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Phone surveillanceis the act of performingsurveillanceon phone conversations,location tracking, and data monitoring of a phone. Before the era ofmobile phones, these used to refer to the tapping of phone lines via a method calledwiretapping. Wiretapping has now been replaced bysoftwarethat monitors the cell phones of users.
While mobile phone surveillance has been carried out by large organizations for a long time (e.g., to find clues of illegal activities), more and more of such surveillance is now carried out by individuals for personal reasons. For example, a parent may become a "text spy" to monitor a child's texting activity. This brings in the moral, ethical and legal question of who owns people'sprivacy.
According to a 2007American Management Associationreport, computer monitoring takes form ranges from keyboard(45%), files(43%), blogosphere(12%) to social networking sites(10%).[1]No newer data is available on the number of phone surveillance carried out currently.
The global phone tracking application market size was valued at around $0.17 billion in 2024 and is expected to grow at aCAGRof around 12.3% until 2032.[2]
Phone surveillance is now more commonly carried out on cell phones. This has become increasingly easy with the availability of cell phone monitoring software. These types of software are easily purchased over theinternetand can be quickly installed on phones. There have been questions as to whether this software is illegal; software makers may show adisclaimerthat they do not endorse any illegal activities.
The law has yet to set a clear boundary on who can or who cannot do phone surveillance. A 2005 federal court ruling denies theFBIfrom tracking cellphone locations of people who have not committed any crimes.[3]
An arm of the U.S. military, the United StatesDefense Intelligence Agency(DIA), has been tracking the location of Americans by searching through databases that it purchases frommobile phonecompanies. The phone companies routinely collect and store their customers' cellular telephone location data when the customers use certain software applications. Additional government agencies that use such tactics to track people and arrest them include theU.S. Immigration and Customs EnforcementandUnited States Customs and Border Protection.[4]
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https://en.wikipedia.org/wiki/Phone_surveillance
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Radio resource location services (LCS) protocol(RRLP) applies toGSMandUMTSCellular Networks. It is used to exchange messages between a handset and anSMLCin order to provide geolocation information;[1]e.g., in the case of emergency calls. The protocol was developed in order to fulfil theWireless Enhanced 911requirements in the United States. However, since the protocol does not require any authentication, and can be used outside of a voice call or SMS transfer, its use is not restricted to emergency calls and can be used by law enforcement to pinpoint the exact geolocation of the target's mobile phone. RRLP was first specified in3GPPTS 04.31 - Location Services (LCS); Mobile Station (MS) - Serving Mobile Location Centre (SMLC); Radio Resource LCS Protocol (RRLP).[2]
Harald Welteproved atHAR2009[3]that many high-end smart-phones submit their GPS location to the mobile operator when requested. This happened without any sort of authentication.
RRLP supports two positioning methods:
The method type indicates whether MS based or assisted location is to be performed.
In this mode, the network typically needs to send so-called assistance data to the phone.
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https://en.wikipedia.org/wiki/Radio_resource_location_services_protocol
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Real-time locating systems(RTLS), also known asreal-time tracking systems, are used to automaticallyidentifyandtrackthe location of objects or people inreal time, usually within a building or other contained area. Wireless RTLS tags are attached to objects or worn by people, and in most RTLS, fixed reference points receive wireless signals from tags to determine their location.[1]Examples of real-time locating systems include tracking automobiles through anassembly line, locating pallets of merchandise in a warehouse, or finding medical equipment in a hospital.
The physical layer of RTLS technology is oftenradio frequency(RF) communication. Some systems use optical (usuallyinfrared) or acoustic (usuallyultrasound) technology with, or in place of RF, RTLS tags. And fixed reference points can betransmitters,receivers, or both resulting in numerous possible technology combinations.
RTLS are a form oflocal positioning systemand do not usually refer toGPSor tomobile phone tracking. Location information usually does not include speed, direction, or spatial orientation.
The term RTLS was created (circa 1998) at theID EXPOtrade show by Tim Harrington (WhereNet), Jay Werb (PinPoint), and Bert Moore (Automatic Identification Manufacturers, Inc., AIM). It was created to describe and differentiate anemerging technologythat not only provided the automatic identification capabilities of activeRFIDtags, but also added the ability to view the location on a computer screen. It was at this show that the first examples of a commercial radio based RTLS system were shown by PinPoint and WhereNet. Although this capability had been utilized previously by military and government agencies, the technology had been too expensive for commercial purposes. In the early 1990s, the first commercial RTLS were installed at three healthcare facilities in the United States and were based on the transmission and decoding ofinfrared lightsignals from actively transmitting tags. Since then, new technology has emerged that also enables RTLS to be applied to passive tag applications.
RTLS are generally used in indoor and/or confined areas, such as buildings, and do not provide global coverage likeGPS. RTLS tags are affixed to mobile items, such as equipment or personnel, to be tracked or managed. RTLS reference points, which can be either transmitters or receivers, are spaced throughout a building (or similar area of interest) to provide the desired tag coverage. In most cases, the more RTLS reference points that are installed, the better the location accuracy, until the technology limitations are reached.
A number of disparate system designs are all referred to as "real-time locating systems". Two primary system design elements are locating at choke points and locating in relative coordinates.
The simplest form ofchoke pointlocating is where short range ID signals from a moving tag are received by a single fixed reader in a sensory network, thus indicating the location coincidence of reader and tag. Alternately, a choke point identifier can be received by the moving tag and then relayed, usually via a second wireless channel, to a location processor. Accuracy is usually defined by the sphere spanned with the reach of the choke point transmitter or receiver. The use of directional antennas, or technologies such as infrared or ultrasound that are blocked by room partitions, can support choke points of various geometries.[2]
ID signals from a tag are received by a multiplicity of readers in asensory network, and a position is estimated using one or more locating algorithms, such astrilateration,multilateration, ortriangulation. Equivalently, ID signals from several RTLS reference points can be received by a tag and relayed back to a location processor. Localization with multiple reference points requires that distances between reference points in the sensory network be known in order to precisely locate a tag, and the determination of distances is calledranging.
Another way to calculate relative location is viamobile tagscommunicating with one another. The tag(s) will then relay this information to a location processor.
RF trilateration uses estimated ranges from multiple receivers to estimate the location of a tag. RF triangulation uses the angles at which the RF signals arrive at multiple receivers to estimate the location of a tag. Many obstructions, such as walls or furniture, can distort the estimated range and angle readings leading to varied qualities of location estimate. Estimation-based locating is often measured in accuracy for a given distance, such as 90% accurate for 10-meter range.
Some systems use locating technologies that can't pass through walls, such as infrared or ultrasound. These require line of sight (or near line of sight) to communicate properly. As a result, they tend to be more accurate in indoor environments.
RTLS can be used in numerouslogisticalor operational areas to:
RTLS may be seen as a threat toprivacywhen used to determine the location of people. The newly declared human right ofinformational self-determinationgives the right to prevent one's identity andpersonal datafrom being disclosed to others and also covers disclosure of locality, though this does not generally apply to theworkplace.
Several prominentlabor unionshave spoken out against the use of RTLS systems to track workers, calling them "the beginning ofBig Brother" and "aninvasion of privacy".[5]
Current location-tracking technologies can be used to pinpoint users of mobile devices in several ways. First, service providers have access to network-based and handset-based technologies that can locate a phone for emergency purposes. Second, historical location can frequently be discerned from service provider records. Thirdly, other devices such as Wi-Fi hotspots or IMSI catchers can be used to track nearby mobile devices in real time. Finally, hybrid positioning systems combine different methods in an attempt to overcome each individual method's shortcomings.[6]
There is a wide variety of systems concepts and designs to provide real-time locating.[7]
A general model for selection of the best solution for a locating problem has been constructed at theRadboud University of Nijmegen.[19]Many of these references do not comply with the definitions given in international standardization with ISO/IEC 19762-5[20]and ISO/IEC 24730-1.[21]However, some aspects of real-time performance are served and aspects of locating are addressed in context of absolute coordinates.
Depending on the physical technology used, at least one and often some combination of ranging and/or angulating methods are used to determine location:
Real-time locating is affected by a variety of errors. Many of the major reasons relate to the physics of the locating system, and may not be reduced by improving the technical equipment.
Many RTLS systems require direct and clear line of sight visibility. For those systems, where there is no visibility from mobile tags to fixed nodes there will be no result or a non valid result fromlocating engine. This applies to satellite locating as well as other RTLS systems such as angle of arrival and time of arrival. Fingerprinting is a way to overcome the visibility issue: If the locations in the tracking area contain distinct measurement fingerprints, line of sight is not necessarily needed. For example, if each location contains a unique combination of signal strength readings from transmitters, the location system will function properly. This is true, for example, with some Wi-Fi based RTLS solutions. However, having distinct signal strength fingerprints in each location typically requires a fairly high saturation of transmitters.
The measured location may appear entirely faulty. This is a generally result of simple operational models to compensate for the plurality of error sources. It proves impossible to serve proper location after ignoring the errors.
Real timeis no registered branding and has no inherent quality. A variety of offers sails under this term. As motion causes location changes, inevitably the latency time to compute a new location may be dominant with regard to motion. Either an RTLS system that requires waiting for new results is not worth the money or the operational concept that asks for faster location updates does not comply with the chosen system's approach.
Location will never be reportedexactly, as the termreal-timeand the termprecisiondirectly contradict in aspects of measurement theory as well as the termprecisionand the termcostcontradict in aspects of economy. That is no exclusion of precision, but the limitations with higher speed are inevitable.
Recognizing a reported location steadily apart from physical presence generally indicates the problem of insufficient over-determination and missing of visibility along at least one link from resident anchors to mobile transponders. Such effect is caused also by insufficient concepts to compensate for calibration needs.
Noise from various sources has an erratic influence on stability of results. The aim to provide a steady appearance increases the latency contradicting to real time requirements.
As objects containing mass have limitations to jump, such effects are mostly beyond physical reality. Jumps of reported location not visible with the object itself generally indicate improper modeling with the location engine. Such effect is caused by changing dominance of various secondary responses.
Location of residing objects gets reported moving, as soon as the measures taken are biased by secondary path reflections with increasing weight over time. Such effect is caused by simple averaging and the effect indicates insufficient discrimination of first echoes.
The basic issues of RTLS are standardized by theInternational Organization for Standardizationand theInternational Electrotechnical Commissionunder the ISO/IEC 24730 series. In this series of standards, the basic standard ISO/IEC 24730-1 identifies the terms describing a form of RTLS used by a set of vendors but does not encompass the full scope of RTLS technology.
Currently several standards are published:
These standards do not stipulate any special method of computing locations, nor the method of measuring locations. This may be defined in specifications for trilateration, triangulation, or any hybrid approaches to trigonometric computing for planar or spherical models of a terrestrial area.
In RTLS application in the healthcare industry, various studies were issued discussing the limitations of the currently adopted RTLS. Currently used technologies RFID, Wi-fi, UWB, all RFID based are hazardous in the sense of interference with sensitive equipment. A study carried out by Dr Erik Jan van Lieshout of the Academic Medical Centre of the University of Amsterdam published inJAMA(Journal of the American Medical Equipment)[24]claimed "RFID and UWB could shut down equipment patients rely on" as "RFID caused interference in 34 of the 123 tests they performed". The first Bluetooth RTLS provider in the medical industry is supporting this in their article: "The fact that RFID cannot be used near sensitive equipment should in itself be a red flag to the medical industry". The RFID Journal responded to this study not negating it rather explaining real-case solution: "The Purdue study showed no effect when ultrahigh-frequency (UHF) systems were kept at a reasonable distance from medical equipment. So placing readers in utility rooms, near elevators and above doors between hospital wings or departments to track assets is not a problem".[25]However the case of ”keeping at a reasonable distance” might be still an open question for the RTLS technology adopters and providers in medical facilities.
In many applications it is very difficult and at the same time important to make a proper choice among various communication technologies (e.g., RFID, WiFi, etc.) which RTLS may include. Wrong design decisions made at early stages can lead to catastrophic results for the system and a significant loss of money for fixing and redesign. To solve this problem a special methodology for RTLS design space exploration was developed. It consists of such steps as modelling, requirements specification, and verification into a single efficient process.[26]
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https://en.wikipedia.org/wiki/Real-time_locating_system
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Riley v. California, 573 U.S. 373 (2014),[1]is alandmarkUnited States Supreme Courtcase in which the court ruled that the warrantlesssearch and seizureof the digital contents of acell phoneduring an arrest is unconstitutional under theFourth Amendment.[2][3]
The case arose from inconsistent rulings on cell phone searches from various state and federal courts. TheFourth,Fifth, andSeventh Circuitshad ruled that police officers can search cell phones incident to arrest under various standards. That rule was also accepted by the Supreme Courts ofGeorgia,Massachusetts, andCalifornia. On the other hand, theFirst Circuitand theSupreme Courts of FloridaandOhiodisagreed and ruled that police needed awarrantto search the information on a suspect's phone.[3]California had also proposed a state statute requiring police to obtain a warrant before searching the contents of "portable electronic devices".[4]
Rileyhas been widely praised as “a sweeping victory for privacy rights”[5]with legal scholars describing the decision as "the privacy gift that keeps on giving."[6]
InChimel v. California(1969), the Supreme Court ruled that if the police arrest someone, they may search the body of the person without awarrantand "the area into which he might reach" in order to protect material evidence or the officers' safety.[7]That ruling served as confirmation of the notion that police may search a suspect, and the area immediately surrounding that person, without awarrantduring a lawful arrest in accordance with thesearch incident to arrestdoctrine.[8]
Before theRileycase, the Supreme Court had explored variations on theChimeltheme, considering police searches of various items individuals had close at hand when arrested, and the court was prepared to look into the seizure ofcell phoneswhen incident to arrest. Lower courts were in dispute on whether theFourth Amendmentallows the police to search the digital contents of such a phone, without first getting a warrant.[9]
David Leon Riley was pulled over in San Diego, California in 2009 for expired registration tags on his vehicle. The officer then found that Riley was driving with a suspended driver's license. TheSan Diego Police Department's policy at the time was to impound a vehicle after stopping a driver with a suspended license in order to prevent them from driving again. Additionally, department policy required officers to perform an inventory search of the vehicle, which in Riley's case led to the discovery of two handguns under the hood of his vehicle.[1]
Later ballistic testing confirmed that the handguns were the weapons used in a gangland murder that had taken place a few weeks previously, for which Riley had been a suspect. Because of the discovery of the concealed and loaded handguns, along with gang paraphernalia, during the vehicle search, police placed Riley under arrest and searched his cell phone without a warrant.[1]
The cell phone search yielded information indicating that Riley was a member of the Lincoln Park gang; evidence included pictures, cell phone contacts, text messages, and video clips. Included in the photos was a picture of a different vehicle that Riley owned, which was also the vehicle involved in the gang shooting. Based in part on the pictures and videos recovered from the cell phone, police charged Riley in connection with the gang shooting.[1]
Riley moved to suppress the cell phone evidence at his criminal trial, but the judge permitted the evidence to be included. Ultimately, Riley was convicted and theCalifornia Court of Appealaffirmed the verdict. That court ruled that thesearch incident to arrestdoctrine permits police to conduct a full exploratory search of a cell phone (even if the search is conducted later and at a different location) whenever the phone is found near the suspect at the time of arrest.[10]Riley then appealed that ruling to the United States Supreme Court.
Brima Wurie was arrested in Boston, Massachusetts in 2007 after police observed him participating in an apparent drug sale. Officers seized two cell phones from Wurie's person, and noticed that one of them was receiving multiple calls from a source identified as “my house” on the phone's screen. The officers opened the phone, accessed its call log, determined the number associated with the “my house” label, and traced that number to what they suspected was Wurie's apartment. They then secured asearch warrantfor Wurie's apartment and, during the ensuing search, found crack cocaine, marijuana, drug paraphernalia, a firearm, ammunition, and cash.[1]
Wurie was subsequently charged with drug and firearm offenses and placed on trial. He moved to suppress the evidence obtained from the search of his apartment, but the trial court denied the motion and Wurie was convicted. Wurie appealed to theFirst Circuit Court of Appeals, which reversed the lower court's decision on the use of phone-related evidence at his trial. The Circuit Court held that cell phones are distinct from other physical possessions that may be searched incident to arrest without a warrant, because of the amount of personal data cell phones contain and the negligible threat they pose to law enforcement interests.[11]Massachusetts prosecutors appealed this ruling to the Supreme Court.
The case ofRiley v. Californiaas heard before the Supreme Court combined two cases: Riley's case andUnited States v. Wurie. Riley argued that the digital contents of a smartphone do not threaten the safety of police officers, and that searches for which officers only have a belief that they may find evidence of a crime still violate constitutional rights.[12]Stanford Universitylaw professorJeffrey L. Fisherargued on behalf of Riley, and claimed that at least six courts held that theFourth Amendmentpermits searches of this type, but that three courts did not. Therefore, a definitive Supreme Court precedent was needed.[13]
Fisher told the justices there are "very, very profound problems with searching a smartphone without a warrant" and that it was like giving "police officers authority to search through the private papers and the drawers and bureaus and cabinets of somebody's house."[14]Fisher warned that it could open up "every American's entire life to the police department, not just at the scene but later at the station house and downloaded into their computer forever".[14]
This consolidated opinion addressed the appeals by both Riley and Wurie due to the similar questions raised. Chief JusticeJohn Robertsdelivered the opinion of the court, concluding that awarrantis required to search a mobile phone.[15]Roberts wrote that when police search a suspect's phone without a warrant, they violate the warrantless search test established inChimel v. California:
Digital data stored on a cell phone cannot itself be used as a weapon to harm an arresting officer or to effectuate the arrestee's escape. Law enforcement officers remain free to examine the physical aspects of a phone to ensure that it will not be used as a weapon--say, to determine whether there is a razor blade hidden between the phone and its case. Once an officer has secured a phone and eliminated any potential physical threats, however, data on the phone can endanger no one.[16]
Although possible evidence stored on a phone may be destroyed with either remote wiping ordata encryption, Roberts emphasized "the ordinary operation of a phone's security features, apart from any active attempt by a defendant or his associates to conceal or destroy evidence upon arrest."[17]He then argued that a warrantless search is unlikely to make much of a difference.[18]Furthermore, Roberts argued that cell phones differ from other objects in a person's pocket:
Modern cell phones are not just another technological convenience. With all they contain and all they may reveal, they hold for many Americans “the privacies of life". The fact that technology now allows an individual to carry such information in his hand does not make the information any less worthy of the protection for which the Founders fought.[19]
JusticeSamuel Alitowrote an opinion concurring in the judgment, noting that "we should not mechanically apply the rule used in the predigital era to the search of a cell phone. Many cell phones now in use are capable of storing and accessing a quantity of information, some highly personal, that no person would ever have had on his person in hard-copy form."[20]
However, in trying to find a balance between law enforcement and privacy issues, Alito expressed concern that the majority opinion would create anomalies: "Under established law, police may seize and examine [hard copies of information] in the wallet without obtaining a warrant, but under the Court's holding today, the information stored in the cell phone is out."[21]Alito further suggested that Congress or state legislatures may need to consider new laws that draw "reasonable distinctions based on categories of information or perhaps other variables",[22]otherwise "it would be very unfortunate if privacy protection in the 21st century were left primarily to the federal courts using the blunt instrument of the Fourth Amendment".[23]
The Supreme Court's ruling inRiley v. Californiawas generally praised for addressing the challenges presented by new technologies,[24]but with mixed reviews concerning its impact on privacy law and police procedure. Some commentators believed that the ruling allowed courts to adapt oldersearch warrantrules for modern behaviors in which people store great amounts of private information on their phones;[25]though others found the ruling to be too narrow and focused only on the types offlip phonesandsmart phonesused during that time period, thus creating an uncertain precedent for future technological developments.[26][27]Therefore, the ruling may be more useful for matters of police procedure rather than privacy.[28]
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https://en.wikipedia.org/wiki/Riley_v._California
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Asatellite navigationorsatnavsystem is a system that usessatellitesto provide autonomousgeopositioning. A satellite navigation system with global coverage is termedglobal navigation satellite system(GNSS). As of 2024[update], four global systems are operational: theUnited States'sGlobal Positioning System(GPS),Russia's Global Navigation Satellite System (GLONASS),China'sBeiDouNavigation Satellite System (BDS),[1]and theEuropean Union'sGalileo.[2]
Satellite-based augmentation systems(SBAS), designed to enhance the accuracy of GNSS,[3]include Japan'sQuasi-Zenith Satellite System(QZSS),[3]India'sGAGANand the EuropeanEGNOS, all of them based on GPS.
Previous iterations of the BeiDou navigation system and the presentIndian Regional Navigation Satellite System(IRNSS), operationally known as NavIC, are examples of stand-alone operatingregional navigation satellite systems(RNSS).[4]
Satellite navigation devicesdetermine their location (longitude,latitude, andaltitude/elevation) to high precision (within a few centimeters to meters) usingtime signalstransmitted along aline of sightbyradiofrom satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to a high precision, which allows time synchronisation. These uses are collectively known asPositioning, Navigation and Timing(PNT). Satnav systems operate independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the positioning information generated.
Global coverage for each system is generally achieved by asatellite constellationof 18–30medium Earth orbit(MEO) satellites spread between severalorbital planes. The actual systems vary, but all useorbital inclinationsof >50° andorbital periodsof roughly twelve hours (at an altitude of about 20,000 kilometres or 12,000 miles).[not verified in body]
GNSS systems that provide enhanced accuracy and integrity monitoring usable for civil navigation are classified as follows:[5]
By their roles in the navigation system, systems can be classified as:
As many of the global GNSS systems (and augmentation systems) use similar frequencies and signals around L1, many "Multi-GNSS" receivers capable of using multiple systems have been produced. While some systems strive to interoperate with GPS as well as possible by providing the same clock, others do not.[8]
Ground-basedradio navigationis decades old. TheDECCA,LORAN,GEEandOmegasystems used terrestriallongwaveradiotransmitterswhich broadcast a radio pulse from a known "master" location, followed by a pulse repeated from a number of "slave" stations. The delay between the reception of the master signal and the slave signals allowed the receiver to deduce the distance to each of the slaves, providing afix.
The first satellite navigation system wasTransit, a system deployed by the US military in the 1960s. Transit's operation was based on theDoppler effect: the satellites travelled on well-known paths and broadcast their signals on a well-knownradio frequency. The received frequency will differ slightly from the broadcast frequency because of the movement of the satellite with respect to the receiver. By monitoring this frequency shift over a short time interval, the receiver can determine its location to one side or the other of the satellite, and several such measurements combined with a precise knowledge of the satellite's orbit can fix a particular position. Satellite orbital position errors are caused by radio-waverefraction, gravity field changes (as the Earth's gravitational field is not uniform), and other phenomena. A team, led by Harold L Jury of Pan Am Aerospace Division in Florida from 1970 to 1973, found solutions and/or corrections for many error sources.[citation needed]Using real-time data and recursive estimation, the systematic and residual errors were narrowed down to accuracy sufficient for navigation.[9]
Part of an orbiting satellite's broadcast includes its precise orbital data. Originally, theUS Naval Observatory (USNO)continuously observed the precise orbits of these satellites. As a satellite's orbit deviated, the USNO sent the updated information to the satellite. Subsequent broadcasts from an updated satellite would contain its most recentephemeris.
Modern systems are more direct. The satellite broadcasts a signal that contains orbital data (from which the position of the satellite can be calculated) and the precise time the signal was transmitted. Orbital data include a roughalmanacfor all satellites to aid in finding them, and a precise ephemeris for this satellite. The orbitalephemerisis transmitted in a data message that is superimposed on a code that serves as a timing reference. The satellite uses anatomic clockto maintain synchronization of all the satellites in the constellation. The receiver compares the time of broadcast encoded in the transmission of three (at sea level) or four (which allows an altitude calculation also) different satellites, measuring the time-of-flight to each satellite. Several such measurements can be made at the same time to different satellites, allowing a continual fix to be generated in real time using an adapted version oftrilateration: seeGNSS positioning calculationfor details.
Each distance measurement, regardless of the system being used, places the receiver on a spherical shell centred on the broadcaster, at the measured distance from the broadcaster. By taking several such measurements and then looking for a point where the shells meet, a fix is generated. However, in the case of fast-moving receivers, the position of the receiver moves as signals are received from several satellites. In addition, the radio signals slow slightly as they pass through the ionosphere, and this slowing varies with the receiver's angle to the satellite, because that angle corresponds to the distance which the signal travels through the ionosphere. The basic computation thus attempts to find the shortest directed line tangent to four oblate spherical shells centred on four satellites. Satellite navigation receivers reduce errors by using combinations of signals from multiple satellites and multiple correlators, and then using techniques such asKalman filteringto combine the noisy, partial, and constantly changing data into a single estimate for position, time, and velocity.
Einstein's theory ofgeneral relativityis applied to GPS time correction, the net result is that time on a GPS satellite clock advances faster than a clock on the ground by about 38 microseconds per day.[10]
The original motivation for satellite navigation was for military applications. Satellite navigation allows precision in the delivery of weapons to targets, greatly increasing their lethality whilst reducing inadvertent casualties from mis-directed weapons. (SeeGuided bomb). Satellite navigation also allows forces to be directed and to locate themselves more easily, reducing thefog of war.
Now a global navigation satellite system, such asGalileo, is used to determine users location and the location of other people or objects at any given moment. The range of application of satellite navigation in the future is enormous, including both the public and private sectors across numerous market segments such as science, transport, agriculture, etc.[11]
The ability to supply satellite navigation signals is also the ability to deny their availability. The operator of a satellite navigation system potentially has the ability to degrade or eliminate satellite navigation services over any territory it desires.
In order of first launch year:
First launch year: 1978
The United States' Global Positioning System (GPS) consists of up to 32medium Earth orbitsatellites in six differentorbital planes. The exact number of satellites varies as older satellites are retired and replaced. Operational since 1978 and globally available since 1994, GPS is the world's most utilized satellite navigation system.
First launch year: 1982
The formerlySoviet, and nowRussian,Global'nayaNavigatsionnayaSputnikovayaSistema, (GLObal NAvigation Satellite System or GLONASS), is a space-based satellite navigation system that provides a civilian radionavigation-satellite service and is also used by the Russian Aerospace Defence Forces. GLONASS has full global coverage since 1995 and with 24 active satellites.
First launch year: 2000
BeiDou started as the now-decommissioned Beidou-1, an Asia-Pacific local network on the geostationary orbits. The second generation of the system BeiDou-2 became operational in China in December 2011.[12]The BeiDou-3 system is proposed to consist of 30MEOsatellites and five geostationary satellites (IGSO). A 16-satellite regional version (covering Asia and Pacific area) was completed by December 2012. Global service was completed by December 2018.[13]On 23 June 2020, the BDS-3 constellation deployment is fully completed after the last satellite was successfully launched at theXichang Satellite Launch Center.[14]
First launch year: 2011
TheEuropean UnionandEuropean Space Agencyagreed in March 2002 to introduce their own alternative to GPS, called theGalileo positioning system. Galileo became operational on 15 December 2016 (global Early Operational Capability, EOC).[15]At an estimated cost of €10 billion,[16]the system of 30MEOsatellites was originally scheduled to be operational in 2010. The original year to become operational was 2014.[17]The first experimental satellite was launched on 28 December 2005.[18]Galileo is expected to be compatible with themodernized GPSsystem. The receivers will be able to combine the signals from both Galileo and GPS satellites to greatly increase the accuracy. The full Galileo constellation consists of 24 active satellites,[19]the last of which was launched in December 2021.[20][21]The main modulation used in Galileo Open Service signal is theComposite Binary Offset Carrier(CBOC) modulation.
TheNavIC(acronym forNavigation with Indian Constellation) is an autonomous regional satellite navigation system developed by theIndian Space Research Organisation(ISRO). TheIndian governmentapproved the project in May 2006. It consists of a constellation of 7 navigational satellites.[22]Three of the satellites are placed ingeostationary orbit (GEO)and the remaining 4 ingeosynchronous orbit (GSO)to have a larger signal footprint and lower number of satellites to map the region. It is intended to provide an all-weather absolute position accuracy of better than 7.6 metres (25 ft) throughoutIndiaand within a region extending approximately 1,500 km (930 mi) around it.[23]An Extended Service Area lies between the primary service area and a rectangle area enclosed by the30th parallel southto the50th parallel northand the30th meridian eastto the130th meridian east, 1,500–6,000 km beyond borders.[24]A goal of complete Indian control has been stated, with thespace segment,ground segmentand user receivers all being built in India.[25]
The constellation was in orbit as of 2018, and the system was available for public use in early 2018.[26]NavIC provides two levels of service, the "standard positioning service", which will be open for civilian use, and a "restricted service" (anencryptedone) for authorized users (including military). There are plans to expand NavIC system by increasing constellation size from 7 to 11.[27]
India plans to make the NavIC global by adding 24 moreMEOsatellites. The Global NavIC will be free to use for the global public.[28]
The first two generations of China's BeiDou navigation system were designed to provide regional coverage.
The Korean Positioning System (KPS) is currently in development and expected to be operational by 2035.[29][30]
GNSS augmentationis a method of improving a navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process, for example, theWide Area Augmentation System, theEuropean Geostationary Navigation Overlay Service, theMulti-functional Satellite Augmentation System,Differential GPS,GPS-aided GEO augmented navigation(GAGAN) andinertial navigation systems.
The Quasi-Zenith Satellite System (QZSS) is a four-satellite regionaltime transfersystem and enhancement forGPScoveringJapanand theAsia-Oceaniaregions. QZSS services were available on a trial basis as of January 12, 2018, and were started in November 2018. The first satellite was launched in September 2010.[31]An independent satellite navigation system (from GPS) with 7 satellites is planned for 2023.[32]
TheEuropean Geostationary Navigation Overlay Service(EGNOS) is asatellite-based augmentation system(SBAS) developed by theEuropean Space AgencyandEurocontrolon behalf of theEuropean Commission. Currently, it supplementsGPSby reporting on the reliability and accuracy of their positioning data and sending out corrections. The system will supplementGalileoin the future version 3.0.
EGNOS consists of 40 Ranging Integrity Monitoring Stations, 2 Mission Control Centres, 6 Navigation Land Earth Stations, the EGNOS Wide Area Network (EWAN), and 3geostationary satellites.[33]Ground stations determine the accuracy of the satellite navigation systems data and transfer it to the geostationary satellites; users may freely obtain this data from those satellites using an EGNOS-enabled receiver, or over the Internet. One main use of the system is inaviation.
According to specifications, horizontal position accuracy when using EGNOS-provided corrections should be better than seven metres. In practice, the horizontal position accuracy is at the metre level.
Similar service is provided in North America by theWide Area Augmentation System(WAAS), in Russia by theSystem for Differential Corrections and Monitoring(SDCM), and in Asia, by Japan'sMulti-functional Satellite Augmentation System(MSAS) and India'sGPS-aided GEO augmented navigation(GAGAN).
27 operational + 3 spares
Currently:
26 in orbit24 operational
2 inactive6 to be launched[36]
Using multiple GNSS systems for user positioning increases the number of visible satellites, improves precise point positioning (PPP) and shortens the average convergence time.[43]The signal-in-space ranging error (SISRE) in November 2019 were 1.6 cm for Galileo, 2.3 cm for GPS, 5.2 cm for GLONASS and 5.5 cm for BeiDou when using real-time corrections for satellite orbits and clocks.[44]The average SISREs of the BDS-3 MEO, IGSO, and GEO satellites were 0.52 m, 0.90 m and 1.15 m, respectively. Compared to the four major global satellite navigation systems consisting of MEO satellites, the SISRE of the BDS-3 MEO satellites was slightly inferior to 0.4 m of Galileo, slightly superior to 0.59 m of GPS, and remarkably superior to 2.33 m of GLONASS. The SISRE of BDS-3 IGSO was 0.90 m, which was on par with the 0.92 m of QZSS IGSO. However, as the BDS-3 GEO satellites were newly launched and not completely functioning in orbit, their average SISRE was marginally worse than the 0.91 m of the QZSS GEO satellites.[3]
Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) is a French precision navigation system. Unlike other GNSS systems, it is based on static emitting stations around the world, the receivers being on satellites, in order to precisely determine their orbital position. The system may be used also for mobile receivers on land with more limited usage and coverage. Used with traditional GNSS systems, it pushes the accuracy of positions to centimetric precision (and to millimetric precision for altimetric application and also allows monitoring very tiny seasonal changes of Earth rotation and deformations), in order to build a much more precise geodesic reference system.[45]
The two current operationallow Earth orbit(LEO)satellite phonenetworks are able to track transceiver units with accuracy of a few kilometres using doppler shift calculations from the satellite. The coordinates are sent back to the transceiver unit where they can be read usingAT commandsor agraphical user interface.[46][47]This can also be used by the gateway to enforce restrictions on geographically bound calling plans.
TheInternational Telecommunication Union(ITU) defines aradionavigation-satellite service(RNSS) as "aradiodetermination-satellite serviceused for the purpose ofradionavigation. This service may also includefeeder linksnecessary for its operation".[48]
RNSS is regarded as asafety-of-life serviceand an essential part ofnavigationwhich must be protected frominterferences.
Aeronautical radionavigation-satellite(ARNSS) is – according toArticle 1.47of theInternational Telecommunication Union's(ITU)Radio Regulations(RR)[49]– defined as «Aradionavigation servicein whichearth stationsare located on board aircraft.»
Maritime radionavigation-satellite service(MRNSS) is – according toArticle 1.45of theInternational Telecommunication Union's(ITU)Radio Regulations(RR)[50]– defined as «Aradionavigation-satellite servicein which earth stations are located on board ships.»
ITU Radio Regulations (article 1) classifiesradiocommunicationservices as:
The allocation of radio frequencies is provided according toArticle 5of the ITU Radio Regulations (edition 2012).[51]
To improve harmonisation in spectrum utilisation, most service allocations are incorporated in national Tables of Frequency Allocations and Utilisations within the responsibility of the appropriate national administration. Allocations are:
Alternative Positioning, Navigation and Timing(AltPNT) refers to the concept of as an alternative to GNSS. Such alternatives include:[52]
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Asecure telephoneis atelephonethat providesvoice securityin the form ofend-to-end encryptionfor the telephone call, and in some cases also the mutual authentication of the call parties, protecting them against aman-in-the-middle attack. Concerns about massive growth oftelephone tappingincidents led to growing demand for secure telephones.
The practical availability of secure telephones is restricted by several factors; notably politics,export issues, incompatibility between different products (the devices on each side of the call have to use the same protocol), and high (though recently decreasing) price of the devices.
The best-known product on the US government market is theSTU-IIIfamily. However, this system has now been replaced by theSecure Terminal Equipment(STE) andSCIPstandards which defines specifications for the design of equipment to secure bothdataand voice. The SCIP standard was developed by theNSAand theUS DODto derive moreinteroperabilitybetween secure communication equipment. A new family of standard secure phones has been developed based on Philip Zimmermann's VoIP encryption standardZRTP.[1]
As the popularity ofVoIPgrows, secure telephony is becoming more widely used. Many major hardware and software providers offer it as a standard feature at no extra cost.
Examples include theGizmo5andTwinkle. Both of the former work with offerings from the founder of PGP,Phil Zimmermann, and his VoIP secure protocol,ZRTP. ZRTP is implemented in, amongst others,Ripcord Networksproduct SecurePC with up to NSA Suite B compliant Elliptic Curve math libraries. ZRTP is also being made available for mobileGSMCSD as a new standard for non-VoIP secure calls.
The U.S.National Security Agencyis developing a secure phone based on Google'sAndroidcalledFishbowl.
Scramblerswere used tosecure voicetraffic duringWorld War II(1939-1945), but were often intercepted and decoded due to scrambling's inherent insecurity. The first true secure telephone (operational from 1943) wasSIGSALY, a massive device that weighed over 50 tons. The NSA, formed in 1952, developed a series of secure telephones, including theSTU Iof the 1970s,STU IIandSTU-III, as well asvoice-encryptiondevices for military telephones.
In 1989 an Irish company called Intrepid developed one of the most advanced secure phones. Called "Milcode",[2]the phone was the first to implementcode-excited linear prediction(or CELP) which dramatically improved voice quality and user-operability over previous LPC (Linear Predictive Coding) and LPC-10e versions.
Milcode also boasted significantly higher levels of security than previous secure telephones. The base model offered a proprietary encryption algorithm with a key-length of 512 bits, and a more advanced model with a key-length of 1024 bits. Key exchange used a public key, based onDiffie-Hellman, as opposed to a plug-in datakey. A new key was generated for each phone call. Milcode was also able to encrypt fax and data and was electromagnetically shielded to NATOTEMPESTstandards.
Other products of historical significance arePGPfoneandNautilus(designed as a non-key escrowalternative toClipper, now officially discontinued, but still available onSourceForge),SpeakFreely, and the security VoIP protocol wrapperZfone(developed byPhil Zimmermann, who wrote thePGPsoftware).
Scrambling, generally using a form ofvoice inversion, was available from suppliers of electronic hobbyist kits and is common onFRSradios. Analog scrambling is still used, as some telecommunications circuits, such as HF links and telephone lines in the developing world, are of very low quality.
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Triggerfishdescribes a technology ofcell phoneinterceptionandsurveillanceusing a mobilecellular base station(microcellorpicocell). The devices are also known as cell-site simulators or digital analyzers.
Neither the user nor the cell phone provider need to know about Triggerfish for it to be used successfully.[2]Acourt orderis required, but the device circumvents provisions ofCALEAbarring use ofpen registerortrap-and-trace devices.[3]
The device is similar to but distinct from anIMSI catcher.[4]
On March 28, 2013, theWashington Postreported that federal investigators "routinely" use the systems to track criminal suspects, but sometimes fail to explain the technology sufficiently tomagistrate judgesfrom whom they seek search warrants.[5]
Thisgovernment-related article is astub. You can help Wikipedia byexpanding it.
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United States v. Jones, 565 U.S. 400 (2012), was alandmarkUnited States Supreme Courtcase in which the court held that installing aGlobal Positioning System(GPS) tracking device on a vehicle and using the device to monitor the vehicle's movements constitutes a search under theFourth Amendment.[1]
In 2004, Antoine Jones was suspected by police in theDistrict of Columbiaofdrug trafficking. Investigators asked for and received awarrantto attach a GPS tracking device to the underside of Jones's car but then exceeded the warrant's scope in both geography and length of time. The Supreme Court ruled unanimously that this was asearchunder the Fourth Amendment, although they were split 5-4 as to the fundamental reasons behind that conclusion. The majority held that by physically installing the GPS device on Jones's car, the police had committed atrespassagainst his "personal effects". This trespass, in an attempt to obtain information, constituted a searchper se.[1]
Antoine Jones owned anightclubin theDistrict of Columbia; Lawrence Maynard managed the club. In 2004, a jointFederal Bureau of Investigation(FBI) andMetropolitan Police Departmenttask force began investigating Jones and Maynard for narcotics violations.[2]During the course of the investigation, police installed aGlobal Positioning System(GPS) device on Jones's wife's Jeep Grand Cherokee.[3]They had received a validwarrantfrom a judge, but that warrant only covered the District of Columbia and only for a limited time period.[4]The GPS device tracked the vehicle's movements 24 hours a day for four weeks, and in the states surrounding the District of Columbia.[5]This exceeded both the time limit and the geographic reach of the original warrant.[4]The FBI arrested Jones under conspiracy to distribute narcotics charges in late 2005, based on data about the locations to which the vehicle was tracked, and he filed a motion toexcludethe GPS data from the evidence collected against him.
Jones was tried in criminal court in late 2006, and a federal jury deadlocked on the conspiracy charge and acquitted him of multiple other counts. The government retried Jones, and in early 2008 the jury returned a guilty verdict on one count of conspiracy to distribute and to possess with intent to distribute five or more kilograms of cocaine and 50 or more grams of cocaine base.[6]He was sentenced to life in prison.[7]
Jones argued that his criminal conviction should be overturned because the use of the GPS tracker violated the Fourth Amendment's protection against unreasonablesearch and seizure.[8]In 2010, theUnited States Court of Appeals for the District of Columbia Circuitagreed with Jones and overturned his conviction, holding that the police action was a search because it violated Jones'sreasonable expectation of privacy.[9][10]The D.C. Circuit then denied prosecutors' petition for rehearingen banc.[11]
The Circuit Court's decision was the subject of significant legal debate.[12][13]In 2007, JudgeRichard Posnerof theUnited States Court of Appeals for the Seventh Circuithad reached the opposite conclusion on whether GPS tracking by police was a search under the Fourth Amendment.[14]
Federal prosecutors appealed the Circuit Court decision. In June 2011, the Supreme Court grantedcertiorarito resolve two questions. The first question was "Whether the warrantless use of a tracking device on respondent's vehicle to monitor its movements on public streets violated the Fourth Amendment." The second question was "Whether the government violated respondent's Fourth Amendment rights by installing the GPS tracking device on his vehicle without a valid warrant and without his consent."[15]
Deputy Solicitor GeneralMichael Dreeben[16]began his argument on behalf of federal prosecutors by noting that information that is visible to anyone in the public, such as a driver's movements on public roads, is not protected by the Fourth Amendment.[17]Dreeben citedUnited States v. Knotts(1983) as an example in which police were allowed to use a device known as a "beeper" that enabled tracking a car from a short distance away.[17]Chief JusticeJohn Robertsdistinguished the present case fromKnotts, saying that using a beeper still took "a lot of work" whereas a GPS device allows the police to "sit back in the station ... and push a button whenever they want to find out where the car is."[18]
JusticeAntonin Scaliathen directed the discussion to whether installing the device was an unreasonable search. Scalia argued that "when that device is installed against the will of the owner of the car on the car, that is unquestionably atrespassand thereby rendering the owner of the car not secure in his effects... against an unreasonable search and seizure."[19]Dreeben argued that it may have been a trespass by police, but in the 1984 precedentUnited States v. Karo(a case involving a similar trespass) the Supreme Court ruled that it "made no difference because the purpose of the Fourth Amendment is to protect privacy interests and meaningful interference [with possessions], not to cover all technical trespasses."[20]
JusticeSamuel Alitostated that people's use of technology is changing what theexpectation of privacyis for the courts. "You know, I don't know what society expects and I think it's changing. Technology is changing people's expectations of privacy. Suppose we look forward 10 years, and maybe 10 years from now 90 percent of the population will be usingsocial networkingsites and they will have on average 500 friends and they will have allowed their friends to monitor their location 24 hours a day, 365 days a year, through the use of theircell phones. Then — what would the expectation of privacy be then?"[21]
JusticeSonia Sotomayornoted that "What motivated the Fourth Amendment historically was the disapproval, the outrage, that our Founding Fathers experienced with general warrants that permitted police indiscriminately to investigate just on the basis of suspicion, notprobable cause, and to invade every possession that the individual had in search of a crime." She then asked, "How is this different?"[22]
On January 23, 2012, the Supreme Court held that "the Government's installation of a GPS device on a target's vehicle, and its use of that device to monitor the vehicle's movements, constitutes a 'search'" under theFourth Amendment.[23][24][25]Some journalists and commentators interpreted this ruling as a requirement that all GPS data surveillance requires a search warrant,[26]but this ruling was narrower and applied only to the circumstances of the police investigation of Jones, particularly regarding location data when driving a vehicle.
It can be said that all nine justices unanimously considered the police's actions inJonesto be unconstitutional. Importantly, however, they were split 5-4 on the reasoning for that conclusion. Furthermore, the justices were of three different opinions with respect to the breadth of the judgment.[27]
JusticeAntonin Scaliaauthored themajority opinion. He cited a line of cases dating as far back as 1886 to argue that a physical intrusion, ortrespass, into a constitutionally-protected area – in an attempt to find something or to obtain information – was the basis, historically, for determining whether a "search" had occurred under the meaning of the Fourth Amendment.[28]Scalia conceded that in the years followingKatz v. United States(1967) – in which electronic eavesdropping on a public telephone booth was held to be a search – the vast majority of search and seizure case law had shifted away from that approach founded on property rights, and towards an approach based on a person'sexpectation of privacy.[29]However, he cited a number of post-Katzcases includingAlderman v. United States[30]andSoldal v. Cook County[31]to argue that the trespass analysis had not been abandoned by the Court.[32]In response to criticisms within Alito's concurrence, Scalia emphasized that the Fourth Amendment must provide, at a minimum, the level of protection as it did when it was adopted. Furthermore, a trespassory test need not exclude a test of the expectation of privacy, which may be appropriate to consider in situations where there was no governmental trespass.[33]
In the present case, the Court concluded that government's installation of aGPSdevice onto the defendant's car (his "personal effects" per Fourth Amendment terminology) was a trespass that was purposed to obtain information, so it was a search under the Fourth Amendment.[1]Having reached the conclusion that this was a search under the Fourth Amendment, the Court declined to examine whether any exception exists that would render the search "reasonable," because the government had failed to advance that theory in the lower courts.[34][35]
Also left unanswered was the broader question surrounding the privacy implications of a warrantless use of GPS datawithouta physical intrusion – as might occur, for example, with the electronic collection of GPS data fromwireless service providersor factory-installedvehicle tracking and navigation services.[27]The Court left these matters to be decided in some future case, saying, "It may be that achieving the same result through electronic means, without an accompanying trespass, is an unconstitutional invasion of privacy, but the present case does not require us to answer that question."[36]
JusticeSonia Sotomayorwas the fifth justice to join Scalia's opinion, making hers the decisive vote; she also wrote a separate concurring opinion.[37]"As the majority's opinion makes clear", she noted, "Katz'sreasonable-expectation-of-privacy test augmented, but did not displace or diminish, thecommon-lawtrespassory test that preceded it".[38]She agreed with Justice Samuel Alito'sexpectation of privacyreasoning with respect to long-term surveillance (see below),[39]but she went a step further by also disputing the constitutionality of warrantless short-term GPS surveillance. Even during short-term monitoring, she reasoned, GPS surveillance can precisely record an individual's every movement, and hence can reveal completely private destinations, like "trips to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on".[39]Sotomayor added:
People disclose the phone numbers that they dial or text to their cellular providers, the URLS that they visit and the e-mail addresses with which they correspond to their Internet service providers, and the books, groceries and medications they purchase to online retailers. [...] I would not assume that all information voluntarily disclosed to some member of the public for a limited purpose is, for that reason alone, disentitled to Fourth Amendment protection.[40]
Sotomayor distinguished the present case fromKnotts, reminding thatKnottssuggested that a different principle might apply to situations in which every a person's movement was completely monitored for 24 hours.[38]
In hisconcurring opinion, JusticeSamuel Alitowrote with respect to privacy: "short-term monitoring of a person's movements on public streets accords with expectations of privacy" but "the use of longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy".[41]Alito argued against the majority's reliance ontrespassunder modern circumstances. Specifically, he argued that thecommon lawproperty-based analysis of a "search" under the Fourth Amendment did not apply to such electronic situations as the one that occurred in this case.[42]He further argued that following the doctrinal changes inKatz, a technical trespass leading to the gathering of evidence was "neither necessary nor sufficient to establish a constitutional violation".[43][44]In his concurring opinion Alito outlined that long-term surveillance can reveal everything about a person:
Prolonged surveillance reveals types of information not revealed by short-term surveillance, such as what a person does repeatedly, what he does not do, and what he does ensemble. These types of information can each reveal more about a person than does any individual trip viewed in isolation. [...] A person who knows all of another's travels can deduce whether he is a weekly church goer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups – and not just one such fact about a person, but all such facts.[45]
Following the privacy-based approach most commonly used post-Katz, the other four justices were instead of the opinion that the continuous monitoring of every single movement of an individual's car for 28 days violated areasonable expectation of privacy, and thus constituted a search. Alito explained that before GPS and similar electronic technology, month-long surveillance of an individual's every move would have been exceptionally demanding and costly, requiring a tremendous amount of resources and people. As a result, society's expectations were, and still are, that such complete and long-term surveillance would not be undertaken, and that an individual would not think it could occur to him or her.[46]
With regard to continuous monitoring for a short period, the other Justices relied on theKnottsprecedent and declined to find a violation of the expectation of privacy.[46]InKnotts, a short-distance signal beeper in the defendant's car was tracked during a single trip for less than a day. TheKnottscourt held that a person traveling on public roads has no expectation of privacy in his movements, because the vehicle's starting point, direction, stops, or final destination could be seen by anyone else on the road.[47]
Walter E. Dellinger III, the former U.S. Solicitor General and the attorney who represented Jones, said the decision was "a signal event in Fourth Amendment history."[3]He also said the decision made it more risky for law enforcement to use a GPS tracking device without a warrant.[48]FBI directorRobert Muellertestified in 2013 that theJonesdecision had limited the Bureau's surveillance capabilities.[49]
Criminal defense attorneys and civil libertarians such as Virginia Sloan of theConstitution Projectpraised the ruling for protecting Fourth Amendment rights against government intrusion through modern technology.[48]TheElectronic Frontier Foundation, which filed anamicus briefarguing that warrantless GPS tracking violates reasonable expectations of privacy, praised Sotomayor's concurrence for raising concerns that existing Fourth Amendment precedents do not reflect the realities of modern technology.[50]
The Supreme Courtremandedthe case to the district court to determine whether Jones's criminal conviction could be restored based on the other evidence collected, and without the GPS data ruled unconstitutional by the Supreme Court. During the original investigation, the police obtainedcell site location datavia a process enabled by theStored Communications Act.[51]JudgeEllen Segal Huvelleruled in late 2012 that the government could use the cell site data against Jones.[52][53]A new criminal trial began in early 2013[54]after Jones rejected aplea bargainof 15 to 22 years in prison.[55]In March 2013, amistrialwas declared with the jury evenly split.[56]The Government planned for a fourth trial[57][58]but in May 2013 Jones accepted a plea bargain of 15 years with credit for time served.[59][60]
In October 2013, theCourt of Appeals for the Third Circuitaddressed the unanswered question of whether warrantless use of GPS devices would be reasonable — and thus lawful — under the Fourth Amendment if police haveprobable causeto justify the search.[61]United States v. Katzinwas the first relevant appeals court ruling in the wake ofJonesto address this topic. The court held that a warrant was indeed required to deploy GPS tracking devices, and further, that none of the narrow exceptions to the Fourth Amendment's warrant requirement (e.g.exigent circumstances) were applicable.[62][63]
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United States v. Karo, 468 U.S. 705 (1984), was aUnited States Supreme Courtdecision related to theFourth Amendmentprotection from unreasonablesearch and seizure. It held that use of an electronic beeper device to monitor a can ofetherwithout awarrantconstituted an unlawful search. However, the Court upheld the conviction of Karo and his accomplices, stating that the warrantaffidavitcontained enough information not derived from the unlawful use of the beeper to provide sufficient basis forprobable cause.[1]
Drug Enforcement Administrationagents installed an electronic beeper in a can of ether with the consent of the owner, a government informant. The marked can was sold along with a shipment of 50 gallons of ether to the respondents, who intended to use the ether for the extraction and production ofcocaine. Having tracked the can of ether as it was moved between various residences and commercial storage lockers, the federal investigators determined the location of the can and obtained an arrest warrant. Respondent Karo and his accomplices were arrested for possession of cocaine with intent to distribute.
Karo's attorneys petitioned to have various portions of the evidencesuppressedbecause they were the "tainted fruit" of an unlawful search. InUnited States v. Knotts,[2]the Court held that the monitoring of a beeper did not violate the Fourth Amendment when it revealed no information that could not have been obtained through visual surveillance.
The Supreme Court held that the use of the beeper to conduct surveillance on Karo and his accomplices constituted an unlawful search and seizure in violation of the Fourth Amendment. However, they determined that since the affidavit which led to the issuance of the arrest warrant contained a significant amount of evidence not obtained through use of the beeper (such as the smell of ether emanating from the storage locker and visual tracking of the cans of ether in automobiles), the arrest warrant was valid. Thus, Karo's conviction was upheld.
The majority stated that the installation of the beeper in the can of ether did not constitute "search" or "seizure" by definition. Rather, the Fourth Amendment was not implicated until the beeper was turned on and used to track the ether shipment on private property.
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Avehicle tracking systemcombines the use ofautomatic vehicle locationin individual vehicles withsoftwarethat collects thesefleetdata for a comprehensive picture of vehicle locations. Modern vehicle tracking systems commonly useGPSorGLONASStechnology for locating the vehicle, but other types of automatic vehicle location technology can also be used. Vehicle information can be viewed onelectronic mapsvia the Internet orspecialized software. Urban public transit authorities are an increasingly common user of vehicletracking systems, particularly in large cities.
Several types of vehicle tracking devices exist. Typically they are classified as "passive" and "active". "Passive" devices store GPS location, speed, heading and sometimes a trigger event such as key on/off, door open/closed. Once the vehicle returns to a predetermined point, the device is removed and the data downloaded to a computer for evaluation. Passive systems include auto download type that transfer data via wireless download. "Active" devices also collect the same information but usually transmit the data in near-real-time viacellularorsatellite networksto a computer or data center for evaluation.
Many modern vehicle tracking devices combine both active and passive tracking abilities: when a cellular network is available and a tracking device is connected it transmits data to a server; when a network is not available the device stores data in internal memory and will transmit stored data to the server later when the network becomes available again.
Historically, vehicle tracking has been accomplished by installing a box into the vehicle, either self-powered with a battery or wired into the vehicle's power system. For detailed vehicle locating and tracking this is still the predominant method; however, many companies are increasingly interested in the emergingcell phonetechnologies that provide tracking of multiple entities, such as both a salesperson and their vehicle. These systems also offer tracking of calls, texts, web use and generally provide a wider range of options.[1]
Major constituents of the GPS-based tracking are:
Vehicle tracking systems are commonly used by fleet operators forfleet managementfunctions such asfleet tracking, routing, dispatching, driving behavior, on-board information and security.[3]Some vehicle tracking systems are bundled with or interface withfleet management software. Along with commercial fleet operators, urbantransitagencies use the technology for a number of purposes, including monitoringschedule adherenceof buses in service, triggering automatic changes of buses'destination signdisplays once the vehicle approaches thebus terminus(or other set location along a bus route such as a particular bus stop along the route), and triggering pre-recorded (or evensynthetic speech) bus stop, route (and its destination) or service announcements for passengers.
TheAmerican Public Transportation Associationestimated that, at the beginning of 2009, around half of all transit buses in the United States were already using a GPS-based vehicle tracking system to trigger automated stop announcements.[4]This can refer to external announcements (triggered by the opening of the bus's door) at a bus stop, announcing the vehicle's route number and destination, primarily for the benefit ofvisually impairedcustomers, or to internal announcements (to passengers already on board) identifying the next stop, as the bus (ortram) approaches a stop, or both; the latter are often also displayed on an internalLED displayorLCD monitorconnected to the system while the loudspeakers play them. Data collected as a transit vehicle follows its route is often continuously fed into a computer program which compares the vehicle's actual location and time with its schedule, and in turn produces a frequently updating display for the driver, telling him/her how early or late he/she is at any given time, potentially making it easier to adhere more closely to the published schedule.
Such programs are also used to provide customers withreal-time informationas to the waiting time until arrival of the next bus or tram/streetcar at a given stop, based on the nearest vehicles' actual progress at the time, rather than merely giving information as to thescheduledtime of the next arrival.[5]Transit systems providing this kind of information assign a unique number to each stop, and waiting passengers can obtain information by entering the stop number into an automated telephone system or an application on the transit system's website.[5][6]
Some transit agencies provide a virtual map on their website, with icons depicting the current locations of buses in service on each route, for customers' information,[7]while others provide such information only to dispatchers or other employees.
Other applications include monitoring driving behavior, such as an employer of an employee, or a parent with a teen driver.
Vehicle tracking systems are also popular in consumer vehicles as atheft prevention, monitoring and retrieval device. Police can simply follow the signal emitted by the tracking system and locate the stolen vehicle. When used as a security system, a Vehicle Tracking System may serve as either an addition to or replacement for a traditionalcar alarm. Some vehicle tracking systems make it possible to control the vehicle remotely, including block doors or engine in case of emergency. The existence of vehicle tracking device then can be used to reduce the insurance cost, because the loss-risk of the vehicle drops significantly.
Vehicle tracking systems are an integrated part of the "layered approach" to vehicle protection, recommended by theNational Insurance Crime Bureau(NICB) to preventmotor vehicle theft. This approach recommends four layers of security based on the risk factors pertaining to a specific vehicle. Vehicle Tracking Systems are one such layer and are described by the NICB as "very effective" in helping police recover stolen vehicles.
Some vehicle tracking systems integrate several security systems, for example by sending an automatic alert to a phone or email if an alarm is triggered or the vehicle is moved without authorization, or when it leaves or enters ageofence.
Other scenarios in which this technology is employed include:
Vehicle tracking systems are widely used worldwide. Components come in various shapes and forms but most useGPS technologyandGSMservices. Newer Vehicle tracking systems also use the latestNB-IoTtechnology that can provide low power consumption and optimized data transmission rates. Additionally, these systems may also feature short range data communication systems such asWiFi. While most will offer real-time tracking, others record real time data and store it to be read, in a fashion similar to data loggers. Systems like these track and record and allow reports after certain points have been solved
Vehicle OBD tracking systems make use of OBD GPS trackers that plug into theonboard diagnostic (OBD)port of light, medium, or heavy-duty vehicle. A cellular OBD GPS tracker directly communicates with the cell tower for sending the location and other vehicle performance data to the server over the cellular wireless network. Usually, the tracker device draws power from the OBD port itself and contains a built-in antenna along with a GPS module for receiving the GPS signal. In addition, OBD trackers communicate with the different vehicle subsystems for receiving vehicle diagnostic and fuel consumption related data. Users can view the information using standalone software or web browser from a desktop/laptop computer or using smartphone apps.
Aside fromtheft-prevention, the most common use of vehicle tracking is in logistics and transport. These systems make use of GPS(Global Positioning System) and GSM(Global System for Mobile Communication) technology to provide precise and constant location telematics to an individual fleet manager. These systems are typically equipped with features to monitor statistics such as; fuel consumption, average speed, current driver time and location. There has been a recent increase in demand for this technology asEU regulationsplace increased restrictions on the hours driver are allowed to work in a given day. It is currently limited to 9 hours per day.[9]Companies are legally obligated to install a tachograph in any vehicle that is expected to carry goods. This obligation has led many to attempt to cauterize this potentially onerous obligation, instead turning it into a benefit. Fleet management systems use GPS & GSM technology. Much like other forms of trackers, although due to their nature they are equipped with more thorough diagnostic features.
Other uses such asTrailer Tracking, Fuel Monitoring, Distance Calculation, Asset Tracking,andField Salescan all be incorporated into a fleet management solution.[10]
Industries not traditionally known to use vehicle tracking systems (logistics and transportation industries are the ones that have traditionally incorporated vehicle tracking system into their operations) have started to use it in creative ways to improve their processes or businesses.
The hospitality industry has caught on to this technology to improve customer service. For example, a luxury hotel in Singapore has installed vehicle tracking systems in their limousines to ensure they can welcome their VIPs when they reach the hotel.
Vehicle tracking systems used in food delivery vans may alert if the temperature of the refrigerated compartment moves outside of the range of safe food storage temperatures.
Car rental companies are also using it to monitor their rental fleets.
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https://en.wikipedia.org/wiki/Vehicle_tracking_system
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Enhanced Messaging Service(EMS) was a cross-industry collaboration betweenmagic4,Ericsson,Motorola,SiemensandAlcatelamong others, which provided an application-level extension toShort Message Service(SMS) forcellular phonesavailable onGSM,TDMAandCDMAnetworks. EMS is defined in3GPPTechnical Specification3GPP TS 23.040 (originally GSM 03.40).[1]
EMS was an intermediate technology, between SMS andMMS, providing some of the features of MMS. EMS was a technology designed to work with existing networks, but was ultimately made obsolete by MMS. An EMS-enabled mobile phone could send and receive messages that had special text formatting (such as bold or italic), animations, pictures, icons, sound effects and specialringtones. EMS messages sent to devices that did not support it would be displayed as SMS messages, though they may be unreadable due to the presence of additional data that cannot be rendered by the device.
In some countries, EMS messages could not generally be sent between subscribers of different mobile phone carriers, as they will frequently be dropped by the inter-carrier network or by the receiving carrier. However, in other countries, such as the UK, inter-carrier interoperability was generally achieved. EMS never really picked up due to interoperability limitations and in fact very few operators ever introduced it.
On June 9, 2008, the CTIA organization officially released an RFI for Enhanced Messaging implementation with focus on Group Messaging.[2]The EM term in this context loosely refers to an improved mobile messaging product that combines the simplicity of Text Messaging with the successful rich features of the Internet'sinstant messaging. Other references to this new service have been made as "SMS 2" or "Instant SMS".
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https://en.wikipedia.org/wiki/Enhanced_Messaging_Service
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Rich Communication Services(RCS) is acommunication protocolstandard forinstant messaging, primarily formobile phones, developed and defined by the GSM Association (GSMA). It aims to be a replacement ofSMSandMMSoncellular networkswith more modern features including high resolution image and video support, typing indicators, file sharing, and improved group chat functionality. Development of RCS began in 2007 but early versions lacked features andinteroperability; a new specification named Universal Profile was developed and has been continually rolled out since 2017.[1]
RCS has been designed as an industryopen standard[2][3]to provide improved capabilities over basictext messaging, based on theInternet Protocol(IP). Its development has also been supported bymobile network operatorsto regain their influence against individual OTT (over-the-top) chat apps and services.[4]Additional features of RCS includepresence information, location and multimedia sharing,video calling, and operation over mobile data orWi-Fi, natively integrated in mobile phones without requiring the download of third-party apps.[5]
As of 2020, RCS has rolled out across 90 cell operators in 60 countries globally,[6]had over 1 billion monthly active users as of 2023,[7]and had an estimated 2.5 billion monthly active users as of 2024.[8]RCS can be used anywhere without carrier support using Google Messages onAndroid, where it is provided via their ownJibebackendin place of a carrier's while still connected to the global RCS network, and additionally was the first to offerend-to-end encryptionover RCS.[9][10]End to end encryption usingMLSwas added to the RCS standard in March 2025, but has not been implemented yet.[11]Appleadded support for RCS inMessageswithiOS 18in September 2024; RCS is also accessible through desktops via the web client of Google Messages[12]or viaMicrosoft Phone Link.[13]
RCS is also marketed asAdvanced Messaging[14]and5G Messaging(in China);[15]it was previously variously marketed aschat features,[16]enhanced chat,[17]joyn,[18]SMSoIP,[citation needed]andSMS+.[19]
Samsung Electronicswas one of the first major deviceoriginal equipment manufacturers(OEMs) to support the RCS initiative and it commercially launched RCS capable devices in Europe in 2012 and in the United States in 2015. Following the launch of the new RCS Universal Profile specification, Samsung supported it on new devices since 2017 in its stock Messages app.[20]In December 2020, Samsung updated itsOne UIMessages app to also allow users to opt into RCS usingGoogle's Jibe backend instead ofcarriersin certain regions.[21]The Samsung Messages client brands the RCS capability aschat features, and displaysEnter chat messagein the message box.[22]Starting in 2024, Samsung Messages is no longer coming preloaded on Galaxy phones sold in the United States market in favor of Google Messages.[23]In January 2025, Samsung Messages was removed from the Google Play Store. The app remains functional for existing users.[24]
Mobile phones runningAndroidwithGoogle Play Servicessupport RCS with its native messaging app,Google Messages, beginning with AndroidLollipop.[25][26]In June 2019, Google announced that it would begin to deploy RCS on an opt-in basis via the Messages app, with service compliant with the Universal Profile and hosted by Google (i.e. Jibe) rather than the user's carrier, if the carrier does not provide RCS.[27][28][29]Before 2023 the Google Messages app branded RCS communication asChat, before it was renamed toRCSto be clearer.[16]In March 2024, it was reported that Google was "silently" blocking RCS onrootedAndroids.[30]
Other flavors of Android such asHuawei'sHarmonyOSin China also support RCS through native messaging clients (EMUIversion 8.1+).[31]
In June 2024,Appleannounced that support for RCS would be added to theMessagesapp iniOS 18; as with SMS, RCS is displayed with green message bubbles and buttons, although an RCS indicator is displayed in the message composer text field.[32]iOS 18 launched with support for RCS in September 2024.[33]
The Rich Communication Suite industry initiative[35]was formed by a group of industry promoters in 2007. In February 2008 theGSM Association (GSMA)officially became the project home of RCS and an RCS steering committee was established by the organization, officially announced as Rich Communications Suite on 15 September 2008,[36]later known as Rich Communication Services.[37]The companies involved in launching it were: operators Orange, Telecom Italia, Telefonica and TeleSonera, network vendors Ericsson and Nokia Siemens Networks, and device vendors Nokia, Sony Ericsson and Samsung.[38]The steering committee specified the definition, testing, and integration of the services in the application suite.[39][40][41]
By 2010, RCS had released Version 4 of its specification, however progress was slow and it had yet to be deployed on commercial subscriber services.[38]During this time, closed internet-basedinstant messagingservices (known in the industry as "OTT" (over-the-top) providers) were rising in popularity.[38]To accelerate development, the RCS project released a new specification – RCS-e (e = "enhanced"), which included various iterations of the original RCS specifications.[38]At Mobile World Congress 2012, RCS-e was launched under the consumer brand name "joyn"[38](a brand that has since been abandoned). The full list of carriers that agreed to support RCS-e at the time wereAT&T,Bell Mobility,Bharti Airtel,Deutsche Telekom,Jio,KPN,KT Corporation,LG U+,Orange,Orascom Telecom,Rogers Communications,SFR,SK Telecom,Telecom Italia,Telefónica,Telia Company,Telus,VerizonandVodafone.[42]That year, the first RCS-e/Joyn services were rolled out by networks in Spain, Germany and the US.[38][43]
However, the RCS standard struggled with fragmentation and incompatibility,[44][45]with one industry analyst stating in 2015 that the project was a "zombie [..] infected with bureaucracy, complexity, and irrelevance".[46]AMountain View-based startup called Jibe Mobile, headed and cofounded by Iranian-American engineer Amir Sarhangi, attempted to solve the situation having built an in-house cloud platform claimed to be fully RCSinteroperablebetween carriers, and offering a fast deployment of the service to the carriers.[47][48]Some operators like Orange and Deutsche Telekom had previously signed up to the Jibe cloud platform.[49]
Googlepurchased Jibe Mobile in September 2015,[50]and Amir Sarhangi led the RCS project at Google. Subsequently they[who?]worked together with the GSMA which led to the creation of the Universal Profile standard.[46]The GSMA published the Universal Profile in November 2016.[51]The Universal Profile is a single GSMA specification, and carriers that deploy the Universal Profile guarantee interconnection with other carriers, while designed to help carriers launch RCS quickly and scale easily.[52][53]
The new standard, helped by promotion from Google, finally led to RCS taking off: in early 2017, there were 47 mobile network operators, 11 manufacturers, and 2 OS providers (Google and Microsoft) that had announced their support of the Universal Profile.[54][44]To accelerate adoption, Google transferred the team that was working onGoogle Alloto work on a wider RCS implementation,[27][28][55]then in 2019 it launched the Guest programme to provide an OTT (over-the-top) RCS solution using Jibe to all GoogleAndroidusers, without requiring carrier support;[56]it rolled out globally by 2020.[57]
In October 2019, the four major U.S. carriers announced an agreement to form the Cross-Carrier Messaging Initiative (CCMI) to jointly implement RCS using a newly developed app. This service was to be compatible with the Universal Profile.[58]However, this carrier-made app never came to fruition. By 2021, bothT-MobileandAT&Tsigned deals with Google to adopt Google's Messages app.[59][60][61]In 2023, T-Mobile and AT&T agreed to use Google Jibe to implement RCS services, and in 2024Verizonagreed to use Google Jibe.[62][63][64]
The three Chinese carriers together announced in April 2020 that they will roll out RCS, branded as5G Messaging.[65]BothChina TelecomandChina Unicomhad rolled out the services within two years time. However,China Mobile, the country's and also world's largest mobile carrier, delayed the roll-out until it began in December 2023.[66]In 2020, Germany's three carriers had all rolled out RCS services, interconnected and provided byMavenir;[67]Mavenir's RCS network also started powering carrierRakuten Mobilein Japan, however this network is not linked to the RCS network used by Japan's three largest carriers, who use their own network named+Messagethat is currently not based on the Universal Profile specifications and not connected to the global RCS network.[68]
In 2023, the Chinese state ruled that all new 5G handsets sold in China from 2024 must support RCS.[69]Media reports stated that this decision led toAppleto announce RCS support on itsiPhone,[70][71]despite Apple CEOTim Cookhaving earlier stated that the company had no plans to support RCS on its devices or any interoperability withiMessage.[72]
SMS(Short Messaging Service) was deployed oncellular networksin the 1990s alongside the earliest2GdigitalGSMnetworks. It uses traditionalcircuit switchingtechnology, as opposed to the data-basedpacket orientedstandards that were introduced with newer technologies likeGPRSand which are now standard.[73]SMS has numerous limitations compared to more modern messaging standards (as ininstant messengerclients), such as a 160 character limit, lack of read receipts, and media sharing (images may be shared but these would be sent as anMMS, with an increased charge). RCS aims to be a modern successor with newer features while still remaining an open standard for cell networks like SMS[73]and hence would also not be a closed "walled garden" like commercial messaging networks (also known as OTT (over-the-top) services) such asMessengerandWhatsApp.[74]
Additionally, RCS isIP-based, instead of theSignalling System No. 7 (SS7)standard that SMS uses. Unlike SMS, RCS may require an Internet connection depending on the RCS servers;[75]this is further explained in theTechnical detailssection below.
RCS Business Messaging (RBM) is thebusiness-to-consumer (B2C)(A2Pin telecoms terminology) version of RCS.[76]RBM includes unique features, including predefined quick-reply suggestions, rich cards, carousels, and branding,[77]designed to improvecustomer engagementand interactive features that facilitate new use cases.[78][79]These are available as standard on preloaded RCS-enabled text messaging apps.
This is supposed to be an answer to third-party messengers (or OTTs) absorbing mobile operators' messaging traffic and associated revenues. While RCS is designed to win back Person-to-Person (P2P) traffic, RBM is intended to retain and grow this A2P traffic.[80][81]These additional features are only available with the use of a messaging-as-a-platform (MaaP) server integrated with the operator's network. SMS currently suffers fromgrey routes, where A2P messages are sent over P2P connections, which are cheaper or often free.[82]
RCS Universal Profile is based on3GPP'sIP Multimedia Subsystem (IMS)architectural framework and usesSession Initiation Protocol (SIP)to establish sessions and exchange messages and other content.[44]
RCS may require an Internet connection depending on the RCS servers: in an IMS 'single registration' setup, the SIP messaging traffic can be forwarded to be sent directly to the carrier's network, instead of going over the top across the Internet in a 'dual registration' scenario.[75]In cases where RCS is able to operate over cellular networks without data, it supports messaging as well as file transfer,enriched calling, and more.[83]
RCS Universal Profile aims to build on SMS with additional interactive features that have become increasingly relevant in world of instant messaging. This includes typing indicators, read receipts, file sharing, high-resolution photo and video sharing, improved group chat functionality,audio messaging, and providing phonebook polling forservice discovery.[83]The service directly links to the user'sphone numberand does not require any account registrations, nor does it require downloading and setting up of third-party chat apps from anapp store.[84]
End-to-end (E2E) encryptionviaMLSis specified by Universal Profile RCS 3.0 as of March 2025, but has not been implemented yet.[11]Previously, E2E encryption was not a feature of RCS specified by GSMA, instead deferring to the individual clients to establish E2E encryption.[85][86][87][88]In September 2024, the GSMA announced it was working on bringing interoperable E2E encryption to the Universal Profile RCS standard.[89]RCS usesTransport Layer Securityencryption when E2E encryption is not available. Google claims it will only retain message data in transit until it is delivered to the recipient over Google infrastructure.[90][91]Google Jibe provides RCS infrastructure for various global carriers, as well as Google Messages directly if the carrier does not offer RCS.
In November 2020, Google announced that it would begin to roll out E2E encryption for one-on-one conversations on theirGoogle Messagesmessaging client - using RCS but not part of the GSMA's RCS specifications - beginning with the beta version of the app.[92]Google added E2E encryption to their Messages app using theSignal Protocolas the default option for one-on-one RCS conversations starting in June 2021.[93][94][85][95]In December 2022, E2E encryption was added to group chats in the Google Messages app for beta users and was made available to all users in August 2023. Additionally, Google enabled RCS in Messages by default to encourage E2E encryption adoption.[87][88][96]
In November 2020, Google stated it would work with any company on RCS E2E encryption compatibility.[85]In July 2023, Google announced it was developing support for theMessaging Layer Security(MLS) E2E encryption standard in Google Messages to encourage interoperability of messaging platforms.[97]In November 2023, Apple stated it will not support Google's E2E encryption extension over RCS, but would work with GSMA to create an RCS E2E encryption standard.[98]In September 2024, the GSMA announced it was working on bringing E2E encryption to the standard.[89]In December 2024, a GSMA spokesperson said the market would be updated with E2E encryption "in the coming months".[99]In March 2025, Apple and Google announced they would support Universal Profile 3.0 with E2E encryption.[100][101]
Mobile network carriers/operatorstypically have two ways to deploy RCS services: either basing it on their own IMS infrastructure, or use a third-party hosted service.[49]Like SMS, RCS requires national and international interconnects to enableroaming. As with SMS, this will be accomplished withhubbing- where third-party providers complete agreements with individual operators to interwork their systems. Each subsequent operator that connects to a hub is therefore connected automatically to all other connected operators. This eliminates the need to each operator to connect to all the others to which they may need to send messages.[102]RCS hubs are provided by stakeholders with a vested interest in increasing RCS use. These include traditional SMS hub providers (e.g.Sinch), and software and hardware vendors (e.g.Mavenir,ZTE, and most notablyGoogle's Jibe Cloud platform).[103]
In 2018,Amnesty Internationalresearcher Joe Westby criticized RCS for not allowingE2E encryption, because it is treated as a service of carriers and thus subject tolawful interception.[104][105]
The Vergein 2019 criticized the inconsistent support of RCS in the United States, with carriers not supporting RCS in all markets, not certifying service on all phones, or not yet supporting the Universal Profile. Concerns were shown over Google's decision to run its own RCS service due to the possibility ofantitrustscrutiny, but it was acknowledged that Google had to do so in order to bypass the carriers' inconsistent support of RCS, as it wanted to have a service more comparable toApple'siMessageservice available onAndroid.[91][106]
Ars Technicain 2019 criticized Google's move to launch a direct-to-consumer RCS service, considering it a contradiction of RCS being native to the carrier to provide features reminiscent ofmessaging apps, counting it as being among various past and unsuccessful attempts by Google to develop an in-house messaging service (includingGoogle Talk,Google+Messenger,Hangouts, andAllo), and noting limitations: such as its dependencies on phone numbers as the identity (whereas email-based accounts aretelco-agnostic), not being capable of being readily synchronized between multiple devices, and the aforementioned lack of E2E encryption.[107]
The GSMA's Universal Profile is a globally agreed-upon standard for implementing RCS. The profile allows subscribers of different carriers and nations to communicate with each other.[108]Universal Profile became the dominant RCS specification since its introduction. Google Jibe worked with the GSMA to create the Universal Profile standard.[46]
Before Universal Profile RCS became the dominant RCS specification, there was a variety of proprietary RCS specifications that did not allow RCS messaging between carriers.[124]RCS combined different services defined by3GPPandOpen Mobile Alliance(OMA) with an enhanced phonebook. Another phone's capabilities and presence information could be discovered and displayed by a mobile phone.
RCS reuses 3GPP specified IMS core system as the underlying service platform to take care of issues such as authentication, authorization, registration, charging and routing.
Release 1 Version 1.0 (15 December 2008)
Release 2 Version 1.0 (31 August 2009)
Release 3 Version 1.0 (25 February 2010)
Release 4 Version 1.0 (14 February 2011)
Release 5 Version 1.0 (19 April 2012)
Release 5.1
Release 5.2 Version 5.0 (7 May 2014)
Release 5.3 Version 6.0 (28 February 2015)
Release 6.0 Version 7.0 (21 March 2016)[125]
RCS-e (enhanced)
An attempt by Europe's five biggest mobile operators to galvanize RCS with a simplified version of RCS.[4]
Joyn
Joyn was a service brand of RCS-e.[4]The GSMA defined a series of specific implementations of the RCS specifications. The RCS specifications often defined a number of options for implementing individual communications features, resulting in challenges in delivering interoperable services between carriers. The RCS specifications aimed to define a more specific implementation that promotes standardization and simplify interconnection between carriers.
Applemaintains a global list of carriers that support Universal Profile RCS messaging inMessages (Apple).[130]These carriers that support RCS Person-to-Person (P2P) do not necessarily support RCS Business Messages, also known as Application-to-Person (A2P).[131]Google Messagessupports RCS with these carriers, and additionally supports RCS for all users globally, provided directly by Google Jibe if the carrier does not offer RCS.[9]TheGSMAstates that Universal Profile support is optional in 4G, but mandatory in 5G networks and devices.[132]
Spain, yes
France, Yes
Spain, Yes[131]
[152]Since July 2018 branded as Chat - Universal profile in Slovakia.
[153]Service in France was interrupted as of 14 November 2017.
Spain, Yes
United Kingdom, No[131]
[140][173][174][175][176]First Branded asjoyn. Since November 2013Message+.
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https://en.wikipedia.org/wiki/Rich_Communication_Services
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OTA Bitmap(Over The Air Bitmap) was a specification designed byNokiafor black and white images for mobile phones.
The OTA Bitmap was defined by Nokia as part of theirSmart Messagingspecification, to send pictures as a series of one or moreconcatenatedSMStext messages. The format has a maximum size of 255x255 pixels. It is very rare for an OTA bitmap to measure anything other than 72x28 pixels (for Picture Messages) or 72x14/72x13 pixels (forOperator Logos). The specification contains a byte of data to be used for indicating a multicolour image. This was to future-proof the standard, but the advent ofMMSmeant it never got to implementation.
The OTA Bitmap format is a monochrome, uncompressed format using one bit per pixel. As the format was designed for cellular phones, there is no standard computer format. It may be stored as abinary fileor as hex (usually without spaces) in a text file. Recognizedextensionis.otb.
Before the image itself there is a header. The header is four bytes wide. A typical example is:00 48 1C 01. These are:
Other possibilities may be:00 48 0E 01(for 72x14 bitmaps),00 48 0D 01(for 72x13 bitmaps).
After the header the image itself starts.
This example will use the following 72x28 pixel image.
The first 8 pixels, reading right from the top left hand corner are one white (0) followed by seven blacks (1111111), giving the firstbyte, inBinary, as 01111111.
Converting from thebinary01111111 tohex, results in the first byte that represents the pixels (7F). The next 8 characters are 8 blacks (11111111 or FF) and so on.
When all pixels from the top row are encoded, simply move to the next. There are no markers to indicate a new row, that information is contained in the header.
In the case of an OTA bitmap that is not a multiple of eight pixels in width, a single byte is used to convey information from two lines (e.g. two pixels from the first row and six from the second.) This is not the case in some other formats, so it is important to exercise care when converting between OTA and formats likeWBMP.
Here is the result of the image converted to OTA.
Note to review: there is no write support for OTA format in XnView
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https://en.wikipedia.org/wiki/OTA_bitmap
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Mobile marketingis a multi-channelonline marketingtechnique focused at reaching a specific audience on theirsmartphones,feature phones,tablets, or any other related devices through websites, e-mail, SMS and MMS, social media, ormobile applications.[1]Mobile marketing can provide customers with time and location sensitive, personalized information that promotes goods, services, appointment reminders and ideas.[2]In a more theoretical manner, academicAndreas Kaplandefines mobile marketing as "any marketing activity conducted through a ubiquitous network to which consumers are constantly connected using a personal mobile device".[3]
Marketing through cellphonesSMS(Short Message Service) became increasingly popular in the early 2000s in Europe and some parts of Asia when businesses started to collect mobile phone numbers and send off wanted (or unwanted) content. On average, SMS messages have a 98% open rate and are read within 3 minutes, making them highly effective at reaching recipients quickly.[4]
Over the past few years, SMS marketing has become a legitimate advertising channel in some parts of the world. This is because, unlike email over the public internet, the carriers who police their own networks have set guidelines and best practices for the mobile media industry (including mobile advertising). The IAB (Interactive Advertising Bureau)has established guidelines and is evangelizing the use of the mobile channel for marketers. While this has been fruitful in developed regions such as North America, Western Europe and some other countries, mobile SPAM messages (SMS sent to mobile subscribers without a legitimate and explicit opt-in by the subscriber) remain an issue in many other parts of the world, partly due to the carriers selling their member databases to third parties. In India, however, the government's efforts to create the National Do Not Call Registry have helped cellphone users stop SMS advertisements by sending a simple SMS or calling 1909.[5]
Mobile marketing approaches through SMS have expanded rapidly in Europe and Asia as a new channel to reach the consumer. SMS initially received negative media coverage in many parts of Europe for being a new form of spam as some advertisers purchased lists and sent unsolicited content to consumer's phones; however, as guidelines are put in place by the mobile operators, SMS has become the most popular branch of the Mobile Marketing industry with several 100 million advertising SMS sent out every month in Europe alone. This is thanks in part to SMS messages being hardware agnostic—they can be delivered to practically anymobile phone,smartphoneorfeature phoneand accessed without aWi-Fior mobile data connection. This is important to note since there were over 5 billion unique mobile phone subscribers worldwide in 2017, which is about 66% of theworld population.[6]
However, nowadays, the mobile phone has become a focal device in people’s lives, and many people cannot live without it. These advanced mobile technologies bring people more business opportunities that connect business people and consumers at any time and place. Because of this, digital marketing has become more essential, and mobile marketing is one of the newest digital marketing channels that people are considering; it can get information about the features of goods that people like without the need for buyers to go to the actual store.[7]
SMS marketing has both inbound andoutbound marketingstrategies. Inbound marketing focuses on lead generation, and outbound marketing focuses on sending messages for sales, promotions, contests, donations, television program voting, appointments and event reminders.
There are 5 key components to SMS marketing:sender ID,message size,content structure,spam compliance, andmessage delivery.
A sender ID is a name or number that identifies who the sender is. For commercial purposes,virtual numbers,short codes, SIM hosting, and custom names are most commonly used and can be leased through bulk SMS providers.
As the name implies, shared virtual numbers are shared by many different senders. They're usually free, but they can't receive SMS replies, and the number changes from time to time without notice or consent. Senders may have different shared virtual numbers on different days, which may make it confusing or untrustworthy for recipients depending on the context. For example, shared virtual numbers may be suitable for 2-factor authentication text messages, as recipients are often expecting these text messages, which are often triggered by actions that the recipients make. But for text messages that the recipient isn't expecting, like a sales promotion, a dedicated virtual number may be preferred.
To avoid sharing numbers with other senders, and for brand recognition and number consistency, leasing a dedicated virtual number, which are also known as a long code orlong number(international number format, e.g. +44 7624 805000 or US number format,[8]e.g. 757 772 8555), is a viable option. Unlike a shared number, it can receive SMS replies. Senders can choose from a list of available dedicated virtual numbers from a bulk SMS provider. Prices for dedicated virtual numbers can vary. Some numbers, often called Gold numbers, are easier to recognize, and therefore more expensive to lease. Senders may also get creative and choose avanity number. These numbers spell out a word or phrase using the keypad, like +1-(123)-ANUMBER.
Shortcodes offer very similar features to a dedicated virtual number but are short mobile numbers that are usually 5-6 digits. Their length and availability are different in each and every country. These are usually more expensive and are commonly used by enterprises and governmental organizations. For mass messaging, shortcodes are preferred over a dedicated virtual number because of their higher throughput and are great for time-sensitive campaigns and emergencies.[9]
In Europe the first cross-carrier SMS shortcode campaign was run by Txtbomb in 2001 for anIsland Recordsrelease, In North America, it was theLabatt Brewing Companyin 2002. Over the past few years, mobileshort codeshave been increasingly popular as a new channel to communicate to the mobile consumer. Brands have begun to treat the mobile shortcode as a mobile domain name, allowing the consumer to text message the brand at an event, in-store and off any traditional media.
Short codes provide a direct line between a brand and their customer base. Once a company has a dedicated short code, they are able to directly message their audience without worrying if the messages are being delivered, unlike long code D.I.D.s (Direct Inward Dial, another term for phone number). Whereas long code texts face a higher level of scrutiny, short codes give you unrivalled throughput without triggering red flags from the carriers.
Physical and virtual SIM hosting allows a mobile number sourced from a carrier to be used for receiving SMS as part of a marketing campaign. The SIM associated with the number is hosted by a bulk SMS provider. With physical SIM hosting, a SIM is physically hosted in a GSM modem and SMS received by the SIM are relayed to the customer. With virtual SIM hosting, the SIM is roamed onto the Bulk SMS provider's partner mobile network and SMS sent to the mobile number are routed from the mobile network's SS7 network to an SMSC or virtual mobile gateway, and then onto the customer.
A custom sender ID, also known as analphanumericsender ID, enables users to set a business name as the sender ID for one-way organization-to-consumer messages. Custom sender IDs are only supported in certain countries and are up to 11 characters long, and support uppercase and lowercaseASCIIletters and digits 0-9.[10]Senders are not allowed to use digits only as this would mimic a shortcode or virtual number that they do not have access to. Reputable bulk SMS providers will check customer sender IDs beforehand to make sure senders are not misusing or abusing them.
The message size will then determine the number of SMS messages that are sent, which then determines the amount of money spent on marketing a product or service. Not all characters in a message are the same size.
A single SMS message has a maximum size of 1120 bits. This is important because there are two types of character encodings, GSM and Unicode. Latin-based languages like English are GSM based encoding, which are 7 bits per character. This is where text messages typically get their 160 characters per SMS limit.[11]Long messages that exceed this limit areconcatenated. They are split into smaller messages, which are recombined by the receiving phone.
Concatenated messages can only fit 153 characters instead of 160. For example, a 177 character message is sent as 2 messages. The first is sent with 153 characters and the second with 24 characters.[12]The process of SMS concatenation can happen up to 4 times for most bulk SMS providers, which allows senders a maximum of 612 character messages per campaign.
Non-Latin based languages, like Chinese, and also emojis use a different encoding process called Unicode or Unicode Transformation Format (UTF-8). It is meant to encompass all characters for efficiency but has a caveat. Each Unicode character is 16 bits in size, which takes more information to send, therefore limiting SMS messages to 70 characters. Messages that are larger than 70 characters are also concatenated. These messages can fit 67 characters and can be concatenated up to 4 times for a maximum of 268 characters.
Special elements that can be placed inside a text message include:
Texting is simple, however, when it comes to SMS marketing - there are many different content structures that can be implemented. Popular message types include sale alerts, reminders, keywords, and multimedia messaging services (MMS).
Sale alerts are the most basic form of SMS marketing. They are generally used for clearance, flash sales, and special promotions. Typical messages include coupon codes, and information like expiration dates, products, and website links for additional information.
Transaction Alerts are used by financial institutions to notify their customer about a financial transaction done from their account. Some SMS only highlights the amount transacted while some also include the balance amount left in the account.
Reminders are commonly used in appointment-based industries or for recurring events. Some senders choose to ask their recipients to respond to the reminder text with an SMS keyword to confirm their appointment. This can really help improve the sender's workflow and reduce missed appointments, leading to improved productivity and revenue.
This allows people to text a custom keyword to a dedicated virtual number or short code. Through custom keywords, users can opt-in to service with minimal effort. Once a keyword is triggered, an autoresponder can be set to guide the user to the next step. They can also activate different functions, which include entering a contest, forwarding to an email or mobile number, group chat, and sending an auto-response.
Keywords also allow users to opt-in to receive further marketing correspondence. When using a long code number you face higher levels of scrutiny from Telecom Companies. When sending SMS messages through long code you are unable to send messages with a link in the first message. This is done at the carrier level to help cut down on spam. Using keyword responses, a company can create a bridge between themselves and the user. Carriers will recognize users responding to an SMS with a keyword as a conversation and will allow links to be delivered.
Similar to email, SMS has anti-spam laws which differ from country to country. As a general rule, it's important to obtain the recipient's permission before sending any text message, especially an SMS marketing type of message. Permission can be obtained in a myriad of ways, including allowing prospects or customers to tick a permission checkbox on a website, filling in a form, or getting a verbal agreement.[13]
In most countries, SMS senders need to identify themselves as their business name inside their initial text message. Identification can be placed in either the sender ID or within the message body copy. Spam prevention laws may also apply to SMS marketing messages, which must include a method to opt out of messages.
One key criterion for provisioning is that the consumer opts in to the service. The mobile operators demand a double opt-in from the consumer and the ability for the consumer to opt-out of the service at any time by sending the word STOP via SMS. These guidelines are established in theCTIAPlaybook and the MMA Consumer Best Practices Guidelines[14]which are followed by all mobile marketers in the United States. InCanada, opt-in became mandatory once theFighting Internet and Wireless Spam Actcame into force in 2014.
Simply put, SMS infrastructure is made up of special servers that talk to each other, using software calledShort Message Service Centre(SMSC) that use a special protocol calledShort Message Peer to Peer(SMPP).
Through the SMPP connections, bulk SMS providers (also known asSMS Gateways) like the ones mentioned above can send text messages and process SMS replies and delivery receipts.
When a user sends messages through a bulk SMS provider, it gets delivered to the recipient's carrier via an ON-NET connection or the InternationalSS7 Network.[15]
Operators around the world are connected by a network known as Signaling System #7. It's used to exchange information related to phone calls, number translations, prepaid billing systems, and is the backbone of SMS. SS7 is what carriers around the world use to talk to each other.
ON-NET routing is the most popular form of messaging globally. It's the most reliable and preferable way for telecommunications/carriers to receive messages, as the messages from the bulk SMS provider is sent to them directly. For senders that need consistency and reliability, seeking a provider that uses ON-NET routing should be the preferred option.
Grey Routingis a term given to messages that are sent to carriers (often offshore) that have low cost interconnect agreements with other carriers. Instead of sending the messages directly to the intended carrier, some bulk SMS providers send it to an offshore carrier, which will relay the message to the intended carrier. At the cost of consistency and reliability, this roundabout way is cheaper, and these routes can disappear without notice and are slower. Many carriers don't like this type of routing, and will often block them with filters set up in their SMSCs.
Some bulk SMS providers have the option to combine more reliable grey routing on lower value carriers with their ON-NET offerings. If the routes are managed well, then messages can be delivered reliably. Hybrid routing is more common for SMS marketing messages, where timeliness and reliable delivery is less of an issue.
The easiest and most efficient way of sending an SMS marketing campaign is through abulk SMSservice provider.Enterprise-gradeSMS providers will usually allow new customers the option to sign-up for a free trial account before committing to their platform. Reputable companies also offer free spam compliance, real-time reporting, link tracking, SMS API,[16]multiple integration options, and a 100% delivery guarantee. Most providers can provide link shorteners and built-in analytics to help track the return on investment of each campaign.
Depending on the service provider and country, each text message can cost up to a few cents each.[17]Senders intending to send a lot of text messages per month or per year may get discounts from service providers.
Since spam laws differ from country to country, SMS service providers are usually location-specific.[18]This is a list of the most popular and reputable SMS companies in each continent, with some information about thenumber of phones in use. It is important to note that message pricing, message delivery, and service offerings will also differ substantially from country to country.
MMS mobile marketing can contain a timed slideshow of images, text, audio and video. This mobile content is delivered viaMMS(Multimedia Message Service). Nearly all new phones produced with a color screen are capable of sending and receiving standard MMS message. Brands are able to both send (mobile terminated) and receive (mobile originated) rich content through MMS A2P (application-to-person) mobile networks to mobile subscribers. In some networks, brands are also able to sponsor messages that are sent P2P (person-to-person).
A typical MMS message based on the GSM encoding can have up to 1500 characters, whereas one based on Unicode can have up to 500 characters.[19]Messages that are longer than the limit are truncated and not concatenated like an SMS.
Good examples of mobile-originated MMS marketing campaigns areMotorola's ongoing campaigns atHouse of Bluesvenues, where the brand allows the consumer to send their mobile photos to the LED board in real-time as well as blog their images online.
Push notifications were first introduced to smartphones byApplewith thePush Notification Servicein 2009.[20]For Android devices, Google developedAndroid Cloud to Messagingor C2DM in 2010. Google replaced this service withGoogle Cloud Messagingin 2013.[21]Commonly referred to as GCM, Google Cloud Messaging served as C2DM's successor, making improvements to authentication and delivery, new API endpoints and messaging parameters, and the removal of limitations on API send-rates and message sizes. It is a message that pops up on a mobile device. It is the delivery of information from a software application to a computing device without any request from the client or the user. They look like SMS notifications but they reach only the users who installed the app. The specifications vary for iOS and Android users. SMS and push notifications can be part of a well-developed inbound mobile marketing strategy.
According to mobile marketing company Leanplum, Android sees open rates nearly twice as high as those on iOS. Android sees open rates of 3.48 percent for push notification, versus iOS which has open rates of 1.77 percent.[22]
With the strong growth in the use of smartphones,appusage has also greatly increased. The annual number of mobile app downloads over the last few years has exponentially grown, with hundreds of billions of downloads in 2018, and the number of downloads expecting to climb by 2022.[23]Therefore, mobile marketers have increasingly taken advantage of smartphone apps as a marketing resource. Marketers aim to optimize the visibility of an app in a store, which will maximize the number of downloads. This practice is calledApp Store Optimization(ASO).
There is a lot of competition[24]in this field as well. However, just like other services, it is not easy anymore to rule the mobile application market.
Most companies have acknowledged the potential of Mobile Apps to increase the interaction between a company and its target customers. With the fast progress and growth of the smartphone market, high-qualityMobile app developmentis essential to obtain a strong position in a mobile app store.
The termapp marketinghas not yet been defined in a unified scientific definition and is also used in various ways in practice. The term refers on the one hand to those activities that serve to generate app downloads and thus attract new users for a mobile app. In some cases, the term is also used to describe the promotional sending ofpush notificationsand in-app messages.[25]
Here are several models for App marketing.
1. Content embedded mode For the most part at present, the downloading APP from APP store is free, for APP development enterprise, need a way to flow to liquidate, implantable advertising and APP combines content marketing and game characters to seamlessly integrating user experience, so as to improve advertising hits.[26]With these free downloading apps, developers use in-app purchases or subscription to profit.[27]
2. Advertising model advertisement implantation mode is a common marketing mode in most APP applications. Through Banner ads, consumer announcements, or in-screen advertising, users will jump to the specified page and display the advertising content when users click. This model is more intuitive, and can attract users' attention quickly.
3. User participation mode is mainly applied to website transplantation and brand APP. The company publishes its own brand APP to the APP store for users to download, so that users can intuitively understand the enterprise or product information better. As a practical tool, this APP brings great convenience to users' life. User reference mode enables users to have a more intimate experience, so that users can understand the product, enhance the brand image of the enterprise, and seize the user's heart.
4. The shopping website embedded mode is the traditional Internet electric business offering platforms in the mobile APP, which is convenient for users to browse commodity information anytime and anywhere, order to purchase and order tracking. This model has promoted the transformation of traditional e-commerce enterprises from shopping to mobile Internet channels, which is a necessary way to use mobile APP for online and offline interactive development, such as Amazon, eBay and so on. The above several patterns for the more popular marketing methods, as for the details while are not mentioned too much, but the hope can help you to APP marketing have a preliminary understanding, and on the road more walk more far in the marketing.[26]
There are essentially three major trends in mobile gaming right now: interactive real-time 3D games, massive multi-player games and social networking games. This means a trend towards more complex and more sophisticated, richer game play. On the other side, there are the so-called casual games, i.e. games that are very simple and very easy to play. Most mobile games today are such casual games and this will probably stay so for quite a while to come.
Brands are now delivering promotional messages withinmobile gamesor sponsoring entire games to drive consumer engagement. This is known as mobile advergaming or ad-funded mobile game.
In in-game mobile marketing, advertisers pay to have their name or products featured in the mobile games. For instance, racing games can feature real cars made by Ford or Chevy. Advertisers have been both creative and aggressive in their attempts to integrate ads organically in the mobile games.
Although investment in mobile marketing strategies like advergaming is slightly more expensive than what is intended for a mobile app, a good strategy can make the brand derive a substantial revenue. Games that use advergaming make the users remember better the brand involved. This memorization increases virality of the content so that the users tend to recommend them to their friends and acquaintances, and share them via social networks.[28]
One form of in-game mobile advertising is what allows players to actually play. As a new and effective form of advertising, it allows consumers to try out the content before they actually install it. This type of marketing can also really attract the attention of users like casual players. These advertising blur the lines between game and advertising, and provide players with a richer experience that allows them to spend their precious time interacting with advertising.
This kind of advertisement is not only interesting, but also brings some benefits to marketers. As this kind of in-gaming mobile marketing can create more effective conversion rates because they are interactive and have faster conversion speeds than general advertising. Moreover, games can also offer a stronger lifetime value. They measure the quality of the consumer in advance to provide some more in-depth experience. So this type of advertising can be more effective in improving user stickiness than advertising channels such as stories and video.[29]
Two-dimensional barcodes that are scanned with a mobile phone camera. They can take a user to the particular advertising webpage a QR code is attached to. QR codes are often used in mobile gamification when they appear as surprises during a mobile app game and directs users to the specific landing page. Such codes are also a bridge between physical medium and online via mobile: businesses print QR codes on promotional posters, brochures, postcards, and other physical advertising materials.
Bluetoothtechnology is a wireless short range digital communication that allows devices to communicate without the now supersededRS-232cables.[30]
Mobile marketing via proximity systems, orproximity marketing, relies on GSM 03.41 which defines the Short Message Service - Cell Broadcast.[citation needed]SMS-CB allows messages (such as advertising or public information) to be broadcast to all mobile users in a specified geographical area. In the Philippines, GSM-based proximity broadcast systems are used by select Government Agencies for information dissemination on Government-run community-based programs to take advantage of its reach and popularity (Philippineshas the world's highest traffic of SMS). It is also used for commercial service known as Proxima SMS. Bluewater, a super-regional shopping center in the UK, has a GSM based system supplied by NTL to help its GSM coverage for calls, it also allows each customer with a mobile phone to be tracked though the center which shops they go into and for how long. The system enables special offer texts to be sent to the phone. For example, a retailer could send a mobile text message to those customers in their database who have opted-in, who happen to be walking in a mall. That message could say "Save 50% in the next 5 minutes only when you purchase from our store." Snacks company,Mondelez International, makers of Cadbury and Oreo products has committed to exploring proximity-based messaging citing significant gains in point-of-purchase influence.[31]
Location-based services(LBS) are offered by some cell phone networks as a way to send custom advertising and other information to cell-phone subscribers based on their current location. The cell-phone service provider gets the location from a GPS chip built into the phone, or using radiolocation and trilateration based on the signal-strength of the closest cell-phone towers (for phones withoutGPSfeatures). In the United Kingdom, which launched location-based services in 2003, networks do not use trilateration; LBS uses a single base station, with a "radius" of inaccuracy, to determine a phone's location.
Some location-based services work withoutGPS trackingtechnique, instead transmitting content between devicespeer-to-peer.
There are various methods for companies to utilize a device's location.[32]
1.Store locators.
Utilizing the location-based feedback, the nearest store location can be found rapidly by retail clients.
2.Proximity-based marketing.
Companies can deliver advertisements merely to individuals in the same geographical location.
Location-based services send advertisements prospective customers of the area who may truly take action on the information.
3.Travel information.
Location-based services can provide actual time information for the smartphones, such as traffic condition and weather forecast, then the customers can make the plan.
4.Roadside assistance.
In the event of sudden traffic accidents, the roadside assistance company can develop an app to track the customer's real-time location without navigation.
The advancement of mobile technologies has allowed the ability to leave a voice mail message on a mobile phone without ringing the line. The technology was pioneered byVoAPP, which used the technology in conjunction with live operators as a debt collection service. The FCC has ruled that the technology is compliant with all regulations.[33]CPLexpanded on the existing technology to allow for a completely automated process including the replacement of live operators with pre recorded messages.
Mobile marketing differs from most other forms of marketing communication in that it is often user (consumer) initiated (mobile originated, or MO) message, and requires the express consent of the consumer to receive future communications. A call delivered from a server (business) to a user (consumer) is called a mobile terminated (MT) message. This infrastructure points to a trend set by mobile marketing of consumer controlled marketing communications.[34]
Due to the demands for more user controlled media, mobile messaging infrastructure providers have responded by developing architectures that offer applications to operators with more freedom for the users, as opposed to the network-controlled media. Along with these advances to user-controlledMobile Messaging 2.0, blog events throughout the world have been implemented in order to launch popularity in the latest advances in mobile technology. In June 2007,Airwide Solutionsbecame the official sponsor for the Mobile Messaging 2.0 blog that provides the opinions of many through the discussion of mobility with freedom.[35]
GPS plays an important role in location-based marketing.[36]
Mobile advertising has become more and more popular. However, some mobile advertising is sent without a required permission from the consumer causing privacy violations. It should be understood that irrespective of how well advertising messages are designed and how many additional possibilities they provide, if consumers do not have confidence that their privacy will be protected, this will hinder their widespread deployment.[37]But if the messages originate from a source where the user is enrolled in a relationship/loyalty program, privacy is not considered violated and even interruptions can generate goodwill.[38]
The privacy issue became even more salient as it was before with the arrival of mobile data networks. A number of important new concerns emerged mainly stemming from the fact that mobile devices are intimately personal[39]and are always with the user, and four major concerns can be identified: mobile spam, personal identification, location information and wireless security.[40]Aggregate presence of mobile phone users could be tracked in a privacy-preserving fashion.[41]
Kaplan categorizes mobile marketing along the degree of consumerknowledgeand the trigger ofcommunicationinto four groups: strangers, groupies, victims, and patrons. Consumer knowledge can be high or low and according to its degree organizations can customize their messages to each individual user, similar to the idea ofone-to-one marketing. Regarding the trigger of communication, Kaplan differentiates between push communication, initiated by the organization, and pull communication, initiated by the consumer. Within the first group (low knowledge/push), organizations broadcast a general message to a large number of mobile users. Given that the organization cannot know which customers have ultimately been reached by the message, this group is referred to as "strangers". Within the second group (low knowledge/pull), customers opt to receive information but do not identify themselves when doing so. The organizations therefore does not know which specific clients it is dealing with exactly, which is why this cohort is called "groupies". In the third group (high knowledge/push) referred to as "victims", organizations know their customers and can send them messages and information without first asking permission. The last group (high knowledge/pull), the "patrons" covers situations where customers actively give permission to be contacted and provide personal information about themselves, which allows for one-to-one communication without running the risk of annoying them.[42]
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Shortcodes, orshort numbers, are short digit-sequences—significantly shorter thantelephone numbers—that are used to address messages in theMultimedia Messaging System(MMS) andshort message service(SMS) systems ofmobile network operators.[1]In addition to messaging, they may be used inabbreviated dialing.
Short codes are designed[citation needed]to be easier to read and remember than telephone numbers.[2]Short codes are unique to each operator at the technological level. Even so, providers generally have agreements to avoid overlaps. In some countries, such as the United States, some classes of numbers are inter-operator (used by multiple providers or carriers). U.S. inter-operator numbers are calledcommon short codes).[3]
Organisations may set up short codes to encourage users to engage with services such ascharity donations, mobile services, orderingringtones, or television-program voting.[2]Messages sent to a short code can be billed at a higher rate than a standard SMS and may even subscribe a customer to a recurring monthly service that will be added to the customer's mobile-phone bill until the user texts, for example, the word "STOP" to terminate the service.[4]
Short codes are often associated with automated services. An automated program can handle the response and typically requires the sender to start the message with a command word or prefix. The service then responds to the command appropriately.
In ads or in other printed material where a provider has to provide both a prefix and the short code number, the advertisement will typically follow this format:
Short Codes are five digits in length and start with 5, also are known as short codes for value added service.
Short codes are six or eight digits in length,[5]starting with the prefix "19" followed by an additional four or six digits.[citation needed]Communications Alliance Ltd and WMC Global are responsible for governing premium and standard rate short codes in Australia. Transactional and Subscription services require a double sms MO opt-in or Web based opt-in with an MO reply.[citation needed]
Codes are five digits in length.Bangladesh Telecommunication Regulatory Commission (BTRC)issues and controls short codes in Bangladesh.
Codes are four digits in length.[6]
Codes are three digits in length.
Codes are five digits in length.[7]
Short Codes are four digits in length and start with 1.
Canadian Common Short Codes can be five or six digits long. Common Short Codes beginning with a leading '4' are reserved for private use by wireless network operators. Four-digit Common Short Codes are not permitted due to handset incompatibilities. Short code-based messages vary betweenzero-rated(paid for by campaign),standard rate(user is responsible for standard carrier charges), andpremium rate(varies,C$1-10). Canadian Short codes are governed by the Canadian Wireless Telecommunications Association.[8]
In February 2020, CWTA (Canadian Wireless Telecommunications Association) announced that Rogers Wireless will no longer participate in general use mobile codes in the future. A common short code is a code that is shared by more than one brand for multiple or general uses.[9]
Codes are three and four digits in length.
Messages sent to/from these short codes are known as Premium Rate SMS. Codes are seven digits in length for MO and five (not billed) or eight (billed) for MT direction, starting with nine, while two or three (depending on billing type=MO/MT) trailing digits express the price, e.g. SMS sent to 9090930 is billed forKč30. Leading three digits are purpose type prefixes (908 for micro payments, 909 for adult content and 900 for everything else), digits at position four and five determines the service provider registered by a network operator. There are also other four digit shortcodes, used by a network operators for service only purposes (operator dependent)
Codes are three or four digits in length.
Codes are four or five digits in length.
Codes are four digits in length and start with 8, like 8xxx. Although the telecom sector in Ethiopia is controlled by the government, short code services are outsourced to the private sector. The short codes are used mostly for fundraising, lottery and polling.
Common EU-wide codes start with 11. Examples include: 118xxx - directory services,[10]116xxx - emergency helplines. This is in addition to the EU-wide emergency number 112.
Codes are four digits in length, beginning with "12" or "19".[11]
Codes are five or more digits in length, usually five or six.
Codes are five digits in length. Starting digits define the cost of the service.
Codes are four or five digits in length.
Codes are five digits in length.
Codes are four to eight digits in length, start with digits 501-509.[12]Emergency number is 992.[13]
Codes are four or five digits in length.
There are many companies in the Indian market who rent keywords, on a monthly basis, whose characters, on a typicaltelephone keypad, represent short codes. Short codes are five digits in length and have to start with the digit '5'. The five digits can be extended by three digits further representing three additional characters. Texts sent to these Short Codes are commonly referred to as Premium Rate SMS Messages and cost aroundRs1 to Rs 3 per text depending on the operator as well as the service. Any length of full message can be sent, ranging from 100–500 (some providers only support).
Codes are four digits in length withRp2000 premium price.
Short codes are five digits in length, and start with 5. The second digit generally indicates the maximum price, with 0 = completely free, 1 = standard text rate only, 3 =€0.60, and 7 having no maximum. Codes beginning 59 are ostensibly intended for adult services, but few if any of these codes are used.[14]
In Italy, short codes have no fixed length, starting from three digits up to five. All short codes that start with the digit "4", are designated by a local telecommunications law for "network services". Widely known short codes are in the 48xxx range, commercial ringtones and mobile stuff download.
Codes are generally four to six digits in length, however short codes have no fixed length.
In Latvia short codes also have no fixed length, starting from three digits up to five. All 4 digit short codes that start with "118" or 5 digit short codes that start with "1184" are designated to information service providers.
In Lithuania, short codes also have no fixed length, starting from three digits up to five. All short codes that start with the digit "1", are designated by a local telecommunications law for "network services".
Codes are five digits in length, start with "2" or "3", premium pricing fromRM0.30 up to 10.00. Codes are MT billed so subscription services are allowed. Upon service description approval by mobile operators, dedicated codes are generally live in 4 weeks, and shared codes after 1 week.
Codes are four digits in length.
Codes are three to four digits in length. Dialing short codes are generally 3 digits, and reserved for public services. SMS shortcodes are used for a range of purposes, and are four digits.
Codes are four digits in length.[citation needed]
Codes are three to four digits in length.
Codes are four to five digits in length.
Codes are four to five digits in length.
Codes are three and four digits in length. Users are charged PKR 5 - PKR 25 per SMS sent on short codes. Mobile operators charge a setup fee, monthly fee and fee per keyword for short codes. Short codes usage must abide by the rules set by PTA (Pakistan Telecom Authority).
Codes are four digits in length.
Commercial codes are five digit long (1xxxx) and are reachable from both mobile and fixed networks. Calls to short codes - from any type of network - are routed based on the location of the number originating the call; hence, if wishing to reach a particular geographical area, the subscriber might need to prefix the short code with an appropriate area code.
Codes are seven digits in length. The National Telecommunications Commission (NTC) is a regulatory agency providing an environment that ensures reliable, affordable and viable infrastructure and services in information and communications technology (ICT) accessible to all.[15]Although the NTC is ultimately responsible for the governance of premium and non-premium shortcodes in the Philippines, the NTC's regulatory guidelines are not comprehensive when applied to shortcodes. Instead NTC's guidelines focus more on the carriers and the carrier's technical infrastructure. NTC's website does not contain any specific information with regard to premium SMS or standard rate SMS. There is relevant documentation for Bulk SMS and SPAM control via NTC's "AMENDMENT TO THE RULES AND REGULATIONS ON BROADCAST MESSAGING SERVICES", however again is not directly related to premium SMS.
Codes are four digits in length. The cost of the call or SMS to the short number varies from 1.2 to 300rubles, depending on the number and the carrier.
Codes are four digits in length.
Codes are five digits in length.
Codes are five digits in length. Short codes will start with either a "3" or "4". For example, 34001 or 42001. Each short code or short code range (a range will generally be 34000 to 34009) are assigned specific tariffs or end user prices (EUP). The tariff charges can range fromR0.50 to R30.00 on mobile originated billing and from R0.50 to R50.00 using mobile terminated billing.[16][17]Due to high costs associated with short code rental many providers offer shared shortcodes, which greatly reduces costs.[18]
Codes are four digits in length.
Codes are five digits in length.
Codes are three to five digits in length (most popular codes are three digits long); codes starting with "6" are reserved for adult services.
Codes are usually four digits in length, starting with digits "19".
Codes are four digits in length.
Codes are usually five, six or seven digits in length, mostly starting with 6, 7 or 8.[19]The range of codes may be expanded in time to use other leading digits such as 4. Shortcodes are often owned by holding companies[20]who then lease them out to service providers and advertisers to promote SMS services, charitable fundraising and marketing promotions such as news alerts, voting and quizzes.
Codes starting 70 are used by charities.[21]Codes starting 72 are used by Society Lotteries.[21]Adult related mobile services must use codes starting 69 or 89. Mobile operators sometimes use proprietary codes (either with a different leading digit, or shorter in length) for operator-specific functions. Depending on the service offered, users may interact with service providers either by calling the number, or by sending and/or receiving a text or MMS message.
Calls to mobile shortcodes may be free, or may be charged per call or at a per minute rate. Where the number can be called from any mobile network, the same charge will apply from all networks.
Messages sent to mobile shortcodes may be charged at a "standard rate", or with an additional premium charge. Where messages incur a "standard rate" charge, this is set by the sender's mobile provider and varies by provider.
Messages received from shortcodes may be free or may incur a premium charge. Messages can be used to deliver additional content, or a URL link that opens the users web browser at a specific web page. For subscription services, the charges may recur on a daily, weekly, monthly or other basis. To stop a subscription based shortcode service text the word 'STOP' to the shortcode number.
The service provider must state the applicable charges alongside the number. Calls and messages to mobile shortcodes do not count towards inclusive allowances or bundles.
Where the benefit passed on to the service provider is more than 10p per call, per minute, or per message, Ofcom'sPremium Rate Services Condition[22][23]defines it as being aControlled Premium Rate Service(CPRS) and subject to the additional regulation detailed inThe Regulation of Premium Rate Services Order 2024.[24]
Until 31 January 2025, these services were regulated by thePhone-paid Services Authority.[25]From 1 February 2025, Ofcom regulates these services directly.[26][27]A number of key PSA staff had already been embedded within Ofcom for some time in preparation for this move.[28]
Standard, interoperable short codes in the U.S. are five or six digits long,[29]never start with 1, and only work in the U.S.[30]They are leased by the short code program's registry service providericonectiv, under a deal with theCommon Short Code Administration[31]andCTIA.[32]It costs twice as much to choose a specific code as it does to get one that is randomly assigned.[32]Some carriers assign a subset of their carrier-specific codes to third parties.[33]
"TheShort Code Registry[34]maintains a single database of available, reserved and registered short codes. CTIA administers the Common Short Code program, andiconectiv[35]became the official U.S. Short Code Registry service provider in January, 2016. For more information, please see theShort Code Registry’s Best Practices[36]and theShort Code Monitoring Handbook."[37][38][39]
Texting "HELP" to a short code causes the short code service to return a message with terms and conditions, support information — consisting of either a toll-free phone number or email address at a minimum — and other information from the leaseholder of the short code.[40][41]A user can opt-out from receiving any further messages from a short code service by texting "STOP", "END", "QUIT", "CANCEL", or "UNSUBSCRIBE" to the short code; after doing so, one final message confirming the opt-out is sent.[42][37]
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Synchronized Multimedia Integration Language(SMIL(/smaɪl/)) is aWorld Wide Web ConsortiumrecommendedExtensible Markup Language(XML)markup languageto describemultimediapresentations. It defines markup for timing, layout, animations, visual transitions, and media embedding, among other things. SMIL allows presenting media items such as text, images, video, audio, links to other SMIL presentations, and files from multiple web servers. SMIL markup is written in XML, and has similarities toHTML.
Members of theWorld Wide Web Consortium(also known as the "W3C") created SMIL forstreaming mediapresentations, and published SMIL 1.0 in June 1998. Many of these W3C members helped author several versions of SMIL specifications between 1996 (when the first multimedia workshops were hosted by the W3C) and 2008 (when SMIL 3.0 was published). SMIL is an XML-based application, and is a part of manyMultimedia Messaging Service(MMS) applications. SMIL can be combined with other XML-based specifications such as with SVG (as has been done withSVG animation) and with XHTML (as done withHTML+TIME).
As of 2008[update], theW3C Recommendationfor SMIL isSMIL 3.0.
SMIL 1.0 became a W3C Recommendation on 15 June 1998.[2][6]
SMIL 2.0became a W3C Recommendation on 9 August 2001.[7]SMIL 2.0 introduced a modular language structure that facilitated integration of SMIL semantics into other XML-based languages. Basic animation and timing modules were integrated into Scalable Vector Graphics (SVG) and the SMIL modules formed a basis forTimed-Text. The modular structure made it possible to define the standard SMIL language profile and theXHTML+SMILlanguage profile with common syntax and standard semantics.
SMIL 2.1became a W3C Recommendation on 13 December 2005.[4][8]SMIL 2.1 includes a small number of extensions based on practical experience gathered using SMIL in theMultimedia Messaging Systemon mobile phones.
SMIL 3.0became a W3C Recommendation in December 2008.[5]It was first submitted as a W3C Working draft on December 21, 2006.[9]The last draft revision was released on October 6, 2008.[10][11]
Authoring and rendering tools for smilText and SMIL 3.0 PanZoom functionality:
Demos
A SMIL document is similar in structure to anHTMLdocument in that they are typically divided between an optional<head>section and a required<body>section. The<head>section contains layout and metadata information. The<body>section contains the timing information, and is generally composed of combinations of three main tags—sequential ("<seq>", simple playlists), parallel ("<par>", multi-zone/multi-layer playback) and exclusive ("<excl>", event-triggered interrupts). SMIL refers to media objects byURLs, allowing them to be shared between presentations and stored on different servers forload balancing. The language can also associate different media objects with differentbandwidthrequirements.
For playback scheduling, SMIL supportsISO-8601wallclock()date/time specification to define begin/end events for playlists.
SMIL files take either a.smior.smilfile extension. However,SAMIfiles and Macintoshself mounting imagesalso use.smi, which creates some ambiguity at first glance. As a result, SMIL files commonly use the.smilfile extension to avoid confusion.
SMIL was created during a time when structured data using XML was very popular and during a time whenInternet Explorerwas very popular. Thus "combining" SMIL with other markup languages was considered one of thebest current practicesof the day.
SMIL is one of three means by whichSVG animationcan be achieved (the others beingJavaScriptandCSS animations).
WhileRSSandAtomareweb syndicationmethods, with the former being more popular as a syndication method forpodcasts, SMIL is potentially useful as a script orplaylistthat can tie sequential pieces of multimedia together and can then be syndicated through RSS or Atom.[12][13]In addition, the combination of multimedia-laden .smil files with RSS or Atom syndication would be useful for accessibility to audio-enabled podcasts by thedeafthrough Timed Text closed captions,[14]and can also turn multimedia into hypermedia that can be hyperlinked to other linkable audio and video multimedia.[15]
VoiceXMLcan be combined with SMIL to provide a sequential reading of several pre-provided pages or slides in avoice browser, while combining SMIL withMusicXMLwould allow for the creation of infinitely-recombinable sequences of music sheets. Combining SMIL+VoiceXML or SMIL+MusicXML with RSS or Atom could be useful in the creation of an audible pseudo-podcast with embedded hyperlinks, while combining SMIL+SVG with VoiceXML and/or MusicXML would be useful in the creation of an automatically audio-enabledvector graphicsanimationwith embedded hyperlinks.
SMIL is anticipated for use withinText Encoding Initiative(TEI) documents.[16][17]
SMIL is being implemented on handheld and mobile devices and has also spawned[18]theMultimedia Messaging Service(MMS) which is a video and picture equivalent ofShort Message Service(SMS).
SMIL is also one of the underlying technologies used for "Advanced Content" in the (discontinued)HD DVDformat for adding interactive content (menus etc.).
The field ofDigital Signageis embracing SMIL as a means of controlling dynamic advertising in public areas.[19][20]
Most commonly usedweb browsershave native support for SMIL, but it has not been implemented in Microsoft browsers. It was to be deprecated in Google Chrome,[21]but it has now been decided to suspend that intent until alternatives are sufficiently developed.[22]Other software that implement SMIL playback include:
Media player boxes based on dedicated 1080p decoder chips such as the Sigma Designs 8634 processor are getting SMIL players embedded in them.
A SMIL file must be embedded, then opened using a plug-in such as Apple's QuickTime or Microsoft's Windows Media Player, to be viewed by a browser that doesn't support SMIL.
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The domain namemobiis ageneric top-level domain(gTLD) in theDomain Name System(DNS) of theInternet. The name is short formobile.
The domain was approved byICANNon 11 July 2005, and is managed by the mTLD global registry. It was originally financially backed and sponsored byGoogle,Microsoft,Nokia,Samsung,Ericsson,Vodafone,T-Mobile,Telefónica Móviles,Telecom Italia Mobile,Orascom Telecom,GSM Association,Hutchison Whampoa,Syniverse Technologies, andVisa, with an executive from each company serving on mTLD's board of directors.[1]In February 2010,Afiliasacquired mTLD Top-Level Domain Ltd. (known publicly as "dotMobi").[2]In March 2017, .mobi became an unsponsored generic top-level domain, using the same terms offered tonew gTLDs.[3]
DotMobi domain names have been available for registration by the public since 26 September 2006.
dotMobi engaged with theW3CMobile Web Initiative (MWI) to help formulate the MWI Best Practices for mobile content. The practices outlined a number of ways to achieve good user experiences on mobile Web-enabled devices, and recognized several methods of implementing these practices.
mTLD has released a free testing tool called Ready.mobi (latermobiForge) to analyze the mobile readiness of websites. It does a free page analysis and gives a .mobi Ready score from 1 to 5. This report tests the mobile-readiness of the site using dotMobi's recommended best practices.
dotMobi does not itself mandate any particular technology, but does recommends that .mobi sites produce user experiences consistent with their guidelines and specifically optimized for mobile phones.
By 2024, the old authoritativeWHOISdomain for .mobi had been allowed to expire, which created a vulnerability that included allowing for the creation of fraudulentdigital certificates.[4]
"mobiForge" is amobile developmentanddesignresource site run dotMobi. mobiForge functions both as a platform to announce product updates to thedevelopercommunity anddiscussion forumsfor each of dotMobi's products and services. mobiForge was launched in November 2006 as dev.mobi. It was announced at theMobile 2.0Conference inSan Francisco, along with the launch of ready.mobi. dev.mobi underwent a majorredesignin September 2008 and was rebranded as mobiForge and moved to mobiForge.com
Originally dotMobi focused on promoting the creation of two separate device-dependentWorld Wide Webs, one desktop-based and the other mobile-based. Because of this,Tim-Berners Leebrought up concerns of excess Internet content redundancy.[5]
Providing content tailored to particular devices can be done by other means than a specific TLD, such as using hostnames within an existing domain,HTTPcontent negotiation,cascading style sheets, or other forms of adaptation. The popularization ofresponsive web designhas caused the domain name to be relocated for use on mobile services andmobile appswebsites.
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https://en.wikipedia.org/wiki/.mobi
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NTT DoCoMo'si-mode(Japanese:iモード,ai-mōdo) is amobile internet(distinct fromwireless internet) service popular inJapan. UnlikeWireless Application Protocols, i-mode encompasses a wider variety of internet standards, including web access,e-mail, and thepacket-switched networkthat delivers the data. i-mode users also have access to other various services such as: sports results,weather forecasts,games, financial services, and ticket booking. Content is provided by specialised services, typically from themobile carrier, which allows them to have tighter control over billing.
Like WAP, i-mode delivers only those services that are specifically converted for the service, or are converted through gateways.
In contrast with theWireless Application Protocol(WAP) standard, which usedWireless Markup Language(WML) on top of a protocol stack for wireless handheld devices, i-mode borrows from DoCoMo proprietary protocols ALP (HTTP) and TLP (TCP,UDP), as well as fixed Internet data formats such as C-HTML, a subset of theHTMLlanguage designed by DoCoMo.[1]C-HTML was designed for small devices (e.g. cellular phones) with hardware restrictions such as lower memory, low-power CPUs with limited or no storage capabilities, small monochrome display screens, single-character fonts and limited input methods.[2]As a simpler form of HTML, C-HTML does not support tables, image maps, multiple fonts and styling of fonts, background colors and images, frames, or style sheets, and is limited to a monochromatic display.[3]
i-mode phones have a special i-mode button for the user to access the start menu. There are more than 12,000 official sites and around 100,000 or more unofficial i-mode sites, which are not linked to DoCoMo's i-mode portal page and DoCoMo's billing services. NTT DoCoMo supervises the content and operations of all official i-mode sites, most of which are commercial. These official sites are accessed through DoCoMo's i-mode menu but in many cases official sites can also be accessed from mobile phones by typing the URL or through the use ofQR code(abarcode).
An i-mode user pays for both sent and received data. There are services to avoidunsolicited e-mails. The basic monthly charge is typically on the order ofJPY¥200–300 for i-mode not including the data transfer charges, with additional charges on a monthly subscription basis for premium services. A variety of discount plans exist, for example family discount and flat packet plans for unlimited transfer of data at a fixed monthly charge (on the order of ¥4,000 per month).
i-mode was launched in Japan on 22 February 1999. The content planning and service design team was led byMari Matsunaga, while Takeshi Natsuno was responsible for the business development. Top executive Keiichi Enoki oversaw the technical and overall development. A few months after DoCoMo launched i-mode in February 1999, DoCoMo's competitors launched very similar mobile data services:KDDIlaunchedEZweb, andJ-PhonelaunchedJ-Sky. Vodafone later acquired J-Phone including J-Sky, renaming the serviceVodafone live!, although initially this was different from Vodafone live! in Europe and other markets. In addition, Vodafone KK was acquired bySoftBank, an operator of Yahoo! Japan in October, 2006 and changed the name toSoftBank Mobile.
BandaiandNamcolaunched content for i-mode in 1999. Bandai launched theDokodemo Aso Vegasservice in May 1999, reaching over1 millionpaid subscribers by March 2000. In December 1999, Namco launchedNamco Station, a mobile site for i-mode.[4]
Since 2003, i-mode center is called CiRCUS, which consists of 400NECNX7000HP-UXservers and occupies 4,600 m2floor space in DoCoMo'sKawasakioffice. The operation support system is called CARNiVAL, which is hosted in theSanno Park Tower.
As of June 2006, the mobile data services I-Mode, EZweb, and J-Sky, had over 80 million subscribers in Japan.
i-mode usage in Japan peaked around 2008. On 29 October 2019, DoCoMo announced i-mode will end on 31 March 2026.[5]
Seeing the tremendous success of i-mode in Japan, many operators in Europe, Asia and Australia sought to license the service through partnership with DoCoMo. Takeshi Natsuno was behind the expansion of i-mode to 17 countries worldwide. Kamel Maamria who was a partner with the Boston Consulting Group and who was supporting Mr. Natsuno is also thought to have had a major role in the expansion of the first Japanese service ever outside Japan.
i-mode showed very fast take-up in the various countries where it was launched which led to more operators seeking to launch i-mode in their markets with the footprint reaching a total of 17 markets worldwide.
While the i-mode service was an exceptional service which positioned DoCoMo as the global leader in value add services, another key success factor for i-mode was the Japanese smartphone makers who developed state of the art handsets to support i-mode. As i-mode was exported to the rest of the world, Nokia and other major handset vendors who controlled the markets at the time, refused at first to support i-mode by developing handsets which support the i-mode service. The operators who decided to launch i-mode had to rely on Japanese vendors who had no experience in international markets. As i-mode showed success in these markets, some vendors started customizing some of their handsets to support i-mode, however, the support was only partial and came late in time.
While the service was successful during the first years after launch, the lack of adequate handsets and the emergence of new handsets from new vendors which supported new Internet services on one hand, and a change of leadership of i-mode in Docomo, lead to a number of operators to migrate or integrate i-mode into new mobile Internet services. These efforts were ultimately unsuccessful, and i-mode never became popular outside of Japan.[6]
i-mode sponsored theRenault F1 teamfrom 2004 to 2006.
i-mode was launched in the following countries:
Some typical features include the "clamshell" model with large displays (240 x 320 pixels) and in many models, a display on either side. Additionally the phones have many extra features, e.g. a megapixeldigital camera. The displays normally have 65,536 colors but the newest models have as many as 262,144 colors.
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Amobile browseris aweb browserdesigned for use on amobile devicesuch as amobile phone,PDA,smartphone, ortablet. Mobile browsers are optimized to display web content most effectively on small screens on portable devices. Some mobile browsers, especially older versions, are designed to be small and efficient to accommodate the low memory capacity and low bandwidth of certain wireless handheld devices. Traditional smallerfeature phonesuse stripped-down mobile web browsers; however, most current smartphones have full-fledged browsers that can handle the latest web technologies, such asCSS 3,JavaScript, andAjax.
Websites designed to be usable in mobile browsers may be collectively referred to as themobile web. Today, over 75% of websites are "mobile friendly",[citation needed]by detecting when a request comes from a mobile device and automatically creating a "mobile" version of the page, designed to fit the device's screen and be usable with a touch interface.
The mobile browser usually connects via thecellular network, or increasingly viaWireless LAN, using standardHTTPoverTCP/IPand displays web pages written inHTML. Historically, early feature phones were restricted to only displaying pages specifically designed for mobile use, written inXHTML Mobile Profile(WAP 2.0), orWML(which evolved fromHDML). WML and HDML are stripped-down formats suitable for transmission across limited bandwidth, and wireless data connection calledWAP. In Japan, DoCoMo defined thei-modeservice based on i-mode HTML, which is an extension of Compact HTML (C-HTML), a simple subset of HTML.
WAP 2.0 specifies XHTML Mobile Profile plus WAP CSS, subsets of the W3C's standard XHTML and CSS with minor mobile extensions.
Smartphone mobile browsers are full-featured Web browsers capable of HTML,CSS,ECMAScript, as well as mobile technologies such as WML, i-mode HTML, or cHTML.
To accommodate small screens, they usePost-WIMPinterfaces.
The first mobile browser for a PDA was PocketWeb[1][2]for theApple Newtoncreated atTecOin 1994, followed by the first commercial product NetHopper released in August 1996.[3]
The so-called "microbrowser" technologies such as WAP, NTTDocomo's i-mode platform andOpenwave's HDML platform fueled the first wave of interest in wireless data services.
The first deployment of a mobile browser on a mobile phone was probably in 1997 when Unwired Planet (later to become Openwave) put their "UP.Browser" onAT&Thandsets to give users access to HDML content.[4][5]
A British company,STNCLtd., developed a mobile browser (HitchHiker) in 1997 that was intended to present the entire device UI. The demonstration platform for this mobile browser (Webwalker) had 1MIPStotal processing power. This was a single core platform, running the GSM stack on the same processor as the application stack. In 1999 STNC was acquired byMicrosoft[6]and HitchHiker became Microsoft Mobile Explorer 2.0,[7]not related to the primitive Microsoft Mobile Explorer 1.0. HitchHiker is believed to be the first mobile browser with a unified rendering model, handling HTML and WAP along with ECMAScript,WMLScript,POP3andIMAPmail in a single client. Although it was not used, it was possible to combine HTML and WAP in the same pages although this would render the pages invalid for any other device. Mobile Explorer 2.0 was available on the Benefon Q, Sony CMD-Z5, CMD-J5, CMD-MZ5, CMD-J6, CMD-Z7, CMD-J7 and CMD-J70. With the addition of a messaging kernel and a driver model, this was powerful enough to be the operating system for certain embedded devices. One such device was the Amstrade-m@iler[8]and e-m@iler 2. This code formed the basis for MME3.
Multiple companies offered browsers for the Palm OS platform. The first HTML browser for Palm OS 1.0 was HandWeb by Smartcode software, released in 1997. HandWeb included its own TCP/IP stack, and Smartcode was acquired byPalmin 1999. Mobile browsers for the Palm OS platform multiplied after the release of Palm OS 2.0, which included a TCP/IP stack. A freeware (although later shareware) browser for the Palm OS was Palmscape, written in 1998 by Kazuho Oku in Japan, who went on to foundIlinx. It was still in limited use as late as 2003.Qualcommalso developed the Eudora Web browser, and launched it with the Palm OS based QCP smartphone. ProxiWeb[9]was a proxy-based Web browsing solution, developed byIan Goldbergand others[10]at the University of California, Berkeley and later acquired by PumaTech.
Released in 2001, Mobile Explorer 3.0 added iMode compatibility (cHTML) plus numerous proprietary schemes.[11]By imaginatively combining these proprietary schemes with WAP protocols, MME3.0 implemented OTA database synchronisation,push email, push information clients (not unlike a 'Today Screen') and PIM functionality. The cancelled Sony Ericsson CMD-Z700 was to feature heavy integration with MME3.0. Although Mobile Explorer was ahead of its time in the mobile phone space, development was stopped in 2002.
Also in 2002, Palm, Inc. offered Web Pro on Tungsten PDAs based upon aNovarrabrowser. PalmSource offered a competing Web browser based onAccessNetFront.
Opera softwarepioneered with itsSmall Screen Renderingand Medium Screen Rendering technology. TheOperaweb browser is able to reformat regular web pages for optimal fit on small screens and medium-sized (PDA) screens. It was also the first widely available mobile browser to supportAjaxand the first mobile browser to pass theAcid2test.
Distinct from a mobile browser is a web-based emulator, which uses a "Virtual Handset" to display WAP pages on a computer screen, implemented either in Java or as an HTML transcoder.
The following are some of the more popular mobile browsers. Some mobile browsers are really miniaturized web browsers, so some mobile device providers also provide browsers fordesktopandlaptopcomputers.
Palm
Mobile transcoders reformat and compress web content for mobile devices and must be used in conjunction with built-in or user-installed mobile browsers. The following are several leading mobiletranscodingservices.
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Mobile app developmentis the act or process by which amobile appisdevelopedfor one or moremobile devices, which can includepersonal digital assistants(PDA),enterprise digital assistants(EDA), ormobile phones.[1]Such software applications are specifically designed to run on mobile devices, after considering many hardware constraints. Common constraints includecentral processing unit(CPU) architecture and speeds, availablerandom-access memory(RAM), limited data storage capacities, and considerable variation in displays (technology, size, dimensions, resolution) and input methods (buttons, keyboards, touch screens with or without styluses).[2]These applications (or 'apps') can bepre-installedon phones during manufacturing or delivered as web applications, using server-side or client-side processing (e.g.,JavaScript) to provide an "application-like" experience within aweb browser.[3]
The mobile app development sector has experienced significant growth in Europe. A 2017 report from the Progressive Policy Institute estimated there were1.89 million jobsin theapp economyacross theEuropean Union(EU) by January 2017, marking a 15% increase from the previous year. These jobs include roles such as mobile app developers and other positions supporting the app economy.[4]
To facilitate developing applications for mobile devices, and the consistency thereof, various approaches have been taken.
Most companies that ship a product (e.g., Apple, iPod/iPhone/iPad) provide an officialsoftware development kit(SDK). They may also opt to provide some form ofsoftware testingand/orquality assurance(QA). In exchange for being provided the SDK or other tools, it may be necessary for a prospective developer to sign some form of non-disclosure agreement (NDA), which restricts the sharing of privileged information.
As part of the development process, mobileuser interface(UI) design is an essential step in the creation of mobile apps. Mobile UI designers consider constraints, contexts, screen space, input methods, and mobility as outlines for design. Constraints in mobile UI design, which include the limited attention span of the user and form factors such as a mobile device's screen size for a user's hand(s). Mobile UI context includes signal cues from user activity, such as the location where or the time when the device is in use, that can be observed from user interactions within a mobile app. Such context clues can be used to provide automatic suggestions when scheduling an appointment or activity or to filter a list of various services for the user.
The user is often the focus of interaction with their device, and the interface entails components of both hardware and software. User input allows for the users to manipulate a system, and the device's output allows the system to indicate the effects of the users' manipulation.
Overall, mobile UI design's goal is mainly for an understandable, user-friendly interface. Functionality is supported bymobile enterprise application platformsorintegrated development environments(IDEs).
Developers of mobile applications must also consider a large array of devices with different screen sizes, hardware specifications, and configurations because of intense competition in mobile hardware and changes within each of the platforms.
Today, mobile apps are usually distributed via an official online outlet or marketplace (e.g., Apple: The App Store – Google: Google Play) and there is a formalized process by which developers submit their apps for approval and inclusion in those marketplaces. Historically, however, that was not always the case.
Mobile UIs, or front-ends, rely on mobile back-ends to support access to enterprise systems. The mobile back-end facilitates data routing, security, authentication, authorization, working off-line, and service orchestration. This functionality is supported by a mix ofmiddlewarecomponents, including mobile app servers, mobile backend as a service (MBaaS), andservice-oriented architecture(SOA) infrastructure.
The software development packages needed to develop, deploy, and managemobile appsare made from many components and tools which allow a developer to write, test, and deploy applications for one or more target platforms.
Front-end development tools are focused on the user interface and user experience (UI-UX) and provide the following abilities:
Notable tools are listed below.
First party tools include officialSDKspublished by, or on behalf of, the company responsible for the design of a given hardware platform (e.g., Apple, Google, etc.), and any third-party software that is officially supported for the purpose of developing mobile apps for that hardware.
Kotlin
Back-end tools pick up where the front-end tools leave off, and provide a set of reusable services that are centrally managed and controlled and provide the following abilities:
Available tools include:
XML
Withbring your own device(BYOD) becoming the norm within more enterprises, IT departments often need stop-gap, tactical solutions that layer atop existing apps, phones, and platform component. Features include
Many system-level components are needed to have a functioning platform for developing mobile apps.
Criteria for selecting a development platform usually include the target mobile platforms, existing infrastructure, and development skills. When targeting more than one platform with cross-platform development, it is also important to consider the impact of the tool on theuser experience. Performance is another important criterion, as research on mobile apps indicates a strong correlation between application performance and user satisfaction. Along with performance and other criteria, the availability of the technology and the project's requirements may drive the development between native and cross-platform environments. To aid the choice between native and cross-platform environments, some guidelines and benchmarks have been published. Typically, cross-platform environments are reusable across multiple platforms, leveraging a native container while using HTML, CSS, and JavaScript for the user interface. In contrast, native environments are targeted at one platform for each of those environments. For example, Android development occurs in the Eclipse IDE using Android Developer Tools (ADT) plugins, Apple iOS development occurs using the Xcode IDE with Objective-C and/or Swift, Windows and BlackBerry each have their own development environments.
Mobile applications are first tested within the development environment using emulators and later subjected tofield testing.Emulatorsprovide an inexpensive way to test applications on mobile phones to which developers may not have physical access. The following are examples of tools used for testing applications across the most popularmobile operating systems.
Tools include
According to a 2020 Industry Report on Applications, 46% ofmobile appusers have stated that they have stopped using or uninstalled an app due to poor performance.[9]Design experts advocate for the following design principles to create successful and effective mobile apps:
Clutter-free screens– Keeps interactions quick and simple, allowing users to focus on one specific task rather than being overwhelmed with multiple features and tasks. Design experts strongly advocate for one task per screen and recommend breaking down long forms into pages and progressively revealing new tasks or fields to minimize clutter.[10]
Reduce cognitive load– Makes the use of the app as seamless as possible, and preserves natural flow through the app. Design experts suggest incorporatingautocomplete,spell-check,predictive textassistance, anddropdown menusto reduce cognitive load. Design experts also recommend the state of the app be preserved when users temporarily leave the app and re-enter so that users can continue their use from where they left off.[10][11]
Simple navigation– Around 11% of people have uninstalled apps due to their complicatedinterface.[9]Design experts state it is paramount to present the navigation bar visibly in your app to help users navigate to frequently used and high-priority screens instantly. They suggest the use of recognizable icons specific to the device operating system to help users easily take actions such as opening a menu, changing settings, going back a screen, and searching within a page. According to them, a user should not be confused while navigating the app, so an orderly, clear, and logical navigation flow drives engagement and discovery in the app.[10][11]
Notifications– It’s reported that around 19% of users uninstall an app due to frequent push notifications.[9]Notifications should be sent with careful planning according to design experts. Experts state notifications should be sent at a time most convenient to users in their time zone and the messages should be personalized to bring great value to them.[10]
Speed appearance– About 19% of people uninstall apps due to hang up issues.[9]Design experts state it’s important to make sure the app is fast and responsive so that users don’t have to wait for content. They state developers should deliver content faster or give the perception of progress. Some approaches suggested by the experts are the use of skeleton screens which show the layout of the app with content grayed out,progress barsor loading spinners, tasks being carried out in the background and delivering the content quickly when the user requests for it, or giving users some tasks or content while they are waiting for a page to load.[10]
Usability– Approximately 85% of mobile users use their phone with one hand,[9]thus design experts state it is important that the top-level menu, frequently used controls, and common action items are within the reach of the user’s thumb. They also stress the importance of readability and it’s recommended that the text size is at least 11 point font so that users can read it at the typical reading distance without zooming in.[10]It is recommended that headers and titles on the app screens beSan Francisco17pt andRoboto16sp for operating systemsiOSandAndroidrespectively.[11]The experts also state there should be 4.5:1 minimumcontrast ratiobetween text and the background color.[10]Design experts strongly encourage developers to make apps accessible for all users including people withdisabilities, so they suggest features such asvoice navigation,screen readercompatibility, and user interface adaptability in mobile apps.[11]
Many patent applications are pending for new mobile phone apps. Most of these are in the technological fields of business methods, database management, data transfer, and operator interface.[12]
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Themobile webcomprises mobile browser-basedWorld Wide Webservices accessed from handheldmobile devices, such assmartphonesorfeature phones, through amobileor otherwireless network.
Traditionally, theWorld Wide Webhas been accessed viafixed-lineservices on laptops and desktop computers. However, the web is now more accessible by portable and wireless devices. Early 2010ITU(International Telecommunication Union) report said that with current growth rates, web access by people on the go – via laptops and smart mobile devices – was likely to exceed web access from desktop computers within the following five years.[1]In January 2014, mobile internet use exceeded desktop use in the United States.[2]The shift to mobile Web access has accelerated since 2007 with the rise of largermultitouchsmartphones, and since 2010 with the rise of multitouchtablet computers.Both platforms provide better Internet access, screens, andmobile browsers, or application-based user Web experiences than previous generations of mobile devices.Web designersmay work separately on such pages, or pages may be automatically converted, as inMobile Wikipedia. Faster speeds, smaller, feature-rich devices, and a multitude of applications continue to drive explosive growth for mobile internet traffic. The 2017 Virtual Network Index (VNI) report produced by Cisco Systems forecasts that by 2021, there will be 5.5 billion global mobile users (up from 4.9 billion in 2016).[3]Additionally, the same 2017 VNI report forecasts that average access speeds will increase by roughly three times from 6.8 Mbit/s to 20 Mbit/s in that same period with video comprising the bulk of the traffic (78%).
According to BuzzCity, the mobile internet increased by 30% from Q1 to Q2 2011.[4]In July 2012, approximately 10.5% of all web traffic occurred through mobile devices (up from 4% in December 2010).[5]
The distinction betweenmobile web applicationsandnative applicationsis anticipated to become increasingly blurred, asmobile browsersgain direct access to the hardware of mobile devices (includingaccelerometersandGPSchips), and the speed and abilities of browser-based applications improve.Persistent storageand access to sophisticateduser interfacegraphics functions may further reduce the need for thedevelopmentofplatform-specificnativeapplications.
The mobile web has also been called Web 3.0, drawing parallels to the changes users were experiencing asWeb 2.0websites proliferated.[6][7][8]
The mobile web was first popularized by the Silicon Valley company, Unwired Planet.[9][failed verification]In 1997, Unwired Planet, Nokia, Ericsson, and Motorola started theWAP Forumto create and harmonize the standards to ease the transition to bandwidth networks and small display devices. The WAP standard was built on a three-layer, middleware architecture that fueled the early growth of the mobile web. It was made virtually irrelevant after the development and adoption of faster networks, larger displays, and advanced smartphones based on Apple's iOS and Google's Android software.
Mobile Internet refers to Internet access and mainly usage ofInternetusing a cellular telephone service provider or mobile wireless network. This wireless access can easily change to use a different wireless Internet (radio) tower as a mobile device user moves across the service area. Cellular base stations that connect through the telephone system are more expensive to provide compared to a wireless base station that connects directly to the network of an internet service provider. A mobile broadband modem may "tethers" the smartphone to one or more devices to provide access to theInternetviathe protocolsthat cellular telephone service providers offer.
The Mobile Web Initiative (MWI) was set up by theW3Cto develop the best practices and technologies relevant to the mobile web. The goal of the initiative is to make browsing the web from mobile devices more reliable and accessible. The main aim is to evolve standards of data formats from Internet providers that are tailored to the specifications of particular mobile devices. The W3C has published guidelines formobile content, and aimed to address the problem of device diversity by establishing a technology to support a repository of device descriptions.
W3C developed a validating scheme to assess the readiness of content for the mobile web, through itsmobileOK Scheme, which aims to help content developers to determine if their content is web-ready.[10]The W3C guidelines and mobileOK approach have faced criticism.[citation needed]mTLD, the registry for.mobi, released a free testing tool called the MobiReady Report (seemobiForge) to analyze the mobile readiness of website.
Access to the mobile web was first commercially offered in 1996, in Finland, on theNokia 9000 Communicatorphone via theSoneraandRadiolinjanetworks. The first commercial launch of a mobile-specific browser-based web service was in 1999 in Japan wheni-modewas launched byNTT DoCoMo.
The mobile web primarily utilizes lightweight pages like this one written inExtensible Hypertext Markup Language(XHTML) orWireless Markup Language(WML) to deliver content to mobile devices. Many newmobile browsersare moving beyond these limits by supporting a wider range of Web formats, including variants of HTML commonly found on the desktop web.
At one time, half the world had mobile phones.[11]The articles in 2007-2008 were slightly misleading because the real story at the time was that the number of mobile phone subscriptions had reached half the population of the world. In reality, many people have more than one subscription. For example, inHong Kong,ItalyandUkraine, the mobile phone penetration rate had passed 140% by 2009 . In 2009, the number of unique users of mobile phones had reached half the population of the planet when the ITU reported thatthe subscriber number was to reach 4.6 billion users which means 3.8 billion activated mobile phones in use, and 3.4 billion unique users of mobile phones.[clarification needed]Mobile Internet data connections are following the growth of mobile phone connections, albeit at a lower rate. In 2009 Yankee Group reported that 29% of all mobile phone users globally were accessing browser-based internet content on their phones. According to the BBC, in 2020 there were over 5 billion mobile phone users in the world.[12]According to Statista there were 1.57 billion smartphone owners in 2014 and 2.32 billion in 2017.[13]
Many users inEuropeand theUnited Statesare already users of the fixedinternetwhen they first try the same experience on a mobile phone. Meanwhile, in other parts of the world, such asIndia, their first usage of the internet is on a mobile phone. Growth is fastest in parts of the world where thepersonal computer(PC) is not the first user experience of the internet. India,South Africa,Indonesia, andSaudi Arabiaare seeing the fastest growth in mobile internet usage.[as of?]To a great extent, this is due to the rapid adoption of mobile phones themselves. For example, Morgan Stanley reports that the highest mobile phone adoption growth in 2006 was inPakistanand India. Mobile internet has also been adopted in West Africa,[14]and China had 155 million mobile internet users as of June 2009.[15][irrelevant citation]
The.mobisponsored top-level domainwas launched specifically for the mobile Internet by a consortium of companies including Google, Microsoft, Nokia, Samsung, and Vodafone. By forcing sites to comply with mobile web standards, .mobi tries to ensure visitors a consistent and optimized experience on their mobile device. However, this domain has been criticized by several big names, includingTim Berners-Leeof theW3C, who said that providing different content to different devices "breaks the Web in a fundamental way".[16]
In the fall of 2015,Googleannounced it would be rolling out anopen sourceinitiative called "Accelerated Mobile Pages" or AMP. The goal of this project is to improve the speed and performance of content-rich pages which includevideo,animations, andgraphics. Since the majority of the population now consumes the web through tablets andsmartphones, having web pages that are optimized for these products is the primary need to AMP.[17][18]
The three main types of AMP are AMPHTML, AMPJS, and Google AMPCache.[19]
As of February 2018, Google requires the canonical page content to match the content on accelerated mobile pages.[citation needed]
Mobile web access may suffer frominteroperabilityandusabilityproblems. Interoperability issues stem from theplatformfragmentation of mobile devices,mobile operating systems, and browsers. Usability problems are centered on the small physical size of themobile phone form factors, which limitdisplay resolutionanduser input). Limitations vary, depending on the device, and newersmartphonesovercome some of these restrictions, but problems which may be encountered include:
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Wireless transaction protocol(WTP) is a standard used inmobile telephony. It is a layer of the Wireless Application Protocol (WAP)[1]that is intended to bringInternetaccess tomobile phones. WTP provides functions similar toTCP, except that WTP has reduced amount of information needed for each transaction (e.g. does not include a provision for rearranging out-of-order packets).[1]WTP runs on top of UDP and performs many of the same tasks as TCP but in a way optimized for wireless devices,[1]which saves processing and memory cost as compared to TCP.
It supports 3 types of transaction:[2]
This article aboutwireless technologyis astub. You can help Wikipedia byexpanding it.
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https://en.wikipedia.org/wiki/Wireless_transaction_protocol
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WURFL(WirelessUniversalResourceFiLe) is a set of proprietaryapplication programming interfaces(APIs) and anXMLconfiguration filewhich contains information about device capabilities and features for a variety of mobile devices, focused on mobile device detection.[1][2]Until version 2.2, WURFL was released under an "open source / public domain" license.[3]Prior to version 2.2, device information was contributed by developers around the world and the WURFL was updated frequently, reflecting new wireless devices coming on the market. In June 2011, the founder of the WURFL project,Luca Passani, and Steve Kamerman, the author of Tera-WURFL, a popular PHP WURFL API, formed ScientiaMobile, Inc to provide commercial mobile device detection support and services using WURFL.[4]As of August 30, 2011, the ScientiaMobile WURFL APIs are licensed under adual-licensemodel, using theAGPLlicense for non-commercial use and a proprietary commercial license. The current version of the WURFL database itself is no longer open source.
There have been several approaches to this problem, including developing very primitive content and hoping it works on a variety of devices, limiting support to a small subset of devices or bypassing the browser solution altogether and developing aJava MEorBREWclient application.
WURFL solves this by allowing development of content pages using abstractions of page elements (buttons, links and textboxes for example). At run time, these are converted to the appropriate, specific markup types for each device. In addition, the developer can specify other content decisions be made at runtime based on device specific capabilities and features (which are all in the WURFL).
In March 2012, ScientiaMobile has announced the launch of the WURFL Cloud.[5]While the WURFL Cloud is a paid service, a free offer is made available to hobbyists and micro-companies for use on mobile sites with limited traffic.[6]Currently, the WURFL Cloud supports Java, Microsoft .NET, PHP, Ruby, Python,Node.jsand the Perl programming languages[7][8]
In October 2012, ScientiaMobile has announced the availability of aC++API, anApachemodule, anNGINXmodule andVarnish Cachemodule.[9]Later in November 2016, ScientiaMobile provided a module forthe HAProxy load balancer.[10]Differently from other WURFL APIs, the C++ API and the modules are distributed commercially exclusively. Several popularLinux distributionare supported throughRPMandDEBpackages.[11]
In 2014, WURFL.io was launched. WURFL.io features non-commercial products and services from ScientiaMobile:
WALL (Wireless Abstraction Library by Luca Passani) is aJSPtag librarythat lets a developer author mobile pages similar to plain HTML, while
deliveringWML,C-HTMLandXHTML Mobile Profileto the device from which theHTTP requestoriginates, depending on the actual capabilities of the device itself.[14]Device capabilities are queried dynamically using the WURFL API. A WALL port to PHP (called WALL4PHP) is also available.
WURFL is currently supported using the following.
The PHP/MySQL based Tera-WURFL API comes with a remote webservice that allows you to query the WURFL from any language that supports XML webservices[15]and includes clients for the following languages out of the box:
The August 29, 2011 update of WURFL included a new set of licensing terms. These terms set forth a number of licenses under which WURFL could be used. The free version of the license does not allow derivative works, and prevents direct access to the wurfl.xml file. As a result of the "no-derivates" clause, users are no longer permitted to add new device capabilities to the WURFL file either directly or through the submissions of "patches". A commercial license is required to utilize third-party API's with the WURFL Repository.
On January 3, 2012, ScientiaMobile filed aDMCAtakedown notice against the open-source device database OpenDDR that contains data from a previous version of WURFL. According to OpenDDR, these data were available under GPL.[16]
On March 22, 2012 it was announced by Matthew Weier O'Phinney thatZend Frameworkwould be dropping support for WURFL as of version 1.12.[17]This was due to the licence change which makes it incompatible with theZend Framework'slicensing[18]as the new licensing now requires that you "open-source the full source code of your web site, irrespective of the fact that you may modify the WURFL API or not."[19]
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Unstructured Supplementary Service Data, orUSSDis acommunication protocolused byGSMcellular telephonesto communicate with the service provider's computers. Agatewayis the collection of hardware and software required to interconnect two or more disparate networks, including performing protocol conversion.[1]
A USSD gateway routes USSD messages from the signalling network to a service application and back. A 'USSD gateway' service is also called a 'USSD center'.
USSD gatewayis based upon the ability of the delivery agent or the source to send and receive USSD messages. A USSD is a session-based protocol. USSD messages travel overGSMsignalling channels, and are used to query information and trigger services. Unlike similar services (SMSandMMS), which arestore and forwardbased, USSD establishes a real time session between mobile handset and application handling the service.
The difference between USSD gateways and other messaging gateways is that USSD gateways maintain a single interactive session once the connection is established.SMSandMMSstore and forward messages independently of the user session, similar to the wayemailis sent over theinternet.
Apart from PSSR and USSN, there is another method called Unstructured Supplementary Service Request (USSR) message that initiates a session by USSD Gateway to a Mobile User. This message can be used in conjunction with USSR initiated session to provide session based services like Menu services through USSD. Also, in the earlier phases of MAP (Mobile Application Part), PSSR message was called PSSD (PSS Data).
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ETSIand3rd Generation Partnership Project(3GPP) standards, such asGSMandLTE, definesupplementary service codesthat make it possible to query and set certain service parameters (e.g.,call forwarding) directly from mobile devices.
This article related totelecommunicationsis astub. You can help Wikipedia byexpanding it.
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https://en.wikipedia.org/wiki/Supplementary_service_codes
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SIM Application Toolkit(STK) is a standard of theGSMsystem which enables thesubscriber identity module(SIM card) to initiate actions which can be used for variousvalue-addedservices.[1]Similar standards exist for other network and card systems, with theUSIM Application Toolkit(USAT) forUSIMsused by newer-generation networks being an example. A more general name for this class ofJava Card-based applications running onUICC cardsis theCard Application Toolkit(CAT).[2][3]
The SIM Application Toolkit consists of a set of commands programmed into the SIM which define how the SIM should interact directly with the outside world and initiates commands independently of the handset and the network.[4]This enables the SIM to build up an interactive exchange between a network application and the end user and access, or control access to, the network.[1]The SIM also gives commands to the handset such as displaying menus and/or asking for user input.[5]
STK has been deployed by many mobile operators around the world for many applications, often where a menu-based approach is required, such asMobile Bankingand content browsing.[1]Designed as a single application environment, the STK can be started during the initial power up of the SIM card[5]and is especially suited to low level applications with simple user interfaces.[6]
InGSMnetworks, the SIM Application Toolkit is defined by the GSM 11.14 standard released in 2001.[1][4][6]From release 4 onwards, GSM 11.14 was replaced by 3GPP TS 31.111 which also includes the specifications of the USIM Application Toolkit for 3/4G networks.[2]
UpdatingAndroidsoftware is done over GSM where the SIM Toolkit may install automatically with new software regardless of automatic install applications.
Change in applications and menus stored on the SIM is difficult after the customer takes delivery of theSIMand sometimes may be recognized as surveillance software.
To deliver updates, either the SIM must be returned and exchanged for a new one (which can be costly and inconvenient) or the application updates must be deliveredover-the-air (OTA)using specialized, optional SIM features. As of October 2010[update],mobile network operatorscan, for example, deliver updated STK application menus by sending a secureSMSto handsets that include a Toolbox (S@T) compliantwireless internet browser (WIB). When using a SIM card compliant to the BIP (Bearer Independent protocol[9]) in a BIP-compliant handset, the updates can be delivered very quickly as well (depending upon the network connectivity available to and supported by the handset, i.e.GPRS/3Gspeed). It might also be possible to change the menu of STK applications based on the Wireless Internet Gateway (WIG) specification.[10][11]The update limitations hinder the number and frequency of STK application deployments.[12]
STK has essentially no support for multimedia, only basic pictures.[8]
The STK technology has limited independent development support available.[8]
If a mobile phone does not support SIM Application Toolkit, users may not be able to use the service or network correctly. Issues with several mobile network operators have been noticed on smartphones that don't support STK, likeNokia N900.
USIM Application Toolkit (USAT) is the equivalent of STK for3Gnetworks.[4]USAT takes advantage of the multiapplication environment of 3G devices by not activating until a specific application has been selected, unlike STK which is activated at startup.[13]Some functions are card related rather than application related.[5]
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Mobility managementis one of the major functions of aGSMor
aUMTSnetwork that allowsmobile phonesto work. The aim of mobility management is to track where thesubscribersare, allowing calls,SMSand othermobile phone servicesto be delivered to them.
AGSMorUMTSnetwork, like allcellular networks, is basically aradio networkof individual cells, known as base stations. Each base station covers a small geographical area which is part of a uniquely identifiedlocation area. By integrating the coverage of each of these base stations, a cellular network provides a radio coverage over a much wider area. For GSM, a base station is called abase transceiver station(BTS), and for UMTS it is called aNode B. A group of base stations is named a location area, or arouting area.
The location update procedure allows amobiledevice to inform the cellular network whenever it moves from one location area to the next. Mobiles are responsible for detecting location area codes (LAC). When a mobile finds that the location area code is different from its last update, it performs another update by sending to the network, a location update request, together with its previous location, and itsTemporary Mobile Subscriber Identity(TMSI).
The mobile also stores the current LAC in the SIM card, concatenating it to a list of recently used LACs. This is done to avoid unnecessary IMSI attachment procedures in case the mobile has been forced to switch off (by removing the battery, for example) without having a chance to notify the network with an IMSI detach and then switched on right after it has been turned off. Considering the fact that the mobile is still associated with the Mobile Switching Center/Visitor Location Register(MSC/VLR) of the current location area, there is no need for any kind of IMSI attachment procedures to be done.
There are several reasons why a mobile may provide updated location information to the network. Whenever a mobile is switched on or off, the network may require it to perform anIMSI attachor IMSI detach location update procedure. Also, each mobile is required to regularly report its location at a set time interval using aperiodic location updateprocedure. Whenever a mobile moves from one location area to the next while not on a call, arandom locationupdate is required. This is also required of a stationary mobile that reselects coverage from a cell in a different location area, because of signal fade. Thus, a subscriber has reliable access to the network and may be reached with a call, while enjoying the freedom of mobility within the whole coverage area.
When a subscriber is paged in an attempt to deliver a call or SMS and the subscriber does not reply to that page then the subscriber is marked as absent in both the MSC/VLR and the Home Location Register (HLR) (Mobile not reachable flag MNRF is set). The next time the mobile performs a location update, the HLR is updated and the mobile not reachable flag is cleared.
The Temporary Mobile Subscriber Identity (TMSI) is the identity that is most commonly sent between the mobile and the network. Depending on the necessary precision, a TMSI may be set by a VLR, SGSN, or MME. In the least-precise case, TMSI is randomly assigned by the VLR to every mobile in the area, the moment it is switched on, in order to support identity confidentiality. The number is local to a location area, and so it has to be updated each time the mobile moves to a new geographical area.
The VLR, SGSN, and MME must be capable of correlating an allocated TMSI with the IMSI of the MS to which it is allocated. An MS may be allocated three TMSIs; one for services provided through the MSC (the TMSI), one for services provided through the SGSN (the packet-TMSI or P-TMSI), and one for the services provided the MME (the MME-TMSI or M-TMSI; a part of the GUTI).
The network can also change the TMSI of the mobile at any time. And it normally does so, in order to avoid the subscriber from being identified, and tracked by eavesdroppers on the radio interface. This makes it difficult to trace which mobile is which, except briefly, when the mobile is just switched on, or when the data in the mobile becomes invalid for one reason or another. At that point, the global "international mobile subscriber identity" (IMSI) must be sent to the network. The IMSI is sent as rarely as possible, to avoid it being identified and tracked.
A key use of the TMSI is in paging a mobile. "Paging" is the one-to-one communication between the mobile and the base station. The most important use of broadcast information is to set up channels for "paging". Every cellular system has abroadcastmechanism to distribute such information to a plurality of mobiles.
Size of TMSI is 4 octet with full hex digits but can't be allFFbecause the SIM uses 4 octets with all bits equal to 1 to indicate that no valid TMSI is available.[1]
Roamingis one of the fundamental mobility management procedures of allcellular networks. Roaming is defined[2]as the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the homenetwork, by means of using a visited network. This can be done by using a communication terminal or else just by using the subscriber identity in the visited network. Roaming is technically supported by a mobility management,authentication,authorizationandbillingprocedures.
A "location area" is a set of base stations that are grouped together tooptimizesignaling. Typically, tens or even hundreds of base stations share a singleBase Station Controller(BSC) in GSM, or aRadio Network Controller(RNC) in UMTS. The BSC / RNC is the intelligence behind the base stations; it handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers between base stations.
Each location area has an assigned unique identifier, made up of numbers, called a "location area code" (LAC). The LAC is broadcast by each base station at regular intervals. Within a location area, each base station is assigned a distinct "cell identifier" (CI) number, see alsoCell Global Identity.
If the location areas are large and moderately populated, there will likely be a high number of mobiles operating simultaneously, resulting in very high paging traffic. This is due to the fact that every paging request has to be broadcast to every base station in the location area. Ultimately, this wastesbandwidthand power on mobile devices by requiring them to listen for broadcast messages too often. Similarly if on the other hand, there are too many small location areas, the mobile device must contact the network very often for changes of location, which will also drain the device’s battery. Therefore, it is important to strike a balance between the size of the location area and the number of mobile device users in the location area[citation needed].
The routing area is the packet-switched domain equivalent of the location area. A "routing area" is normally a subdivision of a "location area". Routing areas are used by mobiles which areGPRS-attached. GPRS is optimized for "bursty"data communicationservices, such as wireless internet/intranet, and multimedia services. It is also known as GSM-IP ("Internet Protocol") because it will connect users directly toInternet Service Providers
The bursty nature of packet traffic means that more paging messages are expected per mobile, and so it is worth knowing the location of the mobile more accurately than it would be with traditional circuit-switched traffic. A change from routing area to routing area (called a "Routing Area Update") is done in an almost identical way to a change from location area to location area. The main differences are that the "Serving GPRS Support Node" (SGSN) is the element involved.
The tracking area is theLTEcounterpart of the location area and routing area. A tracking area is a set of cells. Tracking areas can be grouped into lists of tracking areas (TA lists), which can be configured on theUser Equipment(UE). Tracking area updates are performed periodically or when the UE moves to a tracking area that is not included in its TA list.
Operators can allocate different TA lists to different UEs. This can avoid signaling peaks in some conditions: for instance, the UEs of passengers of a train may not perform tracking area updates simultaneously.
On the network side, the involved element is theMobility Management Entity(MME). MME configures TA lists usingNASmessages like Attach Accept, TAU Accept or GUTI Reallocation Command.
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Radio resource management(RRM) is the system level management ofco-channel interference, radio resources, and other radio transmission characteristics inwireless communicationsystems, for examplecellular networks,wireless local area networks,wireless sensorsystems, and radiobroadcasting networks.[1][2]RRM involves strategies and algorithms for controlling parameters such as transmit power, user allocation, beamforming, data rates, handover criteria, modulation scheme, error coding scheme, etc. The objective is to utilize the limited radio-frequency spectrum resources and radio network infrastructure as efficiently as possible.
RRM concerns multi-user and multi-cell network capacity issues, rather than the point-to-pointchannel capacity. Traditional telecommunications research and education often dwell onchannel codingandsource codingwith a single user in mind, but when several users and adjacent base stations share the same frequency channel it may not be possible to achieve the maximum channel capacity. Efficient dynamic RRM schemes may increase the system spectral efficiency by anorder of magnitude, which often is considerably more than what is possible by introducing advanced channel coding and source coding schemes. RRM is especially important in systems limited by co-channel interference rather than by noise, for examplecellular systemsandbroadcast networkshomogeneously covering large areas, andwireless networksconsisting of many adjacentaccess pointsthat mayreusethe same channel frequencies.
The cost for deploying a wireless network is normally dominated by base station sites (real estate costs, planning, maintenance, distribution network, energy, etc.) and sometimes also by frequency license fees. So, the objective of radio resource management is typically to maximize thesystem spectral efficiencyinbit/s/Hz/area unitorErlang/MHz/site, under some kind of user fairness constraint, for example, that thegrade of serviceshould be above a certain level. The latter involves covering a certain area and avoidingoutagedue toco-channel interference,noise, attenuation caused by path losses,fadingcaused by shadowing andmultipath,Doppler shiftand other forms ofdistortion. The grade of service is also affected byblockingdue toadmission control,scheduling starvationor inability to guaranteequality of servicethat is requested by the users.
While classical radio resource managements primarily considered the allocation of time and frequency resources (with fixed spatial reuse patterns), recentmulti-user MIMOtechniques enables adaptive resource management also in the spatial domain.[3]In cellular networks, this means that the fractional frequency reuse in theGSMstandard has been replaced by a universal frequency reuse inLTEstandard.
Static RRM involves manual as well as computer-aided fixedcell planningorradio network planning. Examples:
Static RRM schemes are used in many traditional wireless systems, for example1Gand2Gcellular systems, in today's wireless local area networks and in non-cellular systems, for example broadcasting systems. Examples of static RRM schemes are:
Dynamic RRM schemes adaptively adjust the radio network parameters to the traffic load, user positions, user mobility, quality of service requirements, base station density, etc. Dynamic RRM schemes are considered in the design of wireless systems, in view to minimize expensive manual cell planning and achieve "tighter"frequency reusepatterns, resulting in improvedsystem spectral efficiency.
Some schemes are centralized, where several base stations and access points are controlled by aRadio Network Controller(RNC). Others are distributed, either autonomous algorithms inmobile stations,base stationsor wirelessaccess points, or coordinated by exchanging information among these stations.[1]
Examples of dynamic RRM schemes are:
Future networks like theLTEstandard (defined by3GPP) are designed for a frequency reuse of one. In such networks, neighboring cells use the same frequency spectrum. Such standards exploitSpace Division Multiple Access (SDMA)and can thus be highly efficient in terms of spectrum, but required close coordination between cells to avoid excessive inter-cell interference. Like in most cellular system deployments, the overall system spectral efficiency is not range limited or noise limited, but interference limited.[1]Inter-cell radio resource management coordinates resource allocation between different cell sites by usingmulti-user MIMOtechniques. There are various means ofinter-cell interference coordination(ICIC) already defined in the standard.[4]Dynamic single-frequency networks, coordinated scheduling, multi-site MIMO or joint multi-cell precoding are other examples for inter-cell radio resource management.[3][5]
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Wi-Fi calling, also calledVoWiFi,[1]refers tomobile phonevoice calls and data that are made overIPnetworks usingWi-Fi, instead of thecell towersprovided bycellular networks.[2]Using this feature, compatible handsets are able to route regular cellular calls through a wireless LAN (Wi-Fi) network withbroadband Internet, while seamlessly changing connections between the two where necessary.[3]This feature makes use of theGeneric Access Network(GAN) protocol, also known asUnlicensed Mobile Access(UMA).[4][5]
Voice over wireless LAN(VoWLAN), alsovoice over Wi‑Fi(VoWiFi[6]), is the use of awirelessbroadband network according to theIEEE 802.11standards for the purpose of vocal conversation. In essence, it isvoice over IP(VoIP) over aWi-Finetwork.
Essentially, GAN/UMA allows cell phone packets to be forwarded to a network access point over the internet, rather than over-the-air usingGSM/GPRS,UMTSor similar. A separate device known as a "GAN Controller" (GANC)[5]receives this data from the Internet and feeds it into the phone network as if it were coming from an antenna on a tower. Calls can be placed from or received to the handset as if it were connected over-the-air directly to the GANC'spoint of presence, making the call invisible to the network as a whole.[7]This can be useful in locations with poor cell coverage where some other form ofinternet accessis available,[2]especially at the home or office. The system offers seamlesshandoff, so the user can move from cell to Wi-Fi and back again with the same invisibility that the cell network offers when moving from tower to tower.[3]
Since the GAN system works over the internet, a UMA-capable handset can connect to its service provider from any location with internet access. This is particularly useful for travelers, who can connect to their provider's GANC and make calls into their home service area from anywhere in the world.[citation needed]This is subject to the quality of the internet connection, however, and may not work well over limited bandwidth or long-latency connection. To improvequality of service(QoS) in the home or office, some providers also supply a specially programmedwireless access pointthat prioritizes UMA packets.[8]Another benefit of Wi-Fi calling is that mobile calls can be made through the internet using the same native calling client; it does not require third-partyVoice over IP(VoIP) closed services likeWhatsApporSkype, relying instead on the mobile cellular operator.[9]
The GAN protocol that extends mobile voice, data and multimedia (IP Multimedia Subsystem/Session Initiation Protocol(IMS/SIP)) applications over IP networks. The latest generation system is named orVoWiFiby a number of handset manufacturers, includingAppleandSamsung, a move that is being mirrored by carriers likeT-Mobile USandVodafone.[citation needed]The service is dependent on IMS, IPsec,IWLANandePDG.
The original Release 6 GAN specification supported a 2G (A/Gb) connection from the GANC into the mobile core network (MSC/GSN). Today[when?]all commercial GAN dual-mode handset deployments are based on a 2G connection and all GAN enabled devices are dual-mode 2G/Wi-Fi. The specification, though, defined support for multimode handset operation. Therefore, 3G/2G/Wi-Fi handsets are supported in the standard. The first 3G/UMA devices were announced in the second half of 2008.
A typical UMA/GAN handset will have four modes of operation:
In all cases, the handset scans for GSM cells when it first turns on, to determine its location area. This allows the carrier to route the call to the nearest GANC, set the correct rate plan, and comply with existing roaming agreements.
At the end of 2007, the GAN specification was enhanced to support 3G (Iu) interfaces from the GANC to the mobile core network (MSC/GSN). This native 3G interface can be used for dual-mode handset as well as 3Gfemtocellservice delivery. The GAN release 8 documentation describes these new capabilities.
While UMA is nearly always associated with dual-mode GSM/Wi-Fi services, it is actually a ‘generic’ access network technology that provides a generic method for extending the services and applications in an operator's mobile core (voice, data, IMS) over IP and the public Internet.
GAN defines a secure, managed connection from the mobile core (GANC) to different devices/access points over IP.
A Wi-Fi network that supports voice telephony must be carefully designed in a way that maximizes performance and is able to support the applicable call density.[12]A voice network includes call gateways in addition to the Wi-Fi access points. The gateways provide call handling among wireless IP phones and connections to traditional telephone systems. The Wi-Fi network supporting voice applications must provide much stronger signal coverage than what's needed for most data-only applications. In addition, the Wi-Fi network must provide seamless roaming between access points.
UMA was developed by a group of operator and vendor companies.[13]The initial specifications were published on 2 September 2004. The companies then contributed the specifications to the3rd Generation Partnership Project(3GPP) as part of 3GPP work item "Generic Access to A/Gb interfaces". On 8 April 2005, 3GPP approved specifications for Generic Access to A/Gb interfaces for 3GPP Release 6 and renamed the system to GAN.[14][15]But the termGANis little known outside the 3GPP community, and the termUMAis more common in marketing.[citation needed]
For carriers:
For subscribers:
The first service launch was BT withBT Fusionin the autumn of 2005. The service is based on pre-3GPP GAN standard technology. Initially, BT Fusion used UMA over Bluetooth with phones fromMotorola. From January 2007, it used UMA over 802.11 with phones from Nokia, Motorola and Samsung[18]and was branded as a "Wi-Fi mobile service". BT has since discontinued the service.
On August 28, 2006,TeliaSonerawas the first to launch an 802.11 based UMA service called "Home Free".[19]The service started in Denmark but is no longer offered.
On September 25, 2006Orangeannounced its "Unik service", also known as Signal Boost in the UK.[20][21]However this service is no longer available to new customers in the UK.[22]The announcement, the largest to date, covers more than 60m of Orange's mobile subscribers in the UK, France, Poland, Spain and the Netherlands.
Cincinnati Bellannounced the first UMA deployment in the United States.[23]The service, originally called CB Home Run, allows users to transfer seamlessly from the Cincinnati Bell cellular network to a home wireless network or to Cincinnati Bell's WiFi HotSpots. It has since been rebranded as Fusion WiFi.
This was followed shortly byT-Mobile USon June 27, 2007.[24]T-Mobile's service, originally named "Hotspot Calling", and rebranded to "Wi-Fi Calling" in 2009, allows users to seamlessly transfer from the T-Mobile cellular network to an 802.11x wireless network or T-Mobile HotSpot in the United States.
In Canada, bothFidoandRogers Wirelesslaunched UMA plans under the names UNO and Rogers Home Calling Zone (later rebranded Talkspot, and subsequently rebranded again as Wi-Fi Calling), respectively, on May 6, 2008.[25]
In Australia, GAN has been implemented by Vodafone, Optus and Telstra.[26]
Since 10 April 2015, Wi-Fi Calling has been available for customers ofEEin the UK initially on theNokia Lumia 640andSamsung Galaxy S6andSamsung Galaxy S6 Edgehandsets.[27]
In March 2016,Vodafone Netherlandslaunched Wi-Fi Calling support along withVoLTE.[28]
Since the Autumn of 2016, Wifi Calling / Voice over Wifi has been available for customers of Telenor Denmark, including the ability to do handover to and from the 4G (VoLTE) network. This is available for several Samsung and Apple handsets.
AT&T[29]andVerizon[30]are going to launch Wi-Fi calling in 2015.
Industry organisationUMA Todaytracks all operator activities and handset development.
In September 2015, South African cellular network Cell C launched WiFi Calling on its South African network.[31]
In November 2024, Belgian cellular network Voo launched WiFi Calling on its Belgian network.[32]
GAN/UMA is not the first system to allow the use of unlicensed spectrum to connect handsets to a GSM network. TheGIP/IWPstandard forDECTprovides similar functionality, but requires a more direct connection to the GSM network from the base station. While dual-mode DECT/GSM phones have appeared, these have generally been functionally cordless phones with a GSM handset built-in (or vice versa, depending on your point of view), rather than phones implementing DECT/GIP, due to the lack of suitable infrastructure to hook DECT base-stations supporting GIP to GSM networks on an ad-hoc basis.[33]
GAN/UMA's ability to use the Internet to provide the "last mile" connection to the GSM network solves the major issue that DECT/GIP has faced. Had GIP emerged as a practical standard, the low power usage of DECT technology when idle would have been an advantage compared to GAN.[citation needed]
There is nothing preventing an operator from deploying micro- and pico-cells that use towers that connect with the home network over the Internet. Several companies have developed femtocell systems that do precisely that, broadcasting a "real" GSM or UMTS signal, bypassing the need for special handsets that require 802.11 technology. In theory, such systems are more universal, and again require lower power than 802.11, but their legality will vary depending on the jurisdiction, and will require the cooperation of the operator. Further, users may be charged at higher cell phone rates, even though they are paying for the DSL or other network that ultimately carries their traffic; in contrast, GAN/UMA providers charge reduced rates when making calls off the providers cellular phone network.[citation needed]
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The3GPPhas defined theVoice Call Continuity(VCC) specifications in order to describe how avoice callcan be persisted, as a mobile phone moves between circuit switched and packet switched radio domains (3GPP TS 23.206).
Many mobile phones are becoming available that support both cellular and other broadband radio technologies. For example, theNokiaN Series and E Series devices support bothGSMandWiFi. Similar devices fromSony Ericsson,BlackBerry,Samsung,HTC,Motorolaand even theApple iPhoneprovide comparable dual mode technology.WiMAXsupport is also being added and further handsets are emerging fromKyoceraand other vendors, which provide dual mode technology inCDMAphones. A wide range of Internet applications can then be accessed from mobile devices using wireless broadband technologies like WiFi and WiMAX. For example,VoIPtraffic can be carried over these alternative radio interfaces.
Whereas VoIP calls from mobile devices are controlled by IP infrastructure, according to the VCC specifications, calls to and from a cellular phone in the circuit switched domain are also anchored in an IP domain, for example theIP Multimedia Subsystem(IMS). As the handset becomes attached and detached from wireless access points such as WiFi hotspots, a client application in the device provides notifications of the radio conditions to a VCC platform in the network. This allows circuit switched and IP call legs to be originated and terminated such that the speech path is transferred between domains, transparently to the end user.
This technology is of interest to users as an example of the benefits that are achievable throughFixed Mobile Convergence(FMC). Since most WiFi and WiMAX access points will use fixed backhaul technologies, seamlessly moving between for example WiFi and GSM domains allows the best quality and most cost efficient radio to be used at any given point in time, irrespective of the transport technology used for the media. Similarly, service providers are interested in VCC in order to offer FMC products towards specific market segments, such as enterprise users. Cellular operators in particular can offer bundled services that consist of for example, a broadband connection with a WiFi router and a set of dual mode devices. This supports aFixed Mobile Substitution(FMS) business case where calls from the office can be carried as VoIP over WiFi and a broadband connection, while VCC technology allows these calls to be seamlessly handed over to cellular networks as the device moves to areas of poor WiFi coverage.
One limitation of VCC however, relates to the focus on voice service. In order to preserve the cellular telephony experience while users are WiFi attached, other features need to be replicated in the packet switched domain. For example, the 3GPP has defined SMS over IP specifications (3GPP TS 23.204) in order to describe how messaging functionality can be provided to end users that are present within IP based access networks. However, over several years a range of other business logic, such as GSM Supplementary Services within theHome Location Register(HLR) has been embedded within cellular networks. This functionality must also be realized within the IP domain in order to provide full service continuity between multiple access networks.
In the context of the Release 8 of3GPPstandards, VCC was replaced by a wider concept that covers all services provided byIMS. This work resulted in the specification ofIMS Service Continuity[1]andIMS Centralized Services (ICS),[2]which are meant to be used in particular to provide the continuity of voice calls betweenLTEand legacy 2G/3G networks.
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https://en.wikipedia.org/wiki/Voice_call_continuity
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In healthcare, achange-of-shift reportis a meeting between healthcare providers at the change of shift in which vital information about and responsibility for thepatientis provided from the off-going provider to the on-coming provider (Groves, Manges, Scott-Cawiezell, 2016).[1]Other names for change-of-shift report include handoff, shift report, handover, or sign-out. Change-of-shift report is key toinpatientcare because healthcare providers (nurses,physicians,nursing assistantsetc.) are essential to providing around the clock care.[1]
During report, the outgoing nurses discuss with the oncoming nurses the condition of each patient and any changes that have occurred to the patient during the shift. The purpose is not to cover all details recorded in the patient's medical record, but to summarize individual patient progress.[2]The content of the report often depends on the local organization.
While report is necessary in order to communicate important information between nurses, various problems are posed by the giving of report.
There is evidence to suggest that performing change of shift report at the bedside is key to patient safety. In 2001, theInstitute of Medicinestated that "it is in inadequate handoff that safety often fails first."[5]This is because at every change of shift, there is a chance for miscommunication about vital patient information.[1]A specific type of change-of-shift report isNursing Bedside Shift Reportin which the off going nurse provides change-of-shift report to the on coming nurse at the patient's bedside.[1][6][7]Since 2013, giving report at the patient bedside has been recommend by theAgency for Healthcare Research and Quality(AHRQ) to improve patient safety.[6]However, it wasn't until recently that it was knownhowNursing Bedside Shift Report works to keep patients safe.[1]A qualitative study by the nurse researchers Groves, Manges, and Scott-Cawiezell developed agrounded theoryon how bedside nurses can use nursing bedside shift report (NBSR) to keep patients safe.[1]According to Groves et al. (2016)[1]NBSR is used by nurses to keep patients safe by "reducing risk of harm through conveying the patient story from shift to shift." Additionally, NBSR is key to reducing risk of harm because it supports the nurses ability to identify and address risks.[1][8]Preliminary results from asimulationstudy found that the way nursing report is structured, can affect nurses' safety oriented behaviors (like checking for pressure ulcers, double checking medications, decreasing room clutter to prevent falls).[9]
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https://en.wikipedia.org/wiki/Change-of-shift_report
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Follow-the-sun(FTS), a sub-field ofglobally distributed software engineering (GDSE), is a type of global knowledge workflow designed in order to reduce thetime to market, in which the knowledge product is owned and advanced by a production site in one time zone and handed off at the end of their work day to the next production site that is several time zones west to continue that work.[1][2]Ideally, the work days in these time zones overlap such that when one site ends their day, the next one starts.
FTS has the potential to significantly increase the total development time per day (as viewed from the perspective of a single time zone): with two sites the development time can increase to up to 16 hours, or up to 24 hours if there are three sites, reducing the development duration by as much as 67%.
It is not commonly practiced in industry and has few documented cases where it is applied successfully.[3]This is likely because of its uncommon requirements, leading to a lack of knowledge on how to successfully apply FTS in practice.
Follow-the-sun can be traced back to the mid-1990s whereIBMhad the first global software team which was specifically set up to take advantages of FTS.[4]The team was spread out across five sites around the globe. Unfortunately, in this case FTS was unsuccessful because it was uncommon to hand off the software artifacts daily.
Two other cases of FTS at IBM have been documented by Treinen and Miller-Frost.[3]The first team was spread out across a site in the United States and a site in Australia. FTS was successful for this team. The second team was spread out across a site in the United States and a site in India. In this case FTS was unsuccessful because of miscommunication, time zone issues and cultural differences.
FTS is based on four principles:
An important step in defining FTS is to disambiguate it from other globally distributed configurations to clearly state what FTS is not. These types of similar globally distributed configurations are not FTS:[2]
FTS's largest strength, spreading the development over multiple time zones, is simultaneously its largest weakness. Its distributed workflow is more complex to implement due to cultural and technical differences as well as the differences in time making coordination and communication challenging.
The main reason why FTS is difficult to implement is because the handoffs are an essential element that is hard to get right. The largest factor causing this difficulty is poor communication.[3]
There are few documented cases of companies successfully applying FTS.[3]Some companies have claimed to successfully implement FTS but these companies did not practice the daily handoffs.[3][6]However, a limited amount of successful applications of FTS that did include daily handoffs of artefacts, using a distributed-concurrent model,[2]were found by Cameron.[7]
Recent studies on FTS have moved to mathematical modeling of FTS.[8][9][10][11][12]The research is focused on the issue of speed and the issues around the handoffs.
As FTS is a sub-field of GDSE,[4]the sameagile software developmentmethodologies that are found to work well in GDSE work well with FTS.[2]In particular, Carmelet al.(2009) argue that agile software development methodologies assist the FTS principles because they:[1]
Krollet al.(2013) have researched papers published between 1990 and 2012 and found 36 best practices and 17 challenges for FTS.[13]The challenges were grouped in three categories: coordination, communication and culture. These challenges should be overcome to implement FTS successfully.
It is of great importance to select and adapt a methodology for the daily handoffs[1][13]e.g. usingagile software developmentor thewaterfall model.
Identified best practices are the use of agile methods and using technologies to develop FTS activities. Agile supports daily handoffs which is a critical challenge in FTS.[1]Management tools can be used to estimate and plan schedules, manage sprints and track progress. Additionally, technologies like conference video, emails and telephone calls are easy to implement and allow companies to perform synchronous and asynchronous communication between teams and works well in an agile environment.
A related concept isfollow-the-moon, which is scheduling work to be performed specifically during local night-time hours for reasons such as saving ondatacentercosts by usingcheaper night-time electricity[14]or spare processing power.
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https://en.wikipedia.org/wiki/Follow-the-sun
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Intelecommunications,broadbandorhigh speedis the wide-bandwidthdata transmissionthat exploits signals at a wide spread of frequencies or several different simultaneous frequencies, and is used in fastInternet access. Thetransmission mediumcan becoaxial cable,optical fiber,wireless Internet(radio),twisted paircable, orsatellite.
Originally used to mean 'using a wide-spread frequency' and for services that were analog at the lowest level, nowadays in the context ofInternet access, 'broadband' is often used to mean any high-speed Internet access that is seemingly always 'on' and is faster thandial-up accessover traditionalanalogorISDNPSTNservices.[1]
The idealtelecommunication networkhas the following characteristics:broadband,multi-media,multi-point,multi-rateand economical implementation for a diversity of services (multi-services).[2][3]TheBroadband Integrated Services Digital Network(B-ISDN) was planned to provide these characteristics.Asynchronous Transfer Mode(ATM) was promoted as a target technology for meeting these requirements.[3]
Different criteria for "broad" have been applied in different contexts and at different times. Its origin is in physics,acoustics, and radio systems engineering, where it had been used with a meaning similar to "wideband",[4][5]or in the context of audionoise reduction systems, where it indicated a single-band rather than a multiple-audio-band system design of thecompander. Later, with the advent ofdigital telecommunications, the term was mainly used for transmission overmultiple channels. Whereas apassbandsignal is also modulated so that it occupies higher frequencies (compared to abasebandsignal which is bound to the lowest end of the spectrum, seeline coding), it is still occupying a single channel. The key difference is that what is typically considered abroadband signalin this sense is a signal that occupies multiple (non-masking,orthogonal) passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry.
The term became popularized through the 1990s as a marketing term forInternet accessthat was faster thandial-up access(dial-up being typically limited to a maximum of 56 kbit/s). This meaning is only distantly related to its original technical meaning.
Since 1999, broadband Internet access has been a factor inpublic policy. In that year, at theWorld Trade OrganizationBiannual Conference called “Financial Solutions to Digital Divide” in Seattle, the term “Meaningful Broadband” was introduced to the world leaders, leading to the activation of a movement to close thedigital divide. Fundamental aspects of this movement are to suggest that the equitable distribution of broadband is a fundamental human right.[6]
Personal computing facilitated easy access, manipulation, storage, and exchange of information, and required reliable data transmission. Communicating documents by images and the use of high-resolution graphics terminals provided a more natural and informative mode of human interaction than do voice and data alone.Video teleconferencingenhances group interaction at a distance. High-definition entertainment video improves the quality of pictures, but requires much higher transmission rates.
These new data transmission requirements may require new transmission means other than the present overcrowded radio spectrum.[7][8]A modern telecommunications network (such as the broadband network) must provide all these different services (multi-services) to the user.
Conventionaltelephonycommunication used:
Modern services can be:
These aspects are examined individually in the following three sub-sections.[9]
A multimedia call may communicate audio, data, still images, or full-motionvideo, or any combination of these media. Each medium has different demands for communication quality, such as:
The information content of each medium may affect the information generated by other media. For example, voice could be transcribed into data via voice recognition, and data commands may control the way voice and video are presented. These interactions most often occur at the communication terminals, but may also occur within the network.[3][7]
Traditional voice calls are predominantly two party calls, requiring a point-to-point connection using only the voice medium. To access pictorial information in a remote database would require a point-to-point connection that sends low bit-rate queries to the database and high bit-rate video from the database. Entertainment video applications are largely point-to-multi-point connections, requiring one way communication of full motion video and audio from the program source to the viewers. Video teleconferencing involves connections among many parties, communicating voice, video, as well as data. Offering future services thus requires flexible management of the connection and media requests of a multipoint, multimedia communication call.[7][8]
A multirate service network is one which flexibly allocates transmission capacity to connections. A multimedia network has to support a broad range of bit-rates demanded by connections, not only because there are many communication media, but also because a communication medium may be encoded by algorithms with different bit-rates. For example, audio signals can be encoded with bit-rates ranging from less than 1 kbit/s to hundreds of kbit/s, using different encoding algorithms with a wide range of complexity and quality of audio reproduction. Similarly, full motion video signals may be encoded with bit-rates ranging from less than 1 Mbit/s to hundreds of Mbit/s. Thus a network transporting both video and audio signals may have to integrate traffic with a very broad range of bit-rates.[7][9]
Traditionally, different telecommunications services were carried via separate networks: voice on the telephone network, data oncomputer networkssuch aslocal area networks, video teleconferencing on private corporate networks, and television onbroadcastradio or cable networks.
These networks were largely engineered for a specific application and are not suited to other applications. For example, the traditional telephone network is too noisy and inefficient for bursty data communication. On the other hand, data networks which store and forward messages using computers had limited connectivity, usually did not have sufficient bandwidth for digitised voice and video signals, and suffer from unacceptable delays for the real-time signals. Television networks using radio or cables were largely broadcast networks with minimum switching facilities.[3][7]
It was desirable to have a single network for providing all these communication services to achieve the economy of sharing. This economy motivates the general idea of an integrated services network. Integration avoids the need for many overlaying networks, which complicates network management and reduces flexibility in the introduction and evolution of services. This integration was made possible with advances in broadband technologies and high-speed information processing of the 1990s.[3][7]
While multiple network structures were capable of supporting broadband services, an ever-increasing percentage of broadband and MSO providers opted for fibre-optic network structures to support both present and future bandwidth requirements.
CATV(cable television),HDTV(high definition television),VoIP(voice over internet protocol), andbroadband internetare some of the most common applications now being supported by fibre optic networks, in some cases directly to the home (FTTh – Fibre To The Home). These types of fibre optic networks incorporate a wide variety of products to support and distribute the signal from the central office to an optic node, and ultimately to the subscriber (end-user).
Intelecommunications, a broadband signalling method is one that handles a wide band of frequencies. "Broadband" is a relative term, understood according to its context. The wider (or broader) thebandwidthof a channel, the greater the data-carrying capacity, given the same channel quality.
Inradio, for example, a very narrow band will carryMorse code, a broader band will carry speech, and a still broader band will carrymusicwithout losing the highaudio frequenciesrequired for realisticsound reproduction. This broad band is often divided into channels or "frequency bins" usingpassbandtechniques to allowfrequency-division multiplexinginstead of sending a higher-quality signal.
In data communications, a56k modemwill transmit a data rate of 56 kilobits per second (kbit/s) over a 4-kilohertz-widetelephone line(narrowband orvoiceband). In the late 1980s, theBroadband Integrated Services Digital Network(B-ISDN) used the term to refer to a broad range ofbit rates, independent of physical modulation details.[10]The various forms ofdigital subscriber line(DSL) services arebroadbandin the sense that digital information is sent over multiple channels. Each channel is at a higher frequency than thebasebandvoice channel, so it can supportplain old telephone serviceon a single pair of wires at the same time.[11]However, when that same line is converted to anon-loadedtwisted-pair wire (no telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry up to 100 megabits per second using very high-bit rate digital subscriber line (VDSLor VHDSL) techniques.[12]
Modern networks have to carry integratedtrafficconsisting of voice, video and data. TheBroadband Integrated Services Digital Network(B-ISDN) was designed for these needs.[13]The types of traffic supported by a broadband network can be classified according to three characteristics:[14]
Cellular networksutilize various standards for data transmission, including5Gwhich can support one million separate devices per square kilometer.
The types of traffic found in a broadband network (with examples) and their respective requirements are summarised in Table 1.
Manycomputer networksuse a simpleline codeto transmit one type of signal using a medium's full bandwidth using itsbaseband(from zero through the highest frequency needed). Most versions of the popularEthernetfamily are given names, such as the original 1980s10BASE5, to indicate this. Networks that usecable modemson standardcable televisioninfrastructure are called broadband to indicate the wide range of frequencies that can include multiple data users as well as traditional television channels on the same cable. Broadband systems usually use a differentradio frequencymodulated by the data signal for each band.[15]
The total bandwidth of the medium is larger than the bandwidth of any channel.[16]
The10BROAD36broadband variant of Ethernet was standardized by 1985, but was not commercially successful.[17][18]
TheDOCSISstandard became available to consumers in the late 1990s, to provideInternet accessto cable television residential customers. Matters were further confused by the fact that the10PASS-TSstandard for Ethernet ratified in 2008 used DSL technology, and both cable and DSL modems often have Ethernet connectors on them.
Atelevisionantenna may be described as "broadband" because it is capable of receiving a wide range of channels, while e.g. a low-VHF antenna is "narrowband" since it receives only 1 to 5 channels. The U.S. federal standard FS-1037C defines "broadband" as a synonym forwideband.[19]"Broadband" inanalogvideodistribution is traditionally used to refer to systems such ascable television, where the individual channels aremodulatedon carriers at fixed frequencies.[20]In this context,basebandis the term'santonym, referring to a single channel of analog video, typically incompositeform with separate basebandaudio.[21]The act of demodulating converts broadband video to baseband video. Fiber optic allows the signal to be transmitted farther without being repeated. Cable companies use a hybrid system using fiber to transmit the signal to neighborhoods and then changes the signal from light to radio frequency to be transmitted over coaxial cable to homes. Doing so reduces the use of having multiple head ends. Ahead endgathers all the information from the local cable networks and movie channels and then feeds the information into the system.
However, "broadband video" in the context ofstreamingInternet video has come to mean video files that havebit-rateshigh enough to require broadband Internet access for viewing. "Broadband video" is also sometimes used to describeIPTVVideo on demand.[22]
Power lineshave also been used for various types ofdata communication. Although some systems for remote control are based onnarrowbandsignaling, modern high-speed systems use broadband signaling to achieve very high data rates. One example is theITU-TG.hnstandard, which provides a way to create alocal area networkup to 1 Gigabit/s (which is considered high-speed as of 2014) using existing home business and home wiring (including power lines, but also phone lines andcoaxial cables).
In 2014, researchers atKorea Advanced Institute of Science and Technologymade developments on the creation of ultra-shallow broadbandoptical instruments.[23]
In the context ofInternet access, the term "broadband" is used loosely to mean "access that is always on and faster than the traditional dial-up access".[24][25]
A range of more precise definitions of speed have been prescribed at times, including:
Broadband Internet service in the United States was effectively treated or managed as apublic utilitybynet neutralityrules[30][31][32][33][34]until being overturned by the FCC in December 2017.[35]
A number of national and international regulators categorize broadband connections according to upload and download speeds, stated inMbit/s(megabitspersecond).
In Australia, theAustralian Competition and Consumer Commissionalso requiresInternet Service Providersto quote speed during night time and busy hours[44]
Bandwidth has historically been very unequally distributed worldwide, with increasing concentration in the digital age. Historically only 10 countries have hosted 70–75% of the global telecommunication capacity (see pie-chart Figure on the right).[45]In 2014, only three countries (China, the US, and Japan) host 50% of the globally installed telecommunication bandwidth potential. The U.S. lost its global leadership in terms of installed bandwidth in 2011, being replaced by China, which hosts more than twice as much national bandwidth potential in 2014 (29% versus 13% of the global total).[45]
Nation specific:
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https://en.wikipedia.org/wiki/Broadband
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Amobile broadband modem, also known aswireless modemorcellular modem, is a type ofmodemthat allows apersonal computeror arouterto receivewirelessInternet accessvia amobile broadbandconnection instead of usingtelephoneorcable televisionlines. A mobile Internet user can connect using a wireless modem to a wirelessInternet Service Provider(ISP) to getInternet access.[1][2]
While someanaloguemobile phones provided a standardRJ11telephone socket into which a normal landline modem could be plugged, this only provided slowdial-upconnections, usually 2.4 kilobit per second (kbit/s) or less. The next generation of phones, known as 2G (for 'second generation'), were digital, and offered faster dial-up speeds of 9.6 kbit/s or 14.4 kbit/s without the need for a separate modem. A further evolution calledHSCSDused multiple GSM channels (two or three in each direction) to support up to 43.2 kbit/s. All of these technologies still required their users to have a dial-upISPto connect to and provide the Internet access - it was not provided by the mobile phone network itself.
The release of2.5Gphones with support forpacketdata changed this. The 2.5G networks break both digital voice and data into small chunks, and mix both onto the network simultaneously in a process calledpacket switching. This allows the phone to have a voice connection and a data connection at the same time, rather than a single channel that has to be used for one or the other. The network can link the data connection into a company network, but for most users the connection is to the Internet. This allows web browsing on the phone, but a PC can also tap into this service if it connects to the phone. The PC needs to send a special telephone number to the phone to get access to the packet data connection. From the PC's viewpoint, the connection still looks like a normal PPP dial-up link, but it is all terminating on the phone, which then handles the exchange of data with the network. Speeds on 2.5G networks are usually in the 30–50 kbit/s range.
The firstpersonal computerwith a built-in mobile broadband modem was the ITC 286 CAT, a laptop byIntelligence Technology Corporation. Released in 1988, it featured aHayes-compatibleAMPSmodem capable of transmitting data at 1.2 kbit/s.[3][4]
3Gnetworks have taken this approach to a higher level, using different underlying technology but the same principles. They routinely provide speeds over 300 kbit/s. Due to the now increased internet speed, internet connection sharing viaWLANhas become a workable reality. Devices which allow internet connection sharing or other types of routing on cellular networks are called alsocellular routers.
A further evolution is the3.5GtechnologyHSDPA, which provides speeds of multipleMegabits per second. Several of themobile network operatorsthat provide 3G or faster wireless internet access offer plans and wireless modems that enable computers to connect to and access the internet. These wireless modems are typically in the form of a small USB based device or a small, portable mobile hotspot that acts as a WiFi access point (hotspot) to enable multiple devices to connect to the internet.WiMAXbased services that provide high speed wireless internet access are available in some countries and also rely on wireless modems that connect to the provider's wireless network. Wireless USB modems are nicknamed as "dongles".
Early 3G mobile broadband modems used thePCMCIAorExpressCardports, commonly found on legacy laptops. The expression "connect card" (instead of connection card) had been registered and used the first time byVodafoneas brand for its products but now is become abrandnomerorgenericized trademarkused incolloquialorcommercialspeech for similar product, made by different manufacturers, too. Major producers areHuawei,Option N.V., Novatel Wireless. More recently, the expression "connect card" is also used to identify internetUSBkeys. Vodafone brands this type of device as a Vodem.[5]
Often a mobile network operator will supply a 'locked' modem or other wireless device that can only be used on their network. It is possible to use online unlocking services that will remove the 'lock' so the device accepts SIM cards from any network.
Standalone mobile broadband modems are designed to be connected directly to one computer. In the past thePCMCIAandExpressCardstandards were used to connect to the computer. AsUSBconnectivity became almost universal, these various standards were largely superseded by USB modems in the early 21st century. Some models haveGPSsupport, providing geographical location information.[6]
Many mobile broadband modems sold nowadays also have built-in routing capabilities. They provide traditional networking interfaces such asEthernet,USBandWi-Fi.[7]
Numeroussmartphonessupport theHayes command setand therefore can be used as a mobile broadband modem. Somemobile network operatorscharge a fee for this facility,[8]if able to detect the tethering. Other networks have an allowance for full speed mobile broadband access, which—if exceeded—can result in overage charges or slower speeds.[9]
An Internet-accessing smartphone may have the same capabilities as a standalone modem, and, when connected via a USB cable to a computer, can serve as a modem for the computer. Smartphones with built-in Wi-Fi also typically provide routing andwireless access pointfacilities. This method of connecting is commonly referred to as "tethering."[9]
There are competingcommon carriersbroadcastingsignal in most countries.
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https://en.wikipedia.org/wiki/Cellular_router
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TheDigRFworking group was formed as aMIPI Alliance(MIPI)working groupin April 2007. The group is focused on developing specifications for wireless mobileRFICto base-band IC (BBIC) interfaces in mobile devices.
The group's current charter is split into short-term and long-term development efforts. The short-term development will focus on a specification targeted for completion by end of 2007 forLTEandWiMaxair interfacestandards. The longer term development will focus on future air interface standards which promise further improvements in high speed, data optimized traffic. In addition, the future work will seek to harmonize efforts with the MIPI'sPHYandUniProworking groups.
These specifications will describe the logical, electrical and timing characteristics of the digital RF-BB Interface with sufficient detail to allow physical implementation of the interface, and with sufficient rigor that implementations of the interface from different suppliers are fully compatible at the physical level.
There is DigRF version v1.12 for usage in GSM/EDGE handsets, which was specified in 2004. DigRF v3.09 from the year 2006 with its 312 Mbit/s can additionally handleUMTS. The present DigRF v4 draft offers Gbit/s bandwidth for LTE and WiMax.
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https://en.wikipedia.org/wiki/DigRF_V3
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TheGlobal mobile Suppliers Association(GSA) is a not-for-profit industry organisation representing suppliers in the mobile communication industry.
GSA actively promotes3GPPtechnology such as3G;4G;5G.
GSA is a market representation partner in 3GPP and co-operates with organisations including COAI,ETSI,GSMA, ICU,ITU,European Conference of Postal and Telecommunications Administrations(CEPT-ECC), other regional regulatory bodies and other industry associations.
The GSA Spectrum Group is a large industry advocacy team of more than 185 participants from GSA Executive Member companies formed into 7 regional and country teams and other focused groups. GSA actively cooperates on spectrum related promotion with theGSM Association(GSMA), another organization with similar stated goals representing themobile network operatorcommunity. GSA is also an Associate Member of APT (Asia region), ATU (Africa) and CITEL (LatAm & USA/Canada).
The GSA analyser for mobile broadband data (GAMBoD) is a search and analysis tool developed by GSA to enable searches of mobile devices and new global data on mobile broadband networks, technologies and spectrum (NTS), mobile chipsets, Mobile Operators, Fixed Wireless devices, and Private Mobile Networks. The Devices database can be searched by supplier, form factor, features, peakdownlinkanduplinkspeeds, and operating frequency. The NTS database can be searched by mobile broadband (MBB) technology, feature, UE category, downlink speed, spectrum bands used and can be segmented by region.
In 2021 GSA established the4G-5G Fixed Wireless Access Forumto promote this segment of the mobile industry.[1]The forum has over 50 Members and Observers and produces ecosystem reports and bi-annual plenaries to showcase Fixed Wireless (FWA) deployments.
The Private Mobile Networks (PMN) Special Interest Group (SIG) was established in 2022 to track and report on deployments of non-public mobile networks, in enterprises and industries.[2]To join either of the above groups, companies can contact GSA atgsacom.com
GSA produces around 140 industry reports, white-papers, presentations, charts and industry snapshots each year based on the data from its GAMBoD databases. Many reports are free to download once registered and logged into the web site. More detailed reports are available for Members and Associates.
Areas of research include:
Executive Members
Members
Associates - ~85 including
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https://en.wikipedia.org/wiki/Global_mobile_Suppliers_Association
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Internet accessis a facility or service that provides connectivity for a computer, acomputer network, or other network device to theInternet, and for individuals or organizations to access or use applications such asemailand theWorld Wide Web. Internet access is offered for sale by an international hierarchy ofInternet service providers(ISPs) using various networking technologies. At the retail level, many organizations, including municipal entities, also provide cost-free access to the general public. Types of connections range fromfixed-linecable (such asDSLandfiber optic) tomobile(viacellular) andsatellite.[1]
The availability of Internet access to the general public began with the commercialization of the early Internet in the early 1990s, and has grown with the availability of useful applications, such as the World Wide Web. In 1995, only0.04percent of the world's population had access, with well over half of those living in the United States[2]and consumer use was throughdial-up. By the first decade of the 21st century, many consumers in developed nations used fasterbroadbandtechnology. By 2014, 41 percent of the world's population had access,[3]broadband was almost ubiquitous worldwide, and global average connection speeds exceeded one megabit per second.[4]
TheInternetdeveloped from theARPANET, which was funded by theUS governmentto support projects within the government, at universities and research laboratories in the US, but grew over time to include most of the world's large universities and the research arms of many technology companies.[5][6][7]Use by a wider audience only came in 1995 when restrictions on the use of the Internet to carry commercial traffic were lifted.[8]
In the early to mid-1980s, most Internet access was frompersonal computersandworkstationsdirectly connected tolocal area networks(LANs) or fromdial-up connectionsusingmodemsand analogtelephone lines. LANs typically operated at 10 Mbit/s while modem data-rates grew from 1200 bit/s in the early 1980s to 56 kbit/s by the late 1990s. Initially, dial-up connections were made fromterminalsor computers runningterminal-emulation softwaretoterminal serverson LANs. These dial-up connections did not support end-to-end use of the Internet protocols and only provided terminal-to-host connections. The introduction ofnetwork access serverssupporting theSerial Line Internet Protocol(SLIP) and later thepoint-to-point protocol(PPP) extended the Internet protocols and made the full range of Internet services available to dial-up users; although slower, due to the lower data rates available using dial-up.
An important factor in the rapid rise of Internet access speed has been advances inMOSFET(MOS transistor) technology.[9]The MOSFET invented at Bell Labs between 1955 and 1960 followingFroschand Derick discoveries,[10][11][12][13][14][15]is the building block of the Internettelecommunications networks.[16][17]Thelaser, originally demonstrated byCharles H. TownesandArthur Leonard Schawlowin 1960, was adopted for MOSlight-wavesystems around 1980, which led to exponential growth ofInternet bandwidth. ContinuousMOSFET scalinghas since led to online bandwidth doubling every 18 months (Edholm's law, which is related toMoore's law), with the bandwidths of telecommunications networks rising frombits per secondtoterabits per second.[9]
Broadband Internet access, often shortened to just broadband, is simply defined as "Internet access that is always on, and faster than the traditional dial-up access"[18][19]and so covers a wide range of technologies. The core of these broadband Internet technologies arecomplementary MOS(CMOS)digital circuits,[20][21]the speed capabilities of which were extended with innovative design techniques.[21]Broadband connections are typically made using a computer's built inEthernetnetworking capabilities, or by using aNICexpansion card.
Most broadband services provide a continuous "always on" connection; there is no dial-in process required, and it does not interfere with voice use of phone lines.[22]Broadband provides improved access to Internet services such as:
In the 1990s, theNational Information Infrastructureinitiative in the U.S. made broadband Internet access a public policy issue.[23]In 2000, most Internet access to homes was provided using dial-up, while many businesses and schools were using broadband connections. In 2000 there were just under 150 million dial-up subscriptions in the 34 OECD countries[24]and fewer than 20 million broadband subscriptions. By 2004, broadband had grown and dial-up had declined so that the number of subscriptions were roughly equal at 130 million each. In 2010, in the OECD countries, over 90% of the Internet access subscriptions used broadband, broadband had grown to more than 300 million subscriptions, and dial-up subscriptions had declined to fewer than 30 million.[25]
The broadband technologies in widest use are ofdigital subscriber line(DSL),ADSL, andcable Internet access. Newer technologies includeVDSLandoptical fiberextended closer to the subscriber in both telephone and cable plants.Fiber-optic communication, while only recently being used inpremises and to the curbschemes, has played a crucial role in enabling broadband Internet access by making transmission of information at very high data rates over longer distances much more cost-effective than copper wire technology.
In areas not served by ADSL or cable, some community organizations and local governments are installingWi-Finetworks. Wireless, satellite, and microwave Internet are often used in rural, undeveloped, or other hard to serve areas where wired Internet is not readily available.
Newer technologies being deployed for fixed (stationary) andmobile broadbandaccess includeWiMAX,LTE, andfixed wireless.
Starting in roughly 2006, mobile broadband access is increasingly available at the consumer level using "3G" and "4G" technologies such asHSPA,EV-DO,HSPA+, andLTE.
In addition to access from home, school, and the workplace Internet access may be available frompublic placessuch aslibrariesandInternet cafés, where computers with Internet connections are available. Some libraries provide stations for physically connecting users'laptopsto LANs.
Wireless Internet access points are available in public places such as airport halls, in some cases just for brief use while standing. Some access points may also provide coin-operated computers. Various terms are used, such as "publicInternet kiosk", "public access terminal", and "Webpayphone". Many hotels also have public terminals, usually fee based.
Coffee shops, shopping malls, and other venues increasingly offer wireless access to computer networks, referred to ashotspots, for users who bring their own wireless-enabled devices such as alaptoporPDA. These services may be free to all, free to customers only, or fee-based. A Wi-Fi hotspot need not be limited to a confined location since multiple ones combined can cover a whole campus or park, or even an entire city can be enabled.
Additionally, mobile broadband access allowssmartphonesand other digital devices to connect to the Internet from any location from which amobile phonecall can be made, subject to the capabilities of that mobile network.
The bit rates for dial-upmodemsrange from as little as 110 bit/s in the late 1950s, to a maximum of from 33 to 64 kbit/s (V.90andV.92) in the late 1990s. Dial-up connections generally require the dedicated use of a telephone line. Data compression can boost the effective bit rate for a dial-up modem connection from 220 (V.42bis) to 320 (V.44) kbit/s.[26]However, the effectiveness of data compression is quite variable, depending on the type of data being sent, the condition of the telephone line, and a number of other factors. In reality, the overall data rate rarely exceeds 150 kbit/s.[27]
Broadband technologies supply considerably higher bit rates than dial-up, generally without disrupting regular telephone use. Various minimum data rates and maximum latencies have been used in definitions of broadband, ranging from 64 kbit/s up to 4.0 Mbit/s.[28]In 1988 theCCITTstandards body defined "broadband service" as requiring transmission channels capable of supportingbit ratesgreater than theprimary ratewhich ranged from about 1.5 to 2 Mbit/s.[29]A 2006Organisation for Economic Co-operation and Development(OECD) report defined broadband as having downloaddata transfer ratesequal to or faster than 256 kbit/s.[30]And in 2015 the U.S.Federal Communications Commission(FCC) defined "Basic Broadband" as data transmission speeds of at least 25 Mbit/s downstream (from the Internet to the user'scomputer) and 3 Mbit/s upstream (from the user's computer to the Internet).[31]The trend is to raise the threshold of the broadband definition as higher data rate services become available.[32]
The higher data rate dial-up modems and many broadband services are "asymmetric"—supporting much higher data rates for download (toward the user) than for upload (toward the Internet).
Data rates, including those given in this article, are usually defined and advertised in terms of the maximum or peak download rate. In practice, these maximum data rates are not always reliably available to the customer.[33]Actual end-to-end data rates can be lower due to a number of factors.[34]In late June 2016, internet connection speeds averaged about 6 Mbit/s globally.[35]Physical link quality can vary with distance and for wireless access with terrain, weather, building construction, antenna placement, and interference from other radio sources. Network bottlenecks may exist at points anywhere on the path from the end-user to the remote server or service being used and not just on the first or last link providing Internet access to the end-user.
Users may share access over a common network infrastructure. Since most users do not use their full connection capacity all of the time, this aggregation strategy (known ascontended service) usually works well, and users can burst to their full data rate at least for brief periods. However,peer-to-peer(P2P)file sharingand high-quality streaming video can require high data-rates for extended periods, which violates these assumptions and can cause a service to become oversubscribed, resulting in congestion and poor performance. The TCP protocol includes flow-control mechanisms that automatically throttle back on the bandwidth being used during periods ofnetwork congestion. This is fair in the sense that all users who experience congestion receive less bandwidth, but it can be frustrating for customers and a major problem for ISPs. In some cases, the amount of bandwidth actually available may fall below the threshold required to support a particular service such as video conferencing or streaming live video–effectively making the service unavailable.
When traffic is particularly heavy, an ISP can deliberately throttle back the bandwidth available to classes of users or for particular services. This is known astraffic shapingand careful use can ensure a betterquality of servicefor time critical services even on extremely busy networks. However, overuse can lead to concerns about fairness andnetwork neutralityor even charges ofcensorship, when some types of traffic are severely or completely blocked.
An Internet blackout or outage can be caused by local signaling interruptions. Disruptions ofsubmarine communications cablesmay cause blackouts or slowdowns to large areas, such as in the2008 submarine cable disruption. Less-developed countries are more vulnerable due to a small number of high-capacity links. Land cables are also vulnerable, as in 2011 when a woman digging for scrap metal severed most connectivity for the nation of Armenia.[36]Internet blackouts affecting almost entire countries can be achieved by governments as a form ofInternet censorship, as in the blockage of theInternet in Egypt, whereby approximately 93%[37]of networks were without access in 2011 in an attempt to stop mobilization foranti-government protests.[38]
On April 25, 1997, due to a combination of human error and a software bug, an incorrect routing table at MAI Network Service (a VirginiaInternet service provider) propagated across backbone routers and caused major disruption to Internet traffic for a few hours.[39]
When the Internet is accessed using a modem,digital datais converted toanalogfor transmission over analog networks such as thetelephoneandcablenetworks.[22]A computer or other device accessing the Internet would either be connected directly to a modem that communicates with anInternet service provider(ISP) or the modem's Internet connection would be shared via a LAN which provides access in a limited area such as a home, school, computer laboratory, or office building.
Although a connection to a LAN may provide very high data-rates within the LAN, actual Internet access speed is limited by the upstream link to the ISP. LANs may be wired or wireless.Ethernet over twisted paircabling and Wi-Fi are the two most common technologies used to build LANs today, butARCNET,Token Ring,LocalTalk,FDDI, and other technologies were used in the past.
Ethernet is the name of theIEEE 802.3standard for physical LAN communication[40]and Wi-Fi is a trade name for awireless local area network(WLAN) that uses one of theIEEE 802.11standards.[41]Ethernet cables are interconnected via switches & routers. Wi-Fi networks are built using one or more wireless antenna calledaccess points.
Many "modems" (cable modems,DSL gatewaysorOptical Network Terminals(ONTs)) provide the additional functionality to host a LAN so most Internet access today is through a LAN such as that created by a WiFi router connected to a modem or a combo modem router,[citation needed]often a very small LAN with just one or two devices attached. And while LANs are an important form of Internet access, this raises the question of how and at what data rate the LAN itself is connected to the rest of the global Internet. The technologies described below are used to make these connections, or in other words, how customers' modems (Customer-premises equipment) are most often connected to internet service providers (ISPs).
Dial-up Internet access uses a modem and a phone call placed over thepublic switched telephone network(PSTN) to connect to a pool of modems operated by an ISP. The modem converts a computer's digital signal into an analog signal that travels over a phone line'slocal loopuntil it reaches a telephone company's switching facilities or central office (CO) where it is switched to another phone line that connects to another modem at the remote end of the connection.[42]
Operating on a single channel, a dial-up connection monopolizes the phone line and is one of the slowest methods of accessing the Internet. Dial-up is often the only form of Internet access available in rural areas as it requires no new infrastructure beyond the already existing telephone network, to connect to the Internet. Typically, dial-up connections do not exceed a speed of56kbit/s, as they are primarily made using modems that operate at a maximum data rate of 56 kbit/s downstream (towards the end user) and 34 or 48 kbit/s upstream (toward the global Internet).[22]
Multilinkdial-up provides increased bandwidth bychannel bondingmultiple dial-up connections and accessing them as a single data channel.[43]It requires two or more modems, phone lines, and dial-up accounts, as well as an ISP that supports multilinking – and of course any line and data charges are also doubled. Thisinverse multiplexingoption was briefly popular with some high-end users before ISDN, DSL and other technologies became available.Diamondand other vendors created special modems to support multilinking.[44]
The termbroadbandincludes a broad range of technologies, all of which provide higher data rate access to the Internet. The following technologies use wires or cables in contrast to wireless broadband described later.
Integrated Services Digital Network(ISDN) is a switched telephone service capable of transporting voice and digital data, and is one of the oldest Internet access methods. ISDN has been used for voice, video conferencing, and broadband data applications. ISDN was very popular in Europe, but less common in North America. Its use peaked in the late 1990s before the availability of DSL and cable modem technologies.[45]
Basic rate ISDN, known as ISDN-BRI, has two 64 kbit/s "bearer" or "B" channels. These channels can be used separately for voice or data calls or bonded together to provide a 128 kbit/s service. Multiple ISDN-BRI lines can be bonded together to provide data rates above 128 kbit/s. Primary rate ISDN, known as ISDN-PRI, has 23 bearer channels (64 kbit/s each) for a combined data rate of 1.5 Mbit/s (US standard). An ISDN E1 (European standard) line has 30 bearer channels and a combined data rate of 1.9 Mbit/s. ISDN has been replaced by DSL technology,[46]and it required special telephone switches at the service provider.[47]
Leased linesare dedicated lines used primarily by ISPs, business, and other large enterprises to connect LANs and campus networks to the Internet using the existing infrastructure of thepublic telephone networkor other providers. Delivered using wire,optical fiber, andradio, leased lines are used to provide Internet access directly as well as the building blocks from which several other forms of Internet access are created.[48]
T-carriertechnology[49]dates to 1957 and provides data rates that range from 56 and64 kbit/s(DS0) to1.5 Mbit/s(DS1or T1), to45 Mbit/s(DS3or T3).[50]A T1 line carries 24 voice or data channels (24 DS0s), so customers may use some channels for data and others for voice traffic or use all 24 channels for clear channel data. A DS3 (T3) line carries 28 DS1 (T1) channels. Fractional T1 lines are also available in multiples of a DS0 to provide data rates between 56 and1500 kbit/s. T-carrier lines require special termination equipment such asData service units[51][52][53]that may be separate from or integrated into a router or switch and which may be purchased or leased from an ISP.[54]In Japan the equivalent standard is J1/J3. In Europe, a slightly different standard,E-carrier, provides 32 user channels (64 kbit/s) on an E1 (2.0 Mbit/s) and 512 user channels or 16 E1s on an E3 (34.4 Mbit/s).
Synchronous Optical Networking(SONET, in the U.S. and Canada) and Synchronous Digital Hierarchy (SDH, in the rest of the world)[49]are the standard multiplexing protocols used to carry high-data-rate digital bit-streams over optical fiber usinglasersor highlycoherent lightfromlight-emitting diodes(LEDs). At lower transmission rates data can also be transferred via an electrical interface. The basic unit of framing is anOC-3c(optical) orSTS-3c(electrical) which carries155.520 Mbit/s. Thus an OC-3c will carry threeOC-1(51.84 Mbit/s) payloads each of which has enough capacity to include a full DS3. Higher data rates are delivered in OC-3c multiples of four providingOC-12c(622.080 Mbit/s),OC-48c(2.488 Gbit/s),OC-192c(9.953 Gbit/s), andOC-768c(39.813 Gbit/s). The "c" at the end of the OC labels stands for "concatenated" and indicates a single data stream rather than several multiplexed data streams.[48]Optical transport network(OTN) may be used instead of SONET[55]for higher data transmission speeds of up to400 Gbit/sper OTN channel.
The1,10,40, and 100 Gigabit EthernetIEEE standards (802.3)allow digital data to be delivered over copper wiring at distances to 100 m and over optical fiber at distances to40 km.[56]
Cable Internet provides access using acable modemonhybrid fiber coaxial(HFC) wiring originally developed to carry television signals. Either fiber-optic or coaxial copper cable may connect a node to a customer's location at a connection known as a cable drop. Using acable modem termination system, all nodes for cable subscribers in a neighborhood connect to a cable company's central office, known as the "head end." The cable company then connects to the Internet using a variety of means – usually fiber optic cable or digital satellite and microwave transmissions.[57]Like DSL, broadband cable provides a continuous connection with an ISP.
Downstream, the direction toward the user, bit rates can be as much as 1000Mbit/sin some countries, with the use ofDOCSIS3.1. Upstream traffic, originating at the user, ranges from 384 kbit/s to more than 50 Mbit/s. DOCSIS 4.0 promises up to10 Gbit/sdownstream and6 Gbit/supstream, however this technology is yet to have been implemented in real-world usage. Broadband cable access tends to service fewer business customers because existing television cable networks tend to service residential buildings; commercial buildings do not always include wiring for coaxial cable networks.[58]In addition, because broadband cable subscribers share the same local line, communications may be intercepted by neighboring subscribers. Cable networks regularly provide encryption schemes for data traveling to and from customers, but these schemes may be thwarted.[57]
Digital subscriber line(DSL) service provides a connection to the Internet through the telephone network. Unlike dial-up, DSL can operate using a single phone line without preventing normal use of the telephone line for voice phone calls. DSL uses the high frequencies, while the low (audible) frequencies of the line are left free forregular telephonecommunication.[22]These frequency bands are subsequently separated by filters installed at the customer's premises.
DSL originally stood for "digital subscriber loop". In telecommunications marketing, the term digital subscriber line is widely understood to meanasymmetric digital subscriber line(ADSL), the most commonly installed variety of DSL. The data throughput of consumer DSL services typically ranges from 256 kbit/s to 20 Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (i.e., in the direction to the service provider) is lower than that in the downstream direction (i.e. to the customer), hence the designation of asymmetric.[59]With asymmetric digital subscriber line(SDSL), the downstream and upstream data rates are equal.[60]
Very-high-bit-rate digital subscriber line(VDSL or VHDSL, ITU G.993.1)[61]is a digital subscriber line (DSL) standard approved in 2001 that provides data rates up to 52 Mbit/s downstream and 16 Mbit/s upstream over copper wires[62]and up to 85 Mbit/s down- and upstream on coaxial cable.[63]VDSL is capable of supporting applications such as high-definition television, as well as telephone services (voice over IP) and general Internet access, over a single physical connection.
VDSL2(ITU-TG.993.2) is a second-generation version and an enhancement of VDSL.[64]Approved in February 2006, it is able to provide data rates exceeding 100 Mbit/s simultaneously in both the upstream and downstream directions. However, the maximum data rate is achieved at a range of about 300 meters and performance degrades as distance and loopattenuationincreases.
DSL Rings(DSLR) or Bonded DSL Rings is a ring topology that uses DSL technology over existing copper telephone wires to provide data rates of up to 400 Mbit/s.[65]
Fiber-to-the-home(FTTH) is one member of the Fiber-to-the-x (FTTx) family that includes Fiber-to-the-building or basement (FTTB), Fiber-to-the-premises (FTTP), Fiber-to-the-desk (FTTD), Fiber-to-the-curb (FTTC), and Fiber-to-the-node (FTTN).[66]These methods all bring data closer to the end user on optical fibers. The differences between the methods have mostly to do with just how close to the end user the delivery on fiber comes. All of these delivery methods are similar in function and architecture tohybrid fiber-coaxial(HFC) systems used to provide cable Internet access. Fiber internet connections to customers are either AON (Active optical network) or more commonly PON (Passive optical network). Examples of fiber optic internet access standards areG.984(GPON, G-PON) and10G-PON(XG-PON). ISPs may instead useMetro Ethernetas a replacement for T1 and Frame Relay lines[67]for corporate and institutional customers,[68]or offer carrier-grade Ethernet.[69]
The use ofoptical fiberoffers much higher data rates over relatively longer distances. Most high-capacity Internet and cable television backbones already use fiber optic technology, with data switched to other technologies (DSL, cable, LTE) for final delivery to customers.[70]Fiber optic is immune to electromagnetic interference.[71]
In 2010, Australia began rolling out itsNational Broadband Networkacross the country using fiber-optic cables to 93 percent of Australian homes, schools, and businesses.[72]The project was abandoned by the subsequent LNP government, in favor of a hybrid FTTN design, which turned out to be more expensive and introduced delays. Similar efforts are underway in Italy, Canada, India, and many other countries (see Fiber to the premises by country).[73][74][75][76]
Power-line Internet, also known asBroadband over power lines(BPL), carries Internet data on a conductor that is also used forelectric power transmission.[77]Because of the extensive power line infrastructure already in place, this technology can provide people in rural and low population areas access to the Internet with little cost in terms of new transmission equipment, cables, or wires. Data rates are asymmetric and generally range from 256 kbit/s to 2.7 Mbit/s.[78]
Because these systems use parts of the radio spectrum allocated to other over-the-air communication services, interference between the services is a limiting factor in the introduction of power-line Internet systems. TheIEEE P1901standard specifies that all power-line protocols must detect existing usage and avoid interfering with it.[78]
Power-line Internet has developed faster in Europe than in the U.S. due to a historical difference in power system design philosophies. Data signals cannot pass through the step-down transformers used and so a repeater must be installed on each transformer.[78]In the U.S. a transformer serves a small cluster of from one to a few houses. In Europe, it is more common for a somewhat larger transformer to service larger clusters of from 10 to 100 houses. Thus a typical U.S. city requires an order of magnitude more repeaters than a comparable European city.[79]
Asynchronous Transfer Mode(ATM) andFrame Relayare wide-area networking standards that can be used to provide Internet access directly[50]or as building blocks of other access technologies. For example, many DSL implementations use an ATM layer over the low-level bitstream layer to enable a number of different technologies over the same link. Customer LANs are typically connected to an ATM switch or a Frame Relay node using leased lines at a wide range of data rates.[80][81]
While still widely used, with the advent of Ethernet over optical fiber,MPLS,VPNsand broadband services such as cable modem and DSL, ATM and Frame Relay no longer play the prominent role they once did.
Wireless broadbandis used to provide both fixed and mobile Internet access with the following technologies.
Satellite Internet accessprovides fixed, portable, and mobile Internet access.[82]Data rates range from 2 kbit/s to 1 Gbit/s downstream and from 2 kbit/s to 10 Mbit/s upstream. In the northern hemisphere, satellite antenna dishes require a clear line of sight to the southern sky, due to the equatorial position of all geostationary satellites. In the southern hemisphere, this situation is reversed, and dishes are pointed north.[83][84]Service can be adversely affected by moisture, rain, and snow (known as rain fade).[83][84][85]The system requires a carefully aimed directional antenna.[84]
Satellites in geostationary Earth orbit (GEO) operate in a fixed position 35,786 km (22,236 mi) above the Earth's equator. At the speed of light (about 300,000 km/s or 186,000 miles per second), it takes a quarter of a second for a radio signal to travel from the Earth to the satellite and back. When other switching and routing delays are added and the delays are doubled to allow for a full round-trip transmission, the total delay can be 0.75 to 1.25 seconds. This latency is large when compared to other forms of Internet access with typical latencies that range from 0.015 to 0.2 seconds. Long latencies negatively affect some applications that require real-time response, particularly online games,voice over IP, and remote control devices.[86][87]TCP tuningandTCP accelerationtechniques can mitigate some of these problems. GEO satellites do not cover the Earth's polar regions.[83]HughesNet,Exede,AT&TandDish Networkhave GEO systems.[88][89][90][91]
Satellite internet constellationsinlow Earth orbit(LEO, below 2,000 km or 1,243 miles) andmedium Earth orbit(MEO, between 2,000 and 35,786 km or 1,243 and 22,236 miles) operate at lower altitudes, and their satellites are not fixed in their position above the Earth. Because they operate at a lower altitude, more satellites andlaunch vehiclesare needed for worldwide coverage. This makes the initial required investment very large which initially caused OneWeb and Iridium to declare bankruptcy. However, their lower altitudes allow lower latencies and higher speeds which make real-time interactive Internet applications more feasible. LEO systems includeGlobalstar,Starlink,OneWebandIridium. TheO3bconstellation is a medium Earth-orbit system with a latency of 125 ms. COMMStellation™ is a LEO system, scheduled for launch in 2015,[needs update]that is expected to have a latency of just 7 ms.
Mobile broadbandis the marketing term for wireless Internet access delivered through mobile phone towers (cellular networks) to computers,mobile phones(called "cell phones" in North America and South Africa, and "hand phones" in Asia), and other digital devices usingportable modems. Some mobile services allow more than one device to be connected to the Internet using a single cellular connection using a process calledtethering. The modem may be built into laptop computers, tablets, mobile phones, and other devices, added to some devices usingPC cards,USB modems, andUSB sticksordongles, or separatewireless modemscan be used.[92]
New mobile phone technology and infrastructure is introduced periodically and generally involves a change in the fundamental nature of the service, non-backwards-compatible transmission technology, higher peak data rates, new frequency bands, wider channel frequency bandwidth in Hertz becomes available. These transitions are referred to as generations. The first mobile data services became available during the second generation (2G).
The download (to the user) and upload (to the Internet) data rates given above are peak or maximum rates and end users will typically experience lower data rates.
WiMAXwas originally developed to deliver fixed wireless service with wireless mobility added in 2005. CDPD, CDMA2000 EV-DO, and MBWA are no longer being actively developed.
In 2011, 90% of the world's population lived in areas with 2G coverage, while 45% lived in areas with 2G and 3G coverage.[93]
5Gwas designed to be faster and have lower latency than its predecessor, 4G. It can be used for mobile broadband in smartphones or separate modems that emit WiFi or can be connected through USB to a computer, or for fixed wireless.
Fixed wirelessinternet connections that do not use a satellite nor are designed to support moving equipment such as smartphones due to the use of, for example,customer premises equipmentsuch as antennas that can't be moved over a significant geographical area without losing the signal from the ISP, unlike smartphones. Microwave wireless broadband or5Gmay be used for fixed wireless.
Worldwide Interoperability for Microwave Access (WiMAX) is a set of interoperable implementations of theIEEE 802.16family of wireless-network standards certified by theWiMAX Forum. It enables "the delivery oflast milewireless broadband access as an alternative to cable and DSL".[94]The original IEEE 802.16 standard, now called "Fixed WiMAX", was published in 2001 and provided 30 to 40 megabit-per-second data rates.[95]Mobility support was added in 2005. A 2011 update provides data rates up to 1 Gbit/s for fixed stations. WiMax offers a metropolitan area network with a signal radius of about 50 km (30 miles), far surpassing the 30-metre (100-foot) wireless range of a conventional Wi-Fi LAN. WiMAX signals also penetrate building walls much more effectively than Wi-Fi. WiMAX is most often used as a fixed wireless standard.
Wireless Internet service providers(WISPs) operate independently ofmobile phone operators. WISPs typically employ low-cost IEEE 802.11 Wi-Fi radio systems to link up remote locations over great distances (Long-range Wi-Fi), but may use other higher-power radio communications systems as well, such as microwave and WiMAX.
Traditional 802.11a/b/g/n/ac is an unlicensed omnidirectional service designed to span between 100 and 150 m (300 to 500 ft). By focusing the radio signal using adirectional antenna(where allowed by regulations), 802.11 can operate reliably over a distance of many km(miles), although the technology's line-of-sight requirements hamper connectivity in areas with hilly or heavily foliated terrain. In addition, compared to hard-wired connectivity, there are security risks (unless robust security protocols are enabled); data rates are usually slower (2 to 50 times slower); and the network can be less stable, due to interference from other wireless devices and networks, weather and line-of-sight problems.[96]
With the increasing popularity of unrelated consumer devices operating on the same 2.4 GHz band, many providers have migrated to the5GHz ISM band. If the service provider holds the necessary spectrum license, it could also reconfigure various brands of off the shelf Wi-Fi hardware to operate on its own band instead of the crowded unlicensed ones. Using higher frequencies carries various advantages:
Proprietary technologies likeMotorola Canopy& Expedience can be used by a WISP to offer wireless access to rural and other markets that are hard to reach using Wi-Fi or WiMAX. There are a number of companies that provide this service.[97]
Local Multipoint Distribution Service(LMDS) is a broadband wireless access technology that uses microwave signals operating between 26 GHz and 29 GHz.[98]Originally designed for digital television transmission (DTV), it is conceived as a fixed wireless, point-to-multipoint technology for utilization in the last mile. Data rates range from 64 kbit/s to 155 Mbit/s.[99]Distance is typically limited to about 1.5 miles (2.4 km), but links of up to 5 miles (8 km) from the base station are possible in some circumstances.[100]
LMDS has been surpassed in both technological and commercial potential by the LTE and WiMAX standards.
In some regions, notably in rural areas, the length of the copper lines makes it difficult for network operators to provide high-bandwidth services. One alternative is to combine a fixed-access network, typicallyXDSL, with a wireless network, typically LTE. TheBroadband Forumhas standardized an architecture for such Hybrid Access Networks.
Deploying multiple adjacent Wi-Fi access points is sometimes used to createcity-wide wireless networks.[101]It is usually ordered by the local municipality from commercial WISPs.
Grassrootsefforts have also led towireless community networkswidely deployed in numerous countries, both developing and developed ones. Rural wireless-ISP installations are typically not commercial in nature and are instead a patchwork of systems built up by hobbyists mounting antennas onradio masts and towers, agriculturalstorage silos, very tall trees, or whatever other tall objects are available.
Where radio spectrum regulation is not community-friendly, the channels are crowded or when equipment can not be afforded by local residents,free-space optical communicationcan also be deployed in a similar manner for point to point transmission in air (rather than in fiber optic cable).
Packet radio connects computers or whole networks operated by radio amateurs with the option to access the Internet. Note that as per the regulatory rules outlined in the HAM license, Internet access and email should be strictly related to the activities of hardware amateurs.
The term, atongue-in-cheekplay onnet(work)as inInternetorEthernet, refers to the wearing ofsneakersas the transport mechanism for the data.
For those who do not have access to or can not afford broadband at home, downloading large files and disseminating information is done by transmission through workplace or library networks, taken home and shared with neighbors by sneakernet. The CubanEl Paquete Semanalis an organized example of this.
There are various decentralized,delay tolerantpeer to peer applications which aim to fully automate this using any available interface, including both wireless (Bluetooth, Wi-Fi mesh, P2P or hotspots) and physically connected ones (USB storage, Ethernet, etc.).
Sneakernets may also be used in tandem with computer network data transfer to increase data security or overall throughput for big data use cases. Innovation continues in the area to this day; for example, AWS has recently announced Snowball, and bulk data processing is also done in a similar fashion by many research institutes and government agencies.
Internet access is limited by the relation between pricing and available resources to spend. Regarding the latter, it is estimated that 40% of the world's population has less than US$20 per year available to spend oninformation and communications technology(ICT).[103]In Mexico, the poorest 30% of the society spend an estimated US$35 per year (US$3 per month) and in Brazil, the poorest 22% of the population merely has US$9 per year to spend on ICT (US$0.75 per month). From Latin America, it is known that the borderline between ICT as anecessity goodand ICT as aluxury goodis roughly around the "magical number" of US$10 per person per month, or US$120 per year.[103]This is the amount of ICT spending people esteem to be a basic necessity. Current Internet access prices exceed the available resources by large in many countries.
Dial-up users pay the costs for making local or long-distance phone calls, usually pay a monthly subscription fee, and may be subject to additional per minute or traffic based charges, and connect time limits by their ISP. Though less common today than in the past, some dial-up access is offered for "free" in return for watchingbanner adsas part of the dial-up service.NetZero,BlueLight,Juno,Freenet (NZ), andFree-netsare examples of services providing free access. SomeWireless community networkscontinue the tradition of providing free Internet access.
Fixed broadband Internet access is often sold under an "unlimited" orflat ratepricing model, with price determined by the maximum data rate chosen by the customer, rather than a per minute or traffic based charge. Per minute and traffic based charges and traffic caps are common for mobile broadband Internet access.
Internet services likeFacebook,WikipediaandGooglehave built special programs to partner withmobile network operators(MNO) to introducezero-ratingthe cost for their data volumes as a means to provide their service more broadly into developing markets.[104]
With increased consumer demand for streaming content such as video on demand andpeer-to-peer file sharing, demand for bandwidth has increased rapidly and for some ISPs the flat rate pricing model may become unsustainable. However, withfixed costsestimated to represent 80–90% of the cost of providing broadband service, the marginal cost to carry additional traffic is low. Most ISPs do not disclose their costs, but the cost to transmit a gigabyte of data in 2011 was estimated to be about $0.03.[105]
Some ISPs estimate that a small number of their users consume a disproportionate portion of the total bandwidth. In response some ISPs are considering, are experimenting with, or have implemented combinations of traffic based pricing, time of day or "peak" and "off peak" pricing, and bandwidth or traffic caps. Others claim that because the marginal cost of extra bandwidth is very small with 80 to 90 percent of the costs fixed regardless of usage level, that such steps are unnecessary or motivated by concerns other than the cost of delivering bandwidth to the end user.[106][107][108]
In Canada,Rogers Hi-Speed InternetandBell Canadahave imposedbandwidth caps.[106]In 2008Time Warnerbegan experimenting with usage-based pricing in Beaumont, Texas.[109]In 2009 an effort by Time Warner to expand usage-based pricing into theRochester, New Yorkarea met with public resistance, however, and was abandoned.[110]On August 1, 2012, in Nashville, Tennessee and on October 1, 2012, in Tucson, Arizona Comcast began tests that impose data caps on area residents. In Nashville exceeding the 300 Gbyte cap mandates a temporary purchase of 50 Gbytes of additional data.[111]
Despite its tremendous growth, Internet access is not distributed equally within or between countries.[116][117]Thedigital dividerefers to "the gap between people with effective access toinformation and communications technology(ICT), and those with very limited or no access". The gap between people with Internet access and those without is one of many aspects of the digital divide.[118]Whether someone has access to the Internet can depend greatly on financial status, geographical location as well as government policies. "Low-income, rural, and minority populations have received special scrutiny as the technological 'have-nots'."[119]
Government policies play a tremendous role in bringing Internet access to or limiting access for underserved groups, regions, and countries. For example, in Pakistan, which is pursuing an aggressive IT policy aimed at boosting its drive for economic modernization, the number of Internet users grew from 133,900 (0.1% of the population) in 2000 to 31 million (17.6% of the population) in 2011.[120]InNorth Koreathere is relatively little access to the Internet due to the governments' fear of political instability that might accompany the benefits of access to the global Internet.[121]TheU.S. trade embargois a barrier limiting Internet access inCuba.[122]
Access to computers is a dominant factor in determining the level of Internet access. In 2011, in developing countries, 25% of households had a computer and 20% had Internet access, while in developed countries the figures were 74% of households had a computer and 71% had Internet access.[93]The majority of people in developing countries do not have Internet access.[123]About 4 billion people do not have Internet access.[124]When buying computers was legalized in Cuba in 2007, the private ownership of computers soared (there were 630,000 computers available on the island in 2008, a 23% increase over 2007).[125][126]
Internet access has changed the way in which many people think and has become an integral part of people's economic, political, and social lives. The United Nations has recognized that providing Internet access to more people in the world will allow them to take advantage of the "political, social, economic, educational, and career opportunities" available over the Internet.[117]Several of the 67 principles adopted at theWorld Summit on the Information Societyconvened by theUnited Nationsin Geneva in 2003, directly address the digital divide.[127]To promote economic development and a reduction of thedigital divide,national broadband planshave been and are being developed to increase the availability of affordable high-speed Internet access throughout the world. The Global Gateway, the EU's initiative to assist infrastructure development throughout the world, plans to raise €300 billion for connectivity projects, including those in the digital sector, between 2021 and 2027.[128][129]
Access to the Internet grew from an estimated 10 million people in 1993, to almost 40 million in 1995, to 670 million in 2002, and to 2.7 billion in 2013.[132]Withmarket saturation, growth in the number of Internet users is slowing in industrialized countries, but continues in Asia,[133]Africa, Latin America, theCaribbean, and the Middle East. Across Africa, an estimated 900 million people are still not connected to the internet; for those who are, connectivity fees remain generally expensive, and bandwidth is severely constrained in many locations.[134][135]The number of mobile customers in Africa, however, is expanding faster than everywhere else. Mobile financial services also allow for immediate payment of products and services.[136][137][138]
There were roughly 0.6 billion fixed broadband subscribers and almost 1.2 billion mobile broadband subscribers in 2011.[139]In developed countries people frequently use both fixed and mobile broadband networks. In developing countries mobile broadband is often the only access method available.[93]
Traditionally the divide has been measured in terms of the existing numbers of subscriptions and digital devices ("have and have-not of subscriptions"). Recent studies have measured the digital divide not in terms of technological devices, but in terms of the existing bandwidth per individual (in kbit/s per capita).[115][140]As shown in the Figure on the side, the digital divide in kbit/s is not monotonically decreasing, but re-opens up with each new innovation. For example, "the massive diffusion of narrow-band Internet and mobile phones during the late 1990s" increased digital inequality, as well as "the initial introduction of broadband DSL and cable modems during 2003–2004 increased levels of inequality".[140]This is because a new kind of connectivity is never introduced instantaneously and uniformly to society as a whole at once, but diffuses slowly through social networks. As shown by the Figure, during the mid-2000s, communication capacity was more unequally distributed than during the late 1980s, when only fixed-line phones existed. The most recent increase in digital equality stems from the massive diffusion of the latest digital innovations (i.e. fixed and mobile broadband infrastructures, e.g.3Gand fiber opticsFTTH).[141]As shown in the Figure, Internet access in terms of bandwidth is more unequally distributed in 2014 as it was in the mid-1990s.
For example, only 0.4% of the African population has a fixed-broadband subscription. The majority of internet users use it through mobile broadband.[134][135][142][143]
One of the great challenges for Internet access in general and for broadband access in particular is to provide service to potential customers in areas of lowpopulation density, such as to farmers, ranchers, and small towns. In cities where the population density is high, it is easier for a service provider to recover equipment costs, but each rural customer may require expensive equipment to get connected. While 66% of Americans had an Internet connection in 2010, that figure was only 50% in rural areas, according to the Pew Internet & American Life Project.[144]Virgin Mediaadvertised over 100 towns across the United Kingdom "fromCwmbrantoClydebank" that have access to their 100 Mbit/s service.[33]
Wireless Internet service providers(WISPs) are rapidly becoming a popular broadband option for rural areas.[145]The technology's line-of-sight requirements may hamper connectivity in some areas with hilly and heavily foliated terrain. However, the Tegola project, a successful pilot in remote Scotland, demonstrates that wireless can be a viable option.[146]
The CanadianBroadband for Rural Nova Scotia initiativepublic private partnershipis the first program in North America to guarantee access to "100% of civic addresses" in a region. It is based onMotorola Canopytechnology. As of November 2011, under 1000 households have reported access problems. Deployment of a new cell network by one Canopy provider (Eastlink) was expected to provide the alternative of 3G/4G service, possibly at a special unmetered rate, for areas harder to serve by Canopy.[147]
In New Zealand, a fund has been formed by the government to improve rural broadband,[148]and mobile phone coverage. Current proposals include: (a) extending fiber coverage and upgrading copper to support VDSL, (b) focusing on improving the coverage of cellphone technology, or (c) regional wireless.[149]
Several countries have startedHybrid Access Networksto provide faster Internet services in rural areas by enabling network operators to efficiently combine their XDSL and LTE networks.
The actions, statements, opinions, and recommendations outlined below have led to the suggestion that Internet access itself is or should become a civil or perhaps a human right.[150][151]
Several countries have adopted laws requiring the state to work to ensure that Internet access is broadly available or preventing the state from unreasonably restricting an individual'saccess to informationand the Internet:
In December 2003, theWorld Summit on the Information Society(WSIS) was convened under the auspice of theUnited Nations. After lengthy negotiations between governments, businesses and civil society representatives the WSIS Declaration of Principles was adopted reaffirming the importance of the Information Society to maintaining and strengtheninghuman rights:[127][158]
TheWSISDeclaration of Principles makes specific reference to the importance of the right tofreedom of expressionin the "Information Society" in stating:
A poll of 27,973 adults in 26 countries, including 14,306 Internet users,[159]conducted for theBBC World Servicebetween 30 November 2009 and 7 February 2010 found that almost four in five Internet users and non-users around the world felt that access to the Internet was a fundamental right.[160]50% strongly agreed, 29% somewhat agreed, 9% somewhat disagreed, 6% strongly disagreed, and 6% gave no opinion.[161]
The 88 recommendations made by theSpecial Rapporteuron the promotion and protection of the right to freedom of opinion and expression in a May 2011 report to theHuman Rights Councilof theUnited Nations General Assemblyinclude several that bear on the question of the right to Internet access:[162]
Network neutrality (also net neutrality, Internet neutrality, or net equality) is the principle that Internet service providers and governments should treat all data on the Internet equally, not discriminating or charging differentially by user, content, site, platform, application, type of attached equipment, or mode of communication.[163][164][165][166]Advocates of net neutrality have raised concerns about the ability of broadband providers to use theirlast mileinfrastructure to block Internet applications and content (e.g. websites, services, and protocols), and even to block out competitors.[167]Opponents claim net neutrality regulations would deter investment into improving broadband infrastructure and try to fix something that isn't broken.[168][169]In April 2017, a recent attempt to compromisenet neutrality in the United Statesis being considered by the newly appointed FCC chairman,Ajit Varadaraj Pai.[170]The vote on whether or not to abolish net neutrality was passed on December 14, 2017, and ended in a 3–2 split in favor of abolishing net neutrality.
Natural disasters disrupt internet access in profound ways. This is important—not only for telecommunication companies who own the networks and the businesses who use them, but for emergency crew and displaced citizens as well. The situation is worsened when hospitals or other buildings necessary for disaster response lose their connection. Knowledge gained from studying past internet disruptions by natural disasters could be put to use in planning or recovery. Additionally, because of both natural and man-made disasters, studies in network resiliency are now being conducted to prevent large-scale outages.[171]
One way natural disasters impact internet connection is by damaging end sub-networks (subnets), making them unreachable. A study on local networks afterHurricane Katrinafound that 26% of subnets within the storm coverage were unreachable.[172]At Hurricane Katrina's peak intensity, almost 35% of networks in Mississippi were without power, while around 14% of Louisiana's networks were disrupted.[173]Of those unreachable subnets, 73% were disrupted for four weeks or longer and 57% were at "network edges were important emergency organizations such as hospitals and government agencies are mostly located".[172]Extensive infrastructure damage and inaccessible areas were two explanations for the long delay in returning service.[172]The companyCiscohas revealed a Network Emergency Response Vehicle (NERV), a truck that makes portable communications possible for emergency responders despite traditional networks being disrupted.[174]
A second way natural disasters destroy internet connectivity is by severing submarine cables—fiber-optic cables placed on the ocean floor that provide international internet connection. Asequence of undersea earthquakescut six out of seven international cables connected toTaiwanand caused a tsunami that wiped out one of its cable and landing stations.[175][176]The impact slowed or disabled internet connection for five days within the Asia-Pacific region as well as between the region and the United States and Europe.[177]
With the rise in popularity ofcloud computing, concern has grown over access to cloud-hosted data in the event of a natural disaster.Amazon Web Services(AWS) has been in the news for major network outages in April 2011 and June 2012.[178][179]AWS, like other major cloud hosting companies, prepares for typical outages and large-scale natural disasters with backup power as well as backup data centers in other locations. AWS divides the globe into five regions and then splits each region into availability zones. A data center in one availability zone should be backed up by a data center in a different availability zone. Theoretically, a natural disaster would not affect more than one availability zone.[180]This theory plays out as long as human error is not added to the mix. The June 2012 major storm only disabled the primary data center, but human error disabled the secondary and tertiary backups, affecting companies such asNetflix,Pinterest,Reddit, andInstagram.[181][182]
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This is alist of interface bit rates, a measure ofinformation transfer rates, ordigital bandwidth capacity, at which digital interfaces in acomputerornetworkcan communicate over various kinds ofbusesandchannels. The distinction can be arbitrary between acomputer bus, often closer in space, and largertelecommunications networks. Many deviceinterfacesorprotocols(e.g., SATA, USB,SAS,PCIe) are used both inside many-device boxes, such as a PC, and one-device-boxes, such as ahard drive enclosure. Accordingly, this page lists both the internal ribbon and external communications cable standards together in one sortable table.
Most of the listed rates are theoretical maximumthroughputmeasures; in practice, theactual effective throughputis almost inevitably lower in proportion to the load from other devices (network/bus contention), physical or temporal distances, and otheroverheadindata link layerprotocols etc. The maximumgoodput(for example, the file transfer rate) may be even lower due to higher layer protocol overhead and data packet retransmissions caused by linenoiseorinterferencesuch ascrosstalk, or lost packets incongestedintermediate network nodes. All protocols lose something, and the more robust ones that deal resiliently with very many failure situations tend to lose more maximum throughput to get higher total long-term rates.
Device interfaces where one bus transfers data via another will be limited to the throughput of the slowest interface, at best. For instance,SATArevision 3.0 (6Gbit/s) controllers on one PCI Express 2.0 (5 Gbit/s) channel will be limited to the5 Gbit/srate and have to employ more channels to get around this problem. Early implementations of new protocols very often have this kind of problem. The physical phenomena on which the device relies (such as spinning platters in a hard drive) will also impose limits; for instance, no spinning platter shipping in 2009 saturates SATA revision 2.0 (3 Gbit/s), so moving from this3 Gbit/sinterface toUSB 3.0at4.8 Gbit/sfor one spinning drive will result in no increase in realized transfer rate.
Contention in a wireless or noisy spectrum, where the physical medium is entirely out of the control of those who specify the protocol, requires measures that also use up throughput. Wireless devices,BPL, andmodemsmay produce a higherline rateorgross bit rate, due toerror-correcting codesand otherphysical layeroverhead. It is extremely common for throughput to be far less than half of theoretical maximum, though the more recent technologies (notably BPL) employ preemptive spectrum analysis to avoid this and so have much more potential to reach actual gigabit rates in practice than prior modems.
Another factor reducing throughput is deliberate policy decisions made byInternet service providersthat are made for contractual, risk management, aggregation saturation, or marketing reasons. Examples arerate limiting,bandwidth throttling, and the assignment ofIP addressesto groups. These practices tend to minimize the throughput available to every user, but maximize the number of users that can be supported on one backbone.
Furthermore, chips are often not available in order to implement the fastest rates.AMD, for instance, does not support the 32-bitHyperTransportinterface on any CPU it has shipped as of the end of 2009. Additionally,WiMAXservice providers in the US typically support only up to4Mbit/sas of the end of 2009.
Choosing service providers or interfaces based on theoretical maxima is unwise, especially for commercial needs. A good example is large scale data centers, which should be more concerned with price per port to support the interface, wattage and heat considerations, and total cost of the solution. Because some protocols such as SCSI and Ethernet now operate many orders of magnitude faster than when originally deployed, scalability of the interface is one major factor, as it prevents costly shifts to technologies that are not backward compatible. Underscoring this is the fact that these shifts often happen involuntarily or by surprise, especially when a vendor abandons support for a proprietary system.
By convention, bus and network data rates are denoted either inbits per second–bit/s,kbit/s(103bit/s),Mbit/s(106bit/s),Gbit/s(109bit/s),Tbit/s(1012bit/s) – orbytes per second–B/s,kB/s(103B/s),MB/s(106B/s),GB/s(109B/s),TB/s(1012B/s). In general,parallelinterfaces are quoted inB/sandserialinbit/s. The more commonly used is shown below inboldtype.
On devices likemodems, bytes may be more than 8 bits long because they may be individually padded out with additional start and stop bits; the figures below will reflect this. Where channels useline codes(such asEthernet,Serial ATA, andPCI Express), quoted rates are for the decoded signal.
The figures below aresimplexdata rates, which may conflict with the duplex rates vendors sometimes use in promotional materials. Where two values are listed, the first value is thedownstreamrate and the second value is the upstream rate.
The use ofdecimal prefixesis standard in data communications.
The figures below are grouped by network or bus type, then sorted within each group from lowest to highest bandwidth; gray shading indicates a lack of known implementations.
As stated above, all quoted bandwidths are for each direction. Therefore, forduplexinterfaces (capable of simultaneous transmission both ways), the stated values aresimplex(one way) speeds, rather than total upstream+downstream.
Time signal station toradio clock
802.11networks in infrastructure mode are half-duplex; all stations share the medium. In infrastructure or access point mode, all traffic has to pass through anAccess Point(AP). Thus, two stations on the same access point that are communicating with each other must have each and every frame transmitted twice: from the sender to the access point, then from the access point to the receiver. This approximately halves the effective bandwidth.
802.11 networks in ad hoc mode are still half-duplex, but devices communicate directly rather than through an access point. In this mode all devices must be able toseeeach other, instead of only having to be able toseethe access point.
xLPC protocol includes high overhead. While the gross data rate equals 33.3 million 4-bit-transfers per second (or16.67MB/s), the fastest transfer, firmware read, results in15.63MB/s. The next fastest bus cycle, 32-bit ISA-style DMA write, yields only6.67MB/s. Other transfers may be as low as2MB/s.[42]
yUses128b/130bencoding, meaning that about 1.54% of each transfer is used for error detection instead of carrying data between the hardware components at each end of the interface. For example, a single link PCIe 3.0 interface has an8 Gbit/stransfer rate, yet its usable bandwidth is only about7.88 Gbit/s.
zUses8b/10b encoding, meaning that 20% of each transfer is used by the interface instead of carrying data from between the hardware components at each end of the interface. For example, a single link PCIe 1.0 has a2.5 Gbit/stransfer rate, yet its usable bandwidth is only2 Gbit/s(250 MB/s).
wUsesPAM-4encoding and a 256 bytesFLITblock, of which 14 bytes areFECandCRC, meaning that 5.47% of total data rate is used for error detection and correction instead of carrying data. For example, a single link PCIe 6.0 interface has a64 Gbit/stotal transfer rate, yet its usable bandwidth is only60.5 Gbit/s.
aUses8b/10b encodingbUses64b/66b encodingcUses 128b/150b encoding
The table below shows values forPCmemory module types.
These modules usually combine multiple chips on onecircuit board.
SIMM modules connect to the computer via an 8-bit- or 32-bit-wide interface. RIMM modules used byRDRAMare 16-bit- or 32-bit-wide.[49]DIMM modules connect to the computer via a 64-bit-wide interface.
Some other computer architectures use different modules with a different bus width.
In a single-channel configuration, only one module at a time can transfer information to the CPU.
In multi-channel configurations, multiple modules can transfer information to the CPU at the same time, in parallel.FPM,EDO,SDR, andRDRAMmemory was not commonly installed in a dual-channel configuration.DDRandDDR2memory is usually installed in single- or dual-channel configuration.DDR3memory is installed in single-, dual-, tri-, and quad-channel configurations.
Bit rates of multi-channel configurations are the product of the module bit-rate (given below) and the number of channels.
aThe clock rate at whichDRAMmemory cells operate. Thememory latencyis largely determined by this rate. Note that until the introduction ofDDR4the internal clock rate saw relatively slow progress.DDR/DDR2/DDR3memory uses 2n/4n/8n (respectively)prefetch bufferto provide higher throughput, while the internal memory speed remains similar to that of the previous generation.
bThe memory speed or clock rate advertised by manufactures and suppliers usually refers to this rate (with 1 GT/s = 1 GHz). Note that modern types of memory useDDR buswith two transfers per clock.
RAM memory modules are also utilised bygraphics processing units; however, memory modules for those differ somewhat from standard computer memory, particularly with lower power requirements, and are specialised to serve GPUs: for example,GDDR3was fundamentally based onDDR2. Every graphics memory chip is directly connected to the GPU (point-to-point). The total GPU memory bus width varies with the number of memory chips and the number of lanes per chip. For example, GDDR5 specifies either 16 or 32 lanes perdevice(chip), while GDDR5X specifies 64 lanes per chip. Over the years, bus widths rose from 64-bit to 512-bit and beyond: e.g.HBMis 1024 bits wide.[50]Because of this variability, graphics memory speeds are sometimes compared per pin. For direct comparison to the values for 64-bit modules shown above, video RAM is compared here in 64-lane lots, corresponding to two chips for those devices with 32-bit widths.
In 2012, high-end GPUs used 8 or even 12 chips with 32 lanes each, for a total memory bus width of 256 or 384 bits. Combined with a transfer rate per pin of 5 GT/s or more, such cards could reach 240 GB/s or more.
RAM frequencies used for a given chip technology vary greatly. Where single values are given below, they are examples from high-end cards.[51]Since many cards have more than one pair of chips, the total bandwidth is correspondingly higher. For example, high-end cards often have eight chips, each 32 bits wide, so the total bandwidth for such cards is four times the value given below.
Data rates given are from the video source (e.g., video card) to receiving device (e.g., monitor) only. Out of band and reverse signaling channels are not included.
aUses8b/10b encoding(20% coding overhead)bUses 16b/18b encoding (11% overhead)cUses 128b/132b encoding (3% overhead)
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The following is a list ofmobile telecommunicationsnetworks usingthird-generationUniversal Mobile Telecommunications System(UMTS) technology. This list does not aim to cover all networks, but instead focuses on networks deployed on frequencies other than 2100 MHz which is commonly deployed around the globe and on Multiband deployments.
Networks in Europe, the Middle East and Africa are exclusively deployed on 2100 MHz (Band 1) and/or 900 MHz (Band 8).
Networks in this region are commonly deployed on 850 MHz (Band 5) and/or 1900 MHz (Band 2) unless denoted otherwise.
Networks in Asia are commonly deployed on 2100 MHz (Band 1) unless denoted otherwise.
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The following is a list ofmobile telecommunicationsnetworks usingthird-generationUniversal Mobile Telecommunications System(UMTS) technology. This list does not aim to cover all networks, but instead focuses on networks deployed on frequencies other than 2100 MHz which is commonly deployed around the globe and on Multiband deployments.
Networks in Europe, the Middle East and Africa are exclusively deployed on 2100 MHz (Band 1) and/or 900 MHz (Band 8).
Networks in this region are commonly deployed on 850 MHz (Band 5) and/or 1900 MHz (Band 2) unless denoted otherwise.
Networks in Asia are commonly deployed on 2100 MHz (Band 1) unless denoted otherwise.
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TheMobile Broadband Allianceis aconsortiumof companies that have aligned to promote hardware with built-inHSPAbroadband.
The companies include the mobile operatorsVodafone,Orange, Telefónica Europe,T-Mobile,3Group,Telecom ItaliaandTeliaSonera, and the hardware manufacturersDell,Asus,Toshiba,Lenovo,Qualcomm,Ericsson,Gemalto, andECS.
This technology-related article is astub. You can help Wikipedia byexpanding it.
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https://en.wikipedia.org/wiki/Mobile_Broadband_Alliance
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Intelecommunications, amulti-band device(including (2)dual-band, (3)tri-band, (4)quad-bandand (5)penta-banddevices) is a communication device (especially amobile phone) that supports multipleradio frequencybands. All devices which have more than one channel use multiple frequencies; a band however is a group of frequencies containing many channels. Multiple bands in mobile devices supportroamingbetween different regions where different standards are used for mobile telephone services. Where the bands are widely separated in frequency, parallel transmit and receive signal path circuits must be provided, which increases the cost, complexity and power demand of multi-band devices.[citation needed]
The termquad-banddescribes a device that supports four frequency bands: the 850 and 1900 MHz bands, which are used in the Americas, and 900 / 1800, which are used in most other parts of the world.[1]MostGSM/UMTSphones support all four bands, while mostCDMA2000/1xRTT phones (mostly North America and voice transmission only) do not, and so are considered onlydual-banddevices. A few phones support both of the domestic frequencies but only one foreign one for limitedroaming, making themtri-bandphones.[citation needed]
The termpenta-banddescribes a device that supports a fifth frequency band, commonly the 1700/2100 MHz band in much of the world. TheAdvanced Wireless Services(AWS) 1700 MHz band is also seeing increased usage.[citation needed]
In theUnited Statesonly, the two largest carriers are instead implementing 4G LTE in the 700 MHz band, which was reallocated fromTV broadcastingduring theDTV transition.TV stationswere forced to move to lowerUHFand even far worseVHFfrequencies with poorermobile TVand even regularterrestrial TVperformance[citation needed], because the 700 MHz band has betterradio propagationcharacteristics that allowmobile phone signalto penetrate deeper into buildings with lessattenuationthan the 1700 MHz or 2100 MHz bands.[citation needed]
AT&T Mobilitydevices use formerTV channel53 and 54 nationwide and has purchased spectrum from former TV channel 55 nationwide (purchased fromQualcomm's defunctMediaFLOpay TVservice), and also channel 56 in densely populated areas such asCaliforniaand theNortheast Corridor.Verizon Wirelessformerly held frequencies just above TV channel 51, which is still in use, causingadjacent-channel interferencethat is preventing the carrier from using them until the planned top-downspectrum repackingoccurs. The channel 52 spectrum was later purchased byT-Mobile USwho now uses this spectrum for their network. Verizon now uses higher blocks within the former TV band (channels 60 and 61).[citation needed]
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Theinternational mobile subscriber identity(IMSI;/ˈɪmziː/) is a number that uniquely identifies every user of acellular network.[1]It is stored as a64-bitfield and is sent by the mobile device to the network. It is also used for acquiring other details of the mobile in thehome location register(HLR) or as locally copied in thevisitor location register. To preventeavesdroppersfrom identifying and tracking the subscriber on the radio interface, the IMSI is sent as rarely as possible and a randomly-generatedTMSIis sent instead.[citation needed]
The IMSI is used inanymobile network that interconnects with other networks. ForGSM,UMTSandLTEnetworks, this number was provisioned in theSIMcard and forcdmaOneandCDMA2000networks, in the phone directly or in theR-UIMcard (the CDMA equivalent of the SIM card). Both cards have been superseded by theUICC.
An IMSI is usually presented as a 15-digit number but can be shorter. For example,MTN South Africa's old IMSIs that are still in use in the market are 14 digits long. The first 3 digits represent themobile country code(MCC), which is followed by themobile network code(MNC), either 2-digit (European standard) or 3-digit (North American standard). The length of the MNC depends on the value of the MCC, and it is recommended that the length is uniform within a MCC area.[2]The remaining digits are themobile subscription identification number(MSIN) within the network's customer base, usually 9 to 10 digits long, depending on the length of the MNC.
The IMSI conforms to theITUE.212 numbering standard.
IMSIs can sometimes be mistaken for theICCID(E.118), which is the identifier for the physical SIM card itself (or now the virtual SIM card if it is aneSIM). The IMSI lives as part of the profile (or one of several profiles if the SIM and operator support multi-IMSI SIMs) on the SIM/ICCID.
IMSI analysisis the process of examining a subscriber's IMSI to identify the network the IMSI belongs to, and whether subscribers from that network may use a given network (if they are not local subscribers, this requires a roaming agreement).
If the subscriber is not from the provider's network, the IMSI must be converted to a Global Title, which can then be used for accessing the subscriber's data in the remoteHLR. This is mainly important for international mobileroaming. Outside North America, the IMSI is converted to the Mobile Global Title (MGT) format, standardE.214, which is similar to anE.164number.E.214provides a method to convert the IMSI into a number that can be used for routing to internationalSS7switches. E.214 can be interpreted as implying that there are two separate stages of conversion; first determine the MCC and convert to E.164country calling codethen determine MNC and convert to national network code for the carrier's network. But this process is not used in practice and the GSM numbering authority has clearly stated that a one-stage process is used[1].
In North America, the IMSI is directly converted to an E.212 number with no modification of its value. This can be routed directly on American SS7 networks.
After this conversion,SCCPis used to send the message to its final destination. For details, seeGlobal Title Translation.
This example shows the actual practice which is not clearly described in the standards.
Translation rule:
Therefore, 284011234567890 becomes 359881234567890 under the E.214 numbering plan.
Translation rule:
Therefore, 310150123456789 becomes 14054123456789 under the E.214 numbering plan.
The result is an E.214 compliant Global Title, (Numbering Plan Indicatoris set to 7 in the SCCP message). This number can now be
sent to Global Title Analysis.
Translation rule:
Therefore, 284011234567890 becomes 284011234567890 under the E.212 numbering plan.
This number has to be converted on the ANSI to ITU boundary. For more details please seeGlobal Title Translation.
The Home Network Identity (HNI) is the combination of the MCC and the MNC. This is the number which fully identifies a subscriber's home network. This combination is also known as thePLMN.
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https://en.wikipedia.org/wiki/International_mobile_subscriber_identity
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Amobile phoneorcell phone[a]is a portabletelephonethat allows users to make and receivecallsover aradio frequencylink while moving within a designated telephone service area, unlike fixed-location phones (landline phones). This radio frequency link connects to the switching systems of amobile phone operator, providing access to thepublic switched telephone network(PSTN). Modern mobile telephony relies on acellular networkarchitecture, which is why mobile phones are often referred to as 'cell phones' in North America.
Beyond traditionalvoice communication, digital mobile phones have evolved to support a wide range of additional services. These includetext messaging,multimedia messaging,email, andinternet access(viaLTE,5G NRorWi-Fi), as well as short-range wireless technologies likeBluetooth,infrared, andultra-wideband(UWB).
Mobile phones also support a variety ofmultimediacapabilities, such asdigital photography,video recording, andgaming. In addition, they enable multimedia playback andstreaming, including video content, as well asradioandtelevision streaming. Furthermore, mobile phones offersatellite-basedservices, such asnavigationandmessaging, as well as business applications andpayment solutions(viascanning QR codesornear-field communication(NFC)).
Mobile phones offering only basic features are often referred to asfeature phones(slang:dumbphones), while those with advanced computing power are known assmartphones.[1]
The first handheld mobile phone was demonstrated byMartin CooperofMotorolainNew York Cityon 3 April 1973, using a handset weighing c. 2 kilograms (4.4 lbs).[2]In 1979,Nippon Telegraph and Telephone(NTT) launched the world's first cellular network in Japan.[3]In 1983, theDynaTAC 8000xwas the first commercially available handheld mobile phone. From 1993 to 2024, worldwide mobile phone subscriptions grew to over 9.1 billion; enough to provide one for every person on Earth.[4][5]In 2024, the top smartphone manufacturers worldwide wereSamsung,AppleandXiaomi; smartphone sales represented about 50 percent of total mobile phone sales.[6][7]For feature phones as of 2016[update], the top-selling brands were Samsung,NokiaandAlcatel.[8]
Mobile phones are considered an important human invention as they have been one of the most widely used and sold pieces ofconsumer technology.[9]The growth in popularity has been rapid in some places; for example, in the UK, the total number of mobile phones overtook the number of houses in 1999.[10]Today, mobile phones are globally ubiquitous,[11]and in almost half the world's countries, over 90% of the population owns at least one.[12]
A handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917,FinnishinventorEric Tigerstedtfiled a patent for a "pocket-size folding telephone with a very thin carbon microphone". Early predecessors of cellular phones includedanalogradio communications from ships and trains. The race to create truly portable telephone devices began after World War II, with developments taking place in many countries. The advances inmobile telephonyhave been traced in successive "generations", starting with the early zeroth-generation (0G) services, such asBell System'sMobile Telephone Serviceand its successor, theImproved Mobile Telephone Service. These 0G systems were notcellular, supported a few simultaneous calls, and were very expensive.
The first handheld cellular mobile phone was demonstrated byJohn F. Mitchell[13][14]andMartin CooperofMotorolain 1973, using a handset weighing 2 kilograms (4.4 lb).[2]The first commercial automated cellular network (1G)analogwas launched in Japan byNippon Telegraph and Telephonein 1979. This was followed in 1981 by the simultaneous launch of theNordic Mobile Telephone(NMT) system in Denmark, Finland, Norway, and Sweden.[15]Several other countries then followed in the early to mid-1980s. These first-generation (1G) systems could support far more simultaneous calls but still usedanalogcellular technology. In 1983, theDynaTAC 8000xwas the first commercially available handheld mobile phone.
In 1991, the second-generation (2G) digital cellular technology was launched in Finland byRadiolinjaon theGSMstandard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators. The GSM standard is a European initiative expressed at theCEPT("Conférence Européenne des Postes et Telecommunications", European Postal and Telecommunications conference). The Franco-German R&D cooperation demonstrated the technical feasibility, and in 1987, a Memorandum of Understanding was signed between 13 European countries that agreed to launch a commercial service by 1991. The first version of the GSM standard had 6,000 pages. TheIEEEandRSEawardedThomas HaugandPhilippe Dupuisthe 2018James Clerk Maxwell medalfor their contributions to the first digital mobile telephone standard.[16]In 2018, the GSM was used by over 5 billion people in over 220 countries. The GSM (2G) has evolved into 3G, 4G and 5G. The standardization body for GSM started at the CEPT Working Group GSM (Group Special Mobile) in 1982 under the umbrella of CEPT. In 1988,ETSIwas established, and all CEPT standardization activities were transferred to ETSI. Working Group GSM became Technical Committee GSM. In 1991, it became Technical Committee SMG (Special Mobile Group) when ETSI tasked the committee with UMTS (3G). In addition to transmitting voice over digital signals, the 2G network introduced data services for mobile, starting withSMStext messages, then expanding toMultimedia Messaging Service(MMS), andmobile internetwith a theoretical maximum transfer speed of 384 kbit/s (48 kB/s).
In 2001, the third-generation (3G) was launched in Japan byNTT DoCoMoon theWCDMAstandard.[17]This was followed by 3.5G or 3G+ enhancements based on thehigh-speed packet access(HSPA) family, allowingUMTSnetworks to have higher data transfer speeds and capacity. 3G is able to providemobile broadbandaccess of severalMbit/sto smartphones andmobile modemsin laptop computers. This ensures it can be applied to mobile Internet access,VoIP, video calls, and sending large e-mail messages, as well as watching videos, typically instandard-definitionquality.
By 2009, it had become clear that, at some point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications, such asstreaming media.[18]Consequently, the industry began looking to data-optimized fourth-generation (4G) technologies, with the promise of speed improvements up to tenfold over existing 3G technologies. The first publicly availableLTEservice was launched in Scandinavia byTeliaSonerain 2009. In the 2010s, 4G technology has found diverse applications across various sectors, showcasing its versatility in delivering high-speed wireless communication, such as mobile broadband, theinternet of things(IoT),fixed wireless access, and multimedia streaming (including music, video,radio, andtelevision).
Deployment of fifth-generation (5G) cellular networks commenced worldwide in 2019. The term "5G" was originally used in research papers and projects to denote the next major phase in mobile telecommunication standards beyond the4G/IMT-Advancedstandards. The3GPPdefines 5G as any system that adheres to the5G NR(5G New Radio) standard. 5G can be implemented in low-band, mid-band or high-band millimeter-wave, with download speeds that can achievegigabit-per-second(Gbit/s) range, aiming for a network latency of 1 ms. This near-real-time responsiveness and improved overall data performance are crucial for applications likeonline gaming,augmentedandvirtual reality,autonomous vehicles, IoT, and critical communication services.
Smartphones are defined by their advanced computing capabilities, which include internet connectivity and access to a wide range of applications. TheInternational Telecommunication Unionmeasures those with Internet connection, which it callsActive Mobile-Broadband subscriptions(which includes tablets, etc.). In developed countries, smartphones have largely replaced earlier mobile technologies, while in developing regions, they account for around 50% of all mobile phone usage.
Feature phone is a term typically used as aretronymto describe mobile phones which are limited in capabilities in contrast to a modern smartphone. Feature phones typically providevoice callingandtext messagingfunctionality, in addition to basicmultimediaandInternetcapabilities, and other services offered by the user'swireless service provider. A feature phone has additional functions over and above a basic mobile phone, which is only capable of voice calling and text messaging.[20][21]Feature phones and basic mobile phones tend to use a proprietary, custom-designedsoftwareanduser interface. By contrast, smartphones generally use amobile operating systemthat often shares common traits across devices.
The critical advantage that modern cellular networks have over predecessor systems is the concept offrequency reuseallowing many simultaneous telephone conversations in a given service area. This allows efficient use of the limitedradio spectrumallocated to mobile services, and lets thousands of subscribers converse at the same time within a given geographic area.
Former systems would cover a service area with one or two powerfulbase stationswith a range of up to tens of kilometers' (miles), using only a few sets of radio channels (frequencies). Once these few channels were in use by customers, no further customers could be served until another user vacated a channel. It would be impractical to give every customer a unique channel since there would not be enoughbandwidthallocated to the mobile service. As well, technical limitations such as antenna efficiency and receiver design limit the range of frequencies a customer unit could use.
Acellular networkmobile phone system gets its name from dividing the service area into many small cells, each with a base station with (for example) a useful range on the order of a kilometer (mile). These systems have dozens or hundreds of possible channels allocated to them. When a subscriber is using a given channel for a telephone connection, that frequency is unavailable for other customers in the local cell and in the adjacent cells. However, cells further away can re-use that channel without interference as the subscriber's handset is too far away to be detected. The transmitter power of each base station is coordinated to efficiently service its own cell, but not to interfere with the cells further away.
Automation embedded in the customer's handset and in the base stations control all phases of the call, from detecting the presence of a handset in a service area, temporary assignment of a channel to a handset making a call, interface with the land-line side of the network to connect to other subscribers, and collection of billing information for the service. The automation systems can control the "hand off" of a customer handset moving between one cell and another so that a call in progress continues without interruption, changing channels if required. In the earliest mobile phone systems by contrast, all control was done manually; the customer would search for an unoccupied channel and speak to a mobile operator to request connection of a call to a landline number or another mobile. At the termination of the call the mobile operator would manually record the billing information.
Mobile phones communicate with cell towers that are placed to give coverage across a telephone service area, which is divided up into 'cells'. Each cell uses a different set of frequencies from neighboring cells, and will typically be covered by three towers placed at different locations. The cell towers are usually interconnected to each other and the phone network and the internet by wired connections. Due to bandwidth limitations each cell will have a maximum number of cell phones it can handle at once. The cells are therefore sized depending on the expected usage density, and may be much smaller in cities. In that case much lower transmitter powers are used to avoid broadcasting beyond the cell.
In order to handle the high traffic, multiple towers can be set up in the same area (using different frequencies). This can be done permanently or temporarily such as at special events or in disasters. Cell phone companies will bring a truck with equipment to host the abnormally high traffic.
Capacity was further increased when phone companies implemented digital networks. With digital, one frequency can host multiple simultaneous calls.
Additionally, short-rangeWi-Fiinfrastructure is often used by smartphones as much as possible as it offloads traffic from cell networks on to local area networks.
The common components found on all mobile phones are:
Low-end mobile phones are often referred to asfeature phonesand offer basic telephony. Handsets with more advanced computing ability through the use of native software applications are known as smartphones. The firstGSMphones and many feature phones had NOR flash memory, from which processor instructions could be executed directly in an execute in place architecture and allowed for short boot times. With smartphones, NAND flash memory was adopted as it has larger storage capacities and lower costs, but causes longer boot times because instructions cannot be executed from it directly, and must be copied to RAM memory first before execution.[22]
Mobile phones havecentral processing units(CPUs), similar to those in computers, but optimised to operate in low power environments.
Mobile CPU performance depends not only on the clock rate (generally given in multiples ofhertz)[23]but also thememory hierarchyalso greatly affects overall performance. Because of these problems, the performance of mobile phone CPUs is often more appropriately given by scores derived from various standardized tests to measure the real effective performance in commonly used applications.
One of the main characteristics of phones is thescreen. Depending on the device's type and design, the screen fills most or nearly all of the space on a device's front surface. Many smartphone displays have anaspect ratioof16:9, but taller aspect ratios became more common in 2017.
Screen sizes are often measured in diagonalinchesormillimeters; feature phones generally have screen sizes below 90 millimetres (3.5 in). Phones with screens larger than 130 millimetres (5.2 in) are often called "phablets." Smartphones with screens over 115 millimetres (4.5 in) in size are commonly difficult to use with only a single hand, since most thumbs cannot reach the entire screen surface; they may need to be shifted around in the hand, held in one hand and manipulated by the other, or used in place with both hands. Due to design advances, some modern smartphones with large screen sizes and "edge-to-edge" designs have compact builds that improve their ergonomics, while the shift to taller aspect ratios have resulted in phones that have larger screen sizes whilst maintaining the ergonomics associated with smaller 16:9 displays.[24][25][26]
Liquid-crystal displaysare the most common; others areIPS,LED,OLED, andAMOLEDdisplays. Some displays are integrated with pressure-sensitive digitizers, such as those developed byWacomandSamsung,[27]and Apple's "3D Touch" system.
In sound, smartphones and feature phones vary little. Some audio-quality enhancing features, such asVoice over LTEandHD Voice, have appeared and are often available on newer smartphones. Sound quality can remain a problem due to the design of the phone, the quality of the cellular network and compression algorithms used inlong-distance calls.[28][29]Audio quality can be improved using aVoIPapplication overWiFi.[30]Cellphones have small speakers so that the user can use aspeakerphonefeature and talk to a person on the phone without holding it to their ear. The small speakers can also be used to listen to digital audio files of music or speech or watch videos with an audio component, without holding the phone close to the ear.
The typical lifespan of a mobile phone battery is approximately two to three years, although this varies based on usage patterns, environmental conditions, and overall care. Most modern mobile phones uselithium-ion(Li-ion) batteries, which are designed to endure between 500 and 2,500 charge cycles. The exact number of cycles depends on factors such as charging habits, operating temperature, and battery management systems.[31]
Li-ion batteries gradually degrade over time due to chemical aging, leading to reduced capacity and performance, often noticeable after one or two years of regular use. Unlike older battery types, such asnickel-metal hydride(Ni-MH), Li-ion batteries do not need to be fully discharged to maintain their longevity. In fact, they perform best when kept between 30% and 80% of their full charge.[32]While practices such as avoiding excessive heat and minimizing overcharging can help preserve battery health, many modern devices include built-in safeguards.[33]These safeguards, typically managed by the phone's internal battery management system (BMS), prevent overcharging by cutting off power once the battery reaches full capacity. Additionally, most contemporary chargers and devices are designed to regulate charging to minimize stress on the battery. Therefore, while good charging habits can positively impact battery longevity, most users benefit from these integrated protections, making battery maintenance less of a concern in day-to-day use.[34][35]
Future mobile phone batteries are expected to utilize advanced technologies such assilicon-carbon(Si/C) batteries andsolid-statebatteries, which promise to offer higher energy densities, longer lifespans, and improved safety compared to current lithium-ion batteries.[36][37][38]
Mobile phones require a smallmicrochipcalled a Subscriber Identity Module orSIM card, in order to function. The SIM card is approximately the size of a small postage stamp and is usually placed underneath the battery in the rear of the unit. The SIM securely stores theservice-subscriber key (IMSI)and theKiused to identify and authenticate the user of the mobile phone. The SIM card allows users to change phones by simply removing the SIM card from one mobile phone and inserting it into another mobile phone or broadband telephony device, provided that this is not prevented by aSIM lock. The first SIM card was made in 1991 by Munich smart card makerGiesecke & Devrientfor the Finnish wireless network operatorRadiolinja.[citation needed]
A hybrid mobile phone can hold up to four SIM cards, with a phone having a differentdevice identifierfor each SIM Card. SIM andR-UIMcards may be mixed together to allow bothGSMandCDMAnetworks to be accessed. From 2010 onwards, such phones became popular in emerging markets,[39]and this was attributed to the desire to obtain the lowest calling costs.
When the removal of a SIM card is detected by the operating system, it may deny further operation until a reboot.[40]
Feature phones have basic software platforms. Smartphones have advanced software platforms.Android OShas been thebest-selling OSworldwide on smartphones since 2011.[41]As of March 2025,Android OShad 71.9% of the overall market share, while the second-largest,iOS, had 27.7%.[42]
A mobile app is a computer program designed to run on a mobile device, such as a smartphone. The term "app" is a shortening of the term "software application".
A common data application on mobile phones isShort Message Service(SMS) text messaging. The first SMS message was sent from a computer to a mobile phone in 1992 in the UK while the first person-to-person SMS from phone to phone was sent in Finland in 1993. The firstmobile newsservice, delivered via SMS, was launched in Finland in 2000,[43]and subsequently many organizations provided "on-demand" and "instant" news services by SMS.Multimedia Messaging Service(MMS) was introduced in March 2002.[44]
The introduction of Apple's App Store for the iPhone and iPod Touch in July 2008 popularized manufacturer-hostedonline distributionfor third-party applications (software and computer programs) focused on a single platform. There are a huge variety of apps, includingvideo games, music products and business tools. Up until that point, smartphone application distribution depended onthird-party sourcesproviding applications for multiple platforms, such asGetJar,Handango,Handmark, andPocketGear. Following the success of the App Store, other smartphone manufacturers launched application stores, such as Google's Android Market (later renamed to the Google Play Store), RIM'sBlackBerry App World, or Android-related app stores likeAptoide,Cafe Bazaar,F-Droid,GetJar, andOpera Mobile Store. In February 2014, 93% ofmobile developerswere targeting smartphones first for mobile app development.[45]
As of 2022, the top five manufacturers worldwide were Samsung (21%), Apple (16%), Xiaomi (13%), Oppo (10%), and Vivo (9%).[46]
From 1983 to 1998,Motorolawas market leader in mobile phones.Nokiawas the market leader in mobile phones from 1998 to 2012.[47]In Q1 2012,Samsungsurpassed Nokia, selling 93.5 million units as against Nokia's 82.7 million units. Samsung has retained its top position since then.
Aside from Motorola, European brands such as Nokia,SiemensandEricssononce held large sway over the global mobile phone market, and many new technologies were pioneered in Europe. By 2010, the influence of European companies had significantly decreased due to fierce competition from American and Asian companies, to where most technical innovation had shifted.[48][49]Apple and Google, both of the United States, also came to dominate mobile phone software.[48]
The world's largest individual mobile operator by number of subscribers isChina Mobile, which has over 902 million mobile phone subscribers as of June 2018[update].[50]Over 50 mobile operators have over ten million subscribers each, and over 150 mobile operators had at least one million subscribers by the end of 2009.[51]In 2014, there were more than seven billion mobile phone subscribers worldwide, a number that is expected to keep growing.
Mobile phones are used for a variety of purposes, such as keeping in touch with family members, for conducting business, and in order to have access to a telephone in the event of an emergency. Some people carry more than one mobile phone for different purposes, such as for business and personal use. Multiple SIM cards may be used to take advantage of the benefits of different calling plans. For example, a particular plan might provide for cheaper local calls, long-distance calls, international calls, or roaming.
The mobile phone has been used in a variety of diverse contexts in society. For example:
In 1998, one of the first examples ofdistributing and selling media contentthrough the mobile phone was the sale ofringtonesbyRadiolinjain Finland. Soon afterwards, other media content appeared, such as news, video games, jokes, horoscopes, TV content and advertising. Most early content for mobile phones tended to be copies oflegacy media, such as banner advertisements or TV news highlight video clips. Recently, unique content for mobile phones has been emerging, from ringtones andringback tonestomobisodes, video content that has been produced exclusively for mobile phones.[citation needed]
In many countries, mobile phones are used to providemobile bankingservices, which may include the ability to transfer cash payments by secure SMS text message. Kenya'sM-PESAmobile banking service, for example, allows customers of the mobile phone operatorSafaricomto hold cash balances which are recorded on their SIM cards. Cash can be deposited or withdrawn from M-PESA accounts at Safaricom retail outlets located throughout the country and can be transferred electronically from person to person and used to pay bills to companies.
Branchless bankinghas also been successful in South Africa and thePhilippines. A pilot project inBaliwas launched in 2011 by theInternational Finance Corporationand anIndonesianbank,Bank Mandiri.[59]
Mobile payments were first trialled in Finland in 1998 when two Coca-Cola vending machines inEspoowere enabled to work with SMS payments. Eventually, the idea spread and in 1999, the Philippines launched the country's first commercial mobile payments systems with mobile operatorsGlobeandSmart.[citation needed]
Some mobile phones can makemobile paymentsvia direct mobile billing schemes, or throughcontactless paymentsif the phone and thepoint of salesupportnear field communication(NFC).[60]Enabling contactless payments through NFC-equipped mobile phones requires the co-operation of manufacturers, network operators, and retail merchants.[61][62]
Mobile phones are commonly used to collect location data. While the phone is turned on, the geographical location of a mobile phone can be determined easily (whether it is being used or not) using a technique known asmultilaterationto calculate the differences in time for a signal to travel from the mobile phone to each of severalcell towersnear the owner of the phone.[63][64]
The movements of a mobile phone user can be tracked by their service provider and, if desired, by law enforcement agencies and their governments. Both theSIM cardand the handset can be tracked.[63]
China has proposed using this technology to track the commuting patterns of Beijing city residents.[65]In the UK and US, law enforcement and intelligence services use mobile phones to perform surveillance operations.[66]
Hackers have been able to track a phone's location, read messages, and record calls, through obtaining a subscribers phone number.[67]
Studies have shown that around 40–50% of the environmental impact of mobile phones occurs during the manufacture of their printed wiring boards and integrated circuits.[68]
The average user replaces their mobile phone every 11 to 18 months,[69]and the discarded phones then contribute toelectronic waste. Mobile phone manufacturers withinEuropeare subject to theWEEE directive, and Australia has introduced a mobile phone recycling scheme.[70]
Apple Inc.had an advanced robotic disassembler and sorter called Liam specifically for recycling outdated or broken iPhones.[71]
According to theFederal Communications Commission, one out of three robberies involve the theft of a cellular phone.[citation needed]Police data in San Francisco show that half of all robberies in 2012 were thefts of cellular phones.[citation needed]Anonline petitiononChange.org, calledSecure our Smartphones, urged smartphone manufacturers to installkill switchesin their devices to make them unusable if stolen. The petition is part of a joint effort by New York Attorney GeneralEric Schneidermanand San Francisco District AttorneyGeorge Gascónand was directed to theCEOsof the major smartphone manufacturers and telecommunication carriers.[72]On 10 June 2013, Apple announced that it would install a "kill switch" on itsnext iPhone operating system, due to debut in October 2013.[73]
All mobile phones have a unique identifier calledIMEI. Anyone can report their phone as lost or stolen with their Telecom Carrier, and the IMEI would be blacklisted with a central registry.[74]Telecom carriers, depending upon local regulation can or must implement blocking of blacklisted phones in their network. There are, however, a number of ways to circumvent a blacklist. One method is to send the phone to a country where the telecom carriers are not required to implement the blacklisting and sell it there,[75]another involves altering the phone's IMEI number.[76]Even so, mobile phones typically have less value on the second-hand market if the phones original IMEI is blacklisted.
Demand for metals used in mobile phones and other electronics fuelled theSecond Congo War, which claimed almost 5.5 million lives.[77]In a 2012 news story,The Guardianreported: "In unsafe mines deep underground in eastern Congo,children are workingto extract minerals essential for the electronics industry. The profits from the minerals finance the bloodiest conflict since the second world war; the war has lasted nearly 20 years and has recently flared up again. For the last 15 years, theDemocratic Republic of the Congohas been a major source of natural resources for the mobile phone industry."[78]The companyFairphonehas worked to develop a mobile phone that does not containconflict minerals.[citation needed]
Due to concerns by theOrthodox Jewishrabbinate in Britain that texting by youths could waste time and lead to "immodest" communication, the rabbinate recommended that phones with text-messaging capability not be used by children; to address this, they gave their official approval to a brand of "Kosher" phones with no texting capabilities. Although these phones are intended to preventimmodesty, some vendors report good sales to adults who prefer the simplicity of the devices; other Orthodox Jews question the need for them.[79]
In Israel, similar phones to kosher phones with restricted features exist to observe thesabbath; under Orthodox Judaism, the use of any electrical device is generally prohibited during this time, other than to save lives, or reduce the risk of death or similar needs. Such phones are approved for use by essential workers, such as health, security, and public service workers.[80]
Restrictions on the use of mobile phones are applied in a number of different contexts, often with the goal of health, safety, security or proper functioning of an establishment, or as a matter of etiquette. Such contexts include:
Mobile phone use while driving, including talking on the phone, texting, or operating other phone features, is common but controversial. It is widely considered dangerous due todistracted driving. Being distracted while operating a motor vehicle has been shown to increase the risk of accidents. In September 2010, the USNational Highway Traffic Safety Administration(NHTSA) reported that 995 people were killed bydrivers distracted by cell phones. In March 2011, a US insurance company,State Farm Insurance, announced the results of a study which showed 19% of drivers surveyed accessed the Internet on a smartphone while driving.[81]Many jurisdictions prohibit the use of mobile phones while driving. In Egypt, Israel, Japan, Portugal, and Singapore, both handheld and hands-free use of a mobile phone (which uses aspeakerphone) is banned. In other countries, including the UK and France and in manyUS states, only handheld phone use is banned while hands-free use is permitted.
A 2011 study reported that over 90% of college students surveyed text (initiate, reply or read) while driving.[82]The scientific literature on the dangers of driving while sending a text message from a mobile phone, ortexting while driving, is limited. A simulation study at theUniversity of Utahfound a sixfold increase in distraction-related accidents when texting.[83]
Due to the increasing complexity of mobile phones, they are often more like mobile computers in their available uses. This has introduced additional difficulties for law enforcement officials when attempting to distinguish one usage from another in drivers using their devices. This is more apparent in countries which ban both handheld and hands-free usage, rather than those which ban handheld use only, as officials cannot easily tell which function of the mobile phone is being used simply by looking at the driver. This can lead to drivers being stopped for using their device illegally for a phone call when, in fact, they were using the device legally, for example, when using the phone's incorporated controls for car stereo,GPSorsatnav.
A 2010 study reviewed the incidence of mobile phone use whilecyclingand its effects on behaviour and safety.[84]In 2013, a national survey in the US reported the number of drivers who reported using their cellphones to access the Internet while driving had risen to nearly one of four.[85]A study conducted by the University of Vienna examined approaches for reducing inappropriate and problematic use of mobile phones, such as using mobile phones while driving.[86]
Accidents involving a driver being distracted by talking on a mobile phone have begun to be prosecuted as negligence similar to speeding. In theUnited Kingdom, from 27 February 2007, motorists who are caught using a hand-held mobile phone while driving will have three penalty points added to their license in addition to the fine of £60.[87]This increase was introduced to try to stem the increase in drivers ignoring the law.[88]Japanprohibits all mobile phone use while driving, including use of hands-free devices. New Zealand has banned hand-held cell phone use since 1 November 2009. Many states in the United States have banned texting on cell phones while driving. Illinois became the 17th American state to enforce this law.[89]As of July 2010[update], 30 states had banned texting while driving, with Kentucky becoming the most recent addition on 15 July.[90]
Public Health Law Researchmaintains a list of distracted driving laws in the United States. This database of laws provides a comprehensive view of the provisions of laws that restrict the use of mobile communication devices while driving for all 50 states and the District of Columbia between 1992 when first law was passed, through 1 December 2010. The dataset contains information on 22 dichotomous, continuous orcategorical variablesincluding, for example, activities regulated (e.g., texting versus talking, hands-free versus handheld), targeted populations, and exemptions.[91]
In the U.S., theFederal Communications Commission(FCC) regulations prohibit the use ofmobile phonesaboard aircraft in flight.[92]Contrary to popular misconception, theFederal Aviation Administration(FAA) does not actually prohibit the use of personal electronic devices (including cell phones) on aircraft. Paragraph (b)(5) of 14 CFR 91.21 permits airlines to determine if devices can be used in flight, allowing use of "any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used."[93]
In Europe, regulations and technology have allowed the limited introduction of the use of passenger mobile phones on some commercial flights, and elsewhere in the world manyairlinesare moving towards allowing mobile phone use in flight.[94]Many airlines still do not allow the use of mobile phones on aircraft.[95]Those that do often ban the use of mobile phones during take-off and landing.
Between 2011 and 2019, an estimated 30,000 walking injuries occurred in the US related to using a cellphone, leading to some jurisdictions attempting to ban pedestrians from using their cellphones.[98][99][100]Other countries, such as China and the Netherlands, have introduced special lanes for smartphone users to help direct and manage them.[101][102]
As of 2007, some hospitals had banned mobile devices due to acommon misconceptionthat their use would create significantelectromagnetic interference.[105][106]
Screen time, the amount of time using a device with a screen, has become an issue for mobile phones since the adaptation of smartphones.[107]Research is being conducted to show the correlation between screen time and the mental and physical harm in child development.[108]To prevent harm, some parents and even governments have placed restrictions on its usage.[109][110]
There have been rumors that mobile phone use can cause cancer, but this is a myth.[111][112]
While there are rumors of mobile phones causing cancer, there was a study conducted by International Agency for Research on Cancer (IARC) that stated the there could be an increase risk of brain tumors with the use of smartphones, this is not confirmed. They also stated that with the lack of data for the research and the usage periods of 15 years will warrant further research for smartphones and the cause of brain tumors.[113]
A study by theLondon School of Economicsfound that banning mobile phones in schools could increase pupils' academic performance, providing benefits equal to one extra week of schooling per year.[114]
Mobile phones are considered an important human invention as it has been one of the most widely used and sold pieces of consumer technology.[9][11]They have also become culturally symbolic. InJapanese mobile phone culturefor example, mobile phones are often decorated with charms. They have also become fashion symbols at times.[115]TheMotorola Razr V3andLG Chocolateare two examples of devices that were popular for being fashionable while not necessarily focusing on the original purpose of mobile phones, i.e. a device to provide mobile telephony.[116]
Some have also suggested that mobile phones or smartphones are astatus symbol.[117]For example a research paper suggested that owning specifically anApple iPhonewas seen to be a status symbol.[118]
Text messaging, which are performed on mobile phones, has also led to the creation of 'SMS language'. It also led to the growing popularity ofemojis.[119]
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https://en.wikipedia.org/wiki/Mobile_phone
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ASIM lock,simlock,network lock,carrier lockor (master)subsidy lockis a technical restriction built intoGSMandCDMA[1]mobile phones bymobile phonemanufacturers for use by service providers to restrict the use of these phones to specific countries and/or networks. This is in contrast to a phone (retrospectively calledSIM-freeorunlocked) that does not impose any SIM restrictions.
Generally phones can be locked to accept onlySIMcards with certainInternational Mobile Subscriber Identities(IMSIs); IMSIs may be restricted by:
Additionally, some phones, especiallyNokiaphones, are locked by group IDs (GIDs), restricting them to a singleMobile virtual network operator(MVNO) of a certain operator.
Most mobile phones can be unlocked to work with anyGSMnetwork provider, but the phone may still display the original branding and may not support features of the new carrier. Besides the locking, phones may also havefirmwareinstalled on them which is specific to the network provider. For example, aVodafoneorTelstrabranded phone inAustraliawill display the relevant logo and may only support features provided by that network (e.g. Vodafone Live!). This firmware is installed by the service provider and is separate from the locking mechanism. Most phones can beunbrandedbyreflashinga different firmware version, a procedure recommended for advanced users only. The reason many network providers SIM lock their phones is that they offer phones at a discount to customers in exchange for acontractto pay for the use of the network for a specified time period, usually between one and three years. Thisbusiness modelallows the company to recoup the cost of the phone over the life of the contract. Such discounts are worth up to several hundredUS dollars. If the phones were not locked, users might sign a contract with one company, get the discounted phone, then stop paying the monthly bill (thus breaking the contract) and start using the phone on another network or even sell the phone for a profit.[2]SIM locking curbs this by prohibiting change of network (using a new SIM).
In some countries, SIM locking is very common if subsidized phones are sold with prepaid contracts. It is important to note, however, that the technology associated with the phone must be compatible with the technology being used by the network carrier. A GSM cell phone will only work with a GSM carrier and will not work on a CDMA network provider. Likewise, a CDMA cell phone will only work with a CDMA carrier and will not work on a GSM network provider.[3][4]Note that newer (2013+) high end mobile phones are capable of supporting both CDMA and GSM technologies, allowing customers to use their mobile devices on any network. Examples of these mobile devices are the AppleiPhone 5c, 6 and newer,Motorola's G4, G5, X Pure,Samsung's Galaxy S6,S7,S8smart phones, mostly phones based on aQualcomm Snapdragonchipset or radio.
In some jurisdictions, such asCanada,[5]Chile,[6]China,Israel,[7]Singapore,[8]and theUnited States[9]it is illegal for providers to sell SIM locked devices. In other countries, carriers may not be required to unlock devices or may require the consumer to pay a fee for unlocking.
Unlocking the phone, however, is almost universally legal.[10]Additionally, it is often legal for carriers to force SIM locks for certain amounts of time, varying by region.
A handset can be unlocked byentering a codeprovided by the network operator. Alternative mechanisms include software running on the handset or a computer attached to the handset, hardware devices that connect to the handset orover-the-airby the carrier. Usually the unlock process is permanent. The code required to remove all locks from a phone is referred to as themaster code,network code key, ormultilock code.
If the phone is network locked it will typically display one of the following messages: SIM network PIN blocked, Enter lock PIN.
There can also be multiple levels of locks placed on the phone by networks, which block the use of other networks' SIM cards. These are usually referred to as "Network Control Key" (NCK) and "Service Provider Control Key" (SPCK), additionally, a Regional lock exists which is specific to Europe and it is called "Region Control Key" (RGCK).
Typically, a locked handset will display a message if a restricted SIM is used, requesting the unlock code. On recent phone models running Android software, the phone will display a message saying "SIM network unlock PIN" or "Enter Network Lock Control Key" if network locked. Windows phones will display the message, "This SIM card can only be used on specific networks. Contact your customer service center for the unlock code". Other handsets may display different messages such as "Enter special code" or "Enter unlocking code," or in some cases the handset will simply display a message stating that it is locked. Once a valid code is entered, the handset will display "Network unlocked" or "Network unlock successful".
The unlock code is verified by the handset and is generated by the manufacturer, typically by an algorithm such as a one wayhashortrapdoor function. Sometimes big telecom providers change the original factory unlock codes as an extra layer of security against unlocking services. For various big brands such as Samsung and Motorola there is no algorithm but just a random code generator where the unlock codes are programmed in the phone itself and then saved in a big database managed by the manufacturer. For the other brands where the unlock codes are still based on algorithms those are based on theIMEInumber and the MCC code and have beenreverse-engineered, stolen or leaked. Some handsets can be unlocked using software that generates an unlock code from an IMEI number and country and operator details using the algorithm specific to the handset. Other manufacturers have taken a more cautious approach, and embed arandomnumber in the handset's firmware that is retained by the manufacturer and the network on whose behalf the lock was applied. These handsets can still be unlocked by online services that have access to either inside people with the manufacturer or with the telecom networks, or they need to be connected to the computer with a cable where specific software will bypass the security and SIM-unlock the phone. Sometimes this is done by advanced calculations to bypass the security the official way and other times using exploits or overwriting parts of the firmware where the lock status is kept, and often even recover a phone that isbrickedor completely damaged in the software sense.
Most handsets have security measures built into their firmware that protects them from repeated attempts to guess the unlock code. After entering more than a certain number of incorrect codes the phone becomesfrozen. This is a state where the phone will display a security message that the phone needs a service. Older phones could no longer be used at all at this point, however modern smartphones often keep working with the original SIM but require extra work to then unlock them correctly. In extreme situations physical access to internal hardware via in-circuit debugging may be utilised (for example, viaJTAGheaders on a circuit board). Such access may be required to modify initialization software used forbooting.
A hardlocked phone is one in which a telecom provider has modified the firmware on the phone to make it impossible to manually enter the unlock codes in any way. The only solution to SIM-unlock such a phone is to change the firmware to a firmware which has not been modified by any telecom provider, a so-called "unbranded firmware".
Handset manufacturers have economic incentives both to strengthen SIM lock security (which placates network providers and enables exclusivity deals) and to weaken it (broadening a handset's appeal to customers who are not interested in the service provider that offers it). Also, making it too difficult to unlock a handset might make it less appealing to network service providers who have a legal obligation to provide unlock codes for certain handsets or in certain countries.
In some cases, a SIM-locked handset is sold at a substantially lower price than an unlocked one, because the service provider expects income through its service. SIM locks are employed on cheaper (pay-as-you-go) handsets, while discounts on more expensive handsets require a subscription that provides guaranteed income. Unlocked handsets have a higher market value, even more so if they are debranded.Debrandinginvolves reflashing or replacing the firmware to remove the operator logo or any limitations or customizations that have been imposed on the handset by the operator, and is usually accomplished with software designed for a particular handset model, however, most smart-phones can be debranded and unlocked solely with the use of special software.
The main reason to unlock a handset is to be able to use it with a different SIM card. Consumers may wish to continue using their previous provider with a new handset or when traveling abroad they may wish to connect to a foreign network with aprepaid subscription.
Nevertheless, the fundamental principle of GSM and its successors, is open interfaces which encourage competition among multiple vendors. This is the reason a mobile phone is, in fact, a combination of a phone and the subscriber identity module (SIM). Locking the phone to a network is not much different from having the SIM built into the mobile phone. Network operators in many industrialized countries are not bound by law to give the phone unlocking code to subscribers even after the expiry of the contract period.
A practice known asbox breakingis common[11]in theUnited Kingdomand other markets. This involves purchasing subsidized handsets (usually pay-as-you-go) from retail stores, unlocking the phones, and then selling them (often abroad) for a higher price than the subsidised retail price. The SIM card that came with the handset is then either thrown away, sold, or used elsewhere. This practice is legal in the UK and provides ade factolimit to the extent to which networks are willing to subsidize pay-as-you-go handsets. While the act ofbox breakingis legal, some businesses are also engaging in illegal activities such as exporting the box-broken phones to other countries, to sell asgrey marketgoods without paying import duties (known ascarousel fraud) or substituting counterfeit batteries and chargers.[12][13]
Some companies offer an online unlocking service. This service requires that individuals who wish to unlock a handset provide theirIMEInumber and sometimes also country and operator details to the company, either via email or a website. The company will then provide the unlock code for the handset. For some brands such as Nokia and Samsung various services also offer special remote-unlocking software with instructions, where a cable is needed to remove the SIM lock at home. Such companies may email the unlocking code or software which will remotely unlock the device. Some companies also offer unlocking services that require sending the handset's IMEI number. Other companies sell unlocking hardware, including devices which fit between the SIM card and the phone to spoof the original network identifier during registration and devices to read and edit the handset's firmware. The pricing for unlocking a device will vary depending on the network it is locked to and the handset model itself, as each unlock code is unique to each individual handset.
There are online services that will provide an IMEI unlocking service forDCT4 and DCT3 Nokiamobile phones.[citation needed]This method of unlock requires the user to know which carrier the mobile phone is locked to, and also needs to provide an IMEI. Generally, older model Nokia unlock codes are free and instantly retrievable by these services. The unlock codes retrieved must be entered into the mobile phone using the keypad.
ForDCT4 and DCT3 Nokia, unlock codes consist of a "#" key, followed by "pw+", 10 (DCT3) or 15 (DCT4) digits, "+", and another number ranging from 1-7, and finally ends with a "#". Depending on the carrier which the phone is locked to, only some codes will work with the mobile phone. Most phones respond to the unlock codes ending in +1# or +7#, however some phones are configured to allow only one of the seven codes to work. The following is an example of a DCT4/DCT3 unlock code:
DCT4 and DCT3 Nokia will only allow a maximum of five unlock attempts using the unlock code method. After five incorrect codes have been inputted, the phone will not allow the user to try any more codes (even if it is correct) and will require the owner to try other unlock methods.
Many countries listed below have some form of SIM-locking laws specifying the period of SIM locking and the cost of obtaining unlocking codes.
InAndorra, the state-owned communications mobile company Mobiland does not sell SIM-locked phones. As there is no competition, consumers usually buy standard mobile phones that are not locked to any specific carrier.[citation needed]
InAustria, unlocking is allowed at any time by the owner of the device. A lawsuit was decided in favor of a mobile operator who encouraged the unlocking of phones by providing links to free/cheap unlocking services.[14]
T-Mobile Austria charges 150 euros to unlock the iPhone for prepaid subscribers and in contract subscribers. For subscribers who have finished their 2-year iPhone contract, T-Mobile Austria charges 50 euros to unlock the iPhone.[15]
InAustralia, carriers can choose whether to SIM/Network Lock handsets or not, however in practice, is rarely performed except in limited cases. Almost all handsets available on the Australian market have no such restriction.[citation needed]
One law professor, Dale Clapperton, gave a talk stating that bundling iPhone and mobile phone service could be violating the Trade Practices Act.[16]However, no other legal professional or academic has come out in support of this viewpoint.[17]This also doesn't address SIM lockingper se, only as applied to subsidised iPhone purchases, and persistence of the lock beyond the contractual period.[citation needed]
Until 2007,Belgiumhad laws prohibiting bundling, but they were challenged as violating EuropeanDirective 2005/29/EC The Unfair Commercial Practices Directive. On April 23, 2009, theEuropean Court of Justiceruled against Belgium and struck down Belgium's anti-bundling law.[18]The Belgian government was given until May 2009 to change the law, failing which the European Commission would commence proceedings against Belgium.[citation needed]This leaves Canada, China, Singapore, and Israel as the only countries in the world that forbid SIM locking and contract/phone bundling outright.[19][5]Chile initiated a ban as of January 1, 2012.
InBrazil, SIM locks are not prohibited. However, the mobile carrier must inform the consumer of the existence of a SIM lock. Anatel, Brazil's telecom regulator, requires the carrier to unlock free of charge the mobile phone if required by the user. After this regulation most telecom operators started voluntarily unlocking the devices as soon as it was purchased so one could leave the store with an unlocked phone.[20]
Under revisions to theCanadian Radio-television and Telecommunications Commission(CRTC) Wireless Code of Conduct effective 1 December 2017, all new devices must be sold unlocked, and carriers must offer to unlock phones purchased prior to this date free of charge.[5]Fees may be required if the customer was not under a contract or prepaid plan with the carrier.[21]
After the implementation of this rule,Bell Canadainitially refused to offer unlocks for users who were not customers of the carrier (in contrast toRogersandTelus Communications), but reversed course in February 2018 due to public backlash.[22][23]In a filing to the CRTC in August 2018, Bell also stated that it had begun to reimplement SIM locks on unsold phones as an anti-theft and safety measure (the phones are unlocked during the activation process when sold to a customer), citing increases in theft from store stocks since the implementation of the prohibition.[24]
Under the original version of the Wireless Code implemented 2013, carriers were required to offer unlocks no later than 90 calendar days from the start of a contract for subsidized devices, or immediately upon purchase of an unsubsidized device. The Code, however, did not expressly prohibit carriers from charging an unlock fee.[5][25]
Prior to the introduction of the Wireless Code,New Democratic PartyMPBruce Hyerfirst attempted to mandate SIM unlocking at the end of cell phone contracts when he introduced aprivate member's billentitled theCell Phone Freedom Actin 2010. The act would not have banned SIM locking but would have required wireless carriers to unlock phones at no charge at the end of a cell phone contract. The bill was introduced in two sessions of parliament but failed to pass either time.[citation needed]
Under a regulation enacted by the Ministry of Industry and Information Technology, locking phones to a specific carrier is prohibited if other carriers are also using the same type of network technology. Therefore, all phones approved to be sold in China are never locked to begin with regardless of whether the consumer purchased the phone under a contract or not. However, since all three Chinese carriers each uses a different network technology after the adoption of 3G, carriers started to ask phone manufacturers to disable support for network technologies not used by such carrier even if the phone has been originally designed to be capable of supporting those network technologies. Such a move does not result in violation of the ban on phone locking. For example, an iPhone 6 was designed to be capable of supporting LTE FDD, LTE TD, CDMA, andWCDMAtechnologies but China Mobile reached a deal with Apple to create a special model for China Mobile in addition to the off-contract retail model sold by Apple and third party vendors with the capability to support LTE FDD, CDMA, WCDMA, which are the technologies not used by China Mobile, disabled, effectively making such special contract model incompatible with the 3G and 4G networks of other carriers even though such phones are never locked.[citation needed]
Starting October 1, 2011, all the mobile telephone services providers, must sell to all users unlocked devices and provide free of charge support to unlock previously sold devices. This regulation was ordered to enablemobile number portabilityand to facilitate the reduction on costs ordered simultaneously.[26]
Since 1 January 2012, newly sold phones must be unlocked. Previously bought locked phones had to be unlocked for free. The regulation was put in place in order to implementmobile number portability.[6]However, the law only requires phones to be usable with all Chilean providers. It does not cover international unlocking for use outside Chile, so users may have to pay for the unlocking service.[citation needed]
A new related issue is present since 23 September 2017, every IMEI have to be registered so the phone works in the country. For local carriers, they do the process, but to use a phone from outside the country, each user has to register it.IMEI Registration.[27]
InCroatia, for devices bought on contract, the mobile operator must provide the unlock code on the user's request free of charge. Such request can be made immediately after buying the phone, and the operator has a 15-day period to fulfill the request. For devices bought on a prepaid plan, the user has to wait at least 12 months before submitting such request.[28]
The carrier can choose to bind contracts up to 6 months from the contract's start. Many of the carriers choose not to lock the phones. Only Hi3G ("3") lock their phones, but can only do so for six months.[29]If the phone needs to be unlocked within the first six months, the carrier can charge DKK 500 (~ €67)[29]for the unlock. After six months, the carrier is obliged by law to unlock the phone free of charge. But the consumer needs to contact the original supplier, and provide the IMEI and original phone number for which the phone was sold.[citation needed]
Although there is no specific law preventing SIM locking, as of December 2009Ecuador's two biggest carriers,PortaandMovistar, unlock phones previously sold by them, without charge.[30]
Countries in theEuropean Union(EU) each have their own legislation on SIM locking, but must comply with the EUUnfair Commercial Practices Directive(Directive 2005/29/EC of 2005). As noted above, this directive has been successfully applied in Belgium to overturn that country's previous ban on bundling phones with contracts. However, carriers in many countries in the EU do not necessarily associate a phone's SIM lock status to the customer's tie-in contract status.
InFinland, carriers are not allowed to sell SIM-locked GSM phones, nor are they allowed to offer tie-in sales on GSM equipment. Under Finnish law, a tie-in sale is defined as selling the equipment for a discounted price contingent on the consumer also acquiring a new service contract from the seller. Under the terms of a provisional exception, valid from 2006 until 2009, tie-in sales were permitted with 3G handsets, and 3G equipment which is purchased under such tie-in sales may be SIM-locked. The SIM lock must be removed free of charge at the conclusion of the tie-in contract, within a maximum duration of 2 years.[31]In 2008, the Finnish government was preparing to extend the exception, and at the same time, was considering reducing the duration of tie-in contracts to one year.[32]
InFrance, SIM locks are not prohibited. However, the mobile operator must inform the consumer of the existence of a SIM lock, and the subscriber has the right to request that the lock be removed at any time. No later than three months after the subscription of the contract, the mobile operator must "systematically and free of charge" provide the subscriber with a procedure to deactivate the SIM lock. Proposal to shorten the time that operators may charge a fee for removing the SIM lock prior from six-month to the three-month deadline.[33]
InGermany, there does not appear to be any effective law regulating SIM locking.[original research?]For example, the iPhone was initially offered for sale in Germany exclusively through T-Mobile, and it was locked to T-Mobile's network. They began to provide unlocking codes for that phone after they were sued by Vodafone and a temporary injunction was issued requiring T-Mobile to do so. Vodafone's injunction was later overturned, and the iPhone is again available exclusively locked to T-Mobile.[34]While T-Mobile Germany told the court that they would unlock the iPhone after the contract, they were doing it voluntarily.[citation needed]
While SIM locking is legal, a court ruled in 2012 that providers must clearly inform potential customers about the SIM lock.[35]
As of 2015, usually only prepaid mobile phones are sold with a SIM lock. Phones sold with a contract stipulating monthly payments are not typically locked (as the monthly payments are due no matter what network the phone is used on). Also, most providers will unlock the phone on demand. Usually a fee is charged during the first two years after purchase; afterwards the unlocking is free. As of 2022, new phones are rarely distributed with a SIM lock;[36]old phones however may still be locked.
InHonduras, there is a general law applicable to all consumer relations engaged in the national territory and provided by natural or legal persons, public or private. This law is called "Ley de Proteccion al Consumidor"[37]or "Consumer Protection Act of Honduras", approved by Legislative Decree No.24-2008, and it regulates the activities of any goods and services providers stating the principles that they must follow in order to operate in this country.
Article 20 of this law states the prohibitions that sellers are obliged to abide when selling a good or providing a service to people. Paragraph 7 of this article states that it is prohibited to a provider to "place seals, adhesives, duct tapes or analogous mechanisms, which prevent the consumer to make free use of the product, except those mechanisms used by the manufacturer for warranty purposes".
Even though the existence of this law, local carriers continue to apply SIM restrictions to the phones they sell. For example, the iPhone is sold by Claro in Honduras and is SIM-locked.[38]which suggests that this generalconsumer protectionlaw does not prohibit SIM locking of cell phones[39]
InHong Kong, carriers are not allowed to SIM-lock a phone for the sole purpose of tying customers to their network. But Hong Kong carriers can SIM-lock a phone to protect the handset subsidy, to enforce mobile plan contracts or to protect from theft.[40]After the initial purchase subsidy has been recovered, or the full cost of the equipment has been paid up under a rental or installment agreement, the carrier must provide a detailed procedure for unlocking the equipment free of charge upon request.[citation needed]
SIM locking is not common inIndia. Initially, each state in India had a differentmobile network operatorandroamingacross states was prohibitive. It was cheaper to change theSIM cardthan pay high roaming charges. The number of inter-state travelers demanded unlocked phones. Usually, phones and SIM cards are sold separately. Mobile phone manufacturers sell phones directly to customers rather than through network operators.Dual SIMphones are quite common in use, with users choosing to make calls using a cheaper operator suitable for the particular call and time of the day from a Dual SIM phone without even switching it off. This along with other factors, encouraged competition among network operators and brought down the mobile phone call charges in from the initial₹32 (US$0.75) in 1996 to₹0.50 (US$0.005 approx.) in 2011. The rates still differ from one service provider to another and across different tariff schemes provided by the same operator.Telecom Regulatory Authority of India(TRAI) is the independentregulatorof thetelecommunicationsbusiness inIndia,[41]established to check call rates and resolve all communication related issues and holds the upper hand in fixing call rates.
According to the Arrangements Law passed on December 29, 2010,Israelicarriers are banned from locking handsets sold by them, and are obligated to unlock any handset previously sold at no charge.[7]
Italyhas SIM locking laws requiring that carriers must specify the amount of subsidies, and allow subscribers to obtain unlocking codes after nine months by paying half of the listed subsidies. After 18 months, the SIM lock must be removed.[42]
Japan'sMinistry of Internal Affairs and Communicationshas legislated that all smartphones and tablets released after May 1, 2015, byNTT DoCoMo,au/Okinawa CellularandSoftBank Mobile(the three major carriers in Japan) must be sold without a SIM lock upon request from customers and without any cost to the customer involved. Before that, from 2011 until 2015, only NTT DoCoMo and au/Okinawa Cellular would remove the SIM lock from phones with a SIM unlock function after the phone is kept or used at least six months after purchase.[43]
InMonaco, the partially state-owned communications mobile companyMonaco Telecomdoes not sell SIM-locked phones. As there is no competition, consumers usually buy standard mobile phones that are not locked to any specific carrier.
Dutchmobile carriers have an agreement[44]with the Netherlands' telecom regulator,OPTA, to establish a code of conduct[45]with respect to SIM locking — specifically, unlocking fees can be charged within the first 12 months and SIM lock cannot last longer than 12 months.[46]
In a 2002 letter to the Dutch Secretary of State of Economic Affairs, OPTA stated that the telecom regulator has decided to start working on the formalization of the voluntary code of conduct into legislation.[47]However, a 2006 report written by the Dutch Ministry of Economic Affairs,[48]stated that competition in the Dutch mobile market is sufficient and the formalization of the voluntary code of conduct into legislation is not needed. Thus there are no SIM locking laws in the Netherlands.[49]
Locking was planned inNew Zealandbefore May 2008[50]whenVodafone New Zealandannounced they would begin locking handsets. The company had planned to charge $50 to unlock them, but then relented. It is speculated that the intention to lock was prompted byTelecom New Zealandbuilding their new mobile network based onUMTStechnology, allowing handsets to change networks for the first time. Until that point in time, Telecom's network (the only other mobile network at that time) was based on CDMA technology, meaning that it was not possible to change networks.2degreeswere also building a mobile network based on UMTS at this time.
After pressure from theCommerce Commission, Vodafone relented on its locking policy, and will unlock any locked phones for free once they have been owned for nine months. You can pay to have it unlocked prior to this.[51][52]
Following speculation of a new lower cost, MNVO of Telecom XT details were leaked regarding theSkinny MobileNetwork, which would SIM lock handsets.
As of 2015, Vodafone, Spark, Skinny, and 2Degrees all charged a $30 unlock fee for phones owned for less than 9 months.
As of 2020, Spark charges a $30 unlock fee for phones owned for less than 9 months, unless the customer is on a Pay Monthly 24 Month Plan.
2Degrees dropped its fees for unlocking phones.[53]
Phones sold with a subscription are usually SIM locked to Norwegian carriers. The fee varies depending on how long it has been since you purchased your mobile phone. After 12 months, you can enter the operator lock code yourself without paying for it.[citation needed]
Ufone has started SIM Locking with the release of its new smartphone named Smart U5 developed by Emitac Services, UAE. U5 comes SIM locked to Ufone only. No other SIM can be used on the U5.[citation needed]
According to OSIPTEL Peru's telecom regulator, article 23 of the Terms of use, mobile carriers can sell phones locked for a lower price for 12, 18 or 24-month contracts, but also must sell unlocked devices for the full price. The same article dictates the customer can request the unlock code for free after 12 months from the purchase date, no matter if the contract is still in place. The sole exception is if the customer cancels the contract before its end and pays the remaining cost, at which point the customer can request the device be unlocked at any time. OSIPTEL plans to reduce the time customers must wait to remove their SIM locks to 6 months.
A 2006 study sponsored by thePortugalregulator,ANACOM, on handset subsidies and SIM locking concluded that there are no special regulatory concerns on offering subsidized SIM-locked equipment in exchange for signing a contract tying a customer to a particular network. Network providers are allowed to apply SIM locks as they see fit, and they may voluntarily remove them if they choose to do so. In the paper, the author stated that the average unlocking fee charged by Portuguese carriers is 90-100 euros.[54]A recently approved law[55]requires network operators to unlock a device free of charge if the respective contract has already expired (But they refuse to do so charging at least 10 euros). It also establishes limits to the fees that operators may charge to unlock a device while it is still under contract.
Romaniantelecom regulator ANCOM signed a code of conduct with several Romanian carriers providing that as of September 1, 2009 mobile operators selling handsets locked within their own network have to inform clients whether the handset is locked and provide unlocking upon request. It is "self-regulation" by the carriers to prevent the regulator from actually imposing regulations on them. If the handset is not purchased together with other electronic communications services, the mobile telephony operator that sells it will bear the unlocking costs and will not bind the terminal unlocking by the purchase of other services or by the payment of other fees.[citation needed]
If the handset is purchased as part of a promotional package or at a preferential price and the customer requires the unlocking before the expiry of the minimum period provided in the contract for communications services concluded with the operator, the customer will have to pay both the unlocking fee and the penalty for the anticipated unlocking of the handset. The price charged to unlock handsets will not exceed the costs of this operation and operators are obliged to meet unlocking requests within 15 days.[56]
SIM locking is not common in Russia, but they have huge potentials to sell unlocked phones. Most mobile phones sold in Russia doesn't have extensive bundlings, customizations as well as the carrier-specific bloatware.Beeline-branded phones are always locked to their network operator.[citation needed]
In telecommunication contracts it is frequent the practice to lock the use of a sim card of one operator with a phone acquired through the same mobile operator. Obstructing the unlocking of the phone may be illegal if the consumer is entitled to it.[citation needed]
In 1997,Singapore's then-telecommunications regulator, Telecommunication Authority of Singapore (nowInfocomm Media Authority of Singapore) enforced a legislation where telcos (Singtel,StarHub,M1,Circles.Life,MyRepublic,TPG Telecomand Zero1) are not allowed to SIM-lock devices, such as phones, tablets and smartwatches that are imported and sold in Singapore.[57][58]In August 1997, TAS warned at least one operator,M1, for selling SIM-locked phones.[59]
In 1998, the then-Spanishtelecom regulator,Tribunal de Defensa de la Competencia(nowComisión Nacional de los Mercados y la Competencia), saw that Spanish mobile carriers already provided unlocking codes voluntarily for a fee within the first 12 months and for free after 12 months, so it decided not to establish any legal framework in Spain.[60]CMT has not revisited this decision since then, therefore there are no SIM-locking laws in Spain.
In Sweden, carriers are required to unlock handsets after 12 months since purchase. This applies both to on-contract and pay as you go phones. All carriers will charge a fee of 300 SEK (approximately $45) or 350 SEK (approximately $50), depending on carrier, to unlock the handset. However, as of 2016, most carriers have stopped locking phones altogether.[citation needed]
SIM locking may be particularly common in Switzerland. Swisscom began lifting SIM lock since July 2013. Sunrise prepaid mobile phones have a SIM lock for 2 years from purchase.[citation needed]
Thailandis also another country that forbids outright SIM locking and as a result, no phones are sold in the market are subsidized by carriers. Up until recently mobile phone manufacturers have their own store fronts and mobile carriers are only the service providers.[citation needed]
SIM locking is forbidden by theregulatory authorityin Turkey since 2013.[61][62]There are conflicting and varying reports about former practices of SIM locking by operators. A newspaper column from 1997 criticizesTelsim'sSIM locking policy: "... you cannot quit Telsim until the phone becomes waste, the only way to quit Telsim is buying a new phone."[63]Turkcell'sSIM locking policy has been subject to a lawsuit in 2001, resulting in Turkcell being fined.[64]BlackBerryphones sold by Turkcell and Vodafone were SIM locked, however, could be unlocked on request without any conditions.[65]Yet, the SIM locking practice was only confined to phones sold by operators and it is not clear if operators enforced SIM locking on the phones sold by them tightly or not and if the practice was widespread. Phones sold by other channels were strictly unlocked. Three major mobile network operators, Turkcell, Türk Telekom and Vodafone still offer phones with long term contracts, however these phones are sold unlocked.[citation needed]
In theUnited Kingdom, mobile phone network providers are not obliged to provide unlocking, even after the end of the contract.Ofcom, UK's telecom regulator, allowed3to sell a mobile phone with the SIM card permanently superglued to the phone.[66]Most operators offer some form of unlocking service, depending on the state of the contract and the model of phone, but usually for a charge. The fullOftel2002 SIM-lock position paper specifies that there is no SIM-locking law in the UK; the regulator wants only "consumer awareness". The examples within the position paper are just "examples" of current carrier practices for illustration purposes, but do not reflect any official Oftel regulation.[67]The main networks often agree to unlock handsets for a charge, either at the end of a contract or, for prepaid handsets, after several months. Some Blackberry handsets supplied byVodafone(e.g.,Storm)[68]are examples of a UK carrier not offering unlocking codes. As of April 2011O2will unlock any of their pay-monthly phones for free, even if they're still in contract, with the exception of handsets made exclusively for them, such as their Palm devices.[69]Carphone Warehouse, one of the largest UK phone retailers, offers unlocked phones with most PAYG deals.[citation needed]As of January 1, 2014, all phones sold by 3 UK are unlocked. Phones bought before this date will be unlocked for free.[70]
On 17 December 2019, Ofcom announced that it would explore a mandate banning SIM locking.[71]On 27 October 2020, The UK's mobile networks are to be forbidden from selling phones locked to their services from December 2021.[72]
One of the twoAmericanGSM carriers,T-Mobile,[73]will unlock handsets for those with active account in good standing for at least 40 days and no unlock code request in the last 90 days. The other,AT&T Mobility, is required to do so upon request (with some exceptions and requirements) after ninety days of active service under the terms of aclass actionsettlement.[74]Prior to the settlement, AT&T would[75]usually do so once one has concluded their contract, and in some other situations. AT&T had in the past stated that it would not unlock iPhones under any circumstances, regardless of the legality of doing so, even after customers are out of contract. However, AT&T has since announced that starting April 8, 2012, it will begin unlocking off-contract iPhones, provided that the customer's account is in good standing.[76]AT&T also has an unannounced policy of unlocking iPhones forUnited States service memberswho are deployed overseas—even if they are still under contract.[77]
Before carriers began voluntarily providing unlock codes for all phone models, in 2010 theElectronic Frontier Foundation(EFF) successfully convinced theUnited States Copyright Officeto allow an exemption to the general prohibition on circumvention of copyright protection systems under theDigital Millennium Copyright Act of 1998for unlocking of phones through user self-help (sometimes referred to as "hacking").[78]This exemption has become less important now that most carriers are voluntarily providing unlock codes.
According to a ruling effective October 28, 2012, it will be illegal to unlock phones purchased 90 days after this date or later without the carrier's permission.[79]In other words, users can already unlock phones they already own, and phones purchased before January 29, 2013, but phones purchased after this point can only be unlocked with the carrier's permission.
In March 2013, theObama administrationand theFederal Communications Commissionsaid consumers should also be able to switch carriers and keep their actual phones.[80]
On August 1, 2014, President Obama signed into law theUnlocking Consumer Choice and Wireless Competition Act (S. 517; 113th Congress), a bill legalizing unlocking cellphones in the US.[81][82]The bill passed in theUnited States Senateon July 15, 2014, and in theUnited States House of Representativeson July 25, 2014.
Sprintagreed to allow domestic unlocking on all mobile devices launched after February 15, 2015.[83]
It is possible to buy unlocked phones in the U.S. Some online retailers sell phones that come unlocked from the manufacturer, that is, they were never locked in the first place.[citation needed]
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TheInternational Mobile Equipment Identity(IMEI)[1]is a numericidentifier, usuallyunique,[2][3]for3GPPandiDENmobile phones, as well as somesatellite phones. It is usually found printed inside the battery compartment of the phone but can also be displayed on-screen on most phones by entering theMMI Supplementary Service code*#06#on the dialpad, or alongside other system information in the settings menu on smartphone operating systems.
GSMnetworks use the IMEI number to identify valid devices, and can stop a stolen phone from accessing the network. For example, if amobile phoneis stolen, the owner can have their network provider use the IMEI number to blocklist the phone. This renders the phone useless on that network and sometimes other networks, even if the thief changes the phone'sSIMcard.
Devices without a SIM card slot oreSIMcapability usually do not have an IMEI, except for certain earlySprintLTEdevices such as theSamsungGalaxy NexusandS IIIwhich emulated a SIM-freeCDMAactivation experience and lacked roaming capabilities in3GPP-only countries.[4]However, the IMEI only identifies the device and has no particular relationship to the subscriber. The phone identifies the subscriber by transmitting theInternational mobile subscriber identity(IMSI) number, which is stored on a SIM card that can, in theory, be transferred to any handset. However, the network's ability to know a subscriber's current, individual device enables many network and security features.[citation needed]
Dual SIM enabled phones will normally have two IMEI numbers, except for devices such as thePixel 3(which has an eSIM and one physical SIM) which only allow one SIM card to be active at once.
Many countries have acknowledged the use of the IMEI in reducing the effect of mobile phone thefts. For example, in theUnited Kingdom, under the Mobile Telephones (Re-programming) Act, changing the IMEI of a phone, or possessing equipment that can change it, is considered an offence under some circumstances.[5][6]A bill was introduced in the United States by SenatorChuck Schumerin 2012 that would have made the changing of an IMEI illegal, but the bill was not enacted.[7]
IMEI blocking is not the only way to fight phone theft. Instead, mobile operators are encouraged to take measures such as immediate suspension of service and replacement of SIM cards in case of loss or theft.[8]
The existence of a formally allocated IMEI number range for a GSM terminal does not mean that the terminal is approved or complies with regulatory requirements. The linkage between regulatory approval and IMEI allocation was removed in April 2000, with the introduction of the European R&TTE Directive.[9]Since that date, IMEIs have been allocated byBABT(or one of several other regional administrators acting on behalf of theGSM Association) to legitimate GSM terminal manufacturers without the need to provide evidence of approval.
When someone has their mobile equipment stolen or lost, they can ask their service provider to block the phone from their network, and the operator may do so, especially if required by law. If the local operator maintains an Equipment Identity Register (EIR), it adds the device IMEI to it. Optionally, it also adds the IMEI to shared registries, such as theCentral Equipment Identity Register(CEIR), which blocklists the device with other operators that use the CEIR. This blocklisting makes the device unusable on any operator that uses the CEIR, which makes mobile equipment theft pointless, except for parts.
To make blocklisting effective, the IMEI number is supposed to be difficult to change. However, a phone's IMEI may be easy to change with special tools.[10][better source needed]In addition, IMEI is an un-authenticated mobile identifier (as opposed to IMSI, which is routinely authenticated by home and serving mobile networks.) Using a spoofed IMEI can thwart some efforts to track handsets, or target handsets for lawful intercept.[citation needed]
Australia was the first nation to implement IMEI blocking across all GSM networks, in 2003.[11]In Australia the Electronic Information Exchange (EIE) Administration Node provides a blocked IMEI lookup service for Australian customers.[12]
In the UK, a voluntary charter operated by the mobile networks ensures that any operator's blocklisting of a handset is communicated to the CEIR and subsequently to all other networks. This ensures that the handset is quickly unusable for calls, at most within 48 hours.
Some UK Police forces, including theMetropolitan Police Service, actively check IMEI numbers of phones found involved in crime.
In New Zealand, the NZ Telecommunications Forum Inc[13]provides a blocked IMEI lookup service for New Zealand consumers. The service allows up to three lookups per day[14]and checks against a database that is updated daily by the three major mobile network operators. A blocked IMEI cannot be connected to any of these three operators.
In Latvia the SIA "Datorikas institūts DIVI"[15]provides a blocked IMEI lookup service for checks against a database that is updated by all major mobile network operators in Latvia.
In some countries, such blocklisting is not customary. In 2012, major network companies in the United States, under government pressure, committed to introducing a blocklisting service, but it's not clear whether it will interoperate with the CEIR.[16][17]GSM carriers AT&T and T-Mobile began blocking newly reported IMEIs in November 2012.[18]Thefts reported prior to November 2012 were not added to the database. TheCTIArefers users to websites atwww.stolenphonechecker.org[19]andthe GSMA[19]where consumers can check whether a smartphone has been reported as lost or stolen to its member carriers. The relationship between the former and any national or internationalIMEI blocklistsis unclear.[19]
It is unclear whether local barring of IMEI has any positive effect, as it may result in international smuggling of stolen phones.[20]
IMEIs can sometimes be removed from a blocklist, depending on local arrangements. This would typically include quoting a password chosen at the time of blocklisting.[citation needed]
Law enforcement and intelligence services can use an IMEI number as input for tracking devices that are able to locate a cell phone with an accuracy of a few meters. Saudi Arabian government agencies have reportedly used IMEI numbers retrieved from cell phone packaging to locate and detain women who fled Saudi Arabia's patriarchal society in other countries.[21]
An IMEI number retrieved from the remnants of aNokia 5110was used to trace and identify the perpetrators behind the2002 Bali bombings.[22]
Some countries use allowlists instead of blocklists for IMEI numbers, so that any mobile phone needs to be legally registered in the country in order to be able to access mobile networks of the country, with possible exceptions for international roaming and a grace period for registering.[23]These include Chile,[24]Turkey,[25]Azerbaijan,[26]Colombia,[27]and Nepal.[28]Other countries that have adopted some form of mandatory IMEI registration include India, Pakistan, Indonesia, Cambodia, Thailand, Iran, Nigeria, Ecuador, Ukraine, Lebanon,[29]and Kenya.[30]
Prior to their merger withT-Mobile,Sprintin the United States used an allowlist of devices where a user had to register their IMEI and SIM card before aLTE-capable device could be used, despite noUSlaw mandating it.[31]If a user changed their device, they had to register their new IMEI and SIM card. This isn't the case with other CDMA carriers likeVerizonwhich only used allowlists for 3G (which was a requirement for CDMA) and T-Mobile does not use an allowlist but instead a blocklist, including for former Sprint customers.
AT&T[32]andTelus[33]also use an allowlist forVoLTEaccess, but does not require IMEI registration by customers. Instead, phone manufacturers are required to register their devices into AT&T's or Telus' databases, and customers are able to freely swap SIM cards or eSIMs into any allowlisted device. This has the problem that imported phones and some non-imported phones such as olderOnePlusmodels or selectCDMA-capable LTE devices (including models sold onVerizonorSprint) will not work for voice calls even if they have the LTE/5G bands for AT&T and Telus and support VoLTE on competitors or via VoLTE roaming.
The IMEI (15 decimal digits: 14 digits plus a check digit) or IMEISV (16 decimal digits: 14 digits plus two software version digits) includes information on the origin, model, and serial number of the device. The structure of the IMEI/SV is specified in3GPP TS 23.003. The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as theType Allocation Code(TAC). The remainder of the IMEI is manufacturer-defined, with aLuhn check digitat the end. For the IMEI format prior to 2003, the GSMA guideline was to have this Check Digit always transmitted to the network as zero. This guideline seems to have disappeared for the format valid from 2003 onwards.[34]
As of 2004[update], the format of the IMEI isAA-BBBBBB-CCCCCC-D, although it may not always be displayed this way. The IMEISV does not have the Luhn check digit but instead has two digits for the Software Version Number (SVN), making the formatAA-BBBBBB-CCCCCC-EE
Prior to 2002, the TAC was six digits and followed by a two-digitFinal Assembly Code(FAC), which was a manufacturer-specific code indicating the location of the device's construction.
From January 1, 2003 until April 1, 2004, theFACfor all phones was 00.
After April 1, 2004, the Final Assembly Code ceased to exist and the Type Allocation Code increased to eight digits in length.
In any of the above cases, the first two digits of the TAC are theReporting Body Identifier, which identifies the GSMA-approved group that allocated the TAC. The RBI numbers are allocated by the Global Decimal Administrator. IMEI numbers being decimal helps distinguish them from anMEID, which is hexadecimal and always has 0xA0 or larger as the first two hexadecimal digits.
For example, the old style IMEI code 35-209900-176148-1 or IMEISV code 35-209900-176148-23 tells us the following:
TAC: 35-2099 - issued by theBABT(code 35) with the allocation number 2099FAC: 00 - indicating the phone was made during the transition period when FACs were being removed.SNR: 176148 - uniquely identifying a unit of this modelCD: 1 so it is a GSM Phase 2 or higherSVN: 23 - The "software version number" identifying the revision of the software installed on the phone. 99 is reserved.
By contrast, the new style IMEI code 49-015420-323751-8 has an 8-digit TAC of 49-015420.
The CDMAMobile Equipment Identifieruses the same basic format as the IMEI but gives more flexibility in allocation sizes and usage.
The last number of the IMEI is acheck digit, calculated using theLuhn algorithm, as defined in theIMEI Allocation and Approval Guidelines:
The Check Digit shall be calculated according toLuhn formula(ISO/IEC 7812). (See GSM 02.16 / 3GPP 22.016). The Check Digit is a function of all other digits in the IMEI. The Software Version Number (SVN) of a mobile is not included in the calculation.
The purpose of the Check Digit is to help guard against the possibility of incorrect entries to the CEIR and EIR equipment.
The presentation of the Check Digit both electronically and in printed form on the label and packaging is very important. Logistics (using bar-code reader) and EIR/CEIR administration cannot use the Check Digit unless it is printed outside of the packaging, and on the ME IMEI/Type Accreditation label.
The check digit is not transmitted over the radio interface, nor is it stored in the EIR database at any point. Therefore, all references to the last three or six digits of an IMEI refer to the actual IMEI number, to which the check digit does not belong.
The check digit is validated in three steps:
Conversely, one can calculate the IMEI by choosing the check digit that would give a sum divisible by 10. For the example IMEI 49015420323751?,
To make the sum divisible by 10, we setx= 8, so the complete IMEI becomes 490154203237518.
IMEI validation[35]is the process of verifying the authenticity and integrity of a mobile device’s 15-digitIMEInumber, ensuring it conforms to global registry standards and has not been tampered with. An IMEI consists of four parts: theType Allocation Code(TAC), which identifies the device model; theFinal Assembly Code(FAC), denoting the manufacturing site; theSerial Number(SNR), unique to each unit; and theCheck Digit, calculated via theLuhn algorithm. During validation, the first 14 digits are processed through the Luhn checksum procedure and compared to the Check Digit—any mismatch indicates an invalid or forged IMEI. Widely employed byGSMnetwork operators, regulatory agencies, and anti-theft platforms, IMEI validation helps combat device cloning, unauthorized resale, and mobile phone theft, while maintaining network security and consumer trust.
TheBroadband Global Area Network(BGAN),IridiumandThurayasatellite phonenetworks all use IMEI numbers on their transceiver units as well as SIM cards in much the same way as GSM phones do. The Iridium 9601 modem relies solely on its IMEI number for identification and uses no SIM card; however, Iridium is a proprietary network and the device is incompatible with terrestrial GSM networks.
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In telecommunication, apublic land mobile network(PLMN) is a combination of wireless communication services offered by a specific operator in a specific country.[1][2]A PLMN typically consists of several cellular technologies likeGSM/2G,UMTS/3G,LTE/4G, NR/5G, offered by a single operator within a given country, often referred to as acellular network.
A PLMN is identified by a globally unique PLMN code, which consists of aMCC (Mobile Country Code) and MNC (Mobile Network Code). Hence, it is a five- to six-digit number identifying a country, and a mobile network operator in that country, usually represented in the form 001-01 or 001–001.
A PLMN is part of a:
Note that an MNC can be of two-digit form and three-digit form with leading zeros. It is administered by the respective national numbering plan administrator.[3]From PLMN assignments, it is apparent that such dualities of two-digit and three-digit MNCs with the same number value are avoided (see thelist of mobile country codes and mobile network codes). An example for an actual three-digit/two-digit MNC with leading zeros is inBermuda MCC, 350-007 and 350-00, 350-01.
TheIMSI, which identifies a SIM or USIM for one subscriber, typically starts with the PLMN code. For example, an IMSI belonging to the PLMN 262-33 would look like 262330000000001. Mobile phones use this to detectroaming, so that a mobile phone subscribed on a network with a PLMN code that mismatches the start of the USIM's IMSI will typically display an "R" on the icon that indicates connection strength.
A PLMN typically offers the following services to a mobile subscriber:
The availability, quality and bandwidth of these services strongly depends on the particular technology used to implement a PLMN.
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https://en.wikipedia.org/wiki/PLMN
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Amobile equipment identifier (MEID)is a globally unique number identifying a physical piece ofCDMA2000mobile station equipment. The number format is defined by the3GPP2 report S.R0048but in practical terms, it can be seen as anIMEIbut withhexadecimaldigits.
An MEID is 56bitslong (14 hexadecimal digits). It consists of three fields, including an 8-bit regional code (RR), a 24-bit manufacturer code, and a 24-bit manufacturer-assigned serial number. The check digit (CD) is not considered part of the MEID.
The MEID was created to replaceelectronic serial numbers(ESNs), whose virgin form was exhausted in November 2008.[1]As of TIA/EIA/IS-41 Revision D and TIA/EIA/IS-2000 Rev C, the ESN is still a required field in many messages—for compatibility, devices with an MEID can use a pseudo-ESN (pESN), which is a manufacturer code of 0x80 (formerly reserved) followed by the least significant 24 bits of theSHA-1hash of the MEID.[2]MEIDs are used on CDMA mobile phones. GSM phones do not have ESN or MIN, only an International Mobile Station Equipment Identity (IMEI) number.
Commonly, opening the phone's dialler and typing *#06# will display its MEID.[3]
The separation between international mobile equipment identifiers (IMEIs) used by GSM/UMTS and MEIDs is based on the number ranges. There are two administrators: the global decimal administrator (GDA) for IMEIs and the global hexadecimal administrator (GHA).
As of August 2006, the TIA acts as the GHA to assign MEID code prefixes (0xA0 and up), and the GSM Association acts as the global decimal administrator. TIA also allocates IMEI codes, specifically destined for dual-technology phones, out of the RR=99 range. This range is commonly (but not exclusively) used forLTE-capable handsets with CDMA support. Other administrators working under GSMA may also allocate any IMEI for use in dual-technology phones. For instance,AppleandLGnormally use RR=35 which is allocated byBABTwhileChinesebrands such asHuaweiuse two RR=86 IMEIs allocated by TAF for 3GPP networks alongside a distinct RR=99 decimal or RR=A0 hexadecimal MEID for 3GPP2 networks. Every IMEI can also be used as an MEID in CDMA devices (as well as in single-mode devices designed with GSM or other 3GPP protocols) but MEIDs can also contain hexadecimal digits and this MEID variant cannot be used as an IMEI.
There are two standard formats for MEIDs, and both can include an optional check-digit. This is defined by3GPP2 standard X.S0008.
The hexadecimal form is specified to be 14 digits grouped together and applies whether all digits are in the decimal range or whether some are in the range 'A'–'F'. In the first case, all digits are in the range '0'–'9', the check-digit is calculated using the normal base 10Luhnalgorithm, but if at least one digit is in the range 'A'–'F' this check digit algorithm uses base 16 arithmetic. The check-digit is never transmitted or stored. It is intended to detect most (but not all) input errors, it is not intended to be a checksum or CRC to detect transmission errors. Consequently, it may be printed on phones or their packaging in case of manual entry of an MEID (e.g. because there is nobar codeor the bar code is unreadable).
The decimal form is specified to be 18 digits grouped in a 5–5–4–4 pattern and is calculated by converting the manufacturer code portion (32 bits) to decimal and padding on the left with '0' digits to 10 digits and separately converting the serial number portion to decimal and padding on the left to 8 digits. A check-digit can be calculated from the 18 digit result using the standard base 10Luhnalgorithm and appended to the end. Note that to produce this form the MEID digits are treated as base 16 numbers even if all of them are in the range '0'–9'.
Because the pESN is formed by a hash on the MEID there is the potential for hash collisions. These will cause an extremely rare condition known as a 'collision' on a pure ESN-only network as the ESN is used for the calculation of the Public Long Code Mask (PLCM) used for communication with the base-station. Two mobiles using the same pESN within the same base-station area (operating on the same frequency) can result in call setup and page failures.
The probability of a collision has been carefully examined.[4]Roughly, it is estimated that even on a heavily loaded network the frequency of this situation is closer to 1 out of 1 million calls than to 1 out of 100 000.
3GPP2 specificationC.S0072provides a solution to this problem by allowing the PLCM to be established by the base station. It is easy for the base station to ensure that all PLCM codes are unique when this is done. This specification also allows the PLCM to be based on the MEID orIMSI.
A different problem occurs when ESN codes are stored in a database (such as forOTASP). In this situation, the risk of at least two phones having the same pseudo-ESN can be calculated using thebirthday paradoxand works out to about a 50 per cent probability in a database with 4,800 pseudo-ESN entries. 3GPP2 specificationsC.S0016(Revision C or higher) andC.S0066have been modified to allow the replacement MEID identifier to be transmitted, resolving this problem.
Another problem is that messages delivered on the forward paging channel using the pESN as an address could be delivered to multiple mobiles seemingly randomly. This problem can be avoided by usingmobile identification number(MIN) or IMSI based addressing instead.
This shortPythonscript will convert an MEID to a pESN.
The CDG also provides ajavascript calculator with more conversion options.
This C# method will convert an MEID from HEX to DEC format (or return empty for an invalid MEID HEX value)
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https://en.wikipedia.org/wiki/MEID
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Electronic serial numbers(ESNs) were created by the U.S.Federal Communications Commission(FCC) to uniquely identifymobile devices, from the days ofAMPSin the United States starting in the early 1980s. The administrative role was taken over by theTelecommunications Industry Associationin 1997 and is still maintained by them. ESNs are currently mainly used withCDMAphones (and were previously used byAMPSandTDMAphones), compared toInternational Mobile Equipment Identity(IMEI) numbers used by allGSMphones.[1]
The first eight bits of the ESN were originally the manufacturer code, leaving 24 bits for the manufacturer to assign up to 16,777,215 codes to mobiles. To allow more than 256 manufacturers to be identified, the manufacturer code was extended to 14 bits, leaving 18 bits for the manufacturer to assign up to 262,144 codes. Manufacturer code 0x80 is reserved from assignment and is used instead as an eight-bit prefix for pseudo-ESNs (pESN). The remaining 24 bits are the least significant bits of theSHA-1hash of amobile equipment identifier(MEID). Pseudo-ESNs are not guaranteed to be unique (the MEID is the unique identifier if the phone has a pseudo-ESN).
ESNs are often represented as either 11-digit decimal numbers or 8-digit hexadecimal numbers. For the decimal format the first three digits are the decimal representation of the first eight bits (between 00 and 255 inclusive) and the next eight digits are derived from the remaining 24 bits and will be between 0000000 and 16777215 inclusive. The decimal format of pseudo ESNs will therefore begin with 128. The decimal format separately displays eight bit manufacturer codes in the first three digits, but 14 bit codes are not displayed as separate digits. The hexadecimal format displays an ESN as eight digits and also does not separately display 14 bit manufacturer codes which occupy 3.5 hexadecimal digits.
As ESNs have essentially run out, a new serial number format,MEID, was created by3GPP2and was first implemented by Verizon in 2006. MEIDs are 56 bits long, the same length as the IMEI and, in fact, MEID was created to be a superset of IMEI. The main difference between MEID and IMEI is that the MEID allows hexadecimal digits while IMEI allows only decimal digits – "IMEI shall consist of decimal digits (0 through 9) only".[2]
The last of the previously unused ESN codes were allocated in November 2008.[3]Applications for assignments were accepted until June 30, 2010 using reclaimed ESN codes, those previously assigned toAMPSorTDMAphones and therefore not present onCDMA2000systems. Reclaimed codes have also been used forUIMIDassignments. Codes are assigned according to industry guidelines.[4]
Although ESN assignments may still occur in the future based on applications received before June 30, 2010, there have not been any assignments made since December 31, 2010.
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Aninternational mobile subscriber identity(IMSI)catcher, is atelephone eavesdroppingdevice used for interceptingmobile phonetraffic and tracking location data of mobile phone users.[1]Essentially a "fake"mobile toweracting between the target mobile phone and the service provider's real towers, it is considered aman-in-the-middle(MITM) attack. The3G wireless standardoffers some risk mitigation due to mutual authentication required from both the handset and the network.[2]However, sophisticated attacks may be able to downgrade 3G andLTEto non-LTE network services which do not require mutual authentication.[3]
IMSI-catchers are used in a number of countries bylaw enforcementandintelligence agencies, but their use has raised significant civil liberty and privacy concerns and is strictly regulated in some countries such as under the GermanStrafprozessordnung(StPO / Code of Criminal Procedure).[1][4]Some countries do not have encrypted phone data traffic (or veryweak encryption), thus rendering an IMSI-catcher unnecessary.[citation needed]
A virtualbase transceiver station(VBTS)[5]is a device for identifying thetemporary mobile subscriber identity(TMSI),international mobile subscriber identity(IMSI) of a nearbyGSMmobile phoneandinterceptingits calls, some are even advanced enough to detect theinternational mobile equipment identity(IMEI). It was patented[5]and first commercialized byRohde & Schwarzin 2003. The device can be viewed as simply a modified cell tower with a malicious operator, and on 4 January 2012, theCourt of Appeal of England and Walesheld that the patent isinvalid for obviousness.[6]
IMSI-catchers are often deployed by court order without asearch warrant, the lower judicial standard of apen registerand trap-and-trace order being preferred by law enforcement.[7]They can also be used in search and rescue operation for missing persons.[8]Police departments have been reluctant to reveal use of these programs and contracts with vendors such asHarris Corporation, the maker ofStingrayand Kingfish phone tracker devices.[9]
In the UK, the first public body to admit using IMSI catchers was theScottish Prison Service,[10]though it is likely that theMetropolitan Police Servicehas been using IMSI catchers since 2011 or before.[11]
Body-worn IMSI-catchers that target nearby mobile phones are being advertised to law enforcement agencies in the US.[12]
TheGSMspecification requires the handset to authenticate to the network, but doesnotrequire the network to authenticate to the handset. This well-known security hole is exploited by an IMSI catcher.[13]The IMSI catcher masquerades as abase stationand logs the IMSI numbers of all themobile stationsin the area, as they attempt to attach to the IMSI-catcher.[14]It allows forcing the mobile phone connected to it to use no call encryption (A5/0 mode) or to use easily breakable encryption (A5/1 or A5/2 mode), making the call data easy to intercept and convert to audio.
The3G wireless standardmitigates risk and enhanced security of the protocol due to mutual authentication required from both the handset and the network and removes the false base station attack in GSM.[2]Some sophisticated attacks against 3G andLTEmay be able to downgrade to non-LTE network services which then does not require mutual authentication.[3]
Every mobile phone has the requirement to optimize its reception. If there is more than one base station of the subscribed network operator accessible, it will always choose the one with the strongest signal. An IMSI-catcher masquerades as a base station and causes every mobile phone of the simulated network operator within a defined radius to log in. With the help of a special identity request, it is able to force the transmission of the IMSI.[15]
The IMSI-catcher subjects the phones in its vicinity to aman-in-the-middle attack, appearing to them as a preferred base station in terms of signal strength. With the help of aSIM, it simultaneously logs into the GSM network as a mobile station. Since the encryption mode is chosen by the base station, the IMSI-catcher can induce the mobile station to use no encryption at all. Hence it can encrypt the plain text traffic from the mobile station and pass it to the base station.
A targeted mobile phone is sent signals where the user will not be able to tell apart the device from authentic cell service provider infrastructure.[16]This means that the device will be able to retrieve data that a normal cell tower receives from mobile phones if registered.[16]
There is only an indirect connection from mobile station via IMSI-catcher to the GSM network. For this reason, incoming phone calls cannot generally be patched through to the mobile station by theGSM network, although more modern versions of these devices have their own mobile patch-through solutions in order to provide this functionality.
The difference between a passive IMSI-catcher and an active IMSI-catcher is that an active IMSI-catcher intercepts the data in transfer such as spoke, text, mail, and web traffic between the endpoint and cell tower.
Active IMSI-catchers generally also intercept all conversations and data traffic within a large range and are therefore also called rogue cell towers. It sends a signal with a plethora of commands to the endpoints, which respond by establishing a connection and routes all conversations and data traffic between the endpoints and the actual cell tower for as long as the attacker wishes.
A passive IMSI-catcher on the other hand only detects theIMSI,TMSIorIMEIof an endpoint. Once the IMSI, TMSI or IMEI address is detected, the endpoint is immediately released. The passive IMSI-catcher sends out a signal with only one specific command to the endpoints, which respond to it and share the identifiers of the endpoint with the passive IMSI-catcher. The vendors of passive IMSI-catchers take privacy more into account.
False base station attacks are prevented by a combination of key freshness and integrity protection of signaling data, not by authenticating the serving network.[17]
To provide a high network coverage, theUMTSstandard allows for inter-operation with GSM. Therefore, not only UMTS but also GSM base stations are connected to the UMTS service network. This fallback is a security disadvantage and allows a new possibility of a man-in-the-middle attack.[18]
The assignment of an IMSI catcher has a number of difficulties:
Some preliminary research has been done in trying to detect and frustrate IMSI-catchers. One such project is through theOsmocomopen source mobile station software. This is a special type of mobile phone firmware that can be used to detect and fingerprint certain network characteristics of IMSI-catchers, and warn the user that there is such a device operating in their area. But this firmware/software-based detection is strongly limited to a select few, outdated GSM mobile phones (i.e. Motorola) that are no longer available on the open market. The main problem is the closed-source nature of the major mobile phone producers.
The application Android IMSI-Catcher Detector (AIMSICD) is being developed to detect and circumvent IMSI-catchers by StingRay andsilent SMS.[20]Technology for a stationary network of IMSI-catcher detectors has also been developed.[13]Several apps listed on theGoogle Play Storeas IMSI catcher detector apps include SnoopSnitch, Cell Spy Catcher, and GSM Spy Finder and have between 100,000 and 500,000 app downloads each. However, these apps have limitations in that they do not have access to phone's underlying hardware and may offer only minimal protection.[21]
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Atelephone numberis the address of a telecommunication endpoint, such as atelephone, in a telephone network, such as thepublic switched telephone network(PSTN). A telephone number typically consists of asequence of digits, but historically letters were also used in connection withtelephone exchange names.
Telephone numbers facilitate the switching and routing oftelephone callsusing a system of destination code routing.[1]Telephone numbers are entered or dialed by acalling partyon the originating telephone set, which transmits the sequence of digits in the process of signaling to atelephone exchange. The exchange completes the call either to another locally connected subscriber or via the PSTN to thecalled party. Telephone numbers are assigned within the framework of a national or regionaltelephone numbering planto subscribers by telephone service operators, which may be commercial entities, state-controlled administrations, or othertelecommunicationindustry associations.
Telephone numbers were first used in 1879 inLowell, Massachusetts, when they replaced the request for subscriber names by callers connecting to theswitchboard operator.[2]Over the course oftelephone history, telephone numbers had various lengths and formats and even included most letters of the alphabet in leading positions whentelephone exchange nameswere in common use until the 1960s.
Telephone numbers are often dialed in conjunction with other signaling code sequences, such asvertical service codes, to invoke special telephone service features.[3][4]Telephone numbers may have associated short dialing codes, such as9-1-1(emergency services), which obviate the need to remember and dial complete telephone numbers.
When telephone numbers were first used they were very short, from one to three digits, and were communicated orally to aswitchboard operatorwhen initiating a call. As telephone systems have grown and interconnected to encompass worldwide communication, telephone numbers have become longer. In addition totelephones, they have been used to access other devices, such ascomputermodems,pagers, andfax machines. Withlandlines, modems and pagers falling out of use in favor of all-digital always-connectedbroadband Internetandmobile phones, telephone numbers are now often used by data-onlycellulardevices, such as sometablet computers,digital televisions,video game controllers, andmobile hotspots, on which it is not even possible to make or accept acall.
The number contains the information necessary to identify the intended endpoint for atelephone call. Many countries use fixed-length numbers in a so-calledclosed numbering plan.[5]A prominent system of this type is theNorth American Numbering Plan. In Europe, the development ofopen numbering planswas more prevalent, in which a telephone number comprised a varying count of digits. Irrespective of the type of numbering plan, "shorthand" or "speed calling" numbers are automatically translated to unique telephone numbers before the call can be connected. Some special services have special short codes (e.g.,119,911,100, 101, 102,000,999,111, and112being theemergency telephone numbersin many countries).
The dialing procedures (dialing plan) in some areas permit dialing numbers in the local calling area without using anarea codeor city code prefix. For example, a telephone number in North America consists of a three-digit area code, a three-digit central office code, and four digits for the line number. If the numbering plan area does not use anoverlay planwith multiple area codes, or if the provider allows it for other technical reasons, seven-digit dialing may be permissible for calls within the area.
Special telephone numbers are used for high-capacity numbers with severaltelephone circuits, typically arequest lineto aradio stationwhere dozens or even hundreds of callers may be trying to call in at once, such as for a contest. For each largemetro area, all of these lines will share the same prefix (such as404-741-xxxxin Atlanta and305-550-xxxxinMiami), the last digits typically corresponding to the station'sfrequency,callsign, ormoniker.
In the international telephone network, the format of telephone numbers is standardized byITU-TrecommendationE.164. This code specifies that the entire number should be 15 digits or shorter, and begin with an international calling prefix and acountry prefix. For most countries, this is followed by an area code, city code or service number code and the subscriber number, which might consist of the code for a particulartelephone exchange.ITU-TrecommendationE.123describes how to represent an international telephone number in writing or print, starting with a plus sign ("+") and thecountry code. When calling an international number from a landline phone, the + must be replaced with theinternational call prefixchosen by the country the call is being made from. Many mobile phones allow the + to be entered directly, by pressing and holding the "0" forGSMphones, or sometimes "*" forCDMAphones.
The3GPPstandards for mobile networks provide aBCD-encodedfield of ten bytes for the telephone number ("Dialling Number/SCC String"). The international call prefix or "+" is not counted as it encodes a value in a separate byte (TON/NPI - type of number / numbering plan identification). If theMSISDNis longer than 20 digits then additional digits are encoded into extension blocks (EFEXT1) each having a BCD-encoded field of 11 bytes.[6]This scheme allows to extend the subscriber number with a maximum of 20 digits by additional function values to controlnetwork services. In the context ofISDNthe function values were transparently transported in a BCD-encoded field with a maximum of 20 bytes named "ISDN Subaddress".[7]
The format and allocation of local telephone numbers are controlled by each nation's respective government, either directly or by sponsored organizations (such asNANPAin the US orCNACin Canada). In the United States, each state'spublic service commissionregulates, as does theFederal Communications Commission. In Canada, which shares the same country code with the U.S. (due toBell Canada's previous ownership by the U.S.-basedBell System), regulation is mainly through theCanadian Radio-television and Telecommunications Commission.
Local number portability(LNP) allows a subscriber to request moving an existing telephone number to another telephone service provider. Number portability usually has geographic limitations, such as anexisting local telephone companyonly being able to port toa competitorwithin the samerate centre. Mobile carriers may have much larger market areas, and can assign or accept numbers from any area within the region. In many telephone administrations, mobile telephone numbers are in organized in prefix ranges distinct from land line service, which simplifiesmobile number portability, even between carriers.
Within most North American rate centres, local wireline calls are free, while calls to all but a few nearby rate centres are consideredlong distanceand incur toll fees. In a few large US cities, as well as many points outside North America, local calls are not flat-rated or "free" by default.
Charles Williams, Jr., owned a Boston shop where Bell and Watson made experiments and later produced their telephones. This equipment company was purchased by Western Electric in 1882 and Williams became manager of this initial manufacturing plant until retiring in 1886, remaining a director in Western Electric. His residence was phone number 1 and his shop was phone number 2 in Boston.[8]
In the late 1870s, theBellinterests started utilizing theirpatentwith a rental scheme, in which they would rent their instruments to individual users who would contract with other suppliers to connect them; for example from home to office to factory.Western Unionand the Bell company both soon realized that asubscriptionservice would be more profitable, with the invention of thetelephone switchboardorcentral office. Such an office was staffed by anoperatorwho connected the calls by personal names. Some have argued that use of the telephone altered the physical layout of American cities.[9]
The latter part of 1879 and the early part of 1880 saw the first use of telephone numbers atLowell, Massachusetts. During an epidemic of measles, the physician, Dr. Moses Greeley Parker, feared that Lowell's four telephone operators might all succumb to sickness and bring about paralysis of telephone service. He recommended the use of numbers for calling Lowell's more than 200 subscribers so that substitute operators might be more easily trained in such an emergency.[2]Parker was convinced of the telephone's potential, began buying stock, and by 1883 he was one of the largest individual stockholders in both the American Telephone Company and theNew England Telephone and Telegraph Company.
Even after the assignment of numbers, operators still connected most calls into the early 20th century: "Hello, Central. Get me Underwood-342." Connecting through operators or "Central" was the norm until mechanical direct-dialing of numbers became more common in the 1920s.
In rural areas withmagneto crank telephonesconnected toparty lines, the local phone number consisted of the line number plus the ringing pattern of the subscriber. To dial a number such as "3R122" meant making a request to the operator the third party line (if making a call off your own local one), followed by turning the telephone's crank once, a short pause, then twice and twice again.[10]Also common was a code of long and short rings, so one party's call might be signaled by two longs and another's by two longs followed by a short.[11]It was not uncommon to have over a dozenring cadences(and subscribers) on one line.
In most areas ofNorth America, telephone numbers in metropolitan communities consisted of a combination of digits and letters, starting in the 1920s until the 1960s. Letters were translated to dialed digits, a mapping that was displayed directly on the telephone dial. Each of the digits 2 to 9, and sometimes 0, corresponded to a group of typically three letters. The leading two or three letters of a telephone number indicated theexchange name, for example,EDgewood andIVanhoe, and were followed by 5 or 4 digits. The limitations that these systems presented in terms of usable names that were easy to distinguish and spell, and the need for a comprehensive numbering plan that enabled direct-distance dialing, led to the introduction of all-number dialing in the 1960s.
The use ofnumbers starting in 555-(KLondike-5) to represent fictional numbers in U.S. movies, television, and literature originated in this period. The "555" prefix was reserved for telephone company use and was only consistently used fordirectory assistance(information), being "555–1212" for the local area. An attempt to dial a 555 number from a movie in the United States results in an error message. This reduces the likelihood of nuisance calls.QUincy(5–5555) was also used, because there was no Q available.
Phone numbers were traditionally tied down to a single location; because exchanges were "hard-wired", the first three digits of any number were tied to the geographic location of the exchange.
TheNorth American Numbering Planof 1947 prescribed a format of telephone numbers that included two leading letters of the name of the central office to which each telephone was connected. This continued the practice already in place by many telephone companies for decades. Traditionally, these names were often the names of towns, villages, or were other locally significant names. Communities that required more than one central office may have used other names for each central office, such as "Main", "East", " Central" or the names of local districts. Names were convenient to use and reduced errors when telephone numbers were exchanged verbally between subscribers and operators. When subscribers could dial themselves, the initial letters of the names were converted to digits as displayed on the rotary dial. Thus, telephone numbers contained one, two, or even three letters followed by up to five numerals. Such numbering plans are called 2L-4N, or simply 2–4, for example, as shown in the photo of a telephone dial of 1939 (right). In this example,LAkewood 2697indicates that a subscriber dialed the lettersLandA, then the digits2,6,9, and7to reach this telephone in Lakewood, NJ (USA). The leading letters were typically bolded in print.
In December 1930,New York Citybecame the first city in theUnited Statesto adopt the two-letter and five-number format (2L-5N), which became the standard afterWorld War II, when the Bell System administration designed the North American Numbering Plan to prepare the United States and Canada for Direct Distance Dialing (DDD), and began to convert all central offices to this format. This process was complete by the early 1960s, when a new numbering plan, often calledall number calling(ANC) became the standard in North America.
In theUK, letters were assigned to numbers in a similar fashion to North America, except that the letter O was allocated to the digit 0 (zero); digit 6 had only M and N. The letter Q was later added to the zero position on British dials, in anticipation of direct international dialing to Paris, which commenced in 1963. This was necessary because French dials already had Q on the zero position, and there were exchange names in the Paris region which contained the letter Q.
Most of theUnited Kingdomhad no lettered telephone dials until the introduction ofSubscriber Trunk Dialing(STD) in 1958. Until then, only thedirectorareas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) and the adjacent non-director areas had the lettered dials; the director exchanges used the three-letter, four-number format. With the introduction of trunk dialing, the need for all callers to be able to dial numbers with letters in them led to the much more widespread use of lettered dials. The need for dials with letters ceased with the conversion to all-digit numbering in 1968.
In the middle 20th century in North America when a call could not be completed, for example because the phone number was not assigned, had been disconnected, or was experiencing technical difficulties, the call was routed to an intercept operator who informed the caller. In the 1970s this service was converted to Automatic Intercept Systems which automatically choose and present an appropriateintercept message. Disconnected numbers are reassigned to new users after the rate of calls to them declines.
Outside of North America operator intercept was rare, although it did exist, for example it was sometimes used inIreland. However, in most cases, calls to unassigned or disconnected numbers resulted in an automated message, either giving specific or a generic recorded error message. Some networks and equipment simply returned anumber unobtainable,reorderorSIT(special information) tone to indicate an error.
In some networks recordings for error messages were (and still are) preceded by anSITtone. This is particularly useful in multilingual contexts as the tone indicates an error has been encountered, even if the message cannot be understood by the caller and can be interpreted as an error by some auto-dialling equipment.
Telephone numbers are sometimes prefixed with special services, such asvertical service codes, that contain signaling events other than numbers, most notably thestar(*) and thenumber sign(#).[3]Vertical service codes enable or disable special telephony services either on a per-call basis, or for the station or telephone line until changed.[4]The use of the number sign is most frequently used as a marker signal to indicate the end of digit sequences or the end of other procedures; as a terminator it avoids operational delays when waiting for expiration of automatic time-out periods.
Fictitious telephone numbersare often used in films and on television to avoid disturbances by calls from viewers. For example, The United States555(KLondike-5) exchange code was never assigned (with limited exceptions such as 555–1212 fordirectory assistance). Therefore, American films and TV shows have used 555-xxxx numbers, in order to prevent a number used in such a work from being called.[12]
The filmBruce Almighty(2003) originally featured a number that did not have the 555 prefix. In the cinematic release, God (Morgan Freeman) leaves 776–2323 on a pager for Bruce Nolan (Jim Carrey) to call if he needed God's help. The DVD changes this to a555 number. According toUniversal Studios, which produced the movie, the number it used was picked because it did not exist inBuffalo, New York, where the movie was set. It did exist in other cities, resulting in customers' having that number receiving random calls from people asking for God. While some played along with the gag, others found the calls aggravating.[13][14]
The number in theGlenn Miller Orchestra's hit song "Pennsylvania 6-5000" (1940) is the number of theHotel PennsylvaniainNew York City. The number is now written as 1-212-736-5000. According to the hotel's website,PEnnsylvania 6-5000is New York's oldest continually assigned telephone number and possibly the oldest continuously-assigned number in the world.[15][16]
Australian films and television shows do not employ any recurring format for fictional telephone numbers; any number quoted in such media may be used by a real subscriber. The 555 code is used in the Balmain area of Sydney and the suburbs ofMelbourne. Although in many areas being a prefix of 55 plus the thousand digit of 5 (e.g. 55 5XXX), would be valid, the numbering system was changed so that 555 became 9555 in Sydney and Melbourne, and in the country, there are two new digits ahead of the 55.[12]
Tommy Tutone's 1981 hit song "867-5309/Jenny" led to many unwanted calls by the public to telephone subscribers who actually were assigned that number.[17]
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A4G-LTE filteris alow-pass filterornotch filter, to be used interrestrial television(over-the-air/OTA)TV antennas(bothcollectiveand individual), to prevent cellular transmissions frominterferingwith television reception.
These filters are usually used for existing facilities, because antennas and amplifiers sold after the new standard was applied may be already be configured to receive, with good signal gain, onlyTV channelsfrom 14 to 51 of the UHF band, the other higher channels (former TV channels 52 to 83) being attenuated.
4G LTEis the fourth generation mobile phone standard. In urban areas, the 4G uses a frequency band located between 1800 MHz and 2600 MHz, and therefore is quite far from the TV band for causing any type of interference problem.
In rural areas, however, the major operators asked to use part of the UHF band. Since the UHF frequency band is not expandable, it was agreed that television broadcasting should limit its number of channels. Thus, the frequency band dedicated to TV became between 470 MHz and 700 MHz (channels 14-52), whilst 4G LTE uses the frequency bands between 700 and 900 MHz (former TV channels 52 to 83), resulting in an interval separating the two bands (DTT and 4G) of about 1 MHz, so that there is a risk ofinterference[1]in the areas close to the 4G-LTE transmitting towers.[1]In practice, these bands used 698 MHz to 960 MHz (depending on the carrier). See previous section on Filters.
This re-allocation of TV bandwidth to 4G is calledDigital dividend.[2]
Digital dividendto frequency 698 to 806 MHz (TV Channels 61 to 69) assigned by the plan for the New UHF Frequency Band distribution agreed inThe World Radio Congress (WRC-07)which identified 108 MHz of Digital Dividend Spectrum from 698 to 806 MHz for ITU-R Regions 2-1 and nine countries in Regions 3-2, including China, India, Japan and Rep. of Korea.[3]
This Digital dividend is used to improve the coverage of the 4G-LTE new standard in rural areas, needed with the arrival of 4G-LTE and requires therefore the redistribution of UHF frequency band. Starting from January 2015 (in some countries), the main mobile operators will begin to deploy their networks of very high band width "True 4G" or LTE using the frequency previously attributed to TV Channels 61 to 69, which is known as "digital dividend".[3]
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A wide variety of different wireless data technologies exist, some in direct competition with one another, others designed for specific applications.Wirelesstechnologies can be evaluated by a variety of different metrics of which some are described in this entry.
Standards can be grouped as follows in increasing range order:
Personal area network(PAN) systems are intended for short range communication between devices typically controlled by a single person. Some examples include wireless headsets for mobile phones or wireless heart rate sensors communicating with a wrist watch. Some of these technologies include standards such asANTUWB,Bluetooth,Zigbee, andWireless USB.
Wireless Sensor Networks(WSN / WSAN) are, generically, networks of low-power, low-cost devices that interconnect wirelessly to collect, exchange, and sometimes act-on data collected from their physical environments - "sensor networks". Nodes typically connect in a star or mesh topology. While most individual nodes in a WSAN are expected to have limited range (Bluetooth, Zigbee,6LoWPAN, etc.), particular nodes may be capable of more expansive communications (Wi-Fi,Cellular networks, etc.) and any individual WSAN can span a wide geographical range. An example of a WSAN would be a collection of sensors arranged throughout an agricultural facility to monitor soil moisture levels, report the data back to a computer in the main office for analysis and trend modeling, and maybe turn on automatic watering spigots if the level is too low.
For wider area communications,wireless local area network(WLAN) is used. WLANs are often known by their commercial product nameWi-Fi. These systems are used to provide wireless access to other systems on the local network such as other computers, shared printers, and other such devices or even the internet. Typically a WLAN offers much better speeds and delays within the local network than an average consumer'sInternet access. Older systems that provide WLAN functionality includeDECTandHIPERLAN. These however are no longer in widespread use. One typical characteristic of WLANs is that they are mostly very local, without the capability of seamless movement from one network to another.
Cellular networksorWANare designed for citywide/national/global coverage areas and seamless mobility from one access point (often defined as abase station) to another allowing seamless coverage for very wide areas. Cellular network technologies are often split into 2nd generation2G,3Gand4Gnetworks. Originally 2G networks were voice centric or even voice only digital cellular systems (as opposed to the analog 1G networks). Typical 2G standards includeGSMandIS-95with extensions viaGPRS,EDGEand1xRTT, providing Internet access to users of originally voice centric 2G networks. BothEDGEand1xRTTare 3G standards, as defined by theITU, but are usually marketed as 2.9G due to their comparatively low speeds and high delays when compared to true 3G technologies.
True 3G systems such asEV-DO,W-CDMA(includingHSPAandHSPA+) provide combinedcircuit switchedandpacket switcheddata and voice services from the outset, usually at far better data rates than 2G networks with their extensions. All of these services can be used to provide combined mobile voice access and Internet access at remote locations.
4G networks provide even higher bitrates and many architectural improvements, which are not necessarily visible to the consumer. The current 4G systems that are deployed widely areWIMAXandLTE. The two are pure packet based networks without traditional voice circuit capabilities. These networks provide voice services viaVoIPorVoLTE.
Some systems are designed for point-to-point line-of-sight communications, once two such nodes get too far apart they can no longer communicate. Other systems are designed to form awireless mesh networkusing one of a variety ofrouting protocols. In a mesh network, when nodes get too far apart to communicate directly, they can still communicate indirectly through intermediate nodes.
The following standards are included in this comparison.
Antenna,RF front endenhancements and minor protocol timer tweaks have helped deploy long rangeP2Pnetworks compromising on radial coverage, throughput and/or spectra efficiency (310 km&382 km)
Notes: All speeds are theoretical maximums and will vary by a number of factors, including the use of external antennas, distance from the tower and the ground speed (e.g. communications on a train may be poorer than when standing still). Usually the bandwidth is shared between several terminals. The performance of each technology is determined by a number of constraints, including thespectral efficiencyof the technology, the cell sizes used, and the amount of spectrum available.
For more comparison tables, seebit rate progress trends,comparison of mobile phone standards,spectral efficiency comparison tableandOFDM system comparison table.
When discussing throughput, there is often a distinction between the peak data rate of the physical layer, the theoretical maximum data throughput and typical throughput.
The peak bit rate of the standard is thenet bit rateprovided by the physical layer in the fastest transmission mode (using the fastest modulation scheme and error code), excluding forward error correction coding and other physical layer overhead.
The theoreticalmaximum throughputfor end user is clearly lower than the peak data rate due to higher layer overheads. Even this is never possible to achieve unless the test is done under perfect laboratory conditions.
The typical throughput is what users have experienced most of the time when well within the usable range to the base station. The typical throughput is hard to measure, and depends on many protocol issues such as transmission schemes (slower schemes are used at longer distance from the access point due to better redundancy), packet retransmissions and packet size. The typicalthroughputis often even lower because of other traffic sharing the same network or cell, interference or even the fixed line capacity from the base station onwards being limited.
Note that these figures cannot be used to predict the performance of any given standard in any given environment, but rather as benchmarks against which actual experience might be compared.
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E-UTRAis theair interfaceof 3rd Generation Partnership Project (3GPP)Long Term Evolution(LTE) upgrade path for mobile networks. It is an acronym forEvolved UMTS Terrestrial Radio Access,[1]also known as theEvolved Universal Terrestrial Radio Accessin early drafts of the 3GPP LTE specification.[1]E-UTRANis the combination of E-UTRA,user equipment(UE), and aNode B(E-UTRAN Node B or Evolved Node B,eNodeB).
It is aradio access network(RAN) meant to be a replacement of theUniversal Mobile Telecommunications System(UMTS),High-Speed Downlink Packet Access(HSDPA), andHigh-Speed Uplink Packet Access(HSUPA) technologies specified in 3GPP releases 5 and beyond. Unlike HSPA, LTE's E-UTRA is an entirely new air interface system, unrelated to and incompatible withW-CDMA. It provides higher data rates, lower latency and is optimized for packet data. It usesorthogonal frequency-division multiple access(OFDMA) radio-access for the downlink andsingle-carrier frequency-division multiple access(SC-FDMA) on the uplink. Trials started in 2008.
EUTRAN has the following features:
AlthoughUMTS, withHSDPAandHSUPAand theirevolution, deliver high data transfer rates, wireless data usage is expected to continue increasing significantly over the next few years due to the increased offering and demand of services and content on-the-move and the continued reduction of costs for the final user. This increase is expected to require not only faster networks and radio interfaces but also higher cost-efficiency than what is possible by the evolution of the current standards. Thus the 3GPP consortium set the requirements for a new radio interface (EUTRAN) and core network evolution (System Architecture Evolution SAE) that would fulfill this need.
These improvements in performance allowwirelessoperators to offerquadruple playservices – voice, high-speed interactive applications including large data transfer andfeature-richIPTVwith full mobility.
Starting with the 3GPP Release 8, E-UTRA is designed to provide a single evolution path for theGSM/EDGE,UMTS/HSPA,CDMA2000/EV-DOandTD-SCDMAradio interfaces, providing increases in data speeds, and spectral efficiency, and allowing the provision of more functionality.
EUTRAN consists only of eNodeBs on the network side. The eNodeB performs tasks similar to those performed by thenodeBsandRNC (radio network controller)together in UTRAN. The aim of this simplification is to reduce the latency of all radio interface operations. eNodeBs are connected to each other via the X2 interface, and they connect to thepacket switched (PS)core network via the S1 interface.[3]
The EUTRANprotocol stackconsists of:[3]
Interfacing layers to the EUTRAN protocol stack:
E-UTRA usesorthogonal frequency-division multiplexing(OFDM),multiple-input multiple-output(MIMO) antenna technology depending on the terminal category and can also usebeamformingfor the downlink to support more users, higher data rates and lower processing power required on each handset.[10]
In the uplink LTE uses bothOFDMAand a precoded version of OFDM calledSingle-Carrier Frequency-Division Multiple Access (SC-FDMA)depending on the channel. This is to compensate for a drawback with normal OFDM, which has a very highpeak-to-average power ratio (PAPR). High PAPR requires more expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. For the uplink, in release 8 and 9 multi user MIMO / Spatial division multiple access (SDMA) is supported; release 10 introduces alsoSU-MIMO.
In both OFDM and SC-FDMA transmission modes acyclic prefixis appended to the transmitted symbols. Two different lengths of the cyclic prefix are available to support differentchannel spreadsdue to the cell size and propagation environment. These are a normal cyclic prefix of 4.7 μs, and an extended cyclic prefix of 16.6 μs.
LTE supports bothFrequency-division duplex(FDD) andTime-division duplex(TDD) modes. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD splits one frequency carrier into alternating time periods for transmission from the base station to the terminal and vice versa. Both modes have their own frame structure within LTE and these are aligned with each other meaning that similar hardware can be used in the base stations and terminals to allow for economy of scale. The TDD mode in LTE is aligned withTD-SCDMAas well allowing for coexistence. Single chipsets are available which support both TDD-LTE and FDD-LTE operating modes.
The LTE transmission is structured in the time domain in radio frames. Each of these radio frames is 10 ms long and consists of 10 sub frames of 1 ms each. For non-Multimedia Broadcast Multicast Service(MBMS) subframes, theOFDMAsub-carrier spacing in the frequency domain is 15 kHz. Twelve of these sub-carriers together allocated during a 0.5 ms timeslot are called a resource block.[11]A LTE terminal can be allocated, in the downlink or uplink, a minimum of 2 resources blocks during 1 subframe (1 ms).[12]
All L1 transport data is encoded usingturbo codingand a contention-freequadratic permutation polynomial(QPP) turbo code internalinterleaver.[13]L1HARQwith 8 (FDD) or up to 15 (TDD) processes is used for the downlink and up to 8 processes for the UL
In the downlink there are several physical channels:[14]
And the following signals:
In the uplink there are three physical channels:
And the following signals:
3GPP Release 8 defines five LTE user equipment categories depending on maximum peak data rate and MIMO capabilities support. With 3GPP Release 10, which is referred to asLTE Advanced, three new categories have been introduced. Followed by four more with Release 11, two more with Release 14, and five more with Release 15.[2]
Note: Maximum data rates shown are for 20 MHz of channel bandwidth. Categories 6 and above include data rates from combining multiple 20 MHz channels. Maximum data rates will be lower if less bandwidth is utilized.
Note: These are L1 transport data rates not including the different protocol layers overhead. Depending on cellbandwidth, cell load (number of simultaneous users), network configuration, the performance of the user equipment used, propagation conditions, etc. practical data rates will vary.
Note: The 3.0 Gbit/s / 1.5 Gbit/s data rate specified as Category 8 is near the peak aggregate data rate for a base station sector. A more realistic maximum data rate for a single user is 1.2 Gbit/s (downlink) and 600 Mbit/s (uplink).[16]Nokia Siemens Networks has demonstrated downlink speeds of 1.4 Gbit/s using 100 MHz of aggregated spectrum.[17]
As the rest of the3GPPstandard parts E-UTRA is structured in releases.
All LTE releases have been designed so far keeping backward compatibility in mind. That is, a release 8 compliant terminal will work in a release 10 network, while release 10 terminals would be able to use its extra functionality.
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Evolved High Speed Packet Access,HSPA+,HSPA(Plus) orHSPAP, is atechnical standardforwireless broadbandtelecommunication, and extends the originalHSPA. The 3GPP standard organisation specified the original HSPA in release 7. HSPA+ can achieve data rates of up to 42.2 Mbit/s.[1]HSPA+ upgrades existing 3G networks to achieve speeds closer to 4G without a new radio interface. HSPA+ should not be confused withLTE, which uses an air interface based onorthogonal frequency-divisionmodulation and multiple access.[2]
HSPA+ introduces antenna array technologies such asbeamformingandmultiple-input multiple-output communications(MIMO). Beamforming focuses antenna power in a beam toward the user's direction. MIMO uses multiple antennas on the sending and receiving side. Further releases of the standard have introduced dual carrier operation, allowing communication over two 5 MHz frequency bands simultaneously.
Advanced HSPA+ is a further evolution of HSPA and provides download speeds up to 168 Mbit/s and upload speeds up to 22 Mbit/s. This is achieved with higherorder modulation(64QAM) or combining cells with Dual-Cell HSDPA.
AnEvolved HSDPAnetwork can be up to 28 Mbit/s and 42 Mbit/s with a single 5 MHz carrier for Rel7 (MIMO with 16QAM) and Rel8 (64-QAM+MIMO). This doubling of cells used can improve throughput, diversity and joint scheduling.[3]Quality of service can be particularly improved for users with poor reception. Alternatively data rates can be doubles by double the bandwidth to 10 MHz (i.e. 2×5 MHz) by using DC-HSDPA.
Dual-Carrier HSDPA, (aka Dual-Cell HSDPA), is part of3GPPRelease 8 specification, allowing communication with a mobile user over multiple frequency bands simultaneously. UMTS licenses are often issued as 5, 10, or 20 MHz paired spectrum allocations. The multicarrier feature achieves better resource utilization and spectrum efficiency through joint resource allocation and load balancing across the downlink carriers.[4]
New HSDPAUser Equipment categories 21-24have been introduced that support DC-HSDPA. DC-HSDPA can support up to 42.2 Mbit/s, but unlike HSPA, it does not need to rely on MIMO transmission.
The support of MIMO in combination with DC-HSDPA allows operators deploying Release 7 MIMO to benefit from the DC-HSDPA functionality defined in Release 8. While in Release 8 DC-HSDPA can only operate on adjacent carriers, Release 9 also allows that the paired cells can operate on two different frequency bands. Later releases allow the use of up to four carriers simultaneously.
From Release 9 onwards is possible to use DC-HSDPA in combination with MIMO being used on both carriers. The support of MIMO in combination with DC-HSDPA allows theoretical speeds of up to 84.4 Mbit/s.[5][6]
The following table is derived from table 5.1a of the release 11 of 3GPP TS 25.306[7]and shows maximum data rates of different device classes and by what combination of features they are achieved. The per-cell per-stream data rate is limited by theMaximum number of bits of an HS-DSCH transport block received within an HS-DSCH TTIand theMinimum inter-TTI interval. The TTI is 2 ms. So for example Cat 10 can decode 27,952 bits/2 ms = 13.976 Mbit/s (and not 14.4 Mbit/s as often claimed incorrectly). Categories 1-4 and 11 have inter-TTI intervals of 2 or 3, which reduces the maximum data rate by that factor. Dual-Cell and MIMO 2x2 each multiply the maximum data rate by 2, because multiple independent transport blocks are transmitted over different carriers or spatial streams, respectively. The data rates given in the table are rounded to one decimal point.
Dual-Carrier HSUPA, also known asDual-Cell HSUPA, is a wireless broadband standard based on HSPA that is defined in3GPPUMTSrelease 9.
Dual Cell (DC-)HSUPA is the natural evolution of HSPA by means of carrier aggregation in the uplink.[8]UMTS licenses are often issued as 10 or 15 MHz paired spectrum allocations. The basic idea of the multicarrier feature is to achieve better resource utilization and spectrum efficiency by means of joint resource allocation and load balancing across the uplink carriers.
Similar enhancements as introduced withDual-Cell HSDPAin the downlink for 3GPP Release 8 were standardized for the uplink in 3GPP Release 9, called Dual-Cell HSUPA. The standardisation of Release 9 was completed in December 2009.[9][10][11]
The following table shows uplink speeds for the different categories of Evolved HSUPA.
The aggregation of more than two carriers has been studied and3GPPRelease 11 is scheduled to include 4-carrier HSPA. The standard was scheduled to be finalised in Q3 2012 and first chipsets supporting MC-HSPA in late 2013. Release 11 specifies 8-carrier HSPA allowed in non-contiguous bands with 4 × 4MIMOoffering peak transfer rates up to672 Mbit/s.
The 168 Mbit/s and 22 Mbit/s represent theoretical peak speeds. The actual speed for a user will be lower. In general, HSPA+ offers higher bitrates only in very good radio conditions (very close to the cell tower) or if the terminal and network both support eitherMIMOorDual-Cell HSDPA, which effectively use two parallel transmit channels with different technical implementations.
The higher 168 Mbit/s speeds are achieved by using multiple carriers withDual-Cell HSDPAand 4-wayMIMOtogether simultaneously.[12][13]
A flattened all-IP architecture is an option for the network within HSPA+. In this architecture, the base stations connect to the network via IP (often Ethernet providing the transmission), bypassing legacy elements for the user's data connections. This makes the network faster and cheaper to deploy and operate. The legacy architecture is still permitted with the Evolved HSPA and is likely to exist for several years after adoption of the other aspects of HSPA+ (higher-order modulation, multiple streams, etc.).
This 'flat architecture' connects the 'user plane' directly from the base station to theGGSNexternal gateway, using any available link technology supporting TCP/IP. The definition can be found in3GPP TR25.999. The user's data flow bypasses the Radio Network Controller (RNC) and theSGSNof the previous 3GPP UMTS architecture versions, thus simplifying the architecture, reducing costs and delays. This is nearly identical to the3GPP Long Term Evolution(LTE) flat architecture as defined in the 3GPP standard Rel-8. The changes allow cost-effective modern link layer technologies such as xDSL or Ethernet, and these technologies are no longer tied to the more expensive and rigid requirements of the older standard of SONET/SDH and E1/T1 infrastructure.
There are no changes to the 'control plane'.
Nokia Siemens NetworksInternet HSPA(I-HSPA) was the first commercial solution implementing the Evolved HSPA flattened all-IP architecture.[14]
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Flat IPis anetwork addressingscheme where each device is assigned aunique identifierwithin anon-hierarchicaladdress space. Unlikehierarchical IPaddressing methods, which rely on structuredsub-networking, flat IP treats all devices as equal entities.
This approach is frequently used incellular networks, particularly inLTE, due to its efficiency in managing device handovers between network cells. It enables each device to be directly accessed via its unique identifier, improving routing efficiency and reducing latency in mobile environments.
While flat IP can streamline network design for specific applications, it may presentscalabilitychallenges in large networks. The scheme lacks a structuredhierarchyand requires a large pool ofunique identifiers, which can reduce efficiency in large-scale networks compared to traditionalIP models. However, flat IP remains a practical choice when simplicity and direct device access are prioritized.
Flat IParchitectureis suited for various settings, including small businesses,home networks,mobile broadband. It facilitates streamlinednetwork management, and establishes direct connections for real-time data applications.[1]
Wireless operators adopt flat IP architecture to meet the growing need for real-time data applications delivered over mobilebroadband networks. Unlike traditionalhierarchicalnetwork designs, flat IP architecture relies upon a simplified, horizontal structure.
Flat IP architectures can offer advantages such as:
In mobile networks, centralized anchors often cause performance bottlenecks. Flat, distributed architectures resolve this by removing centralized components, improving scalability, flexibility, andlatency.[2]
Flat IP architecture can present several challenges:
Flat IP architecture is more suited for mobile networks. The following organizations use Flat IP:
In mobile networks, flat IP architecture integrates several essential components, including:[4]
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LTE in unlicensed spectrum(LTE-Unlicensed,LTE-U) is an extension of theLong-Term Evolution(LTE) wireless standard that allows cellular network operators to offload some of their data traffic by accessing the unlicensed 5 GHz frequency band.[1]LTE-Unlicensed is a proposal, originally developed byQualcomm, for the use of the4G LTEradio communications technology inunlicensed spectrum, such as the 5 GHz band used by802.11aand802.11accompliantWi-Fiequipment.[2][3]It would serve as an alternative to carrier-ownedWi-Fi hotspots. Currently, there are a number of variants of LTE operation in the unlicensed band, namely LTE-U, License Assisted Access (LAA), MulteFire, sXGP and CBRS.[4]
The first version of LTE-Unlicensed is called LTE-U and is developed by the LTE-U Forum to work with the existing 3GPP Releases 10/11/12. LTE-U was designed for quick launch in countries, such as the United States and China, that do not mandate implementing the listen-before-talk (LBT) technique. LTE-U would allow cellphone carriers to boost coverage in their cellular networks, by using the unlicensed 5 GHz band alreadypopulatedby Wi-Fi devices.
LTE-U is intended to let cell networks boost data speeds over short distances, without requiring the user to use a separate Wi-Fi network as they normally would. It differs fromWi-Fi calling; there remains a control channel using LTE, but all data (not just phone calls) flows over the unlicensed 5 GHz band, instead of the carrier's frequencies.[5]
In 2014, the LTE-U Forum was created byVerizon, in conjunction withAlcatel-Lucent,Ericsson,Qualcomm, andSamsungas members.[6][7]The forum collaborates and creates technical specifications forbase stationsand consumer devices passing LTE-U on the unlicensed 5 GHz band, as well as coexistence specs to handle traffic contention with existing Wi-Fi devices.
T-MobileandVerizon Wirelesshave indicated early interest in deploying such a system as soon as 2016.[8]While cell providers ordinarily rely on theradio spectrumto which they have exclusive licenses, LTE-U would share space with Wi-Fi equipment already inhabiting that band – smartphones, laptops and tablets connecting to home broadband networks, free hotspots provided by businesses, and so on.
As of late January 2019, there were three LTE-U deployed/launched networks in three countries; eight further operators are investing in the technology in the form of trials or pilots in seven countries.[9]
The second variant of LTE-Unlicensed is Licensed Assisted Access (LAA) and has been standardized by the 3GPP in Rel-13. LAA adheres to the requirements of the LBT protocol, which is mandated in Europe and Japan. It promises to provide a unified global framework that complies with the regulatory requirements in the different regions of the world.
Ericssonuses the termLicense Assisted Access(LAA) to describe similar technology.[10]LAA is the3rd Generation Partnership Project's (3GPP) effort to standardize operation of LTE in the Wi-Fi bands. It uses acontention protocolknown as listen-before-talk (LBT), mandated in some European countries, to coexist with other Wi-Fi devices on the same band.[8][6][1]
MulteFire is another variant of LTE in unlicensed bands and has been proposed as a standalone version of LTE for small cells. This variant will use only the unlicensed spectrum as the primary and only carrier, and it will provide an opportunity for neutral hosts to deploy LTE in the future.[1]The idea of standalone operation of LTE in unlicensed bands was originally proposed by a small minority of vendors in 3GPP but rejected by the network operators who wanted the technology to be reliant on their licensed spectrum holdings.[citation needed]This technology is now developed by theMuLTEfire Alliance.
The proposed use of LTE-U bymobile phone networkoperators is the subject of controversy in the telecommunications industry.[11]In June 2015,Googlesent theFederal Communications Commission(FCC) of the United States a 25-page protest, making an argument against LTE-U in highly technical detail.[6]Since Google's study did not use actual LTE-U equipment in the tests, some industry experts have called its conclusions into question, with one commenter calling the study "utterly artificial and speculative" and "embarrassing".[12]
In August 2015, theWi-Fi AllianceandNational Cable & Telecommunications Association(NCTA) also voiced opposition to LTE-U approval before more testing can be done, citing concerns that it would severely degrade performance of other Wi-Fi devices.[5]Also in August 2015,Qualcommresponded to the allegations made in Google's whitepaper in a detailed filing with theFCC.[13]Qualcomm stated that it conducted tests that were "specifically designed to replicate (to the fullest extent possible) the test scenarios cited in Google’s FCC filing, in particular", and that they "collectively showed that LTE-U coexists very well with Wi-Fi when LTE-U is operating either above or below Wi-Fi’s Energy Detect ('ED') level." Qualcomm explained that the divergence in results was caused by the fact that "the testing the opposing parties conducted for LTE-U/Wi-Fi coexistence below the ED level utilized extremely pessimistic and impractical technical assumptions", whereas Qualcomm's tests were conducted "using a far more realistic setup", including actual LTE-U equipment (versus signal generators in Google's study).
In May 2016, the New York City Mayor's Office sent a letter to the FCC, 3GPP, Wi-Fi Alliance, and IEEE, expressing concern over LTE-U interference with Wi-Fi, given the City's broad investment in the technology.[14]These concerns were discussed at a public event.[15]
In June 2016 the Wi-Fi Alliance announced its co-existence test plan would be ready in August. In FCC filings, Qualcomm, Verizon and T-Mobile said they plan to use this plan, some with the aim of full implementation before the end of 2016.[16]However, in August 2016, Qualcomm demurred. “The latest version of the test plan released by the Wi-Fi Alliance lacks technical merit, is fundamentally biased against LTE-U, and rejects virtually all the input that Qualcomm provided for the last year, even on points that were not controversial,” said Dean Brenner, senior vice president of government affairs.[17]Qualcomm asserts that the plan biased in favor of Wi-Fi, and also that the testing regimen is extended to cover not just LTE-U, but also LAA, despite it already being a 3GPP standard.[17]Verizon also opposed the test plan, saying it was "fundamentally unfair and biased".[18]
Research from the University of Chicago in 2021 also showed a marked decrease in Wi-FI performance when LAA was in active use.[19]
In November 2016 Verizon, separate to the Wi-Fi Alliance coexistence plan, filed a Special Temporary Authority (STA) application with the FCC[20]to test 40 small cells in the 5 GHz band. According to a separate filing, Verizon will conduct the tests in Oklahoma City, Raleigh and Cary, North Carolina, and Irving, Texas.[21]
In February 2017, the FCC approved the use of LTE-U on base stations manufactured by Ericsson and Nokia.[22]
As of June 26, 2017, T-Mobile declared that they have successfully launched LTE-U in Bellevue, Washington; Brooklyn, New York; Dearborn, Michigan; Las Vegas, Nevada; Richardson, Texas; and Simi Valley, California.[23]
In January 2019, theGlobal Mobile Suppliers Associationreported that 32 operators are investing in LAA across 21 countries;[9]this had increased to 37 operators in 21 countries by July 2019.[24]Eight of these have announced LAA network launches in six countries, while 29 operators are trialling or deploying the technology in 18 countries. The GSA also identified 21 chipsets containing modems that support one or more of LTE-U, LAA, LWA or CBRS from vendors including GCT,Intel,Mediatek,Qualcomm, andSamsung.[9][24]
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Narrowband Internet of things(NB-IoT) is alow-power wide-area network(LPWAN)radio technologystandard developed by3GPPforcellular networkdevices and services.[1][2]The specification was frozen in3GPP Release 13(LTE Advanced Pro), in June 2016.[3]Other 3GPPIoTtechnologies includeeMTC(enhanced Machine-Type Communication) and EC-GSM-IoT.[4]
NB-IoT focuses specifically on indoor coverage, long battery life, and high connection density. NB-IoT uses a subset of theLTEstandard, but limits the bandwidth to a single narrow-band of 200kHz. It usesOFDMmodulation for downlink communication andSC-FDMAfor uplink communications.[5][6][7][8][9]IoT applications which require more frequent communications will be better served byLTE-M, which has no duty cycle limitations operating on the licensed spectrum.
In March 2019, theGlobal Mobile Suppliers Association(GSA) announced that over 100 operators had either NB-IoT or LTE-M networks.[10]This number had risen to 142 deployed/launched networks by September 2019.[11]
2 Mbit/s (EGPRS2B)
16.9 kbit/s (single-tone)
2 Mbit/s (EGPRS2B)
As of March 2019 GSA identified:[14]
The3GPP-compliantLPWAdevice ecosystem continues to grow. In April 2019,GSAidentified 210 devices supporting either Cat-NB1/NB-2 or Cat-M1 – more than double the number in its GAMBoD database at the end of March 2018.[16]This figure had risen a further 50% by September 2019, with a total of 303 devices identified as supporting either Cat-M1, Cat-NB1 (NB-IoT) or Cat-NB2. Of these, 230 devices support Cat-NB1 (including known variants) and 198 devices support Cat-M1 (including known variants). The split of devices (as of September 2019) was 60.4% modules, 25.4% asset trackers, and 5.6% routers, with data loggers, femtocells, smart-home devices, and smart watches, USB modems, and vehicle on-board units (OBUs), making up the balance.[17]
In 2018 first NB-IoT data loggers and other certified devices started to appear. For example ThingsLog released their first CE certified single channel NB-IoT data logger on Tindie in late 2018.
To integrate NB-IoT into a maker board for IoT developments, SODAQ, a Dutch IoT hardware and software engineering company, crowdfunded an NB-IoT shield onKickstarter.[18]They then went on to partner with module manufactureru-bloxto create maker boards with NB-IoT andLTE-Mintegrated.[19]
Since 2021, there also is a cheap all-in-one NB-IoT solution available to the general public developed by the Chinese manufacturer Ai-Thinker.[20]
At the beginning of 2023 the Belgian company DPTechnics released theWalterIoT board which combines an ESP32-S3 together with aSequansMonarch 2 NB-IoT/LTE-M platform. The board is focused on long-term availability and includes a GNSS receiver.
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QoS Class Identifier(QCI) is a mechanism used in3GPPLong Term Evolution(LTE) networks to ensure carrier traffic is allocated appropriateQuality of Service(QoS). Different carrier traffic requires different QoS and therefore different QCI values. QCI value 9 is typically used for the default carrier of a UE/PDN for non privileged subscribers.[1]
To ensure that carrier traffic in LTE networks is appropriately handled, a mechanism is needed to classify the different types of carriers into different classes, with each class having appropriate QoS parameters for the traffic type. Examples of the QoS parameters include Guaranteed Bit Rate (GBR) or non-Guaranteed Bit Rate (non-GBR), Priority Handling, Packet Delay Budget and Packet Error Loss rate. This overall mechanism is called QCI.
The QoS concept as used in LTE networks is class-based, where each carrier type is assigned one QoS Class Identifier (QCI) by the network. The QCI is a scalar that is used within the access network (namely theeNodeB) as a reference to node specific parameters that control packet forwarding treatment, for example scheduling weight, admission thresholds and link-layer protocol configuration.
The QCI is also mapped to transport network layer parameters in the relevantEvolved Packet Core(EPC) core network nodes (for example, thePDN Gateway(P-GW),Mobility Management Entity(MME) andPolicy and Charging Rules Function(PCRF)), by preconfigured QCI toDifferentiated Services Code Point(DSCP) mapping.
According to 3GPP TS 23.203, 9 QCI values in Rel-8 (13 QCIs Rel-12, 15 QCIs Rel-14) are standardized and associated with QCI characteristics in terms of packet forwarding treatment that the carrier traffic receives edge-to-edge between theUEand the P-GW. Scheduling priority, resource type, packet delay budget and packet error loss rate are the set of characteristics defined by the 3GPP standard and they should be understood as guidelines for the pre-configuration of node specific parameters to ensure that applications/services mapped to a given QCI receive the same level of QoS in multi-vendor environments as well as in roaming scenarios. The QCI characteristics are not signalled on any interface.
The following table illustrates the standardized characteristics as defined in the 3GPP TS 23.203 standard "Policy and Charging Control Architecture".
Every QCI (GBR and Non-GBR) is associated with a Priority level. Priority level 0.5 is the highest Priority level. If congestion is encountered, the lowest Priority level traffic (highest Priority number!) would be the first to be discarded.
QCI-65, QCI-66, QCI-69 and QCI-70 were introduced in 3GPP TS 23.203 Rel-12.
QCI-75 and QCI-79 were introduced in 3GPP TS 23.203 Rel-14.
QCI-67 was introduced in 3GPP TS 23.203 Rel-15.
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System Architecture Evolution(SAE) is the core network architecture of mobile communications protocol group3GPP'sLTEwireless communication standard.
SAE is the evolution of theGPRS Core Network, but with a simplified architecture; an all-IP Network (AIPN); support for higher throughput and lower latencyradio access networks(RANs); and support for, and mobility between, multiple heterogeneous access networks, includingE-UTRA(LTEandLTE Advancedair interface), and 3GPP legacy systems (for exampleGERANorUTRAN, air interfaces ofGPRSandUMTSrespectively), but also non-3GPP systems (for exampleWi-Fi,WiMAXorCDMA2000).
The SAE has a flat, all-IP architecture with separation of control plane and user plane traffic.
The main component of the SAE architecture is theEvolved Packet Core(EPC), also known asSAE Core. The EPC will serve as the equivalent of GPRS networks (via theMobility Management Entity,Serving GatewayandPDN Gatewaysubcomponents).
The subcomponents of the EPC are:[1][2]
The MME is the key control-node for the LTE access-network. It is responsible for idle modeUser Equipment(UE) paging and tagging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the Serving Gateway for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with theHome Subscriber Server). TheNon Access Stratum(NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs. It checks the authorization of the UE to camp on the service provider'sPublic Land Mobile Network(PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from theSGSN. The MME also terminates the S6a interface towards the HSS for roaming UEs.
The Serving Gateway routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNodeBhandovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and Packet Data Network Gateway). For idle state User Equipment, the Serving Gateway terminates the downlink data path and triggers paging when downlink data arrives for the User Equipment. It manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception.
The Packet Data Network Gateway (PDN Gateway, also PGW) provides connectivity from the User Equipment (UE) to external packet data networks (PDNs) by being its point of exit and entry of traffic. A piece of User Equipment may have simultaneous connectivity with more than one Packet Data Network Gateway for accessing multiple packet data networks. The PDN Gateway performs policy enforcement, packet filtering for each user, charging support,lawful interceptionand packet screening. Another key role of the Packet Data Network Gateway is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and3GPP2(CDMA 1X andEvDO).
TheHome Subscriber Serveris a central database that contains user-related and subscription-related information. The functions of the HSS include mobility management, call and session establishment support, user authentication and access authorization. The HSS is based on pre-Rel-4Home Location Register(HLR) andAuthentication Center(AuC).
TheANDSFprovides information to the UE about connectivity to 3GPP and non-3GPP access networks (such as Wi-Fi). The purpose of the ANDSF is to assist the UE to discover the access networks in their vicinity and to provide rules (policies) to prioritize and manage connections to these networks.
The main function of the ePDG is to secure the data transmission with a UE connected to the EPC over untrusted non-3GPP access, e.g.Wi-Fi calling(VoWiFi). For this purpose, the ePDG acts as a termination node ofIPsectunnels established with the UE.
The Non-Access Stratum (NAS) protocols form the highest stratum of the control plane between the user equipment (UE) and MME.[3]NAS protocols support the mobility of the UE and the session management procedures to establish and maintain IP connectivity between the UE and a PDN GW. They define the rules for a mapping between parameters during inter-system mobility with 3G networks or non-3GPP access networks. They also provide the NAS security by integrity protection and ciphering of NAS signaling messages. EPS (Evolved Packet System) provides the subscriber with a "ready-to-use" IP connectivity and an "always-on" experience by linking between mobility management and session management procedures during the UE attach procedure.
Complete NAS transactions consist of specific sequences of elementary procedures with EPS Mobility Management (EMM) and EPS Session Management (ESM) protocols.
The EPS (Evolved Packet System) Mobility Management (EMM) protocol provides procedures for the control of mobility when the User Equipment (UE) uses the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). It also provides control of security for the NAS protocols.
EMM involves different types of procedures such as:
The UE and the network execute the attach procedure, the default EPS bearer context activation procedure in parallel. During the EPS attach procedure the network activates a default EPS bearer context. The EPS session management messages for the default EPS bearer context activation are transmitted in an information element in the EPS mobility management messages. The UE and network complete the combined default EPS bearer context activation procedure and the attach procedure before the dedicated EPS bearer context activation procedure is completed. The success of the attach procedure is dependent on the success of the default EPS bearer context activation procedure. If the attach procedure fails, then the ESM session management procedures also fails.
The EPS Session Management (ESM) protocol provides procedures for the handling of EPS bearer contexts. Together with the bearer control provided by theAccess Stratum, it provides the control of user plane bearers. The transmission of ESM messages is suspended during EMM procedures except for the attach procedure.
EPS Bearer:Each EPS bearer context represents an EPS bearer between the UE and a PDN. EPS bearer contexts can remain activated even if the radio and S1 bearers constituting the corresponding EPS bearers between UE and MME are temporarily released. An EPS bearer context can be either a default bearer context or a dedicated bearer context. A default EPS bearer context is activated when the UE requests a connection to a PDN. The first default EPS bearer context, is activated during the EPS attach procedure. Additionally, the network can activate one or several dedicated EPS bearer contexts in parallel.
Generally, ESM procedures can be performed only if an EMM context has been established between the UE and the MME, and the secure exchange of NAS messages has been initiated by the MME by use of the EMM procedures. Once the UE is successfully attached, the UE can request the MME to set up connections to additional PDNs. For each additional connection, the MME activates a separate default EPS bearer context. A default EPS bearer context remains activated throughout the lifetime of the connection to the PDN.
Types of ESM procedures:
ESM involves different types of procedures such as:
The MME maintains EMM context and EPS bearer context information for UEs in the ECM-IDLE, ECM CONNECTED and EMM-DEREGISTERED states.
The MME protocol stack consists of:
MME supports the S1 interface with eNodeB. The integrated S1 MME interface stack consists ofIP,SCTP, S1AP.
MME supports S11 interface with Serving Gateway. The integrated S11 interface stack consists ofIP,UDP,eGTP-C.
The SGW consists of
SGW supports S11 interface with MME and S5/S8 interface with PGW. The integrated control plane stack for these interfaces consists ofIP,UDP,eGTP-C.
SGW supports the S1-U interface with eNodeB and S5/S8 data plane interface with PGW. The integrated data plane stack for these interfaces consists ofIP,UDP,eGTP-U.
Main interfaces supported by the P-GW are:
The EPC is a packet-only core network. It does not have acircuit-switcheddomain, which is traditionally used for phone calls andSMS.
3GPP specified two solutions for voice:
3GPP specified three solutions for SMS:
CSFB and SMS over SGs are seen as interim solutions, the long term beingIMS.[4]
The UE can connect to the EPC using several access technologies. These access technologies are composed of:
It is up to the network operator to decide whether a non-3GPP access technology is trusted or untrusted.
It is worth noting that these trusted/untrusted categories do not apply to 3GPP accesses.
The 3GPP delivers standards in parallel releases, which compose consistent sets of specifications and features.
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Voice over Long-Term Evolution(acronymVoLTE) is anLTEhigh-speedwireless communicationstandard forvoice callsandSMSusingmobile phonesand data terminals.[1][2]VoLTE has up to three times more voice[3]and data capacity than older3GUMTSand up to six times more than2GGSM. It uses less bandwidth because VoLTE's packetheadersare smaller than those of unoptimizedVoIP/LTE. VoLTE calls are usually charged at the same rate as other calls.
To be able to make a VoLTE call, the device, its firmware, and the mobile telephone providers on each end, as well as the inter-carrier connectivity must all implement the service in the area, and be able to work together. VoLTE has been marketed as "HD voice" by some carriers, but this is a broader concept. Moreover, HD+ (EVS) is used only in LTE andNR; HD voice was available in 3G too.
VoLTE is based on theIP Multimedia Subsystem(IMS) architectural framework, with specific profiles forcontrolandmedia planesof voice service. This facilitates VoLTE on theLTEwireless broadband service defined byGSMAin PRD IR.92.[4]The approach results in the voice service (control and media planes) being delivered as data flows within the LTE data bearer, with no dependency on (or ultimately, requirement for) thecircuit-switchedvoice network to be in the call path.
As of February 2019 there were 253 operators investing in VoLTE in 113 countries globally, including 184 operators with commercially launched VoLTE-HD voice service in 87 countries, up from 137 operators in 65 countries 12 months previously, according to data from theGlobal Mobile Suppliers Association.[5]By August 2019, these numbers had risen to 262 operators investing in VoLTE in 120 countries and 194 operators with launched VoLTE-HD voice services in 91 countries.[6]
VoLTERoaminghistorically was required to make VoLTE Calls when roaming on another4G/LTEnetwork. Now countries with only 3G cores use 3G-to-VoLTE Roaming Interworking.[7]
Devices without VoLTE Roaming cannot make VoLTE calls when roaming on another network. VoLTE Roaming uses the S8HR Architecture, this architecture routes the calls to the home mobile network or to a 3G home network using 3G-to-VoLTE Roaming Interworking .[8]Roamingdevices that lack VoLTE Roaming support can use2Gor3GNetworks (if available) for making and receiving calls (via Circuit Switched Fallback). In countries without either2Gor3GNetworks, Roaming devices will not have access to call service from the connected Roaming Network.
VoLTE Roaming Support requires anAndroidDevice withAndroid12(2021) or newer or aniPhonewithiOS15(2021) or newer.[9]As of April 2023 Devices fromAndroid4-11made up approximately 70% of the Global Android Device Market according toGoogle.[10]These older devices are largely in demographics that are less likely to roam.[citation needed]
Not all devices that have been sold as 'VoLTE capable' support making calls to Emergency Numbers over 4G/LTE with VoLTE.[11]Some carriers and manufacturers have disabled the ability for phones to call Emergency Services with VoLTE and the devices are reliant on 2G or 3G Networks to make calls toEmergency Services.[12]
In 2022 at the European Emergency Number Association (EENA) Conference Telecoms Expert Rudolf van der Berg made a presentation to the Conference outlining serious compatibility issues with VoLTE Calling and Emergency Calling. One of the major issues he raised is that many 4G/LTE Phones (both European & International) are completely unable to call (911/112)Emergency serviceswithout the presence of 2G/3G (Circuit Switched Calling) Networks.[13]
A device can have working VoLTE Calling (IMS Registration) on a network but may not be able to successfully make calls to emergency numbers over 4G. For Android devices there are methods to test a device for 4G Emergency Calling support, however such testing can require third-party software and tools to perform. Simply dialing an Emergency Number on a 4G device isnotsufficient to test if a device can make VoLTE Emergency Calls.[14]
Depending on signal strength and other factors a device may default to 2G or 3G networks (if available). Furthermore, a 4G/LTE device may say“Emergency Calls Only”within the system settings or notifications area but that message does not prove the device can actually make an Emergency call over 4G/LTE.[14]Additionally a device may be configured for 4G Emergency Calls in a given region but fail to connect when placing a 4G Call in another country. These devices will generally get stuck on 'calling' and the call will never go through, even though a 2G or 3G network is available.[14]
In March 2024 prior to the Switch-off of3GNetworks inAustralia, theFederal Governmentannounced that more than 740,0004GVoLTE enabled phones may no longer be able to call Emergency Services after the3GNetworks were switched off.[15]In early April 2024 this number was increased to more than 1 million devices in the media with no change to the government reporting. After the completion of the review the number was less than 70,000 of devices that may not be able to call Emergency Services.[citation needed]
Telstrawas originally set to switch off their 3G Network on 30 June 2024. Telstra extended their switch off to 31 August in early May 2024.[16]On 14 August 2024, Telstra and Optus further extended the 3G switch off date to 28 October 2024.[17]Vodafonecompleted their 3G switch off in early January 2024.[18]
There have been several issues with the VoLTE deployment:
VoLTE has been supported withQualcomm SnapdragonChipsets since at least 2013/2014 (e.g. Snapdragon 800/801), however not allAndroiddevices sold have VoLTE enabled in software by the manufacturer.[23][24]In many instances devices will also lack the correct carrier network configurations/profiles to support VoLTE calling on all networks.[25]
Unlike calling with2Gand3Gthere is no single configuration for VoLTE that all devices and networks universally support. Some networks support theGSMAIR.92 'Open Market Device' Configuration.[26]This configuration is intended to be a generic/global VoLTE configuration that can be used by Open Market (non-carrier) devices.[27]4G/LTEDevices that lack native VoLTE calling support are reliant on 2G/3G Networks to make or receive calls (via Circuit Switched Fallback - CSFB) and without either2Gor3GNetworks those devices do not have call service.
A device may be marketed as having VoLTE support, however the device may only be able to make calls on some networks due to varying network configurations and VoLTE standardisation issues.[13]
In some instances the retail versions of devices have been sold without VoLTE Calling on any networks (depending on brand/market/region). However the exact same device purchased directly from a carrier (with carrier software) will support VoLTE on that carrier network.[28]Equally some handsets purchased from another carrier or from another market may not be configured (in software) to support VoLTE on all networks within a given country. This issue primarily affectsAndroidPhones and non-Apple devices. TheiPhone 6(2014) withiOS 10and newer support VoLTE calling on most networks, theiPhone 5and5sthough4G/LTEdevices do not support VoLTE calling.[29][30][31]
For example, for an Android device to have VoLTE Calling on theTelstranetwork the device needs to be running a Telstra Modem Configuration. Devices that are running theGSMA'Open Market Device' configuration or a configuration from another carrier cannot get working VoLTE Calling on the Telstra network. This limitation prevents Telstra customers from using Open Market Devices which do not have native Firmware support for the Telstra Network. Open Market configuration devices can work on competing Australian providersOptus&Vodafone.[26][28]
With someQualcommbased Android devices it is possible to modify the device firmware with special software and manually load a compatible carrier modem configuration.[26]By modifying the firmware customers can use VoLTE calling, however the carrier may not recognise those devices as supported despite working correctly.
For example, starting in May 2024 Telstra starting forcing a pre-recorded message with all outbound calls advising affected customers of the need to upgrade in advance of the 3G shutdown in August. However even customers with modified devices with working VoLTE calling on Telstra were hearing the message every time they made a 4G VoLTE call.[32]This is due to Telstra relying on established lists of 'compatible' devices (i.e. DeviceIMEI/TAC codes).
Android users are able to confirm if VoLTE is working by checking for the Device 'IMSStatus' within a hidden Radio Info Debug menu.[26][33]
If theIMSStatus shows "IMS Registration: Registered" and "Voice over LTE: Available" then VoLTE is enabled and working. An IMS Status of "Not Registered" and "Voice over LTE: Unavailable" indicates VoLTE is not enabled or working. However the IMS Status debugdoes notconfirm working 4G Emergency Calling support.[14]
For VoLTE calling to be "Available" on a device, VoLTE has to be both provisioned/enabled in the Firmware and a carrier compatible modem configuration/profile must be loaded on the device. Typically the modem configurations are automatically loaded by the device firmware when inserting asim card. However not all devices are configured to detect the sim cards for all networks and enable VoLTE Calling.[26]
The IMS Status debug can also indicate ifWi-Fi Calling(Voice over Wi-Fi) and Video Calling (ViLTE/Video Telephony) are available. (Note: For Wi-Fi Calling to say Available the device has to be connected to a suitable Wi-Fi Network).
Additionally, devices with a "UT Interface" status of "Unavailable" will be unable to changeCall Forwardingor Call Busy Settings over 4G/LTE. Note: UT Interface is not required for VoLTE Calling, UT Interface is only required to changesupplementary servicesettings (i.e. call forwarding) on a 4G/LTE only network. Devices without an "Available" UT Interface are reliant on 2G/3G networks to change call forwarding/busy settings.
Beginning in August 2012,MetroPCSlaunched the world's first commercial VoLTE services inDallas, Texas, in theUnited States, alongside the first VoLTE phone, the LG Connect 4G.[34]In May 2014,Singtelintroduced the world's first commercial "full-featured" VoLTE service in Singapore, only in combination withGalaxy Note 3, it was subsequently expanded.[35]In June 2014,KTshowcased the world's first cross-borderroaming servicesbased on Voice over LTE. The South Koreanoperatorpartnered withChina Mobileto develop VoLTE roaming services.[36]
In November 2014,VerizonandAT&Tannounced the companies are enabling VoLTE-to-VoLTE connections between their respective customers. VoLTE interoperability between Verizon and AT&T customers began in 2015. Testing and design were performed between both companies using third party networks such asAlcatel-Lucent.[37]This was stated to have been completed in November 2017.[38]
On July 11, 2015, SEATEL Cambodia announced the world's first commercial 100% VoLTE service without 2G/3G in Cambodia.[39][40][41][42][43]
As of 2020, almost all new phones for sale have the potential to support VoLTE.[citation needed]
On December 31, 2022,Verizonshut down theirCDMAnetwork, therefore requiring devices to supportLTEor5G. Customers withCDMA-only devices andLTEdevices without VoLTE support would have been required to switch to a VoLTE-capable device by that date. Verizon stopped activating CDMA-only devices on their network in 2018, and had previously planned to shut down 3G service in 2019, but extended the timeline for shutting down the 3G network twice[44]— first to December 31, 2020, and then to December 31, 2022, which the VP of Network Engineering says "will not be extended again." The company indicated the delays were in an effort to "minimize disruptions" to its customers still utilizing the 3G network. As of March 2021, less than 1% of Verizon's customers were still using 3G, and many of the 3G-connected devices are integrated devices, such as smart utility meters and home burglar alarms.[45]
Additionally, certain Verizon-compatible handsets were blocked from Verizon's CDMA network even before December 31, 2022, even if the device supported CDMA (for instance, unlocked devices with support forSprintorChina Telecom), therefore requiring VoLTE support when used on Verizon. This includes5G-capable andOnePlushandsets. Devices lacking CDMA support starting with thePixel 6andiPhone 14series as well as select older devices sold on GSM carriers will only work on Verizon in VoLTE mode.
To ensure compatibility,3GPPdemand at leastAMR-NB codec (narrow band), but the recommended speech codec for VoLTE isAdaptive Multi-Rate Wideband(AMR-WB), also known under the trademark HD Voice after GSMA's certification program. This codec is mandated in 3GPP networks that are capable of 16 kHz sampling.[46]
In addition, many carriers and devices can useEnhanced Voice Services(EVS). This is an up to superwideband (20–16,000 Hz) or fullband (20–20,000 Hz) codec backwards-compatible with AMR-WB.[47]This codec is also known under the trademark HD Voice+, after GSMA's certification program.[48]GSMA has proposed to make EVS mandatory just like AMR-WB.[47](Both the carrier(s), any interconnect and the two calling devices must be capable of using the codec for it to be used.) The AMR-WB+ codec has a wide bit-rate range, from 5.2 to 48 kbit/s. EVS offers a wide range of bit rates from 5.9 kbit/s to 128 kbit/s, allowing service providers tooptimize network capacity and call quality as desiredfor their service, so VoLTE does not ensure high call quality.[47]
Fraunhofer IIShas previously demonstrated an implementation of theAAC-ELDcodec in VoLTE that they call "Full-HD Voice". It has not gained any standard status or real-world adoption.[49]They have since reused the term "Full-HD Voice" for EVS in fullband mode (HD+ is also used).[47]
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E.164is aninternational standard(ITU-TRecommendation), titledThe international public telecommunication numbering plan, that defines anumbering planfor the worldwidepublic switched telephone network(PSTN) and some other datanetworks.
E.164 defines a general format for internationaltelephone numbers. Plan-conforming telephone numbers are limited to only digits and to a maximum of fifteen digits.[1]The specification divides the digit string into a country code of one to three digits, and the subscriber telephone number of a maximum of twelve digits.
Recommendation E.164 is part of a series of standards (E.160–E.169,Numbering plan of the international telephone service) that represent a redefinition of the earlier specifications in Recommendation E.29 in the Red Books of 1960 and 1964. In 1960, an international numbering plan was defined for Europe and parts of western Asia, and some Mediterranean countries.[2]In 1964, E.29 was expanded with a global code system based onworld numbering zones. In the 1968 White Book, the definition of country codes was relegated to ITU Recommendation E.161. The first issue of E.164 was published in 1988 in Blue Book Fascicle II.2, under the titleNumbering Plan for the ISDN Era.
E.163 was the formerITU-Trecommendation for describingtelephonenumbers for thepublic switched telephone network(PSTN). In the United States, this was formerly referred to as adirectory number. E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.[3]
This recommendation describes the procedures and criteria for the reservation, assignment, and reclamation of E.164 country codes and associatedidentification code(IC) assignments.[4]The criteria and procedures are provided as a basis for the effective and efficient utilization of the available E.164 numbering resources.
This recommendation contains the criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code991for the purpose of conducting an international non-commercial trial.[5]
This recommendation describes the principles, criteria, and procedures for the assignment and reclamation of resources within a shared E.164 country code for groups of countries.[6]These shared country codes will coexist with all other E.164-based country codes assigned by the ITU. The resource of the shared country code consists of acountry codeand agroup identification code(CC + GIC) and provides the capability for a group of countries to provide telecommunication services within the group. The Secretariat of the ITU Standardization Sector (ITU-T), the Telecommunication Standardization Bureau (TSB) is responsible for the assignment of the CC + GIC.
The E.164 recommendation provides the telephone number structure and functionality for five categories of telephone numbers used in international publictelecommunications.
For each of the categories, it details the components of the numbering structure and the digit analysis required for successfulroutingof calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialing procedures, and addressing for Geographic-basedISDNcalls. Specific E.164-based applications which differ in usage are defined in separate recommendations.
The number categories are all based on a fifteen-digit numbering space. Before 1997, only twelve digits were allowed. The definition does not include anyinternational call prefixes, necessary for a call to reach international circuits from inside the country of call origination.
[1]Figure 2
E.164 numbers were originally defined for use in the worldwidepublic switched telephone network(PSTN). The early PSTN collected routing digits from users (e.g. on a dial pad), signaled those digits to each telephony switch, and used the numbers to determine how to ultimately reach the called party.
ITU-TE.123entitledNotation for national and international telephone numbers, e-mail addresses and web addressesprovides guidance when printing E.164 telephone numbers. This format includes the recommendation of prefixing international telephone numbers with a plus sign (+) and using only spaces for digit grouping.
The presentation of a telephone number with the plus sign (+) indicates that the number should be dialed with aninternational calling prefix, in place of the plus sign. The number is presented starting with thetelephone country code. This is called theglobalizedformat of an E.164 number, and is defined in the Internet Engineering Task ForceRFC2806.[7]The international calling prefix is atrunk codeto reach an international circuit in the country of call origination.[8]
Some national telephone administrations and telephone companies have implemented anInternet-based database for their numbering spaces. E.164 numbers may be registered in theDomain Name System(DNS) of theInternetin which the second-level domain e164.arpa has been reserved fortelephone number mapping(ENUM). In the system, any telephone number may be mapped into adomain nameusing a reverse sequence of subdomains for each digit. For example, the telephone number+19995550123translates to the domain name3.2.1.0.5.5.5.9.9.9.1.e164.arpa. When a number is mapped, a DNS query may be used to locate the service facilities on the Internet that accept and process telephone calls to the owner of record of the number, using, for example, theSession Initiation Protocol(SIP), a call-signalingVoIPprotocol whoseSIP addressesare similar in format (user@domain...) to e-mail addresses. This allows a direct, end-to-end Internet connection without passing through the public switched telephone network.
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Network switching subsystem(NSS) (orGSM core network) is the component of aGSMsystem that carries outcall outandmobility managementfunctions formobile phonesroamingon thenetwork of base stations. It is owned and deployed bymobile phone operatorsand allows mobile devices to communicate with each other andtelephonesin the widerpublic switched telephone network(PSTN). The architecture contains specific features and functions which are needed because the phones are not fixed in one location.
The NSS originally consisted of the circuit-switchedcore network, used for traditionalGSM servicessuch as voice calls,SMS, andcircuit switched datacalls. It was extended with an overlay architecture to provide packet-switched data services known as theGPRS core network. This allows mobile phones to have access to services such asWAP,MMSand theInternet.
Themobile switching center(MSC) is the primary service delivery node for GSM/CDMA, responsible forroutingvoice calls and SMS as well as other services (such as conference calls, FAX, and circuit-switched data).
The MSC sets up and releases theend-to-end connection, handles mobility and hand-over requirements during the call and takes care of charging and real-time prepaid account monitoring.
In the GSM mobile phone system, in contrast with earlier analogue services, fax and data information is sent digitally encoded directly to the MSC. Only at the MSC is this re-coded into an "analogue" signal (although actually this will almost certainly mean sound is encoded digitally as apulse-code modulation(PCM) signal in a 64-kbit/s timeslot, known as aDS0in America).
There are various different names for MSCs in different contexts which reflects their complex role in the network, all of these terms though could refer to the same MSC, but doing different things at different times.
Thegateway MSC(G-MSC) is the MSC that determines which "visited MSC" (V-MSC) the subscriber who is being called is currently located at. It also interfaces with the PSTN. All mobile to mobile calls and PSTN to mobile calls are routed through a G-MSC. The term is only valid in the context of one call, since any MSC may provide both the gateway function and the visited MSC function. However, some manufacturers design dedicated high capacity MSCs which do not have anybase station subsystems(BSS) connected to them. These MSCs will then be the gateway MSC for many of the calls they handle.
Thevisited MSC(V-MSC) is the MSC where a customer is currently located. Thevisitor location register(VLR) associated with this MSC will have the subscriber's data in it.
Theanchor MSCis the MSC from which ahandoverhas been initiated. Thetarget MSCis the MSC toward which a handover should take place. Amobile switching center serveris a part of the redesigned MSC concept starting from3GPP Release 4.
Themobile switching center serveris a soft-switch variant (therefore it may be referred to as mobile soft switch, MSS) of the mobile switching center, which provides circuit-switched calling mobility management, and GSM services to the mobile phonesroamingwithin the area that it serves. The functionality enables split control between (signaling ) and user plane (bearer in network element called as media gateway/MG), which guarantees better placement of network elements within the network.
MSS andmedia gateway(MGW) makes it possible to cross-connect circuit-switched calls switched by using IP, ATM AAL2 as well asTDM. More information is available in 3GPP TS 23.205.
The termCircuit switching(CS) used here originates from traditional telecommunications systems. However, modern MSS and MGW devices mostly use genericInternettechnologies and formnext-generation telecommunication networks. MSS software may run on generic computers orvirtual machinesincloudenvironment.
The MSC connects to the following elements:
Tasks of the MSC include:
Thehome location register(HLR) is a central database that contains details of each mobile phone subscriber that is authorized to use the GSM core network. There can be several logical, and physical, HLRs perpublic land mobile network(PLMN), though oneinternational mobile subscriber identity(IMSI)/MSISDN pair can be associated with only one logical HLR (which can span several physical nodes) at a time.
The HLRs store details of everySIM cardissued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is theprimary keyto each HLR record.
Another important item of data associated with the SIM are the MSISDNs, which are thetelephone numbersused by mobile phones to make and receive calls. The primary MSISDN is the number used for making and receiving voice calls and SMS, but it is possible for a SIM to have other secondary MSISDNs associated with it forfaxand data calls. Each MSISDN is also aunique keyto the HLR record. The HLR data is stored for as long as a subscriber remains with the mobile phone operator.
Examples of other data stored in the HLR against an IMSI record is:
The HLR is a system which directly receives and processesMAPtransactions and messages from elements in the GSM network, for example, the location update messages received as mobile phones roam around.
The HLR connects to the following elements:
The main function of the HLR is to manage the fact that SIMs and phones move around a lot. The following procedures are implemented to deal with this:
Theauthentication center(AuC) is a function toauthenticateeachSIM cardthat attempts to connect to thegsmcore network (typically when the phone is powered on). Once the authentication is successful, the HLR is allowed to manage the SIM and services described above. Anencryption keyis also generated that is subsequently used to encrypt all wireless communications (voice, SMS, etc.) between the mobile phone and the GSM core network.
If the authentication fails, then no services are possible from that particular combination of SIM card and mobile phone operator attempted. There is an additional form of identification check performed on the serial number of the mobile phone described in the EIR section below, but this is not relevant to the AuC processing.
Proper implementation of security in and around the AuC is a key part of an operator's strategy to avoidSIM cloning.
The AuC does not engage directly in the authentication process, but instead generates data known astripletsfor the MSC to use during the procedure. The security of the process depends upon ashared secretbetween the AuC and the SIM called theKi. TheKiis securely burned into the SIM during manufacture and is also securely replicated onto the AuC. ThisKiis never transmitted between the AuC and SIM, but is combined with the IMSI to produce achallenge/responsefor identification purposes and an encryption key calledKcfor use in over the air communications.
The AuC connects to the following elements:
The AuC stores the following data for each IMSI:
When the MSC asks the AuC for a new set of triplets for a particular IMSI, the AuC first generates a random number known asRAND. ThisRANDis then combined with theKito produce two numbers as follows:
The numbers (RAND, SRES,Kc) form the triplet sent back to the MSC. When a particular IMSI requests access to the GSM core network, the MSC sends theRANDpart of the triplet to the SIM. The SIM then feeds this number and theKi(which is burned onto the SIM) into the A3 algorithm as appropriate and an SRES is calculated and sent back to the MSC. If this SRES matches with the SRES in the triplet (which it should if it is a valid SIM), then the mobile is allowed to attach and proceed with GSM services.
After successful authentication, the MSC sends the encryption keyKcto thebase station controller(BSC) so that all communications can be encrypted and decrypted. Of course, the mobile phone can generate theKcitself by feeding the same RAND supplied during authentication and theKiinto the A8 algorithm.
The AuC is usually collocated with the HLR, although this is not necessary. Whilst the procedure is secure for most everyday use, it is by no means hack proof. Therefore, a new set of security methods was designed for 3G phones.
In practice, A3 and A8 algorithms are generally implemented together (known as A3/A8, seeCOMP128). An A3/A8 algorithm is implemented in Subscriber Identity Module (SIM) cards and in GSM network Authentication Centers. It is used to authenticate the customer and generate a key for encrypting voice and data traffic, as defined in 3GPP TS 43.020 (03.20 before Rel-4). Development of A3 and A8 algorithms is considered a matter for individual GSM network operators, although example implementations are available. To encrypt Global System for Mobile Communications (GSM) cellular communications A5 algorithm is used.[1]
TheVisitor Location Register (VLR)is a database of the MSs (Mobile stations) that have roamed into the jurisdiction of the Mobile Switching Center (MSC) which it serves. Each mainbase transceiver stationin the network is served by exactly one VLR (oneBTSmay be served by many MSCs in case of MSC in pool), hence a subscriber cannot be present in more than one VLR at a time.
The data stored in the VLR has either been received from theHome Location Register (HLR), or collected from the MS. In practice, for performance reasons, most vendors integrate the VLR directly to the V-MSC and, where this is not done, the VLR is very tightly linked with the MSC via a proprietary interface. Whenever an MSC detects a new MS in its network, in addition to creating a new record in the VLR, it also updates the HLR of the mobile subscriber, apprising it of the new location of that MS. If VLR data is corrupted it can lead to serious issues with text messaging and call services.
Data stored include:
The primary functions of the VLR are:
EIRis a system that handles real-time requests to check theIMEI(checkIMEI) of mobile devices that come from the switching equipment (MSC,SGSN,MME). The answer contains the result of the check:
The switching equipment must use the EIR response to determine whether or not to allow the device to register or re-register on the network. Since the response of switching equipment to ‘greylisted’ and ‘unknown equipment’ responses is not clearly described in the standard, they are most often not used.
Most often, EIR uses the IMEI blacklist feature, which contains the IMEI of the devices that need to be banned from the network. As a rule, these are stolen or lost devices. Mobile operators rarely use EIR capabilities to block devices on their own. Usually blocking begins when there is a law in the country, which obliges all cellular operators of the country to do so. Therefore, in the delivery of the basic components of the network switching subsystem (core network) is often already present EIR with basic functionality, which includes a ‘whitelisted’ response to all CheckIMEI and the ability to fill IMEI blacklist, which will be given a ‘blacklisted’ response.
When the legislative framework for blocking registration of devices in cellular networks appears in the country, the telecommunications regulator usually has a Central EIR (CEIR) system, which is integrated with the EIR of all operators and transmits to them the actual lists of identifiers that must be used when processing CheckIMEI requests. In doing so, there may be many new requirements for EIR systems that are not present in the legacy EIR:
Other functions may be required in individual cases. For example, Kazakhstan has introduced mandatory registration of devices and their binding to subscribers. But when a subscriber appears in the network with a new device, the network operation is not blocked completely, and the subscriber is allowed to register the device. To do this, there are blocked all services, except the following: calls to a specific service number, sending SMS to a specific service number, and all Internet traffic is redirected to a specific landing page. This is achieved by the fact that EIR can send commands to several MNO systems (HLR,PCRF,SMSC, etc.).
The most common suppliers of individual EIR systems (not as part of a complex solution) are the companies BroadForward, Mahindra Comviva, Mavenir, Nokia, Eastwind.
Connected more or less directly to the GSM core network are many other functions.
Thebilling centeris responsible for processing the toll tickets generated by the VLRs and HLRs and generating a bill for each subscriber. It is also responsible for generating billing data of roaming subscriber.
Themultimedia messaging servicecentersupports the sending of multimedia messages (e.g., images,audio,videoand their combinations) to (or from) MMS-bluetooth.
Thevoicemailsystemrecords and stores voicemail.
According to U.S. law, which has also been copied into many other countries, especially in Europe, all telecommunications equipment must provide facilities for monitoring the calls of selected users. There must be some level of support for this built into any of the different elements. The concept oflawful interceptionis also known, following the relevant U.S. law, asCALEA.
Generally, lawful Interception implementation is similar to the implementation of conference call. While A and B are talking with each other, C can join the call and listen silently.
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In mobile telecommunications network routing,E.214is one of three prevailingnumbering plansused for deliveringmobility managementrelated messages.[1]
TheE.164numbering plan, which is a maximum of 15 digits and usually written with a "+" prefix, is the historic first-generation format representing the phone number. The E.212 is a second-generation number plan used in America, extended to include the subscriber's MSIN (Mobile Subscription Identification Number) within the network's customer base. The E.214, developed under EuropeanGSM(Global System for Mobile Communications) standards, is a comparable extended second-generation format used outside America and can be more or less than 15 digits.[2]
In routing a transatlantic mobile call, numbers routed from European networks are converted from E.214 numbers into E.212 numbers at the boundary incoming toward America (this can mean theSignaling Transfer Pointat the edge of the American operator's network). In the outgoing direction, from America toward the rest of the world, numbers are converted from the E.212 standard to the E.214 standard.
This process, calledglobal title translation, is theSS7equivalent toIProuting. E.214 numbers are routed separately fromE.164numbers since they are marked with a differentNumbering Plan Indicator. However, it is possible to reuse theGlobal Titleanalysis tables usedE.164numbers everywhere except for the final destination network of the message. This saves considerable administrative work.
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https://en.wikipedia.org/wiki/E.214
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TheSession Initiation Protocol(SIP) is asignaling protocolused for initiating, maintaining, and terminatingcommunication sessionsthat include voice, video and messaging applications.[1]SIP is used inInternet telephony, in private IP telephone systems, as well as mobile phone calling overLTE(VoLTE).[2]
The protocol defines the specific format of messages exchanged and the sequence of communications for cooperation of the participants. SIP is atext-based protocol, incorporating many elements of theHypertext Transfer Protocol(HTTP) and theSimple Mail Transfer Protocol(SMTP).[3]A call established with SIP may consist of multiplemedia streams, but no separate streams are required for applications, such astext messaging, that exchange data as payload in the SIP message.
SIP works in conjunction with several other protocols that specify and carry the session media. Most commonly, media type and parameter negotiation and media setup are performed with theSession Description Protocol(SDP), which is carried as payload in SIP messages. SIP is designed to be independent of the underlyingtransport layerprotocol and can be used with theUser Datagram Protocol(UDP), theTransmission Control Protocol(TCP), and theStream Control Transmission Protocol(SCTP). For secure transmissions of SIP messages over insecure network links, the protocol may be encrypted withTransport Layer Security(TLS). For the transmission of media streams (voice, video) the SDP payload carried in SIP messages typically employs theReal-time Transport Protocol(RTP) or theSecure Real-time Transport Protocol(SRTP).
SIP was originally designed byMark Handley,Henning Schulzrinne,Eve SchoolerandJonathan Rosenbergin 1996 to facilitate establishingmulticastmultimedia sessions on theMbone. The protocol was standardized asRFC2543in 1999. In November 2000, SIP was accepted as a3GPPsignaling protocol and permanent element of theIP Multimedia Subsystem(IMS) architecture for IP-based streaming multimedia services incellular networks. In June 2002 the specification was revised inRFC3261[4]and various extensions and clarifications have been published since.[5]
SIP was designed to provide a signaling and call setup protocol for IP-based communications supporting the call processing functions and features present in thepublic switched telephone network(PSTN) with a vision of supporting new multimedia applications. It has been extended forvideo conferencing,streaming mediadistribution,instant messaging,presence information,file transfer,Internet faxandonline games.[1][6][7]
SIP is distinguished by its proponents for having roots in the Internet community rather than in thetelecommunications industry. SIP has been standardized primarily by theInternet Engineering Task Force(IETF), while other protocols, such asH.323, have traditionally been associated with theInternational Telecommunication Union(ITU).
SIP is only involved in the signaling operations of a media communication session and is primarily used to set up and terminate voice or video calls. SIP can be used to establish two-party (unicast) or multiparty (multicast) sessions. It also allows modification of existing calls. The modification can involve changing addresses orports, inviting more participants, and adding or deleting media streams. SIP has also found applications in messaging applications, such as instant messaging, and event subscription and notification.
SIP works in conjunction with several other protocols that specify the media format and coding and that carry the media once the call is set up. For call setup, the body of a SIP message contains aSession Description Protocol(SDP) data unit, which specifies the media format, codec and media communication protocol. Voice and video media streams are typically carried between the terminals using theReal-time Transport Protocol(RTP) orSecure Real-time Transport Protocol(SRTP).[3][8]
Every resource of a SIP network, such as user agents, call routers, and voicemail boxes, are identified by aUniform Resource Identifier(URI). The syntax of the URI follows the general standard syntax also used inWeb servicesand e-mail.[9]The URI scheme used for SIP issipand a typical SIP URI has the formsip:username@domainnameorsip:username@hostport, wheredomainnamerequires DNSSRV recordsto locate the servers for SIP domain whilehostportcan be anIP addressor afully qualified domain nameof the host and port. Ifsecure transmissionis required, the schemesipsis used.[10][11]
SIP employs design elements similar to the HTTP request and response transaction model.[12]Each transaction consists of a client request that invokes a particular method or function on the server and at least one response. SIP reuses most of the header fields, encoding rules and status codes of HTTP, providing a readable text-based format.
SIP can be carried by severaltransport layerprotocols includingTransmission Control Protocol(TCP),User Datagram Protocol(UDP), andStream Control Transmission Protocol(SCTP).[13][14]SIP clients typically use TCP or UDP onport numbers5060 or 5061 for SIP traffic to servers and other endpoints. Port 5060 is commonly used for non-encrypted signaling traffic whereas port 5061 is typically used for traffic encrypted withTransport Layer Security(TLS).
SIP-based telephony networks often implement call processing features ofSignaling System 7(SS7), for which special SIP protocol extensions exist, although the two protocols themselves are very different. SS7 is a centralized protocol, characterized by a complex central network architecture and dumb endpoints (traditional telephone handsets). SIP is aclient-serverprotocol of equipotent peers. SIP features are implemented in the communicating endpoints, while the traditional SS7 architecture is in use only between switching centers.
The network elements that use the Session Initiation Protocol for communication are calledSIP user agents. Eachuser agent(UA) performs the function of auser agent client(UAC) when it is requesting a service function, and that of auser agent server(UAS) when responding to a request. Thus, any two SIP endpoints may in principle operate without any intervening SIP infrastructure. However, for network operational reasons, for provisioning public services to users, and for directory services, SIP defines several specific types of network server elements. Each of these service elements also communicates within the client-server model implemented in user agent clients and servers.[15]
A user agent is a logical network endpoint that sends or receives SIP messages and manages SIP sessions. User agents have client and server components. The user agent client (UAC) sends SIP requests. The user agent server (UAS) receives requests and returns a SIP response. Unlike other network protocols that fix the roles of client and server, e.g., in HTTP, in which a web browser only acts as a client, and never as a server, SIP requires both peers to implement both roles. The roles of UAC and UAS only last for the duration of a SIP transaction.[6]
A SIP phone is anIP phonethat implements client and server functions of a SIP user agent and provides the traditional call functions of a telephone, such as dial, answer, reject, call hold, and call transfer.[16][17]SIP phones may be implemented as a hardware device or as asoftphone. As vendors increasingly implement SIP as a standard telephony platform, the distinction between hardware-based and software-based SIP phones is blurred and SIP elements are implemented in the basic firmware functions of many IP-capable communications devices such assmartphones.
In SIP, as in HTTP, theuser agentmay identify itself using a message header field (User-Agent), containing a text description of the software, hardware, or the product name. The user agent field is sent in request messages, which means that the receiving SIP server can evaluate this information to perform device-specific configuration or feature activation. Operators of SIP network elements sometimes store this information in customer account portals,[18]where it can be useful in diagnosing SIP compatibility problems or in the display of service status.
A proxy server is a network server with UAC and UAS components that functions as an intermediary entity for the purpose of performing requests on behalf of other network elements. A proxy server primarily plays the role of call routing; it sends SIP requests to another entity closer to the destination. Proxies are also useful for enforcing policy, such as for determining whether a user is allowed to make a call. A proxy interprets, and, if necessary, rewrites specific parts of a request message before forwarding it.
SIP proxy servers that route messages to more than one destination are called forking proxies. The forking of a SIP request establishes multiple dialogs from the single request. Thus, a call may be answered from one of multiple SIP endpoints. For identification of multiple dialogs, each dialog has an identifier with contributions from both endpoints.
A redirect server is a user agent server that generates3xx (redirection) responsesto requests it receives, directing the client to contact an alternate set of URIs. A redirect server allows proxy servers to direct SIP session invitations to external domains.
A registrar is a SIP endpoint that provides a location service. It accepts REGISTER requests, recording the address and other parameters from the user agent. For subsequent requests, it provides an essential means to locate possible communication peers on the network. The location service links one or more IP addresses to the SIP URI of the registering agent. Multiple user agents may register for the same URI, with the result that all registered user agents receive the calls to the URI.
SIP registrars are logical elements and are often co-located with SIP proxies. To improve network scalability, location services may instead be located with a redirect server.
Session border controllers(SBCs) serve asmiddleboxesbetween user agents and SIP servers for various types of functions, including network topology hiding and assistance inNAT traversal. SBCs are an independently engineered solution and are not mentioned in the SIP RFC.
Gatewayscan be used to interconnect a SIP network to other networks, such as the PSTN, which use different protocols or technologies.
SIP is a text-based protocol with syntax similar to that of HTTP. There are two different types of SIP messages: requests and responses. The first line of a request has amethod, defining the nature of the request, and a Request-URI, indicating where the request should be sent.[19]The first line of a response has aresponse code.
Requests initiate a functionality of the protocol. They are sent by a user agent client to the server and are answered with one or moreSIP responses, which return a result code of the transaction, and generally indicate the success, failure, or other state of the transaction.
Responses are sent by the user agent server indicating the result of a received request. Several classes of responses are recognized, determined by the numerical range of result codes:[20]
SIP defines a transaction mechanism to control the exchanges between participants and deliver messages reliably. A transaction is a state of a session, which is controlled by various timers. Client transactions send requests and server transactions respond to those requests with one or more responses. The responses may include provisional responses with a response code in the form1xx, and one or multiple final responses (2xx – 6xx).
Transactions are further categorized as either typeinviteor typenon-invite. Invite transactions differ in that they can establish a long-running conversation, referred to as adialogin SIP, and so include an acknowledgment (ACK) of any non-failing final response, e.g.,200 OK.
TheSession Initiation Protocol for Instant Messaging and Presence Leveraging Extensions(SIMPLE) is the SIP-based suite of standards forinstant messagingandpresence information.Message Session Relay Protocol(MSRP) allows instant message sessions and file transfer.
The SIP developer community meets regularly at conferences organized by SIP Forum to test interoperability of SIP implementations.[22]TheTTCN-3test specification language, developed by a task force atETSI(STF 196), is used for specifying conformance tests for SIP implementations.[23]
When developing SIP software or deploying a new SIP infrastructure, it is important to test the capability of servers and IP networks to handle certain call load: number of concurrent calls and number of calls per second. SIP performance tester software is used to simulate SIP and RTP traffic to see if the server and IP network are stable under the call load.[24]The software measures performance indicators like answer delay,answer/seizure ratio, RTPjitterandpacket loss,round-trip delay time.
SIP connectionis a marketing term forvoice over Internet Protocol(VoIP) services offered by manyInternet telephony service providers(ITSPs). The service provides routing of telephone calls from a client'sprivate branch exchange(PBX) telephone system to the PSTN. Such services may simplify corporate information system infrastructure by sharingInternet accessfor voice and data, and removing the cost forBasic Rate Interface(BRI) orPrimary Rate Interface(PRI) telephone circuits.
SIP trunkingis a similar marketing term preferred for when the service is used to simplify a telecom infrastructure by sharing the carrier access circuit for voice, data, and Internet traffic while removing the need for PRI circuits.[25][26]
SIP-enabled video surveillance cameras can initiate calls to alert the operator of events, such as the motion of objects in a protected area.
SIP is used inaudio over IPforbroadcastingapplications where it provides an interoperable means for audio interfaces from different manufacturers to make connections with one another.[27]
The U.S.National Institute of Standards and Technology(NIST), Advanced Networking Technologies Division provides a public-domainJavaimplementation[28]that serves as areference implementationfor the standard. The implementation can work in proxy server or user agent scenarios and has been used in numerous commercial and research projects. It supportsRFC3261in full and a number of extension RFCs includingRFC6665(event notification) andRFC3262(reliable provisional responses).
Numerous other commercial and open-source SIP implementations exist. SeeList of SIP software.
SIP-I, Session Initiation Protocol with encapsulatedISUP, is a protocol used to create, modify, and terminate communication sessions based on ISUP using SIP and IP networks. Services using SIP-I include voice, video telephony, fax and data. SIP-I and SIP-T[29]are two protocols with similar features, notably to allow ISUP messages to be transported over SIP networks. This preserves all of the detail available in the ISUP header.[a]SIP-I was defined by theITU-T, whereas SIP-T was defined by theIETF.[30]
Concerns about the security of calls via the public Internet have been addressed by encryption of the SIP protocol forsecure transmission. The URI scheme SIPS is used to mandate that SIP communication be secured withTransport Layer Security(TLS). SIPS URIs take the formsips:user@example.com.
End-to-end encryptionof SIP is only possible if there is a direct connection between communication endpoints. While a direct connection can be made viaPeer-to-peer SIPor via aVPNbetween the endpoints, most SIP communication involves multiple hops, with the first hop being from a user agent to the user agent'sITSP. For the multiple-hop case, SIPS will only secure the first hop; the remaining hops will normally not be secured with TLS and the SIP communication will be insecure. In contrast, theHTTPSprotocol provides end-to-end security as it is done with a direct connection and does not involve the notion of hops.
The media streams (audio and video), which are separate connections from the SIPS signaling stream, may be encrypted using SRTP. The key exchange for SRTP is performed withSDES(RFC4568), or withZRTP(RFC6189). When SDES is used, the keys will be transmitted via insecure SIP unless SIPS is used. One may also add aMIKEY(RFC3830) exchange to SIP to determine session keys for use with SRTP.
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H.323is a recommendation from theITU Telecommunication Standardization Sector (ITU-T)that defines the protocols to provideaudio-visualcommunication sessions on anypacket network.[1]The H.323 standard addresses call signaling and control, multimedia transport and control, and bandwidth control for point-to-point and multi-point conferences.[2]
It is widely implemented[3]by voice andvideoconferencingequipment manufacturers, is used within variousInternetreal-time applications such asGnuGKandNetMeetingand is widely deployed worldwide by service providers and enterprises for both voice andvideoservices overIPnetworks.
It is a part of the ITU-T H.32x series of protocols, which also addressmultimediacommunications overISDN, thePSTNorSS7, and3Gmobile networks.
H.323 call signaling is based on the ITU-T RecommendationQ.931protocol and is suited for transmitting calls across networks using a mixture of IP, PSTN, ISDN, andQSIGover ISDN. A call model, similar to the ISDN call model, eases the introduction ofIP telephonyinto existing networks of ISDN-basedPBXsystems, including transitions to IP-based PBXs.
Within the context of H.323, an IP-based PBX might be agatekeeperor other call control element which provides service totelephonesorvideophones. Such a device may provide or facilitate both basic services and supplementary services, such ascall transfer,park,pick-up, andhold.
The first version of H.323 was published by theITUin November 1996[4]with an emphasis of enabling videoconferencing capabilities over alocal area network(LAN), but was quickly adopted by the industry as a means of transmitting voice communication over a variety of IP networks, includingWANsand the Internet (seeVoIP).
Over the years, H.323 has been revised and re-published with enhancements necessary to better enable both voice and video functionality overpacket-switched networks, with each version beingbackward-compatiblewith the previous version.[5]Recognizing that H.323 was being used for communication not only on LANs, but over WANs and within large carrier networks, the title of H.323 was changed when published in 1998.[6]The title, which has since remained unchanged, is "Packet-Based Multimedia Communications Systems." The current version of H.323 was approved in 2009.[7]
One strength of H.323 was the relatively early availability of a set of standards not only defining the basic call model, but also the supplementary services needed to address business communication expectations.[citation needed]
H.323 was the first VoIP standard to adopt theInternet Engineering Task Force(IETF) standardReal-time Transport Protocol(RTP) to transportaudioand video over IP networks.[citation needed]
H.323 is a system specification that describes the use of several ITU-T and IETF protocols. The protocols that comprise the core of almost any H.323 system are:[8]
Many H.323 systems also implement other protocols that are defined in variousITU-T Recommendationsto provide supplementary services support or deliver other functionality to the user. Some of those Recommendations are:[citation needed]
In addition to those ITU-T Recommendations, H.323 implements various IETFRequest for Comments(RFCs) for media transport and media packetization, including theReal-time Transport Protocol(RTP).
H.323 utilizes both ITU-definedcodecsand codecs defined outside the ITU. Codecs that are widely implemented by H.323 equipment include:
All H.323 terminals providing video communications shall be capable of encoding and decoding video according to H.261QCIF. All H.323 terminals shall have an audio codec and shall be capable of encoding and decoding speech according to ITU-T Rec. G.711. All terminals shall be capable of transmitting and receivingA-lawandμ-law. Support for other audio and video codecs is optional.[7]
The H.323 system defines several network elements that work together in order to deliver rich multimedia communication capabilities. Those elements are Terminals,Multipoint Control Units(MCUs),Gateways, Gatekeepers, and Border Elements. Collectively, terminals, multipoint control units and gateways are often referred to asendpoints. H.323 uses TCP port number 1720.
While not all elements are required, at least two terminals are required in order to enable communication between two people. In most H.323 deployments, a gatekeeper is employed in order to, among other things, facilitate address resolution.
Terminals in an H.323 network are the most fundamental elements in any H.323 system, as those are the devices that users would normally encounter. They might exist in the form of a simple IP phone or a powerful high-definition videoconferencing system.
Inside an H.323 terminal is something referred to as aProtocol stack, which implements the functionality defined by the H.323 system. The protocol stack would include an implementation of the basic protocol defined in ITU-T Recommendation H.225.0 and H.245, as well as RTP or other protocols described above.
The diagram, figure 1, depicts a complete, sophisticated stack that provides support for voice, video, and various forms of data communication. In reality, most H.323 systems do not implement such a wide array of capabilities, but the logical arrangement is useful in understanding the relationships.
Amultipoint control unit(MCU) is responsible for managing multipoint conferences and is composed of two logical entities referred to as theMultipoint Controller(MC) and theMultipoint Processor(MP). In more practical terms, an MCU is a conference bridge not unlike the conference bridges used in the PSTN today. The most significant difference, however, is that H.323 MCUs might be capable of mixing or switching video, in addition to the normal audio mixing done by a traditional conference bridge. Some MCUs also provide multipoint data collaboration capabilities. What this means to the end user is that, by placing a video call into an H.323 MCU, the user might be able to see all of the other participants in the conference, not only hear their voices.
Gateways are devices that enable communication between H.323 networks and other networks, such as PSTN or ISDN networks. If one party in a conversation is utilizing a terminal that is not an H.323 terminal, then the call must pass through a gateway in order to enable both parties to communicate.
Gateways are widely used today in order to enable the legacy PSTN phones to interconnect with the large, international H.323 networks that are presently deployed by services providers. Gateways are also used within the enterprise in order to enable enterprise IP phones to communicate through the service provider to users on the PSTN.
Gateways are also used in order to enable videoconferencing devices based onH.320andH.324to communicate with H.323 systems. Most of the third generation (3G) mobile networks deployed today utilize the H.324 protocol and are able to communicate with H.323-based terminals in corporate networks through such gateway devices.
A Gatekeeper is an optional component in the H.323 network that provides a number of services to terminals, gateways, and MCU devices. Those services include endpoint registration, address resolution, admission control, user authentication, and so forth. Of the various functions performed by the gatekeeper, address resolution is the most important as it enables two endpoints to contact each other without either endpoint having to know theIP addressof the other endpoint.
Gatekeepers may be designed to operate in one of two signaling modes, namely "direct routed" and "gatekeeper routed" mode. Direct routed mode is the most efficient and most widely deployed mode. In this mode, endpoints utilize the RAS protocol in order to learn the IP address of the remote endpoint and a call is established directly with the remote device. In the gatekeeper routed mode, call signaling always passes through the gatekeeper. While the latter requires the gatekeeper to have more processing power, it also gives the gatekeeper complete control over the call and the ability to provide supplementary services on behalf of the endpoints.
H.323 endpoints use the RAS protocol to communicate with a gatekeeper. Likewise, gatekeepers use RAS to communicate with other gatekeepers.
A collection of endpoints that are registered to a single Gatekeeper in H.323 is referred to as a “zone”. This collection of devices does not necessarily have to have an associated physical topology. Rather, a zone may be entirely logical and is arbitrarily defined by thenetwork administrator.
Gatekeepers have the ability to neighbor together so that call resolution can happen between zones. Neighboring facilitates the use of dial plans such as theGlobal Dialing Scheme. Dial plans facilitate “inter-zone” dialing so that two endpoints in separate zones can still communicate with each other.
Border Elements and Peer Elements are optional entities similar to a Gatekeeper, but that do not manage endpoints directly and provide some services that are not described in the RAS protocol. The role of a border or peer element is understood via the definition of an "administrative domain".
An administrative domain is the collection of all zones that are under the control of a single person or organization, such as a service provider. Within a service provider network there may be hundreds or thousands of gateway devices, telephones, video terminals, or other H.323 network elements. The service provider might arrange devices into "zones" that enable the service provider to best manage all of the devices under its control, such as logical arrangement by city. Taken together, all of the zones within the service provider network would appear to another service provider as an "administrative domain".
The border element is a signaling entity that generally sits at the edge of the administrative domain and communicates with another administrative domain. This communication might include such things as access authorization information; call pricing information; or other important data necessary to enable communication between the two administrative domains.
Peer elements are entities within the administrative domain that, more or less, help to propagate information learned from the border elements throughout the administrative domain. Such architecture is intended to enable large-scale deployments within carrier networks and to enable services such asclearinghouses.
The diagram, figure 2, provides an illustration of an administrative domain with border elements, peer elements, and gatekeepers.
H.323 is defined as abinary protocol, which allows for efficient message processing in network elements. The syntax of the protocol is defined inASN.1and uses thePacked Encoding Rules(PER) form of message encoding for efficient message encoding on the wire. Below is an overview of the various communication flows in H.323 systems.
Once the address of the remote endpoint is resolved, the endpoint will use H.225.0 Call Signaling in order to establish communication with the remote entity. H.225.0 messages are:[9]
In the simplest form, an H.323 call may be established as follows (figure 3).
In this example, the endpoint (EP) on the left initiated communication with the gateway on the right and the gateway connected the call with the called party. In reality, call flows are often more complex than the one shown, but most calls that utilize the Fast Connect procedures defined within H.323 can be established with as few as 2 or 3 messages. Endpoints must notify their gatekeeper (if gatekeepers are used) that they are in a call.
Once a call has concluded, a device will send a Release Complete message. Endpoints are then required to notify their gatekeeper (if gatekeepers are used) that the call has ended.
Endpoints use the RAS protocol in order to communicate with a gatekeeper. Likewise, gatekeepers use RAS to communicate with peer gatekeepers. RAS is a fairly simple protocol composed of just a few messages. Namely:
When an endpoint is powered on, it will generally send a gatekeeper request (GRQ) message to "discover" gatekeepers that are willing to provide service. Gatekeepers will then respond with a gatekeeper confirm (GCF) and the endpoint will then select a gatekeeper to work with. Alternatively, it is possible that a gatekeeper has been predefined in the system’s administrative setup so there is no need for the endpoint to discover one.
Once the endpoint determines the gatekeeper to work with, it will try to register with the gatekeeper by sending a registration request (RRQ), to which the gatekeeper responds with a registration confirm (RCF). At this point, the endpoint is known to the network and can make and place calls.
When an endpoint wishes to place a call, it will send an admission request (ARQ) to the gatekeeper. The gatekeeper will then resolve the address (either locally, by consulting another gatekeeper, or by querying some other network service) and return the address of the remote endpoint in the admission confirm message (ACF). The endpoint can then place the call.
Upon receiving a call, a remote endpoint will also send an ARQ and receive an ACF in order to get permission to accept the incoming call. This is necessary, for example, to authenticate the calling device or to ensure that there is availablebandwidthfor the call.
Figure 4 depicts a high-level communication exchange between two endpoints (EP) and two gatekeepers (GK).
Once a call has initiated (but not necessarily fully connected) endpoints may initiate H.245 call control signaling in order to provide more extensive control over the conference. H.245 is a rather voluminous specification with many procedures that fully enable multipoint communication, though in practice most implementations only implement the minimum necessary in order to enablepoint-to-pointvoice and video communication.
H.245 provides capabilities such as capability negotiation,master/slavedetermination, opening and closing of "logical channels" (i.e., audio and video flows), flow control, and conference control. It has support for bothunicastandmulticastcommunication, allowing the size of a conference to theoretically grow without bound.
Of the functionality provided by H.245, capability negotiation is arguably the most important, as it enables devices to communicate without having prior knowledge of the capabilities of the remote entity. H.245 enables rich multimedia capabilities, including audio, video, text, anddata communication. For transmission of audio, video, or text, H.323 devices utilize both ITU-defined codecs and codecs defined outside the ITU. Codecs that are widely implemented by H.323 equipment include:
H.245 also enables real-time data conferencing capability through protocols likeT.120. T.120-based applications generally operate in parallel with the H.323 system, but are integrated to provide the user with a seamless multimedia experience. T.120 provides such capabilities as application sharingT.128, electronic whiteboardT.126, file transferT.127, and text chatT.134within the context of the conference.
When an H.323 device initiates communication with a remote H.323 device and when H.245 communication is established between the two entities, the Terminal Capability Set (TCS) message is the first message transmitted to the other side.
After sending a TCS message, H.323 entities (through H.245 exchanges) will attempt to determine which device is the "master" and which is the "slave." This process, referred to as Master/Slave Determination (MSD), is important, as the master in a call settles all "disputes" between the two devices. For example, if both endpoints attempt to open incompatible media flows, it is the master who takes the action to reject the incompatible flow.
Once capabilities are exchanged and master/slave determination steps have completed, devices may then open "logical channels" or media flows. This is done by simply sending an Open Logical Channel (OLC) message and receiving an acknowledgement message. Upon receipt of the acknowledgement message, an endpoint may then transmit audio or video to the remote endpoint.
A typical H.245 exchange looks similar to figure 5:
After this exchange of messages, the two endpoints (EP) in this figure would be transmitting audio in each direction. The number of message exchanges is numerous, each has an important purpose, but nonetheless takes time.
For this reason, H.323 version 2 (published in 1998) introduced a concept called Fast Connect, which enables a device to establishbi-directionalmedia flows as part of the H.225.0 call establishment procedures. With Fast Connect, it is possible to establish a call with bi-directional media flowing with no more than two messages, like in figure 3.
Fast Connect is widely supported in the industry. Even so, most devices still implement the complete H.245 exchange as shown above and perform that message exchange in parallel to other activities, so there is no noticeable delay to the calling or called party.
Voice over Internet Protocol (VoIP) describes the transmission of voice using the Internet or other packet switched networks. ITU-T Recommendation H.323 is one of the standards used in VoIP. VoIP requires a connection to the Internet or another packet switched network, a subscription to a VoIP service provider and a client (ananalogue telephone adapter(ATA), VoIP Phone or "soft phone"). The service provider offers the connection to other VoIP services or to the PSTN. Most service providers charge a monthly fee, then additional costs when calls are made.[citation needed]Using VoIP between two enterprise locations would not necessarily require a VoIP service provider, for example. H.323 has been widely deployed by companies who wish to interconnect remote locations over IP using a number of various wired and wireless technologies.
A videoconference, or videoteleconference (VTC), is a set oftelecommunicationtechnologiesallowing two or more locations to interact via two-way video and audio transmissions simultaneously. There are basically two types of videoconferencing; dedicated VTC systems have all required components packaged into a single piece of equipment while desktop VTC systems are add-ons to normalPC's, transforming them into VTC devices. Simultaneous videoconferencing among three or more remote points is possible by means of a Multipoint Control Unit (MCU). There are MCU bridges for IP and ISDN-based videoconferencing. Due to the price point and proliferation of the Internet, and broadband in particular, there has been a strong spurt of growth and use of H.323-based IP videoconferencing. H.323 is accessible to anyone with a high speed Internet connection, such asDSL. Videoconferencing is utilized in various situations, for example;distance education,telemedicine,Video Relay Service, and business.[citation needed][needs update]
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The following tables compare general and technical information for a variety ofaudio coding formats.
For listening tests comparing the perceived audio quality of audio formats and codecs, see the articleCodec listening test.
(2023-07-14)
(2022-10-26)
(2023-06-23)
(2004-02-08)
(2023-05-09)
NearLinkaudio
(2022-12-21)
(2025-01-24)
(2009-04-02)
(2023-04-24)
(2007-03-19, final release)
(2022-06-30)
(2015-02-24)
(2023-06-21)
(2020-07-04)
(2024-02-29)
[51][52]
8–576 kbit/s (stereo, 48 kHz)
48 kHz (Stereo)
330, 660, 990 kbit/s (48/96/192 kHz)
~0.6-7.5 kbps (stereo)
12-320 kbit/s (stereo)
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fNetwork emulationis a technique for testing the performance of real applications over a virtual network. This is different fromnetwork simulationwhere virtual models of traffic, network models, channels, and protocols are applied. The aim is to assess performance, predict the impact of change, or otherwise optimize technology decision-making.
Networkemulationis the act of testing the behavior of a network (5G,wireless,MANETs, etc) in a lab. Apersonal computerorvirtual machinerunssoftwareto perform the network emulation; adedicated emulation deviceis sometimes used for link emulation.
Networks introduce delay, errors, and drop packets. The primary goal of network emulation is to create an environment whereby users can connect the devices, applications, products, and/or services being tested to validate their performance, stability, or functionality against real-world network scenarios. Once tested in a controlled environment against actual network conditions, users can have confidence that the item being tested will perform as expected.
Emulation differs fromsimulationin that a network emulator appears tobea network; end-systems such ascomputerscan be attached to the emulator and will behave as if they are attached to a network. A network emulator mirrors the network which connects end-systems, not the end-systems themselves.
Network simulators are typically programs that run on a single computer, take an abstract description of the network traffic such as a flow arrival process, and yield performance statistics such as throughput, delay, loss etc.
These products are typically found in the Development and QA environments of Service Providers, Network Equipment Manufacturers, and Enterprises.
Software developers typically want to analyze the response time and sensitivity to packet loss of client-server applications and emulate specific network effects (of 5G, Smart homes, industrial IOT, military networks, etc.,) with different round-trip-times, throughputs, bit error rates, and packet drops.
Two open-source network emulators are Common Open Research Emulator (CORE) and Extendable Mobile Ad hoc Network Emulator (EMANE). They both support operation as network black boxes, i.e. external machines/devices can be hooked up to the emulated network with no knowledge of emulation. They also support both wired and wireless network emulation with various degrees of fidelity. A CORE is more useful for quick network layouts (layer 3 and above) and single-machine emulation. EMANE is better suited for distributed high-fidelity large-scale network emulation (layers 1/2).
The network performance under maximum throughput conditions can be analyzed bynetwork traffic measurementin atestbednetwork, using anetwork traffic generatorsuch asiperf. The traffic generator sends dummy packets, often with a unique packet identifier, making it possible to keep track of the packet delivery in the network using anetwork analyzer.
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Atraffic generation modelis a stochastic model of thetraffic flowsor data sources in acommunication network, for example a cellular network or a computer network. Apacket generation modelis a traffic generation model of thepacket flowsor data sources in apacket-switched network. For example, aweb trafficmodel is a model of the data that is sent or received by a user'sweb-browser. These models are useful during the development of telecommunication technologies, in view to analyse the performance and capacity of various protocols, algorithms and network topologies .
The network performance can be analyzed bynetwork traffic measurementin atestbednetwork, using anetwork traffic generatorsuch asiperf,bwpingandMausezahn. The traffic generator sends dummy packets, often with a unique packet identifier, making it possible to keep track of the packet delivery in the network.
Numerical analysis usingnetwork simulationis often a less expensive approach.
An analytical approach usingqueueing theorymay be possible for a simplified traffic model but is often too complicated if a realistic traffic model is used.
A simplified packet data model is thegreedy sourcemodel. It may be useful in analyzing themaximum throughputforbest-efforttraffic (without any quality-of-service guarantees). Many traffic generators are greedy sources.
Another simplified traditional traffic generation model for packet data, is thePoisson process, where the number of incoming packets and/or the packet lengths are modeled as anexponential distribution. When the packets interarrival time is exponential, with constant packet size it resembles an M/D/1 system. When both packet inter arrivals and sizes are exponential, it is an M/M/1 queue.
However, the Poisson traffic model is memoryless, which means that it does not reflect theburstynature of packet data, also known as thelong-range dependency. For a more realistic model, aself-similar processsuch as thePareto distributioncan be used as along-tail trafficmodel.
The actual content of the payload data is typically not modeled, but replaced by dummy packets. However, if the payload data is to be analyzed on the receiver side, for example regardingbit-error rate, aBernoulli processis often assumed, i.e. a random sequence of independent binary numbers. In this case, achannel modelreflects channel impairments such as noise, interference and distortion.
One of the3GPP2models is described in.[1]This document describes the following types of traffic flows:
The main idea is to partly implement HTTP, FTP and TCPprotocols. For example, an HTTP traffic generator simulates the download of a web-page, consisting of a number of small objects (like images). A TCP stream (that's why TCP generator is a must in this model) is used to download these objects according to HTTP1.0 or HTTP1.1 specifications. These models take into account the details of these protocols' work. The Voice, WAP and Mobile Network Gaming are modelled in a less complicated way.
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TheIP Multimedia SubsystemorIP Multimedia Core Network Subsystem(IMS) is a standardisedarchitectural frameworkfor delivering IPmultimediaservices. Historically, mobile phones have provided voice call services over acircuit-switched-style network, rather than strictly over an IPpacket-switchednetwork. Variousvoice over IPtechnologies are available on smartphones; IMS provides a standard protocol across vendors.
IMS was originally designed by the wirelessstandardsbody3rd Generation Partnership Project(3GPP), as a part of the vision for evolving mobile networks beyondGSM. Its original formulation (3GPP Rel-5) represented an approach for delivering Internet services overGPRS. This vision was later updated by 3GPP,3GPP2andETSITISPANby requiring support of networks other thanGPRS, such asWireless LAN,CDMA2000and fixed lines.
IMS usesIETFprotocols wherever possible, e.g., theSession Initiation Protocol(SIP). According to the 3GPP, IMS is not intended to standardize applications, but rather to aid the access of multimedia and voice applications from wireless and wireline terminals, i.e., to create a form offixed-mobile convergence(FMC).[1]This is done by having a horizontal control layer that isolates the access network from theservice layer. From a logical architecture perspective, services need not have their own control functions, as the control layer is a common horizontal layer. However, in implementation this does not necessarily map into greater reduced cost and complexity.
Alternative and overlapping technologies for access and provisioning of services across wired and wireless networks include combinations ofGeneric Access Network,softswitchesand "naked" SIP.
Since it is becoming increasingly easier to access content and contacts using mechanisms outside the control of traditional wireless/fixed operators, the interest of IMS is being challenged.[2]
Examples of global standards based on IMS areMMTelwhich is the basis for Voice over LTE (VoLTE),Wi-Fi Calling(VoWIFI),Video over LTE(ViLTE), SMS/MMS over WiFi and LTE,Unstructured Supplementary Service Data(USSD) over LTE, andRich Communication Services(RCS), which is also known as joyn or Advanced Messaging, and now RCS is operator's implementation. RCS also further added Presence/EAB (enhanced address book) functionality.[3]
Some operators opposed IMS because it was seen as complex and expensive.
In response, a cut-down version of IMS—enough of IMS to support voice and SMS over the LTE network—was defined and standardized in 2010 asVoice over LTE(VoLTE).[6]
Each of the functions in the diagram is explained below.
The IP multimedia core network subsystem is a collection of different functions, linked by standardized interfaces, which grouped form one IMS administrative network.[7]A function is not a node (hardware box): An implementer is free to combine two functions in one node, or to split a single function into two or more nodes. Each node can also be present multiple times in a single network, for dimensioning, load balancing or organizational issues.
The user can connect to IMS in various ways, most of which use the standard IP. IMS terminals (such asmobile phones,personal digital assistants(PDAs) and computers) can register directly on IMS, even when they areroamingin another network or country (the visited network). The only requirement is that they can use IP and run SIP user agents. Fixed access (e.g.,digital subscriber line(DSL),cable modems,Ethernet,FTTx), mobile access (e.g.5G NR,LTE,W-CDMA,CDMA2000,GSM,GPRS) and wireless access (e.g.,WLAN,WiMAX) are all supported. Other phone systems likeplain old telephone service(POTS—the old analogue telephones),H.323and non IMS-compatible systems, are supported throughgateways.
HSS – Home subscriber server:Thehome subscriber server(HSS), oruser profile server function(UPSF), is a master user database that supports the IMS network entities that actually handlecalls. It contains the subscription-related information (subscriberprofiles), performsauthenticationandauthorizationof the user, and can provide information about the subscriber's location and IP information. It is similar to the GSMhome location register(HLR) andAuthentication centre(AuC).
Asubscriber location function(SLF) is needed to map user addresses when multiple HSSs are used.
User identities:Various identities may be associated with IMS: IP multimedia private identity (IMPI), IP multimedia public identity (IMPU), globally routable user agent URI (GRUU), wildcarded public user identity. Both IMPI and IMPU are not phone numbers or other series of digits, butuniform resource identifier(URIs), that can be digits (a Tel URI, such astel:+1-555-123-4567) or alphanumeric identifiers (a SIP URI, such assip:john.doe@example.com" ).
IP Multimedia Private Identity:TheIP Multimedia Private Identity(IMPI) is a unique permanently allocated global identity assigned by the home network operator. It has the form of a Network Access Identifier(NAI) i.e. user.name@domain, and is used, for example, for Registration, Authorization, Administration, and Accounting purposes. Every IMS user shall have one IMPI.
IP Multimedia Public Identity:TheIP Multimedia Public Identity(IMPU) is used by any user for requesting communications to other users (e.g. this might be included on abusiness card). Also known as Address of Record (AOR). There can be multiple IMPU per IMPI. The IMPU can also be shared with another phone, so that both can be reached with the same identity (for example, a single phone-number for an entire family).
Globally Routable User Agent URI:Globally Routable User Agent URI(GRUU) is an identity that identifies a unique combination of IMPU andUEinstance.
There are two types of GRUU: Public-GRUU (P-GRUU) and Temporary GRUU (T-GRUU).
Wildcarded Public User Identity:Awildcarded Public User Identityexpresses a set of IMPU grouped together.
The HSS subscriber database contains the IMPU, IMPI,IMSI,MSISDN, subscriber service profiles, service triggers, and other information.
Several roles of SIP servers or proxies, collectively called Call Session Control Function (CSCF), are used to process SIP signaling packets in the IMS.
SIPApplication servers(AS) host and executeservices, and interface with the S-CSCF using SIP. An example of an application server that is being developed in 3GPP is theVoice call continuityFunction (VCC Server). Depending on the actual service, the AS can operate in SIP proxy mode, SIP UA (user agent) mode or SIPB2BUAmode. An AS can be located in the home network or in an external third-party network. If located in the home network, it can query the HSS with the Diameter Sh or Si interfaces (for a SIP-AS).
The AS-ILCM (Application Server - Incoming Leg Control Model) and AS-OLCM (Application Server - Outgoing Leg Control Model) store transaction state, and may optionally store session state depending on the specific service being executed.
The AS-ILCM interfaces to the S-CSCF (ILCM) for an incoming leg and the AS-OLCM interfaces to the S-CSCF (OLCM) for an outgoing leg.
Application Logic provides the service(s) and interacts between the AS-ILCM and AS-OLCM.
Public Service Identities (PSI) are identities that identify services, which are hosted by application servers. As user identities, PSI takes the form of either a SIP or Tel URI. PSIs are stored in the HSS either as a distinct PSI or as a wildcarded PSI:
TheMedia Resource Function(MRF) provides media related functions such asmedia manipulation(e.g. voice stream mixing) and playing of tones and announcements.
Each MRF is further divided into amedia resource function controller(MRFC) and amedia resource function processor(MRFP).
TheMedia Resource Broker(MRB) is a functional entity that is responsible for both collection of appropriate published MRF information and supplying of appropriate MRF information to consuming entities such as the AS. MRB can be used in two modes:
ABreakout Gateway Control Function(BGCF) is a SIP proxy which processes requests for routing from an S-CSCF when the S-CSCF has determined that the session cannot be routed using DNS or ENUM/DNS. It includes routing functionality based on telephone numbers.
A PSTN/CS gateway interfaces withPSTNcircuit switched(CS) networks. For signalling, CS networks useISDN User Part(ISUP) (orBICC) overMessage Transfer Part(MTP), while IMS uses SIP over IP. For media, CS networks usePulse-code modulation(PCM), while IMS usesReal-time Transport Protocol(RTP).
Media Resources are those components that operate on the media plane and are under the control of IMS core functions. Specifically,Media Server(MS) andMedia gateway(MGW)
There are two types ofnext-generation networkinginterconnection:
An NGN interconnection mode can be direct or indirect. Direct interconnection refers to the interconnection between two network domains without any intermediate network domain. Indirect interconnection at one layer refers to the interconnection between two network domains with one or more intermediate network domain(s) acting astransit networks. The intermediate network domain(s) provide(s) transit functionality to the two other network domains. Different interconnection modes may be used for carryingservice layersignalling and media traffic.
Offline charging is applied to users who pay for their services periodically (e.g., at the end of the month).Online charging, also known as credit-based charging, is used forprepaidservices, or real-time credit control of postpaid services. Both may be applied to the same session.
Charging function addressesare addresses distributed to each IMS entities and provide a common location for each entity to send charging information.charging data function(CDF) addresses are used for offline billing andOnline Charging Function(OCF) for online billing.
IMS-based PES (PSTN Emulation System) provides IP networks services to analog devices. IMS-based PES allows non-IMS devices to appear to IMS as normal SIP users. Analog terminal using standard analog interfaces can connect to IMS-based PES in two ways:
Both A-MGW and VGW are unaware of the services. They only relay call control signalling to and from the PSTN terminal. Session control and handling is done by IMS components.
Replacement for the Gq reference point.
One of the most important features of IMS, that of allowing for a SIP application to be dynamically and differentially (based on the user's profile) triggered, is implemented as a filter-and-redirect signalling mechanism in the S-CSCF.
The S-CSCF might apply filter criteria to determine the need to forward SIP requests to AS. It is important to note that services for the originating party will be applied in the originating network, while the services for the terminating party will be applied in the terminating network, all in the respective S-CSCFs.
Aninitial filter criteria(iFC) is anXML-based format used for describing control logic. iFCs represent a provisioned subscription of a user to an application. They are stored in the HSS as part of the IMS Subscription Profile and are downloaded to the S-CSCF upon user registration (for registered users) or on processing demand (for services, acting as unregistered users). iFCs are valid throughout the registration lifetime or until the User Profile is changed.[7]
The iFC is composed of:
There are two types of iFCs:
It is envisaged that security defined in TS 33.203 may not be available for a while especially because of the lack ofUSIM/ISIMinterfaces and prevalence of devices that supportIPv4. For this situation, to provide some protection against the most significant threats, 3GPP defines some security mechanisms, which are informally known as "early IMS security," in TR33.978. This mechanism relies on the authentication performed during the network attachment procedures, which binds between the user's profile and its IP address. This mechanism is also weak because the signaling is not protected on theuser–network interface.
CableLabsinPacketCable 2.0, which adopted also the IMS architecture but has no USIM/ISIM capabilities in their terminals, published deltas to the 3GPP specifications where the Digest-MD5 is a valid authentication option. Later on,TISPANalso did a similar effort given their fixed networks scopes, although the procedures are different. To compensate for the lack of IPsec capabilities, TLS has been added as an option for securing the Gm interface. Later 3GPP Releases have included the Digest-MD5 method, towards a Common-IMS platform, yet in its own and again different approach. Although all 3 variants of Digest-MD5 authentication have the same functionality and are the same from the IMS terminal's perspective, the implementations on the Cx interface between the S-CSCF and the HSS are different.
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Inintelligent networks(IN) and cellular networks,service layeris a conceptual layer within a network service provider architecture. It aims at providingmiddlewarethat serves third-partyvalue-added servicesand applications at a higherapplication layer. The service layer providescapability serversowned by a telecommunication network service provider, accessed through open and secureApplication Programming Interfaces(APIs) by application layer servers owned by third-partycontent providers. The service layer also provides an interface to core networks at a lower resource layer.[1]The lower layers may also be namedcontrol layerandtransport layer(the transport layer is also referred to as theaccess layerin some architectures).[citation needed]
The concept of service layer is used in contexts such asIntelligent networks(IN),WAP,3GandIP Multimedia Subsystem(IMS). It is defined in the3GPPOpen Services Architecture(OSA) model, which reused the idea of theParlayAPI for third-party servers.
In software design, for exampleService-oriented architecture, the concept of service layer has a different meaning.
The service layer of anIMSarchitecture provides multimedia services to the overall IMS network. This layer contains network elements which connect to the Serving-CSCF (Call Session Control Function) using the IP multimedia Subsystem Service Control Interface (ISC).[2]The ISC interface uses theSIPsignalling protocol.
The network elements contained within the service layer are generically referred to as 'service platforms' however the 3GPP specification (3GPP TS 23.228 V8.7.0) defines several types of service platforms:
The SIP Application Server (AS) performs the same function as aTelephony Application Serverin a pre-IMS network, however it is specifically tailored to support the SIP signalling protocol for use in an IMS network.
An OSA Service Capability Server acts as a secure gateway between the IMS network and an application which runs upon theOpen Services Architecture(this is typically aSIPtoParlaygateway)
The IM-SSF (IP Multimedia Service Switching Function) acts as a gateway between the IMS network and application servers using other telecommunication signalling standards such asINAPandCAMEL.
Inservice-oriented architecture(SOA), the service layer is the third layer in a five-abstraction-layer model. The model consists of Object layer, Component layer, Service layer, Process layer and Enterprise layer.[3]The service layer can be considered as a bridge between the higher and lower layers, and is characterized by a number of services that are carrying out individual business functions.
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Avalue-added service(VAS) is a populartelecommunications industry[1]term for non-core services, or, in short, all services beyond standardvoice callsandfaxtransmissions. However, it can be used in any service industry, for services available at little or no cost, topromotetheir primary business. In the telecommunications industry, on a conceptual level, value-added servicesadd valueto thestandard service offering, spurring subscribers to use their phone more and allowing the operator to drive up theiraverage revenue per user. For mobile phones, technologies likeSMS,MMSanddata accesswere historically usually considered value-added services, but in recent years SMS, MMS and data access have more and more become core services, and VAS therefore has begun to exclude those services.
Mobile VAS services can be categorized into:
A distinction may also be made between standard (peer-to-peer) content and premium-charged content. These are called mobile value-added services (MVAS), which are often simply referred to as VAS.
Value-added services are supplied either in-house by themobile network operatorthemselves or by a third-party value-added service provider, also known as a content provider such asAll Headline NewsorReuters.
Value-added service providers typically connect to the operator using protocols likeShort message peer-to-peer protocol, connecting either directly to theshort message service centreor, increasingly, to a messaginggatewaythat gives the operator better control of the content. Several other operators are approaching banking on possible revenue streams by building value-added services (VAS), which is generally available with rewards-based schemes.
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OpenBTS(Open Base Transceiver Station) is a software-basedGSMaccess point, allowing standard GSM-compatiblemobile phonesto be used asSIPendpoints inVoice over IP(VoIP) networks. OpenBTS is open-source software developed and maintained byRange Networks. The public release of OpenBTS is notable for being the firstfree-softwareimplementation of the lower three layers of the industry-standard GSMprotocol stack.
It is written inC++and released as free software under the terms of version 3 of theGNU Affero General Public License.
OpenBTS replaces the conventional GSM operatorcore networkinfrastructure from layer 3 upwards. Instead of relying on externalbase station controllersforradio resource management, OpenBTS units perform this function internally. Instead of forwarding call traffic through to an operator'smobile switching center, OpenBTS delivers calls viaSIPto a VOIP soft switch (such asFreeSWITCHoryate) orPBX(such asAsterisk). This VOIP switch or PBX software can be installed on the same computer used to run OpenBTS itself, forming a self-contained cellular network in a single computer system. Multiple OpenBTS units can also share a common VOIP switch or PBX to form larger networks[2]
The OpenBTSUm air interfaceuses asoftware-defined radiotransceiverwith no specialized GSM hardware. The original implementation used aUniversal Software Radio Peripheralfrom Ettus Research, but has since been expanded to support several digital radios in implementations ranging from full-scale base stations to embeddedfemtocells.
The project was started by Harvind Samra and David A. Burgess[3]with the aim of the project to drastically reduce the cost of GSM service provision in rural areas, the developing world, and hard to reach locations such as oil rigs.[4]The project was initially conducted through Kestrel Signal Processing, the founders' consulting firm.
On September 14, 2010, at the Fall 2010DEMO conference, the original authors launchedRange Networksas a start up company to commercialize OpenBTS-based products.[5]
In September 2013, Burgess left Range Networks and started a new venture called Legba[6]and started a close collaboration with Null Team SRL, the developers ofYate. In February 2014, Legba and Null announced the release of YateBTS, a fork of the OpenBTS project that uses Yate for its control layers and network interfaces.
A large number of experimental installations have shown that OpenBTS can run on extremely low overhead platforms. These including some CDMA handsets - making a GSM gateway to aCDMAnetwork. Computer security researcher Chris Paget reported[7]that a handheld device, such as anAndroidphone, could act as a gateway base station to which handsets can connect; the Android device then connects calls using an on-boardAsteriskserver and routes them to thePSTNviaSIPover an existing3Gnetwork.
At the 2010DEF CONconference, it was demonstrated with OpenBTS that GSM calls can be intercepted because in GSM the handset does not authenticate the base station prior to accessing the network.[8]
OpenBTS has been used by the security research community to mount attacks on cellular phone baseband processors.[9][10]Previously, investigating and conducting such attacks was considered impractical due to the high cost of traditional cellular base station equipment.
Large scale live tests of OpenBTS have been conducted in the United States in Nevada and northern California using temporary radio licenses applied for through Kestrel Signal Processing andRange Networks, Inc.
During theBurning Manfestival in August 2008, a week-long live field test was run underspecial temporary authorizationlicense.[11][12]Although this test had not been intended to be open to Burning Man attendees in general, a number of individuals in the vicinity succeeded in making out-going calls after a mis-configured Asterisk PBX installation allowed through test calls prefixed with aninternational code.[13]The test connected about 120 phone calls to 95 numbers in area codes over North America.
At the 2009 Burning Man festival, a larger test setup was run using a 3-sector system.[14]For the 2010 festival, an even larger 2-sector 3-carrier system was tested.
At the 2011 festival, the OpenBTS project set up a 3-site network withVSATgateway and worked in conjunction with theVoice over IPservices companyVoxeoto provide much of the off-site call routing.[15][16]
RELIEF is a series of disaster response exercises managed by theNaval Postgraduate SchoolinCalifornia, USA.[17]Range Networks operated OpenBTS test networks at the RELIEF exercises in November 2011[18]and February 2012.[19]
In 2010, an OpenBTS system was installed on the island ofNiueand became the first installation to be connected and tested by a telecommunication company. Niue is a very small island country with a population of about 1,700 - too small to attract mobile telecommunications providers. The cost structure of OpenBTS suited Niue, which required a mobile phone service but did not have the volume of potential customers to justify buying and supporting a conventional GSM basestation system.[20]
The success of this installation and the demonstrated demand for service helped bootstrap later commercial services. The OpenBTS installation was later decommissioned ~February 2011 by Niue Telecom, a commercial grade GSM 900 network with Edge support was instead launched few months later (3x sites in Kaimiti O2, Sekena S2/2/2 and Avatele S2/2/2) this provided full coverage around the island and around the reef, the installation included a pre-pay system, USSD, Int. SMS and new Int. Gateway.
From July 26 to July 29, 2012, the Ninja Networks team set up a "NinjaTel Van" in the Vendor[21]area of Defcon 20 (at the Rio Hotel/Casino in Las Vegas.) It used OpenBTS and served a small network of 650GSMphones with custom SIM cards.[22]
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Early research and development:
Merging the networks and creating the Internet:
Commercialization, privatization, broader access leads to the modern Internet:
Examples of Internet services:
GSM 03.40or3GPP TS 23.040is amobile telephonystandard describing the format of theTransfer Protocol Data Units(TPDU) part of theShort Message Transfer Protocol(SM-TP) used in theGSMnetworks to carryShort Messages.[1]This format is used throughout the whole transfer of the message in the GSMmobile network. In contrast, application servers use different protocols, likeShort Message Peer-to-PeerorUniversal Computer Protocol, to exchange messages between them and theShort Message service center(SMSC).
GSM 03.40 is the original name of the standard. Since 1999 has been developed by the3GPPunder the name 3GPP TS 23.040. However, the original name is often used to refer even to the 3GPP document.[citation needed]
The GSM 03.40 TPDUs are used to carry messages between the Mobile Station (MS) andMobile Switching Centre(MSC) using the Short Message Relay Protocol (SM-RP),[2]while between MSC andShort Message Service Centre(SMSC) the TPDUs are carried as a parameter of aMobile Application Part(MAP)[3]package.[4]
In emerging networks which useIP Multimedia Subsystem(IMS) Short Messages are carried in the MESSAGE command ofSession Initiation Protocol(SIP). Even in theseIP-basednetworks an option exists which (due to compatibility reasons) defines transfer of Short Messages in the GSM 03.40 format embedded in 3GPP 24.011 as Content-Type: application/vnd.3gpp.sms.[5][6]
GSM 03.40 defines six types of messages between Mobile Station (MS) and SMS Center (SC), which are distinguished by the message direction and the two least significant bits in the first octet of SM-TP message (the TP-MTI field):
SMS-SUBMIT is used to submit a short message from amobile phone(Mobile Station, MS) to ashort message service centre(SMSC, SC).
SMS-SUBMIT-REPORT is an acknowledgement to the SMS-SUBMIT; a success means that the message was stored (buffered) in the SMSC, a failure means that the message was rejected by the SMSC.
SMS-COMMAND may be used to query for a message buffered in the SMSC, to modify its parameters or to delete it.
SMS-DELIVER is used to deliver a message from SMSC to a mobile phone. The acknowledgement returned by the mobile phone may optionally contain a SMS-DELIVER-REPORT. Whenhome routingapplies, SMS-DELIVER is used to submit messages from an SMSC to another one.
SMS-STATUS-REPORT may be sent by the SMSC to inform the originating mobile phone about the final outcome of the message delivery or to reply to a SMS-COMMAND.
The fields of SM-TP messages, including their order and size, are summarized in the following table, whereMmeans a mandatory field,Oan optional field,Eis used for fields which are mandatory in negative responses (RP-ERR) and not present in positive responses (RP-ACK),xis a field present elsewhere:
The first octet of the TPDU contains various flags including the TP-MTI field described above:
By setting the TP-More-Messages-to-Send (TP-MMS) bit to 0 (reversed logic), the SMSC signals it has more messages for the recipient (often further segments of a concatenated message). The MSC usually does not close the connection to the mobile phone and does not end the MAP dialogue with the SMSC, which allows faster delivery of subsequent messages or message segments. If by coincidence the further messages vanish from the SMSC in the meantime (when they are for example deleted), the SMSC terminates the MAP dialogue with a MAP Abort message.
The TP-Loop-Prevention (TP-LP) bit is designed to prevent looping of SMS-DELIVER or SMS-STATUS-REPORT messages routed to a different address than is their destination address or generated by an application. Such message may be sent only if the original message had this flag cleared and the new message must be sent with the flag set.
By setting the TP-Status-Report-Indication (TP-SRI) bit to 1, the SMSC requests a status report to be returned to the SME.
By setting the TP-Status-Report-Request (TP-SRR) bit to 1 in a SMS-SUBMIT or SMS-COMMAND, the mobile phone requests a status report to be returned by the SMSC.
When the TP-SRQ has value of 1 in an SMS-STATUS-REPORT message, the message is the result of an SMS-COMMAND; otherwise it is a result of an SMS-SUBMIT.
When TP-UDHI has value 1, the TP-UD field starts withUser Data Header.
Setting the TP-RP bits turns on a feature which allows to send a reply for a message using the same path as the original message. If the originator and the recipient home networks differ, the reply would go through another SMSC then usually. The mobile operator must take special measures to charge such messages.
Both SM-RP and MAP used to transmit GSM 03.40 TPDU carry enough information to return acknowledgement—the information whether a request was successful or not. However, a GSM 03.40 TPDU may be included in the acknowledgement to carry even more information. The GSM 03.40 has undergone the following development:
Although these changes are ancient (version 6.1.0 occurred in July 1998), old formats of MAP are frequently seen even in today's networks.
The content of the message (its text when the message is not a binary one) is carried in the TP-UD field. Its size may be up to 160 × 7 = 140 × 8 = 1120 bits. Longer messages can be split into multiple parts and sent as aConcatenated SMS. The length of message content is given in the TP-UDL field. When the message encoding is GSM 7-bit default alphabet (depends on TP-DCS field), the TP-UDL gives length of TP-UD in 7-bit units; otherwise TP-UDL gives length of the TP-UD in octets.
When TP-UDHI is 1, the TP-UD starts withUser Data Header(UDH); in this case the first octet of the TP-UD is User Data Header Length (UDHL) octet, containing the length of the UDH in octets without UDHL itself. UDH eats room from the TP-UD field. When the message encoding is GSM 7-bit default alphabet and a UDH is present, fill bits are inserted to align start of the first character of the text after UDH with septet boundary. This behaviour was designed for older mobile phones which don't understand UDH; such mobile phones might display the UDH as a jumble of strange characters; if the first character after UDH was Carriage Return (CR), the mobile phone would rewrite the message with the rest of the message.
A GSM 03.40 message contains at most one address: destination address (TP-DA) in SMS-SUBMIT and SMS-COMMAND, originator address (TP-OA) in SMS-DELIVER and recipient address (TP-RA) in SMS-STATUS-REPORT. Other addresses are carried bylower layers.
The format of addresses in the GSM 03.40 is described in the following table:
Type of number (TON):
If a subscriber enters a telephone number with `+' sign at its start, the `+' sign will be removed and the address gets TON=1 (international number), NPI=1. The number itself must always start with a country code and must be formatted exactly according to theE.164standard.
In contrast, for numbers written without `+' sign the address gets TON=0 (unknown), NPI=1. In this case the number must adhere to the mobile operator'sdial plan, which means that international numbers must have the international prefix (00 in most countries, but 011 in the USA) before the country code and numbers for long-distance calls must start with the trunk prefix (0 in most countries, 1 in the USA) followed by a trunk code.
Numbering plan identification (NPI):
Telephone numbers should have NPI=1. Application servers may use alphanumeric addresses which have TON=5, NPI=0 combination.
The EXT bit is always 1 meaning "no extension".
U.S. number +1 555 123 4567 would be encoded as 0B 91 51 55 21 43 65 F7 (the F in upper four bits of the last octet is a filler which is used when the number length is odd).
Alphanumeric address is at first put to the GSM 7-bit default alphabet, then encoded the same way as any message text in TP-UD field (that means it is 7-bit packed) and then the address is supplied with the "number" length and TON and NPI.
For example, a fictional alphanumeric addressDesign@Homeis converted to the GSM 7-bit default alphabet which yields 11 bytes 44 65 73 69 67 6E 00 48 6F 6D 65 (hex), the 7-bit packing transforms it to 77 bits stored in 10 octets as C4 F2 3C 7D 76 03 90 EF 76 19; 77 bits is 20nibbles(14 hex) which is the value of the first octet of the address. The second octet contains TON (5) and NPI (0), which yields D0 hex. The complete address in the GSM format is 14 D0 C4 F2 3C 7D 76 03 90 EF 76 19.
The Message Reference field (TP-MR) is used in all messages on the submission side with exception of the SMS-SUBMIT-REPORT (that is in SMS-SUBMIT, SMS-COMMAND and SMS-STATUS-REPORT). It is a single-octet value which is incremented each time a new message is submitted or a new SMS-COMMAND is sent. If the message submission fails, the mobile phone should repeat the submission with the same TP-MR value and with the TP-RD bit set to 1.
A date and time used in TP-SCTS, TP-DT and in Absolute format of TP-VP is stored in 7 octets:
In all octets the values are stored in binary coded decimal format with switched digits (number 35 is stored as 53 hex).
Time zone is given in quarters of an hour. If the time zone offset is negative (in Western hemisphere) bit 3 of the last octet is set to 1.
23:01:56 Mar 25th 2013 PST (GMT-7) would be encoded as 31 30 52 32 10 65 8A.
In this example, the time zone, 8A is binary 1000 1010. Bit 3 is 1, therefore the time zone is negative. The remaining number (bit-wise 'and' with 1111 0111) is 1000 0010, hexadecimal 82. Treat this as any previous element in the sequence, (hex 82 represents number 28). Finally the time zone offset is given by 28 × 15 minutes = 420 minutes (7 hours).
An SMS-SUBMIT TPDU may contain a TP-VP parameter which limits the time period for which the SMSC would attempt to deliver the message. However, the validity period is usually limited globally by the SMSC configuration parameter— often to 48 or 72 hours. The Validity Period format is defined by the Validity Period Format field:
The absolute format is identical to the othertime formatsin GSM 03.40.
Enhanced format of TP-VP field is seldom used. It has always 7 octets, although some of them are not used. The first octet is TP-VP Functionality Indicator. Its 3 least significant bits have the following meaning:
The value of 1 in the bit 6 of the first octet means that the message is Single-shot. The value of 1 in the bit 7 of the first octet indicates that TP-VP functionality indicator extends to another octet. However, no such extensions are defined.
TP-PID (Protocol identifier) either refers to the higher layer protocol being used, indicates interworking with a certain type of telematic device (likefax,telex,pager,teletex,e-mail), specifies replace type of the message or allows download of configuration parameters to theSIM card. Plain MO-MT messages have PID=0.
For TP-PID = 63 the SC converts the SM from the received TPData Coding Schemeto any data coding scheme supported by that MS (e.g. the default).
Short Message Type 0 is known as asilent SMS. Any handset must be able to receive such short message irrespective of whether there is memory available in the (U)SIM or ME or not, must acknowledge receipt of the message, but must not indicate its receipt to the user and must discard its contents, so the message will not be stored in the (U)SIM or ME.
A special 7-bit encoding calledGSM 7 bit default alphabetwas designed for Short Message System in GSM. The alphabet contains the most-often used symbols from most Western-European languages (and some Greek uppercase letters). SomeASCIIcharacters and theEuro signdid not fit into the GSM 7-bit default alphabet and must be encoded using two septets. These characters form GSM 7-bit default alphabetextension table. Support of the GSM 7-bit alphabet is mandatory for GSM handsets and network elements.[7]
Languages which useLatin script, but use characters which are not present in the GSM 7-bit default alphabet, often replace missing characters withdiacriticmarks with corresponding characters without diacritics, which causes a not entirely satisfactory user experience, but is often accepted. For best look the 16-bitUTF-16(in GSM called UCS-2) encoding may be used at price of reducing length of a (non segmented) message from 160 to 70 characters.
The messages in Chinese, Korean or Japanese languages must be encoded using theUTF-16character encoding. The same was also true for other languages using non-Latin scripts like Russian, Arabic, Hebrew and various Indian languages. In 3GPP TS 23.038 8.0.0 published in 2008 a new feature, an extendedNational language shift tablewas introduced, which in the version 11.0.0 published in 2012 coversTurkish,Spanish,Portuguese,Bengali,Gujarati,Hindi,Kannada,Malayalam,Oriya,Punjabi,Tamil,TeluguandUrdulanguages. The mechanism replaces GSM 7-bit default alphabet code table and/or extended table with a national table(s) according to special information elements inUser Data Header. The non-segmented message using national language shift table(s) may carry up to 155 (or 153) 7-bit characters.
TheData Coding Scheme(TP-DCS) field contains primarily information about message encoding. GSM recognizes only 2 encodings fortext messagesand 1 encoding forbinary messages:
The TP-DCS octet has a complex syntax to allow carrying of other information; the most notable are message classes:
Flash messagesare received by a mobile phone even though it has full memory. They are not stored in the phone, they just displayed on the phone display.
Another feature available through TP-DCS is Automatic Deletion: after reading the message is deleted from the phone.
Message Waiting Indication group of DCS values can set or reset flags of indicating presence of unreadvoicemail,fax,e-mailor other messages.
A special DCS values also allows messagecompression, but it perhaps is not used by any operator.
The values of TP-DCS are defined inGSM recommendation 03.38. Messages sent via this encoding can be encoded in the default GSM 7-bitalphabet, the 8-bit data alphabet, and the 16-bitUCS-2alphabet.[7]
The TP-DT field indicates the time and date associated with a particular TP-ST outcome:
The TP-PI field indicates presence of further fields in the SUBMIT-REPORT, DELIVER-REPORT or SMS-STATUS-REPORT TPDU.
As currently there are still four free bits in TP-PI, it can be expected that the extension bit will be zero even in the future, which helps to distinguish TP-PI field from TP-FCS field when information whether TPDU is part of positive or negative response is not available: if the most significant bit of the second octet of TPDU is 1, the second octet is TP-FCS (in a negative response), otherwise it is TP-PI (in a positive response).
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Thebase station subsystem(BSS) is the section of a traditionalcellular telephone networkwhich is responsible for handling traffic and signaling between amobile phoneand the network switching subsystem. The BSS carries outtranscodingof speech channels, allocation of radio channels to mobile phones,paging,transmissionandreceptionover theair interfaceand many other tasks related to the radio network.
Thebase transceiver station, or BTS, contains the equipment for transmitting and receiving radio signals (transceivers),antennas, and equipment forencryptingand decrypting communications with thebase station controller(BSC). Typically a BTS for anything other than apicocellwill have several transceivers (TRXs) which allow it to serve several differentfrequenciesand different sectors of the cell (in the case of sectorised base stations).
A BTS is controlled by a parent BSC via the "base station control function" (BCF). The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations. The BCF provides an operations and maintenance (O&M) connection to the network management system (NMS), and manages operational states of each TRX, as well as software handling and alarm collection.
The functions of a BTS vary depending on the cellular technology used and the cellular telephone provider. There are vendors in which the BTS is a plain transceiver which receives information from the MS (mobile station) through theUm air interfaceand then converts it to a TDM (PCM) based interface, the Abis interface, and sends it towards the BSC. There are vendors which build their BTSs so the information is preprocessed, target cell lists are generated and even intracell handover (HO) can be fully handled. The advantage in this case is less load on the expensive Abis interface.
The BTSs are equipped with radios that are able to modulate layer 1 of interface Um; for GSM 2G+ the modulation type isGaussian minimum-shift keying(GMSK), while forEDGE-enabled networks it is GMSK and8-PSK. This modulation is a kind of continuous-phasefrequency-shift keying. In GMSK, the signal to be modulated onto the carrier is first smoothed with aGaussianlow-pass filterprior to being fed to afrequency modulator, which greatly reduces the interference to neighboring channels (adjacent-channel interference).
Antenna combiners are implemented to use the same antenna for several TRXs (carriers), the more TRXs are combined the greater the combiner loss will be. Up to 8:1 combiners are found in micro and pico cells only.
Frequency hoppingis often used to increase overall BTS performance; this involves the rapid switching of voice traffic between TRXs in a sector. A hopping sequence is followed by the TRXs and handsets using the sector. Several hopping sequences are available, and the sequence in use for a particular cell is continually broadcast by that cell so that it is known to the handsets.
A TRX transmits and receives according to theGSMstandards, which specify eightTDMAtimeslots per radio frequency. A TRX may lose some of this capacity as some information is required to bebroadcastto handsets in the area that the BTS serves. This information allows the handsets to identify the network and gain access to it. This signalling makes use of a channel known as theBroadcast Control Channel(BCCH).
By using directional antennas on a base station, each pointing in different directions, it is possible to sectorise the base station so that several different cells are served from the same location. Typically thesedirectional antennashave a beamwidth of 65 to 85 degrees. This increases the traffic capacity of the base station (each frequency can carry eight voice channels) whilst not greatly increasing theinterferencecaused to neighboring cells (in any given direction, only a small number of frequencies are being broadcast). Typically two antennas are used per sector, at spacing of ten or morewavelengthsapart. This allows the operator to overcome the effects offadingdue to physical phenomena such asmultipath reception. Someamplificationof the received signal as it leaves the antenna is often used to preserve the balance between uplink and downlink signal.[1]
The base station controller (BSC) provides, classically, theintelligencebehind the BTSs. Typically a BSC has tens or even hundreds of BTSs under its control. The BSC handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers from BTS to BTS (except in the case of an inter-BSC handover in which case control is in part the responsibility of theanchor MSC). A key function of the BSC is to act as aconcentratorwhere many different low capacity connections to BTSs (with relatively low utilisation) become reduced to a smaller number of connections towards themobile switching center(MSC) (with a high level of utilisation). Overall, this means that networks are often structured to have many BSCs distributed into regions near their BTSs which are then connected to large centralised MSC sites.
The BSC is undoubtedly the most robust element in the BSS as it is not only a BTS controller but, for some vendors, a full switching center, as well as anSS7node with connections to the MSC andserving GPRS support node(SGSN) (when usingGPRS). It also provides all the required data to the operation support subsystem (OSS) as well as to the performance measuring centers.
A BSC is often based on a distributed computing architecture, with redundancy applied to critical functional units to ensure availability in the event of fault conditions. Redundancy often extends beyond the BSC equipment itself and is commonly used in the power supplies and in the transmission equipment providing the A-ter interface to PCU.
The databases for all the sites, including information such ascarrier frequencies, frequency hopping lists, power reduction levels, receiving levels for cell border calculation, are stored in the BSC. This data is obtained directly from radio planning engineering which involves modelling of thesignal propagationas well as traffic projections.
The transcoder is responsible fortranscodingthe voice channel coding between the coding used in the mobile network, and the coding used by the world's terrestrial circuit-switched network, thePublic Switched Telephone Network. Specifically, GSM uses aregular pulse excited-long term prediction(RPE-LTP) coder for voice data between the mobile device and the BSS, butpulse-code modulation(A-laworμ-lawstandardized inITU G.711) upstream of the BSS. RPE-LPC coding results in a data rate for voice of 13 kbit/s where standard PCM coding results in 64 kbit/s. Because of this change in data ratefor the same voice call, the transcoder also has a buffering function so that PCM 8-bit words can be recoded to construct GSM 20 ms traffic blocks.
Although transcoding (compressing/decompressing) functionality is defined as a base station function by the relevant standards, there are several vendors which have implemented the solution outside of the BSC. Some vendors have implemented it in a stand-alone rack using a proprietary interface. InSiemens' andNokia's architecture, the transcoder is an identifiable separate sub-system which will normally be co-located with the MSC. In some ofEricsson's systems it is integrated to the MSC rather than the BSC. The reason for these designs is that if the compression of voice channels is done at the site of the MSC, the number of fixed transmission links between the BSS and MSC can be reduced, decreasing network infrastructure costs.
This subsystem is also referred to as thetranscoder and rate adaptation unit(TRAU). Some networks use 32 kbit/sADPCMon the terrestrial side of the network instead of 64 kbit/sPCMand the TRAU converts accordingly. When the traffic is not voice but data such as fax or email, the TRAU enables its rate adaptation unit function to give compatibility between the BSS and MSC data rates.
The packet control unit (PCU) is a late addition to the GSM standard. It performs some of the processing tasks of the BSC, but for packet data. The allocation of channels between voice and data is controlled by the base station, but once a channel is allocated to the PCU, the PCU takes full control over that channel.
The PCU can be built into the base station, built into the BSC or even, in some proposed architectures, it can be at the SGSN site. In most of the cases, the PCU is a separate node communicating extensively with the BSC on the radio side and the SGSN on the Gb side.
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TheCOMP128algorithms are implementations of the A3 and A8 functions defined in theGSMstandard. A3 is used toauthenticatethe mobile station to the network. A8 is used to generate thesession keyused by A5 to encrypt the data transmitted between the mobile station and theBTS.
There are three versions of COMP128. They were originally confidential. A partial description of the first version was leaked in 1997 and completed viareverse engineering. This led to a full publication in 1998.[1]The second and third versions were obtained via reverse engineering of software which verifies SIM cards compliance.[2]
For details on the way A3 and A8 are used seeAuthentication Center.
A3 and A8 both take a 128-bit key (Ki) and a 128-bitchallenge(RAND) as inputs. A3 produces a 32-bit response (SRES) and A8 produces a 64-bit session key (Kc). A3/A8 is the combined function withKiandRANDas inputs andSRESandKcas outputs.
As A3 and A8 are not further specified, operators can freely choose the concrete algorithms used for A3 and A8.
The COMP128 algorithms implement the A3/A8 function. There are three of them:
All of them are built around acompression functionwith two 128 bits inputs and one 128 bits output, hence their names.KiandRANDare used as the inputs of the compression function. Bits from its output are then used to fillSRESandKc.
COMP128-1 uses a compression function with eight rounds which is based on a butterfly structure with five stages.SRESis filled with the first 32 bits of the output.Kcis filled with the last 54 bits of the output followed by ten zeroes.
For a full description of the algorithm, the reader can view theOsmocomBB implementation.
The implementation of COMP128-2 and COMP128-3 is noticeably more complex than COMP128-1. For a full description of the algorithm, the reader can view theOsmocomBB implementationorFreeRADIUS implementation, both based on thePython codefrom the Secrets of Sim[2]article. COMP128-2 is identical to COMP128-3 except for the fact that at the end, it clears the 10 rightmost bits ofKc.
The COMP128-1 hash function is considered weak because there is insufficientdiffusionof small changes in the input. Practical attacks have been demonstrated that can recover the subscriber key from the SIM.[3]
The session keys produced by COMP128-1 and COMP128-2 intentionally have only 54 bits of entropy. This significantly weakens the A5 or A6 encryption.
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Awalkie-talkie, more formally known as ahandheld transceiver,HT, orhandheld radio, is a hand-held, portable,two-way radiotransceiver. Its development during theSecond World Warhas been variously credited toDonald Hings, radio engineerAlfred J. Gross,Henryk Magnuskiand engineering teams atMotorola. First used for infantry, similar designs were created for field artillery and tank units, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work.[1]
Typical walkie-talkies resemble atelephonehandset, with aspeakerbuilt into one end and amicrophonein the other (in some devices the speaker also is used as the microphone) and anantennamounted on the top of the unit. They are held up to the face to talk. A walkie-talkie is ahalf-duplexcommunication device. Multiple walkie-talkies use a single radio channel, and only one radio on the channel can transmit at a time, although any number can listen. The transceiver is normally in receive mode; when the user wants to talk they must press a "push-to-talk" (PTT) button that turns off the receiver and turns on the transmitter. Some units have additional features such as sending calls, call reception with vibration alarm, keypad locking, and a stopwatch.[2][3]Smaller walkie-talkies are also very popular among young children.
In accordance withITU Radio Regulations, article 1.73, a walkie-talkie is classified asradio station/land mobile station.
Handheld two-way radios were developed by the military from backpack radios carried by a soldier in an infantry squad to keep the squad in contact with their commanders. The Canadian inventorDonald Hingswas the first to create a portable radio signaling system for his employerCM&Sin 1937. He called the system a "packset", although it later became known as a "walkie-talkie". In 2001, Hings received theOrder of Canadafor the device's significance to the war effort.[4][5]Hings' model C-58 "Handie-Talkie" was in military service by 1942, the result of a secret R&D effort that began in 1940.[6]
Alfred J. Gross, a radio engineer and one of the developers of theJoan-Eleanor system, also worked on the early technology behind the walkie-talkie between 1938 and 1941, and is sometimes credited with inventing it.[7]
The first device to be widely nicknamed a "walkie-talkie" was developed by the US military during World War II, the backpackedMotorolaSCR-300. It was created by an engineering team in 1940 at the Galvin Manufacturing Company (forerunner of Motorola). The team consisted of Marion Bond, Lloyd Morris, Bill Vogel,Dan Noble, who conceived of the design usingfrequency modulation, andHenryk Magnuski, who was the principalRF engineer.[8]
The first handheld walkie-talkie was the AMSCR-536transceiver from 1941, also made by Motorola, named the Handie-Talkie (HT).[9]The terms are often confused today, but the original walkie-talkie referred to the back mounted model, while the handie-talkie was the device which could be held entirely in the hand. Both devices usedvacuum tubesand were powered by high voltagedry cellbatteries.
Following World War II,Raytheondeveloped the SCR-536's military replacement, theAN/PRC-6. The AN/PRC-6 circuit used 13vacuum tubes(receiver and transmitter); a second set of thirteen tubes was supplied with the unit as running spares. The unit was factory set with onecrystalwhich could be changed to a different frequency in the field by replacing the crystal and re-tuning the unit. It used a 24-inchwhip antenna. There was an optional handset that could be connected to the AN/PRC-6 by a 5-foot cable. An adjustable strap was provided for carrying and support while operating.[10]
In the mid-1970s, theUnited States Marine Corpsinitiated an effort to develop asquadradio to replace the unsatisfactory helmet-mounted AN/PRR-9 receiver and receiver/transmitter handheld AN/PRT-4 (both developed by theUS Army). The AN/PRC-68, first produced in 1976 byMagnavox, was issued to the Marines in the 1980s, and was adopted by the US Army as well.
The abbreviation HT, derived from Motorola's "Handie-Talkie" trademark, is commonly used to refer to portable handheldhamradios,[11]with "walkie-talkie" often used as a layman's term or specifically to refer to a toy. Public safety and commercial users generally refer to their handhelds simply as "radios". Surplus Motorola Handie-Talkies found their way into the hands of ham radio operators immediately following World War II. Motorola's public safety radios of the 1950s and 1960s were loaned or donated to ham groups as part of theCivil Defenseprogram. To avoid trademark infringement, other manufacturers use designations such as "Handheld Transceiver" or "Handie Transceiver" for their products.
Walkie-talkies are widely used in any setting where portable radio communications are necessary, including business,public safety, military, outdoor recreation, and the like, and devices are available at numerous price points from inexpensive analog units sold as toys up to ruggedized (i.e.waterprooforintrinsically safe) analog and digital units for use on boats or in heavy industry. Most countries allow the sale of walkie-talkies for, at least, business,marine communications, and some limited personal uses such asCB radio, as well as for amateur radio designs.
Walkie-talkies for public safety, and commercial and industrial uses may be part oftrunked radio systems, which dynamically allocate radio channels for more efficient use of the limited radio spectrum. Such systems always work with abase stationthat acts as a repeater and controller, although individual handsets and mobiles may have a mode that bypasses the base station.
Walkie-talkies, thanks to increasing use of miniaturized electronics, can be made very small, with some personal two-way UHF radio models being smaller than a deck of cards (though VHF and HF units can be substantially larger due to the need for larger antennas and battery packs). In addition, as costs come down, it is possible to add advancedsquelchcapabilities such asCTCSS(analog squelch) andDCS(digital squelch) (often marketed as "privacy codes") to inexpensive radios, as well as voice scrambling and trunking capabilities. Some units (especially amateur HTs) also includeDTMFkeypads for remote operation of various devices such asrepeaters. Some models includeVOXcapability for hands-free operation, as well as the ability to attach external microphones and speakers.
Consumer and commercial equipment differ in a number of ways; commercial gear is generally ruggedized, with metal cases, and often has only a few specific frequencies programmed into it (often, though not always, with a computer or other outside programming device; older units can simply swap crystals), since a given business or public safety agent must often abide by a specific frequency allocation. Consumer gear, on the other hand, is generally made to be small, lightweight, and capable of accessing any channel within the specified band, not just a subset of assigned channels.
Military organizations use handheld radios for a variety of purposes. Modern units such as theAN/PRC-148Multiband Inter/Intra Team Radio (MBITR) can communicate on a variety of bands and modulation schemes and includeencryptioncapabilities.
Walkie-talkies (also known as HTs or "handheld transceivers") are widely used amongamateur radiooperators. While converted commercial gear by companies such as Motorola are not uncommon, many companies such asYaesu,Icom, andKenwooddesign models specifically for amateur use. While superficially similar to commercial and personal units (including such things as CTCSS and DCS squelch functions, used primarily to activate amateur radiorepeaters), amateur gear usually has a number of features that are not common to other gear, including:
Digital voice modesare available on some amateur HTs. For example, newer additions to the Amateur Radio service are Next Generation Digital Narrowband (NXDN) and Digital Smart Technology for Amateur Radio orD-STAR. Handheld radios with these technologies have several advanced features, including narrower bandwidth, simultaneous voice and messaging, GPS position reporting, and callsign routed radio calls over a wide-ranging international network.
As mentioned, commercial walkie-talkies can sometimes be reprogrammed to operate on amateur frequencies. Amateur radio operators may do this for cost reasons or due to the fact that Public Safety grade commercial gear is more solidly constructed and better designed than purpose-built amateur gear that is built to a price.
The personal walkie-talkie has become popular also because of licence-free services (such as the U.S.FRS, Europe'sPMR446and Australia'sUHF CB) in other countries. While FRS walkie-talkies are also sometimes used as toys because mass-production makes them low in cost, they have propersuperheterodynereceivers and are a useful communication tool for both business and personal use. The boom in licence-free transceivers has, however, been a source of frustration to users of licensed services which are sometimes interfered with. For example, FRS andGMRSoverlap in the United States, resulting in substantialpirateuse of the GMRS frequencies. Use of the GMRS frequencies (USA) requires a license; however most users either disregard this requirement or are unaware. Canada reallocated frequencies for licence-free use due to heavy interference from US GMRS users. The European PMR446 channels fall in the middle of a United States UHF amateur allocation, and the US FRS channels interfere with public safety communications in the United Kingdom. Designs for personal walkie-talkies are in any case tightly regulated, generally requiring non-removable antennas (with a few exceptions such asCB radioand the United StatesMURS allocation) and forbidding modified radios.
Most personal walkie-talkies sold are designed to operate inUHFallocations, and are designed to be very compact, with buttons for changing channels and other settings on the face of the radio and a short, fixed antenna. Most such units are made of heavy, often brightly colored plastic, though some more expensive units have ruggedized metal or plastic cases. Commercial-grade radios are often designed to be used on allocations such as GMRS or MURS (the latter of which has had very little readily available purpose-built equipment). In addition, CB walkie-talkies are available, but less popular due to the propagation characteristics of the 27 MHz band and the general bulkiness of the gear involved.
Personal walkie-talkies are generally designed to give easy access to all available channels (and, if supplied,squelch codes) within the device's specified allocation.
Personal two-way radios are also sometimes combined with other electronic devices;Garmin's Rino series combine aGPS receiverin the same package as an FRS/GMRS walkie-talkie (allowing Rino users to transmit digital location data to each other) Some personal radios also include receivers for AM and FM broadcast radio and, where applicable,NOAA Weather Radioand similar systems broadcasting on the same frequencies. Some designs also allow the sending of text messages and pictures between similarly equipped units.
While jobsite and government radios are often rated in power output, consumer radios are frequently and controversially rated in mile or kilometer ratings. Because of theline of sightpropagation of UHF signals, experienced users consider such ratings to be wildly exaggerated, and some manufacturers have begun printing range ratings on the package based on terrain as opposed to simple power output.
While the bulk of personal walkie-talkie traffic is in the 27 MHz and 400–500 MHz area of the UHF spectrum, there are some units that use the "Part 15" 49 MHz band (shared with cordless phones, baby monitors, and similar devices) as well as the "Part 15" 900 MHz band; in the US at least, units in these bands do not require licenses as long as they adhere to FCC Part 15 power output rules. A company calledTriSquareis, as of July 2007, marketing a series of walkie-talkies in the United States, based onfrequency-hopping spread spectrumtechnology operating in this frequency range under the nameeXRS(eXtreme Radio Service—despite the name, a proprietary design, not an official allocation of the US FCC). The spread-spectrum scheme used in eXRS radios allows up to 10 billion virtual "channels" and ensures private communications between two or more units.
Low-power versions, exempt from licence requirements, are also popular children'stoyssuch as the Fisher Price Walkie-Talkie for children illustrated in the top image on the right. Prior to the change ofCBradio fromlicensedto "permitted by part" (FCC rules Part 95) status, the typical toy walkie-talkie available inNorth Americawas limited to 100 milliwatts of power on transmit and using one or two crystal-controlled channels in the 27MHzcitizens' bandusingamplitude modulation(AM) only. Later toy walkie-talkies operated in the 49 MHz band, some withfrequency modulation(FM), shared with cordless phones and baby monitors. The lowest cost devices are very simple electronically (single-frequency,crystal-controlled, generally based on a simple discretetransistorcircuit where "grown-up" walkie-talkies usechips), may employsuperregenerativereceivers, and may lack even a volume control, but they may nevertheless be elaborately decorated, often superficially resembling more "grown-up" radios such as FRS or public safety gear. Unlike more costly units, low-cost toy walkie-talkies may not have separate microphones and speakers; the receiver's speaker sometimes doubles as a microphone while in transmit mode.
An unusual feature, common on children's walkie-talkies but seldom available otherwise even on amateur models, is a "code key", that is, a button allowing the operator to transmitMorse codeor similar tones to another walkie-talkie operating on the same frequency. Generally the operator depresses the PTT button and taps out a message using a Morse Codecrib sheetattached as a sticker to the radio. However, as Morse Code has fallen out of wide use outside amateur radio circles, some such units either have a grossly simplified code label or no longer provide a sticker at all.
In addition,Family Radio ServiceUHFradios will sometimes be bought and used as toys, though they are not generally explicitly marketed as such (but seeHasbro'sChatNowline, which transmits both voice and digital data on the FRS band).
Somecellular telephone networksoffer a push-to-talk handset that allows walkie-talkie-like operation over the cellular network, without dialing a call each time. However, the cellphone provider must be accessible.
In addition to land mobile use, waterproof walkie talkie designs are also used formarine VHFandaviationcommunications, especially on smaller boats andultralight aircraftwhere mounting a fixed radio might be impractical or expensive. Often such units will have switches to provide quick access to emergency and information channels. They are also used in recreational UTVs to coordinate logistics, keep riders out of the dust and are usually connected to an intercom and headsets
Intrinsically safewalkie-talkies are often required in heavy industrial settings where the radio may be used around flammable vapors. This designation means that the knobs and switches in the radio are engineered to avoid producing sparks as they are operated.
A variety ofmobile appsexist that mimic a walkie-talkie/push-to-talkstyle interaction. They are marketed as low-latency, asynchronous communication. The advantages touted over two-way voice calls include: the asynchronous nature not requiring full user interaction (likeSMS) and it is voice over IP (VOIP) so it does not use minutes on a cellular plan.
Applications on the market that offer this walkie-talkie style interaction for audio includeHytera,[14]Voxer,Zello,Orion Labs,Motorola Wave, and HeyTell, among others.[15]
Other smartphone-based walkie-talkie products are made by companies likegoTenna,Fantom Dynamicsand BearTooth, and offer a radio interface.[citation needed]Unlike mobile data dependent applications, these products work by pairing to an app on the user's smartphone and working over a radio interface.[16]
There are various types of accessories available for walkie-talkies such as rechargeable batteries, drop-in rechargers, multi-unit rechargers for charging as many as six units at a time, and an audio accessory jack that can be used for headsets or speaker microphones. Newer models allow the connection to wireless headsets viaBluetooth. Some models also came up with the wifi integration such asMotorolaXIRP 8600i series.[17]
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Anamateur radio stationis aradio stationdesigned to provideradiocommunicationsin theamateur radio servicefor anamateur radio operator. Radio amateurs build and operate several types of amateur radio stations, including fixed ground stations, mobile stations, space stations, and temporary field stations. Aslangterm often used for an amateur station's location is theshack, named after the small enclosures added to the upperworks of naval ships to hold early radio equipment and batteries.[1][2]
An amateur radio station established in a permanent structure with equipment that is not intended for portable operation is referred to as afixed station. This is the most common form of amateur radio station, and can be found in homes, schools, and some public buildings. A typical fixed station is equipped with atransceiverand one or moreantennas. For voice communications, the station will be equipped with amicrophone; for communications usingMorse code, atelegraph keyis common; and for communications over digital modes such asRTTYandPSK31, a station will be equipped with a specialized interface to connect the transceiver to acomputersound card. While not a requirement for radiocommunications, most fixed amateur radio stations are equipped with one or morecomputers, which serve tasks ranging from logging of contacts with other stations to various levels of station hardware control. Fixed stations might also be equipped withamplifiers,antenna rotators,SWR meters,antenna tuners, and other station accessories.
Fixed stations are generally powered from theACmains electrical supply available in the building. Some equipment in fixed stations may run off low voltageDCinstead of AC, and require a separatepower supply. Some fixed stations are equipped with auxiliary sources of power, such aselectrical generatorsorbatteriesfor use in emergencies.
An amateur radio station installed in avehicleis referred to as amobile station. A typical mobile station is equipped with a transceiver, one or more antennas, and a microphone. The transceiver may be specially designed for installation in vehicles. It may be much smaller than transceivers designed for fixed station use, to facilitate installation under a seat or in a trunk, and it may feature a detachable control head that can be mounted in a separate location from the rest of the radio. Antennas designed for mobile stations must accommodate the unique physical constraints of the vehicle and travel lanes which it occupies, allowing for clearance under overpasses and bridges, and safe passage by vehicles in adjacent lanes. Most antennas used in mobile stations areomnidirectional. Few mobile stations are equipped to communicate with Morse code or digital modes. Most mobile stations are designed to be operated by the vehicle operator while driving.
Most transceivers installed in vehicles are designed to run on 12-16 VDC, and are generally powered by the startingbatteryin the vehicle. Because of the power demands placed on the vehicle battery, most mobile stations either do not include external amplifiers or include amplifiers with power outputs that are more modest than those commonly found in fixed stations.
A specialized form of mobile station used for competition in aVHFamateur radiocontestinNorth Americais called arover station. A rover station is often designed to be operated by a passenger in the vehicle rather than the driver, and may include multiple transceivers,transverters,directional antennas, and alaptop computerto log contacts made.
While it may not be a regulatory requirement, many mobile stations will append a/Mto end of their call sign (pronounced as "slash mobile" onphone) while operating to identify themselves to other stations as a mobile station. Rover station operating in a VHF contest will append a/Rto the end of their call sign (pronounced "slash rover").
Maritime mobilestations are mobile stations installed in a watercraft, usually an ocean-going vessel. When in international waters, these stations are operated under the regulatory authority of theflagunder which the vessel is registered. In addition to the regulatory requirements of amateur radio, operation of maritime mobile stations also requires the permission of the captain of the vessel. Maritime mobile stations append a/MMto end of their call sign (pronounced as "slash maritime mobile").
Aeronautical mobilestations are mobile stations installed in an aircraft. In addition to the regulatory requirements of amateur radio, operation of aeronautical mobile stations also requires the permission of the pilot of the aircraft. Aeronautical mobile stations append a/AMto end of their call sign (pronounced as "slash aeronautical mobile").
An amateur radio station set up in a temporary location is referred to as aportable station. A portable station might be established to provideemergency communicationsin a disaster area, to provide public service communications during a large organized event such as a charity bicycle ride, to provide communications during an expedition, or for the recreational enjoyment of operating outdoors. Portable stations include the same basic equipment as fixed and mobile stations, although transportation of the transceiver, antennas, power supplies or batteries and necessary accessories often influences the particular selection. Equipment that does not weigh very much, or that can be broken down for shipment or transportation in luggage is especially popular with amateur radio operators travelling onDX-peditions.
Most portable stations rely upon generator or battery power. Because this form of power might be of limited supply, portable stations often operate at lowertransmitter power outputto conserve energy.
Some portable stations append a/Pto end of their call sign (pronounced as "slash portable") to indicate their status as a portable operation. In some countries, this is a regulatory requirement, whereas in others it is done at the option of the operator.
An amateur radio station that is located in asatellite, theSpace Shuttle, or on theInternational Space Stationis referred to as aspace station. Some countries, including theUnited States, have additional or different regulations regarding the operation of space stations than other amateur radio stations. Most space stations are located on satellites that orbit the Earth. These stations are frequently eithertranspondersorrepeatersthat operate under automatic control and can be used byground stations(any station that is not a space station) to relay their signal to other ground stations.
Handheld radios contain all the necessary equipment for radiocommunications with another station. A typical radio used as ahandheld stationintegrates a transceiver with an antenna and a battery in one handheld package. Most handheld transceivers used in amateur radio are designed for operation on the VHF orUHFamateur radio bands and most often are capable of onlyFMvoice communications transmissions. To conserve battery power, they have limited transmitter power, often below 1W, to cover a local range of typically a few km or miles.
Anamateur radio repeateris a specialty amateur radio station that extends the range of communications for other stations. A repeater uses a receiver tuned to one radio frequency and a transmitter tuned to another radio frequency. Other stations using a repeater station transmit on one frequency but listen for signals on the other frequency. If a repeater station is in a favorable location, such as on a tall tower, the top of a tall building, or on a mountaintop, stations that otherwise would not be able to communicate with each other can each use the repeater and establish two-way communications.
Repeater stations generally operate under automatic control. The control equipment is responsible for transmitting the repeater station's call sign at regular intervals. This identification is often done in Morse code. Some US repeater stations append a/Rto end of their call sign or not (used to be required in the 80s and early 90s but no longer). Some may still have a vanity "WR#xxx" repeater license where #=0 thru 9 and xxx is any 3 letter combo but these callsigns won't be renewed and will be forced to change when their current license expires.
Some modern amateurtransceivershaveembedded computerswithfirmwarewhich is executed to provide the functions and features of the transceiver. This software must be provided by the original manufacturer of the equipment. Another type of software is that required to control a receiver (or transceiver) without a front panel provided. Examples of this are the Kenwood TS-B2000 and the Ten-Tec Pegasus; both transceivers are sold with PC software to provide thehuman interfacefor operation. Most transceivers with front control panels (and many receivers popular among shortwave listeners) have a computer interface such as a serial port,USBorEthernetport. These ports are useful for satellite-tracking frequency control (Dopplertuning), station logging, digital operation, internet and special-needs accessibility. In many cases, the software adds improved or extra functions and features beyond that provided by the original design. For this reason, some operators purchase radio-control software for non-computerized operation even if their radio has a front control panel.[3]
During transmissions, an amateur radio station must identify itself with acall signissued by the authorized regulatory authority of thecountryin which the station is located.
Most regulatory agencies worldwide issue amateur radio call signs to the operator licensee, and not to the station: In effect, any radio transmitter a licensed operator touches the controls of, becomes the radio station on that amateur's license. An amateur radio station may be operated under the call sign of the owner of the station (if they are near the controls), or the call sign of the person operating the station as a guest.
In some countries, special call signs might be made available for clubs, and are frequently used at a club station established for use of the club's members. Other special call-signs similar to club stations are sometimes temporarily assigned for "event stations" on special occasions, such as public events or radio-amateur expeditions to transmit from distant locations (DX-peditions). Like a club station, all the operators present for the event use the event call sign rather than their own.
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https://en.wikipedia.org/wiki/Mobile_rig
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TheMobile Telephone Service(MTS) was a pre-cellularVHFradio system that linked to thePublic Switched Telephone Network(PSTN). MTS was the radiotelephone equivalent of land dial phone service.
The Mobile Telephone Service was one of the earliest mobile telephone standards. It was operator assisted in both directions, meaning that if one were called from aland linethe call would be routed to a mobile operator, who would route it to one's phone. Similarly, to make an outbound call one had to go through the mobile operator, who would ask for the mobile number and the number to be called, and would then place the call.
This service originated with theBell System, and was first used inSt. Louis, Missouri, United States on June 17, 1946. The original equipment weighed 80 pounds (36 kg), and there were initially only 3 channels for all the users in the metropolitan area, later more licenses were added bringing the total to 32 channels across 3 bands (seeIMTS frequencies). This service was used at least into the 1980s in large portions of North America.[1]On October 2, 1946,Motorolacommunications equipment carried the first calls onIllinois Bell Telephone Company's new car radiotelephone service inChicago.[2][3]Due to the small number of radio frequencies available, the service quickly reached capacity.
MTS was replaced byImproved Mobile Telephone Service(IMTS), introduced in 1964.
MTS uses 25 VHF radio channels in theUnited StatesandCanada. The channels are identified by pairs of letters taken from positions on a North Americantelephonedial that, when changed to digits, form (for 12-channel mobile sets) 55, 57, 95 and 97.[clarification needed]
In the 1960s plan, the VHF high-band allocations provided for 11 channels in the United States: JL, YL, JP, YP, YJ, YK, JS, YS, YR, JK and JR. In Canada, two additional channels were available: JJ and JW.
These channels are prone tonetwork congestionandinterferencesince a radio closer to the terminal will sometimes take over the channel due to having a more powerful signal. The service uses technology that has been manufacturer discontinued for more than three decades.
The driver for replacement in most of North America, particularly large cities, was congestion, the inability of the network to carry more than two dozen channels in a geographic area. Cellular service resolved this congestion problem very effectively, especially since cellular frequencies, typically UHF, do not reach as far as VHF frequencies and can therefore be reused. The ability of a cellular system to use signal strength to choose channels and split cells into smaller units also helps expand channel capacity.
The driver for replacement in remote areas, however, is not network congestion, butobsolescence. Because the equipment is no longer manufactured, companies still using the service must struggle to keep their equipment operating, either by cannibalising from retired equipment or improvising solutions. Due to insufficient traffic, cellular is not a cost-effective replacement. Currently, the only viable solution issatellite telephony, as the small number of "base stations" which orbit the planet serve large geographic regions as they pass over. Cost, however, has been an issue, and the replacement has become acceptable to VHF mobile customers gradually, as the cost of satellite telephony has been dropping and will continue to drop.
Many MTSfrequenciesare now used for localpagingservices. They are only found in some parts of rural North America, having been replaced in most areas by cellular service in the 1980s or later.
All calls were placed by a suitably equipped telephone operator.
Outgoing calls were placed when the operator connected to a base station (originally using a cord board, but by the 1990s could be done by dialing a code sequence from aTOPSposition), then announced the call over the channel (giving the channel's name first), e.g.,
The page would usually be repeated twice more after a pause. The called party had to have their unit on and the volume set at a level that allowed them to notice a call and then listen to the called number. If the called party heard an incoming call, they would then use the microphone to announce they were receiving the call, and the operator would allow the two parties to speak, monitoring for the end of the call and marking a manual ticket for billing.
The format of such "voice-called" mobile customer numbers varied by jurisdiction.B.C. Tel, for example, used seven-character numbers starting with N or H, a digit (often 1), then five more digits for the individual customer.AGTin Alberta used seven-character numbers.
Soon enough, customer equipment, "selective call", was developed that had a built-in circuit that could be programmed to recognize a five-digit code as its own, in a manner similar to IMTS systems and crude compared to cellular phones. The phone company would assign the customer a number and the customer would have it programmed into the set by the phone company or by a dealer.
The operator would connect to the base station by cord board and key the five-digit number; in the 1990s, phone operators at TOPS positions would key the five digits after dialing the code to initiate the call and then identify the base station; a typical TOPS operator code would consist of a two digit sequence for voice-call or selective call, a three digit sequence for the base station, then the customer number.
The base station would signal the five digit sequence; any and all radios tuned to that base station would detect the sequence and compare it with their own; if it matched, the unit would signal its user with a bell or buzzer, and the user could then answer and announce the identity of their unit, similar to how a voice-call user would respond.
Calls from mobile units to a base station were started by signaling the operator by pressing the microphone button. The operator would plug into the channel (automated TOPS systems routed the incoming call through the normal queue), announce availability and the channel name, and the customer would identify their mobile number. (Security systems were sometimes adopted later to prevent fraud, by the customer giving a confidential number. In an automated connection to the operator, other radios on the base station could hear the transmission from the station, not what the radio user was transmitting.) The customer would then specify the details of their call, either to another mobile or to a landline number, which the operator would then place. The call was manually ticketed prior to the use of TOPS, and automatically ticketed if the mobile user was automatically connected to the TOPS operator.
Very few companies automated MTS to use TOPS as most were able to discontinue MTS services due to the reasons above: they could not meet the service demand except by switching to cellular.Northwestelwas one company still offering MTS that tied the base stations into TOPS.
A variant of MTS used short-wave frequencies, and was known as High Frequency or High Frequency-Single Sideband, so named for using frequencies between 3 and 30 MHz. These services required far fewer base stations and were used to reach distant locations over vast territories. The drawback was that the frequencies were extremely noisy from various interference, and were subject to propagation problems due to time of day, mostly due to the sun's effect on the ionosphere. Northwestel, which discontinued the service shortly after 2000, could not tie this system into TOPS, and had to aurally monitor the channels using speakers to listen for incoming calls.
For billing purposes, many MTS base stations were identified with a very close-by rate center of an automatic exchange. However, if there was no nearby rate center, they became an "Other Place Point". Phone companies typically identified these, and single points such as an individual telephone in a rural area, using a six-digit combination of 88T-XXX, where T is a digit from 6 to 9, and X is any digit 0-9. For example, Fox Lake, Yukon Territory, was 889-949. This combination would serve the same purpose as theNANParea code and central office code, with its own latitudinal-longitudinal coordinates, to allow a distance to be calculated for rating of a call. This coding system, which was in its zenith of usage during the 1980s and 1990s, was rendered unusable when the North American Numbering Plan administrator withdrew the 88X codes for future use as toll free (e.g. 1-800-) services.
By the end of the 1990s, very few companies still had need of the Other Place Point codes, and other rating arrangements were made. For example, Northwestel would use the nearest exchange for calls to its mobile points from other phone companies, and would code the locations in its billing software for calls within the company's operating territory. The rate impact was negligible for calls over longer distances.
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https://en.wikipedia.org/wiki/Mobile_Telephone_Service
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Aradiotelephone(orradiophone), abbreviatedRT,[1]is aradio communicationsystem for conducting aconversation;radiotelephonymeanstelephonyby radio. It is in contrast toradiotelegraphy, which is radio transmission oftelegrams(messages), ortelevision, transmission ofmoving picturesand sound. The term is related toradio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically totwo-way radiosystems for bidirectional person-to-person voice communication between separated users, such asCB radioormarine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with thetelephone network, and in some radio services, includingGMRS,[2]interconnection is prohibited.
The wordphonehas a long precedent beginning with early US wired voice systems. The term meansvoiceas opposed to telegraph orMorse code. This would include systems fitting into the category of two-way radio or one-way voice broadcasts such as coastal maritime weather. The term is still popular in theamateur radiocommunity and in USFederal Communications Commissionregulations.
A standardlandlinetelephone allows both users to talk and listen simultaneously; effectively there are two opencommunication channelsbetween the two end-to-end users of the system. In a radiotelephone system, this form of working, known asfull-duplex, requires a radio system to simultaneously transmit and receive on two separate frequencies, which both wastesbandwidthand presents some technical challenges. It is, however, the most comfortable method of voice communication for users, and it is currently used in cell phones and was used in the formerIMTS.
The most common method of working for radiotelephones ishalf-duplex, operation, which allows one person to talk and the other to listen alternately. If a single frequency is used, both parties take turns to transmit on it, known as simplex. Dual-frequency working or duplex splits the communication into two separate frequencies, but only one is used to transmit at a time with the other frequency dedicated to receiving.
The user presses a special switch on the transmitter when they wish to talk—this is called the "press-to-talk" switch or PTT. It is usually fitted on the side of the microphone or other obvious position. Users may use aprocedural code-wordsuch as "over" to signal that they have finished transmitting.[3]
Radiotelephones may operate at anyfrequencywhere they are licensed to do so, though typically they are used in the various bands between 60 and 900MHz(25and 960 MHz in the United States). They may use simplemodulationschemes such asAMorFM, or more complex techniques such as digital coding,spread spectrum, and so on. Licensing terms for a given band will usually specify the type of modulation to be used. For example,airbandradiotelephones used for air to ground communication between pilots and controllers operates in theVHFband from 118.0 to 136.975 MHz, using amplitude modulation.
Radiotelephonereceiversare usually designed to a very high standard, and are usually of thedouble-conversion superhetdesign. Likewise, transmitters are carefully designed to avoid unwanted interference and feature power outputs from a few tens of milliwatts to perhaps 50wattsfor a mobile unit, up to a couple of hundred watts for abase station. Multiple channels are often provided using afrequency synthesizer.
Receivers usually feature asquelchcircuitto cut off theaudiooutput from the receiver when there is notransmissionto listen to. This is in contrast tobroadcastreceivers, which often dispense with this.
Often, on a small network system, there are many mobile units and one main base station. This would be typical for police or taxi services for example. To help direct messages to the correct recipients and avoid irrelevant traffic on the network being a distraction to other units, a variety of means have been devised to create addressing systems.
The crudest and oldest of these is calledCTCSS, or Continuous Tone-Controlled Squelch System. This consists of superimposing a precise very low frequency tone on the audio signal. Only the receiver tuned to this specific tone turns the signal into audio: this receiver shuts off the audio when the tone is not present or is a different frequency. By assigning a unique frequency to each mobile, private channels can be imposed on a public network. However this is only a convenience feature—it does not guarantee privacy.
A more commonly used system is called selective calling orSelcall. This also uses audio tones, but these are not restricted to sub-audio tones and are sent as a short burst in sequence. The receiver will be programmed to respond only to a unique set of tones in a precise sequence, and only then will it open the audio circuits for open-channel conversation with the base station. This system is much more versatile than CTCSS, as relatively few tones yield a far greater number of "addresses". In addition, special features (such as broadcast modes and emergency overrides) can be designed in, using special addresses set aside for the purpose. A mobile unit can also broadcast a Selcall sequence with its unique address to the base, so the user can know before the call is picked up which unit is calling. In practice many selcall systems also have automatictranspondingbuilt in, which allows the base station to "interrogate" a mobile even if the operator is not present. Such transponding systems usually have a status code that the user can set to indicate what they are doing. Features like this, while very simple, are one reason why they are very popular with organisations that need to manage a large number of remote mobile units. Selcall is widely used, though is becoming superseded by much more sophisticated digital systems.
Mobile radio telephonesystems, such asMobile Telephone ServiceandImproved Mobile Telephone Service, allowed a mobile unit to have a telephone number allowing access from the general telephone network, although some systems required mobile operators to set up calls to mobile stations. Mobile radio telephone systems before the introduction ofcellular telephoneservices suffered from few usable channels, heavy congestion, and very high operating costs.
TheMarine Radiotelephone ServiceorHF ship-to-shoreoperates onshortwaveradio frequencies, usingsingle-sideband modulation. The usual method is that a ship calls a shore station, and the shore station's marine operator connects the caller to thepublic switched telephone network. This service is retained for safety reasons, but in practice has been made obsolete by satellite telephones (particularly INMARSAT) andVoIPtelephone and email viasatellite internet.
Short wave radio is used because it bounces between theionosphereand the ground, giving a modest 1,000 watt transmitter (the standard power) a worldwide range.[4]
Most shore stations monitor several frequencies. The frequencies with the longest range are usually near 20MHz, but the ionosphere weather (propagation) can dramatically change which frequencies work best.
Single-sideband (SSB) is used because the short wave bands are crowded with many users, and SSB permits a single voice channel to use a narrower range of radio frequencies (bandwidth) when compared to earlier AM systems.[5]SSB uses about 3.5kHz, whileAM radiouses about 8 kHz, andnarrowband(voice or communication-quality)FMuses 9 kHz.
Marine radiotelephone first became common in the 1930s, and was used extensively for communications to ships and aircraft over water.[6]In that time, most long-range aircraft had long-wire antennas that would be let out during a call, and reeled-in afterward. Marine radiotelephony originally used AM mode in the 2-3 MHz region before the transition to SSB and the adoption of various higher frequency bands in addition to the 2 MHz frequencies.
One of the most important uses of marine radiotelephony has been to change ships' itineraries, and to perform other business at sea.
In the United States, since the Communications Act of 1934 theFederal Communications Commission(FCC) has issued various commercial "radiotelephone operator" licenses and permits to qualified applicants. These allow them to install, service, and maintain voice-only radio transmitter systems for use on ships and aircraft.[7](Until deregulation in the 1990s they were also required for commercial domestic radio and television broadcast systems. Because of treaty obligations they are still required for engineers of internationalshortwavebroadcast stations.) The certificate currently issued is thegeneral radiotelephone operator license.
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https://en.wikipedia.org/wiki/Radiotelephone
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Asatellite telephone,satellite phoneorsatphoneis a type of mobile phone that connects to other phones or thetelephone networkbyradiolink throughsatellitesorbiting the Earth instead of terrestrialcell sites, as cellphones do. Therefore, they can work in most geographic locations on the Earth's surface, as long as open sky and the line-of-sight between the phone and the satellite are provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions. Satellite phones provide similar functionality to terrestrial mobile telephones;voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a satellite phone is that it can be used in such regions where local terrestrial communication infrastructures, such aslandlineandcellularnetworks, are not available.
Satellite phones are popular on expeditions into remote locations where there is no reliable cellular service, such as recreational hiking, hunting, fishing, and boating trips, as well as for business purposes, such as mining locations and maritime shipping.[1]Satellite phones rarely get disrupted by natural disasters on Earth or human actions such as war, so they have proven to be dependable communication tools in emergency and humanitarian situations, when the local communications system have been compromised.[2]
The mobile equipment, also known as a terminal, varies widely. Early satellite phone handsets had a size and weight comparable to that of alate-1980s or early-1990s mobile phone, but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while someprototypesatellite phones have no distinguishable difference from an ordinarysmartphone.[3][4]
A fixed installation such as one used aboard a ship may include large, rugged, rack-mounted electronics, and a steerablemicrowaveantenna on the mast that automatically tracks the overhead satellites. Smaller installations usingVoIPover a two-waysatellite broadbandservice such asBGANorVSATbring the costs within the reach of leisure vessel owners. Internet service satellite phones have notoriously poor reception indoors, though it may be possible to get a consistent signal near a window or in the top floor of a building if the roof is sufficiently thin. The phones have connectors for external antennas that can be installed in vehicles and buildings. The systems also allow for the use of repeaters, much like terrestrial mobile phone systems.
In the early 2020s various manufacturers began to integrate satellite messaging connectivity and satellite emergency services into conventional mobile phones for use in remote regions, where there is no reliable terrestrial network.
The first satellite relayed phone calls were achieved early on in the space age, after the first relay test was conducted byPioneer 1and the first broadcast bySCOREin 1958 at the end of the year, afterSputnik Ibecame at the beginning of the year the first satellite in history.
MARISATwas the first mobile communications satellite, eventually operated by the first privatized satellite communicationINMARSATorganization, which was formed in 1979.[5]
Satellite phone systems can be classified into two types: systems that use satellites in a highgeostationaryorbit, 35,786 kilometres (22,236 mi) above the Earth's surface, and systems that use satellites inlow Earth orbit(LEO), 640 to 1,120 kilometers (400 to 700 miles) above the Earth. The connection and regular data order and infrastructure order can be found in this image.
Some satellite phones use satellites ingeostationary orbit(GSO), which appear at a fixed position in the sky. These systems can maintain near-continuous global coverage with only three or four satellites, reducing the launch costs. The satellites used for these systems are very heavy (about 5000 kg) and expensive to build and launch. The satellites orbit at an altitude of 35,786 kilometres (22,236 mi) above the Earth's surface; a noticeable delay is present while making a phone call or using data services due to the large distance from users. The amount of bandwidth available on these systems is substantially higher than that of the low Earth orbit systems; all three active systems provide portable satellite Internet using laptop-sized terminals with speeds ranging from 60 to 512 kbit per second (kbps).
Geostationary satellite phones can only be used at lower latitudes, generally between 70 degrees north of the equator and 70 degrees south of the equator. At higher latitudes the satellite appears at such a low angle in the sky thatradio frequency interferencefrom terrestrial sources in the same frequency bands can interfere with the signal.
Another disadvantage of geostationary satellite systems is that in many areas—even where a large amount of open sky is present—the line-of-sight between the phone and the satellite is broken by obstacles such as steep hills and forest. The user will need to find an area with line-of-sight before using the phone. This is not the case with LEO services: even if the signal is blocked by an obstacle, one can wait a few minutes until another satellite passes overhead, but a GSO satellite may drop a call when line of sight is lost.
Satellite phones may use satellites in low Earth orbit (LEO). The advantages include the possibility of providing worldwide wireless coverage with no gaps. LEO satellites orbit the Earth in high-speed, low-altitude orbits with an orbital time of 70–100 minutes, an altitude of 640 to 1,120 kilometers (400 to 700 miles). Since the satellites are not geostationary, they move with respect to the ground. Any given satellite is only in view of a phone for a short time, so the call must be "handed off" electronically to another satellite when one passes beyond the local horizon. Depending on the positions of both the satellite and terminal, a usablepassof an individual LEO satellite will typically last 4–15 minutes on average.[6]At least one satellite must have line-of-sight to every coverage area at all times to guarantee coverage; thus a constellation of satellites, typically 40 to 70, is required to maintain worldwide coverage.
Both systems, based in the United States, started in the late 1990s, but soon went into bankruptcy after failing to gain enough subscribers to fund launch costs. They are now operated by new owners who bought the assets for a fraction of their original cost and are now both planning to launch replacement constellations supporting higher bandwidth. Data speeds for current networks are between 2200 and 9600 bit/s using a satellite handset.
A third system was announced in 2022 whenT-Mobile USandSpaceXannounced a partnership to add satellite cellular service toStarlinksecond generation (Gen2) satellites that are to begin launching to orbit in late 2022. The service is aimed to providedead-zonecell phone coverage across the US using existingmidband PCSspectrum that T-Mobile owns.[9]Cell coverage will begin withmessagingand expand to include voice and limited data services later, with testing to begin in 2023. With Starlink Gen2 satellites in low Earth orbit using existingPCSspectrum, T-Mobile plans to be able to connect ordinary mobile phones to satellites, unlike earlier satellite phones in the market which used specialized radios to connect to geosynchronous-orbit satellites, which have longer communicationslatencies.[10]T-Mobile has offered to extend the offering globally if cellular carriers in other countries wish to exchange roaming services via the T-Mobile partnership with SpaceX, with other carriers working with theirregulatorsto enable midband communicationslanding rightson a country-by-country basis. Bandwidth will be limited to approximately 2 to 4 megabits per second spread across a very large cell coverage area, with thousands of voice calls or millions of text messages simultaneously in an area. The size of a single coverage area has not yet been specified.[10]
LEO systems have the ability totrack a mobile unit's locationusingDoppler navigationfrom the satellite.[11]However, this method can be inaccurate by tens of kilometers. On some Iridium hardware the coordinates can be extracted usingAT commands, while recent Globalstar handsets will display them on the screen.[12]
Most VSAT terminals can be reprogrammed in-field using AT-commands to bypass automatic acquisition of GPS coordinates and instead accept manually injected GPS coordinates.
Satellite phones are usually issued with numbers in a specialcountry calling code.
Inmarsat satellite phones are issued with codes +870. In the past, additional country codes were allocated to different satellites, but the codes +871 to +874 were phased out at the end of 2008 leaving Inmarsat users with the same country code, regardless of which satellite their terminal is registered with.[13]
Low Earth orbit systems including some of the defunct ones have been allocated number ranges in theInternational Telecommunication Union'sGlobal Mobile Satellite Systemvirtual country code +881. Iridium satellite phones are issued with codes +881 6 and +881 7. Globalstar, although allocated +881 8 and +881 9 useU.S. telephone numbersexcept for service resellers located in Brazil, which use the +881 range.
Small regional satellite phone networks are allocated numbers in the +882 code designated for "international networks" which is not used exclusively for satellite phone networks.
While it is possible to obtain used handsets for the Thuraya, Iridium, and Globalstar networks for approximatelyUS$200, the newest handsets are quite expensive. The Iridium 9505A, released in 2001, sold in March 2010 for over $1,000.[14]Satellite phones are purpose-built for one particular network and cannot be switched to other networks. The price of handsets varies with network performance. If a satellite phone provider encounters trouble with its network, handset prices will fall, then increase once new satellites are launched. Similarly, handset prices will increase when calling rates are reduced.
Among the most expensive satellite phones areBGANterminals, often costing several thousand dollars.[15][16]These phones provide about 0.5 Mbit/s Internet and voice communications. Satellite phones are sometimes subsidised by the provider if one signs a post-paid contract, but subsidies are usually only a few hundred dollars or less.
Since most satellite phones are built under license or the manufacturing of handsets is contracted out toOEMs, operators have a large influence over the selling price. Satellite networks operate underproprietary protocols, making it difficult for manufacturers to independently make handsets.
A startup is proposing the use of standard mobile phone technology in satellites to enable low bandwidth text message with satellites from cheap mobile phones.[17]
The cost of making voice calls from a satellite phone varies from around $0.15 to $2 per minute, while calling them fromlandlinesand regular mobile phones is more expensive. Costs for data transmissions (particularly broadband data) can be much higher. Rates from landlines and mobile phones range from $3 to $14 per minute with Iridium, Thuraya[18]and Inmarsat being some of the most expensive networks to call. The receiver of the call pays nothing, unless they are being called via a special reverse-charge service.
Calls between different satellite phone networks are often very expensive, with calling rates of up to $15 per minute.
Calls from satellite phones to landlines are usually around $0.80 to $1.50 per minute unless special offers are used. Such promotions are usually bound to a particular geographic area where traffic is low.
Most satellite phone networks have pre-paid plans, with vouchers ranging from $100 to $5,000.
Some satellite phone networks provide a one-way paging channel to alert users in poor coverage areas (such as indoors) of the incoming call. When the alert is received on the satellite phone it must be taken to an area with better coverage before the call can be accepted.
Globalstar provides a one-way data uplink service, typically used for asset tracking.
Iridium operates a one-waypagerservice as well as the call alert feature.
In some countries, possession of a satellite phone is illegal.[19]Their signals will usually bypass local telecoms systems, hindering censorship andwiretappingattempts, which has led some intelligence agencies to believe that satellite phones aid terrorist activity.[20]It is also common for restrictions to be in place in countries with oppressive governments regimes as a way to both expose subversive agents within their country and maximize the control of the information that makes it past their borders.[21]
All modern satellite phone networksencryptvoice traffic to prevent eavesdropping. In 2012, a team of academicsecurity researchersreverse-engineeredthe two major proprietary encryption algorithms in use.[37]One algorithm (used in GMR-1 phones) is a variant of theA5/2algorithm used inGSM(used in common mobile phones), and both are vulnerable tocipher-text onlyattacks. The GMR-2 standard introduced a new encryption algorithm which the same research team alsocryptanalysedsuccessfully. Thus satellite phones need additional encrypting if used for high-security applications.
Most mobile telephone networks operate close to capacity during normal times, and large spikes in call volumes caused by widespread emergencies often overload the systems when they are needed most. Examples reported in the media where this has occurred include the1999 İzmit earthquake, theSeptember 11 attacks, the2006 Kiholo Bay earthquake, the2003 Northeast blackouts,Hurricane Katrina,[38]the2007 Minnesota bridge collapse, the2010 Chile earthquake, and the2010 Haiti earthquake. Reporters and journalists have also been using satellite phones to communicate and report on events in war zones such as Iraq.
Terrestrial cell antennas and networks can be damaged by natural disasters. Satellite telephony can avoid this problem and be useful during natural disasters. Satellite phone networks themselves are prone to congestion as satellites and spot beams cover a large area with relatively few voice channels.
In the early 2020s, manufacturers began to integrate satellite connectivity intosmartphonedevices for use in remote areas, out of thecellular networkrange.[39][40]The satellite-to-phone services useL bandfrequencies, which are compatible with most modern handsets.[41][42]However, due to the antenna limitations in the conventional phones, in the early stages of implementation satellite connectivity is limited to satellite messaging and satellite emergency services.[43][44]
In 2018,Thurayaproposed a mobile phone capable[45]of both classic cellular plus satellite connectivity,[46]the X5 Touch, whom to be the world's first bi-typessatellite plus cellularsmartphone.
Three years later, in 2021,Thurayalaunched its second bi-typesatellite plus cellularphone, the XT Lite, a reviewed of the X5 model.[47]
In 2022, theAppleiPhone 14started supporting sending emergency text messages viaGlobalstarsatellites. Apple later acquires a 20% stake in the company in 2024.[48]It is however not the first mobile phone to combine both cellular and satellite connectivity.[46]In 2023, theAppleiPhone 15added satellite communication with roadside service in the United States.[49]In 2024, six years after the first bi-technology mobile phone,Thurayalaunches the Skyphone, its new edition of 2018's one,[50]also made for2G/3G/4Gand satellite convergence within anAndroïd-based phone.
Recent Developments
In recent years, some smartphone manufacturers have started adding satellite communication features directly into their devices. For instance, Apple introduced Emergency SOS via satellite with the iPhone 14, allowing users to send emergency messages when they’re outside of cellular coverage. This feature represents a shift toward making satellite connectivity more accessible to everyday users without requiring a separate satellite phone.[51]
Accessibility and Market Trends
The demand for reliable communication in remote areas has been steadily growing, especially in the face of natural disasters and the rise of remote work. To meet this need, companies like SpaceX and AST SpaceMobile are working on new satellite networks using low Earth orbit (LEO) satellites. These networks are designed to offer wider coverage and faster connections, potentially making satellite communication more affordable and practical for everyday use.[52]
In 2022,T-Mobileformed a partnership to useStarlinkservices via existingLTEspectrum, expected in late 2024.[53][54][55][56]In 2022,AST SpaceMobilestarted building a3GPPstandard-based cellular space network to allow existing, unmodified smartphones to connect to satellites in areas with coverage gaps.[57][58]
In 2023,Qualcommannounced Snapdragon Satellite, the service that will allow supported cellphones, starting withSnapdragon8 Gen 2 chipset, to send and receive text messages via5GNon-Terrestrial Networks(NTN).[59]
In 2024,Iridiumintroduced Project Stardust, a standard-based satellite-to-cellphone service supported viaNB-IoTfor 5G non-terrestrial networks, which will be used over Iridium's existing low-earth orbit satellites. Scheduled for launch in 2026, the service provides messaging, emergency communications andIoTfor devices like cars, smartphones, tablets and related consumer applications.[60][61]
Recent Developments: In recent years, some smartphone manufacturers have started adding satellite communication features directly into their devices. For instance, Apple introduced Emergency SOS via satellite with the iPhone 14, allowing users to send emergency messages when they’re outside of cellular coverage. This feature represents a shift toward making satellite connectivity more accessible to everyday users without requiring a separate satellite phone.[62]
Accessibility and Market Trends: The demand for reliable communication in remote areas has been steadily growing, especially in the face of natural disasters and the rise of remote work. To meet this need, companies like SpaceX and AST SpaceMobile are working on new satellite networks using low Earth orbit (LEO) satellites. These networks are designed to offer wider coverage and faster connections, potentially making satellite communication more affordable and practical for everyday use.[63]
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Intelecommunications,broadbandorhigh speedis the wide-bandwidthdata transmissionthat exploits signals at a wide spread of frequencies or several different simultaneous frequencies, and is used in fastInternet access. Thetransmission mediumcan becoaxial cable,optical fiber,wireless Internet(radio),twisted paircable, orsatellite.
Originally used to mean 'using a wide-spread frequency' and for services that were analog at the lowest level, nowadays in the context ofInternet access, 'broadband' is often used to mean any high-speed Internet access that is seemingly always 'on' and is faster thandial-up accessover traditionalanalogorISDNPSTNservices.[1]
The idealtelecommunication networkhas the following characteristics:broadband,multi-media,multi-point,multi-rateand economical implementation for a diversity of services (multi-services).[2][3]TheBroadband Integrated Services Digital Network(B-ISDN) was planned to provide these characteristics.Asynchronous Transfer Mode(ATM) was promoted as a target technology for meeting these requirements.[3]
Different criteria for "broad" have been applied in different contexts and at different times. Its origin is in physics,acoustics, and radio systems engineering, where it had been used with a meaning similar to "wideband",[4][5]or in the context of audionoise reduction systems, where it indicated a single-band rather than a multiple-audio-band system design of thecompander. Later, with the advent ofdigital telecommunications, the term was mainly used for transmission overmultiple channels. Whereas apassbandsignal is also modulated so that it occupies higher frequencies (compared to abasebandsignal which is bound to the lowest end of the spectrum, seeline coding), it is still occupying a single channel. The key difference is that what is typically considered abroadband signalin this sense is a signal that occupies multiple (non-masking,orthogonal) passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry.
The term became popularized through the 1990s as a marketing term forInternet accessthat was faster thandial-up access(dial-up being typically limited to a maximum of 56 kbit/s). This meaning is only distantly related to its original technical meaning.
Since 1999, broadband Internet access has been a factor inpublic policy. In that year, at theWorld Trade OrganizationBiannual Conference called “Financial Solutions to Digital Divide” in Seattle, the term “Meaningful Broadband” was introduced to the world leaders, leading to the activation of a movement to close thedigital divide. Fundamental aspects of this movement are to suggest that the equitable distribution of broadband is a fundamental human right.[6]
Personal computing facilitated easy access, manipulation, storage, and exchange of information, and required reliable data transmission. Communicating documents by images and the use of high-resolution graphics terminals provided a more natural and informative mode of human interaction than do voice and data alone.Video teleconferencingenhances group interaction at a distance. High-definition entertainment video improves the quality of pictures, but requires much higher transmission rates.
These new data transmission requirements may require new transmission means other than the present overcrowded radio spectrum.[7][8]A modern telecommunications network (such as the broadband network) must provide all these different services (multi-services) to the user.
Conventionaltelephonycommunication used:
Modern services can be:
These aspects are examined individually in the following three sub-sections.[9]
A multimedia call may communicate audio, data, still images, or full-motionvideo, or any combination of these media. Each medium has different demands for communication quality, such as:
The information content of each medium may affect the information generated by other media. For example, voice could be transcribed into data via voice recognition, and data commands may control the way voice and video are presented. These interactions most often occur at the communication terminals, but may also occur within the network.[3][7]
Traditional voice calls are predominantly two party calls, requiring a point-to-point connection using only the voice medium. To access pictorial information in a remote database would require a point-to-point connection that sends low bit-rate queries to the database and high bit-rate video from the database. Entertainment video applications are largely point-to-multi-point connections, requiring one way communication of full motion video and audio from the program source to the viewers. Video teleconferencing involves connections among many parties, communicating voice, video, as well as data. Offering future services thus requires flexible management of the connection and media requests of a multipoint, multimedia communication call.[7][8]
A multirate service network is one which flexibly allocates transmission capacity to connections. A multimedia network has to support a broad range of bit-rates demanded by connections, not only because there are many communication media, but also because a communication medium may be encoded by algorithms with different bit-rates. For example, audio signals can be encoded with bit-rates ranging from less than 1 kbit/s to hundreds of kbit/s, using different encoding algorithms with a wide range of complexity and quality of audio reproduction. Similarly, full motion video signals may be encoded with bit-rates ranging from less than 1 Mbit/s to hundreds of Mbit/s. Thus a network transporting both video and audio signals may have to integrate traffic with a very broad range of bit-rates.[7][9]
Traditionally, different telecommunications services were carried via separate networks: voice on the telephone network, data oncomputer networkssuch aslocal area networks, video teleconferencing on private corporate networks, and television onbroadcastradio or cable networks.
These networks were largely engineered for a specific application and are not suited to other applications. For example, the traditional telephone network is too noisy and inefficient for bursty data communication. On the other hand, data networks which store and forward messages using computers had limited connectivity, usually did not have sufficient bandwidth for digitised voice and video signals, and suffer from unacceptable delays for the real-time signals. Television networks using radio or cables were largely broadcast networks with minimum switching facilities.[3][7]
It was desirable to have a single network for providing all these communication services to achieve the economy of sharing. This economy motivates the general idea of an integrated services network. Integration avoids the need for many overlaying networks, which complicates network management and reduces flexibility in the introduction and evolution of services. This integration was made possible with advances in broadband technologies and high-speed information processing of the 1990s.[3][7]
While multiple network structures were capable of supporting broadband services, an ever-increasing percentage of broadband and MSO providers opted for fibre-optic network structures to support both present and future bandwidth requirements.
CATV(cable television),HDTV(high definition television),VoIP(voice over internet protocol), andbroadband internetare some of the most common applications now being supported by fibre optic networks, in some cases directly to the home (FTTh – Fibre To The Home). These types of fibre optic networks incorporate a wide variety of products to support and distribute the signal from the central office to an optic node, and ultimately to the subscriber (end-user).
Intelecommunications, a broadband signalling method is one that handles a wide band of frequencies. "Broadband" is a relative term, understood according to its context. The wider (or broader) thebandwidthof a channel, the greater the data-carrying capacity, given the same channel quality.
Inradio, for example, a very narrow band will carryMorse code, a broader band will carry speech, and a still broader band will carrymusicwithout losing the highaudio frequenciesrequired for realisticsound reproduction. This broad band is often divided into channels or "frequency bins" usingpassbandtechniques to allowfrequency-division multiplexinginstead of sending a higher-quality signal.
In data communications, a56k modemwill transmit a data rate of 56 kilobits per second (kbit/s) over a 4-kilohertz-widetelephone line(narrowband orvoiceband). In the late 1980s, theBroadband Integrated Services Digital Network(B-ISDN) used the term to refer to a broad range ofbit rates, independent of physical modulation details.[10]The various forms ofdigital subscriber line(DSL) services arebroadbandin the sense that digital information is sent over multiple channels. Each channel is at a higher frequency than thebasebandvoice channel, so it can supportplain old telephone serviceon a single pair of wires at the same time.[11]However, when that same line is converted to anon-loadedtwisted-pair wire (no telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry up to 100 megabits per second using very high-bit rate digital subscriber line (VDSLor VHDSL) techniques.[12]
Modern networks have to carry integratedtrafficconsisting of voice, video and data. TheBroadband Integrated Services Digital Network(B-ISDN) was designed for these needs.[13]The types of traffic supported by a broadband network can be classified according to three characteristics:[14]
Cellular networksutilize various standards for data transmission, including5Gwhich can support one million separate devices per square kilometer.
The types of traffic found in a broadband network (with examples) and their respective requirements are summarised in Table 1.
Manycomputer networksuse a simpleline codeto transmit one type of signal using a medium's full bandwidth using itsbaseband(from zero through the highest frequency needed). Most versions of the popularEthernetfamily are given names, such as the original 1980s10BASE5, to indicate this. Networks that usecable modemson standardcable televisioninfrastructure are called broadband to indicate the wide range of frequencies that can include multiple data users as well as traditional television channels on the same cable. Broadband systems usually use a differentradio frequencymodulated by the data signal for each band.[15]
The total bandwidth of the medium is larger than the bandwidth of any channel.[16]
The10BROAD36broadband variant of Ethernet was standardized by 1985, but was not commercially successful.[17][18]
TheDOCSISstandard became available to consumers in the late 1990s, to provideInternet accessto cable television residential customers. Matters were further confused by the fact that the10PASS-TSstandard for Ethernet ratified in 2008 used DSL technology, and both cable and DSL modems often have Ethernet connectors on them.
Atelevisionantenna may be described as "broadband" because it is capable of receiving a wide range of channels, while e.g. a low-VHF antenna is "narrowband" since it receives only 1 to 5 channels. The U.S. federal standard FS-1037C defines "broadband" as a synonym forwideband.[19]"Broadband" inanalogvideodistribution is traditionally used to refer to systems such ascable television, where the individual channels aremodulatedon carriers at fixed frequencies.[20]In this context,basebandis the term'santonym, referring to a single channel of analog video, typically incompositeform with separate basebandaudio.[21]The act of demodulating converts broadband video to baseband video. Fiber optic allows the signal to be transmitted farther without being repeated. Cable companies use a hybrid system using fiber to transmit the signal to neighborhoods and then changes the signal from light to radio frequency to be transmitted over coaxial cable to homes. Doing so reduces the use of having multiple head ends. Ahead endgathers all the information from the local cable networks and movie channels and then feeds the information into the system.
However, "broadband video" in the context ofstreamingInternet video has come to mean video files that havebit-rateshigh enough to require broadband Internet access for viewing. "Broadband video" is also sometimes used to describeIPTVVideo on demand.[22]
Power lineshave also been used for various types ofdata communication. Although some systems for remote control are based onnarrowbandsignaling, modern high-speed systems use broadband signaling to achieve very high data rates. One example is theITU-TG.hnstandard, which provides a way to create alocal area networkup to 1 Gigabit/s (which is considered high-speed as of 2014) using existing home business and home wiring (including power lines, but also phone lines andcoaxial cables).
In 2014, researchers atKorea Advanced Institute of Science and Technologymade developments on the creation of ultra-shallow broadbandoptical instruments.[23]
In the context ofInternet access, the term "broadband" is used loosely to mean "access that is always on and faster than the traditional dial-up access".[24][25]
A range of more precise definitions of speed have been prescribed at times, including:
Broadband Internet service in the United States was effectively treated or managed as apublic utilitybynet neutralityrules[30][31][32][33][34]until being overturned by the FCC in December 2017.[35]
A number of national and international regulators categorize broadband connections according to upload and download speeds, stated inMbit/s(megabitspersecond).
In Australia, theAustralian Competition and Consumer Commissionalso requiresInternet Service Providersto quote speed during night time and busy hours[44]
Bandwidth has historically been very unequally distributed worldwide, with increasing concentration in the digital age. Historically only 10 countries have hosted 70–75% of the global telecommunication capacity (see pie-chart Figure on the right).[45]In 2014, only three countries (China, the US, and Japan) host 50% of the globally installed telecommunication bandwidth potential. The U.S. lost its global leadership in terms of installed bandwidth in 2011, being replaced by China, which hosts more than twice as much national bandwidth potential in 2014 (29% versus 13% of the global total).[45]
Nation specific:
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TheDigital Britainreport was a policy document published in 2009, which outlined theUnited KingdomGovernment's strategic vision for ensuring that the country is at the leading edge of the globaldigital economy.
TheDigital Economy Act 2010was one of the outcomes of this policy.
The UK government announced on 29 January 2009 that it planned to have 100%broadbandcoverage in the UK by 2012, with a minimum speed of 2Mbit/s. Some industry experts, including broadband think tank PointTopic and measurement site SamKnows, claimed that these plans were ill thought out.[1]However, a government-backed forum hoped to address such issues, with a view to succeeding within the 2012 deadline.[2]
Closely based on a 2007 government-commissioned think tank report from The Work Foundation,[3]the final Digital Britain report was released on 16 June 2009,[4]and made a number of recommendations with regard to broadband access,internetuse andpublic service broadcasting. Among these recommendations were:
In August 2009, responsibility for the project was moved toStephen Timms, the Financial Secretary, who was previously the minister responsible fore-commerceand used to work in the telecoms industry. He reported toPeter Mandelson.[6]
Mandelson had been seeking a legal and regulatory attack oncopyright infringementbystatutory instrument.[7]In November 2009 he added these measures into theDigital Economy Bill, but faced objections from leading internet companies.[8]
ThePre-Budget Reportin December 2009 included a new tax of £6 p.a. on home land lines to fund the expansion of broadband.[9]This was included in theMarch 2010 United Kingdom Budget, but dropped from the Finance Bill due to lack of time after the general election was called.[10]In his Budget speech, ChancellorAlistair Darlinghad also announcedtax breaksfor the Britishvideo game industry, and reiterated the Government's target of 90% Broadband coverage by 2017—but omitted to repeat the target of 100% by 2020.[11]
In March 2010 theDepartment for Business, Innovation and Skillsannounced the National Plan for Digital Participation, aiming "to ensure that everyone who wants to be online can get online, do more online and benefit from the advantages of being online."[12]
The Digital Britain report served as a catalyst for a number of later initiatives led by the public and private sectors. In October 2019, theLord Mayor of Londonlaunched "future.now", a consortium of leading companies, education providers, and charities working in collaboration with government to empower everyone to thrive in a digital UK.[13][14]Pre-eminent firms in the digital economy including Accenture, BT Group, Digital British, Deloitte, and Nominet have either directly supported the coalition or made statements in support of improving digital skills for longer term economic benefit.
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MiFiis a brand ofwireless routerthat acts as a mobileWi-Fi hotspotdevice.
In many countries, includingThe United States,Canada, andMexico, Inseego Corp. (previously known as Novatel Wireless)[1]owns aregistered trademarkon the "MiFi" brand name; in theUnited Kingdom, mobile operatorHutchison 3Gowns the "MiFi" trademark. Novatel Wireless has never offered an official explanation for the origin of the name "MiFi"; it has been suggested that it is short for "My Wi-Fi".[2]
A MiFi device can be connected to acellular networkand provideInternet accessfor up to fifteen devices. Inseego Corp. introduced the first MiFi device in the United States in May 2009.[3]In the UK, Hutchison 3G's "MiFi" is a similar product fromHuaweiwith the same name.[4][5]
Novatel Wireless owns a registeredtrademarkon the "MiFi" brand name in the U.S. (includingPuerto Rico), and a number of countries worldwide:[6]Bahrain, Canada,Egypt,Germany,Ghana,Hungary,Japan,Kuwait,Mexico,Pakistan, theNetherlands,New Zealand,Poland,Portugal,Qatar,Romania,Singapore,Slovenia,South Africa,Spain, andThailand.[4][7][8][9]
The notable exception is in the UK, where mobile operator3owns the "MiFi" trademark. InIndiathe Mi-Fi trademark is owned by Mi-Fi Networks Private Limited.[10]
Same functionality as 2200, plus:
Same functionality as 23xx series, plus:
The Las VegasConsumer Electronics Show2011 saw the introduction of two new4G-capable MiFi devices from Novatel:
Both devices maintainbackward compatibilitywith existing 3G networks. Other features include:[16]
In November 2019,Vodafone Qatarand Inseego Corp. together launched the Gulf region’s first commercially available 5G mobile hotspot, 5G MiFi M1100.[18]
A number of providers other than Novatel provide personal hotspot, "MiFi"-like services:
Mobile phones with an Internet connection can often be turned intoWi-Fihotspots using a process called "tethering", which is similar to using dedicated MiFi devices.
The following phone families have built-in features to create Wi-Fi access point:
For other phones there are third-party applications to allow this:
In January 2010, two major security holes were discovered with the Novatel MiFi 2200 which, if properly exploited, could allow a malicious user to obtain the device's current GPS location and security keys. If the malicious user were physically close enough to use the device's Wi-Fi signal, this could give access to the MiFi's3Gconnection as well as any other connected devices.[44]Novatel responded that a security patch would be available in February 2010.[45]
The popularity of MiFi devices can also be problematic for corporate network security. Corporations generally expect to control on-site Internet access: many use firewalls to reduce the risk of malware, and some enforce restrictions aimed at employee productivity. Personal mobile hotspots may provide a "back door" by which employees can circumvent these precautions.[46]
In May 2010, the MiFi 2372 was recalled in Canada byBell MobilityandRogers Communications.[47]In two documented cases, the difficulty of opening the MiFi battery compartment had caused customers to use levels of force that caused physical damage to the batteries, which then overheated. Novatel replaced the recalled units with ones that have an easier-to-open battery compartment.
At two majortrade showsin 2010 —Google's first public demo ofGoogle TVand theiPhone 4demonstrations at the 2010Apple Worldwide Developers Conference— keynote presentations using available Wi-Fi connectivity were disrupted by network unreliability. The problem was traced to massiveradio interference, caused by the popularity of MiFi and similar devices for "liveblogging" from the trade show floor. AppleCEOSteve Jobssaid that 570 different Wi-Fi networks ("several hundred" being MiFi's[48]) had been operating simultaneously in theAppleexhibit hall.[49][50]
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Amobile enterpriseis a corporation or large organization that supports critical business functions and use of business applications viaremote workusingwirelessmobile devices. In a mobile enterprise, employees use mobile devices to do any or all of the following: access email, manage projects, manage documents, providecustomer relationship management, conductenterprise resource planning, fill out invoices and receipts, accounting vouchers, work orders, purchase orders, etc. and manage a corporate calendar and address book. These are the most common applications though many other corporate mobile applications are being developed and used by organizations around the world.
A mobile enterprise generally implies aggressive use of mobile technology facilitated by Internet-based data transmissions. As long as wireless network connectivity is available, enterprisedatabasescan be remotely accessed and updated from anywhere in the world, at any time, with any device equipped with aWeb browserand by anyone with permission to access such services. A mobile enterprise leverages existing Internet infrastructure andTCP/IPinstallations. In a mobile enterprise, mobile clients are at parity with other traditional clients such aslaptopanddesktop computers. The emphasis is on expedientdata interchangeand communication; little or no emphasis is placed on the method of access.
A mobile enterprise is generally accepted to confer benefits in the areas of higherworkforce productivityand employee satisfaction. Faster decision-making is another often cited benefit that results from employees having access to real-time data at the point of action, for example, during a meeting. Therefore, mobile knowledge workers (such as consultants) are one of the groups among employees which is equipped with mobile devices by their organization. However, the strategic adoption of mobile devices in enterprises often also requires a change management process.[1]Use of mobile applications in the workplace can increase worker productivity by as much as 45 percent.[2]
Security is not a major concern anymore, since critical data is stored on servers in highly secured data centers. The mobile devices are used as terminals for information access and updates only. TLS (see IETF RFC 5246) and its predecessor SSL (see IETF RFC 6101) security protocol is deployed between the web server and the web browser on the end user device. Lost devices is not a problem since both the data and the programs reside on the servers housed in the data centers and not on the mobile devices.
According to an article in CRM Guidebooks:
A recent Yankee Group survey “Anywhere Enterprise–Large: U.S. Mobility and Applications Survey” identified that businesses can realize the following advantages from mobile business apps:
The mobile enterprise depends entirely on the Internet as its infrastructure. The system breaks down when a user cannot connect to the Internet. The system does not work in places where Internet service is not available. The system is disrupted whenever the Internet suffers a disruption such as when underwater data cables are damaged by earthquakes as in the case of the2006 Hengchun earthquakeor2008 submarine cable disruptionin the Middle East that disrupted internet service between the Middle East and Europe.
The move to a more mobile, and dispersed, workplace is also resulting in changes to the definition of a successful employee. Some individuals, often called "self starters", can be highly effective working remotely without the influence of workmates or oversight of bosses in the same location. Others cannot, some even finding it difficult to start and complete projects without the social environment of the co-located workplace. Managers evaluating current and prospective employees must take these changes into account as they assign employees to their evolving mobile environments, attempting to match traits to workplace to maximize each employee's potential.
As for all mobile applications, bandwidth economy is a major consideration. Simplicity and minimalism is of utmost importance to reduce upload and download time for best user experience.
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High Speed Packet Access(HSPA)[1]is an amalgamation of twomobileprotocols—High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA)—that extends and improves the performance of existing3Gmobile telecommunication networks using theWCDMAprotocols. A further-improved3GPPstandard calledEvolved High Speed Packet Access(also known as HSPA+) was released late in 2008, with subsequent worldwide adoption beginning in 2010. The newer standard allowsbit ratesto reach as high as 337 Mbit/s in the downlink and 34 Mbit/s in the uplink; however, these speeds are rarely achieved in practice.[2]
The first HSPA specifications supported increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. They also reduced latency and provided up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink compared with original WCDMA protocol.
High Speed Downlink Packet Access(HSDPA) is an enhanced3G(third-generation)mobilecommunications protocolin the High-Speed Packet Access (HSPA) family. HSDPA is also known as3.5Gand3G+. It allows networks based on theUniversal Mobile Telecommunications System(UMTS) to have higher data speeds and capacity. HSDPA also decreaseslatency, and therefore theround-trip timefor applications.
HSDPA was introduced in3GPPRelease 5. It was accompanied by an improvement to the uplink that provided a new bearer of 384 kbit/s (the previous maximum bearer was 128 kbit/s).Evolved High Speed Packet Access(HSPA+), introduced in 3GPP Release 7, further increased data rates by adding 64QAM modulation,MIMO, andDual-Carrier HSDPAoperation. Under 3GPP Release 11, even higher speeds of up to 337.5 Mbit/s were possible.[3]
The first phase of HSDPA was specified in 3GPP Release 5. This phase introduced new basic functions and was aimed to achieve peak data rates of 14.0 Mbit/s with significantly reduced latency. The improvement in speed and latency reduced the cost per bit and enhanced support for high-performance packet data applications. HSDPA is based on shared channel transmission, and its key features are shared channel and multi-code transmission,higher-order modulation, shortTransmission Time Interval(TTI), fast link adaptation and scheduling, and fasthybrid automatic repeat request(HARQ). Additional new features include the High Speed Downlink Shared Channels (HS-DSCH),quadrature phase-shift keying, 16-quadrature amplitude modulation, and the High Speed Medium Access protocol (MAC-hs) in base stations.
The upgrade to HSDPA is often just a software update for WCDMA networks. In HSDPA, voice calls are usually prioritized over data transfer.
The following table is derived from table 5.1a of the release 11 of 3GPP TS 25.306[4]and shows maximum data rates of different device classes and by what combination of features they are achieved. The per-cell, per-stream data rate is limited by the "maximum number of bits of an HS-DSCH transport block received within an HS-DSCH TTI" and the "minimum inter-TTI interval". The TTI is 2 milliseconds. So, for example, Cat 10 can decode 27,952 bits / 2 ms = 13.976 Mbit/s (and not 14.4 Mbit/s as often claimed incorrectly). Categories 1-4 and 11 have inter-TTI intervals of 2 or 3, which reduces the maximum data rate by that factor. Dual-Cell and MIMO 2x2 each multiply the maximum data rate by 2, because multiple independent transport blocks are transmitted over different carriers or spatial streams, respectively. The data rates given in the table are rounded to one decimal point.
Further UE categories were defined from 3GGP Release 7 onwards asEvolved HSPA(HSPA+) and are listed inEvolved HSDPA UE Categories.
As of 28 August 2009[update], 250 HSDPA networks had commercially launchedmobile broadbandservices in 109 countries. 169 HSDPA networks supported 3.6 Mbit/s peak downlink data throughput, and a growing number delivered 21 Mbit/s peak data downlink.[citation needed]
CDMA2000-EVDOnetworks had the early lead on performance. In particular,Japaneseproviders were highly successful benchmarks for this network standard. However, this later changed in favor of HSDPA, as an increasing number of providers worldwide began adopting it.
In 2007, an increasing number of telcos worldwide began sellingHSDPA USB modemsto provide mobile broadband connections. In addition, the popularity of HSDPA landline replacement boxes grew—these provided HSDPA for data viaEthernetandWi-Fi, as well as ports for connecting traditional landline telephones. Some were marketed with connection speeds of "up to 7.2 Mbit/s"[5]under ideal conditions. However, these services could be slower, such as when in fringe coverage indoors.
High-Speed Uplink Packet Access(HSUPA) is a 3G mobile telephonyprotocolin the HSPA family. It is specified and standardized in 3GPP Release 6 to improve the uplink data rate to 5.76 Mbit/s, extend capacity, and reduce latency. Together with additional improvements, this allows for new features such asVoice over Internet Protocol(VoIP), uploading pictures, and sending large e-mail messages.
HSUPA was the second major step in the UMTS evolution process. It has since been superseded by newer technologies with higher transfer rates, such asLTE(150 Mbit/s for downlink and 50 Mbit/s for uplink) andLTE Advanced(maximum downlink rates of over 1 Gbit/s).
HSUPA adds a new transport channel to WCDMA, called the Enhanced Dedicated Channel (E-DCH). It also features several improvements similar to those of HSDPA, including multi-code transmission, shorter transmission time interval enabling fasterlink adaptation, fast scheduling, and fasthybrid automatic repeat request(HARQ) with incremental redundancy, makingretransmissionsmore effective. Similar to HSDPA, HSUPA uses a "packet scheduler", but it operates on a "request-grant" principle where theuser equipment(UE) requests permission to send data and the scheduler decides when and how many UEs will be allowed to do so. A request for transmission contains data about the state of the transmission buffer and the queue at the UE and its available power margin. However, unlike HSDPA, uplink transmissions are notorthogonalto each other.
In addition to this "scheduled" mode of transmission, the standards allow a self-initiated transmission mode from the UEs, denoted "non-scheduled". The non-scheduled mode can, for example, be used for VoIP services for which even the reduced TTI and theNode Bbased scheduler are unable to provide the necessary short delay time and constant bandwidth.
Each MAC-d flow (i.e., QoS flow) is configured to use either scheduled or non-scheduled modes. The UE adjusts the data rate for scheduled and non-scheduled flows independently. The maximum data rate of each non-scheduled flow is configured at call setup, and typically not frequently changed. The power used by the scheduled flows is controlled dynamically by the Node B through absolute grant (consisting of an actual value) and relative grant (consisting of a single up/down bit) messages.
At thephysical layer, HSUPA introduces the following new channels:
The following table shows uplink speeds for the different categories of HSUPA:
Further UE categories were defined from 3GGP Release 7 onwards as Evolved HSPA (HSPA+) and are listed inEvolved HSUPA UE Categories.
Evolved HSPA(also known as HSPA Evolution, HSPA+) is a wireless broadband standard defined in3GPPrelease 7 of the WCDMA specification. It provides extensions to the existing HSPA definitions and is thereforebackward compatibleall the way to the original Release 99 WCDMA network releases. Evolved HSPA provides data rates between 42.2 and 56 Mbit/s in the downlink and 22 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple output (2x2 MIMO) technologies and higher order modulation (64 QAM). With Dual Cell technology, these can be doubled.
Since 2011, HSPA+ has been widely deployed among WCDMA operators, with nearly 200 commitments.[6]
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LTE Advanced, also named or recognized asLTE+,LTE-Aor4G+, is a4Gmobilecellularcommunication standard developed by3GPPas a major enhancement of theLong Term Evolution(LTE) standard.
Three technologies from the LTE-Advanced tool-kit –carrier aggregation, 4x4MIMOand256QAMmodulation in the downlink – if used together and with sufficient aggregated bandwidth, can deliver maximum peak downlink speeds approaching, or even exceeding, 1 Gbit/s. This is significantly more than the peak 300 Mbit/s rate offered by the preceding LTE standard.[1]Later developments have resulted inLTE Advanced Pro(or4.9G) which increases bandwidth even further.[2]
The first ever LTE Advanced network was deployed in 2013 bySK Telecomin South Korea.[3]In August 2019, theGlobal mobile Suppliers Association(GSA) reported that there were 304 commercially launched LTE-Advanced networks in 134 countries. Overall, 335 operators are investing in LTE-Advanced (in the form of tests, trials, deployments or commercial service provision) in 141 countries.[4]
LTE Advanced is also named (indicated as)LTE+,LTE-A,[5]or (onSamsung GalaxyandXiaomismartphones) as4G+. Such networks have also often been described as ‘Gigabit LTEnetworks’ mirroring a term that is also used in the fixed broadband industry.[6]
The mobile communication industry and standards organizations have therefore started work on 4G access technologies, such as LTE Advanced.[when?]At a workshop in April 2008 in China, 3GPP agreed the plans for work on Long Term Evolution (LTE).[7]A first set of specifications were approved in June 2008.[8]Besides the peak data rate 1Gb/sas defined by the ITU-R, it also targets faster switching between power states and improved performance at the cell edge. Detailed proposals are being studied within theworking groups.[when?]The LTE+ format was first proposed byNTT DoCoMoofJapanand has been adopted as the international standard.[9]It was formally submitted as a candidate4GtoITU-Tin late 2009 as meeting the requirements of theIMT-Advancedstandard, and was standardized by the 3rd Generation Partnership Project (3GPP) in March 2011 as 3GPP Release 10.[10]
The work by3GPPto define a4Gcandidate radio interface technology started in Release 9 with the study phase for LTE-Advanced. Being described as a3.9G(beyond 3G but pre-4G), the first release of LTE did not meet the requirements for4G(also calledIMT Advancedas defined by theInternational Telecommunication Union) such as peak data rates up to 1Gb/s. The ITU has invited the submission of candidate Radio Interface Technologies (RITs) following their requirements in a circular letter, 3GPP Technical Report (TR) 36.913, "Requirements for Further Advancements forE-UTRA(LTE-Advanced)."[11]These are based on ITU's requirements for4Gand on operators’ own requirements for advanced LTE.
Major technical considerations include the following:
Likewise, 'WiMAX 2', 802.16m, has been approved by ITU as theIMT Advancedfamily. WiMAX 2 is designed to be backward compatible with WiMAX 1 devices. Most vendors now support conversion of 'pre-4G', pre-advanced versions and some support software upgrades of base station equipment from 3G.
The target of 3GPP LTE Advanced is to reach and surpass theITUrequirements. LTE Advanced should be compatible with first release LTE equipment, and should share frequency bands with first release LTE. In the feasibility study for LTE Advanced,3GPPdetermined that LTE Advanced would meet theITU-Rrequirements for4G. The results of the study are published in3GPPTechnical Report (TR) 36.912.[12]
One of the important LTE Advanced benefits is the ability to take advantage of advanced topology networks; optimized heterogeneous networks with a mix of macrocells with low power nodes such aspicocells,femtocellsand new relay nodes. The next significant performance leap in wireless networks will come from making the most of topology, and brings the network closer to the user by adding many of these low power nodes – LTE Advanced further improves the capacity and coverage, and ensures user fairness. LTE Advanced also introduces multicarrier to be able to use ultra wide bandwidth, up to 100 MHz of spectrum supporting very high data rates.
In the research phase many proposals have been studied as candidates for LTE Advanced (LTE-A) technologies. The proposals could roughly be categorized into:[13]
Within the range of system development, LTE-Advanced and WiMAX 2 can use up to 8x8MIMOand 128-QAMin downlink direction. Example performance: 100 MHz aggregated bandwidth, LTE-Advanced provides almost 3.3 Gbit peak download rates per sector of the base station under ideal conditions. Advanced network architectures combined with distributed and collaborative smart antenna technologies provide several years road map of commercial enhancements.
The3GPPstandards Release 12 added support for 256-QAM.
A summary of a study carried out in 3GPP can be found in TR36.912.[14]
Original standardization work for LTE-Advanced was done as part of 3GPP Release 10, which was frozen in April 2011. Trials were based on pre-release equipment. Major vendors support software upgrades to later versions and ongoing improvements.
In order to improve the quality of service for users in hotspots and on cell edges,heterogeneous networks(HetNets) are formed of a mixture of macro-, pico- and femto base stations serving corresponding-size areas. Frozen in December 2012, 3GPP Release 11[15]concentrates on better support of HetNet. Coordinated Multi-Point operation (CoMP) is a key feature of Release 11 in order to support such network structures. Whereas users located at a cell edge in homogenous networks suffer from decreasing signal strength compounded by neighbor cell interference, CoMP is designed to enable use of a neighboring cell to also transmit the same signal as the serving cell, enhancing quality of service on the perimeter of a serving cell. In-device Co-existence (IDC) is another topic addressed in Release 11. IDC features are designed to ameliorate disturbances within the user equipment caused between LTE/LTE-A and the various other radio subsystems such as WiFi, Bluetooth, and the GPS receiver. Further enhancements for MIMO such as 4x4 configuration for the uplink were standardized.
The higher number of cells in HetNet results in user equipment changing the serving cell more frequently when in motion.
The ongoing work on LTE-Advanced[16]in Release 12, amongst other areas, concentrates on addressing issues that come about when users move through HetNet, such as frequent hand-overs between cells. It also included use of 256-QAM.
This list covers technology demonstrations and field trials up to the year 2014, paving the way for a wider commercial deployment of the VoLTE technology worldwide. From 2014 onwards various further operators trialled and demonstrated the technology for future deployment on their respective networks. These are not covered here. Instead a coverage of commercial deployments can be found in the section below.
LTE Advanced Pro(LTE-A Pro, also known as4.5G,4.5G Pro,4.9G,Pre-5G,5G Project)[45][46][47][48]is a name for3GPPrelease 13 and 14.[49][50]It is an evolution of LTE Advanced (LTE-A) cellular standard supporting data rates in excess of 3 Gbit/s using 32-carrier aggregation.[2]It also introduces the concept ofLicense Assisted Access, which allows sharing of licensed and unlicensed spectrum.
Additionally, it incorporates several new technologies associated with5G, such as 256-QAM, MassiveMIMO,LTE-UnlicensedandLTE IoT,[51][52]that facilitated early migration of existing networks to enhancements promised with the full 5G standard.[53]
Telstrain Australia deployed the very first LTE Advanced Pro network in January 2017.[54]
LTE for UMTS - OFDMA and SC-FDMA Based Radio Access,ISBN978-0-470-99401-6Chapter 2.6: LTE Advanced for IMT-advanced, pp. 19–21.
Resources (white papers, technical papers, application notes)
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Intelecommunications, the(digital) cliff effectorbrick-wall effectis a sudden loss ofdigitalsignal reception. Unlikeanalog signals, which gradually fade whensignal strengthdecreases orelectromagnetic interferenceormultipathincreases, a digital signal provides data which is either perfect or non-existent at thereceivingend. It is named for a graph of reception quality versus signal quality, where the digital signal "falls off a cliff" instead of having a gradual rolloff.[1]This is an example of anEXIT chart.
The phenomenon is primarily seen in broadcasting, where signal strength is liable to vary, rather than in recorded media, which generally have a good signal. However, it may be seen in significantly damaged media that is at the edge of readability.
This effect can most easily be seen ondigital television, including bothsatellite TVand over-the-airterrestrial TV. Whileforward error correctionis applied to thebroadcast, when a minimum threshold of signal quality (a maximumbit error rate) is reached it is no longer enough for thedecoderto recover. The picture may break up (macroblocking), lock on afreeze frame, or go blank. Causes includerain fadeorsolar transiton satellites, andtemperature inversionsand other weather or atmospheric conditions causinganomalous propagationon the ground.
Three particular issues particularly manifest the cliff effect. Firstly, anomalous conditions will cause occasional signal degradation. Secondly, if one is located in a fringe area, where the antenna is just barely strong enough to receive the signal, then usual variation in signal quality will cause relatively frequent signal degradation, and a very small change in overall signal quality can have a dramatic impact on the frequency of signal degradation – one incident per hour (not significantly affecting watchability) versus problems every few seconds or continuous problems. Thirdly, in some cases, where the signal is beyond the cliff (in unwatchable territory), viewers who were once able to receive a degraded signal from analog stations will findafter digital transitionthat there is no available signal in rural, fringe or mountainous regions.[2]
The cliff effect is a particularly serious issue formobile TV, as signal quality may vary significantly, particularly if the receiver is moving rapidly, as in a car.
Hierarchical modulationand coding can provide a compromise by supporting two or more streams with different robustness parameters and allowing receivers to scale back to a lower definition (usually fromHDTVtoSDTV, or possibly from SDTV toLDTV) before dropping out completely. Two-level hierarchical modulation is supported in principle by the EuropeanDVB-Tdigital terrestrial television standard.[3]However, layeredsource coding, such as provided byScalable Video Coding, is not supported.
HD Radiobroadcasting, officially used only in the United States, is one system designed to have an analogfallback. Receivers are designed to immediately switch to the analog signal upon losing a lock on digital, but only as long as the tuned station operates inhybriddigital mode (the official meaning of "HD"). In the future all-digital mode, there is no analog to fall back to at the edge of the digital cliff. This applies only to the main channelsimulcast, and not to anysubchannels, because they have nothing to fall back to. It is also important for the station'sbroadcast engineerto make sure that theaudio signalissynchronizedbetween analog and digital, or the cliff effect will still cause a jump slightly forward or backward in the radio program.
The cliff effect is also heard onmobile phones, where one or both sides of the conversation may break up, possibly resulting in adropped call. Other forms ofdigital radioalso suffer from this.
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Adropoutis a momentary loss ofsignalin acommunications system, usually caused bynoise,propagationanomalies, or system malfunctions. Foranalog signals, a dropout is frequently gradual and partial, depending on thecause. Fordigital signals, dropouts are more pronounced, usually being sudden and complete, due to thecliff effect. Inmobile telephony, a dropout of more than a fewsecondswill result in adropped call.
This article related totelecommunicationsis astub. You can help Wikipedia byexpanding it.
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https://en.wikipedia.org/wiki/Dropout_(communications)
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LoRa(from "LongRange", sometimes abbreviated as "LR") is a physical proprietaryradio communicationtechnique.[2]It is based onspread spectrummodulation techniques derived fromchirp spread spectrum(CSS) technology.[3]It was developed by Cycleo, a company ofGrenoble, France, and patented in 2014.[4]In March 2012, Cycleo was acquired by the US companySemtech.[5]
LoRaWAN(Long RangeWide Area Network) defines the communication protocol and system architecture. LoRaWAN is an official standard of theInternational Telecommunication Union(ITU), ITU-T Y.4480.[6]The continued development of the LoRaWAN protocol is managed by the open, non-profit LoRa Alliance, of which Semtech is a founding member.
Together, LoRa and LoRaWAN define alow-power, wide-area(LPWA) networking protocol designed to wirelessly connect battery operated devices to the Internet in regional, national or global networks, and targets keyInternet of things(IoT) requirements, such asbi-directional communication, end-to-end security, mobility and localization services. Thelow power, low bit rate, and IoT use distinguish this type of network from awireless WANthat is designed to connect users or businesses, and carry more data, using more power. The LoRaWAN data rate ranges from 0.3 kbit/s to 50 kbit/s per
channel.[7]
LoRa uses license-free sub-gigahertzradio frequencybands EU433 (LPD433) or EU868 (863–870/873 MHz) inEurope; AU915/AS923-1 (915–928 MHz) inSouth America; US915 (902–928 MHz) inNorth America; IN865 (865–867 MHz) inIndia; and AS923 (915–928 MHz) inAsia;[8]LoRa enables long-range transmissions with low power consumption.[9]The technology covers thephysical layer, while other technologies and protocols such as LoRaWAN cover the upper layers. It can achieve data rates between 0.3 kbit/s and 27 kbit/s, depending upon thespreading factor.[10]
LoRa is one of the most popular low-powerwireless sensor networktechnologies for the implementation of theInternet of Things, offering long-range communication compared to technologies such asZigbeeorBluetooth, but with lower data rates.[11]
LoRa devices havegeolocationcapabilities used fortrilateratingpositions of devices via timestamps from gateways.[12]
LoRa uses a proprietary spread spectrum modulation that is similar to and a derivative ofchirp spread spectrum(CSS) modulation. Each symbol is represented by a cyclic shifted chirp over the bandwidth centered around the base frequency. The spreading factor (SF) is a selectable radio parameter from 5 to 12[13]and represents the number of bits sent per symbol and in addition determines how much the information is spread over time.[3]There areM=2SF{\displaystyle M=2^{\mathrm {SF} }}different initial frequencies of the cyclic shifted chirp across the bandwidth around the center frequency.[14]The symbol rate is determined byRs=B/M{\displaystyle R_{s}=B/M}. LoRa can tradeoff data rate for sensitivity (assuming a fixed channel bandwidthB{\displaystyle B}) by selecting the SF, i.e. the amount of spread used. A lower SF corresponds to a higher data rate but a worse sensitivity, a higher SF implies a better sensitivity but a lower data rate.[15]Compared to lower SF, sending the same amount of data with higher SF needs more transmission time, known as time-on-air. More time-on-air means that the modem is transmitting for a longer time and consuming more energy. Typical LoRa modems support transmit powers up to +22 dBm.[13]However, the regulations of the respective country may additionally limit the allowed transmit power. Higher transmit power results in higher signal power at the receiver and hence a higherlink budget, but at the cost of consuming more energy. There are measurement studies of LoRa performance with regard to energy consumption, communication distances, and medium access efficiency.[16]According to the LoRa Development Portal, the range provided by LoRa can be up to 3 miles (4.8 km) in urban areas, and up to 10 miles (16 km) or more in rural areas (line of sight).[17]
In addition, LoRa usesforward error correction codingto improve resilience against interference. LoRa's high range is characterized by high wirelesslink budgetsof around 155 dB to 170 dB.[18]Range extenders for LoRa are called LoRaX.
Since LoRa defines the lower, physical, layer, the upper networking layers were lacking. The specification consist of two parts. The actual LoRaWAN acts as a cloud controlledMAClayer protocol for managing communication betweenLPWANgatewaysand end-node devices. For communication within the cloud, LoRaWAN specifies data formats for higher layers, while the transport protocol could be any Internet protocol.
LoRaWAN defines the communication protocol and system architecture for the network, while LoRa's physical layer enables the long-range communication link. LoRaWAN is also responsible for managing the communication frequencies,data rate, and power for all devices.[19]Devices in the network are asynchronous and transmit when they have data available to send. Data transmitted by an end-node device is received by multiple gateways. Each gateway has a multi-channel receiver, while the end-devices can hop between the channels using a single channel transceiver. Gateways forward the data packets without further processing to a centralized network server.[20]This technology shows high reliability for the moderate load, however, it has some performance issues with sending acknowledgements (2016).[21]
The data is then further forwarded to an associated application server.[22][23]The cloud back-end interface definition uses JSON as data format. The cloud network specifies secure joining protocols for end-devices and possibilities for roaming between gateways. The application data payload is encrypted between the end-device and the cloud application and the content format is not specified by LoRaWAN.
In the wireless communication, particularly across the IoT applications, collision avoidance is essential for reliable communication and overall spectral efficiency. Previously, LoRaWAN has relied uponALOHAas themedium access control(MAC) layer protocol, but to improve this, the LoRa Alliance's Technical Recommendation TR013[24]introducedCSMA-CA, which does not debilitate LoRa's distinctive modulation advantages such as Spreading Factor orthogonality,[16]and the capability for belownoise-floorcommunication.[16]Employing the CAD based CSMA technique specified in TR013[24]overcomes the limitations of relying onReceived Signal Strength(RSS)-based sensing, which is unable to maintain the two said advantages of LoRa modulation. Therefore, implementing TR013 enhances LoRaWAN's spectrum efficiency and ensures more reliable device communication, including in congested environments.[24]TR013 is based on the LMAC[25]and is the first industry-academia collaboration of LoRa Alliance to have resulted in a Technical Recommendation.[26][27]
The LoRa Alliance is an open, non-profit association whose stated mission is to support and promote the global adoption of the LoRaWAN standard for massively scaled IoT deployments, as well as deployments in remote or hard-to-reach locations.
Members collaborate in a vibrant ecosystem of device makers, solution providers, system integrators and network operators, delivering interoperability needed to scale IoT across the globe, using public, private, hybrid, and community networks. Key areas of focus within the Alliance are Smart Agriculture, Smart Buildings, Smart Cities, Smart Industry, Smart Logistics, and Smart Utilities.
Key contributing members of the LoRa Alliance include Actility,Amazon Web Services,Cisco, Everynet,Helium, Kerlink, MachineQ, aComcastCompany,Microsoft,MikroTik, Minol Zenner, Netze BW, Semtech, Senet,STMicroelectronics, TEKTELIC and The Things Industries.[35]In 2018, the LoRa Alliance had over 100 LoRaWAN network operators in over 100 countries; in 2023, there are nearly 200, providing coverage in nearly every country in the world.[36]
On October 1, 2024,Ciscoannounced it is "exiting the LoRaWAN space" with no planned migration for Cisco LoRaWAN gateways.[37]
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Wi-Fi(/ˈwaɪfaɪ/)[1][a]is a family ofwireless networkprotocols based on theIEEE 802.11family of standards, which are commonly used forlocal area networkingof devices andInternetaccess, allowing nearby digital devices to exchange data byradio waves. These are the most widely used computer networks, used globally inhome and small office networksto link devices and to provideInternet accesswithwireless routersandwireless access pointsin public places such as coffee shops, restaurants, hotels, libraries, and airports.
Wi-Fiis a trademark of theWi-Fi Alliance, which restricts the use of the term "Wi-Fi Certified" to products that successfully completeinteroperabilitycertification testing.[3][4][5]Non-compliant hardware is simply referred to asWLAN, and it may or may not work with "Wi-Fi Certified" devices. As of 2017,[update]the Wi-Fi Alliance consisted of more than 800 companies from around the world.[6]As of 2019,[update]over 3.05 billion Wi-Fi-enabled devices are shipped globally each year.[7]
Wi-Fi uses multiple parts of theIEEE 802protocolfamily and is designed to work well with its wired sibling,Ethernet. Compatible devices can network throughwireless access pointswith each other as well as with wired devices and the Internet. Different versions of Wi-Fi are specified by variousIEEE 802.11protocol standards, with different radio technologies determining radio bands, maximum ranges, and speeds that may be achieved. Wi-Fi most commonly uses the 2.4 gigahertz (120 mm)UHFand 5 gigahertz (60 mm)SHFradio bands, with the 6 gigahertz SHF band used in newer generations of the standard; these bands are subdivided into multiple channels. Channels can be shared between networks, but, within range, only one transmitter can transmit on a channel at a time.
Wi-Fi's radio bands work best forline-of-sightuse. Common obstructions, such as walls, pillars, home appliances, etc., may greatly reduce range, but this also helps minimize interference between different networks in crowded environments. The range of an access point is about 20 m (66 ft) indoors, while some access points claim up to a 150 m (490 ft) range outdoors. Hotspot coverage can be as small as a single room with walls that block radio waves or as large as many square kilometers using multiple overlapping access points withroamingpermitted between them. Over time, the speed andspectral efficiencyof Wi-Fi has increased. As of 2019,[update]some versions of Wi-Fi, running on suitable hardware at close range, can achieve speeds of 9.6 Gbit/s (gigabitper second).[8]
A 1985 ruling by the U.S. Federal Communications Commission released parts of theISM bandsfor unlicensed use for communications.[9]These frequency bands include the same 2.4 GHz bands used by equipment such asmicrowave ovens, and are thus subject to interference.[10]
In 1991 inNieuwegein, theNCR CorporationandAT&Tinvented the precursor to 802.11,[11]intended for use in cashier systems, under the nameWaveLAN. NCR'sVic Hayes, who held the chair of IEEE 802.11 for ten years, along withBell Labsengineer Bruce Tuch, approached theInstitute of Electrical and Electronics Engineers(IEEE) to create a standard and were involved in designing the initial 802.11b and 802.11a specifications within the IEEE.[12]They have both been subsequently inducted into the Wi-Fi NOW Hall of Fame.[13]
In 1989 in Australia, a team of scientists began working on wireless LAN technology.[14]A prototypetest bedfor awireless local area network(WLAN) was developed in 1992 by a team of researchers from the Radiophysics Division of theCSIRO(Commonwealth Scientific and Industrial Research Organisation) in Australia, led byJohn O'Sullivan.[15]A patent for Wi Fi was lodged by the CSIRO in 1992.[16]
The first version of the 802.11 protocol was released in 1997, and provided up to 2 Mbit/s link speeds. This was updated in 1999 with802.11bto permit 11 Mbit/s link speeds.
In 1999, theWi-Fi Allianceformed as a trade association to hold the Wi-Fi trademark under which most IEEE 802.11 products are sold.[17]
The major commercial breakthrough came withApple Inc.adopting Wi-Fi for theiriBookseries of laptops in 1999.[11]It was the first mass consumer product to offer Wi-Fi network connectivity, which was then branded by Apple asAirPort.[18]This was in collaboration with the same group that helped create the standard:Vic Hayes, Bruce Tuch,Cees Links, Rich McGinn, and others fromLucent.[19][20]
In 2000, Radiata, a group of Australian scientists connected to the CSIRO, were the first to use the 802.11a standard on chips connected to a Wi-Fi network.[16]
Wi-Fi uses a large number ofpatentsheld by multiple different organizations.[21]Australia,[22]the United States[23]and the Netherlands[24]simultaneously claim the invention of Wi-Fi, and a consensus has not been reached globally.[25][26]In 2009, the AustralianCSIROwas awarded $200 million after a patent settlement with 14 technology companies, with a further $220 million awarded in 2012 after legal proceedings with 23 companies.[27][28][29]
In 2016, the CSIRO's WLAN prototype test bed was chosen as Australia's contribution to the exhibitionA History of the World in 100 Objectsheld in theNational Museum of Australia.[15]
The nameWi-Fi, commercially used at least as early as August 1999,[30]was coined by the brand-consulting firm Interbrand. The Wi-Fi Alliance had hired Interbrand to create a name that was "a little catchier than 'IEEE 802.11b Direct Sequence'."[31][32]According to Phil Belanger, a founding member of the Wi-Fi Alliance, the termWi-Fiwas chosen from a list of ten names that Interbrand proposed.[31]Interbrand also created the Wi-Filogo. Theyin-yangWi-Fi logo indicates the certification of a product forinteroperability.[33]The name is often written asWiFi,Wifi, orwifi, but these are not approved by the Wi-Fi Alliance.
The nameWi-Fiisnotshort-form for 'Wireless Fidelity',[34]although the Wi-Fi Alliance did use theadvertising slogan"The Standard for Wireless Fidelity" for a short time after the brand name was created,[31][33][35]and the Wi-Fi Alliance was also called the "Wireless Fidelity Alliance Inc." in some publications.[36]IEEEis a separate, but related, organization and their website has stated "WiFi is a short name for Wireless Fidelity".[37][38]The nameWi-Fiwas partly chosen because it sounds similar toHi-Fi, which consumers take to meanhigh fidelityorhigh quality. Interbrand hoped consumers would find the name catchy, and that they would assume thiswirelessprotocol has high fidelity because of its name.[39]
Other technologies intended for fixed points, includingMotorola Canopy, are usually calledfixed wireless. Alternative wireless technologies includeZigbee,Z-Wave,Bluetoothandmobile phone standards.
To connect to a Wi-Fi LAN, a computer must be equipped with awireless network interface controller. The combination of a computer and an interface controller is called astation. Stations are identified by one or moreMAC addresses.
Wi-Fi nodes often operate in infrastructure mode in which all communications go through a base station.Ad hoc moderefers to devices communicating directly with each other, without communicating with an access point.
Aservice setis the set of all the devices associated with a particular Wi-Fi network. Devices in a service set need not be on the same wavebands or channels. A service set can be local, independent, extended, mesh, or a combination. Each service set has an associated identifier, a 32-byte service set identifier (SSID), which identifies the network. TheSSIDis configured within the devices that are part of the network. A basic service set (BSS) is a group of stations that share the same wireless channel, SSID, and other settings that have wirelessly connected, usually to the same access point.[40]: 3.6Each BSS is identified by a MAC address called theBSSID.
TheIEEEdoes not test equipment for compliance with their standards. TheWi-Fi Alliancewas formed in 1999 to establish and enforce standards for interoperability andbackward compatibility, and to promotewirelesslocal-area-network technology. The Wi-Fi Alliance enforces the use of the Wi-Fi brand to technologies based on theIEEE 802.11standards from the IEEE. Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, gain the right to mark those products with the Wi-Fi logo. Specifically, the certification process requires conformance to the IEEE 802.11 radio standards, theWPA and WPA2security standards, and theEAPauthentication standard. Certification may optionally include tests of IEEE 802.11 draft standards, interaction with cellular-phone technology in converged devices, and features relating to security set-up, multimedia, and power-saving.[41]
Not every Wi-Fi device is submitted for certification. The lack of Wi-Fi certification does not necessarily imply that a device is incompatible with other Wi-Fi devices.[42]The Wi-Fi Alliance may or may not sanction derivative terms, such asSuper Wi-Fi,[43]coined by the USFederal Communications Commission(FCC) to describe proposed networking in the UHF TV band in the US.[44]
Equipment frequently supports multiple versions of Wi-Fi. To communicate, devices must use a common Wi-Fi version. The versions differ between the radio wavebands they operate on, the radio bandwidth they occupy, the maximum data rates they can support and other details. Some versions permit the use of multiple antennas, which permits greater speeds as well as reduced interference.
Historically, the equipment listed the versions of Wi-Fi supported using the name of the IEEE standards. In 2018, theWi-Fi Allianceintroduced simplified Wi-Fi generational numbering to indicate equipment that supports Wi-Fi 4 (802.11n), Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax). These generations have a high degree of backward compatibility with previous versions. The alliance has stated that the generational level 4, 5, or 6 can be indicated in the user interface when connected, along with the signal strength.[48][49]
The most important standards affecting Wi‑Fi are: 802.11a, 802.11b, 802.11g, 802.11n (Wi-Fi 4), 802.11h, 802.11i, 802.11-2007, 802.11–2012, 802.11ac (Wi-Fi 5),[49]802.11ad, 802.11af, 802.11-2016, 802.11ah, 802.11ai, 802.11aj,802.11aq, 802.11ax (Wi-Fi 6),[49]802.11ay.
Wi-Fi technology may be used to provide local network andInternet accessto devices that are within Wi-Fi range of one or more routers that are connected to the Internet. The coverage of one or more interconnected access points can extend from an area as small as a few rooms to as large as many square kilometres. Coverage in the larger area may require a group of access points with overlapping coverage. For example, public outdoor Wi-Fi technology has been used successfully inwireless mesh networksin London. An international example isFon.
Wi-Fi provides services in private homes, businesses, as well as in public spaces.Wi-Fi hotspotsmay be set up either free of charge or commercially, often using acaptive portalwebpage for access. Organizations, enthusiasts, authorities andbusinesses, such as airports, hotels, and restaurants, often provide free or paid-use hotspots to attract customers, to provide services to promote business in selected areas.Routersoften incorporate adigital subscriber linemodem or acable modemand a Wi-Fi access point, are frequently set up in homes and other buildings, to provide Internet access for the structure.
Similarly, battery-powered routers may include amobile broadband modemand a Wi-Fi access point. When subscribed to a cellular data carrier, they allow nearby Wi-Fi stations to access the Internet. A number of smartphones have a built-inmobile hotspotcapability of this sort, though carriers often disable the feature, or charge a separate fee to enable it. Standalone devices such asMiFi- andWiBro-branded devices provide the capability. Some laptops that have a cellular modem card can also act as mobile Internet Wi-Fi access points.
Multiple traditional university campuses in the developed world provide at least partial Wi-Fi coverage.Carnegie Mellon Universitybuilt the first campus-wide wireless Internet network, calledWireless Andrew, at itsPittsburghcampus in 1993 before Wi-Fi branding existed.[50][51][52]A number of universities collaborate in providing Wi-Fi access to students and staff through theEduroaminternational authentication infrastructure.
In the early 2000s, multiple cities around the world announced plans to construct citywide Wi-Fi networks. There are a number of successful examples; in 2004,Mysore(Mysuru) became India's first Wi-Fi-enabled city. A company called WiFiyNet has set up hotspots in Mysore, covering the whole city and a few nearby villages.[53]
In 2005,St. Cloud, FloridaandSunnyvale, California, became the first cities in the United States to offer citywide free Wi-Fi (fromMetroFi).[54]Minneapolishas generated $1.2 million in profit annually forits provider.[55]
In May 2010, the thenLondonmayorBoris Johnsonpledged to have London-wide Wi-Fi by 2012.[56]SeveralboroughsincludingWestminsterandIslington[57][58]already had extensive outdoor Wi-Fi coverage at that point.
New York Cityannounced a city-wide campaign to convert oldphone boothsintodigital kiosksin 2014. The project, titledLinkNYC, has created a network of kiosks that serve as public Wi-Fi hotspots, high-definition screens andlandlines. Installation of the screens began in late 2015. The city government plans to implement more than seven thousand kiosks over time, eventually making LinkNYC the largest and fastest public, government-operated Wi-Fi network in the world.[59][60][61][62][63]TheUKhas planned a similar project across major cities of the country, with the project's first implementation in theLondon Borough of Camden.[64]
Officials in South Korea's capitalSeoulwere moving to provide free Internet access at more than 10,000 locations around the city, including outdoor public spaces, major streets, and densely populated residential areas. Seoul was planning to grant leases to KT,LGTelecom, and SK Telecom. The companies were supposed to invest $44 million in the project, which was to be completed in 2015.[65][needs update]
Wi-Fi positioning systemsuse known positions of Wi-Fi hotspots to identify a device's location.[66][67][68]It is used whenGPSisn't suitable due to issues like signal interference or slow satellite acquisition.[69]This includes assistedGPS, urban hotspot databases, and indoor positioning systems.[70]Wi-Fi positioning relies on measuring signal strength (RSSI) and fingerprinting.[71][72][73][74]Parameters likeSSIDand MAC address are crucial for identifying access points. The accuracy depends on nearby access points in the database. Signal fluctuations can cause errors, which can be reduced with noise-filtering techniques. For low precision, integrating Wi-Fi data with geographical and time information has been proposed.[75][76]
TheWi-Fi RTTcapability introduced inIEEE 802.11mcallows for positioning based on round trip time measurement, an improvement over the RSSI method.[77]TheIEEE 802.11azstandard promises further improvements in geolocation accuracy.[78][79]
Wi-Fi sensingis used in applications such asmotion detectionandgesture recognition.[80]
Wi-Fi stations communicate by sending each otherdata packets, blocks of data individually sent and delivered over radio on various channels. As with all radio, this is done by themodulation and demodulationofcarrier waves. Different versions of Wi-Fi use different techniques, 802.11b usesdirect-sequence spread spectrumon a single carrier, whereas 802.11a, Wi-Fi 4, 5 and 6 useorthogonal frequency-division multiplexing.[81][82]
Channels are usedhalf duplex[83][84]and can betime-sharedby multiple networks. Any packet sent by one computer is locally received by stations tuned to that channel, even if that information is intended for just one destination.[e]Stations typically ignore information not addressed to them.[f]The use of the same channel also means that the data bandwidth is shared, so for example, available throughput to each device is halved when two stations are actively transmitting.
As with other IEEE 802 LANs, stations come programmed with a globally unique 48-bit MAC address.[g]The MAC addresses are used to specify both the destination and the source of each data packet. On the reception of a transmission, the receiver uses the destination address to determine whether the transmission is relevant to the station or should be ignored.
A scheme known ascarrier-sense multiple access with collision avoidance(CSMA/CA) governs the way stations share channels. With CSMA/CA stations attempt to avoid collisions by beginning transmission only after the channel is sensed to be idle,[85][86]but then transmit their packet data in its entirety. CSMA/CA cannot completely prevent collisions, as two stations may sense the channel to be idle at the same time and thus begin transmission simultaneously. A collision happens when a station receives signals from multiple stations on a channel at the same time. This corrupts the transmitted data and can require stations to re-transmit. The lost data and re-transmission reduces throughput, in some cases severely.
The 802.11 standard provides several distinctradio frequencyranges for use in Wi-Fi communications: 900MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 6 GHz and 60 GHzbands.[87][88][89]Each range is divided into a multitude ofchannels. In the standards, channels are numbered at 5 MHz spacing within a band (except in the 60 GHz band, where they are 2.16 GHz apart), and the number refers to the centre frequency of the channel. Although channels are numbered at 5 MHz spacing, transmitters generally occupy at least 20 MHz, and standards allow for neighbouring channels to be bonded together to form a wider channel for higher throughput.
Countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. 802.11b/g/n can use the 2.4 GHz band, operating in the United States under FCCPart 15rules and regulations. In this frequency band, equipment may occasionally sufferinterferencefrom microwave ovens,[10]cordless telephones,USB 3.0hubs,[90]Bluetoothand other devices.[91]
Spectrum assignments and operational limitations are not consistent worldwide: Australia and Europe allow for an additional two channels (12, 13) beyond the 11 permitted in the United States for the 2.4 GHz band, while Japan has three more (12–14).
802.11a/h/j/n/ac/ax can use the5 GHz U-NII band, which, for much of the world, offers at least 23 non-overlapping 20 MHz channels. This is in contrast to the 2.4 GHz frequency band where the channels are only 5 MHz wide. In general, lower frequencies have longer range but have less capacity. The 5 GHz bands are absorbed to a greater degree by common building materials than the 2.4 GHz bands and usually give a shorter range.
As 802.11 specifications evolved to support higher throughput, the protocols have become much more efficient in their bandwidth use. Additionally, they have gained the ability toaggregatechannels together to gain still more throughput where the bandwidth for additional channels is available. 802.11n allows for double radio spectrum bandwidth (40 MHz) per channel compared to802.11aor 802.11g (20 MHz). 802.11n can be set to limit itself to 20 MHz bandwidth to prevent interference in dense communities.[92]In the 5 GHz band, 20 MHz, 40 MHz, 80 MHz, and 160 MHz channels are permitted with some restrictions, giving much faster connections.
Wi-Fi is part of the IEEE 802 protocol family. The data is organized into802.11 framesthat are very similar toEthernet framesat the data link layer, but with extra address fields. MAC addresses are used asnetwork addressesfor routing over the LAN.[93]
Wi-Fi's MAC andphysical layer(PHY) specifications are defined by IEEE 802.11 for modulating and receiving one or more carrier waves to transmit the data in the infrared, and 2.4,3.6, 5, 6, or60 GHzfrequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base version of the standard was released in 1997 and has had many subsequent amendments. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand. While each amendment is officially revoked when incorporated in the latest version of the standard, the corporate world tends to market to the revisions because they concisely denote capabilities of their products.[94]As a result, in the market place, each revision tends to become its own standard.
In addition to 802.11, the IEEE 802 protocol family has specific provisions for Wi-Fi. These are required because Ethernet's cable-based media are not usually shared, whereas with wireless all transmissions are received by all stations within the range that employ that radio channel. While Ethernet has essentially negligible error rates, wireless communication media are subject to significant interference. Therefore, the accurate transmission is not guaranteed so delivery is, therefore, abest-effort deliverymechanism. Because of this, for Wi-Fi, theLogical Link Control(LLC) specified byIEEE 802.2employs Wi-Fi'smedia access control(MAC) protocols to manage retries without relying on higher levels of the protocol stack.[95]
For internetworking purposes, Wi-Fi is usuallylayeredas alink layer[h]below theinternet layerof theInternet Protocol. This means that nodes have an associatedinternet addressand, with suitable connectivity, this allows full Internet access.
In infrastructure mode, which is the most common mode used, all communications go through a base station. For communications within the network, this introduces an extra use of the airwaves but has the advantage that any two stations that can communicate with the base station can also communicate through the base station, which limits issues associated with thehidden node problemand simplifies the protocols.
Wi-Fi also allows communications directly from one computer to another without an access point intermediary. This is calledad hocWi-Fi transmission. Different types of ad hoc networks exist. In the simplest case, network nodes must talk directly to each other. In more complex protocols nodes may forward packets, and nodes keep track of how to reach other nodes, even if they move around.
Ad hoc mode was first described byChai Keong Tohin his 1996 patent of wireless ad hoc routing,[96]implemented on Lucent WaveLAN 802.11a wireless on IBMThinkPadsover a size nodes scenario spanning a region of over a mile. The success was recorded inMobile Computingmagazine (1999)[97]and later published formally inIEEE Transactions on Wireless Communications, 2002[98]andACM SIGMETRICS Performance Evaluation Review, 2001.[99]
This wireless ad hoc network mode has proven popular withmultiplayer video gamesonhandheld game consoles, such as theNintendo DSandPlayStation Portable. It is also popular ondigital cameras, and otherconsumer electronics devices. Some devices can also share their Internet connection using ad hoc, becoming hotspots orvirtual routers.[100]
Similarly, the Wi-Fi Alliance promotes the specificationWi-Fi Directfor file transfers and media sharing through a new discovery and security methodology.[101]Wi-Fi Direct launched in October 2010.[102]
Another mode of direct communication over Wi-Fi isTunneled Direct Link Setup(TDLS), which enables two devices on the same Wi-Fi network to communicate directly, instead of via the access point.[103]
AnExtended Service Setmay be formed by deploying multiple access points that are configured with the same SSID and security settings. Wi-Fi client devices typically connect to the access point that can provide the strongest signal within that service set.[104]
Increasing the number of Wi-Fi access points for a network providesredundancy, better range, support for fasthandover, and increased overall network capacity by using more channels or by defining smallercells. Except for the smallest implementations (such as home or small office networks), Wi-Fi implementations have moved towardthinaccess points, with more of thenetwork intelligencehoused in a centralized network appliance, relegating individual access points to the role of dumb transceivers. Outdoor applications may usemeshtopologies.[105]
Wi-Fi operational range depends on factors such as the frequency band, modulation technique,transmitter power output, receiver sensitivity, antenna gain and type, and propagation and interference characteristics in the environment. At longer distances, speed is typically reduced.
Compared to cell phones and similar technology, Wi-Fi transmitters are low-power devices. In general, the maximum amount of power that a Wi-Fi device can transmit is limited by local regulations, such asFCC Part 15in the US.Equivalent isotropically radiated power(EIRP) in theEuropean Unionis limited to 20dBm(100 mW).
Wi-Fi, however, has higher power compared to some other standards designed to supportwireless personal area networkapplications. For example, Bluetooth provides a much shorterpropagationrange between 1 and 100 metres (1 and 100 yards)[106]and so in general has a lower power consumption. Other low-power technologies such asZigbeehave fairly long range, but much lower data rate. The high power consumption of Wi-Fi makes battery life in some mobile devices a concern.
An access point compliant with either802.11bor 802.11g, using the stockomnidirectional antennamight have a range of 0.1 km. The same radio with an external semi-parabolic antenna (15 dB gain) with a similarly equipped receiver at the far end might have a range over 32 km.
Higher gain rating (dBi) indicates further deviation (generally toward the horizontal) from a theoretical, perfectisotropic radiator, and therefore the antenna can project or accept a usable signal further in particular directions, as compared to a similar output power on a more isotropic antenna.[107]For example, an 8 dBi antenna used with a 100 mW driver has a similar horizontal range to a 6 dBi antenna being driven at 500 mW. This assumes that radiation in the vertical is lost; this may not be the case in some situations, especially in large buildings or within awaveguide. In the above example, a directional waveguide could cause the low-power 6 dBi antenna to project much further in a single direction than the 8 dBi antenna, which is not in a waveguide, even if they are both driven at 100 mW.
On wireless routers with detachable antennas, it is possible to improve range by fitting upgraded antennas that provide a higher gain in particular directions. Outdoor ranges can be improved to many kilometres through the use of high gaindirectional antennasat the router and remote device(s).
Wi-Fi 4 and higher standards allow devices to have multiple antennas on transmitters and receivers. Multiple antennas enable the equipment to exploitmultipath propagationon the same frequency bands giving much higher speeds and longer range.
Wi-Fi 4 can more than double the range over previous standards.[108]
The Wi-Fi 5 standard uses the 5 GHz band exclusively, and is capable of multi-station WLAN throughput of at least 1 gigabit per second, and a single station throughput of at least 500 Mbit/s. As of the first quarter of 2016, The Wi-Fi Alliance certifies devices compliant with the 802.11ac standard as "Wi-Fi CERTIFIED ac". This standard uses several signal processing techniques such as multi-user MIMO and 4X4 Spatial Multiplexing streams, and wide channel bandwidth (160 MHz) to achieve its gigabit throughput. According to a study by IHS Technology, 70% of all access point sales revenue in the first quarter of 2016 came from 802.11ac devices.[109]
With Wi-Fi signalsline-of-sightusually works best, but signals can transmit, absorb, reflect,refract,diffractandup and down fadethrough and around structures, both man-made and natural. Wi-Fi signals are very strongly affected by metallic structures (includingrebarin concrete,low-e coatingsin glazing), rock structures (includingmarble) and water (such as found in vegetation).
Due to the complex nature of radio propagation at typical Wi-Fi frequencies, particularly around trees and buildings, algorithms can only approximately predict Wi-Fi signal strength for any given area in relation to a transmitter.[110]This effect does not apply equally tolong-range Wi-Fi, since longer links typically operate from towers that transmit above the surrounding foliage.
Mobile use of Wi-Fi over wider ranges is limited, for instance, to uses such as in an automobile moving from one hotspot to another. Other wireless technologies are more suitable for communicating with moving vehicles.
Distance records (using non-standard devices) include 382 km (237 mi) in June 2007, held by Ermanno Pietrosemoli and EsLaRed of Venezuela, transferring about 3 MB of data between the mountain-tops ofEl Águilaand Platillon.[111][112]TheSwedish National Space Agencytransferred data 420 km (260 mi), using 6 watt amplifiers to reach an overheadstratospheric balloon.[113]
Wi-Fi connections can be blocked or the Internet speed lowered by having other devices in the same area. Wi-Fi protocols are designed to share the wavebands reasonably fairly, and this often works with little to no disruption. To minimize collisions with Wi-Fi and non-Wi-Fi devices, Wi-Fi employsCarrier-sense multiple access with collision avoidance(CSMA/CA), where transmitters listen before transmitting and delay transmission of packets if they detect that other devices are active on the channel, or if noise is detected from adjacent channels or non-Wi-Fi sources. Nevertheless, Wi-Fi networks are still susceptible to thehidden nodeandexposed node problem.[114]
A standard speed Wi-Fi signal occupies five channels in the 2.4 GHz band. Interference can be caused by overlapping channels. Any two channel numbers that differ by five or more, such as 2 and 7, do not overlap (noadjacent-channel interference). The oft-repeated adage that channels 1, 6, and 11 are theonlynon-overlapping channels is, therefore, not accurate. Channels 1, 6, and 11 are the onlygroup of threenon-overlapping channels in North America. However, whether the overlap is significant depends on physical spacing. Channels that are four apart interfere a negligible amount – much less than reusing channels (which causesco-channel interference) – if transmitters are at least a few metres apart.[115]In Europe and Japan where channel 13 is available, using Channels 1, 5, 9, and 13 for802.11gand802.11nis viable andrecommended.
However, multiple 2.4 GHz 802.11b and 802.11g access-points default to the same channel on initial startup, contributing to congestion on certain channels. Wi-Fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices' use of other access points as well as with decreasedsignal-to-noise ratio(SNR) between access points. These issues can become a problem in high-density areas, such as large apartment complexes or office buildings with multiple Wi-Fi access points.[116]
Other devices use the 2.4 GHz band:[91]microwave ovens, ISM band devices,security cameras, Zigbee devices, Bluetooth devices,video senders, cordless phones,baby monitors,[117]and, in some countries,amateur radio, all of which can cause significant additional interference. It is also an issue when municipalities[118]or other large entities (such as universities) seek to provide large area coverage. On some 5 GHz bands interference from radar systems can occur in some places. For base stations that support those bands they employ Dynamic Frequency Selection which listens for radar, and if it is found, it will not permit a network on that band.
These bands can be used by low power transmitters without a licence, and with few restrictions. However, while unintended interference is common, users that have been found to cause deliberate interference (particularly for attempting to locally monopolize these bands for commercial purposes) have been issued large fines.[119]
Various layer-2 variants of IEEE 802.11 have different characteristics. Across all flavours of 802.11, maximum achievable throughputs are either given based on measurements under ideal conditions or in the layer-2 data rates. This, however, does not apply to typical deployments in which data are transferred between two endpoints of which at least one is typically connected to a wired infrastructure, and the other is connected to an infrastructure via a wireless link.
This means that typically data frames pass an 802.11 (WLAN) medium and are being converted to 802.3 (Ethernet) or vice versa.
Due to the difference in the frame (header) lengths of these two media, the packet size of an application determines the speed of the data transfer. This means that an application that uses small packets (e.g. VoIP) creates a data flow with high overhead traffic (lowgoodput).
Other factors that contribute to the overall application data rate are the speed with which the application transmits the packets (i.e. the data rate) and the energy with which the wireless signal is received. The latter is determined by distance and by the configured output power of the communicating devices.[120][121]
The same references apply to the attached throughput graphs, which show measurements ofUDPthroughput measurements. Each represents an average throughput of 25 measurements (the error bars are there, but barely visible due to the small variation), is with specific packet size (small or large), and with a specific data rate (10 kbit/s – 100 Mbit/s). Markers for traffic profiles of common applications are included as well. This text and measurements do not cover packet errors but information about this can be found at the above references. The table below shows the maximum achievable (application-specific) UDP throughput in the same scenarios (same references again) with various WLAN (802.11) flavours. The measurement hosts have been 25 metres (yards) apart from each other; loss is again ignored.
Wi-Fi allows wireless deployment of local area networks (LANs). Also, spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs. However, building walls of certain materials, such as stone with high metal content, can block Wi-Fi signals.
A Wi-Fi device is ashort-rangewirelessdevice. Wi-Fi devices arefabricatedonRF CMOSintegrated circuit(RF circuit) chips.[122]
Since the early 2000s, manufacturers are building wireless network adapters into most laptops. The price ofchipsetsfor Wi-Fi continues to drop, making it an economical networking option included in ever more devices.[123]
Different competitive brands of access points and client network-interfaces can inter-operate at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance arebackward compatible. Unlikemobile phones, any standard Wi-Fi device works anywhere in the world.
A wireless access point (WAP) connects a group of wireless devices to an adjacent wired LAN. An access point resembles anetwork hub, relayingdatabetween connected wireless devices in addition to a (usually) single connected wired device, most often an Ethernet hub or switch, allowing wireless devices to communicate with other wired devices.
Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as mini PCIe (mPCIe,M.2), USB,ExpressCardand previously PCI, Cardbus, andPC Card. As of 2010, most newer laptop computers come equipped with built-in internal adapters.
Wireless routersintegrate a Wireless Access Point, Ethernetswitch, and internal router firmware application that providesIProuting,NAT, andDNSforwarding through an integrated WAN-interface. A wireless router allows wired and wireless Ethernet LAN devices to connect to a (usually) single WAN device such as a cable modem,DSL modem, oroptical modem. A wireless router allows all three devices, mainly the access point and router, to be configured through one central utility. This utility is usually an integratedweb serverthat is accessible to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a computer, as is the case with as Apple's AirPort, which is managed with theAirPort UtilityonmacOSand iOS.[124]
Wirelessnetwork bridgescan act to connect two networks to form a single network at thedata-link layerover Wi-Fi. The main standard is thewireless distribution system(WDS).
Wireless bridging can connect a wired network to a wireless network. A bridge differs from an access point: an access point typically connects wireless devices to one wired network. Two wireless bridge devices may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes or for devices that have no wireless networking capability (but have wired networking capability), such asconsumer entertainment devices; alternatively, a wireless bridge can be used to enable a device that supports a wired connection to operate at a wireless networking standard that is faster than supported by the wireless network connectivity feature (external dongle or inbuilt) supported by the device (e.g., enabling Wireless-N speeds (up to the maximum supported speed on the wired Ethernet port on both the bridge and connected devices including the wireless access point) for a device that only supports Wireless-G).
A dual-band wireless bridge can also be used to enable 5 GHz wireless network operation on a device that only supports 2.4 GHz wireless and has a wired Ethernet port.
Wireless range-extenders orwireless repeaterscan extend the range of an existing wireless network. Strategically placed range-extenders can elongate a signal area or allow for the signal area to reach around barriers such as those pertaining in L-shaped corridors. Wireless devices connected through repeaters suffer from an increased latency for each hop, and there may be a reduction in the maximum available data throughput. Besides, the effect of additional users using a network employing wireless range-extenders is to consume the available bandwidth faster than would be the case whereby a single user migrates around a network employing extenders. For this reason, wireless range-extenders work best in networks supporting low traffic throughput requirements, such as for cases whereby a single user with a Wi-Fi-equipped tablet migrates around the combined extended and non-extended portions of the total connected network. Also, a wireless device connected to any of the repeaters in the chain has data throughput limited by the "weakest link" in the chain between the connection origin and connection end. Networks using wireless extenders are more prone to degradation from interference from neighbouring access points that border portions of the extended network and that happen to occupy the same channel as the extended network.
The security standard,Wi-Fi Protected Setup, allows embedded devices with a limited graphical user interface to connect to the Internet with ease. Wi-Fi Protected Setup has 2 configurations: The Push Button configuration and the PIN configuration. These embedded devices are also called TheInternet of thingsand are low-power, battery-operated embedded systems. Several Wi-Fi manufacturers design chips and modules for embedded Wi-Fi, such as GainSpan.[125]
Increasingly in the last few years (particularly as of 2007[update]), embedded Wi-Fi modules have become available that incorporate a real-time operating system and provide a simple means of wirelessly enabling any device that can communicate via a serial port.[126]This allows the design of simple monitoring devices. An example is a portable ECG device monitoring a patient at home. This Wi-Fi-enabled device can communicate via the Internet.[127]
These Wi-Fi modules are designed byOEMsso that implementers need only minimal Wi-Fi knowledge to provide Wi-Fi connectivity for their products.
In June 2014,Texas Instrumentsintroduced the first ARM Cortex-M4 microcontroller with an onboard dedicated Wi-Fi MCU, the SimpleLink CC3200. It makes embedded systems with Wi-Fi connectivity possible to build as single-chip devices, which reduces their cost and minimum size, making it more practical to build wireless-networked controllers into inexpensive ordinary objects.[128]
The main issue with wirelessnetwork securityis its simplified access to the network compared to traditional wired networks such as Ethernet. With wired networking, one must either gain access to a building (physically connecting into the internal network), or break through an externalfirewall. To access Wi-Fi, one must merely be within the range of the Wi-Fi network. Most business networks protect sensitive data and systems by attempting to disallow external access. Enabling wireless connectivity reduces security if the network uses inadequate or no encryption.[129][130][131]
An attacker who has gained access to a Wi-Fi network router can initiate a DNS spoofing attack against any other user of the network by forging a response before the queried DNS server has a chance to reply.[132]
A common measure to deter unauthorized users involves hiding the access point's name by disabling the SSID broadcast. While effective against the casual user, it is ineffective as a security method because the SSID is broadcast in the clear in response to a client SSID query. Another method is to only allow computers with known MAC addresses to join the network,[133]but determined eavesdroppers may be able to join the network byspoofingan authorized address.
Wired Equivalent Privacy(WEP) encryption was designed to protect against casual snooping but it is no longer considered secure. Tools such asAirSnortorAircrack-ngcan quickly recover WEP encryption keys.[134]Because of WEP's weakness the Wi-Fi Alliance approved Wi-Fi Protected Access (WPA) which usesTKIP. WPA was specifically designed to work with older equipment usually through a firmware upgrade. Though more secure than WEP, WPA has known vulnerabilities.
The more secureWPA2usingAdvanced Encryption Standardwas introduced in 2004 and is supported by most new Wi-Fi devices. WPA2 is fully compatible with WPA.[135]In 2017, a flaw in the WPA2 protocol was discovered, allowing a key replay attack, known asKRACK.[136][137]
A flaw in a feature added to Wi-Fi in 2007, calledWi-Fi Protected Setup(WPS), let WPA and WPA2 security be bypassed. The only remedy as of 2011[update]was to turn off Wi-Fi Protected Setup,[138]which is not always possible.
Virtual private networkscan be used to improve the confidentiality of data carried through Wi-Fi networks, especially public Wi-Fi networks.[139]
AURIusing the WIFI scheme can specify the SSID, encryption type, password/passphrase, and if the SSID is hidden or not, so users can follow links fromQR codes, for instance, to join networks without having to manually enter the data.[140]AMeCard-like format is supported by Android and iOS 11+.[141]
Wi-Fi access points typically default to an encryption-free (open) mode. Novice users benefit from a zero-configuration device that works out-of-the-box, but this default does not enable anywireless security, providing open wireless access to a LAN. To turn security on requires the user to configure the device, usually via a softwaregraphical user interface(GUI). On unencrypted Wi-Fi networks connecting devices can monitor and record data (including personal information). Such networks can only be secured by using other means of protection, such as aVPN, orHypertext Transfer ProtocoloverTransport Layer Security(HTTPS).
The older wireless-encryptionstandard, Wired Equivalent Privacy (WEP), has beenshowneasily breakable even when correctly configured. Wi-Fi Protected Access (WPA) encryption, which became available in devices in 2003, aimed to solve this problem. Wi-Fi Protected Access 2 (WPA2) ratified in 2004 is considered secure, provided a strongpassphraseis used. The 2003 version of WPA has not been considered secure since it was superseded by WPA2 in 2004.
In 2018,WPA3was announced as a replacement for WPA2, increasing security;[142]it rolled out on 26 June.[143]
Piggybacking refers to access to a wireless Internet connection by bringing one's computer within the range of another's wireless connection, and using that service without the subscriber's explicit permission or knowledge.
During the early popular adoption of802.11, providing open access points for anyone within range to use was encouraged[by whom?]to cultivatewireless community networks,[144]particularly since people on average use only a fraction of their downstream bandwidth at any given time.
Recreational logging and mapping of other people's access points have become known aswardriving. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. Providing access to one's Internet connection in this fashion may breach the Terms of Service or contract with theISP. These activities do not result in sanctions in most jurisdictions; however, legislation andcase lawdiffer considerably across the world. A proposal to leavegraffitidescribing available services was calledwarchalking.[145]
Piggybacking often occurs unintentionally – a technically unfamiliar user might not change the default "unsecured" settings to their access point and operating systems can be configured to connect automatically to any available wireless network. A user who happens to start up a laptop in the vicinity of an access point may find the computer has joined the network without any visible indication. Moreover, a user intending to join one network may instead end up on another one if the latter has a stronger signal. In combination with automatic discovery of other network resources (seeDHCPandZeroconf) this could lead wireless users to send sensitive data to the wrong middle-man when seeking a destination (seeman-in-the-middle attack). For example, a user could inadvertently use an unsecured network to log into awebsite, thereby making the login credentials available to anyone listening, if the website uses an insecure protocol such as plainHTTPwithoutTLS.
On an unsecured access point, an unauthorized user can obtain security information (factory preset passphrase or Wi-Fi Protected Setup PIN) from a label on a wireless access point and use this information (or connect by the Wi-Fi Protected Setup pushbutton method) to commit unauthorized or unlawful activities.
Wireless Internet access has become much more embedded in society. It has thus changed how the society functions in a number of ways.
As of 2017[update]over half the world did not have access to the Internet,[76]prominently rural areas in developing nations. Technology that has been implemented in more developed nations is often costly and energy inefficient. This has led to developing nations using more low-tech networks, frequently implementing renewable power sources that can solely be maintained throughsolar power, creating a network that is resistant to disruptions such as power outages. For instance, in 2007, a 450-kilometre (280 mi) network between Cabo Pantoja andIquitosinPeruwas erected in which all equipment is powered only bysolar panels.[76]These long-range Wi-Fi networks have two main uses: offer Internet access to populations in isolated villages, and to provide healthcare to isolated communities. In the case of the latter example, it connects the central hospital in Iquitos to 15 medical outposts which are intended for remote diagnosis.[76]
Access to Wi-Fi in public spaces such as cafes or parks allows people, in particular freelancers, to work remotely. While the accessibility of Wi-Fi is the strongest factor when choosing a place to work (75% of people would choose a place that provides Wi-Fi over one that does not),[71]other factors influence the choice of specifichotspots. These vary from the accessibility of other resources, like books, the location of the workplace, and the social aspect of meeting other people in the same place. Moreover, the increase of people working from public places results in more customers for local businesses thus providing an economic stimulus to the area.
Additionally, in the same study it has been noted that wireless connection provides more freedom of movement while working. Both when working at home or from the office it allows the displacement between different rooms or areas. In some offices (notably Cisco offices in New York) the employees do not have assigned desks but can work from any office connecting their laptop to Wi-Fihotspot.[71]
The Internet has become an integral part of living. As of 2016[update], 81.9% of American households have Internet access.[146]Additionally, 89% of American households with broadband connect via wireless technologies.[147]72.9% of American households have Wi-Fi.
Wi-Fi networks have also affected how the interior of homes and hotels are arranged. For instance, architects have described that their clients no longer wanted only one room as their home office, but would like to work near the fireplace or have the possibility to work in different rooms. This contradicts architect's pre-existing ideas of the use of rooms that they designed. Additionally, some hotels have noted that guests prefer to stay in certain rooms since they receive a stronger Wi-Fi signal.[71]
TheWorld Health Organization(WHO) says, "no health effects are expected from exposure to RF fields from base stations and wireless networks", but notes that they promote research into effects from other RF sources.[148][149](a category used when "a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence"),[150]this classification was based on risks associated with wireless phone use rather than Wi-Fi networks.
The United Kingdom'sHealth Protection Agencyreported in 2007 that exposure to Wi-Fi for a year results in the "same amount of radiation from a 20-minute mobile phone call".[151]
A review of studies involving 725 people who claimedelectromagnetic hypersensitivity, "...suggests that 'electromagnetic hypersensitivity' is unrelated to the presence of an EMF, although more research into this phenomenon is required."[152]
Several other wireless technologies provide alternatives to Wi-Fi for different use cases:
Some alternatives are "no new wires", re-using existing cable:
Severalwiredtechnologies for computer networking, which provide viable alternatives to Wi-Fi:
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Wireless USBis a short-range, high-bandwidthwirelessradiocommunication protocolversion of the Universal Serial Bus (USB) created by the Wireless USB Promoter Group. It is unrelated toWi-FiandCypressWireless USB. It was maintained by theWiMedia Alliancewhich ceased operations in 2009.
Wireless USB is based on theWiMedia Alliance'sUltra-WideBand(UWB) common radio platform, which is capable of sending 480Mbit/sat distances up to 3 metres (9.8 ft) and 110 Mbit/s at distances up to 10 metres (33 ft). It is designed to operate in the 3.1 to 10.6GHzfrequency range, although local regulatory policies may restrict the legal operating range in some countries.
The standard is now obsolete, and no new hardware has been produced for many years, although it has been adopted byAndroidfor precise signaling[1]
Support for the standard was deprecated inLinux5.4[2][3]and removed in Linux 5.7[4]
The rationale for this specification was the overwhelming success ofUSBas a base for peripherals everywhere; cited reasons include extreme ease of use and low cost, which allow the existence of a ubiquitous bidirectional, fastportarchitecture. The definition ofUltra-WideBand(UWB) matches the capabilities and transfer rates of USB very closely (from 1.5 and 12 Mbit/s up to 480 Mbit/s for USB 2.0) and makes for a natural wireless extension of USB in the short range (3 meters, up to 10 at a reduced rate of 110 Mbit/s). Still, there was no physicalbusto power the peripherals any more, and the absence of wires means that some properties that are usually taken for granted in USB systems need to be achieved by other means.
The goal of the specification was to preserve the functional model ofUSB, based on intelligent hosts and behaviorally simple devices, while allowing it to operate in awirelessenvironment and keeping security on a par with the levels offered by traditional wired systems. It also seeks to be comparably power-efficient. To accomplish this, it uses an existing standard that defines a suitablephysical layerandmedium access control, through which the desired performance can be met, and it adds to it a convergence layer to merge both architectural efforts.
W-USB was defined as a bus, albeit logical and not physical, which can simultaneously connect ahostwith a number of peripherals. The host divides the available bandwidth through atime-division multiple access(TDMA) strategy. It maintains the ability of USB to safely manage deviceson the fly. Hosts can communicate with devices up to 10 meters away.
Wireless USB had potential uses ingame controllers,printers,scanners,digital cameras,portable media players,hard disk drivesandUSB flash drives.[citation needed]It was also suitable for transferring parallel video streams, using USB overultra-widebandprotocols.
The Wireless USB Promoter Group was formed in February 2004 to define the Wireless USBprotocol. The group consisted ofAgere Systems(now merged withLSI Corporation[5]),Hewlett-Packard,Intel,Microsoft,NEC Corporation,Philips Semiconductors, andSamsung.[6]
In May 2005, the Wireless USB Promoter Group announced version 1.0 of the Wireless USB specification.[7]
In June 2006, five companies showed the first multi-vendor interoperability demonstration of wireless USB. A laptop with anIntelhost adapter using anAlereonPHY was used to transfer high-definition video from aPhilipswireless semiconductor with a Staccato Communications PHY, all usingMicrosoftWindows XPdrivers developed for Wireless USB.
In October 2006, the U.S.Federal Communications Commission(FCC) approved Host Wire Adapter (HWA) and Device Wire Adapter (DWA) wireless USB products fromWiQuest Communicationsfor both outdoor and indoor use. The first retail product was shipped by IOGEAR usingAlereon, Intel, and NEC silicon in mid-2007. Around the same time, Belkin, Dell, Lenovo, and D-Link began shipping products that incorporated WiQuest technology. These products included embedded cards in notebook PCs or adapters for those PCs that do not currently include wireless USB. In 2008, a new wireless USB docking station from Kensington was made available through Dell. This product was unique as it was the first product on the market to support video and graphics over a USB connection by usingDisplayLinkUSB graphics technology. Kensington released a Wireless USB Universal Docking Station in August 2008 for wireless connectivity between a notebook PC and an external monitor, speakers, and existing wired USB peripherals.Imationannounced the Q4 2008 availability of a new external Wireless HDD.[8]
On March 16, 2009, theWiMedia Allianceannounced transfer agreements for the WiMedia ultra-wideband (UWB) specifications. WiMedia transferred specifications to theBluetoothSpecial Interest Group (SIG), the Wireless USB Promoter Group, and theUSB Implementers Forum. After the technology transfer, the WiMedia Alliance ceased operations.[9][10][11]In October 2009, the Bluetooth Special Interest Group dropped the development of UWB as part of the alternative MAC/PHY, Bluetooth 3.0/High Speed technology. A small, but significant, number of former WiMedia members had not and would not sign up to the necessary agreements for theintellectual propertytransfer. The Bluetooth group then turned its attention from UWB to60 GHz.[12][13][14]
On September 29, 2010, version 1.1 of the Wireless USB specification was announced.[15]It delivered several backwards-compatible improvements: UWB upper band support for frequencies 6 GHz and above, improved power management and consumption, and support forNFCand proximity based association.
As mentioned, the USB model is preserved, and generally minor adjustments made to fit the specific needs of a wireless system. The changes are as follows, from top to bottom:
The replacement ofcopper wiresin the bus layer introduces ambiguity in the actual state of host-device connections and, even more importantly, potentially exposes communications fully to any other device within the propagation range, whereas they were reasonably secure over the wire. Hence, an explicit secure relationship must be established. For this, the bus and device layers incorporate the necessary resources for use by the function layer. Every W-USB transmission is encrypted by the bus layer without impairing layer-to-layer horizontal communication.
The bus follows a TDMA-basedpollingapproach supervised by the host. A transfer is formed by three parts: atoken, data, and ahandshake. For efficiency reasons, several tokens containing timing information for the devices can be grouped into one, thus formingtransaction groups. Flow control and packet sizes are adjusted for power efficiency, while respecting the high-levelpipemodel of communication between source and destination.
Even preserving the USB model typical error rates in wireless media require modifications in the mechanisms used to achieve said model: among others, data handshakes and buffering.
UWB defines both PHY and MAC layers, which need to be integrated in the W-USB model. In particular, MAC is joined with thelogical link control(LLC) sublayer to form thelink layer, responsible for encryption/decryption, PHY error management and synchronization, while PHY itself covers the correctness of headers, not payloads.
The MAC layer is particularly relevant to W-USB. It usessuperframesdivided in 256time slots, the first of which are dedicated to the transfer ofbeaconing information. Slots can further be allocated to meet the necessities of clusters of devices, also identified by MMC's (see below). A host maintains one or more W-USB communication channels and is fully aware of the MAC layer, whereas a device only needs to use the defined W-USB interface to communicate through existing channels.
There are three degrees of MAC consciousness in devices. The highest of these corresponds to aself-beaconing device, which is able to perform beaconing on its own. The following degree representsdirected-beaconing devices, which are unaware of MAC frames and have limited beaconing capabilities, depending on the host to detect and beacon for nearby devices. Lastly there arenon-beaconing devices, which have a very limited ability to transmit and receive; on the other hand, devices which are undetectable by the host can not be affected by these devices, nor can affect them.
Thus, non-beaconing devices can only operate in very close vicinity to the host. Directed- and self-beaconing devices must be able to identify their hidden neighbors, which they do by emitting beacons. On their end, hosts manage global timers with the precision the physical medium requires (20ppm). Channel time is sent within MMC's, and it is used for slot allocation, so it is important that hosts perform accurate beaconing. Devices may as well beacon reservation declarations.
The superframe includes device notification time slots for asynchronous transfers initiated by the devices (which do not use pipes, but instead tap the bus layer directly); the host dynamically assigns slots as needed. Besides these, W-USB transactions between the host andendpointsare carried out as in USB.
Transactions use TDMA microscheduling while adhering to USB semantics. Asplit-transaction protocolis used to allow multiple transactions to be carried out simultaneously. This is related to the transaction group concept, which consists of amicroscheduled management command(MMC) and allocated time slots for the execution of its associated workload.
Wireless data transfers tend to incur in very significant overheads; to mitigate this W-USB replaces these with theburst mode data phase, which groups one or more data packets which reducing packet delimiters and separation gaps, in contrast with the USB rule of one data packet per transaction. The extent to which this practice is applied can be adjusted, resulting in a varying degree of equity between competing devices.
The specification defines four particular data transfer types; their identifying features are summarized here.
Power management can also affect data transport, since devices may control their power use at their discretion. The fact that the communications protocol is based on TDMA means that both host and devices know exactly when their presence is not required, and can use this to enter power saving modes. Devices may turn off their radios transparently to the host while maintaining their connections. They can also turn off over extended periods of time if they previously notify the host, as they will ignore all communications from said host. Eventually, the device will trigger the wakeup procedure and check for pending work.
In turn, the host will usually turn its radio off when it is not needed. If it decides to stop the channel, be in temporarily or to enter hibernation or shutdown states, it must notify the devices before it can do so.
The WUSB architecture allows up to 127 devices to connect directly to a host. Because there are no wires or ports, there is no longer a need for hubs.
However, to facilitate migration from wired to wireless, WUSB introduced a newDevice Wire Adapter (DWA)class. Sometimes referred to as a "WUSB hub", a DWA allows existing USB 2.0 devices to be used wirelessly with a WUSB host.
WUSB host capability can be added to existing PCs through the use of aHost Wire Adapter (HWA). The HWA is a USB 2.0 device that attaches externally to a desktop or laptop's USB port or internally to a laptop's MiniCard interface.
WUSB also supportsdual-role devices (DRDs), which in addition to being a WUSB device, can function as ahostwith limited capabilities. For example, a digital camera could act as a device when connected to a computer and as a host when transferring pictures directly to a printer.
W-USB can form true USB systems, formed by a host, devices and interconnection support. It implements the USBhub–spokemodel, in which up to 127 wireless devices can formpoint-to-point links(spokes) with the host (the hub). The host controller is unique in the system and is usually embedded in a working computer, though it could be connected to it through a simple USB connection, possibly wireless as well. Such a topology is similar to astar network(but all communications are strictly point-to-point, never between devices).
In order to allow common wired USB devices to be connected, the specification definesdevice wire adapters. Likewise, hosts connect to W-USB systems through use of ahost wire adapter. Even though the physical layer is based on Ultra-WideBand, W-USB devices have a fully compliant USB interface. The physical layer may support a wide range of transfer rates, of which three are defined as mandatorily supported: 53.3, 106.7 and 200 Mbit/s, all other possible UWB rates being optional for devices (hosts must support them all).
W-USB devices are categorized in the same way as traditional USB. Because of the existence of wire adapters, traditional USB hubs are not needed. A device supports one or more communication pipes to the host, and allocates endpoint 0 for the USB control pipe. Device type information is available through this pipe.
Connections with the host are created by means of an establishment message sent at some point. Both host and device can then proceed to authenticate using their unique keys; if the process succeeds, the host assigns a unique USB address to the device, after which the device becomes visible to the USB protocol. Because the connectivity model allows for on-the-fly, unannounced disconnection, connections must always remain active. Aside from host- or device-forced disconnections, long inactivity periods may trigger the same termination mechanisms.
In addition, W-USB hosts have other responsibilities which go beyond those of a wired host; namely, their MAC sublayer is responsible for supervising the suitability of device MAC layers. If needed, this requires assisting them in their beaconing duties and processing the beaconing data that could be sent to them. Furthermore, the UWB radio and associated bandwidth may be shared with other entities, and the host must make sure that the defined policies are satisfied; according to shared use (which may be coordinated to avoid interference) it will be able to offer full or partial functionality.
UWB is a general term for radio communication using pulses of energy which spread emitted Radio Frequency energy over 500 MHz+ of spectrum or exceeding 20% fractional bandwidth within the frequency range of 3.1 GHz to 10.6 GHz as defined by the FCC ruling issued for UWB in February 2002. UWB is not specific to WiMedia or any other company or group and there are in fact a number of groups and companies developing UWB technology totally unrelated to WiMedia. WUSB was a protocol promulgated by theUSB Implementers Forumthat used WiMedia's UWB radio platform. Other protocols that announced their intention to use WiMedia's UWB radio platform included Bluetooth and the WiMedia Logical Link Control Protocol.[citation needed]
A few issues differentiate Wireless USB from other proposed/competing standards that utilize 60 GHz band likeWiGig:
Robustness is one of the main concerns upon which the specification is built, and as such resource management and connection/disconnection of devices becomes even more important than in wired USB.Packet loss and corruptionare dealt with throughtimeoutsas well as hardware buffering, guaranteed retries (as mentioned in the description of transfer models) and otherflow controlmethods. If synchronism policies cannot be maintained, errors can be handled either by hardware or software (retries, maximum number of retries failure, failure recovery decisions and so on).
The W-USB host tries to mitigate the unreliability of wireless mediums (a 10% error rate is considered acceptable for 1 kB packets; in wired media this value is usually around 10−9) maintaining counters and statistics for each device and possible requesting information from them. It can also access and modify thetransmit power controlfunctions of each device, as well as change transmission parameters such as data payload size and bandwidth adjustments.
The focus is always on providing quality of service comparable to that of traditional USB. Wires offer a very high level of security (given a typical trusted working environment), so standard USB does not deal with it, even though it does not hinder its applicability or implementability; W-USB manages security explicitly, but instead of harnessing the base of UWB it designs a model which is valid for USB in general. Because of this, it must be added to the common USBdevice control plane.
For communication to exist, secure relationships must be established. These must have a defined purpose and restrict membership to the group, which serves as the base of trust to carry out the desired work. Within a wired systems, data transfers imply a controlled physical connection; this translates into the wireless domain through the concept ofownership: the user grants trust to the devices, which in turn prove this trust to others (interacting in so-calledceremonies) in order to form the desired associations. The USB address identifier is a token of the owner's trust. Applications may require other bases of trust not directly supported by this USB-specific model, in which case they can be implemented on top of the core USB stack.
Even more, trust needs to be maintained, otherwise it will expire. After receiving the group key of a cluster, a device must keep the connection alive by at least confirming its presence within eachtrust timeoutboundary, which is set to four seconds. If it does not succeed at keeping up with this requirement, reauthentication is demanded.
Following the natural asymmetry of USB, the host initiates all processes (except signaling), security being no exception. Security requests are made to devices to find their security capabilities, after which the appropriate devices can be chosen. The standard,symmetric encryptionmethod isAES-128withCCM, thoughPublic keyencryption may be used for initial authentication (namely, only the sending of the initial CCM key), provided that the achieved security level is comparable (in practice by using 3072-bitRSAandSHA-256for hashing).
Note that there is a difference betweenmaster keysandsession keys. Master keys are long-lived and usually work as a shared secret or a means to distribute session keys, which in turn do not outlive the connection for which they were created and usually serve as the functional encryption/decryption mechanism. A specific header field indicates which of the possible keys is to be used. It is also important to note that replay prevention mechanisms require the keeping of counters which are updated on valid receptions. The range of these counters further limits the life of session keys.
Other forms of USB over wireless exist, such as those based on the competing direct sequenceultra-widebandtechnology by Cable-Free USB.[19]The same was also true for other radio frequency based wire replacement systems which could carry USB. The result was that the nameCertified Wireless USBwas adopted to allow consumers to identify which products would be adherent to the standard and would support the correct protocol and data rates.
There was also USB over IP, which may have used IP-based networking to transfer USB traffic wirelessly. For example, with proper drivers the host side may have used 802.11a/b/g/n/ac Wi-Fi (or wiredEthernet) to communicate with the device.[20]
As of 2013[update],Media Agnostic USB(MA USB) is a specification being developed by theUSB Implementers Forum. It is intended to enable communication using theUniversal Serial Bus(USB) protocol to be performed over a wide range of physical communication media, includingWiFiandWiGigwireless networks.[21]The protocol is being developed from the base of theWi-Fi Alliance's previousWiGig Serial Extensionspecification.[22][23]
Media Agnostic USB is distinct from, and should not be confused with, previous wireless USB protocols such as Certified Wireless USB.
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Bluetooth Meshis a computermesh networkingstandardbased onBluetooth Low Energythat allows for many-to-many communication over Bluetooth radio. The Bluetooth Mesh specifications were defined in the Mesh Profile[1]and Mesh Model[2]specifications by theBluetooth Special Interest Group(Bluetooth SIG). Bluetooth Mesh was conceived in 2014[3]and adopted on July 13, 2017(2017-07-13).[4]
Bluetooth Mesh is amesh networkingstandard that operates on aflood networkprinciple. It's based on the nodes relaying the messages: every relay node that receives a network packet that
can be retransmitted with TTL = TTL - 1. Message caching is used to prevent relaying recently seen messages.
Communication is carried in the messages that may be up to 384 bytes long, when using Segmentation and Reassembly (SAR) mechanism, but most of the messages fit in one segment, that is 11 bytes. Each message starts with an opcode, which may be a single byte (for special messages), 2 bytes (for standard messages), or 3 bytes (for vendor-specific messages).
Every message has a source and a destination address, determining which devices process messages. Devices publish messages to destinations which can be single things / groups of things / everything.
Each message has a sequence number that protects the network against replay attacks.
Each message is encrypted and authenticated. Two keys are used to secure messages: (1) network keys – allocated to a single mesh network, (2) application keys – specific for a given application functionality, e.g. turning the light on vs reconfiguring the light.
Messages have atime to live(TTL). Each time message is received and retransmitted, TTL is decremented which limits the number of "hops", eliminating endless loops.
Bluetooth Mesh has a layered architecture, with multiple layers as below.
Nodes that support the various features can be formed into a particular mesh network topology.
to enable larger networks.
advertising bearers.
duty cycles only in conjunction with a node supporting the Friend feature.
messages destined for those nodes.
The practical limits of Bluetooth Mesh technology are unknown. Some limits that are built into the specification include:
Number of virtual groups is 2128.
As of version 1.0 of Bluetooth Mesh specification,[2]the following standard models and model groups have been defined:
Foundation models have been defined in the core specification. Two of them are mandatory for all mesh nodes.
Provisioning is a process of installing the device into a network. It is a mandatory step to build a Bluetooth Mesh network.
In the provisioning process, a provisioner securely distributes a network key and a unique address space for a device. The provisioning protocol uses P256 Elliptic CurveDiffie-HellmanKey Exchange to create a temporary key to encrypt network key and other information. This provides security from a passive eavesdropper.
It also provides various authentication mechanisms to protect network information, from an active eavesdropper who usesman-in-the-middle attack, during provisioning process.
A key unique to a device known as "Device Key" is derived from elliptic curve shared secret on provisioner and device during the provisioning process. This device key is used by the provisioner to encrypt messages for that specific device.
The security of the provisioning process has been analyzed in a paper presented during theIEEE CNS2018 conference.[5]
The provisioning can be performed using a Bluetooth GATT connection or advertising using the specific bearer.[1]
Free softwareandopen source softwareimplementations include the following:
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Bluejackingis the sending of unsolicited messages overBluetoothto Bluetooth-enabled devices such asmobile phones,PDAsorlaptop computers,[1]sending avCardwhich typically contains a message in the name field (i.e., for bluedating) to another Bluetooth-enabled device via theOBEXprotocol.
Bluetooth has a very limited range, usually around 10 metres (32.8 ft) on mobile phones, but laptops can reach up to 100 metres (328 ft) with powerful (Class 1) transmitters.
Bluejacking was reportedly first carried out between 2001 and 2003 by a Malaysian IT consultant who used his phone to advertiseEricssonto a singleNokia 7650phone owner in a Malaysian bank.[2]He also invented the name, which he claims is an amalgam ofBluetoothandajack, his username on Esato, a Sony Ericsson fan online forum.Jackingis, however, an extremely common shortening of "hijack', the act of taking over something.[3][4]Ajack's original posts are hard to find, but references to the exploit are common in 2003 posts.
Another user on the forum claims earlier discovery,[5]reporting a near-identical story to that attributed toAjack, except they describe bluejacking 44 Nokia 7650 phones instead of one, and the location is a garage, seemingly inDenmark, rather than a Malaysian Bank. Also, the message was an insult to Nokia owners rather than aSony Ericssonadvertisement.
Bluejacking is usually not very harmful, except that bluejacked people generally don't know what has happened, and so may think that their phone is malfunctioning. Usually, a bluejacker will only send a text message, but with modern phones it's possible to send images or sounds as well. Bluejacking has been used inguerrilla marketingcampaigns to promoteadvergames.
The actual message itself doesn't deploy anymalwareto the software; rather, it is crafted to elicit a response from the user or add a new contact and can be seen as more of aprankthan an attack. These messages can evoke either annoyance or amusement in the recipient. Users typically possess the ability to reject such messages, and this tactic is frequently employed in confined environments such as planes, trains, and buses.[6]However, some forms ofDoSDisruptions are still possible, even in modern devices, by sending unsolicited pairing requests in rapid succession; this becomes disruptive because most systems display a full screen notification for every connection request, interrupting every other activity, especially on less powerful devices.
Bluejacking is also confused withBluesnarfing, which is the way in which mobile phones are illegally hacked via Bluetooth.
BlueJackQ is a website dedicated to bluejacking. The website contains a few bluejacking stories taken from the site's forum. The website also includes software that can be used for bluejacking and guides on how to bluejack which are slightly out of date but the basic principle still applies to most makes of phone. Its forum has 4,000 registered users and 93,050 posts.[7]The website has been featured in many news articles.[8]
The forums[7]were opened on the November 13, 2003 and has been the center of BluejackQ from the start. It currently has 4 moderators and has 20 different sections available to members. The areas included information about BluejackQ, reviews of mobile phones, media players, PDAs and Miscellaneous devices, general bluejacking threads and an off-topic area. The BluejackQpodcastwas first released as a test version on January 15, 2006, thus becoming the first bluejacking-related podcast. Podcasts 1, 2 and 3 featured three members of the forums.[citation needed]
The forums seem to have been unused since 2020.
The authentic bluejacking as described here is not the same exploit which was frequently depicted in the television seriesPerson of Interest; that fictional exploit portrayeddifferent and more invasive capabilities.
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Bluebuggingis a form ofBluetoothattack often caused by a lack of awareness. It was developed after the onset ofbluejackingandbluesnarfing. Similar to bluesnarfing, bluebugging accesses and uses all phone features[1]but is limited by the transmitting power of class 2 Bluetooth radios, normally capping its range at 10–15 meters. However, the operational range can be increased with the use of adirectional antenna.[2][3]
Bluebugging was developed by the German researcher Martin Herfurt in 2004, one year after the advent of bluejacking.[2]Initially a threat against laptops with Bluetooth capability,[4]it later targeted mobile phones[5]and PDAs.
Bluebugging manipulates a target phone into compromising its security, this to create a backdoor attack before returning control of the phone to its owner. Once control of a phone has been established, it is used to call back the hacker who is then able to listen in to conversations, hence the name "bugging".[5]The Bluebug program also has the capability to create a call forwarding application whereby the hacker receives calls intended for the target phone.[1]
A further development of Bluebugging has allowed for the control of target phones through Bluetooth phone headsets, It achieves this by pretending to be the headset and thereby "tricking" the phone into obeying call commands. Not only can a hacker receive calls intended for the target phone, they can send messages, read phonebooks, and examine calendars.
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Pod slurpingis the act of using a portabledata storage devicesuch as aniPoddigital audio playerto illicitlydownloadlarge quantities ofconfidentialdata by directly plugging it into a computer where thedataare held, and which may be on the inside of afirewall. The phrase "pod slurping" was introduced by Abe Usher. It pertains to a malicious program embedded in aUSB storage device, which activates automatically upon being connected to a host.[1]
There has been some work in the development of fixes to the problem, including a number ofthird-partysecurity products that allow companies to set security policies related toUSBdevice use, and features withinoperating systemsthat allow IT administrators or users to disable the USB port altogether.Unix-based orUnix-likesystems can easily prevent users frommountingstorage devices, andMicrosofthas released instructions for preventing users from installing USBmass storage deviceson its operating systems.[2]
Additional measures include physical obstruction of the USB ports, with measures ranging from the simple filling of ports with epoxy resin to commercial solutions which deposit a lockable plug into the port.[3]
The following external links act as an indirect mechanism of further learning on this topic (e.g., detailed descriptions, examples, and implementations).
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https://en.wikipedia.org/wiki/Pod_slurping
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Snarfis a term used by computer programmers and theUNIXcommunity meaning to copy a file or data over a network, for any purpose, with additional specialist meanings to access data without appropriate permission.[1]It also refers to usingcommand linetools to transfer files through theHTTP,gopher,finger, andFTPprotocols without user interaction, and to a method of achievingcache coherencein amultiprocessingcomputer architecture through observation of writes to cached data.
An example of a snarf is theEvil twin attack, using a simple shell script running software like AirSnarf[2]to create a wireless hotspot complete with acaptive portal. Wireless clients that associate to a snarf access point will receive an IP, DNS, and gateway and appear completely normal. Users will have all of their DNS queries resolve to the attacker'sIP number, regardless of their DNS settings, so any website they attempt to visit will bring up a snarf "splash page", requesting a username and password. The username and password entered by unsuspecting users will be mailed to root@localhost. The reason this works is:
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TheFacebook Bluetooth Beaconis a hardwarebeaconreleased byFacebookin 2015. The beacon uses abluetoothconnection to communicate with theFacebook appon the user's smartphone, informing it of the phone's location.[1]The technology allows location-specific advertising to be pushed to the user's Facebook feed.[1]
In June 2015, Facebook gave free beacons to a number of businesses in the United States.[2]
This technology-related article is astub. You can help Wikipedia byexpanding it.
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https://en.wikipedia.org/wiki/Facebook_Bluetooth_Beacon
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Innavigation, aradio beaconorradiobeaconis a kind ofbeacon, a device that marks a fixed location and allowsdirection-findingequipment to find relativebearing. But instead of employingvisible light, radio beacons transmitelectromagnetic radiationin theradio waveband. They are used for direction-finding systems on ships, aircraft and vehicles.[1]
Radio beaconstransmita continuous or periodic radio signal with limited information (for example, its identification or location) on a specifiedradio frequency. Occasionally, the beacon's transmission includes other information, such astelemetricor meteorological data.
Radio beacons have many applications, including air and sea navigation, propagation research,robotic mapping,radio-frequency identification(RFID),near-field communication(NFC) andindoor navigation, as withreal-time locating systems(RTLS) likeSyledisorsimultaneous localization and mapping(SLAM).
The most basic radio-navigational aid used in aviation is thenon-directional beaconor NDB. It is a simple low- and medium-frequency transmitter used to locateairway intersectionsand airports and to conductinstrument approaches, with the use of aradio direction finderlocated on the aircraft. The aviation NDBs, especially the ones marking airway intersections, are gradually being decommissioned and replaced with other navigational aids based on newer technologies. Due to relatively low purchase, maintenance and calibration cost, NDBs are still used to mark locations of smalleraerodromesand important helicopter landing sites.
Marine beacons, based on the same technology and installed in coastal areas, have also been used by ships at sea.[2][3]Most of them, especially in the Western world, are no longer in service, while some have been converted totelemetrytransmitters fordifferential GPS.[4]
Other than dedicated radio beacons, anyAM,VHF, orUHFradio stationat a known location can be used as a beacon withdirection-findingequipment. However stations, which are part of asingle-frequency networkshould not be used as in this case the direction of the minimum or the maximum can be different from the direction to the transmitter site.
Amarker beaconis a specialized beacon used in aviation, in conjunction with aninstrument landing system(ILS), to give pilots a means to determine distance to the runway. Marker beacons transmit on the dedicated frequency of 75 MHz. This type of beacon is slowly being phased out, and most new ILS installations have no marker beacons.
Anamateur radio propagation beaconis specifically used to study the propagation of radio signals. Nearly all of them are part of theamateur radioservice.
A group of radio beacons with single-letter identifiers ("C", "D", "M", "S", "P", etc.) transmitting inMorse codehave been regularly reported on varioushigh frequencies. There is no official information available about these transmitters, and they are not registered with theInternational Telecommunication Union. Some investigators suggest that some of these so-called "cluster beacons" are actually radio propagation beacons for naval use.
Beacons are also used in bothgeostationaryandinclined-orbitsatellites. Any satellite will emit one or more beacons (normally on a fixed frequency) whose purpose is twofold; as well as containingmodulatedstation-keeping information (telemetry), the beacon locates the satellite (determines itsazimuthand elevation) in the sky.
A beacon was left on the Moon by crew ofApollo 17, the last Apollo mission, transmittingFSKtelemetry on 2276.0 MHz[5]
Driftnet radio buoys are extensively used by fishing boats operating in open seas and oceans.[6]They are useful for collecting long fishing lines or fishing nets, with the assistance of aradio direction finder. According to product information released by manufacturer Kato Electronics Co, Ltd., these buoys transmit on 1600–2850 kHz with a power of 4-15 W.
Some types of driftnet buoys, called "SelCall buoys", answer only when they are called by their own ships. Using this technique the buoy prevents nets and fishing gears from being carried away by other ships, while the battery power consumption remains low.[7]
Distress radio beacons, also collectively known asdistress beacons,emergency beacons, or simplybeacons, are thosetracking transmittersthat operate as part of the internationalCospas-SarsatSearch and Rescuesatellitesystem. When activated, these beacons send out adistress signalthat, when detected by non-geostationarysatellites, can be located bytriangulation. In the case of 406 MHz beacons, which transmit digital signals, the beacons can be uniquely identified almost instantly (viaGEOSAR), and aGPSposition can be encoded into the signal (thus providing both instantaneous identification and position).Distress signalsfrom the beacons are homed bysearch and rescue(SAR) aircraft and ground search parties, who can in turn come to the aid of the concerned boat, aircraft or persons.
There are three kinds of distress radio beacons:
The basic purpose of distress radio beacons is to rescue people within the so-called "golden day" (the first 24 hours following a traumatic event), when the majority of survivors can still be saved.[8]
In the field ofWi-Fi(wireless local area networks using the IEEE 802.11b and 802.11g specification), the termbeaconsignifies a specific data transmission from thewireless access point(AP), which carries theSSID, the channel number and security protocols such asWired Equivalent Privacy(WEP) orWi-Fi Protected Access(WPA). This transmission does not contain the link layer address of another Wi-Fi device, therefore it can be received by any LAN client.[9]
Stations participating in packet radio networks based on theAX.25link layer protocol also use beacon transmissions to identify themselves and broadcast brief information about operational status. The beacon transmissions use specialUIorUnnumbered Informationframes, which are not part of a connection and can be displayed by any station.[10][11]Beacons in traditional AX.25 amateur packet radio networks contain free format information text, readable by human operators.
This mode of AX.25 operation, using a formal machine-readable beacon text specification developed by Bob Bruninga, WB4APR, became the basis of theAPRSnetworks.
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https://en.wikipedia.org/wiki/Electric_beacon
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Pseudoliteis a contraction of the term "pseudo-satellite," used to refer to something that is not asatellitewhich performs a function commonly in the domain of satellites. Pseudolites are most often smalltransceiversthat are used to create a local, ground-basedGlobal Positioning System(GPS) alternative. The range of each transceiver's signal is dependent on the power available to the unit.
Being able to deploy one's own positioning system, independent of the GPS, can be useful in situations where the normal GPS signals are either blocked/jammed (military conflicts), or simply not available (exploration of other planets).
Pseudolites are normally used to augment the GPS by improvingdilution of precision(DOP). Or pseudolites are also used to implement GPS-like indoor location systems, where pseudolites are acting as GPS satellites. Pseudolites use cheap voltage controlled oscillator, so pseudolite based location system shall provide a methodology to compensate clock differences among pseudolites.
For planetary exploration, research being conducted at facilities includingNASA'sAmes Research CenterandStanford University(see link at bottom) may allow a rover to deploy an array of pseudolites with no particular accuracy and still calibrate the system to centimeter-level resolution without human assistance. This would aid a rover's path-finding routines and increase the safe maneuvering speed of the unassisted vehicle. The concept is sometimes referred to as a Self-Calibrating Pseudolite Array (SCPA).
Other applications of pseudolite arrays include precision approach landing systems for aircraft and highly accurate tracking of transponders.
Pseudolites have started to gain more and more attention in the context of indoor location.[1][2]
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https://en.wikipedia.org/wiki/Pseudolite
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