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890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.1.1 Ghost Cancellation Reference (GCR) | This waveform to ITU-R BT 1124 Systems C and ETS 300 732 [7] is carried on line 318. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.1.2 Wide Screen Signalling (WSS) | As this is carried on the first half of line 23, it does not fall within the strict definition of the VBI. This signal to ETS 300 294 [6] occupies only the first half of the line the remainder being active picture. TR 101 233 V1.1.1 (1998-02) 8 |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.1.3 Video Programming System (VPS) | This is a bi-phase modulation with a data rate of 2,5 Mbit/s on line 16 used for the record function of some Programme Delivery Control (PDC) systems (see ETS 300 231[3]). |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.2 Frequently used signals | |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.2.1 Test signals | The standard test signals used by broadcasters are based on ITU-R Recommendation 473 [8] and ITU-R Recommendation 567 [9] which describe many elements of test signals. There is also EBU Recommendation R 26-1981 [10] which recommends the use of ITU-R Recommendation 473 [8]. These standard test signals are generally repetitive on the two fields and are often on lines 17/330, 18/331 and 19/332 or 19/332 and 20/333. The elements of these waveforms usually include: a) luminance bar at 100 %; b) 2T pulse; c) T pulse or 20T pulse; d) chrominance bar on a luminance pedestal; e) luminance step/stair case; f) luminance step/stair case with superimposed chrominance; g) luminance saw-tooth; h) luminance saw-tooth with superimposed chrominance; i) colour bars. In addition there are test signals which include a frequency sweep and a (sin x)/x waveform. These waveforms are used to assess the quality of the transmitted signal. Action can be taken automatically for instance to adjust the equalization of a radio link or rebroadcast signal or to change over to a standby feed. As such, these signals are very important to the broadcaster or public telecommunications operator and often test signals will be constructed to meet specific needs. It is desirable that any new signals are constructed and transmitted to have no effect on Teletext decoders. This may be achieved by ensuring that there is no part of the waveform which a Teletext decoder may interpret as valid Teletext framing code in the presence of noise. It should be noted that some existing decoders will accept a single bit error in the framing code and have a framing code acceptance window which is considerably wider than the transmission limits defined in the present document. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.2.2 Quiet lines | The measurement of random noise by receivers and by public telecommunications operators and broadcasters is normally made on a quiet line. As many existing Teletext decoders cannot decode line 6/319, one or both of these lines is often used for noise measurement. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.2.3 Encryption systems | Many broadcasters encrypt their signals and the control of the decrypting systems is carried in the unencrypted VBI. These systems which are entirely proprietary, can occupy a number of VBI line pairs. For example Videocrypt can be interpreted as valid Teletext by some existing decoders under some circumstances, resulting in corrupted displays. TR 101 233 V1.1.1 (1998-02) 9 |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.2.4 Teletext broadcasting | This is packet based broadcasting that conforms to ETS 300 706 [1] or ETS 300 708 [2]. Teletext decoders should be designed to be insensitive to non-Teletext waveforms. It is reasonable to assume that on a given channel the type of waveform on a given line will remain constant for one session of viewing. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.3 Signals that are infrequently used | |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.3.1 Teletext-like data broadcasting | Certain forms of data broadcasting and other private data can be carried by a Teletext based waveform that does not fully comply to ETS 300 706 [1] or ETS 300 708 [2]. This can be generated by using a different framing code or inverting the data. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.3.2 Non-Teletext data broadcasting | There are a number of proprietary data broadcasting systems which do not use a Teletext - like waveform. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.3.3 Closed captioning | This is a derivative of the closed caption system to EIA 608 (Line 21 Data services for NTSC) used in North America on line 21/334. In Europe this signal is used for internal purposes by some satellite broadcasters, not for general reception in the home, usually on line 22/335. This is also known as NCI (National Captioning Institute) caption. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 5.3.4 Vertical interval time code | Broadcasters may inadvertently broadcast this internal signal which is recorded on video tape on lines 19/332 and 21/334. This may occur because the picture has been processed and has slipped by a few lines. In some countries lines 9/322 and lines 22/335 are used for this purpose. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 6 Principles applied to the allocation of services to lines | The broadcasters, regulatory authorities and the common carriers of information such as public telecommunications operators, cable and satellite operators lay down the requirements for the signals in the VBI. Over some years, there has been a general movement to rationalize the use of the VBI, usually to maximize the number lines carrying Teletext. As there are many differing requirements, it has been impossible to get international agreement to any particular arrangement or use of groups of lines. However, there are a few basic trends which broadcasters tend to follow when allocating VBI capacity. Because the use of the VBI has grown over the years from the early arrangement of test signals on lines 17/330, 18/331, 19/332 and 20/333, there are usually seen to be four main areas: 1) top of VBI - Line 318 is either blank or carries the GCR signal to ITU-R BT 1124 System C further specified in ETS 300 732 [7]. - Lines 6/319 should be used for quiet lines or test signals, because not all exiting Teletext decoders can accept on these lines. It is strongly recommended that one or both of these lines are used for noise measurements. 2) middle/majority of VBI - From Lines 7/320 to about line 18/331, there is likely to be Teletext or encryption systems or other non-Teletext data broadcasting. In some countries Teletext or Teletext - like data broadcasting or other non-Teletext data broadcasting is inserted only up to lines 16/329. VPS is located on line 16. TR 101 233 V1.1.1 (1998-02) 10 3) test signals - Lines 19/332 and 20/333 tend to be used for test signals but are also used for Teletext. In some countries lines 17/330, 18/331 and 19/332 are used for test signals. 4) close to picture - Lines 21/334 and 22/335 tend to be used for programme related information, such as Teletext subtitles (In magazine parallel transmission) or closed captioning. It is very likely that Teletext or test signals may also appear here. In some countries also lines 20/333 are used for Teletext. Because of the way in which a Teletext service may require certain numbers of VBI lines for efficient transmission, typically 12 line pairs, there may be strong commercial incentives to use 12 VBI lines before the ITS which may mean that Teletext is on line 16/329. Similarly, certain decoders may window over only 16 line pairs. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7 Allocation of Teletext services | There can be many Teletext services in the VBI; each of which may be operated by one or several service providers. The main categories are given in table 1. Table 1: Allocation of Teletext services Service Packets Specification Text services X/0 to X/29 ETS 300 706 [1] Page based data broadcasting packets X/0 to X/29 ETS 300 708 [2] Independent data broadcasting 8/31, 1/31, 2/31, 3/31 ETS 300 708 [2] Audio data 4/30 and 4/31 ETS 300 708 [2] Packet 8/30 format 1 ETS 300 706 [1] Packet 8/30 format 2 ETS 300 231 [3] VPS ETS 300 231 [3] In addition, ETR 287 [4] and ETR 288 [5] provide an insight into the application of the specifications and the organization of Teletext transmission. Within the lines allocated to Teletext there tends to be an allocation of data broadcasting, both page based and independent packet, onto the lower line numbers. This is because a few existing Teletext text decoders may malfunction if there are packets X/31 on the highest line numbers in each field used for Teletext. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.1 Teletext text transmission | As these services usually form the major part of the Teletext service, a brief outline of what may be transmitted may help. There are three main groups of Teletext text transmission: 1) magazine serial mode; 2) magazine parallel mode; and 3) complex mode. TR 101 233 V1.1.1 (1998-02) 11 |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.1.1 Magazine serial mode | Quote from annex B of ETS 300 706 [1]: "In a transmission multiplexed with a video signal, it is likely that each page will be transmitted on the maximum number of VBI lines available, and all the pages from all magazines will be transmitted one after the other, although not necessarily in numerical sequence". The large number of filler packets are very often transmitted (to comply with the 20 ms rule) may be replaced by data broadcasting, or text enhancement data which does not obey the 20 ms rule. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.1.2 Magazine parallel mode | This method gives the editor greater control over the cycle times of pages in different magazines and a greater transmission efficiency. The basic operation can be enhanced to give an even more efficient transmission with no packet containing unused filler data. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.1.2.1 Simple parallel operation | Quote from annex B of ETS 300 706 [1]: "In a transmission multiplexed with a video signal, it is likely that pages from one or more magazines will be allocated to groups of VBI lines for transmission. Thus a single VBI can consist of packets from a number of different magazines. Pages within each magazine need not be transmitted in numerical sequence". This method enables different sources of Teletext to be combined easily and is in any case more efficient to transmit. Thus a line or groups of lines will be allocated to a particular service; for instance data broadcasting or subtitles. Any filler packets transmitted (to comply with the 20 ms rule) may be replaced by data broadcasting, or text enhancement data which does not obey the 20 ms rule. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.1.2.2 Complex transmissions | These methods are usually: - based on a magazine parallel mode of text transmission and aim to remove "ALL" filler packets from the VBI; - dynamically allocating between services or magazines on a VBI by VBI basis; - by altering the number and type of packets X/0 to X/29 within the VBI with other packets transmitted. Even more complex services which are known under trade names such as "Super spiral" and "IPP" can organize the VBI on a super streamed or even individual packet basis. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.2 Data broadcasting | |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.2.1 Page based | This can be considered as being similar to the normal text or enhancement data in a text transmission. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.2.2 Independent | These are independent packets of data which do not have any affinity for a particular page or magazine. Thus they are a very efficient way of sending information as within a Teletext multiplex. They can be added or subtracted from the Teletext multiplex very easily as they are independent of all other elements. TR 101 233 V1.1.1 (1998-02) 12 |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.2.3 Audio data | This may be used by broadcasters to provide an "AUDETEL" audio description of television service (packet 4/30) or as an independent sound channel (packet 4/31). |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.3 Packet 8/30 format 1 | If this packet is transmitted, it should be in the VBI following the Universal Time Co-ordinated (UTC) second boundary. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.4 Programme Delivery Control (PDC) 8/30f2 | In Teletext this uses packet 8/30 format 2. Packet 8/30s shall be transmitted with at least 200 ms between them. It is usual for them to be transmitted at the 200 ms boundary, but there is no requirement for them to be transmitted in LCI order or to allocate a particular time slot for the LCI. For non-Teletext VPS method (line 16) see subclause 5.1.3. |
890633305f5cc56e514b089b1797c1f3 | 101 233 | 7.5 Allocation summary | 6 7 8 9 1 0 1 1 1 2 13 1 4 1 5 16 1 7 1 8 19 2 0 21 23 2 4 6 22 3 10 p o ssible T elete xt D ata-L in e s Multip lexed M o de fie ld -blan kin g Int e rval (25 lines) 318 3 19 320 32 1 32 2 32 3 32 4 3 2 5 32 6 3 2 7 328 32 9 33 0 33 1 3 3 2 3 33 3 34 3 3 5 2 2 ( VBI ) Figure 2: Usable TV lines, when multiplexed with a CVBS signal TR 101 233 V1.1.1 (1998-02) 13 Table 2: Allocation of services in the Vertical Blanking Interval (VBI) LINE VPS wss test quiet encryption Teletext text Teletext data Teletext like non Teletext closed captioning VITC 6 ¥ l l 7 H H 8 H H 9 H H L L 10 H M L L 11 H H M L L 12 H H M L L 13 H H M L L 14 H H M L L 15 H H M L L 16 S H H M L L 17 ¥ H H M L L 18 ¥ H H M L L 19 ¥ M L B 20 ¥ M L B 21 H H M B 22 H H M B B 23 S GCR 318 S 319 ¥ M M 320 H H 321 H H 322 H H L L 323 H M L L 324 H H M L L 325 H H M L L 326 H H M L L 327 H H M L L 328 H H M L L 329 H H M L L 330 ¥ H H M L L 331 ¥ H H M L L 332 ¥ M B 333 ¥ M B 334 H H M B 335 H H M B B Key: S = Specified in a standard H = Highly likely to be used M = Medium likelihood of usage L = Low use of usage B = Broadcasters usage ¥ = Test waveform TR 101 233 V1.1.1 (1998-02) 14 Annex A (informative): Examples of VBI allocation There are many factors which require to be considered when allocating the VBI to services. The whole transmission path from the broadcaster to the home should be considered as the common carriers may have their own restrictions or may bridge Teletext onto different lines. Given freedom to decide the allocation of the VBI, the following method may be followed. 1) The first is to allocate those services which require a fixed line: GCR line 318, VPS line 16, WSS line 23. NOTE: Only VPS occupies key space within the VBI. 2) Then allocate the lines to be used by test signals and quiet lines. - These are usually fixed by convention to be test signals on lines 17/330, lines 18/331 and lines 19/332 or on lines 19/332 and lines 20/333 with the quiet lines being at least lines 6/319. - As these signals are usually close to picture, they often form a dividing line in the VBI. 3) Then allocate any other signal which shall be on a fixed line; such as encryption or other non-Teletext waveforms. - It may be that some of these signals are placed on line close to the picture, thus freeing a contiguous group of lines from the top of the VBI to the test signal lines. This may give a skeleton allocation like in table A.1. Table A.1 Allocation method Line Line specific Other signals Teletext Teletext Other signals Line specific Line GCR 318 6 Quiet Quiet 319 7 Data Data 320 8 Text Text8/30 321 9 Text Text 322 10 Text Text 323 11 Text Text 324 12 Encryption Encryption 325 13 Encryption Encryption 326 14 Encryption Encryption 327 15 Encryption Encryption 328 16 VPS 329 17 Text Text 330 18 Text Text 331 19 Test Test 332 20 Test Test 333 21 Text Text 334 22 Text Text+sub 335 23 WSS Picture The remainder of the lines can be used for Teletext. The efficient use of these lines is a complex topic, depending on the number of transmitted packets per page, enhancement data or data broadcasting. An introduction to the key issues can be found in ETR 288 [5]. With parallel transmission mode the number of lines or line pairs allocated for each stream shall also be considered. It is worthwhile using a Teletext packet analyser to check the use of the Teletext lines; particularly if magazine parallelmode is being used. TR 101 233 V1.1.1 (1998-02) 15 Annex B (informative): Example of test signal construction This example uses line 21 and 335 for a test signal to provide all the elements of a test waveform required but only using one line pair. Lines 21/335 were selected to maximize the amount of space available for Teletext services, whilst leaving a blank line pair 22/335 for the use of test signals on point-to-point links in the TV distribution system. The first part of the test waveform is identical on both lines 21 and 335, so that they can be viewed on a simple waveform monitor/oscilloscope: - 10 µs luminance bar (ITU-R Recommendation 567 [9], B2); - 2T sine squared pulse (ITU-R Recommendation 567 [9], B1); - 10T composite pulse (similar to ITU-R Recommendation 567 [9], F); then on line 21: - a five riser staircase with 140 mV superimposed chroma (similar to ITU-R Recommendation 567 [9], D2); and on line 334: - 700 mV peak-to-peak chrominance bar on a 350 mV pedestal (similar to ITU-R Recommendation 567 [9], G1); - 68 bits of data as 200 ns sine squared 462 mV pulses. TR 101 233 V1.1.1 (1998-02) 16 History Document history V1.1.1 February 1998 Publication ISBN 2-7437-1940-0 Dépôt légal: Février 1998 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 1 Scope | The present document describes a Common Reference Model for Broadband Radio Access Networks (BRAN) supporting ATM, also know as Wireless ATM Access Systems (WACS). WACS provide wireless local and remote access to ATM networks. In the ETSI BRAN Project, the scope of the standards for such specific systems is limited to the air interface, the service interfaces of the wireless subsystem, interworking functions for specified user and network interfaces, and supporting capabilities required to realize these services. The air interface and the interworking functions for HIPERLAN/2 provide multi-vendor interoperation capabilities at the air interface and at those supported network interfaces. Interfaces and protocols between the signalling functions in ATM terminal devices and the signalling functions in the ATM switch are outside the scope of BRAN, but may be in the scope of the present document where they relate to radio mobility. The following describes a reference model to be used as basis for the development of a set of functional standards for WACS. It should be noted that for many purposes, there is no need to distinguish between WACS compliant systems serving mobile user nodes and those serving stationary access nodes. In the latter case, the same node may be visible to more than one access point and the radio link conditions may require a "handover" in order to maintain communications in changing radio environments. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 2 References | The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. [1] CEPT Recommendation T/R 22-06: "Harmonised radio frequency bands for High Performance Radio Local Area Networks (HIPERLANs) in the 5 GHz and 17 GHz frequency range". [2] TR 101 031: "Radio Equipment and Systems (RES); HIgh PErformance Radio Local Area Network (HIPERLAN); Requirements and architectures for Wireless ATM Access and Interconnection". [3] ITU-T Recommendation Q.2931 (1995): "Digital Subscriber Signalling System No. 2 (DSS 2) – User-Network Interface (UNI) layer 3 specification for basic call/connection control". [4] ITU-T Recommendation I.356 (1996): "B-ISDN ATM layer cell transfer performance". [5] ATM Forum (April 1996): "Traffic Management Specification Version 4.0". [6] ATM Forum (July 1996): "ATM User-Network Interface (UNI) Signalling Specification Version 4.0". [7] ATM Forum (September 1996): "Integrated Local Management Interface (ILMI) Specification Version 4.0". [8] ATM Forum (March 1996): "Private Network-Network Interface (PNNI) Specification Version 1.0". [9] ATM Forum (1994): "ATM User-Network Interface (UNI) Specification Version 3.1". ETSI TR 101 378 V1.1.1 (1998-12) 6 [10] ITU-T Recommendation G.902 (1995): "Framework Recommendation on functional access networks (AN) - Architecture and functions, access types, management and service node aspects". [11] TR 101 054 (V1.1): "Security Algorithms Group of Experts (SAGE); Rules for the management of the HIPERLAN Standard Encryption Algorithm (HSEA)". [12] ISO/IEC 7498-1: "Information technology - Open Systems Interconnection - Basic Reference Model: The Basic Model". [13] ISO/IEC DIS 8802-11: "Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications". [14] ISO/IEC 15802-1: "Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Common specifications - Part 1: Medium Access Control (MAC) service definition ". [15] ISO/IEC 8802-2: "Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 2: Logical link control". |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 3 Definitions and abbreviations | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 3.1 Definitions | For the purposes of the present document, the following terms and definitions apply: [Local] access: this term is used in the telecommunications sense: short-range (less than 100 m) wireless access to other, possibly wired, networks. [Remote] access: this terms is used in the telecommunications sense: long-range (up to 10 km) wireless access to other, possibly wired, networks. Remote access networks are also referred to as "local loop networks," although the use of this term is deprecated by ITU. [WACS] access point: a device controlling a single wireless subnetwork. association: a radio sub-system binding between a WACS Node and a WACS AP. BRAN family: this currently comprises the HIPERLAN/2, HIPERACCESS and HIPERLINK systems. data confidentiality: provisions for the protection of transmitted data from observation by unauthorized stations or other monitoring means. One measure for doing that is to implement encryption. Data Link Control (DLC): layer 2 of the ISO/OSI reference model [12]. The DLC layer consists of the medium access control (MAC) and logical link control (LLC) sublayers. downlink: the incoming data direction from a WACS Terminal Adapter perspective. end-user Mobility-supporting ATM Switch (EMAS): ATM switch enhanced to support mobile users. encryption: a means of obtaining data confidentiality (see also data confidentiality). handover: the changing of the path over which information flows within or across the wireless ATM subsystem, without releasing the connection. HIPERACCESS: HIgh PErformance Radio ACCESS network. HIPERLAN/2: HIgh PErformance Radio Local Access Network. HIPERLINK: HIgh PErformance Radio network LINK. ETSI TR 101 378 V1.1.1 (1998-12) 7 interworking: interaction between dissimilar subnetworks, end systems, or parts thereof, providing a Functional Element capable of supporting end-to-end communications. Local Area Network (LAN): a group of user stations each of which can communicate with at least one other using a common transmission medium commonly managed. Logical Link Control (LLC): ISO/IEC 8802-2 layer [15] between the network layer and the MAC layer of the ISO/IEC DIS 8802-11 reference model [13]. The LLC sublayer maintains the quality of service on a virtual circuit basis. Depending on the type of service provided and channel quality, capacity and utilisation, the LLC layer may implement a variety of means including FEC, ARQ and flow pacing to optimise the service provided to the (DLC) user. MAC Service Data Unit (MSDU): the fundamental unit of data delivery between MAC entities. See Service Data Unit (SDU). Medium Access Control (MAC): ISO/IEC 15802-1 layer [14] of the ISO/IEC DIS 8802-11 reference model [13] between the PHY and the LLC. The MAC sublayer implements a service policy, i.e. allocation of resources to virtual circuits and terminals, that takes into account such factors as channel quality, number of terminal devices and medium sharing with other wireless subnetworks. [WACS] node: a grouping comprizing a WACS Terminal and a WACS Terminal Adaptor. Protocol Data Unit (PDU): data unit exchanged between entities at the same ISO layer. Physical Layer (PHY): layer 1 of the ISO/OSI reference model [12]. The mechanism for transfer of symbols between HIPERLAN/2 nodes. registration: a binding between a WACS Node and the external network which enables that network to route connections to the WACS Node. Service Data Unit (SDU): data unit exchanged between adjacent ISO layers. [WACS] terminal: the functional components of a WACS Node that contains the end-user application. [WACS] terminal adapter: the functional components of a WACS Node that provide the wireless communications services and the related control functions. Wireless ATM Access System (WACS): ATM specific wireless access subsystem. uplink: the outgoing data direction from WACS Terminal Adapter perspective. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 3.2 Abbreviations | For the purposes of the present document, the following abbreviations apply: AAL ATM Adaptation Layer ABR Available Bit Rate ACF Association Control Function AP Access Point APC Access Point Controller (equivalent to the ATMF AP) APCF Access Point Control Function APT Access Point Transceiver (equivalent to the ATMF Radio Port) ARQ Automatic Repeat reQuest ATM Asynchronous Transfer Mode ATMC ATM Connection BRAN Broadband Radio Access Network CAC Connection Admission Control CAP Combined EMAS/AP CBR Constant Bit Rate CC Connection Control CCF Call control and Connection control Function CDVT Cell Delay Variation Tolerance CEPT European Conference of Postal and Telecommunications Administrations DLC Data Link Control (layer) ETSI TR 101 378 V1.1.1 (1998-12) 8 EMAS End-user Mobility-supporting ATM Switch ETSI European Telecommunications Standards Institute FE Functional Element FEC Forward Error Correction IEC International Electrotechnical Committee ILMI Integrated Local Management Interface IMF Identification Management Function ISO International Standards Organisation ITU-T International Telecommunications Union (Telecommunications Division) LAN Local Area Network LLC Logical Link Control (layer) LME Layer Management Entity MAC Medium Access Control (layer) MMF Mobility Management Function MSDU MAC Service Data Unit M-NNI Mobility-enhanced NNI M-UNI Mobility-enhanced UNI NNI Network-to-Network Interface OSI Open Systems Interconnection QoS Quality of Service PHY Physical (layer) PDU Protocol Data Unit RF Radio Frequency RRC Radio Resource Control RTR Radio Transmission and Reception SCF Service Control Function SDU Service Data Unit SMF Security Management Function TA Terminal Adaptor TR Technical Report UBR Unspecified Bit Rate UNI User-Network Interface VBR Variable Bit Rate VBR-RT Real-Time Variable Bit Rate VBR-NRT Non-Real-Time Variable Bit Rate VCI Virtual Channel Identifier VPC Virtual Path Connection VPI Virtual Path Identifier WACS Wireless ATM Access System WCS Wireless Convergence Sublayer |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 4 Wireless ATM Access Systems (WACS) | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 4.1 Services | WACS shall provide the following services: • connection set-up in accordance with ATM signalling specifications. These are [3], UNI3.1 [9], UNI4.0 [6], or evolved equivalents. Outgoing and incoming connections shall be supported. Device addressing shall be consistent with world-wide roaming; • releasing incoming connections and outgoing connections; • unit data transfer; • indication of changing capacities due to changes in the radio environment. Note that this does not and should not imply resource re-negotiation at the ATM or higher levels. ETSI TR 101 378 V1.1.1 (1998-12) 9 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 4.2 Supporting capabilities | WACS shall provide the following capabilities in support of the above services: • traffic management to maximize adherence to QoS parameters established at connection set-up; • association of WACS nodes to WACS Access Points; • informing the ATM switch of the changes in the population of associated nodes; • monitoring of radio conditions; • support for power conservation (sleep mode); • dynamic allocation of radio link capacity to ensure adherence to the negotiated traffic contract [4], [5]; • radio link encryption (optional). |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 4.2.1 Security | Users of WACS systems may require protection of their transmissions from being listened to by other users operating possibly co-located wireless subnetworks. This requires the implementation of a data confidentiality service. The level of protection provided should be consistent with the protection provided by wired systems that do not implement a data confidentiality service. Further, the cryptographic algorithm shall not be subject to export controls and therefore allow world-wide use. The WACS standard shall include optional functions for the selective use of encryption and for the synchronization of the use of cryptographic keys between nodes of a WACS. NOTE: ETSI has developed a cryptographic algorithm for HIPERLANs, the HIPERLAN Standard Encryption Algorithm. For obtaining this algorithm, see [11]. This algorithm is designed to operate at 20 Mbit/s or greater and is available to ETSI members under a Confidentiality Agreement. The negotiation of cryptographic algorithms, and key exchanges take place either during the association phase or in a second phase (optimally directly following association). |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 5 WACS reference model | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 5.1 Reference models for HIPERLAN/2 | Specifications for two Reference Models, termed the Distributed and the Unified Control Model respectively will be developed. The radio interface as specified by BRAN should be the same for both models. The WACS Reference Models identify the main groups of functional elements and their reference points. These groups are further decomposed in figures 1 and 2. The functional elements are: • the WACS Node which consists of the WACS Terminal and WACS Terminal Adapter (WACS-TA); • the WACS Access Point (WACS-AP), which can be decomposed into an Access Point Controller (APC) controlling one or multiple Access Point Transceivers (APT); and • the End-user Mobility-supporting ATM Switch (EMAS). NOTE 1: In the case of the Unified Control Model, the Access Point and the End-user Mobility-supporting ATM Switch are combined into a single Combined EMAS/AP (the CAP) with an internal interface. The BRAN specifications will describe by default the Distributed Control Model, since the Unified Control Model is a simplification of the Distributed Control Model. In fact, the Unified Control Model can be derived from the Distributed Control Model by making interface W.2 an internal interface (WI.3). The Distributed Control Model additionally provides methods to facilitate intra-AP handover. ETSI TR 101 378 V1.1.1 (1998-12) 10 NOTE 2: These two reference models not necessarily means physical implementation, but the specification of reference points and the respective protocols make a physical realization possible. WACS - Terminal WACS - TA WACS - AP Controller End-user Mobility Supporting ATM switch External Network WACS Node WACS - Access Point Wireless ATM Subsystem W.2 WI.1 WI.2 W.1 WACS - AP Tranceiver R.1 Figure 1: Distributed Control Model WACS - Terminal WACS - TA WACS - AP Controller End-user Mobility Supporting ATM Switch External Network WACS Node WACS – Combined EMAS/AP Wireless ATM Subsystem WI.3 WI.1 WI.2 W.1 WACS - AP Tranceiver R.1 Figure 2: Unified Control Model |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 5.2 Reference model for HIPERACCESS | In both cases above, the WACS Node is shown as an integrated unit with an internal interface (WI.1). This may not always be the case, for example, in HIPERACCESS systems, the WACS Terminal Adapter typically is provided with a physical interface for a user to attach a terminal or network. This interface is identified in table 1, subclause 5.3 as W.3. In this case the WACS Terminal Adapter terminates WACS specific protocols; it presents a user-network interface to the WACS user via an interworking function. In this application, the use of switching in the combined EMAS/AP is in contravention to the requirements of [10]. Amongst other reasons, the need in a telecommunications access network to allow for reliable billing to the customer for services used, motivates this requirement. Therefore the reference model for HIPERACCESS systems should normally be based on the Distributed Control variant of the WACS Reference Model. For the purpose of achieving a high degree of radio coverage a repeater may be present at the W.1 reference point. ETSI TR 101 378 V1.1.1 (1998-12) 11 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 5.3 Reference points | The WACS Reference Model includes following reference points, some of which are subject to standardization (see table 1). Table 1: Reference points Reference point Description Details and/or Comments W.1 The radio interface. This reference point comprises: - The WACS DLC protocol supporting transparent ATM transport (User, Control and Management plane traffic) as well as mobility and security support functions such as access point acquisition and association and establishment of security contexts to facilitate radio link encryption; - the UNI protocol - with mobility enhancements according to ATMF implementation agreements; and - optionally the ILMI protocol [7]. W.2 Interface between the Access Point and the End-user Mobility-supporting ATM Switch and its management and control functions. The reference point comprises: - The WACS Access Point Control Protocol that carries the interactions between the AP and the End-user Mobility-supporting ATM Switch for the establishment and releasing of connections, for connection handover between APs and related purposes. The specification of this protocol depends on the function distribution between Access Point and End-user Mobility-supporting ATM Switch. W.3 Interface between terminal equipment and WACS Terminal Adapter for HIPERACCESS. This interface is a standard UNI interface and it is outside the scope of the present document. Note that this interface is not shown in any diagram in the present document. R.1 Standard Interface between the EMAS and the external network, e.g., (M-)UNI or (M-)NNI. This interface is a standard interface and it is outside the scope of the present document. Enhancements to support terminal mobility may be included into this interface. WI.1 Internal interface of the WACS Node. This interface is not described in the present document. It is a proprietary interface. WI.2 Internal interface of the WACS Access Point. This interface is not described in the present document. It is a proprietary interface. WI.3 Internal interface of the Combined EMAS/AP. This interface is not described in the present document. It is a proprietary interface. A complete description of the distribution of functions across the elements of the model is needed to assure alignment with other standards, e.g. those developed by the ATM Forum for signalling and management enhancements to the basic ATM interface specifications. This description is given in the following sections. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6 Functional architecture and elements | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.1 Functional architecture | The main objective of the functional architecture is to define a flexible system with a wireless specific elements separated from the standard wireline specific connection control elements. The separation should allow standard Connection Control (CC) functions, such as [3] or UNI3.1/4.0, to exist as such in the higher protocol layers while they only have a clearly defined interface for the wireless sub-system. It should be noted that some mobility and authentication related functions and information, is also present in the higher protocol layers, e.g. ILMI, that describe the terminal / switch interaction. ETSI TR 101 378 V1.1.1 (1998-12) 12 The Distributed reference model defines Connection Control end points in the WACS Node and End-user Mobility- supporting ATM Switch (see figure 3). The AP is transparent to connection control signalling ([3] or UNI3.1/4.0). The AP will behave as an ATM level bridge/multiplexer (VPC cross-connect) with additional functions supporting Connection Admission Control and hand-over decision making by the EMAS. These additional functions require a specific protocol. This approach allows the wireless specific functions to be kept within the radio sub-system while keeping the connection control end point as in the standard ATM switch. The Unified Reference Model defines Connection Control end points in the WACS Node and Combined EMAS/AP (CAP) (see figure 4). The protocol between WACS Node and CAP will include (M-)UNI and a set of wireless specific messages. The exact content of these wireless specific messages will depend on the level of mobility supported. The interface between WACS combined EMAS/AP and external network may be a standard NNI interface (e.g. PNNI [8]) or M-NNI which supports mobility as will be defined by the ATM Forum. The functional model here is sufficient for the purposes of the present document. However, it is recognized that functional elements like the MMF may be further decomposed or distributed over other functional elements. ATMCT RRCT RTRT RRC RTR SCF SMF MMF CCF Inf. 1 Inf.2 Inf.3 Inf.4 WACS Node Network Side ACF ACFT ATMC ATMC APCF APCF : logical interface : physical interface WACS AP EMAS Inf.7 Inf. 5 External network Inf.A IMF CCFT MMFT Figure 3: WACS Functional Architecture - Distributed Control Inf.2 Inf.3 Combined EMAS/AP Network Side Control function : logical interface : physical interface WACS Node Inf.4 Control function Inf. 5 External ATM network MMF CCF SMF SCF ATMC ACF RRC RRCT ATMCT ACFT RTRT RTR Inf. 1 Inf.A IMF MMFT CCFT Figure 4: WACS Functional Architecture - Unified Control ETSI TR 101 378 V1.1.1 (1998-12) 13 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2 Functional elements | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1 WACS Node side | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.1 IMF (Identification Management Function) | IMF provides the means to identify the WACS Node. This FE includes functions to: • store identification information (e.g. subscription, service, identity), location management related information and security related information; • support authentication on the WACS Node side (e.g. calculation of authentication response); and • provide service related processing and local service control required on the WACS Node side. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.2 MMFT (Mobility Management Function - WACS Node side) | MMFT is used for all mobile terminal related mobility actions. MMFT supports all mobile specific functions on the WACS Node side, e.g. location update initiation, paging response and network information monitoring and analysis. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.3 CCFT (Call control and Connection control Function - WACS Node side) | CCFT is used for connection set-up/release as in the standard ATM network. The function is per connection entity and CCFT uses signalling to setup, control and release connections. Since handover is closely related to CCFT, the ATM handover control messages could be added into standard UNI signalling. CCFT handles the WACS Node side of access control and call and connection control (e.g. [3] or UNI 3.1/4.0) and is responsible for initiating functional requests including QoS requests from the user or other functional entities. It includes: • establish, maintain, modify and release calls and connections; • call control adaptation between the wireless subnetwork and the external network (if necessary); and • control functions to establish, maintain, modify and release ATM connections in the ATMCT (WACS Node ATM Connection) Function Element. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.4 ACFT (Association Control Function - WACS Node side) | ACFT provides control functions for association of the WACS Node to the WACS AP. This FE includes: • control functions for establishment and release of the association between the WACS Node and the wireless subnetwork, i.e. association to establish the first wireless link activity as the WACS Node enters the wireless subnetwork; • support intra-AP handover procedures; • radio handover execution; • paging response detection and handling; • radio access information monitoring and analysis including link maintenance information; and • power saving/conservation. ETSI TR 101 378 V1.1.1 (1998-12) 14 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.5 RRCT (Radio Resource Control function - WACS Node side) | RRCT handles the WACS Node side of radio connection including: • selection, reservation and release of radio resources as required from the communication control plane; • radio channel supervision; • local radio environment reporting (if WACS Node-side assisted or WACS Node-side controlled handover); • handover triggering (if WACS Node-side controlled handover); and • radio access information monitoring and analysis. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.6 RTRT (Radio Transmission and Reception - WACS Node side) | RTRT handles the radio transmission and reception at the WACS Node side. It includes Logical Link Control (LLC), Medium Access Control (MAC) and Radio physical layer related (Radio PHY) functions. DLC functions (LLC and MAC) provide bearer services for ATM connections on U-plane and C-plane and control channels between the WACS Node and the wireless subnetwork. This includes: • error control functions to improve wireless specific transmission impairment (e.g. ARQ by error detection and re- transmission, and/or forward error correction coding and decoding); • multiplexing and de-multiplexing of logical channels; • mechanisms to share radio channels; • ciphering and deciphering; and • service requesting and service granting. Radio PHY function includes: • RF generation, emission, and reception; • scramble and descramble; • baseband channel multiplexing and demultiplexing; • modulation and demodulation; • radio channel quality measurement; • micro diversity relevant functions (e.g. antenna diversity, multipath diversity); and • RF power setting. DLC management functions include: • buffer traffic contracts; and • buffer link performance data. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.1.7 ATMCT (ATM Connection function - WACS Node side) | This ATMCT function connects, maintains, modify and releases ATM connections and provides ATM bearer services for C-plane and U-plane to connect the end user device, i.e., ATM terminal. It may support ATM layer and AAL functions for C-plane and/or U-plane. ATMCT controls the ATM connection elements to provide ATM services (e.g. CBR, VBR-RT, VBR-NRT, ABR and UBR). ETSI TR 101 378 V1.1.1 (1998-12) 15 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2 Network side | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.1 SCF (Service Control Function) | SCF provides service related control functions. SCF handles storage and access to service such as service profile and provides consistency checks on data. SCF contains the service logic and service related processing required on the network side and provides overall service control. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.2 MMF (Mobility Management Function) | MMF is used for all network side related mobility actions. MMF contains the control logic for location and mobility management, i.e. location management function to track the mobile user within the customer premizes area, and handover related function, where handover activities could be invoked by CCF through the standard UNI signalling, or via ACF using the Access Point Control Protocol. It also handles storage and access to location data and may store subscriber identity and provide consistency checks on data. This FE also includes: • paging control (e.g. initiating paging, process paging response); • location management and routing control; • location updating; • store mobility related data; and • store subscriber identity data, if necessary. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.3 SMF (Security Management Function) | SMF contains security related functions, e.g.: • store authentication data, e.g. security related parameters; • perform identity, i.e. registered users/terminals management; • subscriber verification; • subscriber authentication and authentication processing including ciphering; and • confidentiality control. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.4 ACF ( Association Control Function) | ACF provides control functions for association of the WACS Node to the WACS AP. This FE includes: • control functions for establishment and release of the association between the WACS Node and the wireless subnetwork, i.e. association to establish the first wireless link activity as the WACS Node enters the wireless subnetwork; • support intra-AP handover procedures; • radio access information monitoring and analysis including link maintenance functions; • radio handover execution; • identify the AP used by a (portable) WACS Node to access the wireless subnetwork; • identify location area; • perform system information broadcasting (system access information and service access related information); and • power saving/conservation support. ETSI TR 101 378 V1.1.1 (1998-12) 16 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.5 CCF (Call control and Connection control Function) | CCF establishes a call to the distant end of a network and associates radio and network nodes to the call. It includes: • establish, maintain, modify and release a call; • connection admission control for the fixed part of a connection; • call adaptation between the wireless subnetwork and the external network (if necessary); • establish a new link under inter-AP and release the old link (if inter-AP handover); • request for allocation/reservation of network resources and radio resources; • inter-AP handover initiation except for the cases due to changes in radio environment; • inter-AP handover execution (inter- and intra-CCF); • perform charging operation, if necessary; • control functions to establish, maintain, modify and release ATM connections in the ATMC Functional Element; • establish, maintain, modify and release ATM connections; • perform switching for network side ATM connections; and • provide information relevant to charging. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.6 RRC (Radio Resource Control function) | RRC handles the overall control of the radio resources and radio connections within a given area with typically many WACS Nodes. RRC should have an interface for AP transceiver and may have another interface for the mobility enabled switch. RRC includes: • sharing of radio resources between APTs; • radio channel management; • radio channel supervision including assessment of radio channel measurement results from RTR; • radio channel power control; • analysis of mobile radio environment; • hand-over initiation due to changes in radio environment (inter- and intra-AP); and • wireless CAC. ETSI TR 101 378 V1.1.1 (1998-12) 17 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.7 RTR (Radio Transmission and Reception function) | RTR handles the radio transmission and reception on the network side. It includes Data Link Control (DLC), Medium Access Control (MAC) and radio physical layer related (Radio PHY) functions. DLC functions (LLC and MAC) provide bearer services for ATM connections on U-plane and C-plane and control channels between the WACS Node and the wireless subnetwork. This includes: • error control functions to improve wireless specific transmission impairment (e.g. ARQ by error detection and re- transmission, and/or forward error correction coding and decoding); • multiplexing and de-multiplexing of logical channels; • mechanisms to share radio channels; • service requesting and service granting; • scheduling function to assign the "air time slot" for the ATM cells. The scheduling will be based on the ATM traffic contract and QoS parameters; • ciphering and deciphering; and • PDU handling function to manage the MAC data packets to be transmitted over the air interface. Radio PHY functions include: • RF generation, emission, and reception; • scramble and descramble; • baseband channel multiplexing and demultiplexing; • modulation and demodulation; • radio channel quality measurement and reporting; • RF power setting; • initial (random) access detection; • micro diversity relevant functions (e.g. antenna diversity); and • power control execution. DLC management functions include: • buffer traffic contracts; and • buffer link performance data. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.8 ATMC (ATM Connection function) | The ATMC function connects, maintains, modifies and releases ATM connections and provides ATM bearer services for C-plane and U-plane to connect the end user device to the external network (e.g. ATM switch). ATMC controls the ATM connection elements to provide ATM services (e.g. CBR, VBR-RT, VBR-NRT, ABR and UBR). It includes scheduling function to multiplex the ATM cells to be sent to the ATM switch. The scheduling will be based on the ATM traffic contract and QoS parameters. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.2.9 APCF (Access Point Control Function) | APCF includes functions to execute AP specific commands given by the EMAS and functions to relay information between the WACS terminal and the EMAS. These message exchanges take place via the APCP. ETSI TR 101 378 V1.1.1 (1998-12) 18 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.3 Interfaces | Table 2 below describes the interfaces given in figures 3 and 4. Table 2: Description of interfaces Interface Description Comments Inf.1: M-UNI This interface supports all the ATM core network related exchanges required for call set-up, clearing, location management. Inf.2: Association Control This interface supports the exchanges required for radio level association, radio level handover, paging and the radio link management for power conservation purposes. The activities on this interface must be closely co-ordinated with those on the Inf.1 Interface, the Inf.3 Interface and the Inf.7 Interface. Inf.3: Radio Resource Control This interface supports the exchanges required for radio resource monitoring, capacity monitoring, RF channel selection, etc. Consideration should be given to merging this with the Inf.2 Interface. Inf.4: Wireless DLC/PHY This interface supports the exchanges required for the operation of the radio link between the wireless Node and the wireless Access Point. Inf.5: (M-)UNI/NNI Standard interface between ATM switches, possibly enhanced to support mobility. Inf.6: UNI Does not apply to ETSI BRAN. This interface does not appear in the present document but it does appear in the ATM Forum baseline text. Inf.7: Access Point Control This interface supports the exchanges between the elements of the mobility support functions distributed between the Access Point and the End-user Mobility-supporting ATM Switch. The activities on this interface must be closely co-ordinated with those on the Inf.1 Interface, and the Inf.2 Interface. Inf.A: Smart Card Access This is an optional interface to access smart cards, containing, e.g. subscription information. Optional interface. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.4 Protocols | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.4.1 Wireless ATM layer model | The layer architecture presented below replaces the ATM PHY layer with two wireless layers that describe the wireless protocols: the Wireless Data Link Control Layer and the Wireless PHY layer. The DLC and PHY layers are each provided with Layer Management Elements. These model the functions and interfaces available for non-communications functions such as changing a radio channel. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 6.2.4.2 Wireless ATM Convergence Sublayer | The Wireless ATM Convergence Sublayer (WCS) is defined as a sublayer that generates no protocol but that provides the wireless DLC layer with the information it needs to perform its QoS management functions as required (e.g. the DLC Unitdata request could have parameters: VPI/VCI, cell loss priority, user data). Figure 5 shows the WCS in relation to some of the other system elements and protocols. The exact definition of the primitives between the DLC and the WCS is for definition by the BRAN Project. Given the desired behaviour and protocol of the DLC layer, the interface specification can be given and specified sufficiently clearly. The Layer Management Entity of the DLC layer is used to convey traffic contract information and performance requirements between the DLC layer and the higher, connection control functions. ETSI TR 101 378 V1.1.1 (1998-12) 19 Wireless Control Functions Wireless DLC Wireless PHY Wireless ATM Convergence sublayer ATM layer (S)AAL(X) Wireless DLC Wireless PHY (S)AAL(X) ATM PHY ATM PHY ATM layer AIR I/F LME LME Wireless Control Functions DLC-SAP Wireless ATM Convergence sublayer ATM layer WACS Node WACS Access Point EMAS Figure 5: Wireless ATM Protocol Layer architecture based on Wireless Convergence Sublayer (Distributed Control Model) This model is functionally equivalent to the respective ATMF models. BRAN will specify the interface between the ATM layer and the Wireless Convergence Sublayer. Some notes on the Layer Model: NOTE 1: The DLC layer contains two sublayers: a Medium Access Control sublayer (MAC) and a Logical Link Control sublayer (LLC). The MAC sublayer implements a service policy that takes into account such factors as channel quality, number of terminal devices and medium sharing with other wireless subnetworks. The LLC sublayer maintains the quality of service on a virtual circuit basis. Depending on the type of service provided and channel quality, capacity and utilization, the LLC layer may implement a variety of means including FEC, ARQ and flow pacing to optimize the service provided to the (DLC) user. NOTE 2: Generic Flow Control, once specified - may impact the functionality of the DLC layer and its service definition. NOTE 3: Usage Parameter Control is an optional capability of ATM systems that may have impact on the specification of the Wireless DLC layer and on the Access Point behaviour. ETSI TR 101 378 V1.1.1 (1998-12) 20 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7 Division of responsibility between ATMF and BRAN | This is the proposed division of responsibility between the ATM Forum and the BRAN Project. Responsibility assigned for a Functional Element or an Interface means that the relevant organization is responsible for producing the specification. However in some cases, it is indicated that specifications should be jointly created. In these cases, the responsibility for producing the specifications remains as designated, but both parties should contribute. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.1 Responsibility for interfaces | The responsible bodies for specifying Interfaces are listed in table 3 below. Table 3: Responsibility for Interface specifications Interface Responsible Comments Inf.1: M-UNI ATM Forum Inf.2: Association Control ETSI BRAN Project For joint specification. Inf.3: Radio Resource Control ETSI BRAN Project For joint specification. Inf.4: Wireless DLC/PHY ETSI BRAN Project Inf.5: (M-)UNI/NNI ATM Forum Inf.6: UNI ATM Forum This interface does not appear in the present document but it does appear in the ATM Forum baseline text. Inf.7: Access Point Control ATM Forum For joint specification. Inf.A: Smart Card access ATM Forum Optional interface. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.2 Interfaces subject to joint specification | |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.2.1 Inf.2: Association Control interface | This interface may contain, amongst others, the following elements: I.2.1 AP Beacon. Signals the presence, network name, current load and other details of AP. I.2.2 AP Associate - AP Disassociate. These allow a WACS Node to attach itself to an AP so that DLC connections can be established. The AP Disassociate can be send by the AP as well to unilaterally end an association, e.g. in terms of compromized security or failed authentication. I.2.3 Radio Handover Request/Complete. This is for further study. I.2.4 Freeze DLC link - Unfreeze DLC link. This supports power conservation modes and listening by the WACS Node on other (RF) channels. I.2.5 Establish Security Context - This allows the establishment of a security context between the WACS Node and the WACS AP in order to facilitate radio link encryption. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.2.2 Inf.3: Radio Resource Control interface | This interface may contain, amongst others, the following elements: I.3.1 Channel Quality Report Request - This allows an Access Point to query its nodes to report local RF channel conditions. I.3.2 Channel Quality Report - this allows a node to report RF channel conditions. This information may be combined with other interface elements, e.g. an Association Request. ETSI TR 101 378 V1.1.1 (1998-12) 21 |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.2.3 Inf.7: Access Point Control interface | The reason for a joint specification is the close relationship of this interface to interfaces Inf.1 and Inf.2. |
54dbcab7d1f46c040ce341b020d57461 | 101 378 | 7.3 Responsibility for Functional Elements | The responsible bodies for Functional Element specifications are listed in table 4. Table 4: Responsibility for Functional Element specification Functional Element Responsible Comments IMF ATM Forum The ID of the terminal user should be linked to the MMF and/or the ACF. CCF ATM Forum Should include high-level applications associated with call control, such as OA&M, billing, etc. For joint specification (depending on handover). MMF ATM Forum For joint specification (depending on handover). ACF ETSI BRAN Project For joint specification. RRC ETSI BRAN Project For joint specification. RTR ETSI BRAN Project ATMC ATM Forum APCF ATM Forum For joint specification. SCF ATM Forum SMF ATM Forum ETSI TR 101 378 V1.1.1 (1998-12) 22 History Document history V1.1.1 December 1998 Publication ISBN 2-7437-2556-7 Dépôt légal : Décembre 1998 |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 1 Scope | The purpose of the present document is to facilitate the interpretation of the technical concepts included in the DVB specifications related to DSNG transmission: - Framing structure, channel coding and modulation for Digital Satellite News Gathering (DSNG) and other contribution applications by satellite (EN 301 210 [1]); and - Co-ordination channels associated with Digital Satellite News Gathering (DSNG) (EN 301 222 [2]). The present document gives an overview of the technical and operational issues relevant to the system, including service quality and link availability evaluation for typical DSNG and fixed contribution links. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 2 References | The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. [1] EN 301 210: "Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for Digital Satellite News Gathering (DSNG) and other contribution applications by satellite". [2] EN 301 222: "Digital Video Broadcasting (DVB); Co-ordination channels associated with Digital Satellite News Gathering (DSNG)". [3] ISO/IEC 13818-1: "Information technology - Generic coding of moving pictures and associated audio information: Systems". [4] ISO/IEC 13818-2: "Information technology - Generic coding of moving pictures and associated audio information: Video". [5] EN 300 421: "Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for 11/12 GHz satellite services". [6] EN 50083-9: "Interfaces for CATV/SMATV Headends and similar Professional Equipment". [7] ETR 154: "Digital Video Broadcasting (DVB); Implementation guidelines for the use of MPEG-2 Systems, Video and Audio in satellite, cable and terrestrial broadcasting applications". [8] EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems". [9] TBR 30 (1997): "Satellite Earth Stations and Systems (SES); Satellite News Gathering (SNG) Transportable Earth Stations (TES) operating in the 11-12/13-14 GHz frequency bands". [10] ETS 300 327: "Satellite Earth Stations and Systems (SES); Satellite News Gathering (SNG) Transportable Earth Stations (TES) (13-14/11-12 GHz)". ETSI TR 101 221 V1.1.1 (1999-03) 7 [11] ETS 300 673 (1997): "Radio Equipment and Systems (RES); ElectroMagnetic Compatibility (EMC) standard for 4/6 GHz and 11/12/14 GHz Very Small Aperture Terminal (VSAT) equipment and 11/12/13/14 GHz Satellite News Gathering (SNG) Transportable Earth Station (TES) equipment". [12] ETS 300 813: "Digital Video Broadcasting (DVB); DVB interfaces to Plesiochronous Digital Hierarchy (PDH) networks". [13] ETR 162: "Digital Video Broadcasting (DVB); Allocation of Service Information (SI) codes for DVB systems". [14] ETR 211: "Digital Video Broadcasting (DVB); Guidelines on implementation and usage of Service Information (SI)". [15] ITU-R Recommendation BT.1121-1 (1995): "User requirements for the transmission through contribution and primary distribution network of digital HDTV signals". [16] ITU-R Recommendation BT.1205 (1995): "User requirements for the quality of baseband SDTV and HDTV signals when transmitted by digital satellite news gathering (SNG)". [17] ITU-R Recommendation SNG.722-1 (1992): "Uniform technical standards (analogue) for Satellite News Gathering (SNG)". [18] ITU-R Recommendation SNG.770-1 (1993): "Uniform operational procedures for Satellite News Gathering (SNG)". [19] ITU-R Recommendation SNG.771-1 (1993): "Auxiliary coordination satellite circuits for SNG terminals". [20] ITU-R Recommendation SNG.1007-1 (1995): "Uniform technical standards (digital) for Satellite News Gathering (SNG)". [21] ITU-R Recommendation SNG.1070 (1993): "An automatic transmitter identification system (ATIS) for analogue-modulation transmissions for Satellite News Gathering and outside broadcasts". [22] ITU-R Recommendation SNG.1152 (1995): "Use of digital transmission techniques for Satellite News Gathering (SNG) (sound)". [23] Void. [24] ITU-T Recommendation G.729: "Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction". [25] ITU-T Recommendation V.11: "Electrical characteristics for balanced double-current interchange circuits operating at data signalling rates up to 10 Mbit/s". [26] ANSI/EIA RS232E: "Interface between data terminal equipment and data-circuit terminating equipment employing serial binary data interchange". [27] ITU-T Recommendation G.702: "Digital hierarchy bit rates". [28] EBU technical Review (1998): "New DVB standard for DSNG and contribution satellite links", A. Morello, V. Mignone. [29] ETR 289: "Digital Video Broadcasting (DVB); Support for use of scrambling and Conditional Access (CA) within digital broadcasting systems". [30] TR 102 154: "Digital Video Broadcasting (DVB); Implementation guidelines for the use of MPEG-2 Systems, Video and Audio in satellite, cable and terrestrial contribution broadcasting applications". ETSI TR 101 221 V1.1.1 (1999-03) 8 |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 3 Symbols and abbreviations | |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 3.1 Symbols | For the purposes of the present document, the following symbols apply: a Roll-off factor ∆ Eb/N0 degradation at the target BER Γ Ratio of the spectrum density of the DSNG signal and of each co-ordination signal divided by the spreading factor L η Modulation/coding spectral efficiency (bits per transmitted symbol) Φ Antenna diameter ρ Is a parameter related to the ratio between C/N and C/I A Interference power suppression of each co-ordination channel by the baseband filter of the DSNG receiver C/N Carrier-to-noise power ratio C/I Carrier-to-interference power ratio dfree Convolutional code free distance dfree Convolutional code free distance Eb/N0 Ratio between the energy per useful bit and twice the two sided noise power spectral density f0 Centre frequency of a modulated signal fN Nyquist frequency fN Nyquist frequency g(x) RS code generator polynomial G1,G2 Convolutional code generators GLR,GLS ML-sequence generators GSS1, GSS2 Spreading sequences generators H(f) Baseband square root Raised Cosine filtering in the modulator I Interleaving depth [bytes] I, Q In-phase, Quadrature phase components of the modulated signal j Branch index of the interleaver K Convolutional code constraint length k/n Rate of the punctured convolutional code L Spreading sequence length (Spreading Factor) (bit) m Number of transmitted bits per constellation symbol M Convolutional interleaver branch depth for j = 1, M = N/I M Number of co-ordination carriers transmitted in CDMA configuration N Error protected frame length (bytes) ETSI TR 101 221 V1.1.1 (1999-03) 9 p(x) RS field generator polynomial R Useful bit-rate before multiplexer rm In-band ripple (dB) Rs Symbol rate corresponding to the bilateral Nyquist bandwidth of the modulated signal Rs Symbol rate corresponding to the bilateral Nyquist bandwidth of the modulated signal before spread-spectrum Rs,chip Chip symbol rate corresponding to the bilateral Nyquist bandwidth of the modulated signal after SS RTCM Rate of the trellis code Ru Useful bit rate after MPEG-2 (ISO/IEC 13818-1[3]) transport multiplexer, referred to the 188 byte format Ru Useful bit-rate after multiplexer, before channel encoder Ru(204) Bit rate after RS outer coder, referred to the 204 byte format T Number of bytes which can be corrected in RS error protected packet Ts Symbol period Ts Period of unspread symbol Ts, chip Period of the spread symbol, equal to 1/Rs, chip U Number of channels at the MUX input (U = 1, 2, 4) X,Y Di-bit stream after rate 1/2 convolutional coding NOTE 1: The sub-script "COOR" refers to the co-ordination signals. NOTE 2: The sub-script "DSNG" refers to the main DSNG signal. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 3.2 Abbreviations | For the purposes of the present document, the following abbreviations apply: 16QAM 16 points Quadrature Amplitude Modulation 1CBPS 1 Coded Bit Per Symbol 2CBPS 2 Coded Bits Per Symbol 422P@ML 422 Profile at Main level video format 8PSK Eight Phase Shift Keying ADPCM Adaptive Differential Pulse code modulation ATM Asynchronous Transfer Mode AWGN Additive White Gaussian Noise BB Baseband BER Bit Error Ratio BS Bandwidth of the frequency Slot allocated to a service BSS Broadcast Satellite Service BW Bandwidth (at -3 dB) of the transponder CA Conditional Access CCITT International Telegraph and Telephone Consultative Committee CDMA Code Division Multiple Access DCT Discrete Cosine Transform DEMUX De-multiplexer DPCM Differential Pulse Code Modulation DSNG Digital Satellite News Gathering DS-SS Direct-Sequence Spread-Spectrum DTH Direct To Home DVB Digital Video Broadcasting DVB-S Refers to the DVB Specification for Satellite services (EN 300 421 [5]) EBU European Broadcasting Union EIRP Equivalent Isotropic Radiated Power EPG Electronic Program Guide ETS European Telecommunication Standard ETSI European Telecommunications Standard Institute FDM Frequency Division Multiplex FDMA Frequency Division Multiple Access FEC Forward Error Correction ETSI TR 101 221 V1.1.1 (1999-03) 10 FIFO First-In, First-Out shift register FSS Fixed Satellite Service G/T Gain-to-noise temperature ratio GOP Group-of-Pictures HDTV High Definition Television HEX Hexadecimal notation IBO Input Back Off IF Intermediate Frequency IMUX Input Multiplexer - Filter IPFD Input power flux density IRD Integrated Receiver Decoder ITU International Telecommunications Union MCPC Multiple Channels Per Carrier MP@ML Main Profile at Main level video format MPEG Moving Pictures Experts Group MSB Most Significant Bit MUX Multiplex OBO Output Back Off OCT Octal notation OMUX Satellite transponder Output Multiplexer – Filter P Puncturing P/P Parallel-to-parallel P/S Parallel-to-serial PAL Phase Alternating line PCM Pulse-Code Modulation PDH Plesiochronous Digital Hierarchy ppm parts per million PRBS Pseudo Random Binary Sequence PSI Program Specific Information PSK Phase Shift Keying PSTN Public Switched Telephone Network QEF Quasi-Error-Free QPSK Quaternary Phase Shift Keying R Randomized sequence RF Radio Frequency RS Reed-Solomon SCPC Single Channel Per Carrier SI Service Information SMATV Satellite Master Antenna Television SNG Satellite News Gathering SS Spread Spectrum TBD To Be Defined TCM Trellis Coded Modulation TDM Time Division Multiplex TS Transport Stream TV Television TWTA Travelling Wave Tube Amplifier VBI Vertical Blocking Interval ETSI TR 101 221 V1.1.1 (1999-03) 11 |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4 Analysis of the capabilities of the DVB-DSNG system | |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.1 User's requirements | Using the same terminology as that of the ITU, the DVB has adopted the following definition of ITU-R Recommendation SNG.722-1 [17]: "Temporary and occasional transmissions with short notice of television or sound for broadcasting purposes, using highly portable or transportable up-link earth stations..."). The DSNG up-link terminals should be highly reliable and have reduced size and weight, while the receiving station may be appropriately dimensioned to ensure the required link availability. Therefore the transmission format should provide high ruggedness against noise and interference and best exploitation of satellite capacity. High intervention promptness and low set-up complexity is required. In particular, "the equipment should be capable of being set up and operated by a crew of no more than two people within a reasonably short time (for example, one hour)". Interoperability between different pieces of equipment is another key feature for DSNG, especially in an international programme exchange environment. In particular, the DVB has identified in the complexity of the DVB/MPEG SI/PSI tables a possible source of problems for DSNG, affecting equipment interoperability and fast link set up. For DSNG links, the typical bit-rate used by flyaway and small transportable terminals are about 8 Mbit/s, using MPEG-2 MP@ML. However for transportable stations, when higher quality and enhanced editing facilities are required, "use of MPEG-2 422P@ML should be supported. ... In this case, bit-rates should be higher than 8 Mbit/s and lower than 34 Mbit/s". Regarding Multiplexing, although DSNG transmissions usually transport a single TV programme and associated sound signals (SCPC, Single Channel Per Carrier), "advantage should be taken of the flexibility of the MPEG-DVB multiplex" to convey multiple programmes (MCPC, Multiple Channels Per Carrier). The processing delays of digital compression systems may be very high (even exceeding one second), especially with the sophisticated coding algorithms allowing high bit-rate compression ratios. Short video coding delays are important characteristics for those applications where the DSNG transmission is mixed together with a live programme, since long delays would prevent dialogues between journalists in the studio and in the field. Optionally, the DSNG equipment should be capable of providing two or more duplex co-ordination (communication) circuits by satellite as described in EN 301 222 [2], whenever possible in the same transponder as the main DSNG signal. These channels should be available prior to, during and after the DSNG transmission to connect the DSNG operator, the satellite operator and the broadcaster. This equipment may be also used for data transmission and fax. Examples of the use of the system with co-ordination channels are provided in clause 5 of the present document. Regarding the equipment cost, the DVB pointed out that "the total cost of the system and its operation should be considered, and not just the receiver cost. A non-negligible part of the overall cost of a SNG transmission lies in the requirements for satellite capacity. Modulation techniques, additional to QPSK, such as 8PSK and 16QAM, should be investigated to optimize the efficient use of satellite capacity". 4.2 Source coding transport multiplexing and service information The DVB has developed a series of User Guidelines for the implementation of MPEG-2 in contribution applications TR 102 154 [30]. Picture Coding The MPEG-2 Main Profile at Main Level (MP@ML) may be used as the baseline solution for picture coding in DSNG applications. It allows high flexibility for DSNG applications, being able to operate with variable bit-rates from 1,5 Mbit/s to 15 Mbit/s. ETSI TR 101 221 V1.1.1 (1999-03) 12 The MPEG-2 codecs are based on Hybrid DPCM/DCT algorithms with motion compensation, operating on I-frames (intra), P-frames (predicted) and B-frames (bi-directional prediction). It should be noted that MPEG-2 MP@ML is a 4:2:0 system and was designed for distribution rather than contribution. MPEG-2 MP@ML at bit-rates from 6 Mbit/s with IBBOP GOP structure allows, for current programme material, a subjective quality equivalent to PAL and 4:2:2 pictures, respectively. Lower bit-rates may be acceptable for specific applications, where power and bandwidth limitations are dominant over the picture quality requirements. In 1995, the MPEG-2 Committee defined a picture coding "profile" to fulfil the requirements of the production environment, which is named 422P@ML. It offers a number of additional features compared to the MP@ML format: the coding rate can be increased up to 50 Mbit/s, the chrome components maintain the 4:2:2 format as the uncompressed studio format. This allows higher picture quality, better chrome resolution, post-processing after co-decoding, short GOP to improve editability in compressed form and to shorten the coding delay. Subjective quality tests (non-expert viewers, 4H distance) have been carried out by the RAI Research Centre and other organizations (See annex A, article 9) on computer simulated 422P@ML sequences, with single and multiple generations (8 co-decoding processes) and colour matte post-processing. In conclusion, to fulfil the wide range of picture quality levels and bit-rates required by DSNG and other contribution applications, MPEG-2 MP@ML at bit-rates from 1,5 Mbit/s to 15 Mbit/s can cover the applications where no (or very limited) post-processing is performed in the studio before re-broadcasting, while MPEG-2 422P@ML at bit-rates from 15 Mbit/s to 30 Mbit/s can cover the high quality applications, where post-production and cascaded co-decoding are required. Audio Coding As regards the sound, all the DVB systems, in line with the trend toward international standardization, adopt the MPEG audio layer II coding method which allows a wide range of bit-rates (for example from 64 kbit/s to 256 kbit/s) satisfying the various service requirements. Bit-rates as low as 64 kbit/s may be applicable for some DSNG applications with mono channels. The optional use of linear (uncompressed) audio coding is also under evaluation by DVB, for contribution applications requiring maximum audio quality. Transport Multiplexing and Service Information (SI) The DVB-S system adopts a common framing structure, based on the MPEG-2 transport multiplex, with fixed length packets of 188 bytes, including 1 sync byte, 3 header bytes and 184 useful bytes. This structure allows easy interworking between broadcast channels and telecom networks using ATM protocols. The MPEG-2 multiplex is very flexible for merging in the Transport Stream (TS) a variety of video, sound and data services, as well as additional information (for example Service Information). Therefore it allows SCPC as well as MCPC services. The DVB-MPEG Service Information tables, defined for broadcasting applications, describe in detail the multiplex configuration and the programme content, and allow the user to easily access a wide programme offer through the Electronic Programme Guide (EPG). Annex D of the DSNG specification EN 301 210 [1] deals with a simplified Service Information mechanism, based on few fixed tables, avoiding the need to compile SI information in the field, in order to accelerate the link set up and to simplify interoperability problems. Up-link station identification is also provided, for emergency interference situations. ETSI TR 101 221 V1.1.1 (1999-03) 13 Scrambling for security applications For some DSNG applications, and for simplicity and maximum interoperability, the DSNG specification EN 301 210 [1] may be used with no security based scrambling. For many other DSNG applications scrambling will be necessary. The DVB has identified a variant of the Common Scrambling Algorithm (see ETR 289 [29]) suitable for DSNG and other contribution applications. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.3 Channel coding and modulation | Efficient and reliable transmission of digital television signals over satellite channels is focused on the design of the "channel adapter", which performs the adaptation of the multiplexed video/audio/data bit stream to the physical channel, by adopting powerful channel coding and modulation techniques. The specified system offers many transmission modes (inner coding and modulations), giving different trade-offs between power and spectrum efficiency. QPSK modulation has been adopted, and optionally 8PSK and 16QAM modulations, and the concatenation of convolutional and Reed Solomon codes. The QPSK mode is compliant with the DVB-S system defined in EN 300 421 [5], while for 8PSK and 16QAM, "pragmatic" trellis coding (see annex article 10) has been applied, optimizing the error protection of the same convolutional code. The QPSK and 8PSK modes, thanks to their quasi-constant envelope, are appropriate for operation with close to saturated satellite power amplifiers, in single carrier per transponder configuration. 16QAM (as well as QPSK and 8PSK) is appropriate for operation in quasi-linear satellite channels, in multi-carrier Frequency Division Multiplex (FDM) type applications, with high spectrum efficiency. For DSNG applications the usual method of accessing the transponders is Frequency Division Multiplexing (FDM), where part of the transponder bandwidth (frequency slot) is allocated to each signal. In order to reduce the effect of intermodulation noise introduced on adjacent carriers occupying the same transponder, the TWTA should be operated significantly below the saturation point. The linearity requirements are raised also by the fact that the aggregated FDM signal is no longer characterized by a constant envelope, even if each individual signal has quasi-constant envelope (for example QPSK or 8PSK). The higher is the spectrum efficiency of the modulation/coding scheme, the more stringent are the linearity requirements, because of the reduction of the system ruggedness against interference. In relation with 8PSK and 16QAM, the DVB-DSNG specification EN 301 210 [1] gives some warnings that are here reproduced: • they require higher transmitted EIRPs and/or receiving antenna diameters, because of their intrinsic sensitivity to noise and interference; • they are more sensitive to linear and non-linear distortions; in particular 16QAM cannot be used on transponders driven near saturation; • they are more sensitive to phase noise, especially at low symbol rates; therefore high quality frequency converters should be used; • the System modulation/coding schemes are not rotationally invariant, so that "cycle-slips" and "phase snaps" in the chain can produce service interruptions; therefore frequency conversions and demodulation carrier recovery systems should be designed to avoid cycle-slips and phase snaps. ETSI TR 101 221 V1.1.1 (1999-03) 14 MPEG-2 Source Coding and Multiplexing MUX Adaptation & Energy Dispersal Satellite Channel Adapter Outer Coder RS(204,188) Inter- leaver (I=12) Convolutional Inner Coder to the RF Satellite Channel Baseband Shaping Quadrature Modulator Mapping Constellation Bit Into type QPSK 8PSK (optional) 16QAM (optional) According to EN 300421 According to EN 300421 for QPSK α (see note) = 0,35 NOTE: α = 0,25 for 8PSK and 16QAM (additional and optional). Figure 1: Functional block diagram of the System Figure 1 gives a functional block diagram of the transmission system. The input stream, organized in 188 bytes packets following the MPEG-2 transport multiplexer ISO/IEC 13818-1 [3], is bit by bit randomized through a scrambling PRBS, in order to comply with the Radio Regulations interference requirements, which impose to have a regular spectrum shape of the transmitted signal, and to facilitate clock recovery in the receiver. Then the Reed-Solomon RS (204,188, t = 8) shortened code (derived from the original RS (255, 239, t = 8)), is applied to each randomized transport packet. Since, on the receiver side, the residual errors at the output of the Viterbi decoder are not statistically independent, but grouped in burst which may overload the RS code correction capability, the error distribution is randomized through a convolutional interleaver with depth I equal to 12 bytes applied to the error protected packets. The interleaved packets are then passed to the convolutional encoder, which is based on a rate 1/2 convolutional code with constraint length equal to 7 (64 trellis states), and allows the selection of the most appropriate level of error correction for a given service or data rate. Punctured convolutional coding is associated with QPSK modulation (according to the DVB-S system specification EN 300 421 [5] with the possibility to operate at five possible rates: 1/2, 2/3, 3/4, 5/6, 7/8; pragmatic Trellis Coded Modulations (TCM) is associated with 8PSK and 16QAM. The principle of the pragmatic trellis encoder is shown in figure 2. bytes from X Y I Q Puncturing Encoder Convolutional bit mapping constellation to P/S= parallel-to-serial NE P0 E U non-encoded branch P/P encoded branch P/S rate k/n convolutional code Symbol Sequencer over D symbols C 1 or 2 coded bits per symbol P/P= parallel-to-parallel interleaver P7 Figure 2: Inner trellis coder principle ETSI TR 101 221 V1.1.1 (1999-03) 15 The byte-parallel stream at the output of the convolutional interleaver is conveyed to a parallel-to-parallel converter, which splits the input bits into two branches, depending on the selected modulation/inner coding mode. The schemes of the parallel-to-parallel converters have been selected and designed in order to reduce, on average, the byte error-ratio at the input of the Reed-Solomon decoder (high concentration of bit-errors in bytes), and therefore the bit error ratio (BER) after RS correction is reduced. The 8PSK 5/6 and 8/9 schemes are characterized by 1 Coded Bit Per Symbol (1CBPS), while 8PSK 2/3 and 16QAM 3/4 and 7/8 schemes have 2 Coded Bits Per Symbol (2CBPS). The optimum bit mapping to constellation is different for 1CBPS and 2CBPS. The selection of the trellis coding schemes, from a number of different proposals, was based on accurate computer simulations carried-out by the RAI Research Centre. The selected schemes are the ones offering the best performance on a linear channel affected by Additive White Gaussian Noise (AWGN). In the cases of equal performance 1CBPS schemes have been preferred, since they require lower processing speed of the TCM Viterbi decoder compared to 2CBPS schemes, and therefore allows the implementation of higher speed modems (for high quality contribution applications or MCPC transmissions). Finally baseband shaping and quadrature modulation is applied to the signal. Square-root raised-cosine baseband shaping with a roll-off factor α = 0,35 is considered for all constellations, like in the DVB-S system EN 300 421 [5]. An additional roll-off factor α = 0,25 may be used for the 8PSK and 16QAM modulations, to increase the spectrum efficiency in the transponder bandwidth. This choice was based on extensive computer simulations, including the satellite TWTA effects. Error performance Sensitivity to transmission noise is expressed by the Eb/No ratio required to achieve a target residual BER. Eb is the energy per useful bit and No is the spectral density of the AWGN. The DVB-DSNG system has been designed to provide a quasi-error free quality target, i.e. less than one incorrect error-event per transmission hour at the input of the MPEG-2 demultiplexer. This target, achievable by interleaving and by RS error correction, corresponds approximately to a bit error ratio (BER) of 2 × 10-4 at the output of the TCM/Viterbi decoder. It should be noted that these evaluations take into account stationary noise only and ideal demodulation, while the effects of phase noise and carrier recovery instabilities might generate burst of uncorrectable errors separated by large time intervals. Since the DVB-DSNG coding schemes are not rotationally invariant (to optimize the BER performance), care should be taken in the design of frequency converters and carrier recovery systems, to avoid "cycle skipping" and "phase snaps", which may produce service interruptions. Table 1 gives the IF Loop system performance requirements for the different modes, in terms of the required Eb/No to provide BER = 2 × 10-4 (Quasi Error Free quality target). The figures of Eb/No are referred to the useful bit-rate Ru (188 byte format, before RS coding), and take into account the factor 10 Log 188/204 ˜0,36 dB due to the Reed-Solomon outer code and the modem implementation margins. For QPSK the figures are derived from EN 300 421 [5]. For 8PSK and 16QAM, modem implementation margins which increase with the spectrum efficiency are adopted, to cope with the larger sensitivity associated with these schemes. Table 1: IF-Loop performance of the DSNG System Modulation Inner code rate Spectral efficiency (bit/symbol) Modem implementation margin [dB] Required Eb/No for BER = 2 x 10-4 before RS QEF after RS [dB] 1/2 0,92 0,8 4,5 2/3 1,23 0,8 5,0 QPSK 3/4 1,38 0,8 5,5 5/6 1,53 0,8 6,0 7/8 1,61 0,8 6,4 8PSK 2/3 1,84 1,0 6,9 (optional) 5/6 2,30 1,4 8,9 8/9 2,46 1,5 9,4 16QAM 3/4 2,76 1,5 9,0 (optional) 7/8 3,22 2,1 10,7 NOTE 1: Quasi-Error-Free (QEF) means approximately less than one uncorrected error event per hour at the input of the MPEG-2 demultiplexer. NOTE 2: 8PSK 8/9 is suitable for satellite transponders driven near saturation, while 16QAM 3/4 offers better spectrum efficiency for quasi-linear transponders, in FDMA configuration. NOTE 3: The bit error ratio (BER) of 2 x 10-4 before RS decoding corresponds approximately to a byte error ratio between 7 x 10-4 and 2 x 10-3 depending on the coding scheme. ETSI TR 101 221 V1.1.1 (1999-03) 16 |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.4 Examples of use of the system | One of the main feature of the DVB-DSNG system is the flexibility, allowing to select the modulation, the symbol rate and the coding rate in order to optimize the satellite link performance (i.e. the spectral occupation on the satellite transponder and the power requirements) on a case-by-case basis. On the other hand, in order to achieve rapid interoperability and link set-up in emergency situations, the DSNG specification mandates that at least one "user-definable" set-up is available in DSNG equipment. This set-up includes video/audio coding parameters, modulation scheme and symbol rate. DSNG applications usually exploit the satellite bandwidth in FDM configuration, nevertheless the DSNG system is suitable also for single carrier per transponder transmissions. In single carrier per transponder configurations, the transmission symbol rate Rs can be matched to given transponder bandwidth BW (at -3 dB), to achieve the maximum transmission capacity compatible with the acceptable signal degradation due to transponder bandwidth limitations. To take into account possible thermal and ageing instabilities, reference can be made to the frequency response mask of the transponder. In multi-carrier FDM configuration, Rs can be matched to the frequency slot BS allocated to the service by the frequency plan, to optimize the transmission capacity while keeping the mutual interference between adjacent carriers at an acceptable level. Table 2 and figures 3a and 3b give examples of the maximum useful bit rate capacity Ru achievable by the System versus the allocated bandwidths BW or BS. Rs (symbol rate) corresponds to the -3dB bandwidth of the modulated signal. Rs(1 + α) corresponds to the theoretical total signal bandwidth after the modulator. In these examples the adopted BW/Rs or BS/Rs ratios are 1 + α = 1,35 where α is the roll-off factor of the modulation. This choice allows to obtain a negligible Eb/No degradation due to transponder bandwidth limitations, and also to adjacent channel interference on a linear channel. Higher bit-rates can be achieved with the narrow roll-off factor α = 0,25 (optional for 8PSK and 16QAM) and BW/Rs or BS/Rs equal to 1 + α = 1,25. BW/Rs or BS/Rs ratios different from 1 + α may be adopted for different service requirements, but the use of lower figures to improve the spectrum exploitation should be carefully studied on a case-by-case basis, to avoid severe performance degradations. ETSI TR 101 221 V1.1.1 (1999-03) 17 Table 2: Examples of maximum bit rates versus transponder bandwidth BW or frequency slot BS, for BW/Rs or BS/Rs = η = 1,35 BW Rs = Ru [Mbit/s] or BW/1,35 QPSK 8PSK 16QAM BS [MHz] [MBaud] rate 1/2 rate 2/3 rate 3/4 rate 5/6 rate 7/8 rate 2/3 rate 5/6 rate 8/9 rate 3/4 rate 7/8 72 53,333 49,1503 65,5338 73,7255 81,9172 86,0131 98,3007 122,876 131,068 147,451 172,026 54 40,000 36,8627 49,1503 55,2941 61,4379 64,5098 73,7255 92,1568 98,3007 110,588 129,020 46 34,074 31,4016 41,8688 47,1024 52,3360 54,9528 62,8032 78,5040 83,7376 94,2047 109,906 41 30,370 27,9884 37,3178 41,9826 46,6473 48,9797 55,9768 69,971 74,6357 83,9651 97,9593 36 26,666 24,5752 32,7669 36,8627 40,9586 43,0065 49,1503 61,4379 65,5338 73,725 86,0131 33 24,444 22,5272 30,0363 33,7908 37,5454 39,4227 45,0545 56,3181 60,0726 67,5817 78,8453 30 22,222 20,4793 27,3057 30,7190 34,1322 35,8388 40,9586 51,1983 54,6115 61,4379 71,6776 27 20,000 18,4314 24,5752 27,6471 30,7190 32,2549 36,8627 46,0784 49,1503 55,2941 64,5098 18 13,333 12,2876 16,3834 18,4314 20,4793 21,5033 24,5752 30,7190 32,7669 36,8627 43,0065 15 11,111 10,2397 13,6529 15,3595 17,0661 17,9194 24,5752 25,5991 27,3057 30,7190 35,8388 12 8,888 8,1917 10,9223 12,2876 13,6529 14,3355 16,3834 20,4793 21,8446 24,5752 28,6710 9 6,666 6,1438 8,1917 9,2157 10,2397 10,7516 12,2876 15,3595 16,3834 18,4314 21,5033 6 4,444 4,0959 5,4611 6,1438 6,8264 7,1678 8,1917 10,2396 10,9223 12,2876 14,3355 4,5 3,333 3,0719 4,0959 4,6078 5,1198 5,3758 6,1438 7,6797 8,1917 9,2157 10,7516 3 2,222 2,0480 2,7306 3,0719 3,4132 3,5839 4,096 5,1198 5,4611 6,1438 7,1678 1,5 1,111 1,0240 1,3653 1,5359 1,7066 1,7919 2,048 2,5599 2,7306 3,0719 3,5839 NOTE 1: Ru stands for the useful bit rate (188 byte format) after MPEG-2 MUX. Rs (symbol rate) corresponds to the -3dB bandwidth of the modulated signal. Rs(1 + α) corresponds to the theoretical total signal bandwidth after the modulator. NOTE 2: 8PSK 8/9 is suitable for satellite transponders driven near saturation, while 16QAM 3/4 offers better spectrum efficiency for quasi-linear transponders, in FDMA configuration. NOTE 3: BW/Rs or BS/Rs ratios different from 1 + α may be adopted for different service requirements. The adoption of BS/Rs figures significantly lower than 1 + α (for example BS/Rs = 1,21 associated with α = 0,35), to improve the spectrum exploitation, should be carefully studied on a case-by-case basis, since severe performance degradations may arise due to bandwidth limitations and/or adjacent channel interference, especially with 8PSK and 16QAM modulations and high coding rates (for example 5/6 or 7/8). ETSI TR 101 221 V1.1.1 (1999-03) 18 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 5,1 10,7 9,2 8,1 7,6 6,1 5,3 4,6 4,0 3,0 40,9 86,0 73,7 65,5 61,4 49,1 43,0 36,8 32,7 24,5 43,0 36,8 32,7 30,7 24,5 20,4 16,3 18,4 12,2 QPSK 8PSK 16QAM BW =4,5 BW =9 BW =18 BW =36 10,2 21,5 18,4 16,3 15,3 12,2 10,7 9,2 8,1 6,1 21,5 Ru Ru Ru Ru 61,4 36,8 BW =54 BW =72 129 110,5 98,3 92,1 73,7 49,1 55,3 64,5 Ru 122,8 73,6 81,8 172 147,4 131 98,2 86 65,4 49 Ru Figure 3a: Bit rate capacity versus available bandwidth (Ru in Mbit/s, and BW in MHz) 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 5,1 10,7 9,2 8,1 7,6 6,1 5,3 4,6 4,0 3,0 40,9 86,0 73,7 65,5 61,4 49,1 43,0 36,8 32,7 24,5 43,0 36,8 32,7 30,7 24,5 20,4 16,3 18,4 12,2 QPSK 8PSK 16QAM BW =4,5 BW =9 BW =18 BW =36 10,2 21,5 18,4 16,3 15,3 12,2 10,7 9,2 8,1 6,1 21,5 Ru Ru Ru Ru 61,4 36,8 BW =54 BW =72 129 110,5 98,3 92,1 73,7 49,1 55,3 64,5 Ru 122,8 73,6 81,8 172 147,4 131 98,2 86 65,4 49 Ru Figure 3b: Bit rate capacity versus available bandwidth (Ru in Mbit/s, and BW in MHz) Single carrier per transponder is also possible mainly for contribution applications. Table 3 considers possible examples of use of the DSNG System in the single carrier per transponder configuration for 36 MHz and 27 MHz transponder bandwidth. Different modulation and inner code rates are given with the relevant bit rates. According to typical practical applications, a BW/Rs ratio equal to 1,31 is considered for 36 MHz and 1,23 for 27 MHz transponder bandwidth, offering a slightly better spectrum efficiency than the examples of table 2 for the same modulation/coding schemes. The considered transponder bandwidth of 27 MHz and 36 MHz is wide enough to allow high quality 422P@ML Single Channel Per Carrier (SCPC) transmissions, as well as MP@ML and 422P@ML Multiple Channels Per Carrier (MCPC) transmissions. ETSI TR 101 221 V1.1.1 (1999-03) 19 Table 3: Examples of System configurations by satellite: Single carrier per transponder Satellite BW (At -3 dB) System mode Symbol Rate Rs [MBaud] Bit Rate Ru (after MUX) [Mbit/s] Eb/No (specification) [dB] 27 QPSK 5/6 22,000 33,791 6,0 36 QPSK 3/4 27,500 38,015 5,5 36 8PSK 2/3 27,500 50,686 6,9 NOTE 1: The Eb/No figures refer to the IF loop specification for Quasi-Error-Free (QEF) (see table 1). Overall linear, non-linear and interference performance degradations by satellite should be evaluated on a case-by-case basis; typical figures are of the order of 0,5 dB to 1,5 dB. NOTE 2: Quasi-constant envelope modulations, such as QPSK and 8PSK, are power efficient in single carrier per transponder configuration, since they can operate on transponders driven near saturation. Conversely, 16QAM is not power efficient since it can only operate on quasi-linear transponders (i.e. with large Output-Back-Off, OBO). The use of the narrow roll-off a = 0,25 with 8PSK can produce a larger non-linear degradation by satellite. Table 4 considers possible examples of use of the DSNG System in the multi-carrier FDM configuration and in SCPC (Single Channel Per Carrier) mode. Different modulation/coding modes are given with the relevant bit rates. Table 4: Examples of System configurations by satellite: multi-carrier FDM transmissions, SCPC mode Satellite BW [MHz] Slot BS [MHz] Number of Slots in BW Video Coding System mode Symbol Rate [MBaud] BS/RS [Hz/Baud] Bit Rate Ru [Mbit/s] Eb/No (specification) [dB] 36 9 4 MP@ML QPSK 3/4 6,1113 1,47 8,4480 5,5 36 18 2 422P@ML QPSK 7/8 13,3332 1,35 21,5030 6,4 36 12 3 422P@ML 8PSK 5/6 9,3332 1,28 21,5030 8,9 36 9 4 422P@ML 16QAM 7/8 6,6666 1,35 21,5030 10,7 72 18 4 422P@ML QPSK 7/8 13,3332 1,35 21,5030 6,4 NOTE 1: The Eb/No figures refer to the IF loop specification for Quasi-Error-Free (QEF) (see table 1). Overall linear, non-linear and interference degradations by satellite should be evaluated on a case-by-case basis; typical figures are of the order of 0,5 dB to 1,5 dB. NOTE 2: In the FDM configuration, the satellite transponder shall be quasi-linear (i.e. with large Output-Back-Off, OBO) to avoid excessive intermodulation interference between signals. Therefore 16QAM may be used. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.4.1 Link budget - generic hypothesis | In order to illustrate some potential examples of the use of the system, link budget analysis have been carried out assuming the following hypothesis: • It is considered a full 36 MHz transponder loaded with 4 equals digital carriers each one in a 9 MHz bandwidth slot. • Following the examples given in figures 3a and 3b, it is considered a symbol rate of 6,66 MBaud in 9 MHz (BW/Rs = 1,35). In table 5 it is summarized the useful bit rate after MPEG-2 multiplex for each modulation and channel coding scenario. Table 5 BW Rs QPSK 8PSK 16QAM (MHz) (MBaud) rate 1/2 rate 2/3 rate 3/4 rate 5/6 rate 7/8 rate 2/3 rate 5/6 rate 8/9 rate 3/4 rate 7/8 9 6,66 6,14 8,19 9,22 10,24 10,75 12,29 15,36 16,38 18,43 21,50 The following satellite TWTA overall operating points for each modulation and channel coding scheme, are considered (for multi-carrier per transponder operation) (see table 6). ETSI TR 101 221 V1.1.1 (1999-03) 20 Table 6 Modulation Scheme IBO total (dB) OBO total (dB) QPSK and 8PSK 8 3,7 16QAM 10 6 Satellite resources per carrier: the percentage of the power consumption per carrier is the same as the percentage of bandwidth consumption per carrier: • Power resources per carrier = 1/4 of the total power taking into account the overall operating point. • Bandwidth resources per carrier = 1/4 of the total transponder bandwidth (i.e. 9 MHz). • Quality and availability of the links: 2 x 10-4 before RS, 99,75 % and 99,9 % a.y. are considered (K and H ITU rain regions). Transmit DSNG transportable earth station characteristics: • Location: at beam edge and at beam centre. • Φ = 0,9 m, 1,2 m, 1,5 m and 1,8 m (65 % antenna efficiency, 0,3 dB coupling losses, 0,3 dB pointing losses) equipped with TWTA of 250 W. • Maximum operational EIRP (for 3 dB OBO) = 67 dBW for 1,8 m, 65 dBW for 1,5 m, 63 dBW for 1,2 m and 60 dBW for 0,9 m). Receive earth station characteristics for DSNG transmissions: • Location: at beam edge and at beam centre. • Φ = 2,4 m (G/T = 25 dB/k); 4,5 m (G/T = 30 dB/k) and 8,1 m (G/T = 35 dB/k). • 65 % antenna efficiency, 0,3 dB coupling losses, 0,5 dB pointing losses, 1,2 dB noise figure. Earth station characteristics for fixed contribution links: • Φ = 8,1 m, 4,5 m and 2,4 m. • Total (TWTA) OBO = 2 dB for QPSK and 8PSK, and 6 dB for 16QAM. • Maximum operational EIRP = ≤ 80 dBW. • G/T = 35 dB/k for 8,1 m, 30 dB/k for 4,5 m and 27 dB/k for 2,4 m. Satellite characteristics: • G/T = 5,5 dB/K at beam centre (-0,5 dB/K at beam edge). • EIRP (at saturation) = 50 dBW at beam centre (42 dBW at beam edge). IPFD = -85,5 dBW/m2 (Nominal setting) at beam centre (-79,5 dBW/m2 at beam edge). For the fixed contribution links using (16QAM) it is considered the operation of the transponder in 3 dB lower gain conditions. Simplified link budgets considering a total degradation of 2 dB due to all sources of interference (crosspolar and adjacent channels, intermodulation, non linearities, etc.) ETSI TR 101 221 V1.1.1 (1999-03) 21 Other assumptions are: • Reference satellite orbital location: 0ºE. • Uplink frequency: 14,25 GHz. • Downlink frequency: 11,75 GHz. • Sea level height for the transmit and receive earth stations: 100 m. • Atmospheric absorption: (0,3 dB for uplink and 0,2 dB for the downlink). • Worst case polarization (Linear horizontal). |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.4.2 DSNG Examples | Figures 4, 5, 6, 7, 8, 9 and 10, summarize the results in terms of clear sky margins obtained for the DSGN links using the above hypothesis. Figures 4, 6 and 9 include the results for the beam edge to beam edge links and figures 5, 7, 8 and 10 are for the beam centre to beam centre links. In these graphics it is indicated as reference, the estimated margin required for the 99,9 % and 99,75 % link availability corresponding to the ITU rain regions K and H. For example, if the required availability is 99,9 % and the transmission is made from zone H using 1,8 m as transportable earth station (maximum EIRP of 67 dBW), and 8,1 m as receiving earth station, both located at beam edge, it is possible to transmit a maximum useful data rate of about 12,29 Mbit/s in a 9 MHz slot using 8PSK 2/3 modulation scheme (see figure 4). In the same conditions of availability, zone and receiving earth station, if the transmit earth station is 1,2 m (maximum EIRP of 63 dBW), the maximum useful data rate is 9,22 Mbit/s in a 9 MHz slot using QPSK 3/4 modulation scheme. 0 1 2 3 4 5 6 7 8 9 10 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m Availability K H 99,9% 99,75% 99,9% 99,75% Figure 4: Clear sky margins for DSNG links (beam edge-to-beam edge), using transportable terminals of 1,8 m (useful EIRP 67 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) ETSI TR 101 221 V1.1.1 (1999-03) 22 0 2 4 6 8 10 12 14 16 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation Scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m K H Availability 99,9% 99,75% 99,9% 99,75% Figure 5: Clear sky margins for DSNG links (beam centre-to-beam centre), using transportable terminals of 1,8 m (useful EIRP 67 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) 0 2 4 6 8 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation scheme Clear sky margins (dB) 8,1 m 4,5 m 2,4 m Availability K H 99,9% 99,75% 99,9% 99,75% Figure 6: Clear sky margins for DSNG links (beam edge-to-beam edge), using transportable terminals of 1,5 m (useful EIRP 65 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) 0 2 4 6 8 10 12 14 16 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m K H 99,9% 99,75% 99,9% 99,75% Figure 7: Clear sky margins for DSNG links (beam centre-to-beam centre), using transportable terminals of 1,5 m (useful EIRP 65 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) ETSI TR 101 221 V1.1.1 (1999-03) 23 0 2 4 6 8 10 12 14 16 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation Scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m K H Availability 99,9% 99,75% 99,9% 99,75% Figure 8: Clear sky margins for DSNG links (beam centre-to-beam centre), using transportable terminals of 1,2 m (useful EIRP 63 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) 0 0,5 1 1,5 2 2,5 3 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation Scheme Clear sky margin (dB) 8,1 m Figure 9: Clear sky margins for DSNG links (beam edge-to-beam edge), using transportable terminals of 0,9 m (useful EIRP 60 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) 0 2 4 6 8 10 12 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 Modulation scheme Clear sky margin (dB) 2,4 m 4,5 m 8,1 m K H Availability 99,9% 99,75% 99,9% 99,75% Figure 10: Clear sky margins for DSNG links (beam centre-to-beam centre), using transportable terminals of 0,9 m (useful EIRP 60 dBW) for different receiving earth stations (8,1 m, 4,5 m, 2,4 m) The results included in the figures can be extrapolated for different symbol rates considering their corresponding satellite power and bandwidth resources scaled in a proportional way. ETSI TR 101 221 V1.1.1 (1999-03) 24 For example the clear sky margins included in figure 4 can be considered as the clear sky margins obtained by the links made using 1,5 m transportable DSNG (65 dBW as maximum EIRP) for a symbol rate of 3,33 MBaud in 4,5 MHz bandwidth slot. An other example, the clear sky margins included in figure 6 are also applicable to 1,8 m as transportable terminal (67 dBW as maximum EIRP), considering 13,3 MBaud in 18 MHz bandwidth. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.4.3 Fixed contribution links | Figures 11 and 12 summarize the results in terms of clear sky margins obtained for fixed contribution links using the corresponding hypothesis (see subclause 4.4.1). 0 2 4 6 8 10 12 14 16 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 16QAM 3/4 16QAM 7/8 Modulation scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m K H Availability 99,9% 99,75% 99,9% 99,75% Figure 11: Clear sky margins for fixed contribution links considering different receiving earth stations (8,1 m, 4,5 m and 2,4 m) located at beam centre (Transponder operated in "Nominal Gain") 0 2 4 6 8 10 12 14 16 18 QPSK 1/2 QPSK 2/3 QPSK 3/4 QPSK 5/6 QPSK 7/8 8PSK 2/3 8PSK 5/6 8PSK 8/9 16QAM 3/4 16QAM 7/8 Modulation scheme Clear sky margin (dB) 8,1 m 4,5 m 2,4 m Figure 12: Clear sky margins for fixed contribution links considering different receiving earth stations (8,1 m, 4,5 m and 2,4 m) located at beam centre (Transponder operated in "Nominal Gain-3 dB") |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 4.4.4 Interfacing with terrestrial telecommunications networks | There is the possibility within the specified system to allow interworking between satellite and terrestrial digital networks. The connection of the system with the terrestrial telecommunications networks is illustrated in figure 13. Table 7 shows the symbol rates and their corresponding bandwidth that would be suitable for connection to a PDH terrestrial networks at 34 368 Kbit/s, where the transmission capacity is 29 140 Kbit/s after Reed Solomon coding. ETSI TR 101 221 V1.1.1 (1999-03) 25 Table 7: Examples of Symbol rates using QPSK, 8PSK and 16QAM for 29,140 Mbit/s bit rate after RS QPSK 8PSK (Optional) 16QAM (Optional) 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 Rs (MBaud) 29,14 21,86 19,43 17,48 16,65 10,93 8,74 8,20 4,86 4,16 BW = Rs x 1,35 (Rs x 1,25 Optional) (MHz) 39,34 29,50 26,23 23,60 22,48 14,75 (13,66) 11,80 (10,93) 11,06 (10,25) 6,56 (6,08) 5,62 (5,20) In order to provide an example of the system for connection to a PDH terrestrial networks, it is considered a 72 MHz transponder divided into four 18 MHz slots. The following configuration is suitable for this application: • Useful bit rate (Ru) + Reed Solomon bit rate (RS) = 29,140 Mbit/s. • Modulation scheme: 8PSK. • Convolutional coding 2/3. • Symbol Rate (Rs) = 10,928 MBaud. • Allocated bandwidth (Rs x 1,35) = 14,8 MHz (compatible with 18 MHz bandwidth slot). • Fixed contribution link between 8,1 m earth stations, located at beam center for 99,9 % availability (zone K). Video Coder Audio Coder Data Coder 1 2 n Service components Services MPEG-2 Source Coding and Multiplexing Transport MUX Ru' = 29,140 Mb/s Outer Code Inter- leaver I = 8 Inner Coder QPSK 8PSK/16QAM Modulator to the RF Satellite Channel Satellite Channel Adaptation 34,368 Mbit/s (ITU-T G.702) PDH Terrestrial Network (Hier.Level III) PDH Terrestrial Network Adaptation RS(204,188) Convolutional Type Network Adapter Network Adapter Figure 13: Example of Connection of the System with Terrestrial PDH Network following ETS 300 813 [12] ETSI TR 101 221 V1.1.1 (1999-03) 26 |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 5 Analysis of the co-ordination channels capabilities | |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 5.1 Summary of the co-ordination channel system | Following the ITU-R Recommendation SNG.771-1 [19] "SNG earth stations should be equipped to provide two-way satellite communication circuits which shall be available prior to, during and after, the transmission of the vision and associated sound or sound programme signal. These circuits will provide communications between the SNG operator, the satellite operator and the broadcaster; that two or more duplex circuits should be provided, whenever possible within the same transponder as the programme vision and associated sound or sound programme signal". The same Recommendation considers "that throughout the world, where news events take place, uniform technical and operational standards for communication should be established to ensure prompt activation of the SNG service". The availability of co-ordination (communication) circuits by satellite may be particularly useful in areas where access to the public switched or cellular telephone networks is difficult or impossible. For these purposes, the same antennas of the DSNG stations may often be used, and the same frequency resources (or at least the same satellite transponder) as the main DSNG signal may be exploited. Other frequency resources may also be chosen according to the operational conditions and requirements. To achieve a two-way (i.e. full-duplex) communication channel, two independent carriers have to be transmitted, one from the DSNG terminal, the other from a fixed station. Depending on the service requirements, various scenarios are possible, some of which require reduced communication capacity, others are more demanding (in terms of the number of required connections and up-link facilities). Figure 14 extracted from EN 301 222 [2], shows two examples of implementation of the co-ordination channels between the DSNG terminal, the broadcaster, the DSNG operator (when required) and the satellite operator: • Scenario A (two up-links for co-ordination carriers): the DSNG terminal and a central station (for example the broadcaster's fixed station) up-link a single co-ordination carrier each, containing U multiplexed circuits. In this scenario the terrestrial infrastructure (for example PSTN) is used to forward the co-ordination circuits from the central station to the DSNG operator and the satellite operator and the co-ordination equipment at the DSNG terminal has to transmit and receive a single co-ordination carrier. • Scenario B (four up-links for co-ordination carriers): the DSNG terminal up-links a single co-ordination carrier, containing three multiplexed channels (U = 3), while the broadcaster, the DSNG operator and the satellite operator up-link a total of three co-ordination carriers, each with a single circuit. In this scenario, the co-ordination equipment at the DSNG terminal has to transmit a single co-ordination carrier, and to receive three carriers at the same time. ETSI TR 101 221 V1.1.1 (1999-03) 27 BROADCASTER SATELLITE OPERATOR SATELLITE DSNG TERMINAL SCENARIO A with two up-links PSTN DSNG OPERATOR BROADCASTER SATELLITE DSNG TERMINAL DSNG OPERATOR SATELLITE OPERATOR CO-ORDINATION SIGNALS U=1,2, 4 MULTIPLEXED CHANNELS SCENARIO B with four up-links DSNG SIGNAL DSNG SIGNAL CO-ORDINATION SIGNALS Figure 14: Example environments for DSNG and co-ordination channels transmissions by satellite Co-ordination channels services: voice, fax and data The co-ordination channels specification describes the source coding (for voice and data), multiplexing, channel coding and modulation system for the optional co-ordination (communication) channels by satellite associated with DSNG services. The integration of this System in a DSNG station shall be optional, since other communication systems (for example PSTN, cellular phones connected to terrestrial or satellite networks) may be used, according to the prevailing operational needs. Maximum compatibility with existing ETSI and ITU standards is maintained. In particular voice coding is performed according ITU-T Recommendation G.729 [24] (see Informative Note), offering high voice quality at 8 kbit/s (i.e. better than ADPCM at 32 kbit/s). Data transmission is performed in synchronous RS-422 format, (ITU-T Recommendation V.11 [25]) at bit-rates of 8 kbit/s, 16 kbit/s, or 32 kbit/s. Optionally it may be performed in asynchronous RS-232 format (ANSI/EIA RS232E [26]) at a maximum bit-rate of 9,6 kbit/s, 19,2 kbit/s or 38,4 kbit/s. ETSI TR 101 221 V1.1.1 (1999-03) 28 The co-ordination channels system provides up to four full-duplex co-ordination (voice) channels at 8 kbit/s by satellite, or data capacity for other applications. A co-ordination channel may also convey facsimiles (fax). A fixed time-division multiplex allows the transmission of one, two or four 8 kbit/s channels producing an output bit-stream at 8,16 kbit/s, 2 × 8,16 kbit/s, 4 × 8,16 kbit/s, respectively. The multiplex provides a signalling byte, which indicates the multiplex configuration to the receiver. Modulation and channel coding In order to achieve high ruggedness against noise and interference Direct-Sequence Spread-Spectrum (DS-SS) processing is applied before Quaternary Phase Shift Keying (QPSK) modulation, generating a modulated signal whose bandwidth occupation is expanded and whose power spectral density level is reduced accordingly. DS-SS technique permits the superposition of a number of co-ordination signals in the frequency domain (Code Division Multiple Access, CDMA), using the same centre frequency. For example the scenarios in figure 14 may be efficiently implemented by using this technique. For system simplicity, the spreading processes are asynchronous at each terminal, therefore the number of channels which may be superimposed is limited by mutual interference. Compared to conventional modulations, DS-SS techniques offer significant performance improvements in the presence of interference (for example from and to co-channel narrow-band signals) and also produce less intermodulation noise density over a non linear transponder. DS-SS signals also require less frequency precision in the transmission/reception equipment. In figure 15 the basic principle of Direct-Sequence Spread-Spectrum coding is illustrated. TS,chip t L . TS,chip = TS TS,chip t X X Binary Input (NRZ) from convolutional Spreading Sequences I-Branch Q-Branch To Baseband Filter coder Figure 15: Basic principle of Direct-Sequence Spread-Spectrum coding The bit stream randomization for energy dispersal and inner convolutional coding (rate 1/2 only) for error correction is also considered in order to achieve high ruggedness against noise and interference. Reed-Solomon coding and convolutional interleaving are not used in the System, as the target BER (10-3) after FEC decoding is adequate for voice communication using ITU-T Recommendation G.729 [24], and additionally since they would generally introduce a large end-to-end delay which may cause problems on voice communications in DSNG applications. In summary, the following processes are applied to the data stream (see figure 16): • Voice coding at 8 kbit/s according to ITU-T Recommendation G.729 [24]. • Data coding (Optional). • Multiplexing and framing. • Multiplex adaptation and signal randomization for energy dispersal. • Rate 1/2 convolutional inner coding with constraint length 7, according to EN 300 421 [5]. ETSI TR 101 221 V1.1.1 (1999-03) 29 • Direct-Sequence Spread-Spectrum (DS-SS) processing (with five possible spreading factors: L = 31, 63, 127, 255 and 511). • Bit mapping into QPSK constellation, according to EN 300 421 [5]. • Square-root raised cosine baseband shaping (roll-off factor α = 0,35), according to EN 300 421 [5]. • Quadrature modulation, according to EN 300 421 [5]. Voice/Data Coder 1 2 ... MUX and framing QPSK Modulator Baseband Shaping Interface A Interface B Interface C Power and Frequency Adaptation DS-SS Processing Spreading sequences Rate 1/2 Code DSNG signal (DSNG up-link only) MUX Adaptation and Energy Dispersal Inner Code Modulator MUX Source Coding U R R u U = 1, 2, 4 u 204/200 Voice/Data Coder Voice/Data Coder Voice/Data Coder DSNG signal Combiner R = 8 kbit/s (or 16 kbit/s or 32 kbit/s, for logical channel 1 only and for U = 1) R = U R X X Convolutional Figure 16: Functional block diagram of the System Flexible user definable set-up configuration The co-ordination carriers may be transmitted at a power level significantly lower than that of the DSNG carrier, since their bit-rate is typically some hundred times lower than the DSNG bit-rate, therefore they do not significantly modify the transponder operating point. Flexible, user-definable frequency assignments may be used for the co-ordination channels, allowing the selection on a case-by-case basis of the best Frequency Division Multiplex (FDM) configuration in the satellite transponder. For example, the System is capable of operating, if required, within the same frequency slot as the main DSNG signal, while keeping the level of mutual interference between the main DSNG signal and the co-ordination carriers at an acceptable level. Annex D of EN 301 222 [2] includes further details and is here reproduced in subclause 5.2. To achieve this, the co-ordination channels may be superimposed onto the main DSNG signal (for example the same centre frequency), at the cost of some performance degradation due to mutual interference, which may be more or less critical depending on the modulation/coding scheme of the DSNG system and on the mutual signal levels. As an alternative, the co-ordination channels using a low spreading factor (for example 0,5 MHz or 1 MHz bandwidth occupation) may be allocated within the "roll-off" region of the DSNG signal, in order to reduce the mutual interference between co-ordination and DSNG signals. In other cases, a clear frequency slot may be allocated to co-ordination channels, on the same transponder as the DSNG signal, or even on another transponder/satellite, according to the service requirements. The transmission parameters of the co-ordination channels, such as the frequency, the power level, the symbol-rate and the spreading sequences shall be selectable by the operator in order to allow flexible access to the satellite resources. They are to be manually set-up in the co-ordination terminals. At least one user definable frequency and power set-up configuration shall be provided by the co-ordination channel equipment, in order to facilitate rapid link set-up in emergency situations (see annex B of EN 301 222 [2]). This frequency and power set-up shall be easily selectable in the equipment. Normal practice for setting up the co-ordination carriers will be defined from operational experience of the system. Error Performance The modem, connected in IF loop, shall meet the BER versus Eb/No performance requirements given in table 8. ETSI TR 101 221 V1.1.1 (1999-03) 30 Table 8: IF-Loop performance for the co-ordination channels system Modulation Convolutional code rate Spectral efficiency before spreading (bit/symbol) Required Eb/No (dB) (Note) for BER = 10-3 QPSK 1/2 0,9804 3,6 NOTE: The figure of Eb/No is referred to the bit-rate after Viterbi decoding (i.e. Ru) and includes a modem implementation margin of 0,8 dB. BER levels up to 10-3 may be tolerated by voice services. Lower BER levels may be required for some data services, in this case additional error protection may be applied externally to the modem. 5.2 Examples of use of the DVB-DSNG System with their associated co-ordination channels This subclause has been extracted from annex D of document EN 301 222 [2]. A DSNG transmission may consist of the main DSNG signal, compliant with the DSNG specification EN 301 210 [1] plus various co-ordination signals (full-duplex links). Different frequency allocations may be adopted for the co- ordination channels, depending on the available bandwidth, spectrum occupation of the main DSNG transmission, number of co-ordination channels, and other service requirements. The co-ordination signals may be placed in a clear frequency slot of the transponder, and in this case no co-channel interference to and from the DSNG signal is present, but only the mutual interference among the co-ordination channels (in addition to the typical interference in the transponder). As an alternative, the co-ordination carriers can share the same frequency slot (bandwidth BS) as the DSNG signal, accepting some performance degradation for both the co-ordination signals and the DSNG signal. In this latter case (see figure 17), the co-ordination signals may be superimposed onto the DSNG signal or may be placed in its roll-off region, in order to reduce the mutual interference. The superimposed configuration may have the operational advantage to use the same centre frequency for the DSNG carrier (f0,DSNG) as for the co-ordination carriers (f0,COOR), while the roll-off configuration may have the advantage to reduce the mutual interference between the DSNG and co- ordination signals, thus allowing better RF performance. The co-ordination channels sharing the same DSNG frequency slot may use different bit-rates, spreading sequences and spectral density levels, according to the operational requirements. Nevertheless the number of co-ordination channels should be maintained as low as the operational requirements permit, in order to limit the mutual DSNG/co-ordination channels interference. Furthermore to guarantee an adequate mutual signal to interference ratio due to the other co-ordination channels, the different co-ordination channels should be kept at the same power spectral density level. f0,DSNG f COOR DSNG BS/2 f0,DSNG f0,COOR f COOR DSNG ΓdB+10 Log(L) ΓdB+10 Log(L) = f 0,COOR BS/2 R S,chip/2 R S,DSNG/2 R S,DSNG/2 R S,chip/2 NOTE: The Eb/N0 ratios displayed by demodulators are usually evaluated from BER measurements. Therefore they refer to an effective Eb/(N0 + I0) ratio, where I0 is the equivalent spectral density of the interfering signals (for example, the co-ordination channels) and N0 the spectral density of the thermal noise. As a consequence, in the presence of co-ordination channel interference, care should be taken by the operators while evaluating the real thermal noise margin and allowed rain attenuation of the link. Figure 17: Possible frequency allocations of the co-ordination signals in the DSNG frequency slot: (left) superimposed to the DSNG signal; (right) in the roll-off region of the DSNG signal ETSI TR 101 221 V1.1.1 (1999-03) 31 To estimate, to a first approximation, the impact of the co-ordination channels on the DSNG signal performance, the following hypotheses have been adopted: (a) the transponder is operated in a quasi linear mode; (b) the interference of the DSNG signal on the co-ordination channels (and vice-versa) and the co-ordination channel interference due to the other co-ordination channels is equivalent to Gaussian noise of the same power. The latter approximation may be slightly pessimistic compared to digitally modulated signals, and applies under the assumption of non-synchronized and therefore non-orthogonal spreading sequences. In this case the co-ordination channel signal to interference ratio due to the other co-ordination channels can be approximated by the power ratio L/(M-1), where L indicates the spreading factor and M the number of co-ordination carriers in CDMA. (When the co-ordination channels are synchronized, the signal to interference power ratio can be approximated by the ratio L2/(M-1)). The Eb/N0 performance degradation of the main DSNG signal ∆DSNG, due to the co-ordination channel interference, can be computed with the formulae: ∆DSNG = ρDSNG / (ρDSNG - 1) ρDSNG = RDSNG A2 / (M RCOOR (Eb/N0)COOR (Eb/N0)DSNG ρCOOR η2 DSNG) ρCOOR -1 = 1 - ∆COOR -1 – ((L/(M-1)) / (Eb/N0)COOR)-1 where M indicates the number of communication carriers (M = 2 corresponds to a single full-duplex connection), RDSNG and RCOOR the useful bit-rate for the main and co-ordination signals respectively, ηDSNG the modulation/coding spectral efficiency (bit/symbol) of the DSNG signal, ∆COOR the Eb/N0 performance degradation of the co-ordination signal, ρ is a parameter related to the ratio between C/N and C/I. A is the mutual interference power suppression of the DSNG and each co-ordination channel due to the baseband filtering in transmitters and receivers, assuming matched filters (A = 1 for co-ordination signals superimposed onto the DSNG signal). The factor A may be computed by using the formula: [ ] df f f f H f H R A COOR DSNG COOR DSNG COOR S ) ( ) ( 1 ,0 ,0 2 2 , − − = ∫ ∞ ∞ − where HDSNG is the transfer function of the DSNG receive/transmit baseband filters and HCOOR is the transfer function of the co-ordination receive/transmit baseband filters (ideally corresponding to square root raised cosines). Given the previously defined Eb/N0 performance degradation of the co-ordination signal ∆COOR, and therefore the factor ρCOOR, the ratio Γ between the spectral densities of the DSNG signal and of each co-ordination signal divided by the spreading factor L can be estimated as: Γ = A/((Eb/N0)COOR ρCOOR ηCOOR) where: ηCOOR = 0,9804 Table 9 reports a list of the symbols and their meanings. Table 9: List of the symbols A Interference suppression in the baseband filters ∆ Eb/N0 degradation at the target BER Eb/N0 Ratio between the energy per useful bit and twice the two side thermal noise power spectral density Γ Ratio of the spectrum density of the DSNG signal and of each co-ordination signal divided by the spreading factor L η Modulation/coding spectral efficiency (bits per transmitted symbol) L Spreading sequence length (Spreading Factor) (bit) M Number of co-ordination carriers transmitted in CDMA configuration R Useful bit-rate before multiplexer ρ Parameter related to the ratio between C/N and C/I NOTE 1: The sub-script COOR refers to the co-ordination signals. NOTE 2: The sub-script DSNG refers to the main DSNG signal. ETSI TR 101 221 V1.1.1 (1999-03) 32 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 L = 63 L = 127 L = 511 ∆ COOR = 4,33 dB Γ [dB] L M QPSK 8PSK 16QAM M = 6 M = 4 M = 2 ∆ DSNG [dB] given ∆ COOR = 4,33 dB 63 -5,9 -6,4 -7,1 127 -5,7 -6,0 -6,3 511 -5,6 -5,7 -5,8 2 4 6 Figure 18 Assuming superimposed frequency sharing as in figures 17 (left), 18 and 19 give examples of the main DSNG signal Eb/N0 performance degradation ∆DSNG. The main DSNG signal has a symbol rate of 6,666 MBaud, thus occupying a frequency slot of 9 MHz. A fixed degradation of the co-ordination channel performance of 4,33 dB (see note 3) has been imposed, due to interference from the DSNG signal and from other co-ordination channels. The required (Eb/N0)COOR is 3,6 dB at a target BER of 10-3 (see table 7). The DSNG schemes considered are QPSK, 8PSK, 16QAM, assuming the IF-loop performance given in table 1. In figures 18 and 19, the adopted Γ factor is also given, representing the ratio between the DSNG and co-ordination channel spectral density divided by the spreading factor L. Other Γ factors may be chosen, according to the performance requirements. Lower Γ figures improve the performance of the co-ordination channels, while larger Γ figures improve the DSNG performance. NOTE 3: This corresponds to a fixed BER of about 10-5 after Viterbi decoder in the absence of thermal noise. EXAMPLE 1: (Figure 18) 8 kbit/s per co-ordination carrier, different number of unidirectional channels M. Figure 18: 8 kbit/s co-ordination channels superimposed to DSNG. Example performance degradation of DSNG (RS = 6,666 MBaud) interfered with by M co-ordination signals, with L = 63, L = 127 and L = 511. The degradation of the co-ordination channels has been assumed to be ∆COOR = 4,33 dB. Table 9 reports the meaning of the symbols. Assuming a DSNG signal using QPSK FEC rate 2/3, from figure 18 (8 kbit/s channels) an estimated DSNG degradation of 0,7 dB is obtained for M = 6 and L = 63. For higher DSNG spectrum efficiency modes (for example 8PSK and 16QAM), the interference degradation progressively increases and may become unpractical. EXAMPLE 2: (Figure 19) 32 kbit/s per co-ordination carrier, different number of unidirectional channels M. For 32 kbit/s co-ordination channels and M = 2, a degradation on the DSNG signal (QPSK 1/2, 2/3 and 3/4) lower than 1 dB is achieved. Figure 19: 32 kbit/s co-ordination channels superimposed to DSNG. Example performance degradation of DSNG (RS = 6,666 MBaud) interfered with by M co-ordination signals, with L = 63 and L = 127. The degradation of the co-ordination channels has been assumed to be ∆COOR = 4,33 dB. Table 9 reports the meaning of the symbols. As indicated in figure 17 (right), to reduce mutual interference, the co-ordinations channels may be placed in the roll-off region of the DSNG signal. In order to minimize the mutual interference, the co-ordination signals may use a low spreading factor (i.e. L = 31, L = 63 or L = 127, according to the co-ordination channel bit-rate) and may be placed, for example, in the upper part of the frequency slot allocated to DSNG. In this configuration the centre frequency f0, COOR of the co-ordination signals may be computed by the following formula: ETSI TR 101 221 V1.1.1 (1999-03) 33 L = 63 L = 127 ∆ COOR = 4,33 dB Γ [dB] 2 4 63 -5,9 -6,4 127 -5,7 -6,0 L M 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 QPSK 8PSK 16QAM ∆ DSNG [dB] given ∆ COOR = 4,33 dB M = 4 M = 2 Figure 19 (2) f0,COOR = f0,DSNG + BS / 2 – ( 1,35/2) RS,COOR where f0,DSNG is the centre frequency of the DSNG signal and BS the bandwidth of the frequency slot, RS,COOR = RS,chip is the co-ordination channel symbol rate. In the following, the achievable performance is given for two example configurations, based on the frequency allocations of formula (2) and choosing Γ equal –3 dB as a reasonable practical upper limit for the power density level of the co-ordination channels. EXAMPLE 3: (Figure 20) 8 kbit/s co-ordination channels. M unidirectional co-ordination channels are considered, each at 8 kbit/s, with a spreading factor of 63 and 127. The main DSNG signal has a symbol rate of 6,666 MBaud, thus occupying a frequency slot of 9 MHz. The roll-off region (from the –3 dB point to the slot margin) is 1,167 MHz wide, while the co-ordination signal bandwidth is about 0,5 MHz for spreading factor 63 and 1 MHz for spreading factor 127. Due to the roll-off filter effect, the mutual interference suppression A is about 5,5 dB for L = 127 and 9,7 dB for L = 63. The resulting performance degradations of the DSNG signal are reported in figure 19, assuming a Γ factor (ratio between the DSNG and each co-ordination channel spectral density divided by the spreading factor L) of -3 dB (the – sign indicates that the co-ordination channels before SS have a spectral density higher than that of the DSNG signal). In the example, even in the case of M = 6 the DSNG degradation may be maintained below 0,5 dB for DSNG modulations up to 16QAM FEC rate 3/4. QPSK 8PSK 16QAM ∆ COOR [dB] 2 4 6 63 0,7 1,1 1,6 127 1,8 2,1 2,3 L M M=6 M=4 M=2 L = 63 L = 127 ∆ DSNG [dB] given Γ = -3 dB 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 Figure 20 ETSI TR 101 221 V1.1.1 (1999-03) 34 Figure 20: 8 kbit/s co-ordination channels in the "Roll-off" region of DSNG – Example performance degradation of DSNG (RS = 6,666 MBaud) interfered with by M co-ordination signals, with L = 63 and L = 127. The ratio between the DSNG and each co-ordination channel spectral density divided by the spreading factor L has been assumed to be Γ = -3 dB. Table 9 reports the meaning of the symbols. EXAMPLE 4: (Figure 21) 32 kbit/s co-ordination channels. M unidirectional co-ordination channels are considered, each at 32 kbit/s, with a spreading factor of 31. The main DSNG signal has a symbol rate of 6,666 MBaud, thus occupying a frequency slot of 9 MHz. The roll-off region (from the –3 dB point to the slot margin) is 1,167 MHz wide, while the co-ordination signal bandwidth is about 1 MHz. Due to the roll-off filter effect, the mutual interference suppression A is about 5,5 dB. The resulting performance degradations of the DSNG signal are reported in figure 21, assuming a Γ factor of - 3 dB (the – sign indicates that the co-ordination channels before SS have a spectral density higher than DSNG). In the example, in the case of M = 4 the DSNG degradation may be maintained below 0,5 dB for DSNG modulations up to 8PSK FEC rate 2/3. 0,0 0,5 1,0 1,5 2,0 2,5 1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8 QPSK 8PSK 16QAM M = 2 ∆ COOR = 2,2 dB M = 4 ∆ COOR = 3,4 dB ∆ DSNG [dB] given Γ = -3 dB Figure 21 Figure 21: 32 kbit/s co-ordination channels in the "Roll-off" region of DSNG – Example performance degradation of DSNG (RS = 6,666 MBaud) interfered with by M co-ordination signals, with L = 31. The ratio between the DSNG and each co-ordination channel spectral density divided by the spreading factor L has been assumed to be Γ = -3 dB, table 9 reports the meaning of the symbols. |
9988abb88967aabcacad0cb20508dd68 | 101 221 | 6 Conclusions | The present document provides an overview of the capabilities of the DVB specification for DSNG services (EN 301 210 [1] and EN 301 222 [2]). Several examples of the different configuration of the DSNG system and their corresponding co-ordination channels (modulation, symbol rate, coding rate, etc.) have been analysed for different potential applications (DSNG, fixed contribution links and connection with terrestrial networks). The DVB-DSNG system, thanks to its flexibility to accommodate the required conditions on ruggedness against noise, interference, power and spectrum efficiency, is a significant step forward toward the increasing in quality and cost reduction for SNG and fixed contribution links by satellite. ETSI TR 101 221 V1.1.1 (1999-03) 35 Bibliography The following material, though not specifically referenced in the body of the present document (or not publicly available), gives supporting information. Reimers, U: "The European perspectives on Digital Television Broadcasting". Proceedings NAB'93 Conference, Las Vegas. A. Morello, M. Visintin (1996): "Transmission of TC-8PSK digital television signals over Eurovision satellite links", EBU Technical Review No. 269. A. Viterbi et al. (1989): "A pragmatic approach to trellis-coded modulation", IEEE Communication Magazine. D. Delaruelle (1995): "A pragmatic coding scheme for transmission of 155 Mbit/s SDH and 140 Mbit/s PDH over 72 MHz transponders", Proceedings ICDSC-10 Conference, Brighton. INTELSAT: "IESS-310 Specification". A. Morello, V. Mignone (1998): "The New DVB Standard for Digital Satellite News Gathering", IBC'98 Conference, Amsterdam. J. K. Holmes, "Coherent Spread Spectrum Systems", Krieger Publishing Company, Malabar, Florida. R. De Gaudenzi, C. Elia, R. Viola (1992): "Bandlimited Quasi-Synchronous CDMA: A novel Satellite Access Technique for Mobile and Personal Communications", IEEE Journal on Selected Areas in Comm. Vol 10, No. 2, pp. 328-343. M. Barbero et alii: "Towards Digital Production and Storage of Compressed Video: How to Find the Right Path?", Broadcast Asia 96 Conference Records. A. Viterbi at alii (1989): "A pragmatic approach to trellis-code modulation", IEEE Comm. Magazine. A. Morello, M. Visintin (1996): "Transmission of TC-8PSK digital television signals over Eurovision satellite links", EBU Technical Review, No. 269. ITU-R Preliminary Draft New Recommendation ITU-R SNG 4SNG[XB]: "Common Operating Parameters to ensure interoperability of MPEG-2 DVB-S transmission of Digital Television News Gathering". ETSI TR 101 221 V1.1.1 (1999-03) 36 History Document history V1.1.1 March 1999 Publication ISBN 2-7437-2874-4 Dépôt légal : Mars 1999 |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 1 Scope | The goal of the present document is to give operators and manufacturers suitable advice for enabling practical operation of LMDS hardware equipment, planning antenna systems and geographical propagation. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 2 References | For the purposes of this Technical Report (TR), the following references apply: [1] ETSI EN 300 421: "Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for 11/12 GHz satellite services". [1a] ETSI EN 301 199 (V1.2.1): "Digital Video Broadcasting (DVB); Interaction channel for Local Multi-point Distribution Systems (LMDS)". [2] Electronics & Communication Engineering Journal, April 1997: "Characterization of propagation in 60 GHz radio channels" by P.F.M. Smulders and L.M. Correia. [3] H. Zuhrt: "Elektromagnetische Strahlungsfelder, Springer - Verlag". [4] ITU Radio Regulations/Revised Edition 1994. [5] DIN VDE 0848: "Sicherheit in elektrischen, magnetischen und elektromagnetischen Feldern", Teile 1 und 2. [6] G. Matthaei, L.Young, E.M.T. Jones: "Microwave Filters, Impedance-Matching Networks, And Coupling Structures" Artech House Microwave Library Inc. Norwood. [7] ETSI EN 300 429: "Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for cable systems". [8] ETSI ES 200 800: "Digital Video Broadcasting (DVB); DVB interaction channel for Cable TV distribution systems (CATV)". [9] CEPT/ERC/REC 13-04: "Preferred frequency bands for fixed wireless access in the frequency range between 3 and 29.5 GHz". |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 3 Abbreviations | For the purposes of the present document, the following abbreviations apply: AGC Automatic Gain Control AWGN Additive White Gaussian Noise BWS Broadband Wireless Systems DTH Direct-To-Home EIRP Effective Isotropic Radiated Power GPS Global Positioning System LMDS Local Multipoint Distribution System LNA Low Noise Amplifier MWS Multimedia Wireless Systems NVoD Near Video on Demand (= Time shifted equal contents) ETSI ETSI TR 101 205 V1.1.2 (2001-07) 8 4 Actual and Future Relations between LMDS and other Network Scenarios |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 4.1 Satellite Segments as an example | Nowadays the best-known satellite systems for TV transmission are the so-called geo-stationary satellite networks permitting the simple DTH distribution by using a 60 cm dish antenna for multi-program reception. The dominating frequency band is the so-called Ku band (10,7 GHz to 12,75 GHz down link) in Europe. Usual satellite segments are operating within this resource. These systems have similar transponder carrier positions and also the usable bandwidth is in most cases the same. Frequency re-use is achieved in a simple way by polarization and the directivity of the receive antenna. It is reasonable to expect that the number of satellite systems will increase rather than decrease in addition to the fact that new multi media applications will occupy a part of the whole satellite scenario with the consequence that the terrestrial last-mile scenario has to cope with this. E.g. the useful bit-rate I per transponder is given by: 204 188 2 × × × = m n R I Sy with RSy being the symbol rate, n/m depicting the convolutional code rate and 188/204 being the Reed-Solomon code rate in EN 300 421 [1] (DVB-SAT). E.g. if the convolutional code rate is set to 3/4 and the symbol rate is 27,5 MSy/s we obtain a useful bit-rate of 38 Mbit/s. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 4.2 CATV Networks as an example | CATV networks are determined by the QAM modulation in TV and by the in-band down-streams. This has to be noted when supplying the last mile with cable born contents. The frequency resource occupies approximately 800 MHz. The scenario of re-modulating satellite channels to cable is well-known and is done at IF. Thus no additional exotic equipment but rather truly off-the-shelf re-modulators can be implemented. E.g. the bit-rate for an in-band downstream and QAM is given by: 204 188 ) ( × × = M ld R I Sy with RSy again being the symbol rate. Now ld(m) expresses the number of bits used by an M-ary QAM alphabet (EN 300 429 [7] applies in this case). E.g. the symbol rate is given with 6,95 MSy/s (in an 8 MHz CATV channel) and the constellation shall be 64 QAM we also obtain a useful bit-rate of 38 Mbit/s. Thus a satellite channel like above can be re-modulated into this CATV channel or, similarly this cable downstream channel can be re-modulated into an LMDS embedded downstream of 27,5 MSy/s. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 4.3 Terrestrial Networks as an example | Terrestrial digital TV networks are operated using the so-called COFDM on-air. Despite this the "last mile" is bridged in most cases by the terrestrial service itself and situations are imaginable which require a re-modulation to LMDS. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 9 E.g. the bit-rate for terrestrial TV channels is given by: S U RS CONV s U T T CR CR b R R × × × × = with: Ru: The useful net data rate (Mbit/s); RS: The symbol rate; b: The number of bits per subcarrier; CRCONV: The inner (convolutional) code rate; CRRS: The outer (Reed-Solomon) code rate, 188/204 = 0,9216; TU: The duration of the useful symbol part; Ts: The entire symbol duration, including guard interval. E.g. if the symbol rate is 6,75 MSy/s (fitting into one 8 MHz UHF channel), the convolutional code rate is 3/4 , the modulation is QAM (4 bits/subcarrier) we obtain a useful net bit rate of 14,93 Mbit/s. The maximum possible DVB-T data rate is at 64 QAM, CRCONV = 7/8 and a guard interval of 1/32 indicated with 31,67 Mbit/s. In this maximum case one LMDS channel of e.g. 38 Mbit/s is filled with exactly one DVB-T channel. But due to the bad link budget for DVB-T this is expected to occur very seldom. On the other hand, the minimum DVB-T data rate can be at CRCONV = 1/2, QPSK modulation and a guard interval of 1/4 indicated with 4,98 Mbit/s. This means that the LMDS modulation scheme is wide enough also to contain one or more DVB-T channels within one of its channels. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5 Use of the LMDS Spectral Resource | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5.1 Capacity Comparison of the different Services | As described above the re–broadcast satellite or cable or terrestrial born TV channels would previously dominate the resource use. On the other hand the user of the last mile system really does not want a separate satellite antenna incorporating additional switching – and maintenance problems. Additionally the realization of interaction would become rather complicated. This means as a consequence that re-broadcasting will be a basic element of the last-mile scenario even when, at first, interaction is not demanded (MVDS). First, as an example, a possible bandwidth application is demonstrated which is possible to become a main candidate also for the last mile scenario. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 10 |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5.1.1 Re - Broadcasting of a first satellite space segment | Low Band (SUBSEG. 1D – 1B) H – Polar: 10,7 ... 11,7 GHz, sum: 1 GHz, Low Band (SUBSEG. 1D – 1B) V – Polar: 10,7 ... 11,7 GHz, sum: 1 GHz, Sum: 2 GHz High Band (SUBSEG. 1E – 1G) H – Polar: 11,7 ... 12,75 GHz, sum: 1 GHz, High Band (SUBSEG. 1E – 1G) V – Polar: 11,7 ... 12,75 GHz, sum: 1 GHz, Sum: 2 GHz As a whole: 4 GHz |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5.1.2 Re - Broadcasting of a second space segment | Low Band (SAT type 1,2,4, SUBSEGMENT I/II) H – Polar: 10,7 ... 11,7 GHz, sum: 1 GHz, Low Band (SAT type 1,2,4, SUBSEGMENT I/II) V – Polar: 10,7 ... 11,7 GHz, sum: 1 GHz, High Band (SAT type 2,3,4, SUBSEGMENT I) H – Polar: 11,7 ... 12,75 GHz, sum: 1 GHz, High Band (SAT type 2,3,4, SUBSEGMENT I) V – Polar: 11,7 ... 12,75 GHz, sum: 1 GHz, As a whole: 4 GHz This means, that if today's satellite space segments are reproduced by LMDS one would obtain 2 GHz per segment and polarization. However, the problem is now being discussed at the European regulation offices to extend the range of 40,5 GHz - 42,5 GHz to 43,5 GHz. This could, as one scenario, enable one full satellite segment re-broadcasting together with return channels for a sufficient number of subscribers. Table 1 shows an example of simulcasting a satellite transponder ("Backhaul Source", German Content) which is after transconversion laid upon one of the 40 GHz downstream channels. In this case the transponder "65" is alternatively shared by NVoD services and car race events ("Formel 1 Konfiguration") consuming certain highlighted bit rates. The NVoD services consist of time-shifted videos (feed 1 to 5) with 4,22 Mbit/s, the car race contents reveal different views of the race scenery like "Supersignal" (= Overview), "Cockpit" etc. with less compressed (5,44 Mbit/s) pictures. Tables like "Renndaten" (= race results) only carry very slow motion contents and are compressed to 2,44 Mbit/s. It is clearly shown that the whole data transport stream composes up to 38 Mbit/s at a convolutional FEC of 3/4 and a symbol rate of 27,5 Msy/s including Operating System Downloads for different set top boxes and data overheads for System Information (SI) and, optionally, Conditional Access (CA). In both cases a residual bandwidth ("Restbandbreite") is open for additional service insertion, intermediately filled with stuffing bytes. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 11 Table 1: Satellite Re-Broadcast SATELLITE TRANSPONDER SERVICE Provider Bit Rates DSF Plus Provider A 6,72 Mbit/s NvoD feed 1 Provider A 4,22 Mbit/s NvoD feed 2 Provider A 4,22 Mbit/s NvoD feed 3 Provider A 4,22 Mbit/s NvoD feed 4 (ab 1.11. Option f. 2. Stereokanal) Provider A 4,22 Mbit/s (4,44 Mbit/s) NvoD feed 5 Provider A 4,22 Mbit/s Daten – Overhead (SI/CA) Provider A 5,0 Mbit/s OS-Download 1/1 u. 2/3 QAM (Kabel) Provider A 0,6 Mbit/s Restbandbreite Provider A 4,58 Mbit/s (4,36 Mbit/s) 65 Down-Link Frequency 11,7195 GHz Polarization: II Symbol Rate: 27,5 Msy/s FEC: 3/4 Summe: 38 Mbit/s Supersignal Provider B 6,94 Mbit/s Verfolgerfeld Provider B 5,44 Mbit/s Cockpit Provider B 5,44 Mbit/s Boxengasse/Höhepunkte Provider B 5,44 Mbit/s Renndaten Provider B 2,44 Mbit/s Multisignal Provider B 5,44 Mbit/s Daten – Overhead (SI/CA) Provider B 5,0 Mbit/s OS-Download 1/1 u. 2/3 QAM (Kabel) Provider B 0,6 Mbit/s Restbandbreite Provider B 1,26 Mbit/s ASTRA 1E (Backhaul Source) 65 Formel I Konfiguration Summe: 38 Mbit/s Thus an LMDS base station can act as a satellite-like device providing the transmission service for different providers by using a plenty of backhaul sources. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5.2 Bandwidth On-Demand | Another possible spectrum use may be the broadcast of content to a user individually. This option is feasible because of the frequency re-use from one cell to another: the goal of this mode may be to use the resource most efficiently when e.g. contents being demanded very seldom can be transmitted via an individual small- bandwidth carrier instead of broadcasting the content to everybody. The remaining resource can then be used for other applications to provide contents. For this either individually a server is necessary in the base station or the content is downloaded e.g. during night time slowly from remote. Not included in this mode is content which has acceptance in the mass market i.e. when a large group of customers watches a famous film. In this case it is more efficient to give the event a common starting time i.e. a broadcast mode in the conventional sense. Also NVOD (Near Video On Demand) can then be used occupying a reasonable amount of spectrum. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 5.3 The Implementation of Return Channels for User Interaction | The implementation of return channels goes ahead with the worldwide trend for multimedia applications. At the present time when the present document is being laid out the situation is that certain return channel concepts exist. E.g. the cable return channel referred to ES 200 800 [8] is completely defined. Other concepts as e.g. the Satellite Return Channel are under work. ADSL is also a technique being promoted by some telcos but warnings concerning the electromagnetic impairments to the environment are being voiced. Thus, also LMDS must be tailored to this, expecting a large amount of user terminals and data throughput and with this, resource bandwidth. A specific statement about exact applications and numbers cannot be made at the present time, but it is certain that interactive traffic will be much more than only a "call from the user" to demand e.g. a film via a voice channel. Some examples of more wideband applications to be expected are: ETSI ETSI TR 101 205 V1.1.2 (2001-07) 12 • Video real time interaction. • Data download for entertainment purposes with customer friendly loading times. • Internet like applications with good real time behaviour. More similar applications are possible. The interaction process from the base station's site can appear either as a part of the broadcast downstreams, which is often referred to as embedded interaction, or as a separate radiated message called non-embedded interaction. Regardless of the progress being made in video compression techniques there will always be: • A limit for the reduction of picture data, • an immediate filling of resources by new services or subscribers being freed by additional compression capability. This shows that the return channel resource should be planned generously and with a certain future proof ness. |
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