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9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.1.4.2 Terminal performance | Terminal performance characteristics are mainly driven by the available resources inside the terminal like space and energy and in some way also from the level usage of state-of-the-art technology. In general, the following differentiation can be made for terminals having S-UMTS capability: For low-cost terminals with ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.1.5 Terminal extensions | In some cases an expansion with one or more extensions can be necessary or helpful. Terminal extensions can be situated at the network side to improve radio link characteristics or at the user side to improve user interaction with the terminal. For the connection between the terminal and the external device several wir... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.1.5.1 Network side terminal extensions | In places with high signal blocking, an external-RF module can improve both reception and transmission quality. Especially when direct transmission or reception to satellite is considered, an external antenna and high-power amplifier is advised to support higher data rates, unless the terminal already covers such capab... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.1.5.2 User side terminal extensions | A variety of external devices can be helpful to increase user comfort. The following list gives an impression of the possibilities: • Additional batteries or external power supply. • External and bigger screen. • External and more ergonomic keyboard. • Connection to PC. • Etc. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 45 |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2 Considered intermediate module repeater types (IMR) | Intermediate modules are network components placed and maintained by the network operator. In a S-UMTS network, their function is to significantly increase the coverage in areas where due to shadowing or blocking direct reception of the satellite signal is impossible. In general, 5 different Intermediate Module Repeate... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.1 Simple bi-directional IMR | Figure 6.8: Simple bi-directional IMR Utilization of fixed terrestrial IMR transmitting in the MSS band allocated to Space-to-Earth needs further clarification from a regulatory point of view. This IMR has a repeater function in both directions, meaning both downlink and up-link will be S-UMTS. The direct access archit... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.2 Simple unidirectional IMR | Figure 6.9: Simple unidirectional repeater The simple unidirectional IMR is a repeater only for the downlink. The up-link will be T-UMTS. This scenario has some advantages with respect to the simple repeater type 1: • The IMR complexity (and cost) will be greatly reduced, because the RF must only be capable of receivin... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.3 Simple IMR with a subset of node B functionalities | Figure 6.10: Simple IMR with a subset of node B functionalities This set-up also relates to the direct access scenario. Depending on the extra cost some node B functionalities could be implemented into the IMRs. Functionalities that could be interesting: • Power control • Multipath reception (Rake Rx) As indicated in f... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.3.1 Power control | Figure 6.11: W-CDMA power control mechanisms Power control is an essential feature of any CDMA based cellular system. The mechanism to be considered in this scenario is the inner loop power control (both up-link and down-link). It continuously adjusts the UE transmit levels in order to meet a specified SNR (depending o... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.3.2 Multipath reception | The channel between mobile and satellite does not have Rayleigh multipath characteristics. But if an IMR is included this module sees a multipath environment, exactly in the same way as in T-UMTS. These multipath characteristics can be exploited by incorporating a Rake receiver into the module. An advantage of putting ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.3.3 Comments | The strong increase in complexity and hence cost outweigh the gain in implementing power control in the IMR. Implementing power control implies (de)modulating capabilities and some decision-making software. Also the analogue part (RF/IF) will become more complex and thus expensive. The only actual gain is better fading... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.4 IMR with full Node B functionalities | Figure 6.12: IMR with full Node B functionality The difference with the architecture in 6.1.2.3 is that in this case the IMR has full Node B functionality and the interface between gateway and IMR is a whole different story. The question "which interface to use", is of course determining for the complexity of the modul... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.5 IMR with full Node B and RNC functionalities | Figure 6.13: IMR with full Node B and RNC functionality ETSI ETSI TR 101 865 V1.2.1 (2002-09) 49 This configuration could be interesting for the "UMTS island" scenario in the sense that the satellite link is responsible for the interface between the "island" and the UMTS core network. In some cases this could be much c... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.1.2.6 Conclusion | Table 6.2: Overview of different IMR scenarios IMR type Advantages Disadvantages Simple bi-directional IMR • Creation of a multipath environment • No extra load for the UTRAN • Good coverage • Terminals need an expensive satellite transceiver • No fast power control possible Simple unidirectional IMR • Reduced IMR cost... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2 Architecture and design aspects | Duplexing mode implementation consideration can be found in clause 8.1.2.8. |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1 Terminal functional modules | This clause will define and give a short overview on the different terminal modules that are implemented in the T/S-UMTS and FDD/TDD mode. The hardware and software necessary to support the applications will not be discussed. The (S-)UMTS services will require a certain flexibility in the terminal hardware. Changing pa... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.1 RF front-end and antenna | The RF and antenna clause is defined as the analogue clause of the terminal starting from the low IF interface at the output of the inner modem till the antenna. It is quite a challenge to design an RF section for a multi-standard (satellite and terrestrial) phone, because of the differences like Doppler conditions, HP... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.2 Inner modem hard - and software | We define the inner modem as all the functions performed at (oversampled) chipping rate and symbol rate like: spreading/de-spreading, scrambling/de-scrambling, low IF up-/down-conversion, Rake or PLL/DLL based reception and the runtime control of all these functions. To keep the requested degree of flexibility (T/S UMT... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.2.1 DSP based design | The DSP core offers the largest flexibility. It is clear that reprogramming loops and decisions on the fly can be implemented in software. In case you would like to pass from TDD to FDD duplexing or from S-UMTS to T-UMTS, the only thing you will need to do is to download the appropriate inner modem software. The bigges... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.2.2 Hardware design | To avoid the problem of a power hungry DSP based architecture, the second solution is to develop bigger hardware blocks that are clocked at lower speed. The power consumption of such hardware block will be reduced, but the requested flexibility to support the UMTS standard will not be present. The reconfiguration betwe... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.2.3 Reconfigurable hardware design | Both design techniques (DSP based and hardware based) have their own advantages and disadvantages. The aim of the reconfigurable hardware design technique is to combine the flexibility of a processor-based system and the low power aspect of a hardware based system. The hardware/software split is in this architecture le... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.3 Outer modem hardware and software | We define the outer modem as the architecture containing the following functionality: interleaving/de-interleaving, channel encoding like Turbo and Viterbi coding, rate matching, transport channel multiplexing and physical channel mapping. Like in the inner modem, the S-UMTS services will require certain flexibility fr... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.3.1 Hardware design | When the data of different transport and physical channels is handled in a serial way, no duplication of the data path is needed and power consumption will be lower then with a DSP solution. On the other hand, the data path will have an overhead of hardware due to the necessary flexibility for different data rates. Thi... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.1.3.2 Reconfigurable hardware design | In this approach, the split between hardware and software must be chosen very carefully to keep the microcontroller clock speed low instead of using a high speed DSP core to process the data flow. The control information communicated by higher layers will be processed by the software that will set the appropriate regis... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.2 Multi-standard and SDR | Compared to the current generation of terrestrial and satellite mobile phones, UMTS is characterized by an increased complexity, both from the air interface and the applications point of view. For this reason, a UMTS system on chip for the baseband functions includes much more functionality than today's 2G baseband ASI... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.3 Power consumption and low power aspects | Power consumption is one of the biggest challenges in 3G terminal design. Power hungry UMTS applications such as video-conferencing, always-on connections, games and m-commerce all put more pressure on battery life, as do hardware elements like graphically better screens and more powerful RF chips. The consumer wants a... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.3.1 Baseband | ASICs use less power than DSPs for equivalent performance because they employ fewer transistors and operate at slower speeds. Therefore power-hungry functions should be implemented in an ASIC. The key of low power design is to evaluate each component individually and how all the components work together as a system. Th... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.3.2 Analogue part | When the terminal is transmitting, the power amplifier dominates power consumption. Third generation use a different modulation scheme than GSM, although this improves bandwidth efficiency, it makes the amplifier less efficient. In this view, the up-link through GSM/GPRS seems more power-effective, but since the up-lin... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.3.3 Display | Another big power consumer is the display of a terminal. Three main areas of large power consumption are: lighting the display, data transfer to the controller and running higher colour depth. Innovations in these areas are reflective displays, low-temperature polysilicon TFT displays together with lower driving voltag... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4 IMR basic architecture and characteristics | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4.1 Architecture | This clause gives an overview of the basic architecture for the simple unidirectional IMR. The IMRs function is simply to receive, amplify and re-transmit the signal coming from the satellite towards the mobile. Therefore, the entire module can be kept analogue, since only RF-related functions have to be implemented. F... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4.2 Typical characteristics: | • Gain: 65 dB to 95 dB. • Output power: ±30 dBm. • Rx antenna gain: 24 dBi to 31 dBi. • Noise figure: 5 dB. • Most IMR feature Auto Limit Control (ALC) or Automatic Gain Control (AGC), an adjustable limit for the output power to be able to inhibit out of band gain and emissions, and to prevent self-oscillation. • Mecha... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4.3 Issues to be addressed when implementing a IMR (specifying requirements) | In terms of co-existence: • Out of band gain (or Adjacent Channel Gain, ACG): The frequency band in which the IMR amplifies has to be well controlled and shall cover the assigned band of the operator. The bandwidth and slope of the IF filter determine the degree of suppression of the unwanted channel outside the operat... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4.4 Remarks on frequency separation of donor link and service link | High power IMR used for large coverage areas might imply a frequency separation of both links, because the antenna isolation demand can become too strict. As we see it, for high power IMR a trade-off exists between extra effort in antenna isolation (shielding, highly directional Rx antenna pattern, etc.) and the need f... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 6.2.4.5 Special cases | Indoor IMR: Indoor reception will already be greatly improved by the outdoor IMR. Still, coverage dead zones might exist (e.g. in tunnels, underground parking lots, etc.). The IMR will take the outside-received signal and retransmits it inside a building. These IMR will be similar to the outdoor ones but will need less... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7 High level reference architectures | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.1 T-UMTS architecture | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.1.1 T-UMTS reference architecture | Figure 7.1 shows the basic domains in UMTS as described in TS 123.101 [3]. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 57 User Equipment Domain Access Network Domain Core Network Domain Infrastructure Domain Cu Mobile Equipment Domain USIM Domain Home Network Domain Transit Network Domain Uu Iu [Zu] [Yu] Serving Network Doma... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.1.2 UTRAN architecture | The UTRAN consists of a set of Radio Network Subsystems (RNS) connected to the Core Network through the Iu. A RNS consists of a Radio Network Controller (RNC) and one or more abstract entities currently called Node B. Node B are connected to the RNC through the Iub interface. A Node B can support FDD mode, TDD mode or ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2 S-UMTS architecture | Service interoperability is only one of the different levels of interoperability that characterize the positioning of S-UMTS with respect to T-UMTS. The service interoperability between the terrestrial and the satellite component can result from different architectures exhibiting different degrees of integration betwee... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.1 System impact | The architectures that will be analysed in this clause can be classified under two main categories: • Coverage oriented: - Direct access to satellite. - Indirect access to satellite. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 59 • Broadcast oriented: - Direct satellite reception. - Indirect satellite reception. For each sat... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.1.1 Coverage oriented | Due to the large coverage offered by satellites, the S-UMTS can complement the terrestrial component in the following roles: • Coverage completion: the terrestrial mobile systems deployment is long and largely controlled by the economics and demographics of the region concerned. The satellite component can be used to c... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.1.1.1 Direct access to satellite configuration | The services supported are basically the same as the one provided by the terrestrial component. Due to link budget characteristics, operation in indoor conditions is limited. Therefore dedicated techniques must be used to support paging while indoor. Nevertheless, the cost for the usage of the satellite component will ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.1.1.2 Indirect access to satellite configuration | Another way to consider the coverage problem is to design satellite systems that support any terminal compatible to the terrestrial component without modification. This requires inserting between the terminal and the satellite, an IMR. This module adapts the satellite signals to the terminal interfaces and vice-versa. ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.1.2 Broadcast oriented | The satellite component is based on similar transport capabilities provided by the S-UMTS, DAB and/or DVB technology. The end user benefits from the terrestrial component services and can simultaneously access the services offered by the satellite component using two possible terminal configurations: • Indirect access ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.2 Segments | A S-UMTS can be divided into three segments: a space segment, a user segment and a ground segment. The space segment is composed of one or several GSO satellites and/or by a constellation of non-GSO satellites, with or without Inter Satellite Links, its associated Tracking Control and Ranging (TCR) stations and Satelli... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.3 Satellite systems classification | Satellite systems can be classified as follows: a) Satellite constellation: GSO or NGSO. b) Single-hop or double-hop architecture. c) Bent-pipe or regenerative satellite. d) Inter-Satellite Links: ISL or non-ISL. A number of systems can be designed by combining the above parameters. However, the major impact on the UMT... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.4 GSO systems | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.4.1 GSO double-hop system | A double-hop satellite system based on a GSO constellation is shown in figure 7.10. Gateway RNC Node B Core Network Satellite Iu Uu Feeder links User links Gateway RNC Node B Feeder links Double hop call path: UE1 to Core Network to UE2 User segment Space segment Ground segment NCC Iur Figure 7.10: Double-hop, GSO mode... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.4.2 GSO single-hop system | A single-hop satellite system based on a GSO constellation is shown in figure 7.11. Gateway RNC Node B Core Network Satellite Iu* Uu* Feeder links User links Gateway RNC Node B Feeder links User segment Space segment Ground segment Single-hop call path: UE1 to UE3 NCC Iur Figure 7.11: Single-hop, GSO model for S-UMTS E... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.4.3 GSO S-UMTS system | Figure 7.12 illustrates an example of a GSO S-UMTS system. It consists of a geo-stationary transparent satellite payload, a number of gateways, network and satellite control centres, and the user terminals. Gateways SGF User segment NCC Handheld Terminal Vehicular Terminal Core Network GEO satellite Palmtop/Laptop Term... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.5 NGSO systems | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.6 NGSO single-hop system | A single-hop satellite system based on a LEO constellation with inter-satellite links is shown in figure 7.13. Uu Satellite Satellite Satellite Gateway [Yu] Gateway NCC User Equipment Domain Access + Serving + Home Network Domains Transit Network Domain Figure 7.13: Single-hop, regenerative, ISL, LEO model for S-UMTS I... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.6.1 NGSO double-hop system | The architecture that may be adopted for double-hop, bent-pipe, LEO system is shown in figure 7.14. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 69 Uu Satellite Satellite Satellite Gateway RNC Node B Iu CN Gateway RNC Node B NCC User Equipment Domain Access Network Domain Serving + Transit + Home Network Domains Figure 7.14: ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.7 Payload aspects | This clause presents the different levels of functionality that the space segment, and in particular the communication payload characteristics on-board the satellite, could offer and relate them to different system configuration and topology. The main functional added-values that the space segment can bring, additional... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.7.1 Transparent payloads | Transparent communication payloads can be split into two major families: • The bent-pipe type payload, which plays the role of an amplifier of RF signals that go through the satellite. • The processed type payload, also referred to as payload with transparent on-board processing, which provides, in addition to amplifyi... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.7.2 Hybrid payloads | A hybrid communication payload consists of a small capacity on-board regenerative processor aside a transparent payload (see figure 7.18). Hybrid payloads are originally used in broadcast-based satellite systems with or without satellite return channel, possibly evolving towards the provision of a mixed of DVB and Inte... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.7.3 Regenerative payloads | Regenerative payloads (illustrated in figure 7.20) are primarily characterized by the demodulation of telecommunication signals on board. Additionally, and according to the access scheme of the up-link (such as FDMA, MF-TDMA or CDMA), frequency de-multiplexing functions are required to separate different carriers; and,... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.7.4 Main advantages and drawbacks | Table 7.1 briefly summarizes the advantages and drawbacks of the main types of payload. Table 7.1: Main types of payloads - advantages and drawbacks Payload Type Advantages Drawbacks Bent-pipe with wide coverage High connectivity Robust and reliable technology Friendly to system evolution (i.e. no impact of protocol st... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 7.2.8 Gateway | In a typical S-UMTS system architecture the Gateway (GW) is interconnected to the Core Network (CN) through the Iu interface. No proprietary network is envisaged in between Radio Access Network (RAN) and CN. The Node B and RNC are the main UMTS entities gathered in the GW. One shall note that Node Bs - RNC interfacing ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8 UMTS/IMT 2000 Interface adaptation to S-UMTS | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1 Radio Interface (Uu) specifications for S-UMTS | The ETSI TC-SES S-UMTS/IMT-2000 working group will create air interface specifications for which there is enough interest from ETSI members. A natural set of candidates are the Radio Transmission Technologies (RTT) approved by ITU TG8/1 and ITU Radio Assembly (May 2000), but any other air interface compliant with the s... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.1 Review of ITU-R IMT-2000 Radio Transmission Technologies | According to ITU-R Recommendation M.1457 [14] and to the associated ITU-T Recommendation H.1455 [41], five Terrestrial Radio Interfaces (TRI) have been considered for the terrestrial component of IMT-2000 and six Satellite Radio Interfaces (SRI). The Terrestrial Radio Interfaces (TRI) are: 1) UTRA WCDMA, alias CDMA Dir... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2 Design considerations for S-UMTS air interfaces | Propagation conditions for satellite communication differ greatly from those commonly associated with terrestrial wireless systems. The much greater distances between the transmitter and receiver, Doppler effects, atmospheric attenuation, blocking, fading and multipath diversity, are just some of the characteristics of... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.1 Propagation channel characteristics | As for any wireless system, channel characteristics play a key role in the definition of an S-UMTS RTT. Note that propagation conditions are quite different for LEO/MEO/GSO S-UMTS with respect to T-UMTS. In fact, the T-UMTS channel is typically affected by lognormal long-term shadowing and by Rayleigh short-term multip... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.2 Doppler effect | Doppler effects are of relevance to S-UMTS because of the possible satellite rapid movement with respect to the gateway stations and user terminals. For LEO and most of MEO constellations satellite-induced Doppler is dominating over possible user terminal speed effects. User speed has still a major impact in determinin... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.3 Satellite diversity | Satellite diversity can provide benefits in terms of reduced blockage probability, soft and softer-handoff capability, slow fading counteraction, and under certain conditions even increased system capacity. First of all, the intuition that the probability of complete blockage greatly reduces with the number of satellit... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.4 Power control | In general we can say that power control is important for any mobile satellite network to maximize system efficiency and to maximize User Equipment (UE) battery lifetime. Although it is sometimes felt that the power control for TDMA is less important than for CDMA this opinion is debatable in view of the 3G networks ne... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5 Duplexing mode impact | In the following, we consider the impact of FDD, TDD and F/TDD duplexing modes in a third generation mobile satellite scenario. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 82 |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.1 Spectrum allocation | In Europe the spectrum allocation for MSSs including S-UMTS is (prior to WRC 2000): • 1 980 MHz/2 010 MHz (uplink); and • 2 170 MHz/2 200 MHz (downlink). This symmetric frequency allocation strongly impacts on the choice of the duplexing mode. The envisaged possibilities are hereafter reported. - FDD: standard approach... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.2 Asymmetric traffic handling | Asymmetric traffic occurs when the traffic volume sent in one direction (normally the downlink) is much larger than the volume sent in the other (normally the uplink) direction. Handling such asymmetry is a crucial point for S-UMTS to avoid spectrum usage inefficiencies. Examples of asymmetric traffic sources are file ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.3 Asynchronous traffic management | In the return link, asynchronous traffic occurs whenever a MT tries to access the BS without being time aligned to the return link frame structure. Initial access at start-up, connection restoring procedures, transmission of data packets in connectionless mode are all examples of asynchronous traffic generation. - FDD:... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.4 On Board Processing | - FDD: both regenerative and transparent payload solutions are possible. - TDD: a purely transparent payload is not feasible, since the satellite must know at least the switching point of the incoming traffic. - F/TDD: as for FDD. |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.5 Channel Reciprocity | - FDD: channel reciprocity is weak, open loop power control is scarcely efficient. - TDD: one of the major claims for systems operating in TDD mode is that they can exploit channel reciprocity to implement signal pre-distortion, antenna pre-selection and efficient open loop power control. However it has to be underline... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.6 Delay variation | The end-to-end delay td is not fixed for satellite systems employing satellites in LEO and MEO orbits. The satellite motion with respect to the ground results in the time variation of the slant range (the distance between the mobile terminal and the satellite). Vs S1 S2 S3 Vs Vs Figure 8.3: Slant Range/Delay Variation ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.7 End to End delay | The end-to-end delay is not affected by the duplexing scheme if we assume that in TDD higher bit rates (and power) are used to transmit all the information over the half of the frame that is used for a FDD transmission and that the total amount of spectrum is the same in both cases. |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.8 Interference Aspects in different duplex modes | The comparison and evaluation of the duplexing methods reveals some interference problems to be handled when TDD schemes are used. 8.1.2.5.8.1 Interference From TDD Power Pulsing If fast power control frequency with open loop is desired to support higher Doppler shifts, then short TDD frames must be used. The short tra... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.9 Implementation Issues | From an implementation point of view, FDD systems require two synthesizers on transmitter and receiver side due to simultaneous operation. In addition a tight duplex filter must be used to prevent transmitter signal leaking to receiver side. In contrast to TDD systems a single synthesizer and no expensive duplex filter... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.5.10 Modem configuration | 8.1.2.5.10.1 Duplexer - FDD: duplexers are needed to achieve the required tx and rx frequency separation. In a satellite receiver, high quality (low loss => large size) duplexers are desirable to achieve a large G/T ratio for the given required frequency separation. However, in a MT the duplexer size is heavily constra... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.6 Synchronization issues | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.6.1 Inter-beam synchronization | - FDD: forward link frame synchronization among beams is not necessary. It can be introduced to reduce interference and/or simplify interference cancellation. - TDD: due to imperfect inter-beam isolation, the forward and reverse traffic flows through different beams using the same frequency must be frame synchronous an... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.6.2 Intra-beam reverse link frame synchronization | - FDD: no reverse link frame synchronization reference needed for dedicated channels. For common channels, which are time shared, time synchronization reference is required. See TDD. - TDD: a time synchronization reference is needed to realize a frame-synchronous return link. In satellite environments, time/frequency r... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.6.3 Code synchronization: tracking | - FDD: the pilot signal can be used for efficiently tracking the code epoch. - TDD: due to the burst nature of transmission, tracking can become a difficult task. In particular tracking loops may lose lock during transmitting periods. - F/TDD: same as for TDD. |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.7 Interworking | Future S-UMTS satellite systems will be required to interwork with their terrestrial-based counterparts (i.e. mobile stations, mobile terminals, gateways). This implies interworking at the level of supported services, network protocols, and clearly the mode of operation (i.e. TDD/FDD). This clause mainly concentrates o... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.7.1 Interworking between Terrestrial and Satellite systems | It should be expected that a good part of the success or failure of S-UMTS will depend on its capacity to efficiently integrate with the T-UMTS system. This consideration strongly impacts on the selection between the FDD or TDD approaches in that, from a physical layer point of view, full integration with T-UMTS transl... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.7.2 Inter-Operator Interference Considerations | If there are several operators offering the service in the same geographical area in the TDD band, base station synchronization for the different operators is required and asymmetry flexibility between uplink and downlink becomes considerably more difficult. Asymmetric TDD-CDMA systems are therefore not well suited if ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.8 Terminal implementation considerations | Eventually add this clause in the terminal clause or put a reference to this clause. At this moment, a limited set of physical layer specifications are produced by the ETSI SES S-UMTS WG. Unfortunately, they only deal with an FDD mode for S-UMTS, which follows closely the terrestrial UMTS/FDD. Therefore, initial compar... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.8.1 RF front-end and antenna | Some issues related to RF front end are: • In TDD mode, no duplexer is needed to separate uplink and downlink as it is the case in FDD. • Due to the bursty nature of TDD transmissions, a higher amount of electromagnetic interference has to be expected. ETSI ETSI TR 101 865 V1.2.1 (2002-09) 92 • The RF module of a termi... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.8.2 Inner modem | The following parameters are identical for both TDD and FDD modes: • Channel spacing: 5 MHz. • Chipping rate: 3,84 Mcps. • Frame length: 10 ms. • Frame structure: 15 timeslots/frame. • Downlink modulation: QPSK. • Pulse shaping filter: rooted raised cosine (RRC) with roll-off equal to 0,22. • Channelization codes: real... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.8.3 Outer modem | This clause will give an overview of the differences in implementation between FDD and TDD mode for the outer modem. For both uplink and downlink, the second interleaving must be expanded from frame interleaving to frame and timeslot related interleaving. The physical channel mapping and demapping will be put in additi... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.1.2.9 Recommendations | From the previous discussion, it appears that the selection of the duplexing technique constitutes a rather difficult decision. There are a number of aspects to be taken into consideration, and for each aspect there are advantages and disadvantages for any technique. However, it may be appropriate to critically review ... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.2.1 Analysis of USIM and S-UMTS requirements | At the time of writing this report some 3rd Generation USIM details were yet to be specified. However, an initial analysis of the TS 131.102 [5] entitled "Characteristics of the USIM Application" has revealed that certain S-UMTS parameters should be added to the proposed USIM. The results from this analysis are shown i... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.3 Core Networks interfaces | |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.3.1 Interface with the UMTS core network (Iu) | Depending on the architecture of the satellite system (e.g. GSO, non-GSO, single-hop, double hop, ISL, non-ISL, etc.) different solutions shall be implemented when interfacing the satellite system with the core network (CN) (see clause 7 in the present document). For example, in the double-hop scenario (for both GSO an... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.4 IMS and MBMS | CORE NETWORK GATEWAY USRAN Intermediate Module (GAP FILLER) Niche Market Forward Link Forward Link Return Link Return Link Direct access Baseline (I) + Optional (II) BASE STATION UTRAN Mass Market Multicast and broadcast traffic Indirect access Baseline (I) Rural/Maritime/Aviation /Remote environments Urban/Suburban En... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.5 Packet-mode and S-UMTS | The satellite environments impose extra difficulties in the packet mode support, at least the way it is implemented in T-UMTS, arising mainly from the higher propagation delays and the larger cell sizes related to satellite systems. The interaction of the satellite environments and the UMTS packet-mode can be summarize... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.6 Multicast | The broadcast/multicast case in media with inherent broadcast capabilities is a significantly different case from the conventional implementation of broadcast/multicast over networks consisting of point-to-point links. A great deal of the complexity and difficulty arising in multicast support in the wireline networks h... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.6.1 Multicast in an all-IP CN | The adoption of Mobile IPv6 in the CN makes more straightforward (or even mandatory) the application of IP-derived solutions for multicast support: Multicast capable routers can be deployed at the CN for more efficient multicast transport. IGMP can/must be used for group management purposes. For the unidirectional link... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.6.1.1 The tree-like topology of the network and the IGMP proxying principle | The aforementioned signalling load and the respective resource consumption can be avoided in certain topologies. This is the main reason why the "IGMP proxying" (IGMP-based Multicast Forwarding) technique was conceived. With respect to its position in the multicast spanning tree, the router interfaces can be divided in... |
9c93b22846a27ede6d6f94031adc745f | 101 865 | 8.6.1.2 The LAN-like nature of the network | Rather than implying a strict resemblance the similarity refers to the capability of all the hosts within a beam to receive all transmissions destined for this beam. This capability can be exploited in reducing the number of exchanged IGMP messages over the air interface. Rather than letting every mobile host (MH) send... |
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