Chapter 10: CROSS-LAYER METHODS AND STANDARDIZATION 329 techniques, especially in the return link for terminals with small antennas. The adoption of spectrum spreading is a possible solution to reduce the EIRP, while preserving the required SNR, at the expenses of reduced spectral efficiency. In the forward link, the introduction of spreading requires the design of a new DVB-S2 receiver. In the return link, each terminal could in principle implement direct spreading within the assigned time and frequency slot (MF-TDMA approach). • Fading countermeasures: the more challenging propagation conditions of the non-LoS scenario can be mitigated by adopting advanced techniques such as diversity and higher layer FEC schemes. Moreover, new synchro- nization acquisition and maintenance procedures need to be employed to cope better with frequent fades. • Resource management techniques: efficient RRM schemes need to be adopted to account for mobility, such as: impact of spreading on the MF-TDMA allocation process (DVB-RCS); support of handover requests with suitable protocols; interworking with terrestrial networks in shadowed areas (e.g., tunnels, cities, etc.) where gap fillers can be used; adaptive schedulin techniques for the forward link that are aware of the physical layer behavior. All these innovative aspects require a cross-layer system design aiming at optimizing the choices made at different layers. The DVB-TM is now working to specify the modifications that are needed for the mobile extension of the DVB-S2 standard [23]. The SatNEx II project [24] is actively involved in this standardization process. DVB-H The broadcast of digital television signals was originally targeted to fixed reception, although mobile reception is also feasible with current digital television standards (DVB-T, DVB-S2). The Commercial Module of DVB decided to launch commercial requirements for the production of ad hoc specifications able to provide broadcasting to one specific niche of the mobile receivers: handheld terminals. This is the aim of the DVB-Handheld (DVB-H) standard. Conditional access is important in all broadcast radio/satellite networks to prevent unauthorized access to the broadcast content by eaves-dropping. In DVB-H, an IP-based Conditional Access System (IP-CAS) can provide link-layer encryption (scrambling) for DVB-H services. CAS messages are delivered over IP and may take advantage of time-slicing to save power at a receiver. The DVB common scrambling algorithm on Transport Stream packets is also employed (DVB-CAS): it uses entitlement control messages to send keys to receivers and entitlement management mode messages to deliver management messages. 330 G. Fairhurst, M. A. V´azquez Castro, G. Giambene 10.6.5 International Telecommunication Union ITU is an international organization of the United Nations where governments and industries coordinate global telecom networks and services. ITU is divided in three sectors: ITU-T that aims at the definition of high-quality standards covering all fields of telecommunications; ITU-R that plays a fundamental role in the management of the radio-frequency spectrum, physical layer issues, and satellite orbits; and ITU-D, dealing with Telecommunications Developments. ITU-R is charged with determining the technical characteristics and operational procedures for a huge and growing range of wireless services. This Sector also plays a vital role in the management of the radio-frequency spectrum, a finite natural resource that is increasingly in demand due to the rapid development of new radio-based services and the enormous popularity of mobile communication technologies. In its role as global spectrum coordinator, ITU-R develops and adopts the Radio Regulations, a voluminous set of rules that serve as a binding international treaty governing the use of the radio spectrum for different services around the world. ITU-R also acts, through its Bureau, as a central registrar of international frequency use, recording and maintaining the Master International Frequency Register, which currently includes around 1,265,000 terrestrial frequency assignments, 325,000 assignments servicing 1,400 satellite networks, and another 4,265 assignments related to satellite Earth stations. Moreover, ITU-R is responsible for coordinating efforts to ensure that commu- nication, broadcasting and meteorological satellites in the world’s increasingly crowded skies can co-exist without causing harmful interference each other. The Union facilitates agreements between both operators and governments, and provides practical tools and services to help frequency spectrum man- agers. The portion of the radio-frequency spectrum suitable for communications is divided into ‘blocks’, the size of them varying according to individual services and their requirements. These blocks are called ‘frequency bands’ and are allocated to services on an exclusive or shared basis. The full list of services and frequency bands allocated in different regions forms the Table of Frequency Allocations, which is a part of the radio regulations. 10.7 Conclusions A range of cross-layer optimization techniques have been proposed and evaluated in this book for three different scenarios (i.e., DVB-S/DVB-RCS via GEO bent-pipe satellite, S-UMTS via GEO bent-pipe satellite, and LEO constellation with regenerating satellites). The most significant techniques have been summarized in this Chapter to provide final guidelines for both standardization efforts and further research directions. Cross-layer methods have been categorized, considering: (i) either explicit Chapter 10: CROSS-LAYER METHODS AND STANDARDIZATION 331 signaling or an implicit scheme with a joint optimization of different protocol layers; (ii) the definition at higher layers of requirements to be used for ap- propriate settings at lower layers or, vice-versa, the lower layers progressively determining the requirements at higher layers. As for explicit cross-layer, we have described different mechanisms for the exchange of internal protocol state information between non-adjacent protocol layers, thus violating the classical ISO/OSI layered philosophy. We have proved that the cross-layer techniques can improve the overall end-to-end quality of service, while optimizing the efficiency in utilizing the scarce satellite radio resources. However, standardization fora have not yet significantly addressed cross-layer issues. To this aim, there is a need for a new framework, as well as the strong cooperation of different standardization bodies. One of the aims of this book has been to provide some useful insights that may promote new standardization activities on cross-layer air interface design for satellite communication networks. References [1] J.H.Saltzer,D.P.Reed,D.D.Clark,“End-to-EndArgumentsinSystem Design”, ACM Transactions in Computers Systems, Vol. 2, No. 4, pp. 277-288, November 1984. [2] P. Karn, C. Bormann, G. Fairhurst, D. Grossman, R. Ludwig, J. Mahdavi, G. Montenegro, J. Touch, L. Wood, “Advice for Internet Subnetwork Designers”, BCP 89, IETF RFC 3819, July 2004. [3] S. Floyd, V. Jacobson, “Random Early Detection Gateways for Congestion Avoidance”, IEEE/ACM Transactions on Networking, Vol. 1, No. 4, pp. 397-413, August 1993. [4] M. van der Schaar, S. Shankar, “Cross-Layer Wireless Multimedia Transmission: Challenges, Principles, and New Paradigms”, IEEE Wireless Communications Magazine, Vol. 12, No. 4, pp. 50-58, August 2005. [5] Q. Wang, M. A. Abu-Rgheff, “Cross-Layer Signalling for Next-Generation Wireless Systems”, in Proc. of IEEE Wireless Communications and Networking Conference 2003 (IEEE WCNC 2003), New Orleans, USA, pp. 1084-1089, March 2003. [6] The Internet Engineering Task Force (IETF); Web page with URL: http://www.ietf.org. [7] European Telecommunications Standards Institute (ETSI); Web page with URL: http://www.etsi.org. [8] International Telecommunication Union; Web page with ULR: http://www.itu.int/home/index.html. [9] MoSSA, Advanced Satellite Mobile Systems-Task Force Specific Support Action, Project IST-507557, Deliverable “Survey on Standardization and Regulatory Activities”; Web site with URL: http://asms1.wss.bcentral.com/mossa/default.htm. [10] ETSI TC-SES working group; Web page with URL: http://portal.etsi.org/ses/. [11] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 1: Physical channels and mapping of transport channels into physical channels (S-UMTS-A 25.211)”, TS 101 851-1. [12] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 2: Multiplexing and channel coding (S-UMTS- A 25.212)”, TS 101 851-2. 334 G. Fairhurst, M. A. V´azquez Castro, G. Giambene [13] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 3: Spreading and modulation (S-UMTS-A 25.213)”, TS 101 851-3. [14] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 4: Physical layer procedures (S-UMTS-A 25.214)”, TS 101 851-4. [15] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 5: UE Radio Transmission and Reception (S- UMTS-A 25.101)”, TS 101 851-5. [16] ETSI, “Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT2000; G-family; Part 6: Space Segment Radio Transmission and Reception (S-UMTS-A 25.104)”, TS 101 851-6. [17] IST-MAESTRO project, “Mobile Applications & sErvices based on Satellite & Terrestrial inteRwOrking”; Web site with URL: http://ist-maestro.dyndns.org, 2006. [18] ETSI, “Evaluation of the OFDM as a Satellite Radio Interface Satellite Earth Stations and Systems (SES); Satellite Component of UMTS/IMT-2000”, TR 102 433, 2006. [19] Digital Video Broadcasting (DVB) Project; Web page with URL: http://www.dvb.org. [20] ETSI, “Digital Video Broadcasting (DVB); Interaction channel for Satellite Distribution Systems”, EN 301 790. [21] SatLabs official Web site with URL: http://www.satlabs.org/. 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Index A Access protocol, 120, 132 Adaptive algorithms, 209, 295 Adaptive coding and modulation, 16, 24, 106, 139, 208, 316 Asynchronous transfer mode, 109 B Broadband satellite multimedia, 28, 31, 69, 98, 256 Broadcast and multicast services, 5, 80, 152, 160 C CAC, 45, 51, 100, 110, 177, 179, 184, 189, 199, 257 Complete partitioning, 52, 179 Complete sharing, 52, 179 Call handover, 53, 189, 195, 214, 233 Inter-satellite handover, 54, 190, 194, 214 Intra-satellite handover, 54, 190, 191, 214 CDMA, 14 Channel quality indicator, 138 Channel utilization, 162, 305 Combined free/demand assignment multiple access, 48, 101, 256 Commercial solutions, 82, 89 Communications architecture, 314, 320 Cross-layer signaling, 320 Congestion control, 164, 186 Control-theoretic approach, 213 Cross-layer approach, 34, 156, 164, 256, 314 Bottom-up approach, 316 Hybrid approach, 317 Top-down approach, 316 Cross-layer design, 35, 36, 45, 96, 105, 214, 221, 256, 270, 313, 314 Explicit cross-layer, 35, 36, 133, 145, 156, 164, 300, 315 Implicit cross-layer, 35, 36, 45, 95, 217, 270, 290, 315, 317 D Delayed real-time services, 83 Demand assignment multiple access, 18, 290, 298, 300 Access delay, 290, 298 Rate-based dynamic capacity, 20, 211, 221, 249, 299 Volume-based dynamic capacity, 20, 211, 221, 249, 299, 303 DiffServ, 36, 77, 107, 183, 246 DVB-S, 16, 80, 105, 187, 326 DVB-RCS, 17, 81, 186, 211, 249, 289, 298, 323, 327 Adaptive coding, 218 Implementation issues, 218, 228 MF-TDMA scheme, 15, 17, 184, 211, 251, 302, 327 E ETSI TC SES S-UMTS working group, 15, 121, 325 336 Index Explicit congestion notification, 107 F FDMA, 13 G GEO satellite systems, 4, 10, 68, 71, 125, 131, 141, 184, 209, 265, 290 H Handover algorithms, 51 Handover queuing, 53 Predictive resource reservation, 54 HSDPA, 16, 108, 138, 139, 141, 144, 148 Hybrid satellite networks, 265 Erasure codes, 265 QoS, 266 WiFi networks, 267 I Infinitesimal perturbation analysis, 99, 216, 257 IntServ, 36, 77, 107, 183, 244 L LEO satellite systems, 4, 10, 54, 68, 71, 132, 141, 189, 192, 195 M MAC, 18, 97, 98, 105, 110, 119, 139, 248, 256, 298 MEO satellite systems, 4, 10, 48, 71, 141 Modeling and simulation, 54 N NCC, 17, 178, 208, 298, 327 Network layer, 243 Node-B, 139 O OSI model, 34, 102 P Packet scheduler, 134, 137, 140, 152, 155, 164 Performance enhancing proxies, 29, 99, 293 Power allocation and control, 50 Closed loop, 50 Feedback loop, 50 Open loop, 50 Proactive algorithms, 210 Q QoS classes, 156, 165 QoS for multimedia services, 68 Background services, 76 Conversational services, 70 Interactive services, 73 Performance requirements, 70, 73, 74, 76 QoS based IP models, 76 Streaming services, 74 QoS mapping, 98, 256, 260 R Radio resource management, 43, 54, 96, 101, 119, 177, 289, 303, 318 Cross-layer approach, 45, 60, 96, 99, 101, 104, 214, 295, 303, 305 Joint optimization, 95, 97–100 MAC-centric approach, 105 Dynamic allocation, 20, 47, 49, 55, 99, 101, 110, 191, 198, 208, 211, 213, 214, 218, 233, 248, 251, 256, 299 Fairness, 44, 217, 232 Reactive algorithms, 210 Receding horizon controller, 214 Resource allocation, 23, 46, 99, 121, 138, 158, 179, 184, 208, 225, 249, 299 Frequency allocation, 46 Space allocation, 46 Time allocation, 46 S S-UMTS, 15, 58, 108, 121, 131, 152, 325 Satellite constellations/orbits, 4, 10, 275 Satellite digital multimedia broadcasting, 325 Satellite IP networks, 31, 69, 76, 109, 248 Index 337 IP QoS, 76, 109, 183, 244, 248 Proportional DiffServ, 249 Scheduling scheme, 134 Channel-aware scheduling, 135 Exponential Rule scheduler, 138 Maximum C/I scheduler, 138 Proportional Fair scheduler, 138, 147 Service level agreement, 96, 222, 246 SI-SAP, 31, 98, 256 Smith predictor controller, 214 Standardization, 322 Static algorithms, 209 T TCP over satellite, 290 Cross-layer interactions, 294, 298 MODCOD optimization, 294 TDMA, 13 Transport layer, 99, 289 Congestion control, 291 TCP, 99, 273, 290, 294, 298 UDP, 273, 290, 305 U UMTS, 15, 58, 121 V VLANs for LEO constellations, 270 Voice over IP, 50, 70, 262 W W-CDMA, 16, 46, 137 . efficiency. In the forward link, the introduction of spreading requires the design of a new DVB-S2 receiver. In the return link, each terminal could in principle implement direct spreading within the. huge and growing range of wireless services. This Sector also plays a vital role in the management of the radio-frequency spectrum, a finite natural resource that is increasingly in demand due. technologies. In its role as global spectrum coordinator, ITU-R develops and adopts the Radio Regulations, a voluminous set of rules that serve as a binding international treaty governing the use