234 Tommaso Pecorella, Giada Mennuti
into account, whereas, in the second one, other motion components, like Earth rotation and user movements, are considered. The key idea of the algorithm is that, in order to prevent handover failure during a call, bandwidth will be reserved in a particular number S of spot-beams that the call would handover into.
In , a probabilistic resource reservation strategy for real-time services was proposed. The sliding window concept is adopted to predict the nec-essary amount of reserved bandwidth for a new call in its future handover spot-beams. As for real-time services, a new call request is accepted if the originated spot-beam has available bandwidth and resource reservation is successful in future handover spot-beams. As for non real-time service, new call requests are accepted if the originated spot-beam satisﬁes its maximum required bandwidth.
In ,, a selective look-ahead strategy is proposed where real-time and non-real time service classes are diﬀerently treated. Bandwidth allocation only pertains to real-time connection handovers. To each accepted connection, bandwidth allocation is performed in a look-ahead horizon of k cells along its trajectory. This algorithm oﬀers low call dropping probability, i.e., a reliable management of call handovers of and acceptable call blocking probability for new calls.
This Chapter has presented a set of dynamic bandwidth allocation techniques and identiﬁed associated research topics. We can conclude this Chapter by highlighting these two types of DBA problems and related techniques:
• Handover-constrained techniques, mainly used for LEO satellites, where the main problem is to acquire a resource among a number of diﬀerent satellites, since the communication lifetime is long enough to require a number of handovers;
• Bandwidth-constrained techniques, aﬀecting mainly GEO systems, where the main issue is to cope with the high delay-bandwidth product that makes the reactive approaches unfeasible for delay-constrained traﬃc types.
The problem of multi-tier satellite systems, i.e., satellite systems using a combination of multiple orbital systems, like GEO+LEO, has not been considered, but it could be challenging, due to the multiple use of the diﬀerent techniques among the various tiers. This problem requires further investigations as it involves also intra-tier and inter-tier routing schemes.
Most of the described DBA techniques are inherently satellite-dependent; each satellite system should adapt or implement its own techniques in order to maximize system eﬃciency. A common theme is that optimizing ‘eﬃciency’ does not always means maximizing the bandwidth occupancy, but it is
Chapter 7: DYNAMIC BANDWIDTH ALLOCATION 235
a concept more related to fulﬁlling the system goals in terms of QoS, user satisfaction and, ultimately, system capacity to maximize the network operator’s revenue. Hence, one of the possible approaches to further study DBA techniques is to embed a cost-function into the DBA decision process, in order to introduce an abstraction layer between the raw user bandwidth requests and the actual bandwidth allocation decision algorithms.
Another topic that needs further investigation is represented by the fair-ness of the proposed techniques. Most techniques that involve terminal-based decisions (like in most DVB-RCS systems) can be heavily aﬀected by fairness issues in a multi-vendor and multi-algorithm environment, thus creating serious issues in real-world deployments. At present, this problem is still an open point and should be addressed either by allowing the centralized decision process to take into account the diﬀerent behaviors, or by deﬁning some fairness threshold that every user equipment implementation must comply with. We must observe that the ﬁrst option is not viable in the long-term, as it requires extra-work in the bandwidth allocation decision unit, along with the knowledge of every implementation, and this is not always possible. The second option requires the deﬁnition of precise fairness metrics and test suites to certify the user terminal fairness.
The DBA implementation is therefore a key element for the eﬃcient oper-ation of many satellite systems. Design choices in DBA techniques can greatly impact the overall system performance, and the evolution of appropriate techniques and analysis methods will remain important research topics for future generations of systems.
 K. W. Ross. Multiservice Loss Models for Broadband Telecommunication Networks. Springer-Verlag, London, UK, 1995.
 H. J. Chao, X. Guo. Quality of Service Control in High-Speed Networks. Wiley, New York, NY, 2002.
 J. Walrand, P. Varaiya. High-Performance Telecommunication Networks, 2nd Ed., Morgan Kaufmann. San Francisco, CA, 2000.
 M. H. Ahmed, “Call Admission Control in Wireless Networks: a Comprehensive Survey”, IEEE Communications Surveys and Tutorials, Vol. 7, No. 1, pp. 50-69, 1st Quarter 2005.
 F. Chiti, R. Fantacci, D. Tarchi, S. Kota, T. Pecorella, “QoS Provisioning in GEO Satellite with Onboard Processing Using Prediction Algorithms”, IEEE Wireless Communications Magazine, Vol. 12, No. 5, pp. 21-27, October 2005.
 P. Todorova, S. Olariu, H. N. Nguyen, “A Two-Cell-Lookahead Call Admission and Handoﬀ Management Scheme for Multimedia LEO Satellite Networks”, in Proc. of the 36th Hawaii International Conference on System Sciences (HICSS-36), Big Island, Hawaii, 2003.
 ETSI, “Digital Video Broadcasting (DVB); Interaction channel for satellite distribution system”, EN 301 790, 2005.
 ETSI, “Digital Video Broadcasting (DVB); Interaction channel for satellite distribution system; Guidelines for the use of EN 301 790”, TR 101 790, 2006.
 A. Morell, G. Seco-Granados, M. A. V´azquez-Castro, “Joint Time Slot Optimization and Fair Bandwidth Allocation for DVB-RCS Systems”, in Proc. of the IEEE GLOBECOM 2006, San Francisco, California, USA, November 27 - December 1, 2006.
 J. Neale, A. K. Mohsen, “Impact of CF-DAMA on TCP via Satellite Performance”, in Proc. of the Global Telecommunications Conference 2001 (GLOBECOM ’01), Vol. 4, pp. 2687-2691, November 2001.
 L. Chisci, R. Fantacci, T. Pecorella, “Predictive Bandwidth Control for GEO Satellite Networks”, in Proc. of IEEE International Conference on Communications (ICC 2004), Paris, France, pp. 3958-3962, June 2004.
 L. Chisci, R. Fantacci, T. Pecorella, “Strategies for Distributed Bandwidth Control in Communication Networks with High Bandwidth Delay Product”, in Proc. of the 43rd IEEE Conference on Decision and Control, Atlantis, Paradise Island, Bahamas, Vol. 4, pp. 3732-3737, December 2004.
238 Tommaso Pecorella, Giada Mennuti
 L. Chisci, T. Pecorella, R. Fantacci, “Dynamic Bandwidth Allocation in GEO Satellite Networks: a Predictive Control Approach”, Control Engineering Practice, Vol. 14, No. 9, pp. 1057-1067, September 2006.
 K. Nichols, S. Blake, F. Baker, D. Black, “Deﬁnition of the Diﬀerentiated Services Field (DS Field) in the IPv4 and IPv6 Headers”, IETF RFC 2474, Dec. 1998.
 S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, “An Architecture for Diﬀerentiated Services”, IETF RFC 2475, December 1998.
 B. Davie, A. Charny, J. C. R. Bennett, K. Benson, J. Y. Le Boudec, W. Courtney, S. Davari, V. Firoiu, D. Stiliadis, “An Expedited Forwarding PHB (Per-Hop Behavior)”, IETF RFC 3246, March 2002.
 D. Grossman, “New Terminology and Clariﬁcations for Diﬀserv”, IETF RFC 3260, April 2002.
 S. Karapantazis, P. Todorova, F. N. Pavlidou, “On Bandwidth and Inter-Satellite Handover Management in Multimedia LEO Satellite Systems”, Advanced Satellite Mobile Systems Conference 2006 (ASMS 2006), Herrsching am Ammersee, Germany, May 29-31, 2006.
 N. Celandroni, F. Davoli, E. Ferro, “Static and Dynamic Resource Allocation in a Multiservice Satellite Network with Fading”, International Journal of Satellite Communications and Networking, Special Issue on Satellite IP Quality of Service, Vol. 21, No. 4-5, pp. 469-487, July-October 2003.
 N. Celandroni, F. Davoli, E. Ferro, A. Gotta, “Adaptive Cross-layer Bandwidth Allocation in a Rain-faded Satellite Environment”, International Journal of Communication Systems, Vol. 19. No. 5, pp. 509-530, June 2006.
 F. Davoli, M. Marchese, M. Mongelli, “Optimal Resource Allocation in Satellite Networks: Certainty Equivalent Approach Versus Sensitivity Estimation Algorithms”, International Journal of Communication Systems, Vol. 18, No. 1, pp. 3-36, February 2005.
 F. Davoli, M. Marchese, M. Mongelli, “Discrete Stochastic Programming by Inﬁnitesimal Perturbation Analysis: the case of Resource Allocation in Satellite Networks with Fading”, IEEE Transactions on Wireless Communications, Vol. 5, No. 9, pp. 2312-2316, September 2006.
 M. Baglietto, F. Davoli, M. Marchese, M. Mongelli, “Neural Approximation of Open-Loop Feedback Rate Control in Satellite Networks”, IEEE Transactions on Neural Networks, Vol. 16, No. 5, pp. 1195-1211, September 2005.
 N. Celandroni, F. Davoli, E. Ferro, A. Gotta, “Adaptive Bandwidth Partitioning Among TCP Elephant Connections Over Multiple Rain-Faded Satellite Channels”, in Proc. of the 3rd Internat. Workshop on QoS in Multiservice IP Networks, Catania, Italy, Feb. 2005; in Lecture Notes in Computer Science, 3375, Springer-Verlag, Berlin, pp. 559-573, 2005.
 N. Celandroni, F. Davoli, E. Ferro, A. Gotta, “Long-Lived TCP Connections via Satellite: Cross-Layer Bandwidth Allocation, Pricing and Adaptive Control”, IEEE/ACM Transactions on Networking, Vol. 14, No. 5, pp. 1019-1030, October 2006.
 N. Celandroni, F. Davoli, E. Ferro, A. Gotta, “An Overview of Some Techniques for Cross-Layer Bandwidth Management in Multi-Service Satellite IP Networks”, in Proc. of Workshop on “Advances in Satellite Communications: New Services and Systems”, IEEE GLOBECOM ’05, St. Louis, MO, pp. WO4:4.1-WO4:4.6, November/December 2005.