tailieunhanh - Resource Management in Satellite Networks part 32

Resource Management in Satellite Networks part 32. This book provides significant knowledge on innovative radio resource management schemes for satellite communication systems that exploit lower layer adaptivity and the knowledge of layer 3 IP QoS support and transport layer behavior. The book integrates competencies considering all the parts of system design: propagation aspects, radio resource management, access protocols, network protocols, transport layer protocols, and more, to cover both broadband and mobile satellite systems | 298 Gorry Fairhurst Michele Luglio Cesare Roseti The above discussion leads to the conclusion that satellite systems could benefit from adaptive algorithms for choosing the transmission parameters by means of cross-layer interactions between transport and physical layers. An additional possibility is that MAC and physical layers interact by inserting a link-layer erasure code 20 27 just above MAC layer which could be an all-software solution independent of the underlying hardware characteristics. The recent DVB-S2 standard 28 considers very powerful error-correcting codes. For ideal AWGN channel conditions an optimization based on channel coding would be useless because the curves that give PER versus Eb N0 are very steep 29 causing a sort of on-off behavior of the physical channel either PER is negligible or it is so high that it collapses TCP performance. However optimizing channel parameters makes sense in non-ideal channel conditions and in general on the satellite return channel 3 . Cross-layer interaction between TCP and MAC The interaction between TCP and MAC protocols in a shared network can greatly improve the efficiency of satellite systems. MAC protocols play a fundamental role to guarantee good performance to higher-level protocols by managing the arbitration of uplink access. Two cases must be distinguished i when TCP operates end-to-end as the general Internet standard or when an end-to-end IPsec protection scheme is used ii a PEP scheme violates the end-to-end semantics. Without loss of generality hereafter we will consider the latter case where referring to a DVB-RCS network see Chapter 1 Section the Gateway acts as a PEP . it is a local TCP receiver -from remote RCSTs- located in the Earth station . Satellite networks employing a DAMA scheme introduce an additional contribution to the end-to-end delay called the access delay that can significantly impact the end-to-end performance of TCP flows. In a DVB-RCS-like network the Network .