A number of novel physical layer techniques, and in particular adaptive coding and modulation (ACM) combined with high order modulations, have shown the potential to significantly improve throughput of current return link (RL) broadband access satellite systems. However, their introduction shall be complemented by novel concepts at MAC and network layer, which aim at increasing flexibility and maximizing actual achieved system efficiency, In this paper a novel frame and burst format is proposed, capable of ensuring high overall efficiency combined with radio resource management (RRM) simplicity. A comprehensive cross-layer optimization is carried out through simulation and numerical assessment in order to optimize burst lengths taking into account physical layer performances and network traffic profiles. Moreover, a novel encapsulation protocol (generic stream encapsulation-GSE) is considered to further improve IP transport efficiency.

A new soft decision criterion is derived. This is useful in communication systems where the combination of modulation, interleaving, and error correction is used. The new algorithm is attractive to implement since traceback techniques can be used and only a little extra memory is required to obtain the soft information associated with every symbol. Furthermore, the operations involved are not recursive and the execution is time independent of the received signal quality. The performance of the new algorithm is typically within 0.25-0.1 dB (bit error rate (BER)=10/sup -1/) of that of a significantly more complex algorithm reported previously.