Cross-layer improvement for TCP Westwood and VoIP over satellite

Satellite communications can play an important role in extending the reach of broadband networks to terrestrially underserved areas. However, several popular internet applications could suffer from performance degradation over satellite (e.g. realtime gamming, web browsing, VoIP), thus necessitating protocol modifications and additional optimisation mechanisms. Cross-layer design, which is the optimisation technique adopted in this paper, is a relatively new idea in network design. It is based on blurred boundaries between network layers. In particular, two cross-layer mechanisms are described; the first adapts the VoIP speech coding rate according to network congestion while the second uses TCP state information at MAC layer in order to improve the throughput of TCP traffic. Analysis in this paper demonstrates that the use of cross-layer techniques could improve the performance of the targeted applications in terms of reduced delay while continuously maintaining an optimal speech coding rate for VoIP.