An analysis of TCP over random access satellite links

This paper analyzes the performance of TCP over satellite links with random access. The system considered consists of large number of identical source-destination pairs, each employing TCP at its transport layer and a random access scheme at its MAC layer. Simple formulas that well capture the system performance are given, and some important properties of the system performance are presented as well. Specifically, in order to analyze the system, we propose a simplified version of the system. We then develop formulas for obtaining the throughput of this simplified system as a function of various system and protocol parameters. Based on these formulas, it is shown that the maximum possible system throughput is 1/e, which can he achieved only when the system parameters satisfy a given condition. The optimal MAC layer transmission probability at which the throughput is maximized is derived as well. Furthermore, the impact of varying system and protocol parameters on the system performance is analyzed. The results show that for systems with very small propagation delay or very large number of source-destination pairs, a throughput of 1/e can be achieved by setting the MAC layer transmission probability to its optimal value. However, when the number of users is (relatively) small or the propagation delay is (relatively) large, the maximum achievable throughput can be substantially smaller than 1/e. Although the analysis is based on the simplified system, simulations on the original system show that the formulas and the above results can be used to describe the performance of the original system as well.