An Effective Mechanism for Improving Performance of TCP over LEO/MEO Satellite IP Networks

TCP protocol is widely used in terrestrial Internet, but the terrestrial TCP protocol satellite cannot be directly applied to satellite network with high-transmission delay and high bit error rate. The congestion control is the most core mechanism of TCP protocol, and has direct impact on the overall performance of transmission. The improved scheme of existing TCP control mechanisms such as TCPVegas, TCP-Peach and TCP-westwood have improved congestion control mechanisms and error control mechanism of TCP from different angles in order to make it adapt to satellite link's characteristics like signal attenuation and high bit error rate. However, there exist some gaps between these strategies in the multimedia service transmission and user’s needs. Based on LEO / MEO network structure, aiming at the issues in transmission such as the slow growth of the congestion window, the low utilization of bandwidth and constrained throughout, this paper put forward an improved algorithm TCPQ (TCP QoS) of transmission on the basis of multi-indicators guarantee. TCPQ includes three parts: accelerated start algorithm, nonlinear congestion avoidance algorithm, and adaptive threshold error-identification algorithm. Analysis and simulation experiments show that TCPQ algorithm can make full use of link resource and have a better performance in terms of throughout, transmission efficiency, etc.