Satellite communication plays a more and more significant role in both military and civil affairs. Improving the performace of transport protocol in satellite communication is a hot topic both at home and abroad currently. Although traditional TCP protocol prviodes reliable end-to-end data transmission in wired network communication, it fails to acquire equivalent high performance due to the characteristics of satellite radio link such as long delay, high bit error rate (BER), etc. Aimming at enhancing the throughput and bandwidth utilization of data transmission in satellite link, an improvement of the existing transmis-sion control protocol is necessary.The dissertation gives a detailed analysis of TCP specification and its disadvantages in satellite communicaton firstly. Then some enhanced transport protocols suitable for satel-lite communication are introduced. Bandwidth estimation algorithm can improve the transmission performance of satellite communicaton and alleviate the problem incurred from high BER. It sets the sizes of congestion window and slow start threshold according to estimated bandwidth, avoiding shrinking them blindly on the occurrence of packet loss. Based on the fact that traditional bandwidth estimation algorithm, which is affected by factors like data burst, delayed ACK, ACK compression, etc. is inclined to overestimate the available bandwidth, this thesis puts forward an algorithm called Bandwidth Estima-tion based Transmission Control Protocol(BE-TCP). BE-TCP estimates the available bandwidth more accurately and utilizes a novel method to update the value of ssthresh.Theoretical analysis and NS2 simulation of BE-TCP are carried out and both results indicate that BE-TCP achieves a more accurate bandwidth estimation and an improved performance of TCP in satellite communication.
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