Research And Improvement Of TCP Protocol In Satellite

With the rapid development of network technology, people can through the Internet convenient access to a variety of services. In people’s demand for various services rising exponentially,the ground of Internet bandwidth bottleneck problem has to be solved. But the satellite communication network with wide coverage, high transmission speed advantage, so the satellite-based Internet will become the research focus in communication field. Due to the characteristics of satellite channel is different from the ground channel, such as long delay, high bit error rate, which is suitable for the ground network TCP protocol can not be very good for the satellite network service, so we must according to the characteristics of satellite channel make improvement on TCP protocol.This paper first introduces the basic concepts of congestion control and traditional TCP congestion control algorithm, analyzes the improvement scheme for TCP performance in satellite networks existing. Firstly, according to the satellite network congestion control scheme of the overall analysis, discusses the improvement scheme, based on end to end link layer design scheme and split link schemes, and proposed the research focuses. The end to end on the basis of the improved protocol, are studied and improved, mainly in two aspects:on the one hand, according to the study of TCP-Peach+algorithm in high BER environments zero metadata section loss serious, resulting in the rapid recovery phase so that the congestion window is very difficult to restore to the original state, the congestion window reduced gradually and the in the data transmission rate continued to reduce the problems, propose an improved mechanism of rapid recovery, to inhibit the deterioration of the congestion window reduced gradually and the performance of TCP-Peach+. On the other hand, in view of the TCP-Peach+algorithm in congestion avoidance phase is still the traditional will slow start threshold set to the cwnd/2mechanism, which is a waste of bandwidth resources of existing problems, a new TCP-nPeach algorithm based on bandwidth estimation algorithm was proposed, which was confirmed by the observation signal arrival of accurate estimation of bandwidth, after receiving3duplicate ACK according to the estimated bandwidth congestion window and slow start threshold.This paper finally build a satellite channel simulation model using network simulation tool NS2, TCP-Peach, TCP-Peach+and the improved scheme for performance simulation. Results show that, the new algorithm has a very good improvement in terms of throughput and fairness.