Research Of Satellite Communication Network's Transport Layer Protocol

The development of the Internet makes the world together, the future of human development will be forward to space, the next generation of Internet, satellite network will be an important part of the network. However, due to the high bit error rate, high link delay, and frequent link state changes, the satellite network itself can not be characterized by ground network. The assumption that the protocol implementation of the Internet in the ground is not applicable to the network characteristics. In this paper, we analyze the characteristics of satellite networks and the reasons why the TCP protocol can not adapt to the satellite network. And the improved method is presented and the Space communications protocol speificationtransport protocol(SCPS-TP) protocol is implemented on the demonstration platform to verify the efficiency of SCPS-TP.Firstly, the premise of the TCP running on the ground network is described, and the link characteristics of satellite networks are analyzed. The draw a conclusion that TCP does not adapt to the link characteristics of the satellite network.Aiming at the characteristics of satellite networks, CCSDS proposed a protocol based on TCP protocol named SCPS-TP. Aiming at the link characteristics of long and round trip delay, this paper uses the transmission window expansion mechanism and the increment of timeout retransmission time mechanism to realize amelioration. Aiming at the link characteristics of high link error rate, this paper uses the packet header compression mechanism and select negative acknowledgement mechanism to realize improvment. In the Vegas algorithm, this paper improve the dynamic estimation throughput in the outage tolerance network. The proposed method is based on the ratio of the transmission window and the reference to the round-trip delay. According to the measured network throughput and the estimated throughput, this method can effectively adjust the congestion window size. This method can make the network throughput and forecast the network throughput in an order of magnitude, and can make congestion control algorithm, such as Vegas algorithm more accurate adjustment of congestion window, avoid the disadvantages caused by packet loss caused by link quality, reduce the link throughput, and thus better link throughput. Through many improved methods, the data transmission rate, packet loss rate, reducing the signaling overhead, and the transmission efficiency of the link are effectively improved.Finally, the SCPS-TP protocol is implemented on the Ubuntu operating system using the Qt development environment with an overall architecture and main modules in implementation scheme. Then, this paper design several satellite communication scene, and test a number of demonstration scripts, analysis and demonstration of all parameters, At the end of the paper.it demonstrates the authenticity of the design scheme and the adaptability of the satellite communication network.