Research On Reliable Transmission Protocol And Realization Of Verification Platform Based On Space Integrated Ground Network

With the research and deployment of space satellite networks moving forward rapidly,the Space Integrated Ground Network(SIGN),combining the advantages of mature ground network and space satellite network,has broad application prospect.Among them,the Transmission Control Protocol(TCP)used to guarantee the reliability of end-to-end data transmission would play an important role in various application scenarios in SIGN.However,due to the typical characteristics of space satellite network such as long delay,high bit error rate,high dynamic topology and the asymmetric of the uplink and downlink bandwidths,the reliable transmission protocol in ground network(TCP)faces serious challenges when applying to space satellite network.In view of the problem,this paper's works are mainly as follows:Firstly,this paper investigates and summarizes the main improvement schemes about TCP in space satellite network.Based on the orderliness,correctness,reliability,and high efficiency of the TCP protocol data transmission,the main mechanisms in the TCP protocol are studied.Besides,combined with the main characteristics in SIGN,this paper makes further analysis on the major causes why TCP performs poorly when applying TCP to SIGN directly,tests and verifies it in the Reliable Transmission Protocol simulation platform designed in this paper.Secondly,this paper introduces the basic working principle of the TCP Performance Enhancing Proxy(PEP),which is one of the typical improvement schemes for reliable transmission protocol based on TCP segmented methods.From the perspective of average end-to-end throughput and packet delivery rate,this paper compares and analyzes traditional end-to-end reliable transmission method and segmented reliable transmission method based on PEP.Moreover,as PEP cannot guarantee the continuity of data transmission in mobile environment,this paper proposes a segmented reliable transmission method based on mobile reliable transmission proxy which will deploy the mobile reliable transmission proxy on low orbit Satellite or near space platform.By designing the information interaction mechanism between mobile reliable transmission proxies,the problem of handover between mobile reliable transmission proxies may be solved.Compared with PEP,this method not only guarantees the continuity of the end-to-end transmission process in the handover process of the mobile reliable transmission proxy,but also further improves the average end-to-end throughput of TCP.Finally,this paper designs and implements a verification platform for the reliable transmission protocol of the Space Integrated Ground Network.Based on the Linux operating system,this paper designs a converged gateway for the space satellite network and ground network that supports three configuration modes including routing forwarding mode,PEP mode based on TCP and PEP mode based on SCPS-TP.Through the space link simulator,link characteristics such as delay,packet loss rate,and asymmetric link bandwidth can be simulated to construct different application scenarios of the Space Integrated Ground Network.Then,this paper tests the performance of TCP in aforementioned three modes for different scenarios,which provides platform support for further research on the reliable transmission protocol and provides theoretical guidance and suggestions for constructing real Space Integrated Ground Network.