The Research And Design On Multi-user CFDP

With the development of space communication network and the internationalization of space mission, the research on deep space gains more and more attention and importance. However, different from terrestrial network, many features like long propagation delay, high bit error rate, limited bandwidth, intermittent connectivity and asymmetric channel transmission rate cause a series of problems in space communication, such as limited time for existence of end-to-end path, high packet loss rate and long round-trip time, etc. To solve these problems, CCSDS(Consultative Committee for Space Data Systems) proposed CFDP(CCSDS File Delivery Protocol) to provide an efficient and reliable transmission standard for deep space communication.Firstly, a study is made in this paper on details of CFDP including the analysis of its protocol architectural, communication model and retransmission strategy. The comparison of CFDP with FTP(File Transfer Protocol) in terrestrial network and SCPS-FP(Space Communication Protocol Specification-File Protocol) in satellite network shows that CFDP is more adaptable for communication in bad deep space environment and appears to be more effective.Then, after the analysis of delay performance of CFDP, this paper designs the multi-user CFDP which is based on DNA(Deferred NAK ARQ) or INA(Immediate NAK ARQ) and proposes the realization plan. The multi-user CFDP focuses on the optimization of retransmission strategy and timer design scheme under the constraint to maximize the throughput.Finally, this paper shows the performance of the multi-user CFDP in Earth-Moon and Earth-Mars communication environment based on simulation. The simulation makes a comparison of influences on the file transmission delay under the same transmission mechanism of different factors, and the relationship of file transmission delay under the same condition of different transmission mechanism. In addition, the delay performance of multi-user CFDP based on DNA in different queueing systems is discussed and made a comparison. The results show that both DNA and INA have advantages in different conditions and preemptive priority queueing system performs better than nonpreemptive priority queueing system.