深空通信中基于中继选择的文件传输协议

针对深空通信传播时延大、误码率高以及链路间歇性中断的问题，提出一种基于中继选择的深空文件传输协议。该协议将文件传输过程分为跳到跳发送和端到端重传2个阶段。在发送阶段，提出一种中继选择算法，通过分析天体运动规律选择合适的中继节点，并结合深空链路信道特点，分析链路丢包率和信道增益的关系，选择最优中继链路逐跳进行传输，降低丢包率进而减少重传次数；在重传阶段，目的端对数据包进行校验和检查，丢失的数据包通过端到端链路进行重传，保证文件的可靠传输。仿真结果表明，当端到端误码率大于10－5时，所提协议能有效减少重传次数，进而降低传输时延。在误码率为10－3时，与空间数据系统咨询委员会（consultative committee for space data systems，CCSDS）提出的文件传输协议（CCSDS file delivery protocol，CFDP）相比，该协议的传输时间缩短了40％，能较好地适应深空通信环境。

File delivery protocol based on relay selection for deep space communication

In view of the problem of long delay,large BER and intermittent interruption in deep space communication,a deep space file delivery protocol based on relay selection is proposed.The presented protocol divides the file delivery into two stages:hop-by-hop transmission and end-to-end retransmission.In transmission stage,a relay selection algorithm is put forward,which selects the appropriate relay nodes based on the law of celestial motion,and builds the optimal path according to the relation between loss rate and channel characteristics to decrease packet dropout and the retransmission times.In retransmission stage,the receiver checks the received packets and requires the source to retransmit the lost ones through end-to-end link,which can guarantee the reliability of data delivery.Simulation results indicate that when the end-to-end BER is greater than 10-5,the proposed file delivery protocol can effectively decrease retransmission times and lower trans mission delay.When BER is 10-3,compared with CFDP,the transmission delay can be reduced by 40% indicating that the proposed file delivery protocol can well adapt to deep space communication environment.