CFDP协议触发NAK型文件传输时延的研究

Expected File Delivery Time of Prompt NAK Mode in CCSDS File Delivery Protocol

为适应深空通信环境,研究了CCSDS提出的CFDP文件传输协议,在协议条件下对其触发NAK型传输模式提出了一种适合远距离低传输率的延时触发方法。在地-月、地-火空间通信条件下,对延时触发NAK型传输模式进行了数学建模分析,在保证通信效率的前提下对NAK触发策略和ARQ计时器进行最优化设置,推导出该延时触发NAK型在理论上的最小传输时延期望表达式。与即时NAK和延时NAK传输方式比较,延时触发NAK型具有更小的文件传输时延,具备更优的文件传输性能,提高了系统的有效性。

To support the file transferring in deep space communication environment, the Consultative Committee for Space Data Systems （CCSDS） File Delivery Protocol （CFDP） was developed. The prompt negative acknowledgment （NAK） mode was analyzed, and a deferred-prompt trigger method and automatic repeat-request （ARQ） timer setting rule for the single-hop point-topoint file transfer operation was proposed, which minimized the expected time taken to transfer a file under the constraint of the maximized throughput. Performance measures was mainly concerned for the expected file delivery time and compared with the other NAK modes, the simulation results show that deferred-prompt NAK mode has a better performance in conditions.