Unreliable CCSDS File Delivery Protocol (CFDP) over Cislunar Communication Links

The Consultative Committee for Space Data Systems (CCSDS) file delivery protocol, also known as CFDP, is a new standard protocol designed to meet a comprehensive set of file transfer requirements in space communications, especially deep space missions. There has been theoretical and experimental evaluation on the performance of CFDP operation in low Earth orbit (LEO) and geo-stationary Earth orbit (GEO) space environments. However, very few works have evaluated the performance of CFDP in cislunar space, even though the protocol has been particularly developed for deep space communications. In this work we discuss an experimental investigation of the core file-delivery operation of unreliable CFDP, operating with reliable transmission control protocol (TCP), over a simulated cislunar communication link under various channel conditions. Our intention is to evaluate the transmission effectiveness of the core file-delivery operation in unreliable CFDP running on top of a reliable TCP/IP stack over a long-delayed cislunar link, especially when accompanied by link disruptions and a high bit error rate (BER). The performance of unreliable-CFDP/TCP is also compared with other protocol options of CFDP, such as reliable-CFDP/TCP and reliable-CFDP/UDP. The experiment was carried out through realistic file transfers by running the CFDP protocol stack over a communication test-bed incorporating the qualities that define cislunar communication channel characteristics. The research results and discussions presented in this paper should work equally well in any space mission with a round-trip time (RTT) that is comparable to that of the cislunar space.