DSFDP: Deep Space File Delivery Protocol Research

Deep space exploration embodies a country's comprehensive national strength and technology development level. It is of significant military, political and economic importance. In deep space exploration, the communication plays a key role. Differing from terrestrial and satellite communications, deep space communication has no real-time requirement. Command and data must be stored as files and concentrated to send, so file transmission is an important form of deep space communications.For deep space communications, there are some existing communication protocols. In this thesis, we introduce these protocols'advantages and disadvantages respectively, and lay stress on the Consultative Committee for Space Data System (CCSDS) File Delivery Protocol (CFDP) that CCSDS developed for space communications. We analyze the structure and characteristics of CFDP. With cross-layer optimization, CFDP can meet the requirements of deep space communications, but its error control method, NAK, is yet within the confinement of ARQ. When the channel fade in deep space communications results in higher bit error rate (BER), CFDP needs more rounds to send the file. It will make the transmission time much longer.In recent years, fountain code has been in hot research and wide application. With rateless, semi-feedback characteristics, and simple encoding and decoding algorithm, fountain code is very suitable for deep space communications. The thesis proposed a Deep Space File Delivery Protocol (DSFDP), and gave its transmission performance simulation. The performance comparison between DSFDP and CFDP shows that, in geosynchronous orbit (GEO) communications, both bear the similar transmission performance. But with the increase of delay and BER, DSFDP's performance will be significantly better than that of the CFDP. In the case that the one-way propagation delay is 1.35s (Earth-to-Moon Communications), BER is 10-4 (deep fading), DSFDP's transmission time reduces 50% or more than that of CFDP. In the case that the one-way propagation delay is 240s (the shortest delay of Earth-to-Mars communications), BER is 10-5, DSFDP's transmission time is 40% less than that of CFDP, and if BER is 10-4, DSFDP's transmission time reduces 88% than that of CFDP. Therefore, DSFDP can adapt to a long range of BER and delay variation, especially be suitable for deep space communication where the communication environment deteriorates to the limit condition...