Proactive Retransmission in Delay-/Disruption-Tolerant Networking for Reliable Deep-Space Vehicle Communications

Delay-/disruption-tolerant networking is recognized by the National Aeronautics and Space Administration as the only candidate network communication technology that approaches the level of maturity required for deep-space vehicle communications. Extensive performance evaluation and development of efficient data transmission mechanisms for its main protocol, bundle protocol (BP), are needed. In this paper, a new transmission approach based on "proactive" retransmission is proposed for BP for highly efficient data delivery in deep-space communications characterized by a high rate of data loss, long signal propagation delay, and highly asymmetric channel rate, given ample transmission bandwidth. The objective is to ensure successful and reliable deep-space file transfer within a single communication round-trip interval. The expected total number of transmission attempts needed for successful delivery of a file is first calculated based on the available space channel quality and the configured bundle size. Then, the time-out interval for custodial retransmission is set according to the expected number of transmission attempts required, such that all these attempts will be undertaken within the interval of a single round-trip. The performance evaluations based on both theoretical modeling and file transfer experiments indicate that the proposed proactive retransmission approach achieves the objective and has significant performance advantages over the existing reactive retransmission regardless of the transmission conditions.