Efficient Network Coded Data Transmissions in Disruption Tolerant Networks

Most routing protocols in disruption tolerant networks (DTN) use redundant transmissions to explore the diversities in routing paths in order to reduce data transmission delay. However, mobile nodes in DTN usually have limited energy and may prefer fewer transmissions for longer lifetime. Hence, it is vital to carefully balance the tradeoff between data transmission delay and the amount of transmissions among mobile nodes. In this paper, we consider the problem to route a batch of data packets in DTN. By making an analogy between the routing protocol and low-density erasure codes, we investigate the information-theoretical optimal number of data transmissions in delivering data. With such insights, we propose E-NCP, an efficient protocol in DTNs based on network coding, that reduces data transmissions significantly, while increasing data transmission delay only slightly as compared to the protocol with the best performance. With extensive theoretical analysis and simulations, we show that network coding facilitates a better tradeoff between resource usage and protocol performance, and that our protocol offers unique advantages over replication-based protocols.