Benefits of Network Coding in Disruption Tolerant Networks

In this paper, we investigate the benefits of applying a form of network coding known as Random Linear Coding (RLC) to unicast application in Disruption Tolerant Networks (DTNs). Under RLC, nodes store and forward random linear combinations of packets as they encounter each other. For the case of a single group of packets originating from the same source and destined for the same destination, we prove a lower bound on the probability that the RLC scheme achieves the minimum time to deliver the group of packets. Although RLC achieves a significant reduction in group delivery delay, it fares worse in terms of average packet delivery delay and network transmissions. When replication control is employed, RLC schemes reduce the group delivery delay without increasing the number of transmissions. In general, the benefit achieved by RLC is more significant under stringent resource (bandwidth and buffer) constraints, limited signaling, highly dynamic networks, and when it is applied to packets from same flow. For more practical settings with multiple continuous flows in the network, we show the importance of deploying RLC schemes with a carefully tuned replication control in order to achieve reduction in average delay.