Evaluating the effects of node cooperation on DTN routing

Due to the uncertainty of transmission opportunities between mobile nodes, delay tolerant networks (DTN) routing exploits the opportunistic forwarding mechanism. This mechanism requires nodes to forward messages in a cooperative way. However, in the real word, most of the nodes exhibit non-cooperation behaviors such as dropping and not relaying messages. In this letter, we investigate the problem of how the non-cooperation behaviors of nodes influence the performance of DTN routing algorithms of two-hop relay and epidemic routing. First, we model the message delivery process with non-cooperation behaviors by a two dimensional continuous time Markov chain. Then, we obtain the system performance of message delivery delay and delivery cost by explicit expressions. Numerical results show that different non-cooperation behaviors may have opposite impacts on different routing algorithms. Specifically, dropping message increases the message delivery delay and delivery cost in the two-hop relay, while increases the delay but does not affect the delivery cost in the epidemic routing, and not relaying message increases the delivery delay but decreases the delivery cost for both the two-hop and epidemic routing.