GAR: Group aware cooperative routing protocol for resource-constraint opportunistic networks.

Opportunistic networks are a new evolution of mobile ad hoc networks composed of intermittently connected nodes, in which the routing based on the dynamic topology is a challenging issue. In opportunistic networks, the mobile nodes with common interest or close relationship may form into groups and move together, which brings us a good feature to employ when designing the routing protocol for the resource-constraint opportunistic networks. Our main idea in this paper is to maximize the message delivery probability with the consideration of the group feature in the opportunistic network under the constraints of bandwidth and buffer space. Embedded this idea, we propose a cooperative routing protocol called GAR, which includes a cooperative message transfer scheme and a buffer management strategy. In the cooperative message transfer scheme, the limited bandwidth is considered and the message transfer priorities are designed to maximize the improved delivery probability. In the buffer management strategy, by considering the constraint of buffer space, we propose a cooperative message caching scheme and the dropping order of the messages is designed to minimize the reduced delivery probability. We also propose an improved strategy to utilize the extra contact duration between each pair of encountering nodes to further improve the performance. Finally, we conduct the simulations to demonstrate the effectiveness of our proposed GAR protocol under different network parameters.