Smoothing selfishness by isolating non cooperative nodes in ad hoc wireless networks

Current ad hoc networks rely on a silent mutual agreement among nodes to relay packets to the destinations. The efforts made by each single node to serve the others are usually repaid with the chance to successfully set up its own traffic sessions. However, limited power, together with security concerns, can push certain nodes to refuse to cooperate. Such nodes will thus act as parasites, while the others will unawarely keep on trusting them for what concerns the agreement on mutual service. In this paper we present an algorithm inspired by the results of game theory, specifically designed to let the nodes of an ad hoc network become able to trace the behavior of the companion nodes. Traffic is forwarded only towards cooperative nodes, hence reducing the waste of power at the same time maximizing the delivery rate. In such a scenario, selfish nodes will be isolated as long as they refuse to cooperate. The algorithm is included in an existing ad hoc routing protocol and is shown to successfully stimulate cooperation among nodes in a simulated environment.