A reputation based scheme for stimulating cooperation in MANETs

A Mobile Ad hoc NETwork (MANET) is formed among a set of wireless nodes without infrastructure support, where network services such as routing axe provided by the nodes themselves. In such a scenario, if the wireless devices refuse to provide network services (and thus not cooperate), they cannot be forced to do so because of the lack of a controlling authority. Non cooperation leads to a significant reduction in throughput and the network utilization reduces to below optimum value. In this work, we provide a decentralized reputation based scheme for stimulating cooperation among nodes. Every node is assigned a reputation, calculated by all neighbors of the node, and the reputation is high if the node cooperates and low if the node refuses to cooperate. By providing better services (as an incentive) for nodes with high reputation and no service (as punishment) for those with low reputation, a node can be forced to cooperate, to obtain better services and to avoid punishment. We provide security against tampering of reputation and a mechanism to identify nodes that move to a new neighborhood to avoid punishment. The scheme is also resilient to malicious nodes that try to generate false reputation values for its neighbors and is robust in the presence of mobility. The scheme has been simulated using GloMoSim and the results indicate that in the presence of non cooperative nodes, a significantly higher throughput can be obtained when using our reputation scheme.