Promoting cooperation in mobile ad hoc networks

Consider a mobile ad hoc network (MANET) where the nodes belong to different authorities. The nodes must be given incentives to spend their resources (battery energy, transmission bandwidth, buffer space) in forwarding packets that originate at nodes belonging to another authority. This can be done by assigning a credit balance to each node: when a node acts as an originating node it uses its credits to pay for the costs of sending its own traffic; when a node acts as a transit node it earns credits by forwarding traffic from other nodes. This paper presents a credit-based incentive scheme which assists nodes that persistently lack the credits necessary to transmit their data, and protects nodes from using too large a proportion of their resources to forward traffic that originated from other nodes. We first present the free-for-all scheme and next we present the origin pays protocol which contains a decentralised credit redistribution mechanism to destroy (create) credit at over (under) provisioned nodes. Both constant and congestion-dependent resource prices are investigated. Initial experiments indicate that the origin pays protocol with congestion pricing offers a substantial improvement over the free-for-all protocol that is currently used in MANETs.