Stimulating Cooperation in Mobile Ad Hoc Networks

Consider a mobile ad hoc network (MANET) where packet transmissions occur between mobile nodes. Such a network requires that the nodes act as relays to form multi-hop routes connecting the origin-destination node pairs that are out of radio transmission range with respect to each other. If the nodes do not to belong the same authority, then the nodes must be given an incentive to spend their resources (battery power and transmission bandwidth) in forwarding packets that originate at other nodes. This can be done by introducing a credit balance for each node, where the nodes use credits to pay for the costs of sending their own traffic, and earn credits by forwarding traffic from other nodes. This paper presents several variants of a credit-based incentive scheme (protocol) to promote collaboration in MANETs. The variants address the fairness of the scheme, namely (1) to assist those nodes that are under-provided with credits: such nodes may lack the credits necessary to transmit their data, and (2) to protect those nodes that are over-provided with credits: such nodes may, to their own detriment, provide too large a proportion of their resources to the community. We first present two basic incentive schemes: the first scheme does not regulate the willingness of the nodes to forward packets on behalf of other nodes; the second scheme contains such a regulatory mechanism. We next focus on protocols whose design lies between the two basic schemes. Both the origin pays and the receiver pays protocols are investigated. Both constant and congestion-related resource prices are investigated. Initial simulation experiments indicate that both the origin pays and the receiver pays protocol with a credit distribution and discounting (redistribution) mechanism is sufficient to afford a reasonably fair allocation of flows in the network.