Energy efficiency and fairness in cooperative wireless ad hoc networks

In wireless ad hoc networks, nodes communicate with far off destinations using intermediate nodes as relays. Since nodes are energy constrained, it may not be in the best interest of a node to always accept relay requests. However, if all nodes decide not to expend energy in relaying, then network throughput will drop dramatically. Both these extreme scenarios (complete cooperation and complete non-cooperation) are inimical to the interests of a user. In this paper, we address the issue of user cooperation in ad hoc networks. We assume that nodes are rational, i.e. their actions are strictly determined by self-interest, and that each node is associated with a minimum lifetime constraint. Then, we are able to determine the optimal throughput that each node should receive, and we define this to be the rational Pareto optimal operating point. We propose a distributed and scalable acceptance algorithm, which is used by the nodes to decide whether to accept or reject a relay request. The algorithm results in a Nash equilibrium, and we prove that the system converges to the rational and optimal operating point.