Mitigating the effect of mobility on cooperation in wireless ad hoc networks

In wireless ad hoc networks, nodes may act selfishly to preserve their limited energy resources. This behavior can cause the network performance to drop. Therefore, cooperation between peers is necessary to keep ad hoc networks operational. Beside the need to actively encourage cooperation, passive encouragement is also needed to overcome the effect of factors that may limit cooperation. These factors include malicious behavior, environmental obstruction that may cause communication distortion, and mobility. In particular, recent studies on real networks have shown a detrimental effect of mobility on network topology that may hinder cooperation in ad hoc networks. Coalitional game theory has been used in the literature to model cooperation in ad hoc networks, yet the effect of mobility has not been studied thoroughly. In this paper, we propose a coalition game model for cooperation in mobile ad hoc networks (MANETs) that shows that the effect of topology changes caused by mobility on the coalitional structure can be mitigated while maintaining coalitional stability. We use the notion of reachability to evaluate the proposed model. We simulate the model under different speeds and node densities. Our simulations show that reachability can be sustained at stable levels despite the deterioration caused by mobility.