On Hierarchical Cooperation Formation in Mobile Infostation Networks

Mobile infostation networks which achieve content distribution by exploiting the opportunistic contact among mobile users (MUs) and access points (APs) have attracted a lot of attention in the last few years. It is found that cooperation either between APs or MUs has a great impact on the network performance. However, in most of the existing works wherever cooperation is involved, cooperation among the APs or MUs is discussed independently, while few of them has jointly taken both levels of cooperation into account. In this paper, we propose a more general framework which allows two levels of cooperation. The benefit as well as the cost of such hierarchical cooperation are taken into consideration. With properly defined payoffs of both APs and MUs, each AP may gain more benefit by strategically forming coalition with other APs, while the MUs can also choose to cooperate with one another to further maximize their payoffs. To obtain the optimal structure of two-level cooperation, an implementable distributed algorithm is proposed. Through extensive numerical experiments, our scheme shows the high effectiveness in achieving the stable cooperation structure, and the impact of different system parameters is also extensively investigated.