Cooperation in delay tolerant networks

In delay tolerant networks (DTNs), all the networking functions rely on the contribution of the participants to fulfill the store-and-forward fashion. Since wireless nodes are buffer and energy constrained, it may not be in the best interest of a node to always accept relay request. In recent years, incentive mechanisms have been proposed to stimulate nodes to cooperate in packet forwarding. However, the lack of end-to-end paths, high variation and long feedback delay in DTNs imply that existing solutions for mobile ad-hoc networks do not apply to DTNs. In this paper, we address the problem assuming that nodes are rational to optimize self interest. We propose a model, named Pay-for-Gain (PFG), based on game theory and loan-credit theory, to investigate equilibrium point that maximizes their own interest. For comparison, the strategy tit-for-tat (TFT) and PFG are tested in existing routing protocols in DTNs.