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Cooperation enforcement in ad hoc networks with penalty

To facilitate the multi-hop communications in mobile ad hoc networks, all the nodes in the networks need to cooperate and relay packets for other nodes. Unfortunately, there exist selfish nodes that may refuse to relay packets for others in order to save their own resources such as energy. Those non-cooperative behaviors will lower down the network performance significantly. Therefore, schemes need to be developed to enforce the cooperation of selfish nodes in the multi-hop communications. Credit-based algorithms have been proposed and are considered simple and effective. However, those schemes can lead to unbalanced credit distribution. That is, some nodes in hot areas can easily gain many credits so that they stop relaying for others, while some nodes in cold areas may gain few credits so that they are excluded from the network even if they are willing to cooperate. This paper aims to provide a solution to encourage the nodes in hot areas to stay in the network and help others relay the traffic. We impose a penalty for those non-cooperative nodes in order to force them to participate the communications. To further provide incentive for cooperative nodes to remain cooperative, we propose a game played by the nodes in the same layer. The imposed penalty depends on the outcome of the game. When a node chooses cooperation, the payoff it perceives is the reward from relay minus the cost resulting from the energy loss. When a node chooses not to cooperate, the payoff is the penalty. A node will select the option that generates larger payoff. Simulation results show that our scheme can enforce the nodes in hot areas to cooperate and also encourage cooperative nodes to remain cooperative