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We consider the problem of cooperative packet delivery to mobile nodes in a hybrid wireless mobile network, where both infrastructure-based and infrastructure-less (i.e., ad hoc mode or peer-to-peer mode) communications are used. We propose a solution based on a coalition formation among mobile nodes to cooperatively deliver packets among these mobile nodes in the same coalition. A coalitional game is developed to analyze the behavior of the rational mobile nodes for cooperative packet delivery. A group of mobile nodes makes a decision to join or to leave a coalition based on their individual payoffs. The individual payoff of each mobile node is a function of the average delivery delay for packets transmitted to the mobile node from a base station and the cost incurred by this mobile node for relaying packets to other mobile nodes. To find the payoff of each mobile node, a Markov chain model is formulated and the expected cost and packet delivery delay are obtained when the mobile node is in a coalition. Since both the expected cost and packet delivery delay depend on the probability that each mobile node will help other mobile nodes in the same coalition to forward packets to the destination mobile node in the same coalition, a bargaining game is used to find the optimal helping probabilities. After the payoff of each mobile node is obtained, we find the solutions of the coalitional game which are the stable coalitions. A distributed algorithm is presented to obtain the stable coalitions and a Markov-chain-based analysis is used to evaluate the stable coalitional structures obtained from the distributed algorithm. Performance evaluation results show that when the stable coalitions are formed, the mobile nodes achieve a nonzero payoff (i.e., utility is higher than the cost). With a coalition formation, the mobile nodes achieve higher payoff than that when each mobile node acts alone.