This paper studies the cooperative routing algorithm for maximizing the network lifetime in sensor networks.The study assumes nodes in the network are able to perform cooperative transmission to achieve transmit diversity,and proposes a joint cooperative transmission and energy conserving routing algorithm to prolong the network lifetime.First,a lifetime maximization problem via cooperative nodes is considered and performance analysis for MPSK modulation is provided.With an objective to maximize the minimum device lifetime under a constraint on bit-error-rate performance,the optimization problem determines which nodes should cooperate and how much power should be allocated for cooperation.Since the formulated problem is NP hard,a distributed suboptimal algorithm is developed for multi-node scenarios.The study demonstrates through simulation that the proposed solution achieves more than twice the length of the network lifetime compared with non-cooperative routing,when it is used with FA algorithms.