Lifetime maximization by cooperative sensor and relay deployment in wireless sensor networks

In this paper, cooperative sensor protocol and relay deployment in wireless sensor networks (WSNs) is proposed to improve the network lifetime. First, cooperative transmission is employed among sensor nodes. With an objective of maximizing the network lifetime under a constraint on bit-error-rate performance, we determine which sensors should cooperate and how much power to allocate for cooperation. A closed form solution is provided for a two-sensor WSN. Based on the obtained two-sensor solution, a fast suboptimal algorithm is developed for multiple sensor case. Moreover, the network lifetime is further improved by deploying cooperative relays in the network to help sensors transmit their information. The network lifetime is maximized by choosing the optimum location for each relay and optimally allocating the power that the relay helps each sensor. A suboptimal algorithm is proposed for the WSN with multiple relays. Simulation results show that the network lifetime of the proposed WSN with cooperative sensor employment improves 2.3 times compared with the non-cooperative WSN. In addition, deploying a cooperative relay in the proper location improves network lifetime up to 3 times of that for the non-cooperative WSN.