Joint optimal relay selection and power allocation for cooperative transmission in wireless sensor networks

Energy efficiency is an important performance measure in wireless sensor networks as the life span of the network is closely related to the rate of energy consumption of sensors. Cooperative communication schemes are implemented to reduce the energy consumption of the network, using the notion of diversity in wireless transmission. This work presents a framework for optimal relay selection and power allocation under some signal-to-noise ratio constraints. The proposed approach determines whether direct transmission from the source node to destination node is more energy-efficient or cooperative transmission through different nodes. In the latter case, data transmission from each node to the destination node is performed in two consecutive phases: broadcasting and relaying. The proposed scheme selects the best set of relays for data transmission, the optimal broadcasting power and the optimal power values for the cooperative transmission phase.