An Optimal Energy-Efficient Transmission Design for SWIPT Systems in WSNs

In power limited wireless sensor networks (WSNs), receiving, storing then utilizing energy from radio frequency (RF) signal has been a valid solution to prolong the lifetime. In this paper, we analyze the technique of Simultaneous Wireless Information and Power Transfer (SWIPT) in clustered WSNs, where some nodes are selected as the relay, collecting energy from the signal to help transmit information from the source to the destination. We design an energy-efficient transmission (e-Trans) so that the system can take a full utilization of energy to transmit data. And we aim to achieve the maximal system energy efficiency by jointly optimizing the source transmitting power, relay selection scheme and relay power splitting ratio. We first formulate the e-Trans design problem as a constrained optimization problem. Then, by transforming the fractional objective function into an equation, we propose a novel algorithm to solve the problem and achieve the optimal system energy efficiency. Simulation results illustrate performance of the proposed transmission design.