Energy Efficiency Optimization and Comparison for One-Way and Two-Way Decode-and-Forward Relay Systems

Abstract—Energy-efficient communication techniques play great roles in applications where devices are powered by batteries. Relaying is viewed as an energy saving technique because it can reduce the transmit power by breaking one long range transmission into several short range transmissions. TwoWay Relaying Transmission (TWRT) is expected to consume less transmit power than One-Way Relaying Transmission (OWRT). In this paper, we study the Energy Efficiencies (EEs) of One-Way Decode-and-Forward (OWDF) and Two-Way Decode-and-Forward (TWDF) systems with delay constraint. The maximum EEs of both systems are derived by jointly optimizing the transmission duration and the transmit power allocation. Analytical and simulation results show the impacts of packet size, time deadline and the channel gain to EE.