Energy-Efficient Two-Way Relaying Under Non-ideal Power Amplifiers

Abstract

Energy efficiency (EE) is crucial to many battery-powered relay applications. Maximizing EE is challenging due to non-convex structures resulting from non-ideal power amplifiers (PAs) and non-negligible circuit power. We formulate such non-convex problems to maximize the EE of two-way relay systems, where the transmit power and duration of all participating nodes are jointly optimized. The intrinsic connection between the optimal transmit power and duration is established through our derived necessary conditions of the optimality. It enables us to reformulate the non-convex problems to problems with rigorously proved convexity in the vicinities of the optimal transmit duration and to solve the problems using simple convex search. Simulation results show that the EE gain of our approach is substantial, compared with the state of the art, when the traffic demand is low or unbalanced in the two link directions. The gain enlarges as the imbalance of traffic demand grows.