A Low Complexity Energy Efficiency Maximization Method for Multiuser Amplify-and-Forward MIMO Relay Systems With a Holistic Power Model

In this letter, we investigate the energy efficiency (EE) maximization problem in multiuser amplify-and-forward (AF) MIMO relay systems with a holistic power model. A low complexity EE maximization method is proposed to jointly select the active antennas and the user, as well as optimize the transmission power of the user and relay. More specifically, the active antennas at the relay are selected by a norm-based scheme. We also propose a low complexity iteration scheme based on fractional programming, which can efficiently solve the pseudo-concave problem, in order to select the user and optimize the transmission power. Simulation results show that the proposed low complexity method enjoys a probability of 99% to hit the optimal EE obtained by exhaustive search. Moreover, it has an average gain of 42% in the EE over the conventional AF MIMO relay protocol.