Low complexity antenna grouping for energy efficiency maximization in massive MIMO systems

In this paper, we investigate antenna grouping for energy efficiency maximization in the downlink of multiuser massive MIMO systems. We construct an antenna grouping system model which partitions large-scale transmit antenna array into fixed-size groups. Beamforming is used within each group and spatial multiplexing between groups is considered. Diversity gain is then achieved by beamforming, and multiplexing gain by spatial multiplexing. System capacity and power consumption are analyzed, based on which the impact of the number of active transmit antennas per group is studied. A low complexity algorithm for finding the optimal number of active transmit antennas in each group is proposed based on binary search. Simulation results show that the proposed scheme significantly improves the energy efficiency of the system, and there exists optimal value of the number of the active transmit antennas per group in the fixed-size grouping model that maximized the energy efficiency.