Optimizing Random Unitary Beamforming for Energy Efficiency in MIMO Broadcast Channels

Abstract

Random unitary beamforming (RUB) achieves multiuser diversity gain over multiple-input multiple-output (MIMO) broadcast channels with channel state information (CSI). In this paper, we optimize RUB schemes in terms of energy efficiency (EE) which is defined as "capacity/power consumption". The key idea of our approach is to derive EE-optimal number of antennas and transmit power based on mathematical analysis. Using simple approximation expression, we derive efficient approach to find global optimum. Simulation results demonstrate that analytical results are accurate.