Practical Hybrid Precoding for Multi-user Massive MIMO Systems

Massive MIMO systems bring manifold improvements in the system spectral efficiency but result in high hardware and processing complexity at the base station. Employing hybrid precoding at the base station can reduce such complexity. This paper proposes two hybrid precoding schemes for a multi-user massive MIMO system. The proposed schemes, namely sequential-EGT and best-user EGT schemes, use equal gain transmission (EGT) based analog beamforming to reap the diversity benefit of an analog phased-array and employ zero-forcing beamforming for nullifying inter-user interference. As illustrated by the simulation results presented in this paper, the best-user EGT scheme outperforms sequential-EGT scheme in all scenarios with slightly higher computational complexity. We also investigate the optimal number of scheduled users for each scheme.