Hybrid MMSE precoding for mmWave multiuser MIMO systems

Millimeter-wave (mmWave) communication has emerged as one of the most promising technologies to deal with the increasing demand in data transmissions over wireless networks. However, due to the propagation characteristic at the mmWave band, much higher pathloss is observed compared to the commonly-used microwave band. Thus, antenna arrays become a necessary ingredient in mmWave systems because of their needed beamforming gains. Beamforming for multiple users, also known as multiuser precoding, can be utilized to further improve the spectral efficiency of mmWave systems. Unfortunately, fully digital precoding with large antenna arrays is difficult to implement due to the hardware cost and power constraint in mmWave systems. Recent works in literature have advocated the structure of hybrid analog/digital precoding for mmWave systems, in which only minor performance degradation is observed. In this work, we study hybrid precoding for multiuser mmWave systems. After reviewing recent works in literature on hybrid precoding designs, we then develop a new hybrid minimum mean-squared error (MMSE) precoder. The proposed precoder can be easily obtained by an orthogonal matching pursuit-based algorithm. Simulation results show significant performance advantages of the proposed precoder over known designs in various system settings.