Sub-array based hybrid precoding design for downlink millimeter-wave multi-user massive MIMO systems

In this paper, we investigate the downlink of millimeter-wave multi-user massive MIMO systems, and propose a hybrid precoding scheme based on a sub-array architecture to achieve a better compromise between hardware cost and system performance. The proposed precoding scheme performs analog precoding and digital precoding at the transmitter with the generalized sub-array architecture. It implements analog precoding in the radio frequency domain and then performs a low dimensional digital precoding at baseband according to the effective channel matrix. We analyze the effect of the number of the overlapped antennas to the spectral efficiency, and investigate the number of users that the system can support by using different precoding schemes with the generalized sub-array architecture. The simulation results show that the proposed algorithm has lower complexity than that of the full-array precoding scheme, and can achieve superior performance than those of the other sub-array based hybrid precoding schemes.