An Equivalent Channel-based Hybrid Precoding Scheme for Multi-user Massive MIMO Systems

For 5G/B5G communication systems, to cater the explosive demands in communication rates, extending communication band to millimeter wave (mmWave) seems to be an essential solution, and hence massive multiple-input-multiple-output (MIMO) architecture is usually adopted to combat the severe path-loss of mmWave signals. However, the traditional fully digital precoding manner is inapplicable owing to its high hardware cost and power consumption rendered by the individual requirements on radio frequency (RF) chains of each antenna. In this paper, for massive MIMO systems with multiple users, a novel hybrid precoding scheme is proposed based on the concept of equivalent channel. Specifically, for each user in the system, its analog combiner and analog precoder are designed jointly aiming to maximize the achievable rate with its equivalent channel. After the analog precoder/combiner phase-shifters for each user has been obtained, see them as a part of the channel and form a comprehensive channel of the multi-user system, and then the total baseband digital precoding at the BS is implemented with the block diagonalization method to delete the interference among users. Simulation results show that the proposed scheme can achieve higher spectral efficiency with low complexity compared to the existing schemes.