A Low-Complexity Precoding Scheme for Two-User Massive MIMO Downlink

This paper proposes a low-complexity precoding scheme for the downlink of single-cell two-user massive multi-input- multi-output (MIMO) systems, which can be seen as a combination of matched-filter (MF) precoding with extra user power adjustment. In this scheme, the base station (BS) antennas are grouped into two sets according to their channels, then each set has a main user to serve and a power coefficient is introduced to adjust the weighting between main user and the other user. Via theoretical analysis on the statistical properties of the signal power and interference power, the achievable sum-rate is derived. In addition, the power adjustment coefficient optimization with respect to the sum-rate maximization is solved. Our results show that the proposed precoding outperforms the standard MF precoding.