Domain Selective Precoding in 3-D Massive MIMO Systems

Three-dimensional multiple input multiple output (3-D MIMO) with a large number of active antennas equipped in a uniformly rectangular antenna array has a significant potential in improving the system capacity. In this paper, we present an efficient two-dimensional (2-D) downlink precoding scheme for single-cell 3-D massive MIMO systems. Considering instantaneous channel state information at the base station, we show that either the elevation or azimuth domain can be used for interference cancellation. We divide the interference into two components, one of which is canceled in the elevation domain, while the other is canceled in the azimuth domain. Based on this domain selective (DS) strategy, two DS preceding algorithms are proposed for the single-path scenario based on the zero forcing and signal-to-leakage-plus-noise ratio criteria. Next, we extend our DS precoding scheme to a multi-path scenario. In the proposed algorithms, the precoding vectors of different users are determined in parallel, so as to reduce the computational complexity. Simulation results are provided to demonstrate that the proposed algorithms can achieve better spectral efficiency performance with a low computational complexity.