Two-Stage Precoding Method for the Finitely Large-Scale Antenna Systems

Abstract

A simple matched-filter, which known as a promising precoder in a massive multiple-input multiple-output (MIMO) system, would not achieve the multi-user MIMO downlink capacity when base station equipped with finitely large number of antennas, due to multi-user interference. In this paper, a two-stage precoder design method has been proposed to maximize the sum-rate of cell-edge users when base station equipped with finitely large number of antennas. In the first stage, a matched-filter precoder is adopted to exploit both beamforming gain and the dimensional reduction of effective channels. Then, we derive the second stage precoder that maximizes the sum-rate by minimizing the weighted mean-squared-error. Simulation results and analysis verify the effectiveness of the proposed scheme. A modified transceiver design method is also presented which provides desired robustness in the presence of channel uncertainty.