Beamforming-based spatial precoding in FDD massive MIMO systems

In order to enable frequency-division duplex (FDD) massive multiple-input-multiple-output (MIMO) systems, a beam-grouping, precoding and feedback scheme is proposed to reduce the downlink training overhead and channel state information (CSI) feedback overhead. When the number of transmit antennas on a base station (BS) is growing large, the downlink training overhead for CSI estimation and the CSI feedback overhead are growing tremendously. In addition to the downlink training overhead, simulation results show that the proposed method is able to reduce the feedback overhead without sacrificing the downlink achievable information rate (AIR). Furthermore, the proposed method has a lower computation complexity comparing with other methods in the recent literature.