Beamforming designs for multiuser transmissions in FDD massive MIMO systems using partial CSIT

In this paper, we consider an effective acquisition mechanism of partial channel state information at the transmitter (CSIT) for frequency-division duplex (FDD) massive MIMO systems, based on which two downlink beamforming methods are proposed. The partial CSIT is in the form of downlink angles of departure (AoDs) and the amplitudes of the strongest paths of each UE. By exploiting the reciprocity between downlink AoDs and uplink angles of arrival (AoAs), the partial CSIT can be acquired through downlink training and uplink feedback effectively. Therefore, the feasibility of FDD massive MIMO systems is greatly enhanced. Simulation results demonstrate the superiority of the proposed methods compared to other methods in the sense of fairness and achievable sum rate.