Downlink beamforming with estimated DOA from uplink transmission

This paper proposes a downlink beamforming scheme at the base station (BS) in wireless communication systems based on the estimated directions-of-arrival (DOA) information obtained from uplink signals. Procedures corresponding to traditional linearly constrained minimum variance (LCMV) scheme, zero-forcing based multiple-input multiple-output (MIMO) scheme and the proposed two stage downlink beamforming scheme are described. Simulation results presented clarify that with significantly less required feedback information, our two stage downlink beamforming scheme can achieve better BER performance, especially in high SNR region. This makes the proposed scheme suitable for a multiuser downlink transmission scenario.