Low Complexity Hybrid Beamforming for Uplink Multiuser mmWave MIMO Systems

This paper considers a low-complexity hybrid beamforming (HBF) for uplink multiuser mmWave MIMO systems. The proposed scheme employs a two-stage beamforming design. In the first stage, the base station (BS) analog beamforming is designed to maximize the $k$th user's signal-to-interference-plus-noise-ratio (SINR) in single-carrier systems and to maximize the sum rate's upper bound of uplink virtual cooperative users in orthogonal frequency division multiplexing (OFDM) based systems (also called multi-carrier systems), respectively. Furthermore, we perform phases extraction and quantize phase control on the obtained BS analog beamforming. In the second stage, the BS digital beamforming is designed by performing minimum mean square error (MMSE) with the low-dimensional effective channel. The proposed schemes are simulated in both ideal Rayleigh fading channels and sparsely scattered mmWave channels, approaching the sum rate performance of the full digital solution in single-carrier case and of the virtual uplink user cooperation scheme in multi-carrier case, respectively. The simulation results demonstrate that the proposed schemes outperform the existing HBF designs for uplink multiuser mmWave MIMO systems.