Hybrid Combining Based on Selective Activation of Double Constant Phase Shifters

In this paper, we propose a new uplink hybrid beamforming architecture for multi-user multiple-input-multiple-output (MU-MIMO) millimeter-wave (mmWave) systems. The proposed architecture employs constant phase shifters (CPSs) to control the phases of the signals in conjunction with double switches for signal selection in the radio frequency (RF) beamforming part. By using double switches to approximate the optimal double variable phase shifter (VPS)-based scheme, the proposed scheme can achieve near-optimal sum rates when the number of CPSs is large enough. In addition, with the support of the active/inactive switches, it selectively combines the antenna signals, which can further improve the sum rate while reducing power consumption. The simulation results show that the proposed scheme outperforms conventional VPS-based and fully digital combiners in terms of energy efficiency.