Hybrid beamforming for multi-user MIMO with partially-connected RF architecture

The traditional fully-digital beamforming is realised by the full radio-frequency (RF) chain configuration, which will be impracticable in massive multiple-input multiple-output (MIMO) systems because of the overburden energy consumption of RF chains at millimetre wave frequencies. To address this issue, a series of hybrid beamforming schemes have been proposed to reduce the number of RF chains. Although the hybrid beamforming schemes for single-user MIMO (SU-MIMO) have been studied extensively, the performance of hybrid beamforming for multi-user MIMO (MU-MIMO), especially for partially-connected hybrid architecture, still has room for improvement. In this study, the authors propose a hybrid beamforming scheme for MU-MIMO systems. Specifically, they focus on the design of analogue beamforming and optimise the analogue RF precoders and combiners jointly. The simulation results show that the proposed hybrid beamforming in fully-connected structure can achieve a better performance compared with the existing hybrid beamforming schemes in both SU-MIMO and MU-MIMO systems. It is also observed that the proposed hybrid beamforming can achieve significant performance advantages compared with the existing hybrid beamforming schemes in partially-connected structures.