Hybrid Beamforming Strategy for Wideband Millimeter Wave Channel Models

Hybrid analog-digital beamforming design based on the channel state information (CSI) for wideband millimeter wave channel models receives attention in recent years. However, without the CSI, most previously proposed beamforming methods, such as singular value decomposition (SVD)-based ones, are almost infeasible due to the complexity of both the channel estimation and SVD for large antenna arrays. To this end, this paper presents a viable approach which shows that the angles of departure and arrival associated with the NRF strongest paths can be approximated by the NRF pairs of steering angles. Then the residual phase angles together with the phases caused by the different multipath delays can be further compensated by the digital beamforming. Compared with the SVD-based beamforming schemes, the proposed hybrid beamforming can be easily implemented without the channel estimation and SVD.