Low-Complexity Blind Hybrid Beamforming for mmWave MIMO Reception

This paper presents a computationally simple scheme for hybrid beamforming at millimeter wave (mmWave). A uniform linear array (ULA) is used with a number of subarrays each comprising a subset of the ULA. A small number of subarray-level analog scanning beams are used to obtain an initial coarse estimation of the Direction of Arrival (DoA) of the incoming signal. One of the analog beams is selected by maximizing the average received signal power at the output of all the subarrays and its output is sent to a blind iterative digital beamformer operating at the baseband. The digital beamformer does not incur the signal power loss due to quantization of the digital domain beam scanning and its output is used to reorient the DoA of the selected analog beam to prevent the signal power loss at the output of the analog beam. We demonstrate through numerical analysis that our proposal performs close to the theoretical limits with a reduced complexity compared to the existing techniques in the literature.