Two-Step Codebook-Assisted Alternating Minimization (CA-AltMin) for Low-Complexity Hybrid Beamforming Design

Hybrid beamforming can effectively reduce the cost of millimeter wave multiple-input-multiple-output (MIMO) system. However, the analog beamformer realized by the unit-norm phase shifters makes the design of the hybrid beamformers a complicated non-convex optimization problem, and prior works suffer from high computational complexity. In this letter, we focus on the single-user scenario and propose a two-step procedure for the low-complexity hybrid beamforming design. The first step employs a codebook-based algorithm to provide an initial setting of the hybrid beamformers. The second step employs the AltMin-based algorithm to refine the hybrid beamformers. In particular, we also modify the loss function used in the AltMin algorithm for complexity reduction. Simulation results show that the proposed codebook-assisted AltMin (CA-AltMin) reduces the complexity by 96% and achieves better performance than the state-of-the-art algorithms from different technical aspects.