A New Codebook Design for Hybrid Beamforming Systems using Quantized Phase Shifters

Abstract

We consider a hybrid beamforming system, where the overall beamformer consists of a low-dimensional baseband beamformer and an radio frequency (RF) beamformer implemented by using analog phase shifters. In practice, the analog phase shifters are imperfect and are controlled with several quantized phases. This makes the channel estimation difficult in codebook-based beamforming schemes. In this paper, we propose a new codebook-based beamforming scheme to address the challenge of the quantized phase shifters. The fundamental idea is to design new codebook beams by logically separating a full antenna array into some subarrays and by mirroring a half of weights of subarrays from the rest weights. Numerical results show that the proposed scheme outperforms the conventional scheme using discrete Fourier transform (DFT) beams.