Hybrid Beamforming with Fixed Phase Shifters in OFDM-Based Multiuser MISO Systems

This paper focuses on the study of hybrid beamforming (HBF) design, which aims to reduce hardware complexity and energy consumption in massive multiple-input and multiple-output (MIMO) systems that operate in frequency-selective channels. The proposed HBF architecture utilizes fixed phase shifters (FPSs) and switches to perform analog beamforming coefficients in an orthogonal frequency division multiplexing (OFDM) multiuser multiple-input and single-output (MISO) system. Our design aims to maximize the downlink sum rate while satisfying power constraints for each sub carrier by jointly optimizing the digital and analog precoder coefficients. To address the underlying non-convex optimization problem, we employ the alternating optimization approach and fractional programming (FP) technique. Through numerical studies, we demonstrate the effectiveness of our proposed design compared to baselines under different network settings.