Hybrid Analog-Digital Beamforming for Multiuser MIMO Millimeter Wave Relay Systems

TL;DR

This paper introduces a hybrid analog-digital beamforming approach for multiuser millimeter wave relay systems, optimizing sum rate by minimizing MSE and leveraging compressive sensing, achieving near-digital performance.

Contribution

It proposes a novel hybrid beamforming design using MSE minimization and compressive sensing, specifically tailored for multiuser mm-wave relay systems, with analysis of RF chains and AoA/AoD estimation effects.

Findings

Hybrid beamforming achieves performance close to digital beamforming.

Increasing RF chains and paths improves sum rate.

Better AoA/AoD estimation enhances system performance.

Abstract

This paper proposed new hybrid, analog-digital, beamforming for a multiuser millimeter wave (mm-wave) relay system. For this system, we consider a sum rate maximization problem. The proposed hybrid beamforming is designed indirectly by considering a sum mean square error (MSE) minimization problem while utilizing the solution of digital beamforming. To this end, we assume that the digital beamforming utilizes the well known block diagonalization (BD) approach. Under this assumption, we solve our problem as follows: First, we formulate the sum rate maximization problem as the minimization of the MSE between the received signal of the hybrid and digital beamforming designs. Then, we design the hybrid beamformings of the source, relay and each destination by leveraging compressive sensing techniques. Simulation results confirm that the proposed hybrid beamforming design achieves performance very close to that of the digital one. Furthermore, we have examined the effects of the number of radio frequency (RF) chains and paths together, and the accuracy of angle of arrival (AoA) and angle of departure (AoD) estimators on the sum rate of the hybrid beamforming designs. Computer simulations reveal that the total sum rate of the hybrid beamforming increases when the number of RF chains and paths increase (or the accuracy of the AoA (AoD) estimator improves).