Movable Antenna-Aided Hybrid Beamforming for Multi-User Communications

TL;DR

This paper introduces a movable antenna-assisted hybrid beamforming scheme for multi-user communications, optimizing antenna positions and beamformers to significantly enhance system sum rate over fixed-position arrays.

Contribution

It proposes a novel movable antenna scheme with joint optimization of beamformers and antenna positions, outperforming fixed-position and fully-connected arrays.

Findings

Significant sum rate improvement over fixed-position arrays.

Movable antenna scheme outperforms fixed and fully-connected arrays with large movable regions.

Effective optimization framework using fractional programming and alternating optimization.

Abstract

In this correspondence, we propose a movable antenna (MA)-aided multi-user hybrid beamforming scheme with a sub-connected structure, where multiple movable sub-arrays can independently change their positions within different local regions. To maximize the system sum rate, we jointly optimize the digital beamformer, analog beamformer, and positions of subarrays, under the constraints of unit modulus, finite movable regions, and power budget. Due to the non-concave/non-convex objective function/constraints, as well as the highly coupled variables, the formulated problem is challenging to solve. By employing fractional programming, we develop an alternating optimization framework to solve the problem via a combination of Lagrange multipliers, penalty method, and gradient descent. Numerical results reveal that the proposed MA-aided hybrid beamforming scheme significantly improves the sum rate compared to its fixed-position antenna (FPA) counterpart. Moreover, with sufficiently large movable regions, the proposed scheme with sub-connected MA arrays even outperforms the fully-connected FPA array.