Movable Subarray-Aided Hybrid Beamforming for Near-Field Multiuser Communications

TL;DR

This paper introduces a movable subarray hybrid beamforming architecture for near-field multiuser MIMO systems, balancing hardware practicality and spatial flexibility to enhance beamfocusing and interference mitigation.

Contribution

It proposes a novel MSA-aided HBF design that exploits NF DoFs and MSA movement, along with an efficient channel approximation and optimization algorithm.

Findings

Significant sum-rate improvements over fixed-position antenna benchmarks.

Effective exploitation of NF distance and MSA position DoFs for beamfocusing.

Reduced computational complexity with the proposed channel model and optimization methods.

Abstract

Movable antenna (MA)-enabled near-field (NF) communications offer significant potential for 6G, yet existing designs often neglect the practical constraints of hybrid beamforming (HBF) for extremely large-scale MIMO (XL-MIMO). Conversely, MA-aided HBF frequently overlooks the rich NF degrees of freedom (DoFs). This paper proposes a movable subarray (MSA)-aided HBF architecture for NF multiuser systems, which strikes a strategic balance between hardware practicality and spatial flexibility. By coupling MSA movement with HBF, the proposed design simultaneously exploits NF distance-dependent and MSA position-dependent DoFs, enabling highly precise beamfocusing and superior interference mitigation. To alleviate the computational burden, a hybrid planar-spherical wave model is introduced for efficient channel approximation. Furthermore, an alternating optimization (AO) algorithm is developed by integrating fractional programming, the alternating direction method of multipliers (ADMM), and projected gradient ascent. Simulation results validate substantial sum-rate gains over fixedposition antenna (FPA) benchmarks.