Near-Field Communication with Massive Movable Antennas: An Electrostatic Equilibrium Perspective

2025-12-25

AI Summary

To address the poor scalability of conventional antenna layouts and the spectral efficiency degradation caused by neglecting near-field effects in near-field massive MIMO systems, this paper proposes a reconfigurable antenna placement method grounded in angular-domain reconstruction and electrostatic equilibrium principles. We formulate antenna placement as a weighted Fekete problem for the first time, revealing its intrinsic electrostatic equilibrium nature. The optimal antenna positions are derived analytically as roots of a specific ordinary differential equation (ODE)-based polynomial, and a closed-form asymptotic solution is obtained for the infinite-antenna limit. By integrating two-stage eigenvalue decomposition with asymptotic analysis, the proposed method significantly enhances spectral efficiency while exhibiting strong robustness against channel parameter mismatches. The closed-form solution closely approximates the theoretical optimum across a wide range of practical scenarios, substantially reducing computational complexity.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Multiagent Systems: Mechanism Design

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• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
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• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

Recent advancements in large-scale position-reconfigurable antennas have opened up new dimensions to effectively utilize the spatial degrees of freedom (DoFs) of wireless channels. However, the deployment of existing antenna placement schemes is primarily hindered by their limited scalability and frequently overlooked near-field effects in large-scale antenna systems. In this paper, we propose a novel antenna placement approach tailored for near-field massive multiple-input multiple-output systems, which effectively exploits the spatial DoFs to enhance spectral efficiency. For that purpose, we first reformulate the antenna placement problem in the angular domain, resulting in a weighted Fekete problem. We then derive the optimality condition and reveal that the {optimal} antenna placement is in principle an electrostatic equilibrium problem. To further reduce the computational complexity of numerical optimization, we propose an ordinary differential equation (ODE)-based framework to efficiently solve the equilibrium problem. In particular, the optimal antenna positions are characterized by the roots of the polynomial solutions to specific ODEs in the normalized angular domain. By simply adopting a two-step eigenvalue decomposition (EVD) approach, the optimal antenna positions can be efficiently obtained. Furthermore, we perform an asymptotic analysis when the antenna size tends to infinity, which yields a closed-form solution. Simulation results demonstrate that the proposed scheme efficiently harnesses the spatial DoFs of near-field channels with prominent gains in spectral efficiency and maintains robustness against system parameter mismatches. In addition, the derived asymptotic closed-form {solution} closely approaches the theoretical optimum across a wide range of practical scenarios.

Problem

• Optimizes antenna placement for near-field massive MIMO systems
• Solves electrostatic equilibrium problem to enhance spectral efficiency
• Reduces computational complexity with ODE-based framework and eigenvalue decomposition

Innovation

• Reformulating antenna placement as electrostatic equilibrium problem
• Solving equilibrium via ODE-based framework with polynomial roots
• Efficiently obtaining positions using two-step eigenvalue decomposition