Optimal Movable Antenna Placement for Near-Field Wireless Sensing

2026-03-11

AI Summary

This work addresses the limitation of fixed antenna arrays in near-field wireless sensing, where constrained spatial degrees of freedom hinder minimization of worst-case localization error. The study investigates optimal placement strategies for movable antennas by minimizing the worst-case squared position error bound (SPEB). Theoretical analysis establishes the optimality of center-symmetric configurations and reduces the worst-case source localization problem to the Rayleigh limit along the array broadside. By integrating the method of moments with the Richter–Tchakaloff theorem, the authors derive a closed-form optimal solution supported on only three points, which satisfies minimum inter-element spacing constraints while enabling highly efficient computation. The proposed scheme achieves performance nearly matching exhaustive search with negligible computational overhead, significantly outperforming conventional fixed-array approaches.

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Abstract

Movable antennas (MAs) have emerged as a promising technology for wireless sensing by reconfiguring antenna positions to exploit additional spatial degrees of freedom (DoFs). This paper investigates a robust movable antenna placement strategy for near-field wireless sensing to minimize the worst-case squared position error bound (SPEB). By temporarily relaxing the minimum inter-element spacing constraint, we first establish the optimality of centro-symmetric antenna position distribution, which simplifies the identification of the worst-case source, locating it at the array broadside on the Rayleigh boundary. Moreover, by leveraging moment-based analysis with the Richter-Tchakaloff theorem, we derive a closed-form optimal solution with three points supported on the center and two edges of the array. Guided by this structural insight, we finally develop an efficient three-point discrete deployment strategy to ensure the minimum inter-element spacing. Simulations demonstrate that the proposed design consistently outperforms conventional fixed antenna arrays and matches the exhaustive search benchmark at negligible computational complexity.

Problem

• movable antennas
• near-field wireless sensing
• position error bound
• antenna placement
• spatial degrees of freedom

Innovation

• movable antennas
• near-field sensing
• optimal placement
• squared position error bound
• moment-based analysis