Robust and Secure Near-Field Communication via Curved Caustic Beams

2026-03-25

AI Summary

This work addresses the vulnerability of near-field secure communication to eavesdropper location estimation errors, which can cause beam misalignment and severely degrade physical-layer security. To mitigate this issue, the paper introduces electromagnetic caustics—a concept previously unexplored in this context—into near-field secure communications and proposes a robust beamforming method. By leveraging phase-gradient engineering, the large-aperture array is partitioned into caustic and focusing subarrays, enabling a piecewise closed-form phase distribution that simultaneously avoids potential eavesdropping regions and accurately serves legitimate users. The proposed approach significantly enhances robustness against localization inaccuracies, reducing the worst-case eavesdropping rate by up to 80% under a practical positioning error of 0.25 meters, thereby substantially improving system security.

Technology Category

• Search and Optimization: Distributed Search
• Intelligent Robots: Localization, Mapping, and Navigation
• Computer Vision: Adversarial Attacks & Robustness

Application Category

• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systems
• Systems and Infrastructure for Web, Mobile and WoT: Location- and context-aware Web and WoT applications and services

Abstract

Near-field beamfocusing with extremely large aperture arrays can effectively enhance physical layer security. Nevertheless, even small estimation errors of the eavesdropper's location may cause a pronounced focal shift, resulting in a severe degradation of the secrecy rate. In this letter, we propose a physics-informed robust beamforming strategy that leverages the electromagnetic (EM) caustic effect for near-field physical layer security provisioning, which can be implemented via phase shifts only. Specifically, we partition the transmit array into caustic and focusing subarrays to simultaneously bypass the potential eavesdropping region and illuminate the legitimate user, thereby significantly improving the robustness against the localization error of eavesdroppers. Moreover, by leveraging the connection between the phase gradient and the EM wave departing angle, we derive the corresponding piece-wise closed-form array phase profile for the subarrays. Simulation results demonstrate that the proposed scheme achieves up to an 80% reduction of the worst-case eavesdropping rate for a localization error of 0.25 m, highlighting its superiority for providing robust and secure communication.

Problem

• near-field communication
• physical layer security
• eavesdropper localization error
• beamforming robustness
• secrecy rate

Innovation

• caustic beams
• near-field beamforming
• physical layer security
• robust communication
• phase-only control