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arXiv · 2603.05922

Beamforming Optimization for Extremely Large-Scale RIS-Aided Near-Field Secure Communications

Xiaotong Xu·Qian Zhang·Yunxiao Li·Xuejun Cheng·Meihui Liu·Ju Liu
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Abstract

This paper studies an extremely large-scale reconfigurable intelligent surface (XL-RIS)-aided near-field physical layer security (PLS) communication system, aiming to maximize the secrecy rate by jointly optimizing precoding vector at the BS and the reflection coefficient matrix at the XL-RIS. Artifi-cial jamming was introduced to further enhance communication security. To solve the non-convex secrecy rate problem, an alternate optimization-based algorithm is adopted to decompose it into two sub-problems. Specifically, when optimizing the transmit beamformer at the BS, the non-convex prob-lem is transformed into a convex one through the weighted minimum mean-square error and the successive convex approximation-based algorithms. For the optimization problem of the XL-RIS phase-shifting matrix, a low-complexity alternating direction method of multipliers-based algorithm is employed to enhance the flexibility of the design. The proposed algorithm is capable of accommodating discrete phase optimization for the XL-RIS, thus better aligning with practical system requirements. Simulation results demonstrate that when the eavesdropper reside in the same direction as the legitimate user and is located closer to the XL-RIS, the proposed scheme in this paper can still ensure the secure communication.

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Xiaotong Xu, Qian Zhang, Yunxiao Li, Xuejun Cheng, Meihui Liu, Ju Liu. 2026-03-06. Beamforming Optimization for Extremely Large-Scale RIS-Aided Near-Field Secure Communications. https://arxiv.org/abs/2603.05922

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