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arXiv · 2505.19523

Near-Field Secure Beamfocusing With Receiver-Centered Protected Zone

Cen Liu·Xiangyun Zhou·Nan Yang·Salman Durrani·A. Lee Swindlehurst
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Abstract

This work studies near-field secure communications through transmit beamfocusing. We examine the benefit of having a protected eavesdropper-free zone around the legitimate receiver, and we determine the worst-case secrecy performance against a potential eavesdropper located anywhere outside the protected zone. A max-min optimization problem is formulated for the beamfocusing design with and without artificial noise transmission. Despite the NP-hardness of the problem, we develop a synchronous gradient descent-ascent framework that approximates the global maximin solution. A low-complexity solution is also derived that delivers excellent performance over a wide range of operating conditions. We further extend this study to a scenario where it is not possible to physically enforce a protected zone. To this end, we consider secure communications through the creation of a virtual protected zone using a full-duplex legitimate receiver. Numerical results demonstrate that exploiting either the physical or virtual receiver-centered protected zone with appropriately designed beamfocusing is an effective strategy for achieving secure near-field communications.

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Cen Liu, Xiangyun Zhou, Nan Yang, Salman Durrani, A. Lee Swindlehurst. 2025-05-26. Near-Field Secure Beamfocusing With Receiver-Centered Protected Zone. https://doi.org/10.1109/twc.2025.3624793

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