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Auteurs principaux: Li, Yongqiang, Shu, Feng, Chen, Shaofan, Wu, Yuanyuan, Li, Maolin, Chen, Zhen, Jiang, Hao, Wang, Jiangzhou
Format: Preprint
Publié: 2026
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Accès en ligne:https://arxiv.org/abs/2603.20608
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_version_ 1866910061961412608
author Li, Yongqiang
Shu, Feng
Chen, Shaofan
Wu, Yuanyuan
Li, Maolin
Chen, Zhen
Jiang, Hao
Wang, Jiangzhou
author_facet Li, Yongqiang
Shu, Feng
Chen, Shaofan
Wu, Yuanyuan
Li, Maolin
Chen, Zhen
Jiang, Hao
Wang, Jiangzhou
contents This paper investigates secure Directional Modulation (DM) design enhanced by a rotatable active Reconfigurable Intelligent Surface (RIS). In conventional RIS-assisted DM networks, the security performance gain is limited due to the multiplicative path loss introduced by the RIS reflection path. To address this challenge, a Secrecy Rate (SR) maximization problem is formulated, subject to constraints including the eavesdropper's Direction Of Arrival (DOA) estimation performance, transmit power, rotatable range, and maximum reflection amplitude of the RIS elements. To solve this non-convex optimization problem, three algorithms are proposed: a multi-stream null-space projection and leakage-based method, an enhanced leakage-based method, and an optimization scheme based on the Distributed Soft Actor-Critic with Three refinements (DSAC-T). Simulation results validate the effectiveness of the proposed algorithms. A performance trade-off is observed between eavesdropper's DOA estimation accuracy and the achievable SR. The security enhancement provided by the RIS is more significant in systems equipped with a small number of antennas. By optimizing the orientation of the RIS, a 52.6\% improvement in SR performance can be achieved.
format Preprint
id arxiv_https___arxiv_org_abs_2603_20608
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Reinforcement Learning-Based Secure Near-field Directional Modulation Enhanced by Rotatable RIS
Li, Yongqiang
Shu, Feng
Chen, Shaofan
Wu, Yuanyuan
Li, Maolin
Chen, Zhen
Jiang, Hao
Wang, Jiangzhou
Signal Processing
This paper investigates secure Directional Modulation (DM) design enhanced by a rotatable active Reconfigurable Intelligent Surface (RIS). In conventional RIS-assisted DM networks, the security performance gain is limited due to the multiplicative path loss introduced by the RIS reflection path. To address this challenge, a Secrecy Rate (SR) maximization problem is formulated, subject to constraints including the eavesdropper's Direction Of Arrival (DOA) estimation performance, transmit power, rotatable range, and maximum reflection amplitude of the RIS elements. To solve this non-convex optimization problem, three algorithms are proposed: a multi-stream null-space projection and leakage-based method, an enhanced leakage-based method, and an optimization scheme based on the Distributed Soft Actor-Critic with Three refinements (DSAC-T). Simulation results validate the effectiveness of the proposed algorithms. A performance trade-off is observed between eavesdropper's DOA estimation accuracy and the achievable SR. The security enhancement provided by the RIS is more significant in systems equipped with a small number of antennas. By optimizing the orientation of the RIS, a 52.6\% improvement in SR performance can be achieved.
title Reinforcement Learning-Based Secure Near-field Directional Modulation Enhanced by Rotatable RIS
topic Signal Processing
url https://arxiv.org/abs/2603.20608