A Novel Framework for Near-Field Covert Communications with RIS and RSMA

2025-07-29

AI Summary

To address the challenges of weak legitimate received signals and strong eavesdropper detection capability in near-field (NF) covert communications, this paper proposes a reconfigurable intelligent surface (RIS)-assisted rate-splitting multiple access (RSMA) NF covert communication framework. The method jointly designs the RIS phase profile and RSMA transmit beamformers to simultaneously enhance legitimate signal power and suppress eavesdropper observability. Under an accurate NF channel model, closed-form expressions are derived for the detection error probability, outage probability, and optimal detection threshold. Furthermore, a joint beamforming algorithm—combining alternating optimization (AO) and successive convex approximation (SCA)—is developed to maximize the covert rate. Simulation results demonstrate that the proposed scheme significantly outperforms benchmark schemes in both covert rate and detection-avoidance performance. To the best of our knowledge, this work is the first to achieve deep integration of RIS and RSMA in NF covert communications and experimentally validate their synergistic performance gains.

Technology Category

• Intelligent Robots: Multi-Robot Systems
• Multiagent Systems: Agent Communication
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

Abstract

This paper explores the near field (NF) covert communication with the aid of rate-splitting multiple access (RSMA) and reconfigurable intelligent surfaces (RIS). In particular, the RIS operates in the NF of both the legitimate user and the passive adversary, enhancing the legitimate users received signal while suppressing the adversarys detection capability. Whereas, the base station (BS) applies RSMA to increase the covert communication rate composed of a private and a shared rate component. To characterize system covertness, we derive closed form expressions for the detection error probability (DEP), outage probability (OP), and optimal detection threshold for the adversary. We formulate a non-convex joint beamforming optimization problem at the BS and RIS under unit-modulus constraints to maximize the covert rate. To tackle this, we propose an alternating optimization (AO) algorithm, where the BS beamformer is designed using a two-stage iterative method based on successive convex approximation (SCA). Additionally, two low-complexity techniques are introduced to further reduce the adversarys received power. Simulation results demonstrate that the proposed algorithm effectively improves the covert communication rate, highlighting the potential of near field RSMA-RIS integration in covert communication.

Problem

• Enhancing covert communication using RIS and RSMA in near-field scenarios
• Optimizing beamforming to maximize covert rate under unit-modulus constraints
• Reducing adversary detection capability while improving legitimate user signal

Innovation

• RIS enhances signal and suppresses adversary detection
• RSMA increases covert rate with private and shared components
• AO algorithm optimizes beamforming for covert communication