RIS-Assisted Physical Layer Security in Emerging RF and Optical Wireless Communication Systems: A Comprehensive Survey

TL;DR

This survey analyzes how reconfigurable intelligent surfaces (RIS) can bolster physical layer security (PLS) in both RF and optical wireless systems for future networks. It surveys fundamentals of PLS, RIS architectures (including optical variants), and a broad set of RF and optical RIS-assisted security applications, complemented by optimization and machine learning approaches to manage nonconvex design spaces. Key contributions include taxonomy of attacks and metrics, comprehensive review of RIS-enabled RF/OWC security techniques (AN, beamforming, cooperative jamming), cross-technology integration (mmWave, THz, UAV, D2D, CRNs, WPT/SWIPT, MEC, ISAC, VLC, FSO), and syntheses of performance analyses and open challenges. The paper emphasizes practical next steps—discrete phase-shifters, global optimization, and advanced ML techniques—to bridge theory and deployment, highlighting RIS as a pivotal enabler for secure, next-generation wireless networks with potential 6G impact.

Abstract

Physical layer security (PLS) has received a growing interest from the research community for its ability to safeguard data confidentiality without relying on key distribution or encryption/decryption. However, the evolution towards the 5G technology and beyond poses new security challenges that must be addressed in order to fulfill the unprecedented performance requirements of future wireless networks. Among the potential enabling technologies, RIS has attracted extensive attention due to its ability to proactively and intelligently reconfigure the wireless propagation environment to combat dynamic wireless channel impairments. Consequently, the RIS technology can be adopted to improve the information-theoretic security of both RF and OWC systems. This survey paper provides a comprehensive overview of the information-theoretic security of RIS-based RF and optical systems. The article first discusses the fundamental concepts of PLS and RIS technologies, followed by their combination in both RF and OWC systems. Subsequently, some optimization techniques are presented in the context of the underlying system model, followed by an assessment of the impact of RIS-assisted PLS through a comprehensive performance analysis. Given that the computational complexity of future communication systems that adopt RIS-assisted PLS is likely to increase rapidly as the number of interactions between the users and infrastructure grows, ML is seen as a promising approach to address this complexity issue while sustaining or improving the network performance. A discussion of recent research studies on RIS-assisted PLS-based systems embedded with ML is presented. Furthermore, some important open research challenges are proposed and discussed to provide insightful future research directions, with the aim of moving a step closer towards the development and implementation of the forthcoming 6G wireless technology.

Figures (9)

• Figure 1: Comparison of some between and communication systems wang2023road.
• Figure 2: Wireless wiretap system model.
• Figure 3: 4-element with (a) single connected reconfigurable impedance network, (b) fully connected reconfigurable impedance network, and (c) group connected (2 groups and group size of 2) reconfigurable impedance network.
• Figure 4: Illustration of signal propagation on an , where UE$1$ and UE$2$ denote User $1$ and User 2, respectively.
• Figure 5: An -aided multi-user downlink communication system with different deployment strategies.