[Paper Review] Reconfigurable Intelligent Surfaces-Enabled Vehicular Networks: A Physical Layer Security Perspective

Abubakar U. Makarfi, Khaled M. Rabie+5 more|arXiv (Cornell University)|Apr 1, 2020

Advanced Wireless Communication TechnologiesEngineering49 references47 citations

TL;DR

The paper analyzes the physical layer security of RIS-enabled vehicular networks, deriving ASC and SOP expressions for two models (V2V with RIS-AP and VANET with RIS relay) and validating them with Monte Carlo simulations.

ABSTRACT

This paper studies the physical layer security (PLS) of a vehicular network employing reconfigurable intelligent surfaces (RISs). RIS technologies are emerging as an important paradigm for the realisation of next-generation smart radio environments, where large numbers of small, low-cost and passive elements, reflect the incident signal with an adjustable phase shift without requiring a dedicated energy source. Inspired by the promising potential of RIS-based transmission, we investigate the PLS of two vehicular network system models: One with vehicle-to-vehicle communication with the source employing a RIS-based access point, and the other is in the form of a vehicular adhoc network (VANET), with a RIS-based relay deployed on a building; both models assume the presence of an eavesdropper. The performance of the proposed systems are evaluated in terms of the average secrecy capacity (ASC) and the secrecy outage probability (SOP). We present accurate analytical expressions for the two performance metrics and study the impact of various system parameters on the overall performance of the two considered system configurations. Monte-Carlo simulations are provided throughout to validate the results. The results show that performance of the system in terms of the ASC and SOP is affected by the location of the RIS-relay as well as the number of RIS cells. Moreover, upto an order magnitude gain could be achieved within certain regions when the number of RIS cells are doubled, clearly indicating the benefit of employing a RIS configuration.

Motivation & Objective

• Motivate RIS as a viable technology for mobile vehicular networks to enhance security at the physical layer.
• Model two RIS-enabled vehicular scenarios and quantify secrecy performance under eavesdropping.
• Derive accurate analytical expressions for average secrecy capacity (ASC) and secrecy outage probability (SOP).
• Provide approximate closed-form solutions to facilitate parameter insights and design guidance.

Proposed method

• Model 1 (V2V with RIS as Access Point): derive ASC and SOP using SNR expressions at destination and eavesdropper and their MGFs; express ASC via a joint integral and convert to MGF-based form.
• Model 2 (VANET with RIS relay): derive ASC and SOP with RIS on a building acting as a relay; treat cascaded and double-Rayleigh fading channels; obtain MGFs and use CLT for SOP.
• Use Meijer G-functions and Gauss hypergeometric functions to characterize MGFs and CDFs of the cascaded channels.
• Provide an approximate ASC expression via Jensen’s inequality for tractability and insight.
• Validate analytical results with Monte Carlo simulations across system parameters (RIS size, link distances, transmit power).
• Present closed-form approximate ASC expressions to enable easier parameter analysis.

Experimental results

Research questions

• RQ1 How does RIS deployment (as AP or relay) affect secrecy performance in RIS-enabled vehicular networks?
• RQ2 What are the closed-form or easily computable expressions for ASC and SOP in the two RIS-enabled vehicular network models?
• RQ3 How do system parameters (number of RIS cells, distances, transmit power) impact secrecy metrics?
• RQ4 Do approximate ASC expressions accurately reflect exact results across practical regimes?

Key findings

• RIS configurations improve secrecy capacity in vehicular networks compared to non-RIS setups.
• Secrecy performance is sensitive to RIS location and the number of RIS cells, with larger RISs delivering substantial gains.
• Doubling the number of RIS cells can yield up to an order of magnitude improvement in secrecy metrics within certain regions.
• The authors provide accurate exact expressions and tractable approximate closed-form solutions that align well with Monte Carlo results.
• Monte Carlo simulations validate the analytical results across varied parameter settings.
• The work demonstrates the feasibility and security benefits of RIS-enabled approaches for beyond-5G vehicular communications.