FAS-RIS for V2X: Unlocking Realistic Performance Analysis with Finite Elements

TL;DR

This paper introduces a new framework for analyzing FAS-RIS systems in V2X communications, providing more accurate performance predictions for finite-sized deployments by using a Gamma distribution approximation instead of the traditional CLT-based methods.

Contribution

It presents a novel finite-element performance analysis framework for FAS-RIS systems in V2X, replacing CLT assumptions with a Gamma distribution approximation for better accuracy.

Findings

The Gamma distribution approximation yields more accurate outage probability estimates.

Numerical results show improved performance characterization over CLT-based methods.

The framework is particularly effective for small-scale RIS deployments.

Abstract

The synergy of fluid antenna systems (FAS) and reconfigurable intelligent surfaces (RIS) is poised to unlock robust Vehicle-to-Everything (V2X) communications. However, a critical gap persists between theoretical predictions and real-world performance. Existing analyses predominantly rely on the Central Limit Theorem (CLT), an assumption valid only for a large number of RIS elements, which fails to represent practical, finite-sized deployments constrained by cost and urban infrastructure. This paper bridges this gap by presenting a novel framework that unlocks a realistic performance analysis for FAS-RIS systems with finite elements. Leveraging a Gamma distribution approximation, we derive a new, tractable closed-form expression for the outage probability. Numerical results validate our approach, demonstrating that it offers a significantly more accurate performance characterization than conventional CLT-based methods, particularly in the practical regime of small-scale RIS. This work provides a crucial foundation for the design and deployment of reliable FAS-RIS-aided vehicular networks.