Performance Analysis of Wireless Communication Systems Assisted by Fluid Reconfigurable Intelligent Surfaces

TL;DR

This paper analyzes the performance of wireless systems enhanced by fluid reconfigurable intelligent surfaces (FRIS), showing they can significantly improve reliability and spectral efficiency over traditional RISs through dynamic element activation.

Contribution

It introduces a novel fluid-inspired RIS design and derives analytical expressions for channel behavior, outage probability, and capacity bounds, highlighting its advantages over conventional RISs.

Findings

FRIS improves link reliability and spectral efficiency.

Closed-form expressions for channel statistics are derived.

High SNR asymptotic behaviors are characterized.

Abstract

This letter investigates the performance of emerging wireless communication systems assisted by a fluid reconfigurable intelligent surface (FRIS). Unlike conventional reconfigurable intelligent surfaces (RISs), an FRIS consists of fluid-inspired metamaterials arranged in a densely packed matrix of sub-elements over a surface. It dynamically activates specific elements for signal reflection and modulation based on real-time channel conditions. Considering a downlink scenario where a base station communicates with a user terminal via a FRIS, we first characterize the statistical behavior of the equivalent end-to-end channel by deriving closed-form approximations for its cumulative distribution and probability density functions. Using these expressions, an analytical approximation for the outage probability and a tight upper bound on the ergodic capacity, including their asymptotic behaviors for high signal-to-noise ratio values, are derived. Our findings reveal key performance trends demonstrating that FRIS can substantially improve link reliability and spectral efficiency compared to conventional RISs, owing to its capability to dynamically select optimal elements from a dense preconfigured grid.