Performance Analysis of Fluid Reconfigurable Intelligent Surface over Covert Communications

TL;DR

This paper analyzes how fluid reconfigurable intelligent surfaces (FRIS) enhance covert communication by improving reliability and covertness, especially at low-to-moderate transmit powers, through theoretical derivations and numerical evaluations.

Contribution

It provides the first analytical framework for assessing the impact of FRIS on covert communications, including closed-form expressions for covertness outage probability and success probability.

Findings

FRIS outperforms fixed RIS at low-to-moderate power levels in covertness and reliability.

Analytical expressions for FA, MD, and COP are derived.

At very high power, fixed RIS may offer slightly better success probability.

Abstract

This paper investigates the impact of the recently proposed concept of fluid reconfigurable intelligent surfaces (FRIS) on covert communications. Specifically, we consider a communication scenario where a legitimate transmitter aims to covertly deliver information to its intended receiver through a planar FRIS, while an adversary attempts to detect whether any transmission is occurring. In this context, we analyze the false alarm (FA) and missed detection (MD) probabilities, and derive a closed-form expression for the covertness outage probability (COP). Furthermore, the success probability is characterized under the optimal detection threshold, providing new insights into the trade-off between covertness and reliable transmission. Numerical results reveal that FRIS provides a clear advantage over fixed-position RIS at low-to-moderate transmit powers by improving reliability and enhancing covertness, while at very high power levels, fixed-position RIS may sustain slightly higher success probability due to reduced leakage toward the adversary.