Performance Analysis of Fluid Reconfigurable Intelligent Surface over Covert Communications
Farshad Rostami Ghadi, Masoud Kaveh, Hanjiang Hong, Kai-Kit Wong, Riku Jantti, F. Javier Lopez-Martinez
TL;DR
The paper investigates fluid reconfigurable intelligent surfaces (FRIS) in covert communications, developing a tractable analytical framework to quantify covertness (COP) and reliability (OP, SUC). By employing Gamma approximations and moment matching for the FRIS-induced channels, it derives closed-form expressions for COP and related metrics under an optimal detector. Results show FRIS offers clear gains over fixed RIS at low-to-moderate transmit powers due to adaptive element selection, while at very high powers the leakage toward the warden can reduce the SUC advantage. These insights reveal a power-dependent trade-off and provide guidance for the design of FRIS-enabled covert systems.
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.