On Performance of FAS-aided Covert Communications
Farshad Rostami Ghadi, Masoud Kaveh, Riku Jantti, F. Javier Lopez-Martinez
TL;DR
This work models covert communications with fluid antenna systems at both the receiver (Bob) and the warden (Willie). It develops a compact analytical framework to evaluate the covertness outage probability (COP) and outage probability (OP) under power-control, identifying the optimal detection threshold $\zeta^*$ that maximizes COP. The COP is expressed via a multivariate $t$-distribution (copula) to capture port correlations, and OP uses a similar copula-based form, linking secrecy and reliability through the success probability $P_{\mathrm{suc}}=P_{\mathrm{MD}}(\zeta^*)\cdot(1-P_{\mathrm{out}})$. Numerical results reveal that while FAS at Willie improves detection versus FPAs, equipping Bob with FAS yields substantial gains in reception and transmission reliability, guiding practical deployment of FAS in covert, 6G-like networks.
Abstract
This paper investigates the impact of deploying the fluid antenna system (FAS) on the performance of covert communications. In particular, we focus on a scenario where a transmitter seeks to covertly communicate with a receiver, while a warden attempts to detect the transmission. Both the receiver and the warden are assumed to utilize planar FAS. We derive compact analytical expressions for the covertness outage probability (COP), defined as the complement of the sum of false alarm (FA) and missed detection (MD) probabilities. By determining the optimal detection threshold that maximizes the COP, we characterize the success probability for the legitimate transmission, highlighting the trade-off between covertness and transmission success. Our numerical results confirm that while deploying FAS at the warden enhances its detection ability compared to fixed-position antennas (FPAs), equipping the receiver with FAS rather than FPAs significantly improves reception quality, leading to more reliable transmission.