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arXiv · 2609.34668

Covert Communications over Enormous Fluid Antenna Systems (E-FAS): Impact of Channel Hardening on Detection

Farshad Rostami Ghadi·Damoon Shahbaztabar·Kai-Kit Wong·Wei-Ping Zhu
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Abstract

Enormous fluid antenna systems (E-FAS) enable guided surface wave (SW) propagation and induce an end-to-end channel that is conditionally complex Gaussian with a random covariance scale. This paper investigates the impact of this channel structure on covert communication in the presence of a passive warden. Under an equal power effective mode representation, the random channel scale follows a Gamma distribution, leading to a Bessel-K distribution for the effective channel power. We show that the optimal likelihood ratio test at the warden reduces to an energy detector and derive the corresponding false alarm and missed detection probabilities. These results are then used to characterize the achievable covert throughput under a prescribed detection error constraint. Numerical results show that, for finite observation intervals, finite mode E-FAS channels improve covertness relative to the fully hardened Rayleigh limit with the same average channel power. They further reveal an asymmetric role of channel hardening: stronger hardening can improve the legitimate link, whereas retaining channel scale fluctuations at the warden can enhance finite observation covertness.

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Farshad Rostami Ghadi, Damoon Shahbaztabar, Kai-Kit Wong, Wei-Ping Zhu. 2026-09-28. Covert Communications over Enormous Fluid Antenna Systems (E-FAS): Impact of Channel Hardening on Detection. https://arxiv.org/abs/2609.34668

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