Covert Communications over Enormous Fluid Antenna Systems (E-FAS): Impact of Channel Hardening on Detection
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.
Related
- Antenna Coding by Pixel Antennas: Unlocking A New Dimension for Wireless Communications
- Pinching Antenna and Relay Assisted Joint Indoor Outdoor NOMA Communications with SWIPT
- Dissipative Systems Analysis and Control. Theory and Applications: Erratum/Addendum. Springer Nature Switzerland AG, Communications and Control Engineering, Third uncorrected Edition, 2020
- Impact of Antenna Position Errors on TDMA and NOMA in Pinching-Antenna Systems
- Energy-Accumulate-Then-Act Backscatter Communications With Retransmission Under Imperfect Feedback Detection
BibTeX
@misc{ghadi2026covert,
title = {{Covert Communications over Enormous Fluid Antenna Systems (E-FAS): Impact of Channel Hardening on Detection}},
author = {Farshad Rostami Ghadi and Damoon Shahbaztabar and Kai-Kit Wong and Wei-Ping Zhu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34668},
eprint = {2609.34668},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34668},
}
RIS
TY - UNPB
TI - Covert Communications over Enormous Fluid Antenna Systems (E-FAS): Impact of Channel Hardening on Detection
AU - Farshad Rostami Ghadi
AU - Damoon Shahbaztabar
AU - Kai-Kit Wong
AU - Wei-Ping Zhu
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34668
UR - https://arxiv.org/abs/2609.34668
AB - 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.
ER -