Covert Communication in Fading Channels under Channel Uncertainty

TL;DR

This paper analyzes covert communication in fading channels with uncertain channel knowledge, deriving detection thresholds and achievable rates while considering covertness and outage constraints.

Contribution

It provides an exact expression for the warden's optimal detection threshold and analyzes achievable rates under channel uncertainty and covertness constraints.

Findings

Detection threshold depends on channel uncertainty.

Achievable covert rates decrease with higher uncertainty.

Performance is sensitive to covertness level and outage constraints.

Abstract

A covert communication system under block fading channels is considered where users experience uncertainty about their channel knowledge. The transmitter seeks to hide the covert communication to a private user by exploiting a legitimate public communication link while the warden tries to detect this covert communication by using a radiometer. We derive the exact expression for the radiometers optimal threshold which determines the performance limit of the wardens detector. Furthermore for given transmission outage constraints the achievable rates for legitimate and covert users are analyzed while maintaining a specific level of covertness. Our numerical results illustrate how the achievable performance is affected by the channel uncertainty and required level of covertness.