Probabilistic Accumulate-then-Transmit in Wireless-Powered Covert Communications

TL;DR

This paper proposes a probabilistic accumulate-then-transmit protocol for wireless-powered covert communication systems, enhancing covertness and optimizing system parameters through analytical derivations and simulations.

Contribution

It introduces a novel probabilistic ATT protocol that outperforms traditional methods, with analytical tools for joint optimization of transmission probability and power.

Findings

Probabilistic ATT achieves higher covertness than traditional ATT.

Analytical expressions for warden's detection error probability and covert rate.

Simulation confirms probabilistic ATT reaches covertness bounds.

Abstract

In this paper, we investigate the optimal design of a wireless-powered covert communication (WP-CC) system, in which a probabilistic accumulate-then-transmit (ATT) protocol is proposed to maximize the communication covertness subject to a quality-of-service (QoS) requirement on communication. Specifically, in the considered WP-CC system, a full-duplex (FD) receiver transmits artificial noise (AN) to simultaneously charge an energy-constrained transmitter and to confuse a warden's detection on the transmitter's communication activity. With the probabilistic ATT protocol, the transmitter sends its information with a prior probability, i.e., $p$, conditioned on the available energy being sufficient. Our analysis shows that the probabilistic ATT protocol can achieve higher covertness than the traditional ATT protocol with $p=1$. In order to facilitate the optimal design of the WP-CC system, we also derive the warden's minimum detection error probability and characterize the effective covert rate from the transmitter to the receiver to quantify the communication covertness and quality, respectively. The derived analytical results facilitate the joint optimization of the probability $p$ and the information transmit power. We further present the optimal design of a cable-powered covert communication (CP-CC) system as a benchmark for comparison. Our simulation shows that the proposed probabilistic ATT protocol (with a varying $p$) can achieve the covertness upper bound determined by the CP-CC system, while the traditional ATT protocol (with $p=1$) cannot, which again confirms the benefits brought by the proposed probabilistic ATT in covert communications.