Probabilistic Accumulate-then-Transmit in Covert Communications with Energy Harvesting

In this paper, we investigate a wireless-powered covert communication (WP-CC) system, where 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. A probabilistic accumulate-then-transmit (ATT) protocol, where the transmitter sends its information with a prior probability p conditioned on the available energy being sufficient, is proposed to maximize the communication covertness subject to a requirement on the communication quality. In order to facilitate the optimal design of the prior probability p and the information transmit power in the considered 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. Our examination shows that the proposed probabilistic ATT protocol can achieve higher communication covertness than the traditional ATT protocol with p = 1.