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

• Published in: IEEE transactions on wireless communications Vol. 21; no. 12; pp. 10393 - 10406
• Main Authors: Wang, Yida, Yan, Shihao, Yang, Weiwei, Zhong, Caijun, Ng, Derrick Wing Kwan
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: artificial noise; Communication; Communications systems; Conditional probability; Covert communications; Design optimization; Error detection; Interference cancellation; Internet of Things; Optimization; Protocols; Receivers; Sensor systems; Sensors; Statistical analysis; transmit probability; Transmitters; Upper bounds; Wireless communication; Wireless communications; wireless-powered communications
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2022.3183892

In this paper, we investigate the optimal design of 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. In order to achieve a higher level of covertness, we propose a probabilistic accumulate-then-transmit (ATT) protocol, where the transmitter is able to adjust the prior probability conditioned on the available energy being sufficient, i.e., <inline-formula> <tex-math notation="LaTeX">p </tex-math></inline-formula>, rather than setting <inline-formula> <tex-math notation="LaTeX">p=1 </tex-math></inline-formula> as in the traditional ATT protocol to maximize the system throughput. Then, we 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 <inline-formula> <tex-math notation="LaTeX">p </tex-math></inline-formula> and the information transmit power to maximize the communication covertness subject to a quality-of-service (QoS) requirement on communication. 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 <inline-formula> <tex-math notation="LaTeX">p </tex-math></inline-formula>) can achieve the covertness upper bound determined by the CP-CC system, while the traditional ATT protocol (with <inline-formula> <tex-math notation="LaTeX">p=1 </tex-math></inline-formula>) cannot, which confirms the benefits brought by the proposed probabilistic ATT protocol in covert communications.