Toward Covert Communications via a Wireless-Powered Jammer Fueled by a Receiver

In this letter, we investigate a covert communication system with a wireless-powered jammer, where the jammer firstly harvests energy from a receiver and then generates artificial noise (AN) to confuse the detection at a warden on the communication activity. To evaluate the communication covertness and quality, we analytically derive the sum of error probabilities and the effective covert rate. Then, we jointly optimize the time switching ratio at the wireless-powered jammer and the transmit power at the receiver to maximize the effective covert rate, which can be further improved by increasing the maximum transmit power at the receiver, loosing the covertness constraint, or adjusting cooperatively the information transmit power. Moreover, our proposed scheme with the adaptive time switching ratio at a wireless-powered jammer achieves a higher effective covert rate than the scheme with a fixed time switching ratio and the conventional scheme with a cable-powered jammer, which demonstrates the benefit of introducing the adaptive time switching ratio into the wireless-powered jammer.