Covert Communication by Exploiting a Full-Duplex Cognitive Receiver in CR Network

Covert communications can enhance users's privacy by hiding the existence of communication. In this paper, we analyze a covert cooperative cognitive radio (CCCR) networks, where a primary transmitter (PT) transmits information with the aid of one secondary transmitter (ST). In return, ST attempts to transmit private information by exploiting PT's spectrum in presence of an eavesdropper (Eve). Specifically, a full-duplex secondary receiver (SR) sends jamming signals to the Eve to cause uncertainty by varying the jamming power. Then, the closed-form expression of the minimal detection error probability at Eve, the approximate expression for the optimal transmit power as well as the corresponding covert rate can be obtained under the given constraint. Numerical results show that the jamming signals and noise uncertainty have a significant influence on Eve's minimum detection error probability. Moreover, it can be seen that under the same covert constraints, the joint impact of noise uncertainty and jamming power on Eve's detection error probability, covert rate and covert outage probability (COP) is remarkable when noise uncertainty is large or the self-interference cancellation coefficient is small.