On non-zero secrecy capacity and outage probability of cognitive radio networks

In this paper, we consider a spectrum sharing cognitive radio network (CRN) in the presence of an eavesdropper (EAV) who illegally listens to the primary user (PU) communication. Under the PU outage and the secondary user (SU) peak transmit power constraints, the adaptive transmit power policy of the SU transmitter (SU-Tx) is obtained. Then, expressions for the probability of existence of a non-zero secrecy capacity of the primary network and the outage probability of the secondary network are derived. Numerical results are provided to investigate the impact of the SU-Tx peak transmit power, PU average transmit power and channel mean powers among users on the outage probability and probability of existence of a non-zero secrecy capacity. Our results illustrate that the probability of existence of a non-zero secrecy capacity strongly depends on the channel conditions among users and SU-Tx adaptive transmit power policy.