Utilizing Cooperative Jamming to Secure Cognitive Radio NOMA Networks

In this paper, we propose an innovative framework to improve the physical layer security of cognitive radio nonorthogonal multiple access (CR-NOMA) networks. Specifically, we consider a cooperative spectrum-sharing mechanism, where a cognitive transmitter serves as a relay and assists primary/cognitive transmissions using the NOMA principle in the presence of a passive eavesdropper. Technically, we propose a new cooperative jamming scheme, where the primary/cognitive receivers and the primary transmitter are recruited as jammers to transmit artificial noise in order to intentionally confuse eavesdropper. Under a practical assumption that only the statistical channel state information of eavesdropper is available, the secrecy outage probability (SOP) is used as the performance metric. An optimization problem of maximizing the minimum confidential information rate among the primary and cognitive receivers is formulated. We devise a successive convex approximation based power allocation algorithm to efficiently solve the non-convex optimization problem. Our simulation results indicate that the proposed scheme outperforms the orthogonal multiple access based schemes in terms of minimum confidential information rate.