Secure Transmission for NOMA-Based Cognitive Radio Networks With Imperfect CSI

This letter studies the secure transmission issue of non-orthogonal multiple access (NOMA) based cognitive radio networks (CRNs) with imperfect channel state information (CSI), where the secondary user (SU) transmitter aims to transmit the normalized messages to two receivers ${U_{a}}$ and ${U_{b}}$ , and concurrently ${U_{b}}$ with full-duplex (FD) ability implements jamming to confuse the eavesdropping of the illegal user while causing zero interference to the primary user and ${U_{a}}$ . Under this setup, the novel exact closed-form expressions of connection outage probability (COP), secrecy outage probability (SOP) and effective secrecy throughput (EST) for each SU receiver under Rayleigh fading channels are derived. Simulation results are presented to demonstrate that: 1) the proposed scheme can achieve pretty good security and reliability performance, but there exist trade-off between such two indicators; 2) the FD-NOMA operation performs better than the half-duplex (HD) NOMA and HD orthogonal multiple access (OMA) in term of EST.