Secure NOMA Based Full-Duplex Two-Way Relay Networks With Artificial Noise Against Eavesdropping

In this paper, we develop a secure non-orthogonal multiple access (NOMA)-based two-way relay network, in which two users wish to exchange their NOMA signals via a trusted relay in the presence of an eavesdropper. To ensure secure communications, the relay not only forwards confidential information to the legitimate users but also keeps emitting jamming signals all the time to confuse any potential eavesdropper. Specifically, we equip the relay and each user with the full-duplex technique in the multiple-access phase to combat the eavesdropping and improve the data transmission efficiency, respectively. Different decoding schemes based on the successive interference cancellation (SIC) are proposed for the legitimate users, relay, and eavesdropper. Closed-form expressions for the achievable ergodic secrecy rates of all data symbols are derived, validated by the excellent fitting to the computer simulation results for our proposed network.