Secure NOMA Based Cooperative Networks with Rate-Splitting Source and Full-Duplex Relay

In this paper, we develop a non-orthogonal multiple access (NOMA)-based cooperative network against multiple eavesdroppers, in which the source delivers confidential information using rate-splitting approach to the destination under the help/protection of the full-duplex relay. Specifically, by splitting the symbol into two sub-symbols at the source, the channel gain differences created by the relay can be exploited between two sub-symbols to use spectral resource more efficiently with NOMA proposal. On the other hand, by enabling the full-duplex technique in the first phase, the relay not only forwards the confidential information to the destination but also keeps radiating artificial noises to confuse multiple potential eavesdroppers. Different decoding schemes based on the successive interference cancellation (SIC) are proposed for the destination, relay, and eavesdroppers. Closed-form expressions of the ergodic secrecy rates are derived, which perfectly match the computer simulation results for our proposed network.