Secrecy Performance of NOMA-Based Two-Way Communication System at Physical Layer

This paper examines physical layer security in a NOMA-based two-way wireless communication system with several decode-and-forward relays and a malicious eavesdropper. We implement a partial relay selection system to maximize the secrecy capacity of a specific user's information signal. Two hops are involved in the communication process because of the half-duplex relay cooperation. A selected relay receives information from two users. The relay strengthens the signals and broadcasts them during the second hop. Additionally, a jammer transmits a jamming signal that is known to all legitimate nodes but appears as noise with the received signals at the eavesdropper. Since legitimate user nodes are already aware of the jamming signal, channel status information, and self-information, they can decode the original information in downlink mode by self-interference and successive interference cancellation. Secrecy outage probability, intercept probability, and secrecy throughput have been investigated as metrics to analyze the security, where the secrecy performance of a particular user is found to increase by $94.66\, \%$ with an increment in transmit SNR of jamming from $60\, dB$ to $70\, dB$ and increases by $90.78\, \%$ with an increment in the number of relays from 2 to 5.