Secrecy at Physical Layer in NOMA with Cooperative Jamming

We have proposed and analyzed secrecy performance of a network architecture which contains a source, two destinations, a friendly jammer (FJ) and an eavesdropper (Eve). To jam the Eve in order to secure the confidential information of both users, the FJ sends a jamming signal while the source sends the combined information signal using non-orthogonal multiple access (NOMA) technique to both the users. A known jamming is considered which is known by both the users. Both the users subtract the known jamming from the received signal and then decode the information signal as per the NOMA technique. We analyzed the physical layer security of the network in terms of the secrecy outage probability (SOP) where the two users have different target secrecy rates. A closed form expression of the SOP is developed. We have analyzed the SOP under the impact of several numerical parameters such as: source transmit signal to noise ratio (SNR), FJ transmit SNR, fraction of source transmit power, and different target secrecy rates. For a fixed transmit SNR of the FJ, we obtain an optimal value of the source transmit SNR at which SOP is minimized These analyzed results are also supported by the MATLAB based simulation results.