Two Stage Relay Selection for Enhancing Physical Layer Security in Non Orthogonal Multiple Access
In this paper, we examine the physical layer security of a cooperative relay network where two source destination pairs communicate through a decode and forward (DF) relay in the presence of multiple eavesdroppers. To safeguard the legitimate communications against eavesdropping, we propose a novel two stage secure relay selection (TSSRS) with a non orthogonal multiple access (NOMA) scheme to maximize the capacity of one source destination pair, while guaranteeing the successful communication of the other source destination pair. To explicitly reveal the benefits of our proposed scheme, we derive the exact and asymptotic expressions for its secrecy outage probability. As a benchmark, we also analyze the secrecy performance of the TSSRS strategy with an orthogonal multiple access (OMA) scheme. Both theoretical analysis and simulation results demonstrate that our proposed TSSRS NOMA scheme significantly outperforms the TSSRS OMA scheme when the transmit power at the source and relay is in the low and medium regimes. In addition, we show that the advantage of the TSSRS NOMA scheme over the TSSRS OMA scheme becomes obvious when the two source destination pairs have profoundly different secrecy requirements.
IEEE Transactions on Information Forensics and Security