Secrecy performance analysis of QoS-based non-orthogonal multiple access networks over Nakagami-m fading

In this paper, we consider the physical layer security of a downlink non-orthogonal multiple access (NOMA) system, in which users' quality of service (QoS) requirements are investigated to perform NOMA and all channels are assumed to follow Nakagami-m fading. Specifically, we investigate the scenario that a source transmits information to two legitimate users (LUs) using NOMA scheme in the presence of a passive eavesdropper, where each LU has the different priority based on its QoS requirements. In order to characterize the secrecy performance, the new closed-form expression of overall secrecy outage probability is derived. Finally, our theoretical analyses validated by Monte-Carlo simulation show that in QoS-based NOMA system, the better secrecy performance of overall communication process can be obtained in case that there is not much difference in the level of priority between LUs.