Abstract
In this paper, we investigate the secrecy outage performance of a typical cooperative downlink non-orthogonal multiple access (NOMA) system over Nakagami-m fading channel, in which the base station transmits a superimposed signal to two users via a relay. First, the secrecy outage behavior of the considered system over Nakagami-$m$ fading channel under three wiretapping cases, e.g., one eavesdropper (Eve), non-colluding and colluding eavesdroppers, are studied, and both analytical and asymptotic expressions for the secrecy outage probability are derived. Next, by considering the availability of Eves' channel state information, we adopt the two-stage relay selection (RS) strategy to improve the system's secrecy outage performance. Finally, simulation results are provided to corroborate the accuracy of our derived expressions. The results show that: 1) there exists secrecy performance floor for cooperative NOMA system, and it was determined by the weak user's secrecy requirement and the channel conditions of the Eves; 2) the two-stage RS scheme can increase the secrecy outage performance significantly under three wiretapping cases; 3) the secrecy performance of cooperative NOMA network is superior to that of orthogonal multiple access network on the condition of low and medium signal-to-noise ratio regions.
Highlights
With the rapid growth of the demand for wireless communications, non-orthogonal multiple access (NOMA) has been recognized as a potential multiple access technique in the fifth generation (5G) wireless networks due to its band-efficient [1]–[3]
We can see that the secrecy outage probability (SOP) are saturated in the high signal-to-noise ratio (SNR) region, and the performance floors were determined by the target secrecy rate of the legitimate user D1 and the SNR at the Eve
The effective relay selection (RS) scheme is considered to enhance the secrecy performance of the system. Both the analytical and asymptotic expressions of SOPs for each wiretapping case are obtained in closed-form
Summary
With the rapid growth of the demand for wireless communications, non-orthogonal multiple access (NOMA) has been recognized as a potential multiple access technique in the fifth generation (5G) wireless networks due to its band-efficient [1]–[3]. The work in [10] has proposed a more effective relay selection (RS) scheme to improve the outage probability for cooperative NOMA The aim of this RS strategy is to maximize the strong user’s channel capacity under the condition that the poor user could satisfy its quality of service (QoS). In [18], secrecy outage performance and achievable secrecy rate were analyzed for a vehicular relay network by exploiting cooperative jamming and superposition coding schemes. The authors of [26] analyzed the impact of TAS scheme over Nakagami-m fading channel, while the case that the near user should satisfy both the secrecy and QoS requirements was considered. We provide a thorough study for the secrecy outage performance of cooperative NOMA system over Nakagami-m fading. This classification is practical, since some users in the network need quickly connected to receive some critical control message while other users could be served in an opportunistic manner for its purpose of high data rate download requirement
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
