Performance Analysis of CR-NOMA Based on Untrusted Relay in IoT

Cognitive radio (CR) technology can be used as a key technology for wireless communication to integrate heterogeneous networks, increasing channel capacity and improving spectrum efficiency because secondary users can access to the spectrum of the primary network for communication without authorization. It can, to some extent, pose communication security issues. To address this issue, a system model combining CR network with non-orthogonal multiple access (CR-NOMA) is proposed, in which secondary users are utilized to support the primary network communication while cognitive users are untrusted. To begin, the proposed system CR-NOMA model is constructed in the Internet of Things to guarantee that it is compatible with a wider range of scenarios. Secondly, physical layer security technologies such as redundant information and jamming signal are used to improve the secrecy performance. Finally, the closed-form results for the exact and asymptotic outage probabilities of the near-end user and the remote user are studied, taking information secrecy into account. The secrecy throughput performance of various users is examined. The simulation results demonstrate that using cognitive users as relays to forward information can significantly improve the performance of the proposed system. The performance of the remote user, in particular, demonstrates that the considered model may effectively improve the quality of service of the cellular-edge user and therefore expand the coverage of the base station.