Outage Performance Analysis of STAR-RIS Assisted CR-NOMA Networks

To achieve low-cost, low energy consumption green Internet of Things (IoT) communication and meet 360 ^o area full-coverage, we propose a novel simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted cognitive radio (CR)-non-orthogonal multiple access (NOMA) network. Specifically, the secondary transmitter serves as a relay of the primary network to forward the messages, and the secondary transmitter communicates with the user with the assistance of the STAR-RIS. To evaluate the performance of the considered network, we derive the outage probability (OP) for the users under the Nakagami-m fading channels. In addition, the asymptotic behavior at high signal-to-noise ratio (SNR) regions is analyzed. The following meaningful insights are obtained from the simulation experiments: 1) The OPs of users decrease continuously with the transmit power P s , and increasing P s at high SNR is no longer effective for system reliability; 2) The increase in the components number of STAR-RIS has a positive impact on the reliability for the STAR-RIS assisted overlay CR-NOMA network and saturates after a certain value; 3) The scheme we considered has superior reliable performance by comparing with orthogonal multiple access.