An examination of outage performance for selected relay and fixed relay in cognitive radio-aided NOMA

Abstract

In this paper, we consider impacts of relay selection scheme on primary network performance in cognitive radio (CR) assisted non-orthogonal multiple access (NOMA). We suggest relay selection model to improve the outage performance at primary network. In this model, the fixed power allocation in NOMA is deployed to achieve considered simulation results. To completely study the profits of the NOMA scheme, we derive closed-form formula for the outage probability. We find that the CR-NOMA enhances its performance as suitable selection of relay intending to forward signal to NOMA users. It is shown several performance comparison in such CR-NOMA as varying the target rates at relay and destination. Numerical results are extensively studied to confirm that our proposed CR-NOMA outperforms the other designs in terms of outage probability.