Cooperative multiple access cognitive radio transmission with renewable energy sources

In this paper, cooperative cognitive multiple access schemes with harvesting capability are considered for improving the energy efficiency and spectrum utilization. We consider three scenarios, namely, orthogonal multiple access (OMA), time variable-OMA (OMA-α) and power-domain non-orthogonal multiple access (PD-NOMA), and compare their performance. There exists a secondary network underlying the primary network helps as relay to improve the performance of primary network and gain the opportunity of transmission of own data. Our objective is to maximize the energy efficiency while a minimum transmission data rate for primary network, energy usage causality, and the battery overflow constraints should be satisfied. The proposed problems are highly non-convex, and therefor, we exploit Dinkelbach’s Algorithm and successive convex approximation (SCA) method to overcome this bottleneck. The simulation results reveal that the performance of PD-NOMA scheme in some simulation is approximately up to 66% and 25% better than the performance of OMA-α and OMA, respectively, in the same environment.