Hierarchical Symbiotic Transmission Strategy With Cooperative-NOMA for Cognitive Radio Networks

We propose a hierarchical symbiotic transmission strategy with cooperative-nonorthogonal multiple access (C-NOMA) for multi-carrier cognitive radio networks, where the mutualistic and commensualistic transmission modes are employed in the primary network (PN) and secondary network (SN), by promoting some secondary users (SUs) as relays to assist communication of both PN and SN. The proposed strategy enables higher system throughput and supports much more user connectivity than the existing schemes with C-NOMA that focused on maintaining the performance of PN. Sub-carrier assignment and power allocation solutions are presented to further improve system throughput. Simulation results demonstrate the effectiveness of the proposed strategy.