A Novel Spectrum Sharing Scheme Assisted by Secondary NOMA Relay

In this letter, a two-slot secondary non-orthogonal multiple access (NOMA) relay is used to assist spectrum sharing, where the primary transceivers with long distance communicate through the relay. First, the information for the primary receiver (PR) and secondary receivers (SRs) is transmitted via the NOMA relay. Then, the information for PR is re-transmitted to it through a selected SR to improve its quality of service using maximal-ratio combining, while the next data for PR is sent from the primary transmitter to the NOMA relay simultaneously. The power allocation solution is derived for the NOMA relay. Simulation results have shown the effectiveness of the proposed scheme.