Novel opportunistic cooperative multicast scheme for NOMA

The cognitive radio technology was applied to non-orthogonal multiple access (NOMA) cooperative multicast system,the feasibility of using users as relays was studied,and a two-level cooperative transmission scheme with parameterized multicast candidate sets was proposed.Specifically,the scheme first selected the candidate set according to the cardinality q,and then selected the best forwarding node based on the channel gain between the primary users and the candidate secondary users.Simulation results show that,through the reasonable selection of the cardinality q,the proposed scheme can greatly reduce the diversity gain of the secondary users while simultaneously increasing the diversity gain of the primary users.In NOMA cooperative multicast scenario composed of N multicast users,the proposed scheme can increase the diversity gain of the primary users from 2 to min(N-q+2,q+1) to meet their reliability requirements.