A Non-orthogonal Multiple Access and Interference Mitigation Combined Strategy in Multi-user Networks

In contrast to the orthogonal multiple access (OMA), non-orthogonal multiple access (NOMA) was shown to have outstanding performance in terms of spectrum efficiency, user fairness and signalling cost. In order to further promote the QoS of NOMA, an interference alignment and NOMA (IA-NOMA) combined strategy was proposed and analysed in this paper. In the two-user model, the proposed IA-NOMA showed significant performance improvements in terms of bit error rate. By considering a more generalised scenario, the idea of IA-NOMA was extended from the two-user model to a massive-user network. In this context, a cluster based IA-NOMA (CIA-NOMA) algorithm was proposed, and the sum-rate and outage probability of the CIA-NOMA was derived. The QoS of CIA-NOMA in terms of outage probability and effective data rate were demonstrated under different target rates. For the results of outage probability, it was shown that the CIA-NOMA outperformed NOMA-only method, especially under a low target rate case. Correspondingly, in terms of effective capacity, the CIA-NOMA required less transmit power than the NOMA-only method to achieve a target data rate.