A Fair Individual Rate Comparison between MIMO-NOMA and MIMO-OMA

In this paper, the individual rates achieved by multiple-input, multiple-output (MIMO) non-orthogonal multiple access (NOMA) and MIMO orthogonal multiple access (OMA) are compared when users are paired into clusters. A power allocation (PA) strategy is proposed, which ensures that MIMO-NOMA achieves a higher individual rate for each user than MIMO-OMA with arbitrary PA and an optimal degrees-of-freedom split. In addition, a special case with equal degrees-of- freedom and arbitrary PA for OMA is considered, for which the individual rate superiority of NOMA still holds. Moreover, it is shown that NOMA can attain better fairness through appropriate PA. Finally, simulations are carried out to validate the developed analytical results.