A Survey on Non-orthogonal Multiple Access Schemes

In this paper, we make a survey on non-orthogonal multiple access (NOMA) schemes, which could be a promising candidate as a downlink wireless access scheme for future 5G radio access technology. To enhance the spectrum efficiency, NOMA adopts a successive interference cancellation (SIC) receiver as the baseline receiver scheme for robust multiple access. In order to get a better tradeoff between the system spectrum efficiency measured by the total user throughput and the user fairness measured by celledge user throughput, fractional frequency (FFR) and resource management schemes have been applied to NOMA with SIC. Furthermore, multi-antenna/site technologies with a proposed NOMA/MIMO scheme using SIC and an interference rejection combing (IRC) receiver to get a further user capacity is discussed in some related papers. Finally, it is shown that even in relay channel, NOMA is still effective for system throughput enhancement.