Comprehensive Study of NOMA Schemes.

Non-orthogonal multiple access (NOMA) is an efficient method for radio resource sharing and has been identified as a promising technology in the fifth generation (5G) wireless networks to meet the requirement of system capacity, user connectivity and service latency. Various NOMA schemes have been proposed in the last few years, such as transmitter transparent NOMA, linear spreading based NOMA and sparse code based NOMA at transmitter side, as well as linear minimum mean square error (LMMSE), expectation propagation algorithm (EPA) and message passing algorithm (MPA) at receiver side. This article provides a systematic overview of the state-of-art design of the NOMA transmission based on a unified transmitter and receiver design framework, followed by comprehensive link level evaluations in various aspects to provide quantitative understanding of the relative performance of the various kinds of NOMA transmitter and receiver design.