A Survey of Non-Orthogonal Multiple Access for 5G

Compared to the traditional orthogonal multiple access (MA), non-orthogonal multiple access (NOMA) technology can achieve higher capacity gain and higher spectrum efficiency, support larger massive connectivity. In this article, according to signal transmission characteristic, the NOMA schemes are classified into four categories: scrambling based NOMA, interleaving based NOMA, spreading based NOMA and coding based NOMA. Furthermore, the process and characteristics of different schemes are summarized. The performance of the NOMA schemes is evaluated. According to the evaluation results, the scheme with superior performance is given. By analyzing and comparing features of these technologies, a research guiding is given for future 5G multiple access.