Code domain non orthogonal multiple access schemes for 5G and beyond communication networks: A review

Future communication networks may encounter various issues in order to facilitate heavy heterogeneous data traffic and large number of users; therefore, more advanced multiple access (MA) schemes are being developed to meet the changing requirements. The research space on making more robust MA scheme is continuously increasing, so it becomes significant to analyze the various schemes to determine the appropriate MA scheme for 5G networks. Therefore, in this paper, the comprehensive overview of the most popular and recent MA schemes is presented for 5G networks. This paper mainly classifies the MA techniques in orthogonal MA (OMA) and various types of non-OMA (NOMA) techniques. Specifically, we introduce the rate splitting multiple access (RSMA) and interleave division multiple access (IDMA). Further, close attention is paid to NOMA family, including code-domain NOMA (e.g., sparse code multiple access (SCMA)) and power-domain NOMA. Above all, from this exploration, the opportunities and challenges could be notified in MA schemes, and further, the optimum MA technique can be pointed out among the discussed MA schemes for 5G and beyond communication networks.