User pairing schemes based on channel quality indicator for uplink non-orthogonal multiple access

Non-orthogonal multiple access (NOMA) acquires capacity improvement by utilizing channel gain difference between paired users. Multiple users are multiplexed into power domain with same frequency, time, as well as spreading code therefore capacity improvement can be obtained. In NOMA system, user pairing scheme plays important role because of high association with inter-set interference and capacity improvement. Thus, we propose user pairing schemes based on Channel Quality Indicator (CQI) for sum capacity maximization over Uplink (UL) NOMA system. We also propose hybrid CQI scheme, hence interset interference toward last sequences CQI indexes of strong set users can be reduced while the extreme poor level of CQI users also can be handled in the same time. For result, we provide mathematical analysis of our proposed uplink (UL) NOMA system with two paired user for both perfect and imperfect SIC. Then, the cell capacities of proposed user pairing schemes under perfect SIC as well as imperfect SIC are analyzed and compared with orthogonal multiple access (OMA). Finally, data rate as well as inter-set interference impact of proposed user pairing schemes in strong set users are also evaluated.