Non-Orthogonal Multiple Access: A Constellation Domain Multiplexing Approach

In this paper, a novel constellation domain non-orthogonal multiple access (Con-NOMA) system using signal-space diversity technique is proposed for the downlink network. More specifically, users will be multiplexed in the in-phase and quadrature part of the rotated constellation points of M-ary phase-shift keying/quadrature amplitude modulation symbol. The proposed Con-NOMA is capable of bypassing the requirement of successive interference cancellation, joint detection, uneven power assignment, etc., which are required in the power domain NOMA (PD-NOMA). Further investigation shows that the Con-NOMA is superior to PD-NOMA in terms of the achievable data rate for each user as well as the sum-rate of the overall system. The proposed Con-NOMA is then examined under Nakagami-m fading channel by evaluating the closed-form expression of the average symbol error rate (ASER) for each user. After comparison, it is concluded that the error performance of each user in the proposed Con-NOMA system is much better than in the PD-NOMA system.