A streamlined user grouping in downlink NOMA systems

Reducing SIC operations and interference while maintaining the same radio resources for users in a cluster is a potential research direction in non-orthogonal multiple access (NOMA) systems. In order to reach this goal, a streamlined user grouping is proposed for a four-user cluster in downlink NOMA systems, which is carried out based on the in-phase and quadrature components of a constellation. In terms of bit error rate performance, the proposed scheme is superior in comparison with the conventional NOMA without user grouping and phase rotation-based user grouping. This improvement is achieved in light of the three positive points of pulse amplitude modulation, the Gray mapping rule, and the joint maximum-likelihood detector. We have come up with a streamlined user grouping scheme for a four-user cluster in downlink NOMA systems. This proposed scheme is designed based on PAM modulation, the Gray mapping rule, and the joint maximum-likelihood detector. The streamlined user grouping gives outstanding BER performance in comparison to the conventional NOMA without user grouping and phase rotation-based user grouping.image