Power Boosting Based User Pairing in NOMA Systems

Non orthogonal multiple access (NOMA) is a potential solution for communication systems with massive connection requirement. It enables multiple users to share the same time-frequency resource block through user pairing, so as to improve the spectrum efficiency of the system. However, the advantage of NOMA can only be fully utilized when the difference of user channels are quite large, while it is rarely achieved when the user channels are similar due to the poor performance of successive interference cancellation (SIC) receiver. In this paper, a user pairing scheme based on power boosting is proposed for NOMA systems, which enables users with similar channel gains to get paired and obtain NOMA advantage. In addition to a feasibility analysis on promoting more paired users by increasing certain power, the relationship between the required power boosting and channel difference is also derived. Simulation results demonstrate that, compared with the hybrid transmission of NOMA and orthogonal multiple access (OMA), our proposed scheme can significantly improve the spectrum efficiency with little power efficiency degradation.