Research On User Grouping Algorithms And Power Control Strategies Of NOMA System

Supporting massive user connection is a key issue in 5G and 6G research.It is important to introduce more efficient multiple access technologies to deal with this issue.Non-orthogonal Multiple Access(NOMA)technology is one of the key technologies in 5G and 6G communication systems since it can support overload transmission with limited resources and significantly improve spectrum efficiency.In the NOMA system,resource allocation is one of the key issues affecting system performance,including user grouping and power control,which is a complex mixed integer programming problem.However,the existing user grouping algorithms and power control strategies have high computational complexity,ignore user fairness,and fail to perform Successive Interference Cancellation(SIC)at the receiver.To mitigate those problems,considering reducing the complexity,improving user fairness,ensuring perfect SIC at the receiver and impact of imperfect SIC,this paper proposes three corresponding resource management strategies.The main works of this paper is as follows:(1)To solve high complexity,ignoring user fairness,and failing to perform SIC issue in the resource management algorithm,a user grouping algorithm and power control strategy of downlink NOMA system with perfect SIC are proposed.Considering user fairness,a user carrier dynamic matching algorithm based on the Jain fairness index is proposed,and a power control strategy is given to ensure perfect SIC.At the same time,the proposed resource management strategy reduces the complexity of the algorithm through decoupling technology.The simulation results show that the proposed scheme has better performance than the Orthogonal Multiple Access(OMA)scheme,near far matching algorithm and distributed matching algorithm in terms of user fairness,spectrum efficiency and energy efficiency.(2)To solve NOMA system performance degradation caused by the failure of the receiver to perform SIC,a user grouping algorithm and a power allocation strategy of the downlink NOMA system with imperfect SIC are proposed.The distributed hybrid multiple access user grouping algorithm with imperfect SIC is studied.Moreover,according to the KKT condition,the optimal power allocation is theoretically derived,and an optimum power allocation strategy is given.The simulation results show that the proposed resource management algorithm improves the spectral efficiency of the system and ensures user fairness.(3)To solve the problem that the receiver fails to perform SIC due to the unevenly distributed users,a user grouping algorithm of the uplink NOMA system with imperfect SIC is proposed.Different from the existing grouping algorithm in which users are paired in pairs,the users in the center of the cell are divided into different groups,and these users are matched with the users at the edge of the cell in groups.After the matching is completed,Time division multiple access NOMA protocol is used to communicate with the base station,and the edge user occupies the entire communication time slot,which improves the communication rate of the edge user.In addition,the proposed hybrid multiple access grouping scheme avoids directly pairing users with similar channel gains,thereby greatly improving the probability of successful SIC execution at the receiver.The simulation results unveil the effectiveness of the proposed grouping algorithm.