Research On New Non-orthogonal Multiple Access Technology

In recent years,with the continuous popularization of smart terminal devices,mobile data requirements have achieved rapid growth,which has brought huge challenges to wireless com-munication networks.Conventional orthogonal multiple access(OMA)system allocates or-thogonal resources to users,while the non-orthogonal multiple access(NOMA)system allows users to use non-orthogonal resources,resulting in higher spectrum utilization rate,higher data rate and more massive wireless connections.Therefore,this paper will make in-depth researches on the key technologies in the NOMA system.First of all,this paper investigates the sum rate maximization in the uplink NOMA sys-tem.Considering the two cases without or with the user quality of service(QoS)constraints,more general multi-user and multi-carrier schemes are studied.In the case without user QoS constraints,a power control algorithm based on iterative water filling is proposed.In the case with user QoS constraints,a sub-optimal iterative algorithm based on continuous convex ap-proximation is obtained.The simulation results demonstrate that the proposed power control algorithms outperform existing approaches in terms of the sum rate.Subsequently,this paper investigates the joint optimization of power control and user grouping in the uplink NOMA system.Taking sum rate maximization as the primary goal,considering user QoS constraints and uplink transmit power constraints,a low-complexity joint optimization algorithm is proposed to iteratively optimize power control and user grouping.Aiming at the problem of user grouping,three matching algorithms based on stable match-ing,swap matching and simulated annealing are proposed.The simulation results indicate that the proposed joint optimization algorithms outperform existing approaches,and the algorithm based on simulated annealing can achieve the best system performance.Finally,this paper investigates the error probability minimization in the uplink NOMA system.Considering error propagation with imperfect SIC,this paper analyzes NOMA sys-tem based on both long-packet and short-packet transmissions.The expressions of decoding error probabilities under imperfect SIC are obtained in closed-form.Then,the average error probabilities of the system are minimized by searching the power control schemes.The simula-tion results verify the accuracy of the derived expressions and the effectiveness of the proposed power control schemes.