Research On User Scheduling And Power Allocation Algorithm In Non-orthogonal Multiple Access System

The popularity of wireless terminals and the rapid growth of data traffic have brought unprecedented challenges to existing communication technologies,and the current orthogonal multiple access(OMA)technology can not meet the rapid growth of network capacity.Therefore,multiple access technology needs to introduce new dimensions to relieve the pressure of network capacity.By introducing Non-orthogonal multiple access(NOMA)technology in power domain,the network capacity can be effectively improved.This thesis focuses on the resource allocation scheme of user scheduling and power allocation in NOMA heterogeneous networks.First,describe the advantages of NOMA technology by comparing the characteristics of existing OMA Technology.According to the application scenario of NOMA technology,the basic principle is analyzed.In addition,the successive interference cancellation(SIC)technology and the existing methods of subchannel matching and power allocation are introduced.Secondly,the resource allocation problem of maximizing system throughput in NOMA Het Nets is addressed.The first research content of this thesis is to solve the problem of maximizing the balance between the total system data rate and the number of users by combining subchannel matching and power allocation.To solve this problem,this thesis proposes a user subchannel two-side matching scheme based on matching theory.Under the condition of satisfying the user's minimum data rate requirement and knowing the perfect channel state information(CSI),the scheme establishes the model of maximizing the total throughput of the system by combining user scheduling and power allocation in the NOMA Het Nets.For the user scheduling problem,users and subchannels are considered as two independent sets to pursue their own maximum profit,and the suboptimal solution of the user scheduling problem is obtained by using the matching theory.According to the given subchannel matching scheme,water filling algorithm is used to solve the power allocation problem of users.The simulation results show that the proposed scheme can approach the upper bound and is superior to the existing user grouping algorithm and orthogonal frequency division multiple access(OFDMA)scheme.Finally,the resource allocation problem of maximizing system energy efficiency in NOMA Het Nets is addressed.The second research content of this thesis is to combine user scheduling and power allocation to solve the problem of maximizing the total energy efficiency of the system.To solve this problem,an energy efficiency system model of joint user scheduling,optimal power allocation factor among users in subchannels and power allocation across subchannels is established.Since the problem of formulation is a multiobjective optimization(MOO)problem and has two properties of non-convex and NP hard,this thesis decouples the multi-objective optimization problem into two single objective optimization(SOO)problems:(1)the optimal power allocation factor of maximizing the energy efficiency among users in subchannels solves the subchannel allocation problem;(2)the power allocation problem across subchannels.In the subchannel allocation scheme,this thesis use the non-cooperative game to solve the problem of power allocation factor among users in subchannels and the global optimal search to solve the problem of usersubchannel association.For the problem of power allocation factor among users in subchannels,this thesis introduce the super-modular game to discuss the existence of the Nash equilibrium(NE)and design an algorithm to make it converge to the Nash equilibrium point(NEP).According to the correlation between users and subchannels,this thesis proposes a user-subchannel global optimal search and matching scheme based on noncooperative game.According to the given subchannel allocation scheme,the method of successive convex approximation(SCA)is used to transform the power allocation problem across subchannels into a convex problem and solve it by iteration.The simulation results show that the energy efficiency of the proposed scheme is better than that of OFDMA system and fractional transmit power allocation(FTPA)algorithm with the same subchannel matching scheme.