Research On Low Complexity Resource Allocation Scheme For Millimeter Wave NOMA System

Existing spectrum resources are increasingly scarce and cannot meet people’s needs for high-speed communication,so it is particularly important to study key technologies that can effectively improve spectrum efficiency.Millimeter wave communication technology can efficiently utilize many unused frequency bands to further meet the needs of future users.In additional,the core idea of power domain non-orthogonal multiple access is to multiplex spectrum resources,which can serve multiple users for simultaneous communication on the same resource block,thereby increasing the users access numbers.Integrating the advantages of power domain NOMA technology,millimeter wave communication can effectively improve the system spectrum efficiency and access numbers.However,with the high demand of users and the increasing number of base station antennas,the wireless resources of millimeter-wave NOMA systems based on lens large-scale antenna arrays will become relatively limited,and there are problems of high complexity and energy consumption.Therefore,this paper studies the low-complexity resource allocation scheme of the millimeter wave NOMA system under the condition of limited resources.The specific research work is as follow:(1)When users in a single cell are randomly distributed,since the traditional millimeter wave system requires each antenna to correspond to an independent radio frequency link,the hardware cost is too high,and the system performance is difficult to effectively improve,so consider combining NOMA technology,which can access more users and reduce the number of RF links without being subjected to the constraint that the RF links numbers equal to the user numbers.Therefore,in the millimeter wave NOMA system under the beam space,a beam selection and power allocation scheme combined with user grouping is designed.In order to reduce the interference between users and improve the rate performance,the scheme selects beams uniformly by grouping users,and allocates power to users within the beam in combination with a low-complexity power allocation scheme.The simulation results show that the proposed scheme can effectively improve the spectral efficiency and energy efficiency performance of the system.(2)When users follow the spatial cluster distribution in a single cell,because the combination of the beam spatial MIMO system and the power domain NOMA technology requires the joint design of beam selection and the interference cancellaiton,aiming at the problem that the maximization of the system sum rate cannot be solved directly,a joint optimization scheme based on beam selection and interference cancellation is proposed to solve it.In the stage of inter-cluster interference cancellation,based on the signal power loss analysis of directional deviation,a beam selection algorithm based on K-means is designed.In this algorithm,the cluster center user can be selected through the K-means algorithm,and is used to design beam selection and digital precoding vector.In the stage of intra-cluster interference cancellation,based on the results of beam selection and the determination of the optimal decoding order,a power allocation based on the bisection method is designed to guarantee the fairness of users in each cluster.The simulation verifies that,the proposed scheme has significant performance improvement in terms of achievable sum rate and energy efficiency,and has the advantage of low complexity,which is suitable for the large-scale user scenario.