Research On Beam Selection Scheme For Millimeter Wave Massive MIMO System

With the rapid development of the digital Internet,the existing spectrum resources are increasingly scarce and cannot meet people's needs for communication,especially the epidemic situation in early 2020.All kinds of rescue work rely on digital Internet technology,and digital Internet technology development depends on advanced communication technology.Therefore,the development and promotion of 5G mobile communication technology(5G)is imperative.As one of the keys to 5G,Multiple-Input Multiple-Output(MIMO)technology is a technology that installs a large number of antenna arrays at the base station,which can greatly improve the channel capacity and spectrum efficiency of the communication system.Compared with the frequency band resources occupied by existing communications,the millimeter-wave frequency band is extremely wide.Millimeter-wave has rich spectrum resources and can perform various broadband signal processing.It is easy to integrate large-scale antenna arrays in the millimeter-wave band.Millimeter-wave massive MIMO can achieve higher data rates and higher spectral efficiency through a wider signal bandwidth,becoming one of the key technologies for 5G wireless.Traditional digital millimeter-wave massive MIMO systems require each antenna to correspond to an independent radio frequency(RF)link,which has excellent performance when has a relatively small number of users.However,as the number of cell users continues to increase,the number of antennas at the base station increases.It also means that the number of RF links increases,and the number of hundreds of RF links in a cell will increase hardware costs and cause maintenance difficulties.Therefore,how to reduce the number of RF links required by traditional digital millimeter-wave massive MIMO systems without causing significant performance loss is a research hotspot for the majority of scholars.Therefore,this thesis conducts research on millimeter-wave massive MIMO systems and beam selection.The main research work of this thesis includes the following four aspects:(1)Analyze four models of MIMO system: single-user MIMO system model,multi-user MIMO system model,massive MIMO system model,and millimeter-wave massive MIMO system model,study several key technologies of MIMO.And analyze features of several keytechnologies by use block diagram.(2)Introduction of Non-orthogonal Multiple Access(NOMA)technology based on MIMO.Analyze the downlink multi-user MIMO-NOMA system model in detail,and study the user grouping and power allocation algorithms based on this system.Aiming at the shortcomings of the existing user grouping and power allocation algorithms,a new joint user grouping and power allocation scheme is proposed.The simulation results show that compared with the existing classic user grouping scheme,the proposed scheme can effectively improve he achievable sum rates of the downlink(3)For the traditional digital millimeter-wave massive MIMO system,each antenna is required to correspond to an independent RF link,which results in excessive hardware costs and excessive losses.In this paper,a beam selection scheme based on cuckoo search algorithm is studied.This solution considers the beam selection problem as a solution to the{0-1} knapsack problem.The beam to be selected is selected as a selected item to be loaded into the knapsack.The maximum sum rate of the system are used to solve the maximum capacity problem of the knapsack.Discrete cuckoo search algorithm to get near optimal solution.The heuristic greedy algorithm is used to repair the abnormal coding generated in the discretization results of the cuckoo algorithm Levy flight.The simulation results show that compared with the IA schemes,the proposed scheme can effectively improve the achievable sum rates of the downlink(4)Because the number of RF links in a beam space MIMO system cannot be less than the number of users and the system performance is limited,NOMA technology is introduced.Not only can increase the number of access users,and break the agreement that the number of RF links equals the number of users,and further improve performance.This paper studies beam selection on a beam space MIMO-NOMA system.In order to reduce interference between users and improve user sum rate performance,the user group is selected for beam selection.The simulation results show that the spectrum efficiency and energy efficiency achieved by the proposed scheme are close to existing millimeter-wave MIMO-NOMA schemes,but can reduce the decoding delay at the receiving end.