Research On Key Algorithms And Performance Analysis In Several Scenarios Of Mm Wave Communications

With the development of wireless networks,wireless data services have grown explosively.In order to meet the needs of wireless communication application scenarios,future communication networks need to provide greater bandwidth and higher spectrum efficiency.However,as the low frequency band has become saturated,even if multiple access technology is adopted to improve spectrum efficiency,it will not be able to meet the needs of future communications development.So it is necessary to develop new spectrum resources.Compared with the low frequency band,the millimeter wave(mmWave)frequency band has rich bandwidth resources.The short wavelength of mmWave can be utilized to provide significant beamforming gain by arranging large antenna arrays.The value of mmWave has been recognized in the field of wireless communication,and has received great attention from industry and academia.In view of the characteristics of mmWave,the system optimization and analysis methods in traditional low-frequency communication are no longer applicable.For example,in an mmWave large-scale antenna system,the use of full digital beamforming will increase the hardware cost and the system power consumption;in an mmWave based heterogeneous network,due to the heterogeneity,randomness,and density of node distribution,the traditional method which uses a deterministic model for the spatial distribution of nodes cannot be adopted.Most of the existing mmWave research aims at specific hybrid beamforming design and system modeling analysis,but none of these works has fully considered the mmWave application scenarios.In the new generation of mobile communication systems,typical mmWave application scenarios include 5G high and low frequency hybrid networking,large broadband backhaul,and mobile edge computing(MEC)based private network.Designing algorithms for specific application scenarios and analyzing their system characteristics with a new analysis framework are the basis for the realization of the 5G communications industry,and have important application and research value.In addition,in mmWave communication systems,i.e.,mmWave based industrial Internet of Things and Internet of Vehicles systems,due to the use of air interface technologies such as large-scale antennas,wireless endogenous security elements are more abundant,and it is necessary to design physical layer security mechanisms for specific scenarios.In addition to traditional channel coding techniques,mmWave systems can also use large-scale array antennas to perform beamforming and design safety mechanisms in the spatial domain.Based on the above background,and combining the physical layer security technology,the thesis will design low computational complexity and high performance optimization algorithms,and analyze the performance of the mmWave hybrid networking.Focusing on the mmWave deployment scenario of private network,the thesis first studies the related problems of mmWave based MEC systems,and designs the joint beamforming and resource allocation algorithm with minimum system delay under specific communication and computing constraints.For single-user systems,the thesis seeks the special structure of the problem and divides it into two separate subproblems,and an iterative weighted mean-square error minimization(WMMSE)approach is proposed.For multi-user systems,due to the complexity of the objective function,the thesis introduces a series of auxiliary variables,inequality constraints and equality constraints,and then transforms the optimization problem into an equivalent but more tractable form,and the thesis designs a joint beamforming and resource allocation algorithm based on the Penalty dual decomposition(PDD)framework.The proposed algorithm can converge to the stationary point of the original problem,and can be implemented in a parallel and distributed fashion.A series of simulation results prove the superiority of the proposed algorithm,and prove that the integration of MEC technology and mmWave has broad application prospects at the same time.Secondly,focusing on wireless physical layer security,the thesis studies the transceiver design based on a new artificial jamming strategy in the next generation mmWave system.Specifically,the thesis investigates information surveillance in a device-to-device(D2D)mmWave system where a suspicious transmitter in the network sends messages to a suspicious receiver under the supervision of a surveillant controller(SC).The SC effectively monitors the suspicious communication link through beamforming and artificial jamming.The thesis considers the joint optimization problem for the suspicious transmitter and receiver's analog beamforming vectors,the SC's analog jamming and the monitoring beamforming vectors,and the jamming signal's power level,where the aim is to maximize the effective monitoring rate.In the proposed optimization problem,due to the high coupling of variables and the high non-convexity of the objective function and constraints,the thesis proposes a joint design algorithm based on the Penalty dual decomposition framework.In the inner loop the algorithm,the thesis constructs a new variable matrix by separating the real part and the imaginary part of the optimization variable,and at the same time adopt the Cauchy-Schwartz inequality to transform the original problem and construct the lower bound of the objective function.Then the thesis resorts to the effective Concave-Convex Procedure(CCCP)algorithm to solve the augmented Lagrangian problem.Through a series of simulation results,it is shown that the proposed algorithm can effectively improve the performance of the surveillance system compared with the traditional beamforming and jamming algorithms.Finally,focusing on 5G high and low frequency hybrid networking,the thesis studies the network performance of a downlink vertical heterogeneous network(V-HetNets)consisting of low frequency UAV air base stations(ABSs)and mmWave band terrestrial base stations(TBSs).Taking advantage of the unique attributes of drone mobility,flexibility and three-dimensional deployment,the thesis uses drones as ABSs to flexibly provide wireless connectivity,then a downlink V-HetNets model consisting sub-6GHz frequency ABSs and mmWave frequency TBSs is put forward.In this model,the TBSs serve as low power wireless access nodes which utilize mmWave to provide high speed transmission,while the ABSs utilize sub-6GHz frequency band and non-orthogonal multiple access(NOMA)technique to improve the coverage and freedom to serve multiple users.By using the tools from stochastic geometry,the thesis models the distributions of the ABSs and TBSs,develops a flexible association policy to address the co-existence of ABSs and mmWave TBSs,and derive the analytical expressions for the coverage probability and spectrum efficiency.Finally,Monte Carlo simulation are used to verify the performance of the V-HetNets,and verify the superiority of mmWave based hybrid networking,which theoretically provides a theoretical support for the design of the mmWave heterogeneous networks.