| With the rapid development of high-speed railways and the widespread use of smart devices,the requirements of high-speed railway wireless communication systems for rate,delay and broadband are also increasing.In the face of the contradiction between people’s growing demand for wireless networks and limited wireless resources,the management of wireless resources in high-speed railway scenarios is urgent.Different from traditional mobile communication,the high-speed mobility of high-speed railways has a significant impact on wireless communication performance.At present,the realization of the "double carbon" goal faces many obstacles and challenges,and improving energy efficiency(EE)is an effective means to reduce carbon dioxide emissions.Therefore,it is of great significance to optimize the energy efficiency performance in high-speed railway scenarios.This thesis mainly studies the power allocation of energy efficiency in high-speed railways wireless communication.The main contents of the thesis are as follows:Firstly,the channel characteristics of high-speed railway wireless communication system are analyzed.The state of wireless channel is the key factor affecting the quality of service of high-speed railways wireless communication.We summarize three major challenges faced by high-speed railway wireless communication: carriage penetration loss,Doppler effect and handover.On this basis,according to the characteristics of wireless channels of high-speed railway,the high-speed railway communication schemes based on mobile relay technology and Distributed Antenna System(DAS)are discussed,and their advantages and disadvantages are studied.This thesis also introduces the design index of resource management,related power allocation technology and the shortage of resource allocation of high-speed railways wireless communication.Second,this thesis uses a combination of the Quasi-Newton algorithm and the Armijo criterion to solve the downlink EE optimization problem for high-speed railways wireless communication.By installing the wireless Access Point(AP)on top of the train to avoid the carriage penetration loss,the model of system is established as a multi-constraint mixed integer programming problem by jointly considering the constraints such as user communication fairness and the average transmit power of the evolved Node B(e NB).Among them,the proportional fairness among users is solved by setting a fairness threshold.Considering the form of the objective function and the non-convex constraints,the non-convex optimization problem is transformed by the Hypograph form of the objective function,and a combination of the Quasi-Newton algorithm and the Armijo criterion is used to optimize the energy efficiency of the e NB downlink.The effectiveness of the algorithm in this scenario is verified by simulation.Finally,this thesis studies the EE power allocation method of high-speed railway wireless communication systems under DAS application,optimizes the energy efficiency of downlink information transmission link,and proposes an iterative transformation algorithm based on Dinkelbach-Quadratic.Considering the constraints of minimum transmission rate and maximum transmission power,the optimization problem is modeled as a non-convex optimization problem.Since the optimization problem is a nonlinear fractional form,this thesis uses the Dinkelbach-Quadratic iterative transformation algorithm to solve it.Firstly,the Dinkelbach transformation is used to convert the objective function into a difference form,and the iterative algorithm of the Dinkelbach transformation is not applicable in the scenario of multi-link communication.Therefore,it is necessary to further convert the objective function through the Quadratic transformation,and finally determine the optimal power allocation scheme by alternating iteration.The feasibility and effectiveness of the algorithm are verified by simulation comparison. |
