| As a comfortable,fast and safe means of transportation,the application of highspeed railway has attracted extensive attention all over the world.Especially in China,high-speed railway has developed rapidly and has become the main vehicle of medium and long-distance passenger transport.With the development of mobile Internet technology,passengers have a strong demand for information in the process of taking high-speed railway.How to use the limited wireless resources to meet the different service requirements of the passengers in the high-speed railway,wireless resource management has become very important.Wireless resource management is to flexibly configure and dynamically manage various resources in the system according to the location and channel state information of different users.On the premise of meeting the quality of service(Qo S)for users,it can improve the efficiency and reliability of the data transmission in the wireless communication system and optimize the system performance of the network.The wireless channel characteristics of high-speed railway and the Qo S requirements of different railway communication scenarios have brought great challenges to the wireless resource management of high-speed railway communication system.5G has the advantages of large bandwidth,large connection and low delay.It can realize the ubiquitous interconnection between people and things,things and things.It is a key new infrastructure to support the digital,networked and intelligent transformation of economy and society.In recent years,the Ministry of industry and information technology,China Railway Group and other business competent units have issued relevant policy documents requiring the in-depth implementation of the spirit of Chinese president Xi Jinping's important instructions on accelerating the construction of 5G network and other new infrastructure,focus on the railway with strong transportation,adhere to the new development concept,scientifically and pragmatically promote the construction of railway 5G-R private network,make full use of 5G public network resources,coordinate and promote railway application,and help railway digital transformation and upgrading.The introduction of these documents also provides policy support and reliable research significance for "private network construction and public network application" in the railway 5G field.Aiming at the diversity of the services for high-speed railway wireless communication and the complexity of wireless channels under the condition of 5G public network,this paper summarizes the research status of access control,mobility management,power allocation and resource management.On this basis,typical 5G communication technologies such as finite blocklength communication,mobile edge computing(MEC),physical layer security control and relay transmission are introduced,and the access control strategy,mobility management,power allocation and resource allocation methods are optimized.Under the constraints of minimum delay,the Qo S of users and data transmission security,the problems of maximizing the system performance and minimizing the energy consumption of users are studied,the relevant models and algorithms for solving the problem are proposed and verified by simulation method,which provides a theoretical basis for improving the service quality of railway application scenarios under the condition of 5G public network.The main innovative work and contributions of this paper mainly include the following four parts:(1)Considering the data uplink low delay transmission problem of multi-user in multi cell station under the condition of public network,multiple user terminals send information to the base station of the cell through the on-board relay equipment deployed in the carriage.All cells in the network use the overall spectrum resources,and the same channel in each cell can only be used by one on-board relay equipment.Therefore,under this assumption,there is no interference inside the cell,and there is interference between the cells.In order to support a wide range of ultra reliable and low delay communication applications,finite blocklength communication is adopted.The problem is a non convex integer optimization problem about the channel resource allocation,and the optimization objective is to maximize the uplink transmission system and rate of on-board relay equipment.Based on this problem,a distributed channel selection algorithm based on game theory is proposed in this dissertation,and its convergence is fully analyzed and proved.Simulation results show that the performance of the proposed algorithm in this dissertation is better than the known existing algorithms.(2)The MEC-assisted high-speed rail uplink communication system is considered,which includes multiple on-board relay equipments deployed on the train,multiple macro base stations with MEC server and an illegal eavesdropper.Using the offloading protocol,the computing task to be processed by the on-board relay equipment is divided into two parts: the computing task executed locally and the computing task safely offloaded to the roadside base station and executed by the MEC server.By jointly optimizing task scheduling,offloading rate and power control,the mathematical optimization problem is to minimize the sum of energy consumption of all the on-board relay equipments in the total time slots.Due to the coupling of task scheduling,task offloading ratio and transmission power,the original optimization problem is difficult to solve.Therefore,by fixing two of the three variables,the original optimization problem is decomposed into three sub-problems;the closed solution of the subproblem is derived.By introducing variables and using the continuous convex approximation method,the subproblems are transformed into a convex optimization problem,and different algorithms are proposed to solve it.Finally,based on the above process,a novel iterative algorithm is proposed,and the feasibility of the algorithm is verified by simulation.(3)Consider a high-speed railway wireless communication downlink secure transmission system,including the on-board relay equipments at the top of the train and multiple public network macro base stations deployed by operators within a certain range,and a mobile unmanned aerial vehicle with illegal eavesdropping devices.The objective function is to maximize the sum of the minimum security rate in each time slot.The constraints are the Qo S of the users,the handover requirements of the on-board relay equipments connecting to the base station and the total power constraint of the base stations.The minimum security rate refers to the minimum value of the security rate of multiple users in a time slot.The original optimization problem is a non-convex mixed integer optimization one.The block coordinate descent method is used to decompose the original problem into two sub-problems in this dissertation.One is the association between the base station and the on-board relay equipment,and the other is power control of the base station.The sub-problem of optimizing the association between the base station and the on-board relay equipment can be solved by continuous convex approximation algorithm,and the sub-problem of optimizing the transmission power can be solved by Lagrange dual method.On this basis,a joint optimization algorithm is proposed.Finally,by setting the simulation scene and simulation parameters of highspeed railway communication system,the efficiency of the joint optimization algorithm proposed in this dissertation is verified by simulation.(4)The relay downlink transmission system of high-speed railway based on finite blocklength is considered.The relay node on the top of the carriage uses decoding and forwarding to serve multiple users in the carriage.The research problem is to maximize the minimum throughput of users by jointly optimizing the transmission block length and the transmission power of the relay equipment.For the nonconvex optimization problem,by fixing the transmission power,the original optimization problem is transformed into an optimization subproblem about the block length.Through variable substitution and first-order Taylor series expansion,the closed expression of the block length can be obtained.By fixing the block length,the original optimization problem is transformed into a nonconvex optimization subproblem about the transmission power.By introducing the auxiliary variables and first-order Taylor series expansion,the nonconvex optimization problem about transmission power can be solved.On this basis,an alternating iterative algorithm is proposed.Finally,the effectiveness of the proposed algorithm is verified by simulation.Short message service,short message service and short message service are available for large numbers of customers to take high-speed rail tiktok.This algorithm has practical guiding significance for We Chat short message,tiktok short video and other services,when large numbers of passengers take high-speed railway. |
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