| The flying development of high-speed railway technology drives increased requirements for high-speed railway broadband wireless communication system.Wireless resource management based on high-speed railway system is a research hotspot to improve system performance in recent years.Among them,considering the constraints of user’s quality of service requirements,system power limitations and channel quality conditions,power allocation algorithm distribute limited resources to users efficiently and reasonably,so as to improve the QoS performance of high-speed railway communication system.In the next generation of high-speed railway broadband wireless communication system,with users and multiple services coexisting,how to use limited network resources and design effective power allocation algorithm on the premise of ensuring the service requirements of different characteristics will help to achieve higher transmission rate,provide high-quality services for more users and support better system performance.It is the main issues in the research on user power allocation algorithm in high-speed railway wireless communication system in recent years.Firstly,this dissertation analyzes the research status of power allocation algorithm for high-speed railway users in domestic and abroad,then studies the service division of users,traditional power allocation algorithms,channel modeling of typical propagation scenarios in high-speed railway,and adaptive power allocation algorithms.The main research work has the following two points:(1)Aiming at the shortcomings of the single QoS index and user service studied in the existing power allocation strategy,the QoS indicator is extended to multiple metrics such as packet loss rate,delay,throughput,fairness and satisfaction among users,and a proportional fair power allocation optimization algorithm is proposed.Under the condition of meeting the minimum rate demand of each user,the improved priority scheduling factor combines with Water-Filling algorithm and takes the proportion of the single service QoS priority factor in all service priories as the weight,increases the allocation power orderly.Finally,the actual information transmission rate of real-time service is within the range of user satisfaction,and the minimum transmission rate of non real-time service is guaranteed.The simulation results show that the performance of the optimization algorithm is better than that of the traditional algorithms,and it can control the user satisfaction and fairness within a certain threshold while allocating as many users as possible to the desired rate to maximize the system throughput.(2)In view of the fact that existing research does not fully consider the problem of different users experiencing different fading caused by various scenarios in the operation of high-speed railway,an adaptive power allocation scheme of multi-user based on the wireless channel of high-speed railway is proposed.In the multi-user environment,combined with the research in chapter3,firstly,according to the real-time channel conditions of users and the minimum rate requirement of each user,the HSR user sub-channel allocation factor is introduced to divide the HSR channel into several sub-channels in advance.Then with the help of power-transfer rate utilization function,a part of power is pre-allocated to the sub-channels with better channel conditions.Next,in the iterative allocation process,the Romberg integration method is used to allocate power to the users with poor channel conditions and small rate proportion,so as to ensure the fairness among users.The simulation results show that the improved strategy can stabilize the fairness among edge users and users with better channel conditions and maximize the system throughput. |
