Research On Handover Technology Of LTE System In High-speed Railway Environment

In recent years,China's high-speed railways had continued to develop at a rapid rate,which had brought about convenient transportation,strengthened the rapid flow of population,material and information,and promoted regional cooperation and integrated development.However,the continuous speeding up of trains brought more and more serious problems such as communication interruptions and frequent handovers.As a result,the communication requirements of passengers could not be satisfied,which seriously affected the user experience.LTE took advantage of its high speed,large bandwidth,and other advantages to occupy an absolute advantage in next-generation high-speed rail communications systems.Supporting mobility was a typical feature of high-speed rail broadband mobile communications.Therefore,handover technology had become one of the important technologies for high-speed rail communications.This thesis studied how to improve the stability and reliability of high-speed rail communications from the perspective of LTE system handover technology to better meet passenger's travel needs.First of all,the thesis introduced the status of high-speed rail development and the difficulties faced by high-speed rail communications.Then it summarized the LTE system from the aspects of system network architecture,network element functions and network interface protocols to explain the advantages of LTE systems in high-speed rail communications from the system level.The system handover technology was elaborated,mainly including the concept,principle,flow analysis and signaling design of handover,the handover process and signaling design were mainly introduced.Next,the paper studied the traditional A3-based handover algorithm and analyzed its shortcomings.Aiming at these shortcomings,the thesis proposed a joint decision-based handover algorithm based on stochastic suppression,which improved the reliability and stability of the algorithm from the perspective of decision parameters and handover procedures.In view of the disadvantages of using fixed parameter,the BP neural network with its own momentum component was used to optimize the proposed algorithm,so that when the train ran at different speeds under different scenarios,it could select the appropriate channel and timing to switch and improved communication performance.Based on the theoretical analysis,this thesis used MATLAB simulation software to build a simulation platform,set the applicable platform parameters,and performed simulation analysis on the switching algorithms before and after optimization.The handoverprocess of improved algorithm had been optimized and the algorithm could select appropriate measurement quantity as the judgment reference quantity,which made it be able to select the corresponding parameter threshold according to different operating conditions.Therefore,it could effectively increase the handover success rate,reduced the phenomenon of ping-pong handover,and provided more stable and efficient communication services.