Research On Fast Handover Algorithm For Composite Scene And Ultra-High Speed Railway Mobile Communication System

By the end of 2019,China has built the largest GSM-R network in the world.With the development of the railway towards high-speed,intelligence,and information,the introduction of 5G mobile communication technology into the railway industry will become the evolution direction of the railway communication system in the future.Supporting high reliability,low latency,large capacity,and ultra-high-speed mobile adaptation has always been the performance index that high-speed railway mobile communication system is committed to achieving.However,the complex and changeable terrain,complex wireless environment along the railway,and high-speed of the train have posed great challenges to the reliable communication of the high-speed railway mobile communication system.Therefore,how to enhance the reliability of the ultra-high-speed railway mobile communication network architecture,and how to optimize the handover algorithm in complex scenes,are crucial for the system to further improve the communication performance.In this paper,we focus on two special scenes,composite scene and vacuum tube ultra-high-speed scene.Currently,there is little research on the handover algorithm for these two scenes.The main research works of this paper are as follows:(1)The relationship between handover parameters and handover performance in different scenes is analyzed.Channel parameters like multipath number and time delay spread are studied in order to study the characteristics of the wireless channel model in four typical scenes along the high-speed railway-viaducts,which are open areas,mountainous areas,and urban areas.Handover performance in different scenes is simulated and analyzed.The simulation results show that the same handover parameters have different handover performances in different scenes.With the change of scenes,the train also needs to use different handover parameters to trigger handover.(2)Based on work 1,an improved algorithm for handover performance based on composite scenes is proposed.Firstly,based on the characteristics of composite scene,a new network architecture is designed,which realizes the separation of control plane and user plane by "macro + micro base station".Based on this architecture,a relay micro base station is introduced into the handover overlapping area which can assist the service base station to complete the handover.This paper proposes a pre-handover algorithm based on parameter optimization in composite scenes.This algorithm can select appropriate handover parameters according to different scenes,and reserve resources in advance by taking advantage of the fixed trajectories of high-speed railways.Simulation results demonstrate the handover scheme based on composite scene outperforms the traditional handover algorithm in terms of communication interrupt probability and handover success rate.(3)Finally,for ultra-high-speed scenarios,the system architecture and handover algorithm suitable for vacuum tube trains are designed.The characteristics of the evacuated tube transportation system are analyzed.Based on reasonable assumptions,the redundant coverage reinforcement network architecture of "CU + RAU + Leakage Wave System" is designed to ensure the reliability of the communication of the evacuated tube transportation at ultra-high speed.In addition,based on this architecture,a pre-handover scheme combining with exceptions is proposed.Simulation results demonstrate that the proposed scheme can guarantee the reliability of the communication of the vacuum tube ultra-high-speed train,and shorten the handover processing time.The thesis has 31 figures,4 tables and 70 references.