Research On High-speed Rail Wireless Coverage And Its Handover Technology

With the advent of “Intelligent High-speed rail” era,trains and passengers put forward higher requirements for wireless communication network.The traditional GSM-R railway communication system has been unable to meet the communication requirements of high bandwidth and low latency,so the development of the next generation railway communication system LTE-R has become an inevitable trend.As trains continue to increase speed,frequent handover and link disconnection caused by high-speed movements bring huge challenges to train communication.How to ensure the quality and stability of communication in high-speed rail scenario has very important research significance.To solve this problem,this paper studies the coverage of train wireless network and the handover algorithm of the LTE system.The main work and achievements are as follows:(1)Aiming at the communication difficulties in high-speed rail scenario,a train wireless coverage scheme based on the gateway and Wi-Fi LAN was designed.The relay gateway accesses the ground networks through LTE link upstream to provide Internet data for the whole high-speed rail,and provides the wireless network for passengers by using Wi-Fi signal.The adoption of double-layer network architecture can effectively avoid the impact of train penetration loss,group handover,and single link failure on the train communication network,and maximize the Internet experience of passengers in the train.(2)Aiming at the disconnection caused by frequent handover of LTE links,the existing handover algorithm based on A3 event decision has been improved,and a joint algorithm of A3 and A4 event based on the best handover position is proposed,which converges the trigger position to the best reference point to improve the handover success rate.Through the theoretical analysis of handover performance and simulation verification by LTE-Sim platform.The results show that the optimized handover algorithm can reduce the probability of handover failure from 11% to 6%,and improve the efficiency of handover of the single antenna.(3)Based on the optimization of the handover performance of the single antenna,a dual antenna linkage algorithm by the front and the rear antenna has proposed.The rear antenna handover parameters are optimized based on the results of handover of the front antenna,so that the algorithm has an adaptive ability to deal with the changes of environment.Compared with historical handover data,the effect of the front antenna is more instructive.The simulation results show that the dual antenna linkage algorithm can effectively improve the success probability of the rear antenna handover from 91% to 98% and ensure the link stability of the vehicle communication system.