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

With the rapid development of high-speed railway in China, a significant increase in the speed of the train led to a serious decline in the quality of passenger communications, such as, frequent handover, high rate of dropped calls and so on. With its superior performance, especially the characteristics of high data rate and low system delay, LTE meets the communication requirement of high-speed railway better. In communication system, handover technique is an important component of mobility management, which has an indelible effect in the process of moving continuity solution, especially to ensure the communication quality in high mobility scenarios. In this paper, we will use the theoretical knowledge of LTE handover technology as the basis, and use MATLAB software to build a simulation platform for high-speed rail in the scene of LTE handover technology to do further research.This paper firstly discusses the network architecture, functions of each network element interface and wireless interface protocol of LTE system. Then introduce the role, trigger causes and classification of handover, and make a detailed description of handover process in LTE system. Secondly, it analyzes and summarizes the factors that affect handover of LTE in high speed railway scene, such as, Doppler shift becomes larger, the number of handover increases, the transmission loss increases, how to design handover belt and so on. Aiming at these problems, the corresponding solutions are put forward. Then the principle of traditional A3 handover algorithm is analyzed. And for its shortcomings, handover algorithm that base on the characteristics of terminal velocity and base on the statistical characteristics of handover trigger are proposed and optimize A3 algorithm. Finally, considering the traditional A3 handover algorithm and the modeling analysis of the handover algorithm based on the characteristics of the terminal velocity, it is proposed an optimized handover algorithm based on Doppler effect innovatively. A simulation platform is built by the MATLAB, which is used to test the improved handover algorithm and compare the results of these two algorithms. The improved algorithm can adjust the Handover Hysteresis Margin adaptively, so it can trigger a handoff according to the decision timely and quickly. Besides, we can judge the movement direction of the train based on the value of the Doppler shift, creating a list of the target cell in advance. It not only reduces the handoff delay, the Ping-Pong Handover but reduces the rate of dropping calls effectively, promotes the success rate. It has a better performance.