LTE System Performance Evaluation For High-Speed Railway Environment Based On HIL Simulation

With the rapid development of high-speed railway,in order to meet the increasing demand of railway mobile communication business and comply with the requirements of technological development and industrial upgrading,the evolution of GSM-R into next generation railway mobile communication has become a trend and promoting LTE technology in high-speed railway is imperative.At present,the International Union of Railways and the European Railway Administration are all actively promoting the research,standardization,testing,application popularization and industrialization of LTE technology in the high-speed railway scenario.However,LTE system in high-speed railway is obviously different from the public network in radio propagation environment,networking mode and high-speed mobility.Therefore,it is urgent to evaluate LTE system performance in high-speed railway environment before the actual network deployment.Compared with the public mobile network,the high-speed railway scenario mainly has the characteristics of large Doppler shift and the base station coveraging along the railway tracks.The network deployment mainly adopts Single Frequency Network.Such network deployment will lead to "multi-path".In the OFDM technology adopted in the LTE system,the Doppler shift will destroy the orthogonality between the subcarriers,and multipath will lead to inter-symbol interference,resulting in the deterioration of system performance.Hardware-in-the-loop simulation technology can build a simulation environment in the laboratory,which is close to the actual scene.This paper will evaluate the LTE system performance under high-speed railway environment based on the hardware-in-the-loop simulation platform,study the dynamic channel semi-physical simulation method,analyze the impact of Doppler shift and multipath interference on system performance,and provide suggestions for the deployment of LTE system in high-speed railway scenarios.At the same time,it will lay the foundation for LTE high-speed adaptability research.The main work of this paper is as follows:(1)Build LTE hardware-in-the-loop simulation platform and research the receiving power indicator.Aiming at the problem that the channel simulator only supports the simulation of fixed delay,a simulation method combining computer simulation technology and hardware-in-the-loop simulation technology is proposed to realize the dynamic channel semi-physical simulation.Based on the simulation results and theoretical analysis,this paper gives a reasonable recommended value of sample density and dynamic delay number;(2)Based on the single-tap HST channel model and the Rician channel model,the simulation cases are designed to evaluate the impact of Doppler shift and receiving power on LTE system performance and give suggestions on the aspects of frequency selection,high-speed adaptability,high speed margin and so on;(3)Analyze the channel characteristics of SFN two-tap channel model.Research on the influence of the mutipath delay,power and Doppler shift and evaluate the effect of multipath interference on the system performance.According to the environment of actual high-speed railway scenario,the SFN two-tap channel model is improved by considering the scattering components.Evaluate the system performance and determine the range of system performance deterioration in this scenario.The research results of this thesis can provide technical and platform support for the research of LTE key technologies,equipment and system testing.At the same time,it will lay the foundation for field test and construction of engineering test section.