Research On Wireless Channel Model In High Speed Railway

With the rapid development of high-speed railway, the existing railway communication system can not meet the future demand of high-speed railway (HSR) communications. In order to achieve high performance communication, to ensure the safe operation of high-speed rail, and to meet the increasing data transmission speed that passengers demand, research and development of a new generation of railway communication system is very necessary. To establish wireless channel model of high-speed railway is the research foundation of high speed railway wireless communication system. This thesis focuses on the mobile wireless channel model of high-speed railway U-shaped groove and viaduct scenes.Firstly, the basic theory of HSR mobile wireless channel is introduced, several classical path loss model and the small scale fading are analyzed. Then the path loss model based on scene parameters (width and depth of the U-shaped groove, height of the viaduct and height of the base station antenna) are simulated and analyzed, and being compared with classic Hata path loss model. The simulation results show that Hata model cannot be directly used for high speed railway U-shaped groove and viaduct scene, and the unified standardization path loss (modified Hata path loss model) in high speed railway environment is analyzed. Because there is a strong line of sight path and multiple scattering paths under the two scenes, the simulation method of LOS and NLOS is studied. The improved Jake channel model is simulated and analyzed, and it is used to generate the single path Rayleigh fading signal in this thesis, and then the multi-path channel model is obtained according to measured data of each path and tap delay line (TDL) modeling. Finally, the small-scale fading characteristics of two scenarios are simulated and analyzed, the fading depth and the statistical value of the K factor of each scenario are given, and it is convenient for the designers of railway communication system to carry out the network planning.In order to overcome the shortcomings of the measurement-based channel modeling, a geometry-based rectangular stochastic channel simulation modeling of HSR cutting scenarios is proposed. Firstly, the position, shape and distribution of the rectangular stochastic cluster are analyzed, and the size of the model is derived. Then a simulation platform is built by MATLAB to verify the correctness of rectangle stochastic cluster model in U-groove scene, and the first order and second order statistical properties of the rectangle stochastic cluster model of cutting scenarios are analyzed. The simulation results show that the channel simulation model based on the rectangular stochastic cluster of the U-shaped groove scene are in high agreement with the measured value and the theoretical value.