Research On The Propagation Characteristic Of Control Signal Of High-speed Train

In order to meet the requirements of high security and high trustiness, the brain and command center of the high-speed train-Train Control System has to be researched. Train control signal is a kind of control information, used to guarantee the reliable and safe operation of high-speed train and transmitted through wireless channel. Therefore, it is urgently needed to study the channel propagation characteristics of the high-speed train control signal, which is an important prerequisite for the train running in safe and reliable condition.Firstly, a thorough review of the development history of mobile channel measurement methods, simulation and modeling methods were summarized in Chapter1. On the basis of the summary, the main content of this thesis was refined. Besides that, the background and significance of this thesis was also given. And then, in Chapter2the overview of Chinese train control system and the railway control signal were presented at the beginning, close behind was the major factors that affect the propagation characteristics of high-speed train control signal. These factors include high speed, large metal train carriage, pantograph-catenary disconnection pulse, multiple antennas on the ceiling, multi-paths and Doppler effects and other railway and train equipments and facilities. Therefore, this dissertation was commenced in the parts based on the above mentioned distinctive factors. The large-and small-scale fading characteristics of the high-speed railway operation system were analyzed in chapter3and Chapter4respectively. In Chapter5, the unique factor on the propagation characteristics of high-speed train, the running train carriage, was stated here. With the analysis results from the above chapters and the parameters of the real operation surroundings and conditions of the high-speed railways, a more realistic high-speed train mobile radio propagation model was set up and researched.The Innovation and creative points of this dissertation are outlined as follows:(1) An improved receiving power and distance model-the triple-slope model for high-speed railway control signal was raised and verified by the test data. Furthermore, the application bound of the model, the factors affecting the path-loss exponent and shadows fading were outlined here.(2) The impact of the Doppler Effect on the BER of high-speed train control signal was presented on the basis of the expressions of the Doppler shifts of the LOS path, the reflection paths from the train ceiling and the ground under different propagation environment. With analysis, some suggestions about engineering construction, like the location of base station were given here too.(3) The small-scale fading characteristics of the high-speed train control signal were measured and analyzed, such as the path and delay distributions, and also the Rice K-factor, the correlation of propagation environments.(4) Analyze the contributions from the secondary radiation field (comparing to the transmitting signal) on the train control signal propagation characteristics. The secondary radiation field was generated by the induced current and charge on train body. The research aspect has not been found yet from the published papers.(5) A more realistic high-speed train mobile radio propagation model was set up with the Markov birth and death chain, the pure birth process and the parameters of the real operation surroundings and conditions.(6) The doubly underspread propagation characteristics of the simulation model were considered by using the generalized local time-frequency variant scattering function. These features are just supplements of the small-scale fading characteristics. By the way, the validity of the simulation model was proved with the measured data in Chapter4and in this analyzing process.The measured data, derivation, results and conclusion obtained in this thesis can provide references for the design of actual high-speed train control signal, antenna type and layout, the choices of the base station site and other communication technologies, like coding, error correction, modulation, diversity, anti-fading, etc.