Modeling And Simulation Of High Speed Rail Wireless Channel In Mountainous Environment

In recent years,with the rapid development of high-speed railway in the world,it has become the preferred means of transportation for more and more people to travel because of its fast running speed,strong passenger carrying capacity,small impact by the external environment,green environmental protection and other characteristics.Since the birth of high-speed railway,wireless communication is needed all the time.One is that the control system of high-speed train needs wireless communication to carry,which is an essential factor for the safe operation of high-speed train.Second,passengers in the train have higher requirements for real-time wireless communication services.Therefore,in the process of train operation,a safe,stable and reliable wireless communication system is very necessary.While the high-speed railway will experience typical scenes such as mountains,tunnels,viaducts,plains,etc.each scene has its own terrain characteristics,so the wireless channel propagation characteristics in different scenes are different,among which mountain terrain is widely distributed.Compared with other scenarios,there are a large number of scatterers around the train when the high-speed train runs in the mountain scene,and the size and distribution of scatterers are uneven.Therefore,in order to better meet the communication service needs of the high-speed train,it is necessary to accurately establish the wireless channel model in the mountain scene of high-speed rail.This subject study the wireless channel model in a mountainous environment,uses the finite state Markov chain as the theoretical basis,and uses the equal area interval division strategy to divide the position of the train and base station.The Finite-State Markov Chain(FSMC)was established in each interval,and the established wireless channel model was simulated and analyzed to verify the accuracy of the model.The main content and research results of the paper are as follows.(1)Firstly,the propagation mode of high-speed railway wireless signal and the typical propagation scenarios of high-speed railway train are studied.Aiming at the fading characteristics of high-speed railway wireless channel,two aspects are analyzed: large-scale fading and small-scale fading.It also lists several typical scenarios for high-speed railways,such as ray tracing model,Okumura model,geometric random model,propagation graph model,etc.,and analyzes the applicable conditions and applicable scenarios of each channel model one by one.According to the terrain characteristics of mountain scene,when there are a lot of scatterers around the train,the above models can not be well used in High-Speed Rail mountain scene.The FSMC channel model is a statistical model that can track the signal power strength of different positions of the train,and can better adapt to the complex environment of mountain scenes.(2)Secondly,the finite state Markov chain is used to model the high-speed rail mountain scene.Firstly,MATLAB is used to simulate the path loss data under the mountain scene,and then the average received signal-to-noise ratio(SNR)of the receiver is calculated.Use the equal area interval division strategy to divide the relative position between the base station and the train into intervals,and use the finite state Markov chain to characterize the SNR channel state in each interval,and then derive the state probability of SNR in each interval Steady State Probabilities(SSP)and State Transition Probabilities(STP)are closed expressions.According to the widely distributed characteristics of scatterers in mountain scenes,the probability distribution function of SNR is determined,and the threshold,quantization value and state transition probability matrix of SNR in each interval are further derived,and then the mountain scene is established in each interval FSMC wireless channel model.(3)Finally,through theoretical analysis and simulation experiments,the FSMC wireless channel model using the equal area interval division strategy and the FSMC wireless channel model using the non-uniform interval division strategy,and the FSMC wireless channel model using the uniform interval division strategy are compared and analyzed.By using the minimum mean square error criterion,the mean square error value of the FSMC channel model using the equal area interval division strategy can be minimized,thus verifying the accuracy and rationality of the model proposed in this paper.