Wireless Channel Modeling For High Speed Railway Environments Based On Theoretical Methods

In recent years, the rapid development of China’s high-speed rail (HSR) has received international attention, also greatly contributes to the country’s economic growth. HSR communication has become a hot issue in current academia and industry. Existing railway communication system has been unable to meet the future demand ofHSR communications, research and development of a new generation of HSR communication system is imperative. As we all know, the channel model for the design of wireless communication system plays a vital role. Large scale fading model can be used for covering prediction and interference analysis of network. Small scale fading model can provide a reference for system simulation and algorithm assessment.This paper firstly introduces the propagation characteristics of radio channel in high-speed railway. According to the large scale propagation model obtained from several high-speed railway channel measurements in recent years, summarizes the measurement results under different scenarios with different bandwidth, lists the large-scale fading characteristics under different high-speed railway scenarios. This paper also introduces the small-scale fading characteristics, analyzes the extraction method of high-speed rail radio channel parameters (such as K-factor, Doppler power spectrum, multipath power delay spectrum).Then, describes the calculation method of channel capacity, combines with the actual measurement data, statistically analyzes the variation of ergodic capacity and outage capacity under different scenarios in high-speed railway environment.In the next two sections, this paper uses frequency-domain/time-domain theoretical analytical modeling methods, to establish wireless mobile communication system channel model in fast moving scenarios.(1) The propagation graph channel modeling method, the propagation environment can be described as a directed graph in which the vertices represent the transmitters, receivers and scatterers, and the edges stand for propagation paths between the vertices. Each propagation path can be characterized as an edge in this graph, can obtains the transfer function of the propagation channel finally. Then according to the actual measurement data, the method of Von Mises distribution simulating the angle-of-arrival of receive, and other methods, calibrate and verify the feasibility and research value of the propagation graph modeling method. This paper establishes channel model for typical HSR scenarios based on propagation graph method, obtains the channel CIRs through Matlab simulation, analyzes the key parameters of channel, discuss the fading characteristics of HSR mobile channel.(2) Based on geometrical random scattering theoretical modeling method, the channel characteristics are obtained for superimposed rays at receiving end. Typically, in order to facilitate the superposition of the time domain and simplify the mathematical derivation, this modeling approach assumes that the number of reflections and scattering in radio wave reflector is limited in the propagation model. This paper focuses on one-ring and elliptical model, in-depth studies the correlation function of its radio channel in time and space domains, deduces the closed expression of time-space correlation function. Then builds the channel model for HSR typical scenario based on one-ring model, analyzes the spatial correlation properties.Currently, channel modeling for HSR scenarios is mainly based on the actual channel measurement data. However, it’s more difficult to carry out the work of HSR channel measurements, and to obtain enough measuring data for channel modeling. With the development of channel modeling theory, stochastic propagation graph modeling and geometrical scattering theory modeling methods are two reliable and accurate channel modeling. This paper builds channel model for HSR scenarios based on these two advanced theoretical channel models. These models not only match with the actual measurement data, but also can be used to evaluate the performance of HSR multi-antenna system.