Research On Wireless Channel Fading Characteristics And Non-stationary Characteristics In The High-Speed Railway Scenario

With the rapid development of high-speed rail,the research of wireless communication system in high-speed mobile scenario has become a hot topic.As the foundation of the design of the communication system,channel has become the primary issue of the research.In order to meet the needs of high quality wireless communication in the high-speed rail scenario,and provide a real reference for the prototype design of communication system and the simulation at link level,we need to have an accurate understanding of the characteristics of wireless channel.Therefore,this paper analyzes the channel propagation characteristics in the high-speed rail scenario,and provides data support for the realization of the communication system based on the measured data of the wireless channel.Firstly,the basic characteristics of wireless channel and the principle of channel detection based on LTE are introduced.Then,based on the actual channel measurement data,the characteristics of wireless channel in the high-speed rail scenario are analyzed comprehensively.According to the environment of channel measurement,three common high-speed railway scenarios including plain,station and suburb are selected.Based on various parameters,the channel characteristics in different scenarios are compared and analyzed.For large-scale fading,the trend of the path loss with distance and path loss factor and the comparison of the pass loss in three scenarios are presented,and this paper contrasts path loss with those that in free space.The results of the shadow fading are fitted,and the results show that the shadow fading in three scenarios can be conformed to the normal distribution well.For the small-scale fading characteristics,this paper analyzes the typical characteristic parameters such as Ricean K factor,root mean square(RMS)delay spread and power angle spectrum in three scenarios and draw the conclusion that multipath components in environment have an important influence on those parameters,and the number of the multipath components in the plain is the most,followed by the station and the least in the suburb.Considering the influence of signal transmitted by adjacent base station in the actual situation,this paper also analyzes the changes of the Ricean K factor and the RMS delay spread while the receiver is affected by neighboring base station.The results show that the Ricean K factor becomes smaller and the RMS delay spread becomes larger in this case and this effect only works if the distance between the train and the base station is greater than a certain threshold.This paper also focuses on the non-stationary characteristics of the channel.The analysis of the stationary interval show that the stationary characteristics is best in the plain and worst in the suburb,with the station lying in between.Then,this paper uses a method called RUN TEST to analyze the non-stationary characteristics of the channel from the perspective of sequence randomness.The conclusion is consistent with those that drawn from the stationary interval.Considering the dynamic changes of the multipath components during train operation,this paper proposes the Markov process to describe this change according to the life and death of the multipath components,and presents the non-stationary tapped-delay line model based on Markov process.