Geometry-Based Stochastic Modeling For Cooperative MIMO Channels In High-Speed Railway Scenarios

With the sharp development of high-speed railway,the demand of high-speed railway wireless communication network is rapidly increasing.In order to enhance the system capacity of high-speed railway wireless network,China has decided to evolve into the lons term evolution-railway(LTE-R)system.However,LTE-R system leads to echo channel effect(ECE),which limits the distance between base stations and increases the network cost.To eliminate the negative impact of ECE,cooperative multi-point technology is introduced into LTE-R system to form cooperative multiple input multiple output(MIMO)system.The multi-link correlation is one of the important characteristics of high-speed railway cooperative MIMO system.It is necessary to establish multi-link channel models to provide theoretical basis and evaluation references for the designs,testings,analyses and applications of cooperat:ive MIMO channels in high-speed railway scenarios.Therefore,two geometry-based stochastic models(GBSMs)are established to study the influencing factors of multi-link correlation.The work is as follows:(1)Based on the GBSM theory,a two-dimensional(2D)GBSM for cooperative MIMO channels in high-speed railway scenarios is proposed.The local scatterers around the train are modeled as a single ring model and the surrounding scatterers from the base station to the train are modeled as an ellipse model.The 2D model is used to analyze the influencing factors of multi-link correlation for high-speed railway cooperative MIMO system.Simulation results show that angle spread is the most important factor.The conclusions of 2D model are verified by existing literatures.The fitting result shows that the 2D model can effectively fit the measurement data of LTE-R system from Beijing to Tianjin high-speed railway section,which verifies that the 2D model can accurately model actual high-speed railway channels.The 2D model is a general channel model for high-speed railway cooperative MIMO system and can simulate a varnety of actual high-speed railway channels by adjusting model's parameters.(2)In order to more accurately model the cooperative MIMO channels in high-speed railway scenarios,a three-dimensional(3D)GBSM is proposed.The local scatterers around the train are modeled as a single sphere model,the surrounding scatterers from the base station to the train are modeled as an elliptic cylinder model,and a 3D GBSM for cooperative MIMO channels in high-speed railway scenarios is formed.The 3D model is used to analyze the influencing factors of multi-link correlation for high-speed railway cooperative MIMO system.Simulation results show that angle concentration parameters have the strongest influence on the multi-link correlation.The conclusions of 3D model are verified by existing literatures.The 3D model is verified by comparing the 2D model.The fitting result shows that the 3D model can effectively fit the measurement data of LTE-R system from Beijing to Tianjin high-speed railway section and verifies that the 3D model can accurately model actual high-speed railway channels.The 3D model is also a general channel model for high-speed railway cooperative MIMO system and can simulate a variety of actual high-speed railway channels by adjusting model's parameters.