Characteristic Analysis And System Performance Evaluation Of MIMO Channel In Rail Traffic Scenarios

Recently,rail traffic represented by high-speed railway and urban rail traffic has developed rapidly.The high-speed railway is expected to evolve into a new era of"Smart Rail Mobility" The construction of ultra-high-speed,high-reliability,low-latency,seamless communication connections is a key factor in the realization of intelligent railways to achieve a wide range of ground infrastructure,trains,passengers and goods.The channel characteristics are indispensable for wireless communication research.This paper focuses on the typical scenarios of rail traffic including viaducts,tunnels and train cars.The characteristics of radio wave propagation and wireless channel,including path loss,shadow fading,multipath and spatial dispersion,are studied based on ray tracing technology.Besides,the performance of MIMO system is analyzed and advices on the deployment of wireless communication networks for rail traffic scenarios are given.The main contents of this paper are as follows:(1)For the viaduct scenario,based on the modified SFN MIMO channel model,the antenna array type,array element spacing,rotation angle and other factors are simulated and analyzed in order to explore the the problem of system performance differentiation caused by non-stationary channel characteristics at different positions during train movement.The impact mechanism of MIMO system performance is studied.For 2-element antenna array,a linear array placed perpendicular to the rails provides better system performance.For 4-element antenna array,a circular array with the best rotation angle arctan(1/3)is better than a linear array with a gain of 9 dB,which means lowest SNR to achieve saturated throughput is reduced by 9 dB.(2)Based on ray tracing technology,the radio wave propagation and wireless channel characteristics under the condition of leaky cable coverage are explored.Conlusions can be drawn:The wireless channel can be considered as generalized and stable in the tunnel scenarios.The channel characteristics under different cross sections are similar so that a universal channel model can be adopted.It is recommended that the cable leakage be the same height as the vehicle body to ensure the existence of a direct path,reducing losses and delays for SISO system;The spacing of the leaky cables placed in parallel should be greater than 0.6m for MIMO system.(3)The radio wave propagation and wireless channel characteristics are studied based on ray tracing technology.It is proposed that the on-board relay antenna array should be placed in the vertical rail direction,which can achieve low spatial correlation and improve the gain of the MIMO system.The research results of this thesis can provide reference for the research of key technologies and the actual network deployment of public and private networks in rail traffic scenarios.