Research On Key Technologies Of Distributed MIMO In High Speed Railway Mobile Communication Systems

The rapid development of high-speed railway poses a great challenge to wireless communication,the bandwidth allocated by existing GSM-R can no longer carry the demand for future high-data-communication services,such as passenger broadband wireless communication access services,intelligent train dispatching,and video surveillance services.In order to meet the development trend of high-speed rail next-generation wireless communications,the International Union of Railways(UIC)confirmed that GSM-R will evolve to LTE-R.Based on the forward-looking nature of basic research,it is necessary to design a new generation of broadband wireless access network architecture that adapts to the high-speed railway environment.As one of the key technologies of LTE,Multiple Input Multiple Output(MIMO)provides a means to greatly increase system capacity for future mobile communication systems,especially for high-speed data access services.Therefore,how to exploit the advantages of MIMO technology in the wireless communication scene of high-speed railway has become a research hotspot in railway communications.Analysis of the MIMO channel capacity of high-speed railway will provide some theoretical support for the future development of vehicle-to-ground communications engineering.The paper focuses on three aspects:First of all,the analysis of wireless communication access scheme for high-speed railway vehicles.A brief overview of the special characteristics of high-speed railway wireless communication scenarios is presented,and the three major challenges faced by high-speed railway wireless communications are summarized: Doppler effect,switching problems,and high-speed railway body loss.The current technology status is analyzed,and a broadband wireless access scheme for high-speed railway is designed—a distributed MIMO two-hop communication architecture.Secondly,research on distributed MIMO power allocation algorithm for high-speed railway.This paper analyzes the principle of EPA average power algorithm and WP water pouring power algorithm in two kinds of power allocation algorithms in MIMO system,and applys to the high-speed railway.The simulation is carried out under the high-speed railway simplified channel model Rice channel and LOS direct peth,and the performance of the two algorithms in the high-speed railway wireless communication scenario is compared and analyzed.Finally,research on optimization of antenna spacing based on line-of-sight component.Because there is a line-of-sight component in the wireless communication channel of the high-speed railway,the LOS component will result in a fullness of the channel matrix,thereby reducing the capacity of the MIMO system.This paper proposes an optimization design criterion for antenna element spacing based on line-of-sight components.Firstly,channel modeling of high-speed railway distributed MIMO is performed.Mathematical analysis is used to derive the effect of array spacing on channel capacity.Then,the deterministic channel matrix is used to perform mathematical analysis based on the optimal capacity criterion.The optimal spacing deployment scheme between the remote antenna unit RAU and the vehicle relay TAU antenna is proposed.Finally,Monte-Carlo simulation results show that the optimal antenna spacing scheme proposed in this paper has universal adaptability and good performance compared with the traditional half-wavelength antenna setup in high-speed railway LOS channel environment and Rice channel.