Research On Key Technologies Of Wireless Communication Systems For Vacuum Pipeline High-speed Trains

With the rapid development of the high-speed wheel railway,the next generation of ultra-high-speed rail—vacuum pipeline high-speed train,known as "the fifth type of transportation," has entered people's vision.The vacuum pipeline high-speed train can realize the all-weather ultra-high-speed(over 1000 km/h)operation of the maglev train in a low-pressure pipeline close to vacuum with low mechanical friction,low air resistance,and low noise.If this technology is commercialized,the travel time of passengers will be greatly shortened.Compared with the traditional high-speed rail,the vacuum pipeline high-speed train has two main characteristics: extremely high running speed and a unique running environment(closed long and narrow pipeline).The above characteristics put forward higher requirements for train-to-ground wireless communications.The existing wireless communication systems cannot provide adequate technical supports for serious Doppler effect and frequent handover of highspeed trains in a vacuum pipeline.To ensure the safe and efficient operation of trains,it is necessary to study the novel train-to-ground wireless communication system architecture of vacuum pipeline high-speed trains.Based on the current research status of train-to-ground wireless communication system and the characteristics of vacuum pipeline scenario,the dissertation intends to analyze the business performance requirements of high-speed trains in vacuum pipeline,study the unique wireless channel propagation characteristics of vacuum pipeline scenario,investigate the transmission performance of 5G network at vacuum tube highspeed train scenarios,and further explore new resource optimization methods.Specifically,the dissertation focuses on four contents:1)The requirements of train-to-ground wireless communication service for vacuum pipeline high-speed trains are analyzed and given.This dissertation summarizes the current train-to-ground wireless communication and wireless access technologies used in various wheel-rail traffic applications,and summarizes the requirements of train-to-ground communications.Based on the existing wireless communication technology,combined with the characteristics of vacuum tube high-speed trains and the communication requirements of current wheel-rail traffic,the data types and indicators of train-to-ground communication of vacuum pipeline high-speed trains are analyzed in detail.Finally,the main challenges of wireless communication between train and ground for vacuum pipeline high-speed trains are pointed out.2)Modeling and analyzing the wireless channel characteristics in the vacuum pipeline scenario.A deterministic channel modeling method,propagation graph modeling method,is adopted,and Lambertian scattering is introduced to improve the channel modeling accuracy.In the modeling process,Line-of-Sight(Lo S)component,single reflection component and double reflection component are considered to generate more accurate channel impulse response(CIR).Then,by analyzing multipath number,K factor,delay spread,and Doppler power spectrum,the channel characteristics of the vacuum pipeline scenario are described.Moreover,the capacity of the simulation channel and Rayleigh channel is compared by spectrum efficiency and singular value spread.3)The system performance of 5G network under the vacuum pipeline high-speed train scenario is studied.Based on the system-level simulation,the block error rate,spectrum efficiency and throughput of train control service and passenger service communication of 5G system in single base station and multi-base station scenarios are presented,and the system performance of 5G networks in high-speed train-toground communication scenarios is evaluated.4)A novel cloud wireless access architecture suitable for the vacuum pipeline scenario is proposed,which can significantly reduce the cost of resource migration.This dissertation discusses the feasibility of applying cloud radio access network(CRAN)to vacuum pipeline communications,and studies the resource migration of vacuum pipeline communications by using graph theory.In order to reduce the cost,a novel connection relationship between remote radio head(RRH)and baseband unit(BBU)pool is also proposed.On this basis,a flexible network architecture is established to allocate resources dynamically,and then the problem of minimizing the cost of resource migration is transformed into the shortest path problem.Simulation results show that this mechanism can significantly reduce the cost of resource migration.To sum up,this dissertation is forward-looking research on the key technologies of train-to-ground wireless communication for vacuum pipeline high-speed trains,which is helpful to form a solution to the critical problems of vacuum pipeline communications.These studies are of great significance for China to seize the commanding heights of rail transit technology,lead the future development of ultra-high-speed railway and ensure China's leading position in the field of railway technology.