Research On Key Technologies Of Fronthaul For High-speed Railway Broadband Wireless Access Based On RoF

With the popularity of broadband portable mobile terminals and the rapid development of high-speed rail in recent years,high-speed rail passengers have an increasing demand for real-time broadband communication,forming a high-density,high-throughput high-speed mobile communication scenario.Although the millimeter wave(mmW)wireless communication system can provide large bandwidth,high speed and real-time uninterrupted bandwidth wireless connection between mobile train users and ground base stations,the serious loss of millimeter wave in the atmosphere limits the cell radius,requiring very dense cell base stations along the railway line,and users on high-speed trains frequently switch between adjacent cells,causing communication Drop-words and ping-pong effects,resulting in severely limited communication quality;and millimeter wave electronic equipment is expensive.The wireless signal fronthaul technology based on radio over fiber(RoF)uses low-loss optical fiber to transmit microwave and millimeter wave signals,which has the characteristics of large bandwidth and high speed.has significant advantages.Aiming at the handover problem faced by the high-speed railway(HSR)broadband millimeter-wave signal fronthaul network based on RoF technology,this paper deeply studies the fronthaul technology of uplink and downlink millimeter-wave signal in the HSR mobile fronthaul network based on RoF technology,and proposes a wavelength-stepping-based The RoF linear cellular synchronous mobile solution,and then realize the stable communication between the mobile train and the cellular system along the railway in the bus type and ring structure full-duplex fronthaul network.The main research work of this paper is as follows:(1)A full-duplex fronthaul bus network scheme based on RoF HSR synchronous mobile linear cells based on wavelength stepping is proposed,using step-wavelength laser arrays,optical circulators and fiber Bragg gratings and other devices,through dynamic regulation of step-wavelength The laser emits lasers of different wavelengths to build a mobile cell corresponding to the multi-wavelength "sliding window" synchronized with the moving train,so that the train can establish a stable connection with the ground cellular system and avoid frequent switching of uplink and downlink wireless signals.The simulation results of uplink and downlink signals show that bidirectional transmission signals have good performance;(2)In order to avoid the influence of the Rayleigh scattering effect between the uplink and downlink signals in the bus structure,a full-duplex fronthaul ring network scheme based on RoF high-speed rail synchronous mobile linear cells based on wavelength stepping is proposed,so that the uplink and downlink signals are transmitted in the same direction.Under this scheme,there is no need to consider how to reduce the influence of Rayleigh scattering effect.The uplink and downlink can use the same sideband radio frequency signal and carry the same frequency radio frequency signal,and the signal transmission performance under the same conditions is better than that under the total linear structure.The transmission performance of uplink and downlink signals is verified by simulation.