Research And Simulation Of LTE-R System Handover Technology In High-speed Rail Environment

With the development of the times,the GSM-R railway mobile communication system has been unable to meet future service requirements.With its high channel capacity,high frequency bandwidth and high speed transmission,LTE-R has become the next generation railway mobile communication system approved by the UIC.Handovering technology is one of the key technologies in the high-speed railway communication system.An excellent handovering algorithm is the basis to ensure that communication is not interrupted.LTE-R system handovering technology in high-speed rail environment is mainly studied in this thesis.The purpose of this study is to reduce the number of ping-pong handovers in high-speed mobile environment,improving the success rate of system handover,and ensure that the train can complete handover quickly and stably when running at high speed.Aiming at the research on the handovering technology of LTE-R system from the two perspectives of handover measurement and handover decision,a handover scheme suitable for high-speed mobile environment is proposed in this thesis,and its correctness is verified by a simulation platform built in this thesis.In this thesis,the LTE system architecture,protocol stack,and handovering technology is first explained.Then,the A3 event-based handover algorithm is researched,and the shortcomings of the A3 event-based handover algorithm in high-speed mobile scenarios are analyzed.Based on the research on A3 event handover algorithm,the algorithm is optimized.From the perspective of handover measurement,a handover algorithm based on the Verhulst prediction model is proposed.The algorithm uses the Verhulst prediction model to predict the received signal strength of the serving cell and the target cell.The predicted signal strength value is reported to the serving cell for handover decision,which improves Judgment accuracy and handover trigger rate,reducing ping-pong handover rate.Aiming at the problem that the switching parameters of the A3 event switching algorithm are fixed,a dynamic parameter switching algorithm based on neural network is proposed,and the parameters of the switching algorithm are predicted and dynamically adjusted according to the running speed of the train.Based on the NS-3 system-level simulation platform,the LTE-R mobile communication system is built to simulate the handover performance of the system when different handover parameters are set when the train is running at different speeds.The switching parameters with better switching performance are extracted to train the neural network.The trained neural network entity is deployed on the train side,the train’s running speed is used as the input of the network,and the network output is set as the switching parameter corresponding to the speed.The simulation results show that the dynamic parameter switching algorithm can effectively reduce the number of ping-pong handovers of the system,improve the handover trigger rate,and the train handover position is closer to the midpoint of the handover belt.