Research On Base Station Handover Algorithms For High-speed Railway Mobile Communication System

In recent years,with the advent of the Internet Plus era,high-speed rail travel has become popular,and that leads to explosive growth in data traffic of mobile terminals accessing the Internet on high-speed trains,which requires high-speed railway communication systems with good stability and reliability.Therefore,in the face of communication interruptions caused by signal instability,frequent switching,car body penetration loss,and Doppler effects in high-speed train mobile communications,how to design effective and novel handover scheme to reduce the probabilities of handover failure and communication outrage,has become a research hotspot in high-speed rail communications.This thesis focuses on base station handover algorithms with different network architectures,and the main contributions are summarized as follows:(1)Base station handover algorithm based on the dual-link network architecture: for the existing solutions,as soon as the handover conditions are satisfied,the antenna can perform multiple handovers to reduce the handover failure rate.However,due to the low signal strength,it is difficult to have a suitable handover opportunity.Therefore,an improved handover scheme is presented to optimize the handover conditions,in which the front antenna performs handover under the condition that the signal strength between the front antenna and the target base station is greater than the signal strength between the rear antenna and the target base station,otherwise the rear antenna will immediately join the front antenna to perform multiple parallel handovers.Numerical results show that the improved dual-link base station handover algorithm can effectively reduce the probabilities of handover failure and communication outrage.(2)Base station handover algorithm based on control user plane separation: employing millimeter wave beamforming technology and based on control/user plane separation,a position adaptive dual-link seamless handover scheme is proposed.In the proposed scheme,when the train is about to enter the overlap of the macro base stations or micro base stations,the target macro/micro base station will supplement its overlapping area with millimeter wave directional multi-beam gain,which can enhance the received signal strength(RSS)of the handover antenna to greatly increase handover trigger probability and optimize the handover conditions.At the same time,dual-cast and beamforming technologies are used to optimize the handover signaling process.Numerical results show that the presented scheme can effectively increase the probabilities of handover trigger and handover success,and reduce the probability of communication outrage.