Research On Optimization Of High Speed Railway Handover Scheme Based On LTE

In recent years,with the rapid development of China's high-speed railways and the ever-increasing speed of trains,the technical requirements for high-speed rail wireless broadband communication systems have also been continuously raised.It has become a necessary factor for the development of high-speed railways that make the ever-increasing demand for wireless data communications come true.As the most advanced mobile communication standard at present,LTE greatly adjusts the network architecture and access technologies of the existing 3G systems.The flattened and IP network structure has the advantages of high data transmission rate and low system latency,the International Union of Railways has decided to make LTE-R as the railway wireless communications system in the future.As an important part of mobility management of railway wireless broadband communication system,handover is of great significance in solving the problem of continuous communication during train movement and ensuring wireless communication quality of high-speed train.Therefore,the research based on LTE-R handover technology has great practical significance.The main content of this thesis is the handover.On the one hand,the high-speed train movement brings many challenges to the wireless broadband communication system,such as Doppler shift,frequent handover and so on.On the other hand,the handover hysteresis threshold and time to trigger of the traditional LTE-R handover algorithm can not adapt to the high-speed train movement,with the same handover hysteresis,the higher speed of the train will lead to the greater probability of handover failure and impair train's traffic safety and passenger wireless communication experience.Through summarizing and improving the existing schemes,the problems of frequent handover,Doppler shift and penetration loss are solved.At the same time,a handover optimization scheme based on power and distance is proposed,and the distance factor is added under the influence of speed to the handover parameters,which effectively guarantees the handover success rate under high-speed environment.This scheme has the advantages of fast handover and avoiding errors trigger and achieving higher handover success rate and so on.Firstly,the LTE/LTE-Advanced network architecture,air interface protocols,technical features and the key technologies are described in this thesis.Then the handover technology is introduced,including the signaling process and related parameters of the handover,and the high-speed rail technology challenges are described from the perspective of high-speed rail wireless coverage.The solution and the completion of the link budget lay the foundation for the performance of the A3 algorithm.Finally,the existing high-speed rail handover algorithms are summarized,and an improved algorithm is proposed to ensure the rapid and accuratehandover of trains by reasonably setting the handover parameters,pre-allocating the channel of the target cell,and adding distance assistance information.The simulation results show that the improved scheme can better ensure the handover success rate in high speed environment.