Research On Handover And Handover Self-Optimizing Algorithm For High-Speed Railway Systems Based On LTE Network

High speed railway (HSR) has developed rapidly in China for its properties of convenience and high speed. As the new generation LTE communication system can meet the requirements of higher data rate and bigger capacity, it has become the tendency of HSR wireless communication system. However, the high speed has brought about the frequent inter-cell handover and the traditional LTE handover algorithm may lead to severe wireless communication disconnections and call drops. Therefore, to study the LTE handover algorithm under HSR will improve the user communication experience. Considering the specialities of the LTE channel environment and the network design under HSR, this thesis proposes a handover self-optimizing algorithm based on the location information to effectively improve the handover performance. The main contents are as follows.The first part focuses on the optimized handover algorithm based on LTE under high-speed railway. The LTE network structure, protocol stacks and the signaling process are introduced firstly and the limitations of the traditional handover algorithms under HSR are given out. Then, an optimized handover algorithm based onlocation information is proposed. This algorithm uses the location of trains as the trigger of handovers, which will avoid most of the handover failures caused by the inappropriate settings of Time-to-Trigger in the traditional algorithms. Meanwhile, we propose a self-optimizing method to determine the location for handover and the location can be adjusted efficiently and accordingly with the variation of the specific environment. The radio link failure rate and downlink throughput are selected as indexes of the handover performance evaluation.After the detailed analysis of the properties of the simulation scenario under HSR, the second part verifies the excellent performance of the optimized handover algorithm. The handover self-optimazation algorithm was testified feasibly by simulating based on the LTE system level simulation platform LTE-SIM. Compared with the traditional algorithm in radio link failure rate and downlink throughput, the simulation results demonstrate that the proposed handover self-optimazation algorithm based on the location information takes full advantage of the characteristics of high-speed railway and has better handover performance.The handover self-optimizing algorithm based on location information proposed in this thesis has provided reference to the research about the mobility management in HSR scenarios. And it offers theoretical basis for the future design of the handover algorithm under high-speed railway.