Research On Fast Handover Mechanism Under High-Mobility Scenario

Due to the lower energy consumption, less environmental pollution, larger transmission capacity and higher safety, high-speed railway has been playing an important role in mass transportation. The development of high-speed railway makes people’s lives more and more convenient; meanwhile, it puts forward much higher requirements on high-speed railway communication services. Moreover, new challenges of train-to-ground communication have emerged caused by high mobility: Doppler frequency shift and mobility management (especially the fast handover control) are two of the most important problems. Rapid changing of radio channel and over-frequent handovers make mobile communication access much more difficult. Therefore, it has practical significance to desigh fast handover mechanisms which have high speed adaptivity.In order to provide reliable communication service in high-speed train, two optimized handover schemes are introduced and analyzed in this thesis. The author’s main research work and contributions are shown as follows:Firstly, the main train-ground communication solutions are summarized in this thesis. As LTE having been chosen as the next generation’s evolution of railway communication system, challenges of railway communication system based on LTE are analyzed. Moreover, the architecture and handover mechanism of LTE system are introduced.Secondly, in order to improve handover success probability under high-speed scenario, a seamless handover scheme based on base station collaboration is putforward in this thesis. A co-channel LTE network approach for railway is proposed, then, the optimized scheme is designed, which enables the two adjacent base stations to serve the high-speed train by Co MP cooperative transmit technology. The comparisons of handover outage probability and handover success probability between LTE traditional handover mechanism and the proposed one show that the latter scheme has better performance.Finally, the author attempts to achieve reliable train-ground communicaiton by higher layer protocol. A seamless handover scheme which takes advantage of muti-homing and dynamic address reconfiguration features in SCTP. Meanwhile, on-vehicle dual-anntena approach has been introduced in the optimized scheme to enlarge the overlapping area. The proposed scheme achieves multi-path transmission by SCTP which improves the reliability of train-ground communication.