Research On Handover Algorithms Of TD-LTE System In High-Speed Railway Environment

The purpose of this paper is to research on the issue that there are frequent dropped calls, and poor communication quality of service in TD-LTE for high-speed rail system. Firstly, this paper has a based study on LTE system air interface protocol, E-UTRAN mobility management, inter-cell handover algorithm as a traditional theoretical foundation, and then focuses on the switching problem in TD-LTE system. Switching algorithm performance largely determines the quality of mobile communication when UE goes through different cells.Firstly, this paper takes a deep study of the major TD-LTE network architecture system, the access network air interface protocol and the E-UTRAN mobility management processes, and then analyzes the handover signaling process of LTE system. According to the inherent characteristics of high-speed railway communication system:a linear network topology, the trajectory of the UE is known, the UE’s target cell can be obtained according to its direction of movement, etc. are known, then puts forward three TD-LTE system optimized handover algorithm.1switch terminal velocity based on different parameters optimization algorithms;2switching algorithm based on known information from UE;3improved soft handover algorithm in TD-LTE system.Wherein the first and the third are based on the traditional A3event trigger algorithm, the second is based on the characteristics of railway communication system, you need to know to the speed of UE, direction, location information, etc. The first switching algorithm theoretical analysis and simulation results show that the system can achieve the best performance when system selects a reasonable combination of parameters (switching threshold, TTT trigger delay counter) by comprehensive considering PPHO and the rate of RLF. The starting point of the second handover algorithm based on information already known is to minimize signaling overhead of periodic measurement, lower latency, and fast switching with a high reliability. The handover decision is mainly determined by whether the UE reaches the fixed position. The third improved soft handover algorithm borrowed ideas from TD-SCDMA. This soft handover idea is only under discussion in TD-LTE high-speed rail system. Improved soft handover algorithm has a high signaling complexity, but the success rate of wireless link will be significantly improved while compared to the previous two.