Research On Designing And Optimization Of Signalling Of Td-Lte Based On High-Speed Handover

Broadband wireless communication system based on TD-LTE (Time Division-Long Term Evolution) system in high-speed railway can significantly provide the voice communication, data communication, internet traffic, public information inquiry and train video monitoring traffic. The velocity of train is350km/h and the distance is10kilometers between the two cells. The high-speed train runs so fast that the user equipment (UE) will take about100seconds to pass from one cell to the neighboring cell, which leads to handover in the period of almost every100minutes. Thus will cause serious wireless communication network disconnection and call drops and result in the decline of the network performance at the same time.This thesis focuses on the research about the handover algorithm of TD-LTE system in high-speed railway environment, which is composed of four parts, it is as follows:The first part of the thesis concentrates on the research about the measurement of TD-LTE physics layer Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ). Firstly, the generation of reference signal is studied for TD-LTE system. Secondly, the establishment of physics layer link level simulation platform is introduced for TD-LTE system and the bottle-neck of some modules algorithms feasibility is analyzed in the link level simulation platform. The thirdly, the simulation platform measures RSRP and RSRQ is introduced by the measurement algorithm of RSRP and RSRQ. At last, the measurement results of RSRP and RSRQ are analyzed under the different measurement bandwidth and the velocity of the user equipment (UE) via the simulation platform of the physics layer developed by MATLAB software.The second part of the thesis describes the research on the optimization of event A3triggering handover algorithm based on TD-LTE system in high-speed railway scenario. Firstly, the analysis are represented about two kinds of event A3handover judgment criteria based on the velocity of the UE, which is compared to common event A3handover judgment criteria. Then the establishment of TD-LTE system level simulation platform is introduced. At last the simulation result shows the feasibility of two kinds of optimized handover algorithms, which improve handover success rate significantly.The third part of the thesis mainly focuses on two kinds of handover algorithms of TD-LTE system based on GPS information and pre-bearer procedure of target eNodeB in high-speed railway scenario. Aiming at the deficiency of the common event A3handover judgment criteria mechanism, two kinds of novel handover judgment algorithms based on position information of the UE and pre-bearer mechanism of target eNodeB is proposed. These algorithms could improve system handover performance and reduce the possibility of Radio Link Failure (RLF) and eliminate the deficiency of Ping-Pong Handover (PPHO) at the same time. And the signalling flow chart of TD-LTE system has been optimized. System level simulation results represents both handover algorithms could greatly improve the success rate of handover and shorten the coverage of handover area while system level simulation demonstrates that in overcoming inter-cell interference and improving signal transmission quality, both algorithms are also proved to be effective.The fourth part of the thesis mainly studies Soft Handover (SHO) algorithm of TD-LTE system under the high-speed railway scenario. Summarizing the aforementioned the deficiencys of several Hard Handover (HHO)-mechanisms, a SHO algorithm of TD-LTE system is proposed according to the characteristics of high-speed railway special network of TD-LTE. Moreover the signalling flow chart of TD-LTE system has been redesigned to support the soft handover of TD-LTE system.The system level simulation demonstrates that this algorithm could solve the deficiencies of call drop and communication interrupt better during the whole handover procedure and reduce handover failure rate.