Resarch On The Influence And Optimizations Of The GSM-R Handover Failure In CTCS System

GSM-R is represented for the Global System for Mobile Communication Railway forshort, and takes on the task of communicating the railway controlling digital signal, which isdirectly related to the safety of the railway. It is necessary to study the handover methodbecause of it is important for communication of onboard-trackside link data in GSM-R system.The hard handover was used in GSM-R system, which could lead to the short interruptions. Ifthere are several problems happened （serious interruption, reasonable parameter, andswitching algorithm） at the same time, it will result in ping-pong handover, even drop words.That has great influence on the security and validity of GSM-R system. Therefore, it isnecessary to research on the handover method. The thesis determines the target cell ofhandover, and studies the handover algorithm basing on the estimation of power.Firstly, the thesis presents the research status, trend of development and the keytechnique of switching of GSM-R and CTCS, and explores the importance of handovermethod of GSM-R system, and introduces the status quo and main problems of handover,then analyses the disabled handover process and principle of handover from the signaling. Bythe control of CTCS-3system to the QoS of GSM-R and onboard-trackside link of CTCS-3system, the thesis analyses the influence of disabled handover method to the CTCS-3system.The result shows the disabled handover will lead to the trains delayed.Secondly, pending handover target cell is positioned in the cell of the same levelaccurately in the selective phases of handover, by setting different handover priority of everycell, basing on the traditional single-layer network to decide the direction of railway andneighbour cells list, and combining with antenna position of base station in the realitycondition and double-layer network. The target cell is located in the same level to avoid ofhandover in the same level under normal condition; and it can switch into the reserved leveltimely under the relegated condition. The simplified neighbour cell list is presented bydeciding the direction of railway and pending handover target cell, which can reduce thereadiness time of handover and improve the success rate of handover.Finally, on the basis of above research, the thesis analyses the wireless channel model ofrailway, traditional handover algorithm and the early handover algorithm basing on powerestimation. The two simulation models of two cells were built by using Matlab simulationsoftware, considering three factors: switching times, speed of railways and capability ofswitch, and improving the early handover algorithm. The result shows that this algorithm canprompt system performance more effectively than previous algorithm.