Research On Time Synchronization Technology Of TDCS/CTC System Based On Network Time Protocol

Railway signal system is an important safety related system in the railway systems. It’s very important for the time synchronization of clocks to find the fault location and fault source. As the time synchronization center of all the signal subsystems, train operation dispatching command system/centralized traffic control(TDCS/CTC) affords time message to all the other signal subsystems. Therefore, time synchronization and synchronization accuracy of TDCS/CTC system become especially important. The TDCS/CTC system is selected as the research object and the time synchronization of the system is studied in the thesis. For the reason that the failure analysis of the accident is affected by the accuracy of time synchronization and the wide distribution of TDCS/CTC system, the requirement of the time synchronization accuracy is high. In consequence, it’s very important to choose an appropriate technology of time synchronization. From the perspective of the cost and precision of time synchronization, the network time protocol(NTP) and global positioning system(GPS) technology are employed in the thesis for the time synchronization of TDCS/CTC system. It is because that the NTP technology costs little but the synchronization precision is low under the circumstance which there is no external standard time source and the time synchronization precision of GPS technology is high, but the cost is too much.According to the structure and function of the railway time synchronization network, the TDCS/CTC system synchronization scheme is designed combined with the interfaces of the system in the thesis. Further more, the time synchronization algorithm of the system is designed and the result of the time synchronization accuracy is verified through simulation.Firstly, the structure of the railyway time synchronization network is analyzed. By means of studying the interfaces between the TDCS/CTC system and the other signal subsystems, and the transmit path of the time message, the time synchronization scheme of the TDCS/CTC system of existing railway line and passenger railway line are designed.Secondly, the time synchronization algorithm of multi-server mode and single-server mode are designed respectively. In order to improve the accuracy of time synchronization, the improved time synchronization algorithms for the two modes are proposed in the thesis. For multi-server mode, screening algorithm and reordering algorithm are employed to improve the normal time synchronization algorithm which can improve the accuracy of time synchronization by means of choosing the best server in the process of time synchronization. For single-server mode, data packet selecting algorithm is adopted to improve the normal time synchronization algorithm which can improve the accuracy of time synchronization by means of avoiding the long waiting time of the data packet.Finally, the appropriate synchronization intervals of the railways bureaus and railways stations are set firstly according to the condition of the network delay. Then the normal time synchronization algorithms and improved time synchronization algorithms of multi-server mode and single-server mode are simulated according to the synchronization intervals. The results of the simulation show that the improved time synchronization algorithms of TDCS/CTC system can improve the accuracy effectively.