Research On Coexistence Of CBTC System And PIS

CBTC (Communication Based Train Control) can ensure the safe operation and improve the efficiency of rail vehicles by controlling and supervising running trains in real time, which is a safety critical system. PIS (Passenger Information System) transmits service information to passengers through on-board and ground display equipment, which are based on multimedia network and computer technology. In most urban railway systems, WLAN (Wireless local area network) based on IEEE 802.11 is used as the main technology in train ground communication in both CBTC system and PIS.However, PIS works at 2.4GHz or 5.8GHz, and it interferes with the normal train ground communication even safety of CBTC which works at 2.4GHz. Because PIS is popular and becoming the indispensable part of subway systems, it is important to study and resolve the problem rightly. The purpose of this paper is to study the coexistence of PIS and CBTC Syetem and analyse the most reasonable coexistence of two systems through theory and simulation.Firstly, the thesis introduces the data communication sub-system and standards of WLAN. The functions, structure, communication techniques and bandwidth requirements of PIS are briefly referred.Secondly, it is discussed that how interference is produced to CBTC by PIS. The parameter'interference factor'is introduced and a quantitative analysis for the interference between different channels is given, which provide theoretical basis for modifying interference noise between channels in modeling. Besides interference factor, the thesis proposes a more suitable method to calculate the SINR of real system, and simulation results are also given.Then, OPNET is introduced, which includes the modeling method, communication simulation mechanism, etc. The modeling method of CBTC system and PIS using OPNET is introduced and the modeling theory of PIS source and important modifications of Pipeline are also described in this chapter.In the next chapter, different scenarios of the coexistence of CBTC system and PIS are simulated, which include interferences between cochannel and adjacent channel and interferences between 802.11g and 802.11a, and simulation results are analysed. Actual testing results are given and it is shown that they are in accordance with the simulation results.Finally, the thesis summarizes and gives the reasonable method to decrease the interference caused by PIS according to simulation and analysis results. And some guidance to practical engineering is given.