Research And Design Of The DCS Subsystem In Subway’s CBTC Signal System

With the development of Urban social economy in China, traffic congestion is becoming increasingly serious in most tier one and tier two cities. Urban rail, which is able to provide high transportation volumes, with high speed, safety, punctuality, environmental protection, energy conservation and low land usage, is playing a very important role in mitigating the press of the city transportationCBTC (Communications Based Train Control) is a safe system based on wireless communication with high reliability and stability. This system enables train positioning control information delivered in real time by using modern communication technology to realize bidirectional communication between the train and the ground facilities, rather than using traditional track circuit to send information to the on-board equipment, thus dramatically reduce the interval between two trains, improve speed, and increase transport efficiency.Data Communications System (DCS) serves as the transmission nerve in CBTC System by providing a bidirectional, reliable and secure data Switching between the subsystem in CBTC system, Operation Control Center(OCC), depot, parking lot, railway stations along the line and train-ground facilities.The background and significance of the topic is firstly introduced by this paper,the importance of DCS system in CBTC system is illustrated,the practical significance of China’s urgently research on each subsystem in CBTC system including DCS system’s key technology research and localization reform is proposed according to the present development in this field at home and abroad. Backbone network and wayside data access network in DCS system is designed and researched. Compare differences between SDH ring network with RPR ring network, elaborated the principles and advantages of RPR ring network.Train-ground wireless bi-directional communication is key technology for DCS system. This paper focuses on anylyzing the application strength and weakness of the mainstream wireless communication technology and wireless transmission medium, and proposes the WLAN solution according the practical situation of the subway. As the safety of DCS system is very important, this paper enumerates types of potential security threats in DCS system, ensuring the information transmission safety of CBTC system by studying the 802.11i agreement and error control coding technology. Based on practical experience, a WLAN environment is built for a suite of WLAN technology experimental tests:field strength, bandwidth, switching, CBTC flow support, interference testing, proving that it can satisfy the requirement of subway CBTC system both for reliability and usability.