Study On The CBTC Signal Enhancement Based On Existing Telecommunication Wireless Coverage System

With the development of urban rail transit signaling technology, Communication-Based train control system is developing to a mainstream of subway signal control technologybecause of its high precision, moving block, automation degree high and high-capacity two-way communication characteristics.The difference between CBTC and traditional train signal control system is that CBTC based on wireless wideband and real time communication system. Through the communication system, train control system can obtain all subway and train status information in realtime from communication subsystem.So as to achieve high accuracy and dynamic control, and improve the efficiency and safety of the train. Then position of the communication system in CBTC system determine the importance of communication system, once the communication system instability, the control system will not be able access to the train and subway state information to timely and accurately, the control system have to back to low level control, even have to stop train.Unfortunately, there is no enough attention paid to the stability of communication system. This paper try to find a new technical and engineering solutionusing public wireless coverage system to enhance the stability of CBTC, then analyze the feasibility, key technology and verify the solution via a project. The main contents are as follows:1. The effect of communication subsystem reliability on the whole CBTC system is expoundedby analyzing the composition of CBTC system. The typical problems and potential risks of CBTC wireless signal are founded by further analyzing both the general characteristics and the characteristics in metro space. In particular, the waveguide effect, the car body loss and the compression effect of the wireless signal are analyzed.2. The technical characteristics and composition of public wireless coverage system is briefly introduced.The solution of using wireless coverage system to enhance CBTC signal is proposed. Some key technology like the band compatible, signal combination and amplification, signal filtering and isolation are also discussed.thenthe feasibility analysis, proof of principle and impact on the existing system analyzed. At last, combined with the author’s practical experience, some practical engineering design for subway tunnel environment also introduced.3. Effect is verified relying on the "Mexican subway CBTC signal enhancement test project". The feasibility and result of the solution is verified by comparing the index of RSSI, PingAC delay and PingAC package loss rate that before and after combing CBTC signal to public coverage system.Finally, the conclusion is drawn that the solution is feasible, effective and with low cost.