EFFECTS OF LEAKY WAVEGUIDE ON THE CONTROL PERFORMANCE OF COMMUNICATION BASED TRAIN CONTROL SYSTEM BASED ON PATH-LOSS MODEL

Abstract

In urban rail transit, systems using communication based train control (CBTC), it uses high accuracy of train locating, realizes a continuous automatic train control system. High resolution of locating the train permits the high line capacity and fewer Infrastructures is required than Track circuit based system therefore all over the world countries have more concerned about this technology. DCS system plays an important role in the information interaction between ground equipment and vehicle equipment in CBTC. DCS is WLAN which is short range radio networks based on IEEE 802.11, complete communication network is built with many closely deployed AP (Access Point). IEEE 802.11b is a physical layer amendment for operation in the 2.4 GHz band, adopted in CBTC system in which data transmits at 11Mbps and uses DSSS modulation. Data communications systems based in the 2.4 GHz ISM band has raised the concern of RF interference between CBTC equipped trains and the variety of new and existing users of this band. The reliability and safety of information transmission can be improved when leaky waveguide is used as transmission medium of train-ground wireless communication in CBTC (Communication Based Train Control), also it can provide better performance and stronger anti-interference ability than free space. These benefits of leaky waveguide insisting the research scholar of communication field to intervene in CBTC system. Wireless LAN technologies are adopted in most train wayside communication systems in CBTC. Successful handoff plays an indispensable role in wireless communications. Running through the large wireless networks with numerous APs in urban mass transit, a train equipped with CBTC systems inevitably encounters the problems of handoff. Against the possibly negative phenomena such as Ping-Pong effect, handoff delay, packet loss and so on. Frequency Combination and Location based Handover scheme are analysed, both handover scheme are also correlated with Leaky waveguide based CBTC system. After analysis, it is realized that Location Based Handover Scheme is best suited for Leaky waveguide based CBTC system in many aspects. Leaky waveguide also limits the implementation of various handover schemes.