Study On Communication Guaranteeing Mechanism In CBTC System Based On WLAN

The subway is believed to be the best solution for solving traffic congestion in the large cities and got large-scale construction in recent years in China. After investigating the available CBTC system, this paper focuses on design an effective communication guaranteeing mechanism for those based on WLAN. Directional antennas are chosen for the propagation environment of tunnels. Inspired by Multiple antenna technology, the double card wireless equipment wireless network architecture scheme is designed and the possible problems of CBTC system application are analyzed. Simple mathematical model are used for the mechanics analysis and movement analysis of subway trains. Inherent defect of the traditional roaming mechanism are presented clearly and a new fast roaming mechanism are adopted. The double network cards cooperate with each other in master-slave mode to reverse join threshold and roaming threshold so that the handover delay of master card is reduced greatly. Regardless of the moving direction, the results of matlab simulation verify that the new fast roaming system has absolute advantage over the traditional roaming mechanism in reducing the period without connection nearly a half and that the cumulative resident time is more close to the ideal result.