Research Of Virtual Balise Based On GNSS

Balise is the main positioning device in China Train Control System. But massively deployed balises along the track to achieve higher precision will add system construction and maintenance cost. It has realistic significance if train positioning precision and the reduced number of actually deployed balises can be both guaranteed.With the development of Global Navigation Satellite System (GNSS), some countries begin to conduct Virtual Balise(VB) research based on GNSS. The main aim is to realize balise all functions by using GNSS receiver and related software. A VB can perform just like an actual balise on trackside. On the basis of analyzing VB functional requirement and system architecture, VB sub-system architecture and requirement and status transfer and software is designed and implemented. The research is emphasized on train map matching algorithm and VB capturing time. After analyzing the relations among VB position error, position output frequency and train speed, VB optimization capturing algorithm is proposed. Assume that GNSS receiver is working correctly and a train moves to a reference point on the track (VB point), VB system can perform real-time map matching and capture optimized VB point to generate certain message with the same format as a actual balise and send to the BTM. So that VB has the same interface function as a regular actual balise.The function of VB is realized by using Visual C++6.0 and active control called MapX. Software function has been validated by Tibet railway data, appointed VBs can be successfully captured and related VB function is realized.