Buses Positioning Based On The Mobile Phone Location Estimation

The best means to resolve traffic problems is developing intelligent public traffic system(IPTS), positioning and tracking of buses is a crucial technology in IPTS, and it is the base of acquirement and dissemination of public traffic information, administration of public traffic system, and programming of bus routes. Because of the dense buildings and vehicles in the city, there is much disadvantage, for instance, large investment of infrastructure and positioning equipment, long-term construction, high working cost, fallibility of positioning accuracy and stability, when we utilize the traditional automatic vehicle location(AVL) technology, such as signpost, dead reckoning, global positioning system(GPS) and so on, to estimate the location of buses. Positioning by cellular phone is a new location estimation technology occurring with the development of mobile communication, location estimation is engaged by the character parameters of signal. By contrast with traditional AVL technologies, although mobile phone positioning has lower accuracy, there is much disadvantage to utilize it in IPTS, such as little investment, low working cost, easy system maintenance and so on. The article proposed a bus positioning scheme based on mobile phone positioning technology, and improve the accuracy of bus positioning through the study on TDOA location error and corresponding map match algorithm. The article firstly introduced various AVL technologies currently used in IPTS, by contrast with mobile phone positioning technology, analyzed their merits and shortcomings and proposed that TDOA location estimation technology is used to locate the buses. On the basis of analysis of the principle of TDOA location estimation and the feature of signal propagation in mobile communication environment, taking the system errors and environmental errors into account, we established the statistical model of TDOA error, and proved it is available by experiment. Utilizing the model of TDOA error, we proposed the method of acquiring distribution of location error and error ellipse. Then, we studied the effect on distribution of location error due to the relative location of mobile phone and base stations and combination of base stations, and the statistical rules of the distribution of location error in error ellipse. Finally, we designed the architecture and functional module of the buses positioning system based on the TDOA location estimation, studied the algorithm of buses map matching based on the distribution of TDOA location error, and proved it is available and advantageous in minimizing location error of buses.