Mobile positioning for traffic state acquisition

The topics presented in this paper regard the project “Data Optimisation for integrated Telematics” (Do-iT) granted by the German ministry of economics and technology. Within this project the current traffic state will be derived by use of network-based data from numerous mobile phones of anonymous drivers. With regard to traditional methods like local loop data and GPS-based floating car data (FCD) this method (floating phone data, FPD) will take advantage of the area-wide availability without additional infrastructure and costs. The Timing Advance (TA) value to the serving antenna and signal strength measurements to the serving antenna as well as the six neighbouring antennas are available in the GSM network. The TA value is used to determine the distance from the serving antenna to the mobile phone. From this a search area is generated. The position of the mobile phone is determined by use of the signal strengths which are matched to a signal strength map. These positions are referenced to the digital road network. Positioning is used to enable a reliable traffic prediction as base for modern traffic control and management. Within the paper a brief overview about the project is given. Main focus is on the positioning methods. Different approaches from least squares adjustment and Kalman filtering are presented and first results from data measured in the vicinity of Stuttgart are shown.