An overview of the challenges and progress in meeting the E-911 requirement for location service
IEEE Communications Magazine
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The topics presented in this article are related to 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 respect to traditional methods such as local loop data and GPS-based floating car data (FCD), this method (floating phone data, FPD) will take advantage of area-wide availability without additional infrastructure and costs. The timing advance (TA) value and signal strength measurements to the serving antenna are available in the GSM network, as well as signal strength measurements to up to six neighbouring antennas. 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 a base for modern traffic control and management. Within this article a brief overview of the project is given, with the main focus being on the positioning methods. Different approaches based on least squares adjustment and Kalman filtering are presented and first results from data measured in the vicinity of the city of Stuttgart are presented.