Hybrid Positioning using GPS and GSM Ranging Measurements

Etienne Favey, Daniel Ammann and Clemens Burgi

Abstract:	Using mobile phone signals for positioning in conjunction with GPS in a truly hybrid positioning solution sounds promising, as one type of signal tends to be better available where the other one is scarce. In Europe, Global System for Mobile Communication (GSM) networks are generally of wide use. An approach to use GSM base stations as pseudolites together with GPS L1- only measurements will be presented, already enabling positioning when the sum of GPS and GSM measurements is three or higher. The pseudolites’ position and clock parameters are received via the mobile communication link from a database within the GSM network. Apart from a serial communication link between the mobile phone part and the GPS receiver, a clock synchronization line is used in order to merge the measurements from the different wireless systems. The GPS measurements used are state of the art pseudorange measurements. The GSM part provides observed time difference (OTD) measurements. In an indoor environment where no GPS signals are received, the positioning relies solely on the OTD measurements, whereas in a rural area with scarce or no mobile communication network coverage, the posititioning is based on the GPS measurements. In suburban areas, a hybrid position result evaluating both OTD and GPS measurements may be calculated, when either system on its own would fail. Within the scope of the EMILY-Project, funded by the fifth framework program of the European Commission, a testbed has been realized. The concept of a truly hybrid positioning solution in various environments has been studied. First results from field trials regarding accuracy and availability of position solutions are presented.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1918 - 1923
Cite this article:	Favey, Etienne, Ammann, Daniel, Burgi, Clemens, "Hybrid Positioning using GPS and GSM Ranging Measurements," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1918-1923.
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