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The Assisted GNSS, Technology and Applications

The location based services takes more and more importance. Several methods to locate any users through mobile telephony have been evaluated. Among these techniques Assisted GPS appears to be a very promising one. The challenge of this technique is to propose to locate any user of mobile telephony with a very high availability of service. The expansion of such a technology was first driven by regulation issues known under the E911 law dedicated to provide a location mean to the emergency calls. After this first impulsion, many services flourished. The requirements bending on this location service leads to design GPS receivers with a far higher sensitivity than what can be found on standard GPS receivers, typically with a location capability in indoor environments. This high level of sensitivity is reached thanks to the assistance broadcast by the telecommunication network. The near arrival of Galileo allows a dramatic improvement in terms of both sensitivity and accuracy of Assisted GNSS techniques. The present paper first reminds the functioning of the Assisted-GPS techniques, and the basics interest to enlarge this to a A-GNSS concept including the use of both constellations GPS+Galileo. It will be first presented a description on the on-going activities to have the A-GNSS technique fully standardized in the 3GPP and OMA standardization bodies. Our intent and proposed planning for such an inclusion in current standards documents is explained, as well as the achieved results. Besides, the paper then shows that the interest does not only rely on the increase of the number of visible satellites, but also on a Galileo signal really optimised for A-GNSS location services, in difficult environments (Urban Canyons and indoor) while being designed to meet the processing constraints of low cost user terminals. The improvement is especially noticeable in non synchronous cellular networks such as GSM, compared to synchronous network such as IS95 or CDMA2000.