Keeping a Stand-Alone Receiver on the Road in Hard Urban Environment

Joel Brenner, Andrea Di Cintio and Angelo Genghi

Abstract:	This paper addresses the problem of measurements reliability and multipath mitigation for stand-alone GPS navigation in hard urban environment. NemeriX is a Swiss-headquartered fabless semiconductor company focusing on low-power, high performance GPS chipsets. The target markets are primarily those requiring high-energy efficiency (e.g., battery powered), specifically wireless and handheld. Our GPS solution (NJ1030) has met user expectations in almost all the environments, as far as accuracy, dynamic response, sensitivity and acquisition performances are concerned. However the overall system behavior (GPS receiver coupled with Mapping software) becomes less effective, depending on the GPS constellation visibility, when the user approaches the so-called "Hard Urban Environment", typical of downtown areas of many big cities. In these areas, where the measurement errors are largely dominated by multipath, the receiver can exhibit large position drifts, i.e. comparable to streets separation. The final impact on user experience is even worse due to the mapping software. The majority of the current mapping software rely on a small set of NMEA messages, and in the search for the most likely street they normally do not merge the information about the accuracy of the position solution with the map information. The results, in area characterized by poor visibility and strong multipath, are continuous and annoying jumps of the displayed position from road to road. In the frame of continuous improvement in navigation solution, especially in such environments, a study has been promoted with the objective to provide a position solution whose quality and availability are effective for personal navigators also in hard urban environments. The paper begins with an introduction defining the mid and hard urban environments, and continues showing examples of typical behaviors in these situations for receivers not implementing multipath detection and mitigation techniques, as well as for receivers embedding them. The main issues that arise in these operating conditions will be derived, and analysis of their advantages and drawbacks will be presented.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	2649 - 2660
Cite this article:	Brenner, Joel, Di Cintio, Andrea, Genghi, Angelo, "Keeping a Stand-Alone Receiver on the Road in Hard Urban Environment," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 2649-2660.
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