Cooperative Localization in Indoor Environments Using Constrained Differential Wi-Fi and UWB Measurements

Guenther Retscher, Hannes Hofer, Allison Kealy, Vassilis Gikas, Franz Obex

Peer Reviewed

Abstract:	For Wi-Fi positioning usually location fingerprinting or (tri)lateration are employed whereby the received signal strengths (RSSs) of the surrounding Wi-Fi Access Points (APs) are scanned on the mobile devices and used to perform user localization. Within the scope of this study, localization of an individual user or a group of users within a neighborhood is achieved using an integrated solution with Wi-Fi positioning and inertial navigation (IN). Differential approaches termed DWi-Fi are developed either in analogy to differential GNSS or Very Long Baseline Interferometry (VLBI). They make use of a network of reference stations (RSs) deployed in the area of interest on which continuous RSS observations are performed leading to correction parameters for the users in real-time which consider temporal and spatial variations of the Wi-Fi RSSs. Then path loss model errors for the RSS to range conversion are eliminated by differencing model–derived ranges from the same AP. Similar as in a CORS GNSS network a network solution is proposed where Flächenkorrekturparameter (FKPs) are derived using areal modelling. Furthermore, the detection of selected waypoints along a trajectory is performed for the integrated navigation solution. These waypoints serve as a position estimation update for the IN and are therefore referred to as intelligent checkpoints (iCPs). Also, this study introduces the concept of using Ultra-wide Band (UWB) technology as a means of supporting the Wi-Fi solution through dedicated checkpoints of higher positioning accuracy given its high accuracy potential and the continuously decreasing system cost. A number of tests have been undertaken to examine the validity and the potential of this approach and results of the analyses are presented. It could be proven that all major user requirements (i.e., positioning accuracy, availability, continuity) are being met. The full experimental schemes, practical results and algorithms developed are detailed in this paper.
Published in:	Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) September 25 - 29, 2017 Oregon Convention Center Portland, Oregon
Pages:	2869 - 2882
Cite this article:	Retscher, Guenther, Hofer, Hannes, Kealy, Allison, Gikas, Vassilis, Obex, Franz, "Cooperative Localization in Indoor Environments Using Constrained Differential Wi-Fi and UWB Measurements," Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 2869-2882. https://doi.org/10.33012/2017.15160
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