[G05-1] Indoor and outdoor navigation

[G05-1-01] Constrained Differential Wi-Fi and UWB Measurements for Indoor Cooperative User Localization

Guenther Retscher¹, Hannes Hofer¹, Allison Kealy², ^○Vassilis Gikas³, Andreas Ettlinger¹, Franz Obex⁴ (1.TU Wien Vienna University of Technology, Vienna, Austria, 2.The University of Melbourne, Melbourne, Australia, 3.National Technical University of Athens, Athens, Greece, 4.Freelancer, Vienna, Austria)

Many personal mobility scenarios require the localization of users within a group or neighbourhood. A solution to this problem is Cooperative Positioning (CP) where the end user localization is performed using its own measurements plus any additional information coming from neighbouring users in the form of inter-nodal ranges or other means. In this study, new differential Wi-Fi positioning approaches based either on DGPS or VLBI are applied for (tri)lateration. By the use of reference station (RS) observations the received signal strength (RSS) measurements of the access points (APs) is corrected to reduce short- and long-time variations of the RSS at the user side. A low-cost implementation is realized using a number of Raspberry Pi units, which serve simultaneously as both APs and RSs emitting and scanning Wi-Fi signals. For the data collection a smartphone application (Android App) has been developed. Furthermore, the use of UWB and its combination with Wi-Fi is investigated to form a networked solution. In the practical evaluation, static and kinematic tests using six users carrying different smartphones are conducted in an indoor lab of approximately 400m2. Five Raspberry Pi's served as reference stations and APs together with another three additional Wi-Fi routers. One user enabled the hotspot function on his mobile device so that the other users can measure the RSS to derive inter-nodal ranges. Additional five UWB units were carried by the users serving as either a reference for the derivation of the inter-nodal ranges or in order to be integrated into the overall positioning solution. Ground truth for these experiments was measured using a robotic total station. It is proven that both DWi-Fi approaches outperform conventional RSS lateration and the integration with UWB further strengthens the CP solution.