Talks and Poster Presentations (without Proceedings-Entry):

G. Retscher:
"Differential Wi-Fi - A New Opportunity for Localization of Individuals and Groups of Smartphone App Users";
Talk: Curtin Spatial Science Colloquium 2018, Perth, Australia (invited); 2018-04-05.

English abstract:
An increasing number of personal mobility scenarios require the localization of individuals or a group of end users within a group or neighbourhood. Not rarely, this is the case in adverse operating conditions where only limited positioning information is available. Usually the currently achievable positional accuracy of tracking (groups of) persons is not sufficient. A solution to this problem is referred to as Cooperative Positioning (CP). In CP, end user localization is performed using its own measurement data plus any additional information coming from neighbouring users in the form of inter-nodal ranges or other means.
In this study, absolute indoor localization of a user group is enabled with a novel differential Wi-Fi (Wireless Fidelity) positioning approach. Similar to Differential GPS (DGPS), the received signal strength indication (RSSI) measurements of the Wi-Fi access points (APs) is corrected to reduce short- and long-time variations of the RSS at the user side by the use of reference stations. A low-cost implementation is realized using a number of Raspberry Pi units, which serve simultaneously as both APs and reference stations emitting and scanning Wi-Fi signals. In addition, continuous positioning is achieved by integration of other smartphone sensors, such as accelerometer, magnetometer, gyroscope and barometric pressure sensor.
In the practical evaluation, static and kinematic tests using a number of users carrying different smartphones were conducted in an indoor lab setting and combined out- and indoor environment. In the second case the transition between GNSS positioning and Wi-Fi indoors could also be investigated. One user enabled the hotspot function on his mobile device so that the other users can measure the RSSI to derive inter-nodal ranges. It could be proven in both use cases that the new CP DWi-Fi approach outperforms conventional localization algorithms due to a significant improvement of the indoor positioning and tracking accuracy.
As a typical use case, the localization and guidance of individuals and user groups in multi-modal transportation networks and interchanges using the newly developed smartphone App is discussed at the end of the presentation.

Created from the Publication Database of the Vienna University of Technology.