2005 RoboticsbasedLocationSensingUsi

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802.11, wireless networks, mobile systems, physical localization, probabilistic analysis


A key subproblem in the construction of location-aware systems is the determination of the position of a mobile device. This article describes the design, implementation and analysis of a system for determining position inside a building from measured RF signal strengths of packets on an IEEE 802.11b wireless Ethernet network. Previous approaches to location-awareness with RF signals have been severely hampered by non-Gaussian signals, noise, and complex correlations due to multi-path effects, interference and absorption. The design of our system begins with the observation that determining position from complex, noisy and non-Gaussian signals is a well-studied problem in the field of robotics. Using only off-the-shelf hardware, we achieve robust position estimation to within a meter in our experimental context and after adequate training of our system. We can also coarsely determine our orientation and can track our position as we move. Our results show that we can localize a stationary device to within 1.5 meters over 80% of the time and track a moving device to within 1 meter over 50% of the time. Both localization and tracking run in real-time. By applying recent advances in probabilistic inference of position and sensor fusion from noisy signals, we show that the RF emissions from base stations as measured by off-the-shelf wireless Ethernet cards are sufficiently rich in information to permit a mobile device to reliably track its location.

... While these were good fits for hallways 1 and 2, they failed to model the noisiness of the static localizer on hallways 3 and 4. A conditional probability function trained to the actual points would likely provide better results. Page 9. …



 AuthorvolumeDate ValuetitletypejournaltitleUrldoinoteyear
2005 RoboticsbasedLocationSensingUsiAndrew M. Ladd
Kostas E. Bekris
Algis Rudys
Lydia E. Kavraki
Dan S. Wallach
Robotics-based Location Sensing Using Wireless Ethernet10.1007/s11276-004-4755-8