LBS, Positioning


Active RFID trilateration for indoor positioning

May 2008 | Comments Off on Active RFID trilateration for indoor positioning

Guenther Retscher and Qing Fu

Conclusion and outlook

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This paper addresses the investigation of RFID trilateration for indoor positioning. At first some background of RFID was introduced. On this basis it was deduced how the measured signal strength can be converted into a distance. The converted distances could be used for determining the position of the reader by means of trilateration. Finally, the approach was tested in a test environment near the Vienna University of Technology.
For the signal strength to distance conversion a polynomial model was employed. Signal strength measurements were performed on baselines with a point interval of 2 m. The resulting mean value of the residuals in the conversion of the signal strength into a distance is nearly zero (i.e., below ± 2*10-11 m) using a polynomial model with an order of p = 3. These polynomial models were then used for the deduction of ranges to the tags for the location of points in static and kinematic tests. In the static test the test points were located with an accuracy of better than ± 0.35 m in X-direction and ± 1.44 m in Y-direction. In the kinematic tests lower accuracies in the range of ± 2 to 3 m were achieved, but the trend of the moving user was always determined correctly. The achieved positioning accuracies have proven that RFID trilateration can be successfully employed in a small range to the tags.
In the future, we will perform more experiments to improve the polynomial models for signal strength to distance conversion. At the same time the algorithms will be tested in a larger and complicated environment and with more tags.

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Acknowledgements
This research is supported by the research project P19210-N15 “Ubiquitous Carthograpy for Pedestrian Navigation (UCPNAVI)” founded by the Austrian Science Fund (Fonds zur Förderung wissenschaftlicher Forschung FWF).

References
Finkenzeller K., 2002. RFID Handbook: Fundamentals and Application in Contactless Smart Cards and Identification, Carl Hanser Verlag, Munich, Germany.

* Fu Q., 2008. Active RFID for Positioning Using Trilateration and Location Fingerprinting Based on RSSI. in: Papers presented at the ION GNSS 2008 Conference, September 16-19, 2008, Savannah, Georgia, USA, CD-Rom Proceedings.

* Ranvier S., 2004. Path Loss Models, S-72.333 Physical Layer Methods in Wireless Communication Systems, Postgraduate Course on Radiocommuications, Helsinki University of Technology, SMRAD Centre of Excellence, http://www. comlab.hut.fi/opetus/333/ 2004_2005_ slides/Path_loss_models.pdf (Last date accessed: April 2008).

* Retscher G., Q. Fu, 2007a. Integration of RFID, GNSS and DR for Ubiquitous Positioning in Pedestrian Navigation. in: Papers presented at the ION GNSS 2007 Conference, September 25-28, 2007, Fort Worth, Texas, USA, CD-Rom Proceedings.

* Retscher G., Q. Fu, 2007b. Using Active RFID for Positioning in Navigation Systems, in: Papers presented at the 4th Symposium on Location Based Services and Telecartography, November 8-10, 2007, Hong Kong, PR China.

* Retscher G., Q. Fu, 2008. RFID Trilateration for Indoor and Outdoor Positioning, in: Papers presented at the European Navigation Conference ENC-GNSS 2008, April 22-25, 2008, Toulouse, France.

* Wikipedia, 2008. ITU Model for Indoor Attenuation, see http:// en.wikipedia.org/wiki/ITU_Model_ for_Indoor_ Attenuation (Last date accessed: April 2008).

 

Guenther Retscher

Ass.-Prof, Institute of Geodesy and Geophysics,
Vienna University of Technology
gretsch@pop.tuwien.ac.at
   

Qing Fu

Research Assistant,
Institute of Geodesy and Geophysics, Vienna
University of Technology
Fu@mail.zserv.tuwien.ac.at
   
     
 
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