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Q. Fu:
"Active RFID for Positioning Using Trilateration and Location Fingerprinting Based on RSSI";
Talk: ION GNSS 2008 Conference, Savannah, Georgia, USA (invited); 2008-09-16 - 2008-09-19; in: "ION GNSS 2008 Conference", (2008), 14 pages.

This paper describes the current research work in the project UCPNAVI (Ubiquitous Carthograpy for Pedestrian Navigation) and outlines the methods and obtained results by using active RFID (Radio Frequency Identification) for positioning. The key aim of the work package `Integrated Positioning´ in the project is to investigate alternative location methods using active RFID for positioning in areas where no GNSS position determination is possible due to obstruction of the satellite signals. For this purpose, three methods are introduced in this paper. In most RFID applications positioning is performed using cell-based positioning. RFID tags can be installed at active landmarks (i.e., known locations) in the surroundings and the user who is equipped with an RFID reader can be positioned using cell-based positioning. The positioning accuracy, however, depends on the size of the cell defined by the maximum range of the signal. Using long range RFID for positioning the cell size can be quit large, i.e., up to around 20 m. Therefore, the paper proposes two new methods for positioning, i.e., trilateration und location fingerprinting based on received signal strength indication (RSSI) if more than one RFID tag can be seen. The trilateration approach is based on the deduction of ranges to the RFID tags from RSSI. An iterative approach to model the signal propagation will be introduced, i.e., the ITU (International Telecommunication Union) indoor location model that can be simplified to a logarithmic model, and a simple polynomial model are employed for the signal strength to range conversion. In a third attempt, location fingerprinting based on RSSI is tested. In this case, RSSI are measured in a calibration phase at known locations inside the building and stored in a database. In the positioning phase this measurements are used together with the current measurements to obtain the current location of the user. For the estimation of the current location different approaches are employed and tested, i.e., a direction-based approach, a tag-based approach, a direction-tag-based approach and a heading-based approach. Using fingerprinting usually positioning accuracies on the few meter level can be achieved. The concept and the iterative approach of the different methods and test results are discussed in this paper.

Project Head Georg Gartner:
Ubiquitäre Kartographie für Fußgängernavigation