Indoor Location Positioning Using Radio Signal Strength

We report on the development of a wireless reference system that produces long-term position estimates to enhance the accuracy of a reference-location positioning system used in a novel method for tracking a slowly moving cart in an indoor environment. The new tracking method employs an inertial navigation sensor (INS) and a reference-location positioning system. The latter comprises accelerometers and a gyroscope whose measurements are processed to derive short-term position estimates. On the other hand, the reference system is required to provide long-term estimates that prevent the drifts inherent to short-term estimates. Both types of estimates can be efficiently combined using a Kalman filter to obtain accurate position information.

This report is organized as follows. We first describe the concepts involved in location positioning using received signal strength such as the signal attenuation model, the approximation of transmitter-receiver distance and the received signal power estimation. Then, we present as an exemplary wireless reference system the solution that we use to validate these concepts experimentally. Finally, we discuss the results of our measurement campaigns with emphasis on the location positioning accuracy.

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By: Pedro Coronel, Wolfgang Schott and Beat Weiss

Published in: RZ3659 in 2006

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