Bluetooth Sensor Network Positioning System with Dynamic Calibration

Positioning systems based on sensor networks is one of the most promising fields in mobile computing. This paper considers the Bluetooth standard to locate devices using the RSSI (Received Signal Strength Indicator). The major problem of working with this parameter is its fluctuation that happens very fast due to changes in the environment. These changes can be caused by humidity or temperature, presence and movement of people, opening and closing of doors, multipath effect, etc... This paper introduces an innovative approach that uses the RSSI information between several fixed wireless beacons to improve the reliability of a Bluetooth positioning system. This information is used to calibrate the sensor responses. The results of several experiments illustrate how the real time calibration improves the precision and the stabilization of the position estimations. Moreover, we show the improvement obtained when increasing the number of beacons.