Wireless Indoor Positioning: Effective Deployment of Cells and Auto-Calibration

Precise wireless indoor location is currently an important challenge. Triangulation techniques used for external locations are useless due to adverse effects like the lack of line of sight or multipath. Fingerprinting methods, based on the comparison of Received Signal Strength values measured by the mobile phone with a radio map of RSSI Recorded during the calibration phase, arise as the best methods for indoor scenarios. However, they are also affected by problems like channel variability. In this paper, we propose two ways to improve the systems based on fingerprinting methods. The first one minimizes the negative effects due to an inadequate deployment of the radio-frequency emitters and describes a method to determine the minimum number and the best way to locate them, from initial layout and accuracy requirements. The second one increases accuracy thanks to an automatic radio map recalibration technique that takes into account the measurements reported by a few static reference points, strategically deployed inside an environment.