Efficient Indoor Localization and Navigation with a Combination of Ultrasonic and CSS-based IEEE 802.15.4a

It has been known that CSS-based IEEE 802.15.4a RF module can provide a relatively desirable level of ranging accuracy. It actually exploits a ranging technique called SDSTWR (Symmetric Double-Sided Two-Way Ranging). Meanwhile, many research efforts have been made to devise efficient rangebased indoor localization techniques. Of these, trilateration has been one of the most widely used localization techniques. Our experiments in indoor environments reveal that the trilateration does not work efficiently against indoor obstacles, for example, steel doors. This paper proposes an efficient indoor localization technique whose localization accuracy (errors) is lesser sensitive to the indoor obstacles. The proposed scheme exploits both ultrasonic devices to guide a user to the center of the hallway and two IEEE 802.15.4a reference nodes to determine the user position. Through extensive experiments on actual indoor environments show that the proposed scheme provides about two times higher accuracy as compared with the trilateration, and the indoor navigation service using the proposed scheme works properly. Keywords; indoor localization, IEEE 802.15.4a, ultrasonic