Location and wayfinding services through visible light in crowded buildings

To support people’s wayfinding activities in crowded buildings minimizing the risks of contamination this paper proposes a method able to generate landmark route and alert instructions using Visible Light Communication (VLC). The system is composed of several transmitters (ceiling luminaries) which send the map information, alerts and the path messages required to wayfinding. The system informs the users, in real time, not only of the best route to the desired destination, through a route without clusters of users, but also of crowded places. An architecture based on a mesh cellular hybrid structure was used. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. The modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by a SiC optical sensor with light filtering and demultiplexing properties. Each luminaire for downlink transmission is equipped with one two type of controllers: mesh controller and cellular controllers do forward messages to other devices in the vicinity or to the central manager services. The light signals emitted by the LEDs are interpreted directly by the receivers of the positioned users. Bidirectional communication is tested. The effect of the location of the Access Points (APs) is evaluated and a 3D model for the cellular network is analyzed. In order to convert the floorplan to a 3D geometry, a tandem of layers in an orthogonal topology is used, and a 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is implemented, and the 3D best route to navigate through venue is calculated. Buddy wayfinding services are also considered. The results showed that the dynamic VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction along the time, to interact with received information and to optimize the route towards a static or dynamic destination, avoiding the threat of contamination in crowded regions.