Visible Light Communication with Mobile Lights

Artificial lights in our buildings have always been designed to be static for one purpose only; illumination. With the increasing interest in Visible Light Communication (VLC) and a crowded radio-frequency spectrum, static lights in our offices and rooms might not be ideal anymore. VLC can add extra services like high quality communication and localization. These services benefit from optimal circumstances as we can find in the hot spot below the lights. Outside the hot spot, the intensity of the lightbeam starts to drop rapidly. This research is dedicated to the aspect that the static lights are lacking which is mobility. Instead of having static lights we create a light source that is able to move along with persons in a room. In this work, which consists of the design and evaluation of our system, we create a mobile platform which includes enhancement of an existing gondola system, the design of a small mobile LED-transmitter and a smartphone as receiving device. We designed a system for the light to follow a user. The smartphone can locate the light and it calculates the location offset through image processing. New coordinates for the light are send to the gondola system to move the light and keep the transmitter and receiver in sync. The system was tested by installing it in the Embedded Systems laboratory of the TU Delft and evaluated in terms of illumination, communication and energy efficiency compared to a static light network. We can conclude that a mobile light can add extra services to VLC by ensuring a constant high illuminance and signal-to-noise ratio by using individual focused hot spots that follow the user in real-time, with an average position error of 1.74 cm, which the static light network can not do causing a performance degradation. The mobile light is in most cases also more energy efficient than a full hot spot static light network coverage. Besides that, we obtain a 3.91 centimeter precision indoor localization as an extra result.Electrical Engineering | Embedded System