Passive Communication with Ambient Light

In this work, we propose a new communication system for illuminated areas, indoors and outdoors. Light sources in our environments --such as light bulbs or even the sun-- are our signal emitters, but we do not modulate data at the light source. We instead propose that the environment itself modulates the {ambient} light signals: if mobile elements `wear' patterns consisting of distinctive reflecting surfaces, single photodiode could decode the disturbed light signals to read passive information. Achieving this vision requires a deep understanding of a new type of communication channel. Many parameters can affect the performance of passive communication based on visible light: the size of reflective surfaces, the surrounding light intensity, the speed of mobile objects, the field-of-view of the receiver, to name a few. In this paper, we present our vision for a passive communication channel with visible light, the design challenges and the evaluation of an outdoor application where our receiver decodes information from a car moving at 18 km/h.