DarkVLP: “Lights-off” Visible Light Positioning

Visible Light Positioning (VLP) has been considered as a promising indoor positioning technology due to its high precision and low cost. However, current visible light positioning techniques are greatly limited by the assumption that lights have to be turned on to emit shining light beams, which is not applicable to scenarios that do not need the illumination all the time. In this paper, we design and implement a novel visible light positioning system, DarkVLP, to achieve high-precision positioning when lights are “turned off”. The “turn off” state means lights emit the extremely-low luminance that is imperceptible to human eyes. In order to realize such a system, we have to tackle non-trivial challenges in data encoding/decoding, modulation/demodulation and positioning algorithm. Specifically, we propose the sliding rheostat based modulation scheme to eliminate the need of complex signal synchronization mechanism and landmark recognition algorithm at the receiver. We also propose the dual-photodiode based positioning algorithm, which effectively mitigates effects of substantial signal strength fluctuation, to reliably achieve visible light positioning. In the end, we design novel circuits and prototype our system DarkVLP on commercial off-the-shelf devices. Results of extensive experiments demonstrate that our DarkVLP system could achieve sub-meter precision under the extremely-low luminance, which greatly broadens application scenarios of visible light positioning.