VibranSee: Enabling Simultaneous Visible Light Communication and Sensing

Driven by the ubiquitous proliferation of low-cost LED luminaires, visible light communication (VLC) has been established as a high-speed communications technology based on the high-frequency modulation of an optical source. In parallel, Visible Light Sensing (VLS) has recently demonstrated how vision-based at-a-distance sensing of mechanical vibrations (e.g., of factory equipment) can be performed using high frequency optical strobing. However, to date, exemplars of VLC and VLS have been explored in isolation, without consideration of their mutual dependencies. In this work, we explore whether and how high-throughput VLC and high-coverage VLS can be simultaneously supported. We first demonstrate the existence of a fundamental VLC-vs.-VLS tradeoff, driven by the duty cycle of the strobing light source: a larger duty cycle results in higher VLC throughput but reduced VLS coverage, and vice versa. To overcome this limitation, we evaluate two approaches: (a) time-multiplexed VLC and VLS on a single strobe, and (b) harmonic multi-strobing, where multiple light sources are strobed synchronously to effectively create low-duty cycle harmonics of the base strobe frequency. Finally, we present VibranSee, an approach that improves harmonic multi-strobing by adaptively tuning both (a) the strobe duty cycle and (b) the number of strobing harmonics used. Using both analytical studies and prototype-based experiments, we show VibranSee's benefits: it simultaneously achieves VLC data goodput that is ideally only 18.6% lower (and 23.9% lower for an actual working prototype) than the maximum communication rate and infers over 96.6% (100% for the prototype) of possible vibration frequencies.