StrLight: An Imperceptible Visible Light Communication System with String Lights

This paper presents StrLight, the first practical VLC system that leverages widely-deployed string lights to transmit data. The data transmission is imperceptible to human eyes. Users can decode the data by mobile devices (e.g., smartphones) equipped with cameras. StrLight primarily differs from existing VLC systems in using string lights which are composed of a large number of small LEDs and thus the unique design to address practical issues including a special data modulation/encoding scheme, a data representation with unstructured/unknown topologies of LEDs in the string light, and a fault tolerance against broken and blocked LEDs. To the best of our knowledge, StrLight is the first practical VLC system of its kind. We build several prototypes of string light transmitters and test with different smartphone models and a customized mobile device as receivers. The experiment results show that StrLight provides an efficient and robust data broadcasting. A string light of 100 LEDs working in $450 \;\mathrm{Hz}$450 Hz and a camera with a capture rate of $30 \;\mathrm{Hz}$30 Hz and an image resolution of as low as $320 \times 240$320×240 pixels, delivers data rate of $\sim\!1\;\mathrm{kbps}$∼1 kbps , without observable light flickers.