Designing an optical link between a micro-display and a smartphone camera

Abstract

The popularity of various wireless communication applications is crowding the radio spectrum. As an alternative medium, the visible light spectrum is be- ing exploited. Camera-based visible light communication systems are gaining much attention due to the widespread use of smartphones equipped with small embedded cameras. Screens (e.g., liquid-crystal displays) are ideal choices as multi-pixel transmitters that can send high-capacity packets continuously. Al- though there are many works on screen-to-camera links, only very few are ex- ploiting micro-screens as transmitters. State-of-arts are mainly optimizing the performance of the optical link, less attention is paid to the system’s com- pleteness and practical applications. Thus, the goal of this work is to deliver a self-contained visible light communication system that can send information over a micro-screen-to-camera link at a high data rate.
To achieve our goal, an Android application with real-time image reading and processing is developed. Furthermore, a multi-transmitter system is designed to increase the bandwidth of the communication channel and the system is tweaked to transmit information at a high frame rate. The evaluation results show that this work improves the data rate by over 7-fold, from a baseline of 1.5 kbps to 11.4 kbps. Additionally, a standalone prototype is built based on a Raspberry Pi Zero W. Finally, to showcase the potential of the platform, a smart-city application is developed, where users can download information from Google Maps with the newly developed optical link.
Although the result of this project is encouraging, there is much room for improvement. We envision this work will motivate more research near-field, especially on micro-screen-to-camera links.