An LC-to-camera communication system with ambient light

Abstract

The current wireless networks can face congestion issues due to the increasing number of digital devices. One way to overcome this is to establish communica-tion at a different range of frequencies, specifically in visible light. Most studies in Visible Light Communication (VLC) systems use active light sources like LEDs for transmission, but due to its high power consumption, studies have explored the domain of passive VLC that employs Liquid Crystal (LC)s. These systems utilize the existing lighting infrastructure, without needing dedicated LED transmitters. LCs modulate ambient light by controlling its polarization, thus encoding information. At the receiving end, a camera consisting of optical sensors captures and decodes these signals. However, single-pixel LC-to-Camera systems struggle to transmit data at high capacity. On the other hand, recent developments reveal that LCs can convert incoming light to polarized color sig- nals under certain conditions. This thesis work exploits these properties to design a method that employs colors as data symbols in order to tackle the throughput issue. Therefore, we propose a multi-symbol, multi-channel LC-to-Camera system. We develop a modulation-demodulation mechanism that helps to establish a robust link. Experiments demonstrate an 8-symbol scheme results in a three-time throughput increase at per-pixel level with distances up to 160 cm at minimal error. We explore the scalability with a 2x2 pixel system that operates at rates four times that of a single pixel.