System Design of LED-to-Rolling-Shutter-Camera Communication using Color Shift Keying

Abstract

Visible Light Communication (VLC) is becoming an important research area where Visible Light Sources such as LED, Halogen Lamps and even the sun can be used for Wireless Communication. LED-to-Camera Communication is a form of VLC, where the camera can notice intermittent stimuli changes above a certain threshold frequency (flicker fusion frequency) which human eyes cannot no- tice. There exist numerous methods to encode data (= Modulation Schemes) for LED-to-Camera Communication, however, with some modulation schemes, VLC cannot support any practical appli- cations because the achievable data rate either is too low or the system is difficult to be implemented on off-the-shelf devices.
In this paper, we will propose a system design for LED-to-Camera Communication with Color Shift Keying (CSK) as a modulation scheme to encode the transmitted data. In Color Shift Keying, the sys- tem makes use of colors to encode bits, the receiver will then decode the received color into the corre- sponding bits. The proposed design provides a sys- tem outline which may obtain a more practical data rate by using CSK as a modulation method and a CMOS image sensor as receiver. A CMOS image sensor consists of a matrix of photodiodes which combined make up the captured image. The rolling shutter effect makes use of this matrix-like struc- ture by scanning each line separately, by using the rolling shutter effect the camera captures lines with different colors which can be decoded into bits.