Coding for Visible Light Communication Using Color-Shift Keying Constellations

Color-shift keying (CSK) is a modulation scheme used in visible light communication (VLC) to transmit data by varying the intensity of red, green, and blue LEDs. We study the channel coding for VLC using CSK under constraints of no color shift and no illumination flicker during transmission and design codes over newly introduced symmetric symbol constellations over a triangle intensity plane. One class of codes contains the transmitted sequence based on finite-state machines, and the other is based on the concept of trellis-coded modulation for mitigating color shifts during transmission. The codes have a trellis structure which allows optimal soft-decision decoding using the Viterbi algorithm providing asymptotic coding gain improvements of 1.5 to 3.5 dB with respect to the uncoded transmission while complying with the color shift and flicker constraints.