Analysis and Design of Three-Stage Concatenated Color-Shift Keying

Visible light communication (VLC) relies on abundant unlicensed bandwidth resources. As an attractive high-data-rate modulation scheme designed for VLC, color shift keying (CSK)-assisted modulation is analyzed. We commence our study from an uncoded M-CSK scheme relying on the joint maximum-likelihood (ML) hard detection (HD) of three colors when communicating over an AWGN channel, where both empirical and analytical results are provided. We invoke extrinsic information transfer (EXIT) charts for designing a Maximum a posteriori probability (MAP)-based soft detection (SD)-aided iterative receiver jointly detecting the three colors. Based on the EXIT characteristics of M-CSK, we design different signal labeling strategies for diverse color constellations and detection schemes, which are capable of achieving a substantially improved bit-error-rate (BER) performance. Thus, given fixed transmission power, a CSK system using our proposed signal labeling is capable of increasing the reliable data transmission distance by about 30%.