Adaptive N+1 Color Shift Keying for Optical Camera Communication

Optical Camera Communication (OCC) is an emerging technology for wireless communication between smart devices such as smartphones. A light source such as a LED light and a LED panel is employed as a transmitter in OCC. Among the various modulation schemes, color shift keying (CSK) has attracted considerable attention to improve throughput. CSK exploits the design of three-color LED luminaires. Although CSK is a promising modulation technique, the relationship between symbol colors and external environments has not been considered yet. Some colors become difficult to identify depending on environments including ambient light. To address this problem, this paper proposes an adaptive (N+1)-CSK to define one more color in addition to general CSK. The goal of the proposed scheme is to reduce bit errors by explicitly defining a base color, i.e. NULL color. One symbol is adaptively selected as the base color from the N+1 symbols according to external conditions, and data signals are transmitted using other symbols. We also provide preliminary experimental results to validate the proposed scheme. The bit error rate (BER) is significantly suppressed by appropriately setting the base color depending on the pilot signals of each symbol.