Dimmable VLC demonstration systems based on LED

Abstract

Recently, there have been many attempts to converge LED with IT technology. Among them, Visible Light Communication (VLC), which is the convergence of illumination and communication, has emerged. In VLC system, both lighting and communication can be simultaneously implemented. By considering both terms together, VPPM(Variable Pulse Position Modulation) modulation scheme is proposed by the IEEE 802.15.7 standard group. It uses binary PPM (Pulse Position Modulation) for communication and PWM (Pulse Width Modulation) for dimming control. In this paper, we introduce the implementation of VLC demonstration system based on VPPM modulation scheme. By changing the pulse width of VPPM signal, we can support 25%, 50% and 75% dimming. In addition, our VLC demonstration system provides a new power system using solar cell. By receiving the VPPM modulated visible light signal in the receiver end, we turn on the receiver power and start the system operation to decode the transmitted signal. By using ATmega128 8bit Micro Controller Unit (MCU) by ATMEL and Q3 XLamp XP-E LEDs of Cree, our system provides about 2kbps data rate with 2.5kHz optical rate in more than 30cm distance. By implementing DM S/W, we show the bit error rate (BER) and achievable data rate (ADR) of our demonstration system.