Software Defined Visible Light Communications
We have adapted work from Software Defined Radio to be applicable to the development and evaluation of future Visible Light Communications systems. Here we highlight the SDVLC system and testbed deployed as part of LESA.
We have modified a SDR from RF to compatible with both GNU Radio and Simulink using an optical front end comprised of an illumination grade luminaire from Cree Lighting. We have implemented modulation techniques for dynamic adaptation to lighting conditions such that average optical output power is varied to meet illumination requirements.
Given that the lighting industry is moving towards intelligent systems and controllable luminaires, dual-use VLC must be adaptable in order to maintain the desired average optical output power. The IEEE 802.15.7 standard specifies VPPM for dimming control with VLC data transmission; however dimming range for this technique can be limited by the rise and fall time of the optical signal. We have implemented a 3-technique modulation scheme that extends the dimming range while maintaining throughput and theoretical error rate. In addition, we have generated a real-time implementation of the dimming compatible optical OFDM technique as developed within the Smart Lighting ERC.
The figure below shows the setup of the SDVLC system with the illuminated Cree luminaire modulating the dimming compatible optical OFDM technique.