Channel model and modulation schemes for visible light communications

We present indoor multipath dispersion characteristics for visible light communications (VLC). We generalize the conventional ray-tracing model by including wavelength-dependent white LED characteristics and spectral reflectance of indoor reflectors. We perform a computer simulation to compare the power delay profile of the VLC with that of infrared communications. The VLC uses solid-state lightings to transmit information; therefore it is necessary that modulation schemes for the VLC provide dimming control. We consider several modulation schemes to offer both functions of modulating data-stream and controlling the brightness at the same time. We analyze communication performance in terms of power requirement and spectral efficiency.