513 Mbit/s visible light communications link based on DMT-modulation of a white LED
We report a visible-light wireless point-to-point communication link operating at 513 Mbit/s gross transmission rate (net 450 Mbit/s). The bit-error ratio of the uncoded data was smaller than 2 · 10-3 for an illumination level of 1000 lx. The link was based on a commercial thin-film high-power phosphorescent white LED, an avalanche photo diode, and off-line signal processing of discrete multitone signals. Quadrature-amplitude modulation, bit- and power-loading, as well as symmetrical clipping were successfully employed in pushing the gross transmission rate beyond 500 Mbit/s. Adaptation of the clipping level increased the data rate only by 2%, while simulations predicted an enhancement of 20%. Obstacles towards higher data rates as well as potential remedies are discussed. We predicted that data rates of over 1 Gbit/s can be achieved with the same setup and under the same experimental conditions if these obstacles are overcome.