On the brightness control of ACO-OFDM based VLC systems

In this work, we analyze the brightness performance of asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) based visible light communication (VLC) systems. We specifically consider analog dimming where the brightness is controlled by the average forward voltage/current of the LEDs. In ACO-OFDM, the forward current of the LEDs can be jointly controlled by the DC-bias and useful signal power which have direct impact on the signal-to-noise-distortion-ratio (SNDR). In this work, we maximize the SNDR for a targeted brightness level by jointly optimizing the DC-bias and useful signal power levels. We further propose clipping the positive part of the half-wave symmetry information waveform instead of the negative part (for ACO-OFDM signal generation) in order to achieve higher SNDR values at high brightness requirements.