Cubic Metric Reduction for DCO-OFDM Visible Light Communication Systems

Visible light communication (VLC) systems with a direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) architecture suffers from the well-known problem of high peak-to-average power ratio (PAPR). A DCOOFDM signal at the input of the light emitting diode (LED) with high PAPR can experience clipping due to its limited dynamic-range. This causes distortion and degradation of the signal quality, forcing a large power back-off, and so leading to an inefficient use of the LEDs. In order to resolve this problem, we propose to apply a power derating reduction technique at the VLC transmitter based on a modification of the active constellation extension (ACE) method with two important changes: a better predictor of the power derating than the PAPR, the cubic metric (CM), and a more effective clipping stage. With the proposed method, we achieve a significant CM reduction as large as 7.1 dB, which contributes to a noticeable gain in the input power back-off of 2.5 dB or an important reduction of signal distortion, and a greater illumination to communication efficiency (ICE), higher than 30%.