Advantage of CAP Signaling for VLC Systems Under Non-Linear LED Characteristics

We consider the use of carrier-less amplitude and phase (CAP) modulation together with frequency-domain equalization (FDE)for high-speed data transmission in indoor visible-light communication systems and investigate the suitability of this transmission scheme under non-linear LED characteristics, which has to be dealt with in practical implementations of these networks. We focus on the non-linear characteristic of the LED within its dynamic-range, while neglecting the effect of upper signal clipping which has been subject of extensive research so far. The LED is modeled by the Hammerstein model, which consists of a linear time-invariant system followed by a memoryless non-linear part. Through Monte-Carlo simulations we show that, for a given spectral efficiency, the CAP-FDE scheme suffers less from LED non-linearity in terms of electrical power, as compared with the classical DC-biased optical orthogonal-frequency-division-multiplexing.