Abstract
In this study, a novel non-linear companding transform (NCT) is proposed for the DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) based visible light communications (VLC). The authors lower the peak-to-average power ratio (PAPR) of the original DCO-OFDM signals to mitigate the transmission performance degradation induced by the non-linearity of the light-emitting diodes (LEDs) transmitter. Firstly, the positive and negative amplitudes of the original DCO-OFDM signals are separated into two groups. Then, the group with the maximum peak is first processed with a given compress coefficient u 1 and power compensation coefficient c. After that, another coefficient u 2 is calculated by the emission power conservation criteria to further compress the rest group. Finally, these two groups of amplitude samples are combined together before adding a suitable DC bias for driving LEDs. As the mean power is not changed, a PAPR reduction can be obviously realised by the proposed NCT scheme.
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