Non-linear companding transform for DCO-OFDM-based VLC systems

• Published in: IET communications 2019-05, Vol.13 (8), p.1110-1114
• Main Authors: Xin, Duqiang, Xu, Qiang, Qiao, Shuang, Zhang, Tian
• Format: Article
• Language: English
• Subjects: DCO‐OFDM‐based VLC systems; DC‐biased optical orthogonal frequency division; emission power conservation criteria; given compress coefficient; light emitting diodes; light‐emitting diodes transmitter; negative amplitudes; nonlinearity; novel nonlinear companding; OFDM modulation; optical communication; original DCO‐OFDM signals; peak‐to‐average power ratio; positive amplitudes; power compensation coefficient; Research Article; suitable DC bias; transmission performance degradation
• ISSN: 1751-8628; 1751-8636; 1751-8636
• DOI: 10.1049/iet-com.2018.5864

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 u1 and power compensation coefficient c. After that, another coefficient u2 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.