AUTHORS: Haitham Freag, Emad S. Hassan, Sami A. El-Dolil, Moawad I. Dessouky

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ABSTRACT: Orthogonal frequency division multiplexing (OFDM) is used with visible light communication (VLC) systems to reduce the effects of inter-symbol interference (ISI) and to achieve communication with high speed of data transmission and huge bandwidth. However, OFDM based VLC systems suffer from high peakto-average power ratios (PAPRs). This paper proposes a new hybrid PAPR reduction technique based on signal transformation combined with clipping. The Hadamard transform is used in the proposed technique due to its advantages in reducing the PAPR without affecting the bit error rate (BER) of VLC systems. The optimum clipping threshold at which we can simultaneously reduce the PAPR and improve the BER of VLC systems is also determined. In this paper we also propose a new OFDM structure based on using Discrete Cosine Transform (DCT) precoded before inverse fast Fourier transform (IFFT) stage to further improve the PAPR reduction capability and BER performance. The performance of the proposed technique in terms of complementary cumulative distribution function (CCDF) and the BER is simulated. The obtained results show that the proposed technique can simultaneously reduce the PAPR and achieve good BER performance when compared to the original OFDM based VLC system.

KEYWORDS: OFDM, VLC systems, PAPR reduction, Hadamard transform, DCT precoding, clipping method.

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