A Novel ?-law Nonlinear Companding with Modified Recoverable Upper Clipping Method for PAPR Reduction in ACO-OFDM VLC Systems

Abstract

The high Peak-to-Average-Power Ratio (PAPR) is the major challenge that causes signal distortion at the output of a Light-Emitting-Diode (LED) due to the narrow dynamic region of a LED in an Optical Orthogonal Frequency Division Multiplexing (O-OFDM) based Visible Light Communication (VLC) systems. Although a mu-law Nonlinear Companding Transform (mu-NCT) in an Asymmetrically-Clipped O-OFDM (ACO-OFDM) architecture decreases the PAPR degree, generates undesired large signals that can enter the nonlinearity range of a LED. This paper proposes a novel PAPR reduction method referred to as mu-NCT with Modified Recoverable Upper-Clipping (mu-NCT+MoRoC) model. The mu-NCT+MoRoC model benefits from the PAPR reduction of mu-NCT, and later uses all the advantages of the newly designed MoRoC method to reduce the large signals' amplitudes that rose after the mu-NCT. The MoRoC method stores the large signals without losing information at the transmitter within the existing bandwidth using the asymmetrical structure of ACO-OFDM. To recover the source signal at the receiver, the MoRoC method uses newly generated symbol-based threshold detection and recovery algorithms. Both MoRoC and proposed mu-NCT+MoRoC models provide PAPR reduction and 45% peak amplitude reduction for ACO-OFDM systems without additional bandwidth, loss of information, and extra IFFT/FFT.