PAPR REDUCTION IN ACO-OFDM FOR VISIBLE LIGHT COMMUNICATION SYSTEM

Abstract

Visible Light Communication (VLC) is gaining popularity in optical wireless. In conventional OFDM, bi-polar signals having both positive and negative values are considered. However, in optical OFDM uni-polar signals, which have only positive values, are used. Therefore, suitable changes have to be done in conventional OFDM to make it compatible with O-OFDM. These modifications lead to the generation of asymmetrically clipped optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) technology. In ACO-OFDM systems Peak to Average Power Ratio (PAPR) is a detrimental effect and should be suppressed. In ACO-OFDM, the estimation of probability density function (pdf) is not straightforward; therefore, a very limited literature is available. In this paper, an attempt is made to estimate pdf and Complimentary Cumulative Distribution Function (CCDF) expression for an ACO-OFDM with intensity modulation and direct detection (IM/DD), and its validity is checked by using simulation results. For ACO-OFDM scheme PAPR reduction methodology is used by applying various clipping strategies along with non-linear µ-law companding scheme. The results presented in the paper are obtained through computer simulation using MATLAB software. As clipping increases Bit Error Rate (BER), therefore, at various clipping mechanism BER are also obtained. It has been found, that by choosing suitable clipping along with non-linear companding scheme, PAPR can be reduced significantly while maintaining reasonable good BER performance. It is found, that with the proposed technique, PAPR is reduced by 76.10% as compared to raw ACO-OFDM.

Keywords

• ACO-OFDM
• BER
• CCDF
• O-OFDM
• PAPR
• pdf