# Optical-OFDM VLC System: Peak-to-Average Power Ratio Enhancement and Performance Evaluation
## 4 PAPR Reduction Methodology and Proposed Model
### Proposed PAPR Reduction System
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**MCM** & **Modulation** & \begin{tabular}{c} **E\({}_{\text{b}}/\text{N}_{\text{0}}\)** \\ **Conventional** \\ **(dB)** \\ \end{tabular} & \begin{tabular}{c} **E\({}_{\text{b}}/\text{N}_{\text{0}}\)** \\ **VLM** \\ **(dB)** \\ \end{tabular} & \begin{tabular}{c} **E\({}_{\text{b}}/\text{N}_{\text{0}}\)** \\ **Difference** \\ **(dB)** \\ \end{tabular} & \begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **Conventional** \\ **(dB)** \\ \end{tabular} & \begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **VLM (dB)** \\ \end{tabular} & \
\begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ ****VLM (dB)** \\ \end{tabular} &
\begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **Reduction** \\ **(dB)** \\ \end{tabular} \\ \hline DCO-7 db & 64-QAM & N/A & N/A & N.A & 9.385 & 7.725 & 1.66 \\ \hline ADO-7 db & 64-QAM & N/A & N/A & N.A & 10.154 & 9.159 & 0.995 \\ \hline DCO-10 db & 64-QAM & 26.86 & 26.55 & \(-\)0.31 & 7.633 & 6.23 & 1.403 \\ \hline ADO-10 db & 64-QAM & 30.2 & 30.26 & 0.06 \(\approx\) 0 & 8.411 & 7.357 & 1.054 \\ \hline DCO-13 db & 64-QAM & 29.45 & 29.41 & \(-\)0.04 & 5.93 & 4.87 & 1.06 \\ \hline ADO-13 db & 64-QAM & 32.84 & 33 & 0.16 \(\approx\) 0 & 7.11 & 6.06 & 1.05 \\ \hline ACO & 4096-QAM & 34.25 & 34.278 & 0.028 \(\approx\) 0 & 15.97 & 13.68 & 2.29 \\ \hline FLIP & 4096-QAM & 34.277 & 34.17 & \(-\)0.107 & 16.658 & 13.89 & 2.768 \\ \hline ASCO & 256-QAM & 26.35 & 26.42 & 0.07 \(\approx\) 0 & 15.63 & 13.96 & 1.67 \\ \hline
**LACO\({}_{2}\)** & 256-QAM & 24.66 & 25.22 & 0.56 & 15.58 & 13.79 & 1.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: PAPR0 and \(\text{E}_{\text{b}}/\text{N}_{\text{0}}\) values at a CCDF of \(10^{-3}\) and a BER of \(10^{-4}\). Additionally, the PAPR reduction value and the disparity in \(\text{E}_{\text{b}}/\text{N}_{\text{0}}\) between conventional O-OFDM approaches and the newly introduced O-OFDM approaches after integrating the VLM technique with different modulation scheme but at the same spectral efficiency of 5.9883 (\(\text{bits}/\text{sec}/\text{Hz}\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**References** & **MCM Approach** & \begin{tabular}{c} **FFT/IFFT** \\ **Size** \\ \end{tabular} & \begin{tabular}{c} **Modulation** \\ **Scheme** \\ \end{tabular} & \
\begin{tabular}{c} **PAPR Reduction** \\ **(dB)** \\ \end{tabular} &
\begin{tabular}{c} **E\({}_{\text{b}}/\text{N}_{\text{0}}\) Difference** \\ **(dB)** \\ \end{tabular} \\ \hline
[3] & Pilot-Assisted Optical OFDM & 1024 & M-QAM & \(\approx\)2.2 dB & N/A \\ \hline
[24] & \(\mu\)-SOOFDM & 64 & 16-QAM & 0.45 & \(\approx\)0 \\  & & & 1.93 & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison between the novel proposed O-OFDM approaches and other approaches. ## 7 Conclusions

This paper introduces various Optical-OFDM techniques aimed at identifying an effective approach for VLC systems. The study introduces an innovative PAPR reduction methodology for various O-OFDM approaches, demonstrating minimal degradation in the BER. The PAPR reduction method was utilized to address the nonlinearity issue in O-OFDM. Notably, these reductions were achieved without any degradation in the system's BER performance. The simulation results for different O-OFDM approaches demonstrate that as the modulation order increased, there was an enhancement in spectral efficiency and a decrease in BER performance. However, the PAPR performance remained relatively constant or approximately the same. Upon integrating the proposed method into various O-OFDM approaches, significant PAPR reduction values were achieved without noticeable degradation in BER. LACO-OFDM demonstrated superior BER performance compared to other O-OFDM approaches when operating under the same modulation scheme or spectral efficiency. LACO\({}_{2}\)-OFDM offered equivalent spectral efficiency and PAPR as ASCO-OFDM, yet with reduced computational complexity.