# 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}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **MCM** \\ **Approach** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **E\({}_{\text{b}}\)/N\({}_{\text{O}}\)** \\ **Conventional** \\ **(dB)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **E\({}_{\text{b}}\)/N\({}_{\text{O}}\)** \\ **VLM (dB)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **E\({}_{\text{b}}\)/N\({}_{\text{O}}\)** \\ **Difference** \\ **(dB)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **VLM (dB)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **VLM (dB)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **PAPR\({}_{\text{0}}\)** \\ **Reduction (dB)** \\ \end{tabular} } \\ \hline \hline DCO-7 dB & 21.65 & N/A & N/A & 9.58 & 7.36 & 2.22 \\ \hline ADO-7 dB & 23.22 & N/A & N/A & 10.59 & 8.86 & 1.73 \\ \hline DCO-10 dB & 22.25 & 22.19 & \(-0.06\approx 0\) & 7.71 & 5.94 & 1.77 \\ \hline ADO-10 dB & 25.9 & 26 & \(0.1\approx 0\) & 8.5 & 7.28 & 1.22 \\ \hline DCO-13 dB & 25.13 & 25.19 & \(0.06\approx 0\) & 6.02 & 4.63 & 1.39 \\ \hline ADO-13 dB & 28.5 & 28.59 & \(0.09\approx 0\) & 7.14 & 6.01 & 1.13 \\ \hline ACO & 15.23 & 15.24 & \(0.01\approx 0\) & 16.44 & 13.17 & 3.27 \\ \hline FLIP & 15.2 & 15.23 & \(0.03\approx 0\) & 16.58 & 13.32 & 3.26 \\ \hline ASCO & 17.37 & 17.47 & \(0.1\approx 0\) & 15.03 & 13.41 & 1.62 \\ \hline
**LACO\({}_{\text{2}}\)** & 15.62 & 16.07 & 0.45 & 15.03 & 13.22 & 1.81 \\ \hline
**LACO\({}_{\text{3}}\)** & 16.78 & 17.35 & 0.57 & 14.595 & 12.86 & 1.735 \\ \hline
**LACO\({}_{\text{4}}\)** & 17.52 & 18.12 & 0.6 & 13.96 & 12.45 & 1.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: PAPR0 and E\({}_{\text{b}}\)/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 E\({}_{\text{b}}\)/N\({}_{\text{0}}\) between conventional O-OFDM approaches and the newly introduced O-OFDM approaches after integrating the VLM technique with a 16-QAM modulation scheme. Figure 19: BER comparison between traditional O-OFDM approaches and proposed VLM-O-OFDM approaches using a 16-QAM modulation scheme for **(a)** BER and **(b)** PAPR. exceeded the reduction values for the other approaches, and the \(\text{E}_{\text{b}}/\text{N}_{\text{0 difference}}\) for these two approaches was nearly zero. At a 13 dB DC bias level, ADO and DCO-OFDM exhibited a PAPR reduction of 1.39 dB and 1.13 dB, respectively. Additionally, the \(\text{E}_{\text{b}}/\text{N}_{\text{0 difference}}\) for these two approaches was nearly zero. When the DC bias level was set at 10 dB, DCO-OFDM showcased a PAPR reduction of 1.39 dB, while the \(\text{E}_{\text{b}}/\text{N}_{\text{0 difference}}\) was \(-0.06\) dB. At the same 10 dB DC bias level, ADO-OFDM revealed a PAPR reduction of 1.22 dB; however, this value changed to 1.73 dB at a 7 dB DC bias level, illustrating a variation in PAPR reduction concerning changes in the DC bias level. The PAPR reduction values were 1.62 dB, 1.81 dB, 1.735 dB, and 1.51 dB for ASCO, \(\text{LACO}_{2}\), \(\text{LACO}_{3}\), and \(\text{LACO}_{4}\)-OFDM, respectively. Table 6 presents the detailed numerical results of this assessment at a BER of \(10^{-4}\) and a CCDF of \(10^{-3}\). This evaluation highlights that the proposed PAPR methodology effectively reduces PAPR without causing any degradation in the BER performance for various MCM approaches. Figure 21a delves into assessing the BER performance of various O-OFDM approaches both pre- and post-implementation of the VLM methodology. These O-OFDM strategies maintained an identical spectral efficiency of 5.9883 (bits/sec/Hz). The LACO-OFDM performed better than other approaches by employing a smaller constellation size than FLIP and ACO-OFDM.