# Optical-OFDM VLC System: Peak-to-Average Power Ratio Enhancement and Performance Evaluation
## 4 PAPR Reduction Methodology and Proposed Model
### Proposed PAPR Reduction System
Specifically, the PAPR values for LACO\({}_{2}\)-OFDM, LACO\({}_{3}\)-OFDM, and LACO\({}_{4}\)-OFDM were 15.03 dB, 14.595 dB, and 13.96 dB, respectively. After the applied of the precoding methodology, the PAPR reduction values for these systems were observed as 1.81 dB, 1.735 dB, and 1.51 dB, respectively. Furthermore, the \(\rm{E_{b}/N_{o}}\) values for LACO\({}_{2}\)-OFDM, LACO\({}_{3}\)-OFDM, and LACO\({}_{4}\)-OFDM were identified as 15.62 dB, 16.78 dB, and 17.52 dB. However, the \(\rm{E_{b}/N_{o}}\) for these systems degraded by values of 0.45 dB, 0.57 dB, and 0.6 dB, respectively. ACO-OFDM demonstrated a PAPR reduction of 3.27 dB, while FLIP-OFDM exhibited a reduction of 3.26 dB without \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**References**} & \multirow{2}{*}{**MCM Approach**} & **FFT/IFFT** & **Modulation** & **PAPR Reduction** & \(\rm{E_{b}/N_{O}}\) Difference** \\  & & **Size** & **Scheme** & **(dB)** & **(dB)** \\ \hline \multirow{2}{*}{[42]} & \multirow{2}{*}{ESACO OFDM} & \multirow{2}{*}{128} & 16-QAM & \multirow{2}{*}{\(\approx\)1.2} & 1 \\  & & & 64-QAM & & 256-QAM \\ \hline \multirow{2}{*}{[49]} & \multirow{2}{*}{OFDM-based VLC with DCT} & \multirow{2}{*}{128} & \multirow{2}{*}{4-QAM} & 1.4 & 0 \\ \hline \multirow{6}{*}{[51]} & \multirow{2}{*}{WHT-DCO-OFDM} & \multirow{6}{*}{256} & 0.54 & \multirow{6}{*}{N/A} \\  & & DHT-DCO-OFDM & & 0.99 & \\  & & VLM-DCO-OFDM & & 1.87 & \\  & & WHT-ACO-OFDM & & 0.93 & \\  & & DHT-ACO-OFDM & & 1.27 & \\ \hline \multirow{2}{*}{[52]} & \multirow{2}{*}{WHT-precoding OOFDM} & \multirow{2}{*}{256} & \multirow{2}{*}{16-QAM} & 0.5 & \multirow{2}{*}{\(\approx\)0} \\  & & DCT-precoding OOFDM & & & \\ \hline \multirow{6}{*}{[51]} & \multirow{2}{*}{WHT-precoding OOFDM} & \multirow{2}{*}{256} & \multirow{2}{*}{16-QAM} & \multirow{2}{*}{0.5} & \multirow{2}{*}{\(\approx\)0} \\  & & VLM-DCO-OFDM & & 16-QAM & 3.26 & \(\approx\)0 \\  & & VLM-DCO-OFDM-10 dB & & 16-QAM & 1.77 & \(-\)0.06 \\  & & VLM-ADO-OFDM-10 dB & & 16-QAM & 1.22 & \(\approx\)0 \\  & & VLM-DCO-OFDM-13 dB & & 16-QAM & 1.39 & \(\approx\)0 \\  & & VLM-ADO-OFDM-13 dB & & 16-QAM & 1.13 & \(\approx\)0 \\  & & VLM-ASCO-OFDM & & 16-QAM & 1.62 & \(\approx\)0 \\  & & VLM-ACO\({}_{2}\)-OFDM & & 16-QAM & 1.81 & 0.45 \\ Proposed & \multirow{2}{*}{VLM-LACO\({}_{3}\)-OFDM} & \multirow{2}{*}{1024} & \multirow{2}{*}{16-QAM} & 1.735 & 0.57 \\ Techniques & & VLM-LACO\({}_{4}\)-OFDM & & 16-QAM & 1.51 & 0.6 \\  & & VLM-DCO-OFDM-10 dB & & 64-QAM & 1.403 & \(-\)0.31 \\  & & VLM-ADO-OFDM-10 dB & & 64-QAM & 1.054 & \(\approx\)0 \\  & & VLM-DCO-OFDM-13 dB & & 64-QAM & 1.06 & \(-\)0.04 \\  & & VLM-ADO-OFDM-13 dB & & 64-QAM & 1.05 & \(\approx\)0 \\  & & VLM-ASCO-OFDM & & 256-QAM & 1.67 & \(\approx\)0 \\  & & VLM-LACO2-OFDM & & 256-QAM & 1.79 & 0.56 \\  & & VLM-ACO-OFDM & & 4096-QAM & 2.29 & \(\approx\)0 \\  & & VLM-FLIP-OFDM & & 4096-QAM & 2.768 & \(-\)0.107 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: _Cont._any degradation in BER performance. DCO-OFDM demonstrated superior BER and PAPR performance compared to ADO-OFDM when operating under the same modulation scheme and DC bias level. This advantage is attributed to the information hierarchy inherent in DCO-OFDM. The research involves comparing related literature to validate and establish the novelty of the proposed schemes and assessing their performance within the field. Ultimately, this study advances the compatibility of various O-OFDM systems for practical applications. [PERSON] came up with the idea, drafted the paper, and ran the simulations; [PERSON] and [PERSON] reviewed the article and carried out the theoretical analysis; [PERSON] analyzed the numerical findings; [PERSON], [PERSON], [PERSON] and [PERSON] enhanced the updated version of the manuscript and contributed to the simulation result and the validation; [PERSON], [PERSON] and M.A. supervision; [PERSON], [PERSON] and [PERSON], writing--review and editing; funding, M.A. All authors have read and agreed to the published version of the manuscript.