# Optical-OFDM VLC System: Peak-to-Average Power Ratio Enhancement and Performance Evaluation
## 3 Assessment Criteria Employed to Judge the Effectiveness of MCM Approaches
### Peak-to-Average Power Ratio (PAPR)  
PAPR, in wireless communication O-OFDM systems, is a metric that quantifies the ratio between the signal peak and its average power. High PAPR presents a significant  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**MCM TECHNIQUE** & \begin{tabular}{c} **TX** \\ **Complexity** \\ \end{tabular} & **TX ADD** & **TX MULT** & \
\begin{tabular}{c} **RX** \\ **Complexity** \\ \end{tabular} &
\begin{tabular}{c} **RX** \\ **ADD** \\ \end{tabular} & **RX MULT** \\ \hline DCO-OFDM & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 \\ \hline ACO-OFDM & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 \\ \hline FLIP-OFDM & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 & \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 27,652 & 7172 \\ \hline ASCO-OFDM & 3 \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 82,956 & 21,516 & \(\mathrm{5}\,\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 138,260 & 35,860 \\ \hline ADO-OFDM & 2 \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 55,304 & 14,344 & \(\mathrm{3}\,\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 82,956 & 21,516 \\ \hline LACO,2-OFDM & 2 \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 55,304 & 14,344 & \(\mathrm{3}\,\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 82,956 & 21,516 \\ \hline LACO,3-OFDM & 3 \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 82,956 & 21,516 & \(\mathrm{5}\,\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 138,260 & 35,860 \\ \hline LACO,4-OFDM & 4 \(\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 110,608 & 28,688 & \(\mathrm{7}\,\mathrm{O}(\mathrm{Nlog_{2}}N)\) & 193,564 & 50,204 \\ \hline \hline \end{tabular}
\end{table}
Table 4: The specific numerical values for the addition and multiplication operations concerning the previously mentioned approaches while maintaining a constant FFT/IFFT size of 1024.  
challenge in O-OFDM systems, leading to heightened non-linearity and unwanted deformations. The mathematical relationship for PAPR can be described as follows [48].  
\[PAPR=\frac{max\Big{\{}\left|\left|a_{OFDM,n}\right|_{c}\right|^{2}\Big{\}}}{E\left| \left|a_{OFDM,n}\right|_{c}\right|^{2}}, \tag{33}\]  
In this context, \(E\{.\}\) represents the mathematical expectation, while \(\left|a_{OFDM,n}\right|_{c}\) signifies the resulting output time-domain samples from the IFFT operation after applying the previously discussed clipping process in various O-OFDM approaches [24].  
In this paper, the authors present an innovative approach to address the PAPR challenge in the previously mentioned O-OFDM approaches. Typically, the effectiveness of this PAPR reduction methodology is evaluated by utilizing the complementary cumulative distribution function (CCDF). The CCDF quantifies the probability that the PAPR of an O-OFDM signal exceeds a specified threshold PAPR0, as described below [3]:  
\[CCDF=P(PAPR>PAPR0)=1-\Big{(}1-e^{-PAPR0}\Big{)}^{N}, \tag{34}\]  
If a particular scheme outperforms all others in terms of PAPR methodology, its CCDF curve will be positioned to the left of the others. Therefore, in the simulation results section, we analyze and discuss the juxtaposition between the CCDF curves of the proposed schemes.