## 3 VLC System Model  
Traditionally, VLC systems have relied on LEDs as the primary light source due to their energy efficiency, low cost, and widespread availability. However, recent advancements have demonstrated the potential of laser-based light sources to overcome key limitations of LED-based systems, particularly in achieving higher data rates and extended transmission distances [34; 35]. Laser-based VLC systems offer several advantages over their LED counterparts. The collimated beam profile of lasers significantly reduces beam divergence, enabling long-range communication with minimal attenuation. Additionally, lasers exhibit higher modulation bandwidths compared to LEDs, making them suitable for high-speed data trans \begin{table}
\begin{tabular}{c l l l l l} \hline \hline
**Ref. No.** & **Objective** & **Technologies Used** & \begin{tabular}{l} **Performance** \\ **Metrics** \\ \end{tabular} & \
\begin{tabular}{l} **Description** \\ **\end{tabular} &
\begin{tabular}{l} **Main Limitations** \\ \end{tabular} \\ \hline
**[30]** & VLC-based & \begin{tabular}{l} WDM, DS-OCDMA, \\ aeronautical network \\ for in-flight \\ entertainment \\ distribution. \\ \end{tabular} & \begin{tabular}{l} BER \\ 2D-OCDMA, PSO \\ \end{tabular} & \
\begin{tabular}{l} Proposed an aeronautical \\ VLC network architecture \\ for in-flight entertainment \\ distribution using \\ advanced wavelength \\ assignment techniques. \\ \end{tabular} &
\begin{tabular}{l} Does not provide in-depth \\ exploration of modulation \\ schemes or MIMO \\ techniques and focuses \\ primarily on optical \\ interference mitigation. \\ \end{tabular} \\ \hline
**This work** & Evaluation of \begin{tabular}{l} MIMO-VLC systems \\ under ambient light \\ interference and \\ varying transmission \\ distances using \\ different modulations. \\ \end{tabular} & \begin{tabular}{l} MIMO-VLC, NRZ, \\ RZ, QPSK \\ modulation \\ \end{tabular} & \begin{tabular}{l} BER, transmission \\ distance, system \\ resilience \\ \end{tabular} & \
\begin{tabular}{l} Evaluates MIMO-VLC \\ systems using various \\ modulation techniques, \\ focusing on performance \\ under ambient light \\ interference and varying \\ transmission distances. \\ \end{tabular} &
\begin{tabular}{l} Addresses gaps in prior \\ studies by analyzing the \\ combined impact of MIMO, \\ modulation schemes, and \\ ambient light interference. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont_. mission. Recent studies have validated these advantages in practical implementations. For instance, [PERSON] et al. achieved indoor data rates of up to 100 Gbps and outdoor point-to-point transmission speeds of 4.8 Gbps using laser-based light sources, highlighting the feasibility of laser technology for both indoor and outdoor VLC applications [34]. Furthermore, [PERSON] et al. presented a mobile VLC system utilizing lasers, demonstrating the ability of such systems to support dynamic communication scenarios while maintaining high-performance metrics. This study emphasizes the versatility of lasers in addressing the challenges of real-world VLC environments, including mobility and ambient light interference [35]. By leveraging these advancements, the proposed system employs laser-based light sources to achieve superior performance in terms of transmission distance, data rate, and noise resilience [36]. Figure 1 shows the block diagram of a 2 \(\times\) 2 MIMO-based VLC system. According to this diagram, the data source generates binary data, which is passed through the line coding that uses NRZ or RZ techniques to convert binary data into electric pulses. Next, a certain type of modulation technique is used to modulate an electric pulse signal over a continuous wave light signal and produce a modulated light signal. Then the modulated signal is transmitted via LASER; the transmitted signal must be positive and real valued since LASER cannot send imaginary data [34; 35; 36; 37].