## 8 Conclusions  
V2V VLC is a promising technology for improving traffic safety and efficiency, particularly during high-traffic periods. However, it is challenging to achieve a high SNR over long communication distances. In the literature, most of the papers that address this problem are focused on the receiver side, whereas few studies are focused on the transmitter. Therefore, this paper is focused on optimizing the VLC transmitter to address this problem. The use of different arrangements of LED arrays has been studied for indoor VLC systems to achieve a uniform SNR throughout the room. In this paper, we demonstrate that LED arrays can also be beneficial for outdoor VLC systems by increasing the SNR, and consequently, the communication range. This paper investigated various LED array geometries by first establishing a reference configuration using single-LED transmitters and plotting its irradiance distribution at \(y=1\) m. Different LED array geometries were then proposed with two key design parameters: the half FOV \(\phi_{\frac{1}{2}}^{\prime}\) of each LED and \(d_{0}\). Subsequently, we examined the performance of square array transmitters with varying \(\phi_{\frac{1}{2}}^{\prime}\) and \(d_{0}\) values, noting that decreasing \(\phi_{\frac{1}{2}}^{\prime}\) and increasing \(d_{0}\) enhance the SNR and, hence, extend the communication range. We then adjusted these design parameters for each proposed transmitter geometry, aiming to minimize \(\phi_{\frac{1}{2}}^{\prime}\) and maximize \(d_{0}\) while ensuring that all the proposed transmitters have the same irradiance distributions at \(y=1\) m.  
From a theoretical perspective, system performance improves as the value of \(d_{0}\) increases or the FOV of the LEDs decreases without bound. However, the design imposes the constraint that the illuminated height (\(H\)) and width (\(W\)) must remain constant. Consequently, the values of these parameters are limited. Their values were carefully selected to optimize system performance while maintaining consistent \(H\) and \(W\) dimensions across all designs. Additionally, the separation distance (\(s\)) between the LEDs in the array presents another design constraint. While increasing the array size generally enhances performance, a more compact design is preferable for practical headlight or taillight modules. This creates a trade-off between maximizing system performance and minimizing the overall physical dimensions of the module. With these conditions met, we fixed the design parameters and plotted the SNR against distance for all transmitter configurations. The results consistently showed that the LED arrays outperformed single-LED transmitters, primarily due to the smaller FOV of their elements. For a 15 dB SNR threshold and a separation of \(s=1\) cm, the communication ranges were determined to be 70.5 m for single-LED transmitters, 78.7 m for \(3\times 3\) square array transmitters, 78.6 m for single hexagonal transmitters, 72.7 m for octagonal transmitters, 80.1 m for \(5\times 5\) square array transmitters, and 83.8 m for honeycomb hexagonal array transmitters. Notably, the honeycomb hexagonal transmitters achieved the longest communication distance, yielding a 19% increase compared to the single-LED transmitters. Furthermore, we plotted the BER against the SNR and found that the BER reached \(10^{-6}\) at an SNR of 13.2 dB. In addition, a plot of BER versus distance for all the transmitter configurations was produced and the distances where the BER becomes \(10^{-6}\) were found to be 78.4 m for the single-LED transmitters, 87.4 m for the \(3\times 3\) square array transmitters, 87.3 m for the single hexagonal array transmitters, 80.7 m for the octagonal array transmitters, 89.0 m for the \(5\times 5\) square array transmitters, and 93.0 m for the honeycomb hexagonal array transmitters. In addition, we demonstrated that our proposed transmitter design performs robustly even when the sizes of the LED arrays are decreased drastically.