## 6 Performance Evaluation
We kept \(\mathrm{d}_{\alpha,\chi}=0\) and \(\mathrm{d}_{\alpha,\mathrm{h}}\) was varied during performing the simulation to keep the LED at the center. In addition, the LED flickering rate was set to 1.5 kHz resulting in 70 pixels to construct one strip. The minimum number of strips corresponds to the maximum communication distance, which also depends on the focal length. Figure 11 illustrates how the maximum communication distance varies with respect to the LED size and the effective focal length. It can be seen that the maximum communication distance can be enhanced using larger LEDs. Compared to an LED size of 1 cm, the communication-distance improvement of 2.5 and 4 times can be noticed for LEDs with 5 cm and 10 cm, respectively. Both simulations in Figures 10 and 11 were performed at a constant noise spectral density of \(10^{-21}\). It is worth stating that effective communication will be achieved if the LED is clearly focused on the camera; otherwise, it will result in a significant increase in the BER. Moreover, there is a minimum SINR below which data bits cannot be decoded. Figure 9: The variation of the SINR by changing the horizontal distance between the camera and the LED. Figure 12 illustrates the outage probability for OCC for different AOVs of the camera. The effective focal length and LED radius were the same for the second simulation. It can be seen that the probability of outage increases as the AOV is reduced. In addition, the outage probability increases as the LOS distance between the LED and the camera increases. Therefore, it can be outlined that the outage probability can be improved by increasing the camera AOV, which can be achieved by enhancing the resolution of the image sensor. The capacity of an OCC system significantly depends on the camera parameters. Increasing the camera sampling rate can improve the OCC capacity to a considerable extent. The cumulative distribution function (CDF) of the theoretical data-rate limit for different camera sampling rates is depicted in Figure 13. The simulation was performed for different Euclidean distances between the LED and the camera that are ranged from 0.5 m to 5 m. The CDF is zero at distances higher than approximately 4.472 m. As shown in Figure 13, the data rate performance is significantly improved with higher frame rates. In case of a sampling rate in the range of a few kfps, the OCC capacity of up to several Mbps can be achieved. Moreover, it can be noted that the variation in OCC capacity is not considerably severe (16-28 kbps at 30 fps) with increasing communication distance. Figure 11: The maximum communication distance vs focal length for different LED sizes. Figure 10: The variation of the projected image size onto the image sensor with changing vertical communication distances. As discussed in Section 5, user satisfaction with OCC depends on the service types and requirements. A user making a voice call requires a lower data rate compared to a user engaged in a video call. However, a user who uses OCC for LBS requires a good SINR rather than a high data rate. Figure 14 illustrates the variations in the user satisfaction factor with respect to SINR, evaluated in terms of different data rates. This evaluation is generalized with a satisfaction factor above 0.5 considered as good and a factor above 0.8 as excellent. Figure 12: The outage probability for OCC for different LOS distance between the LED and the camera. Figure 13: The cumulative distribution function of the OCC capacity.