# Simulation of an Indoor Visible Light Communication System Using Optisystem
## 6 Results and Discussion
The signal distortion significantly affects the receiver performance when we increase the irradiance and incident angles from a lower to a higher value. The received signal amplitude decreased when the simulation used higher values. The received signals have smooth curvature for higher values of irradiance and incident angles. However, the signal amplitude is reduced compared to lower angle values. This indicates the angles significantly  
Figure 14: Eye diagram results. (**a**) LOS. (**b**) Single LED NLOS. (**c**) Dual LED NLOS. determine the VLC performance, and it is necessary to optimize the irradiance and incident angles for real-time system implementation. Figure 15: Irradiance angle (\(\theta_{s}\)) effect on an LOS propagation model (\(\theta_{s}\) changes from 0\({}^{\circ}\) to 25\({}^{\circ}\)). Figure 16: Irradiance angle (\(\theta_{s}\)) effect on an LOS propagation model (\(\theta_{s}\) changes from 30\({}^{\circ}\) to 50\({}^{\circ}\)). Figure 17: Incident angle (\(\theta_{d}\)) effect on the LOS propagation model (\(\theta_{d}\) changes from \(0^{\circ}\) to \(25^{\circ}\)). Figure 19 summarises the irradiance and incident angle effect on the receiver signal amplitude. It can be seen that with the angle values from 0\({}^{\circ}\) to 15\({}^{\circ}\), the signal amplitude fluctuates with higher and lower values. When the angle reaches 20\({}^{\circ}\) or higher values, the signal distortion is directly proportional to the angle values. The signal amplitude  
Figure 18: Incident angle (\(\theta_{d}\)) effect on the LOS propagation model (\(\theta_{d}\) changes from 30\({}^{\circ}\) to 50\({}^{\circ}\)). decreases when the system uses higher angles. When the irradiance and incident angles reach 30\({}^{\circ}\), the system shows an equal amount of signal distortion on the receiver side. This indicates that when the angles are in the same value or range of values, the signal amplitude distortion is almost the same in the receiver. Our analysis shows that the VLC system performs well when the angles range from 15\({}^{\circ}\) to 20\({}^{\circ}\). The theoretical analysis of a single LED-based NLOS propagation model is further considered for the FOV effect. Consider an example of the NLOS propagation model of a single LED as a transmitter, shown in Figure 20.  
The incidence and irradiance angles in all the cases are presented in Equations (2)-(6). The initial values used in the analysis are defined as:  
Speed, \(c=3\times 10^{8}\)  
Semi-angle at half power, \(\phi_{1/2}=70^{\circ}\);  
Lambertian order of emission:  
\[m_{l}=\frac{-\ln(2)}{\ln(\cos\phi_{1/2})}=\frac{-\ln(2)}{\ln(\cos 70)}=\frac{-0.69 31}{\ln(0.3420)}=\frac{-0.6931}{-1.07288}=0.6461; \tag{18}\]  
Total transmitted power, \(P_{t}=1\); Detector the physical area of a photodiode, \(A_{r}=1\); Reflection coefficient, \(\rho=0.8\); Gain of an optical filter, \(T_{s}=1\); Refractive index of a lens at a photodiode, \(n=1.5\); FOV of a receiver, FOV = 70; Gain of an optical concentrator:  
Figure 12:0  
Room dimension in meter, \(l_{x},l_{y},l_{z}=10m\); Position of transmitter (LED): \(N_{x}=l_{x}\times 10\); \(N_{y}=l_{y}\times 10\); \(N_{z}=l_{z}\times 10\) Number of the grid on each surface:  
Figure 12:1  
Figure 12:2 Angle effects on the received signal amplitude. **First Reflection:**  
\(d_{1}=5\) m;  
\(d_{2}=10\) m;  
\(\alpha_{ir}=48^{\circ}\)  
\(cos(48)=0.66913\);  
\(\beta_{ir}=40^{\circ}\);  
\(\cos(40)=0.7660\);  
\(\phi_{r}=43^{\circ}\);  
\(\cos(43)=0.7313\);  
\(\psi_{r}=48^{\circ}\);  
\(\cos^{m_{l}}(\phi_{r})=0.8168\);  
Figure 12:3  
Figure 12:4  
Figure 12:5  
**Second Reflection:**  
\(d_{1}=9\) m;  
\(d_{2}=5\) m;  
\(\alpha_{ir}=40^{\circ}\);  
\(\cos(40)=0.7660\);  
\(\beta_{ir}=60^{\circ}\);  
\(\cos(60)=0.5\);  
\(\phi_{r}=50^{\circ}\);  
\(\cos(50)=0.6427\);  
\(\psi_{r}=40^{\circ}\);  
\(\cos^{m_{l}}(\phi_{r})=\left(\cos 50\right)^{0.64601}=0.64278^{0.64601}=0.75163\);  
Figure 12:6  
Figure 12:7 Example of a single LED NLOS propagation model.