## 3 Results and Discussion
### Influence of the Obstacle Full Shadow and Half Shadow on Indoor VLC Systems  
Since a half shadow could only be generated under multiple light sources, we first analyzed the influence of a full shadow and a half shadow generated by a single human body obstacle on the indoor SNR distribution under different light sources, as shown in Figure 5.  
As shown in Figure 5, as the same number of obstacles as the number of light sources increased, the area that did not receive the signal-to-noise ratio in the figure decreased; that is, the full shadow area decreased. In addition, when the human barrier moved within the area enclosed by the light source, no receiving signal-to-noise ratio area could be generated, which indicated that the influence of the total shadow generated by the human barrier on the system signal-to-noise ratio gradually decreased as the light source increased. In addition, there were some areas near the unreceived signal-to-noise ratio area, namely, the half-shadow area. This area increased with an increase in the number of light sources, \begin{table}
\begin{tabular}{c c} \hline \hline
**Simulation Parameter** & **Values** \\ \hline Area of the PD, \(A_{PD}\) & 0.01 m\({}^{2}\) \\ Optical filter gain, \(T(\theta)\) & 1 \\ FOV, \(\psi_{FOV}\) & 70\({}^{\circ}\) \\ LED semi-angle, \(\varphi_{1/2}\) & 70\({}^{\circ}\) \\ Reflectance coefficient, \(\rho\) & 0.8 \\ Detector responsivity, \(R_{PD}\) & 0.54 A/W \\ System bandwidth, \(B_{\text{slc}}\) & 20 MHZ \\ Central luminous intensity, \(I(0)\) & 2700 cd \\ Transmitted power, \(P_{t}\) & 8 W \\ Radius of the cylinder, \(\mathbf{h}\) & 0.3 m \\ Height of the cylinder, \(\mathbf{r}\) & 1.8 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: System simulation parameters. Figure 5: SNR distribution of full shadow and half shadow occlusions of single body obstacles with different light sources. (**a**,**d**) Three-dimensional and two-dimensional graphs of two light sources and one obstacle; (**b**,**e**) Three-dimensional and two-dimensional graphs of three light sources and one obstacle; (**c**,**f**) Three-dimensional and two-dimensional graphs of four light sources and one obstacle. which also verified the above theoretical derivation; that is, the number of half shadows generated by human obstacles was proportional to the number of visible light sources. Although the receiving signal-to-noise ratio of the receiver in the semi-shadowing region did not change as significantly as that of the receiver in the full shadow region, due to the lack of power of at least one light source, the receiving signal-to-noise ratio of the receiver in the non-shadowing region still decreased significantly. This shows that the shadow effect of obstacles on the system performance cannot be ignored under multiple light sources. In practical applications, there is often more than one obstacle for indoor personnel. Therefore, in this paper, the relationship between the mean square error of illumination and the SNR of the receiving plane of an indoor VLC system and the number of obstacles under the occlusion of different amounts of light sources and shadows was discussed, as shown in Figure 6.  
As shown in Figure 6, under the same number of light sources, the presence of any shadow occlusion made the mean square error of illumination and SNR of the receiving plane increase with an increase in the number of obstacles. By contrast, for the same number of obstacles, the presence of any shadow occlusion could make the mean square error of illumination and SNR of the receiving plane decrease with the increase in the number of light sources. The influence of a half shadow on the mean square error of illumination and signal-to-noise ratio of the receiving plane was significantly higher than that of a full shadow, which could affect the distribution of indoor illumination and the uniformity of the signal-to-noise ratio distribution, making it difficult for users in different indoor locations to obtain similar lighting and communication qualities.