# Three-Dimensional Division of Visible Light Communication Irradiation Area
## 4 VLC Experiment Setup and Discussion
### Experimental Results  
The experimental results are divided into three areas (I-III) based on the BER (see Figures 6-10). In area I, the longitudinal distance varied from 5 to 150 cm, and changed in the BER were symmetrically distributed on both sides of the origin when the receiver moved laterally from \(-\)20 to \(+\)20 cm. When the longitudinal distance was 5 cm, the  
Figure 5: Experimental setup.  
maximum lateral receiving distance in the negative direction of the receiver was \(-10\) cm and that in the positive direction of the receiver was 9 cm (see Figure 7a), and therefore the lateral receiving distance of the receiver was 19 cm. When the longitudinal distance was 10 cm, the lateral receiving distance of area I reached its maximum when compared with other lampshade heights, and the distance was 25 cm. The lateral receiving distance became smaller with increasing longitudinal distance and reached its smallest value of 12 cm when the longitudinal distance was 150 cm. At the same time, there was an interval with a BER of 100% in the positive and negative directions of the origin. The primary reason for this is that the light reflected by the lampshade was superimposed, producing an inter-symbol interference at the receiver.  
Figure 8: Lampshade height: 4 cm.  
Figure 6: Lampshade height: 2 cm.  
Figure 7: Lampshade height: 3 cm.  
In area II, due to the differences in the heights of the lampshades, the variation range of the BER in the longitudinal direction also varied. When the lampshade height was 2 cm, the variation range of the longitudinal distance was at its minimum, from 200 to 400 cm (see Figure 6b). As the lampshade height increased, as shown in Figure 8b, the variation range of the longitudinal distance also reached its maximum, from 200 to 600 cm. After this, the variation range of the longitudinal distance remained unchanged. At the same time, the lateral receiving distance at the receiver increased with increasing longitudinal distance. When the longitudinal distance increased from 200 to 600 cm, the lateral receiving distance increased from 14 to 24 cm and from 17 to 31 cm, respectively (see Figures 8b and 10b). In this area, the reflected light had little effect on communication performance, and the receiving range of the receiver increased with increasing lampshade height and longitudinal distance.  
In area III, when the longitudinal distance increased, the light intensity attenuated rapidly and the lateral receiving range of the receiver decreased irregularly. When the longitudinal distance increased from 600 to 1000 cm, the receiving distance of the receiver decreased from 22 cm to 0 (see Figure 7c). At the same time, the longest receiving distance in the longitudinal direction was 923 cm. In this area, when the lampshade height increased from 2 to 6 cm, the longest communication distance of the receiver was increased from 725 to 1060 cm. The lampshade height was increased by 4 cm and the communication distance was increased by 46.34%. This provides evidence that the increase in the communication distance directly affects the system communication performance, and that an increase in lampshade height improves the system communication distance.