# Testbed for Experimental Characterization of Indoor Visible Light Communication Channels
## 4 Simulation Results
The figure also illustrates the elevation (angle from the vertical) and azimuth (angle from the x-axis in the XY plane) for the different locations of the receiver throughout the room. It is clear to see how the receiver is always oriented to a certain point in the center of the ceiling. Some increase in the received power with respect to force vertical orientation of the receiver is observed as well as a greater percentage of the LOS contribution at edge areas. This percentage is also more uniform and with a rectangular shape as reflection on walls becomes less significant due to the fact that the receiver is always pointing to a certain centroid of lamp positions, thus minimizing the observation of walls. Therefore, particular characteristics of each wall, for example, having windows or not, hardly affect the power balance. A simulation for the mockup design illustrated in Figure 2 was conducted so as to compare the obtained results with those of the real indoor VLC environment previously described. In order to observe similar power levels, the power transmitted by each LED lamp was reduced by a factor of approximately \((L_{\text{mockup}}/L_{\text{room}})^{2}\), where \(L_{\text{mockup/room}}\) refers to length of the mockup/room, specifically 0.25 W. Table 2 summarizes the simulation parameters for the mockup scenario. Mockup surfaces are characterized identically as described in Table 1, excepting floor that is considered with null reflection coefficient as there is no floor in the mockup design yielding that all the light reaching this surface vanishes. Figure 9 presents the results obtained for the mockup communication scenario. We can observe similar behavior of the power balance and the illuminance as compared with those results for the room shown in Figure 4. The greater percentage of LOS contribution to the total received power is due to the elimination of the floor as a reflecting surface. Figure 10 illustrates the impulses responses obtained for two positions of the receiver in the mockup: under lamp 1 close to a window (see Figure 2) and at the center of the receiver plane. Although with shorter times due to the smaller dimensions of the mockup, we can observe very similar impulses responses to those obtained for the room scenario as shown in Figure 4. The difference between the two frequencies is due to the fact that the receiver is able to detect the noise in the power balance. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Room size (length \(\times\) width \(\times\) height): & 60 cm \(\times\) 60 cm \(\times\) 30 cm \\ Number of LED arrays (lamps): & 4 (2 \(\times\) 2) \\ Number of LEDs per array: & 9 (3 \(\times\) 3) \\ Dimensions of each LED array: & 0.1 m \(\times\) 0.1 m \\ Positions of LED arrays & array 1: (15, 15, 30) \\ (central point) (\(x\), \(y\), \(z\)) [cm]: & array 2: (45, 15, 30) \\  & array 3: (15, 45, 30) \\  & array 4: (45, 45, 30) \\ LED Lambertian order (\(n\)): & 1 \\ Total LED lamp power (\(P\)): & 250 mW \\ Receiver plane height: & 0 cm \\ Total detector physical area (\(A\)): & 1.00 cm\({}^{2}\) \\ Windows dimensions (width \(\times\) height): & 15 cm \(\times\) 15 cm \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of Simulation for Mockup Scenario. Figure 8: Received power throughout the room when the orientation method defined in Equation (14) is used: (**a**) Power balance. (**b**) Contour map of LOS component percentage in the total received power. (**c**) Elevation of the receiver as a function of its position. (**d**) Azimuth of the receiver as a function of its position. presented in Figure 5, just appreciating the slightly greater percentage of LOS contribution, which is a consequence that there is no floor in the mockup and a lot of light is lost without ever being reflected. Therefore, we can conclude that the designed mockup constitutes a good frame for the experimental evaluation of indoor VLC systems.