## 3 Results and Discussion
### Channel Impulse Response  
The channel impulse response is arguably the most important result when modeling a VLC channel, since it allows us to model how light signals are affected by the channel. Unfortunately, it is nearly impossible to visualize the CIR of all positions in the simulation scenario all at once. This is why Figure 8 only presents the CIR for four RX positions: \(\mathbf{R}_{1}=(4,1,1.8)\) m, \(\mathbf{R}_{2}=(2,1,1.8)\) m, \(\mathbf{R}_{3}=(0,3,1.8)\) m, and \(\mathbf{R}_{4}=(6,0,1.8)\) m. In each graph, the CIR for \(h[1,1](t)\) (red channel), \(h[2,2](t)\) (green channel), and \(h[3,3](t)\) (blue channel) are compared to the CIR of the reference monochromatic channel defined in Equation (64), i.e., \(R_{\text{ref}}\cdot h_{\text{ref}}(t)\), where \(R_{\text{ref}}=0.53\) A/W is the PD responsivity for the reference channel, the optical filter gain is \(\mathcal{G}_{\text{ref}}=1\), and the wall reflectance is \(\rho_{\text{ref}}=0.6\). Note that \(\mathbf{R}_{1}\) and \(\mathbf{R}_{2}\) are RX positions that are symmetrical concerning the LED, differing only in that for the RX at \(\mathbf{R}_{2}\), the LOS link is severely shadowed, while for the RX at \(\mathbf{R}_{1}\), there is no shadowing. Thus, comparing Figure 8 with Figure 8b allows us to clearly see the difference between an LOS-dominant and an NLOS-dominant UM-VLC channel. It is clear how, in the LOS-dominant case, i.e., Figure 8a, the reference and proposed models are similar because the RX position is close to the TX, and thus there is almost no attenuation. In the NLOS-dominant case, i.e., Figure 8b, the proposed channel is much more attenuated than the reference channel. This is as expected, since in the NLOS-dominant case, even if TX and RX are close, the light still has to travel a much longer path (to the wall and back) and thus experiences more attenuation due to dust than in the LOS-dominant case, for the same TX-RX positions. Since the dust attenuation is not factored into the reference channel, it has a much higher gain than the proposed channel in the NLOS-dominant case. The much higher delay spread present in the NLOS-dominant case is also very clear when comparing Figure 8a to Figure 8b.  
\(\mathbf{R}_{3}\) is located on one corner of the simulation scenario, at the wall farther away from the LED (\(y=3\) m), whereas \(\mathbf{R}_{4}\) is located on another corner of the simulation scenario, at the wall closer to the LED (\(y=0\) m). By comparing Figure 8c to Figure 8d, we see that, for the proposed channel model, the CIR of the RX located further away from the LED is slightly more attenuated than the CIR of the RX located closer to the LED. On the contrary, in the reference channel, the CIR of the RX positioned further away has a higher gain. This means that without attenuation, the corner in \(\mathbf{R}_{3}\) has a higher gain than the corner in \(\mathbf{R}_{4}\) since it is relatively better positioned to receive the radiation pattern of the LED (the LED is tilted \(20^{\circ}\) towards its opposite wall). This changes when considering dust attenuation, since the corner at \(\mathbf{R}_{3}\) is position further away than \(\mathbf{R}_{4}\) and thus, dust attenuation outpaces any geometrical advantage corner \(\mathbf{R}_{3}\) had over corner \(\mathbf{R}_{4}\). In Figure 5d, we can see this even more clearly, where the power ratio is much higher in the corners at the wall farther away from the LED than in the corners at the wall closer to the LED.