## 2 Scenario and Ray-Tracing Simulation Setup
### Ray-Tracing Simulation Setup for VLC Bands  
We utilized the non-sequential ray-tracing software Zemax(r) (Zemax LLC, Kirkland, WA, USA) to obtain the VLC channel data [30]. VLC channel models developed using this non-sequential ray-tracing method were accepted as reference channel models in IEEE 802.15.13 and IEEE 802.11 bb [22]. This channel modeling approach has been validated through experimental results in [31].  
The first step was to construct a three-dimensional simulation environment to recreate the industrial scenario. Firstly, the floor, ceiling, and walls were constructed according to the scenario size. Then, CAD models that matched the actual length, width, and height of the metal instruments were chosen and imported into the software according to their position in the realistic industrial scenario.  
Moreover, the reflection characteristics of each object were set according to those of its actual material. The reflection coefficient refers to the ratio of the intensity of the reflected light to the intensity of the incident light on the reflective material surface. It is influenced by the wavelength of the light signal. Due to the large wavelength coverage of visible light signals, the wavelength dependence of the reflection coefficients for various materials needed to be taken into consideration, which is shown in Figure 2. Commonly used materials for indoor scenarios, such as those of the ceiling, floor, and plaster wall, were obtained from [30]. The remaining materials, such as plate window glass, pinewood, galvanized steel, and Fe, were obtained from [32]. Furthermore, the radiation pattern was set based on the roughness of the object. For non-metallic reflectors, which are relatively rough, the pure Lambertian radiation model was adopted. For metal instruments, specular reflection and Lambertian radiation simultaneously occurred, with each accounting for a proportion of half of the received power.  
The second step was to set up the Tx and Rx in the simulation environment. We placed the Tx and Rx on the same LOS path as that in the electronic wave band simulation. On the Tx side, we utilized the method of splicing multiple LEDs to ensure that the light source and the isotropic antenna in the electronic wave band had the same transmission pattern. Nine commercially available light sources (PAR20) that had a viewing angle of 40\({}^{\circ}\) were used to achieve 360\({}^{\circ}\) coverage, with different lights pointing from 0\({}^{\circ}\) to 360\({}^{\circ}\) (interval of 40\({}^{\circ}\)) at TX. Furthermore, the relative spectral power distribution of the light source followed that of typical white light distribution, as shown in Figure 3. On the Rx side, we used rectangular detectors that were facing in the direction of the Tx. All the key parameters can be found in Table 2.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Electronic Wave Band** & **Visible Light Band** \\ \hline Scenario size & 33.3 m \(\times\) 7.7 m \(\times\) 3 m \\ \hline Average height of metal instruments & 1.27 m \\ \hline Central frequency & 3.5/6/28/60/220/260/300 GHz & White light (380–780 THz) \\ \hline TX height & 1.60 m \\ \hline TX pattern & Isotropic & Isotropic-like \\ \hline Analysis rays & 10\({}^{7}\) & \\ \hline Minimum relative ray intensity & 10\({}^{-3}\) & \\ \hline Transmitter power & 1 W & \\ \hline Radiation pattern & Specular reflection & Specular reflection 50\% \\  & & Lambert radiation 50\% \\ \hline RX height & 1.27 m & \\ \hline RX pattern & Isotropic & Rectangular (10 cm) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of simulation setup.  
Figure 2: The reflection coefficients for various materials.