# Channel Characteristics and Link Adaption for Visible Light Communication in an Industrial Scenario
## 2 Simulation Setup  
### Simulation Scenario Set Up  
Since the existing visible channel measurement platform is limited by the LED bandwidth, the complete channel multipath information cannot be accurately obtained. The non-sequential ray tracing features of Zemax have further been used by [PERSON] et al. [10]. VLC channel models developed by this ray tracing method were accepted as reference channel models in IEEE 802.15.13 and IEEE 802.11 bb [20]. Furthermore, this channel model approach has been demonstrated by conducting several experimental results [21]. In this work, this well-established ray-tracing channel modeling approach was constructed to investigate the channel characteristics in IIoT scenarios. Firstly, as shown in Figure 1a, the three-dimension (3D) indoor environments with a size of \(30\times 10\times 8\) m\({}^{3}\) were created as per the requirements in [7]. Then, computer-aided design (CAD) models, such as the floor, wall, manufacturing equipment, assembly lines, forklifts, etc., were imported to model the realistic IIoT scenarios (e.g., object groups A, B, and C shown in the Figure 1b.). The average height of objects set in the scenario is 2 m. Then, the coating materials of walls, manufacturing equipment, assembly lines, and forklifts were, respectively, assumed to be plaster, Copper (Cu), Aluminium (Al), and Ferrum (Fe). The wavelength-dependent spectral reflection characteristics of the surface materials were also integrated into the simulation platform, which can be downloaded from [22]. Moreover, the mixed reflections including diffuse and specular reflections were set by adjusting the scatter fraction (SF) parameter. The specifications of the reference scenario and coating materials of objects under consideration are summarized in Table 1. Twenty-one lumininaries (\(S_{1}\),..., \(S_{21}\)), which are commercially available LEDs with a 60\({}^{\circ}\) half viewing angle are placed across the ceiling with equal spacing. We set the optical power at 10 Watts for each luminaire to achieve the average illumination level which satisfies typical illumination levels for an IIoT environment. Moreover, to investigate the omnidirectional channel parameter information of the IIoT scenario, we prefer a spherical photodetector (PD) in this study to collect all the MPCs arriving at the PD as the mmWave antenna does. The field of view (FOV) and the detector size are 360\({}^{\circ}\) and 1 cm\({}^{2}\), respectively. Furthermore, this paper mainly focuses on investigating the distance dependence and the effect of objects on VLC channel characteristics. Therefore, as the layout of the IIoT scenario depicted in Figure 1c, a 3D simulation was constructed in the previous subsection with two specific roads (road1 and road2) that were designed to incorporate different configurations. Eighteen different locations are considered for PDs (\(D_{1}\),..., \(D_{18}\)) in Road 1. We first modeled the user with a height of 1.5 m (lower than the average height of objects) and 2.5 m (higher than the average height of objects) to study the effect of different user heights on channel characteristics. Furthermore, to investigate the effects of surrounding objects' densities, we varied the distribution densities of objects surrounding the roads. The same number of points was also considered in Road 2 with a red color (\(E_{1}\),..., \(E_{18}\)). Based on this simulation setting, the influence of various factors on the channel characteristics can be investigated. In our simulation, the Monte Carlo analysis and sob  
Figure 1: (**a**) The 3D IIoT simulation scenario; (**b**) The layout of the IIoT scenario. sampling are adopted as the random ray tracing methods. In addition, the main simulated parameters in the adopted methods are the number of reflections and the number of rays. These parameters can be adjusted through \"Relative Minimum Intensity\" [23], where the normalized intensity dropped to \(10^{-3}\).