## 4 Results and Analysis
### Path Loss
This can be attributed to the inconsistent height of the receiver. In 3 GPP TR 38.901, the height of the receiver is described as embedded, which represents that the receiver height is the same as the average height of the reflector in the scenario, while in this research, the receiver was located lower than the average height of the metal instruments, which meant that there were a large number of metal reflectors distributed around the receiver. The abundant metal reflectors could lead to various NLOS signals. Therefore, in the received signal, the ratio of the LOS signal was relatively small, resulting in a smaller PLE. This can also be verified by the K factor. In 3 GPP TR 38.901, the average K factor for the factory scenario is 7 dB, while in this research, the average K factor for the 3.5 GHz channel was \(-\)7.74 dB. The smaller value of the K factor represents a small proportion of LOS power in this research. Therefore, the height of the receiver will also greatly affect the parameters of the path loss model in industrial scenarios, which must be taken into account during path loss modeling. Furthermore, due to the abundant NLOS signals, the PLE for the industrial scenario is lower than that for the common indoor hotspot scenario for all the electronic wave bands. For instance, for 0.5-100 GHz bands, the PLE for the indoor office scenario is 1.73 in 3 GPP TR 38.901. Moreover, for the VLC band, the PLE for the industrial scenario is much higher than that for the common indoor hotspot scenario. For example, in [35], the PLE is 1.70 for the indoor conference scenario, while the PLE for the industrial scenario was 3.84 in this research, which is a similar value to that in [23]. This indicates that the light signals will suffer a faster decay in the industrial scenario. This may be due to the combined effect of the large size of the industrial scenario and the special specular reflection on metal surfaces, which would not happen in an indoor office. On the one hand, the large size makes the reflected light rays take longer paths to the RX. On the other hand, specular reflection reduces the angle of the reflected signal compared to pure Lambertian radiation. Therefore, the difficulty for the reflected signals in reaching the receivers is greatly increased. As the transceiver distance increases, the reflected signals that can reach the receiver decrease significantly, resulting in a significant attenuation of the received power with respect to the transceiver distance. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Frequency/GHz** & \(\boldsymbol{\kappa}\) & \(\boldsymbol{\beta}\) & \(\boldsymbol{\sigma}\) \\ \hline \multirow{2}{*}{Sub-6 GHz} & 3.5 & 43.73 & 1.078 & 0.603237 \\ \cline{2-5}  & 6 & 47.63 & 1.054 & 0.696649 \\ \hline \multirow{2}{*}{mmWave} & 28 & 62.82 & 1.174 & 0.980498 \\ \cline{2-5}  & 60 & 68.66 & 1.343 & 1.04594 \\ \hline \multirow{2}{*}{THz} & 220 & 80.13 & 1.321 & 1.11161 \\ \cline{2-5}  & 260 & 81.79 & 1.304 & 1.22165 \\ \cline{2-5}  & 300 & 82.83 & 1.33 & 1.19503 \\ \hline \multirow{2}{*}{VLC} & VLC & 79.25 & 3.84 & 10.1258 \\ \hline
3 GPP & 0.5–100 GHz & - & 2.15 & 4.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: FI model fitting parameters.