## 5 Results and Discussions
### User Data Rate (UDR)  
Among the goals of our work (see Section 1) is the application of ADR solutions in \(R_{x}\) to reduce ICI in underground mining environments. Therefore, it is necessary to use metrics to verify compliance with this objective. One of the characteristic parameters of performance measurements of communication systems, especially those of wireless communication, is the UDR, which allows  
Figure 8: RMS delay spread distribution in the underground mining VLC scenarios. for the (**a**) mining roadway and (**b**) mine working face. us to analyze the maximum data transmission rate that can be achieved in the VLC scenarios. Thus, the mathematical expression that describes this metric is Shannon's channel capacity as follows [43],  
\[R_{b}=log_{2}(1+\gamma). \tag{45}\]  
Therefore, the ADR intends to maximize the \(\gamma\) of the mining VLC link, which is directly reflected in the decrease of the ICI, thus maximizing the channel capacity and improving the UDR. In this context, the \(\gamma\) of the pyramidal and hemi-dodecahedron ADRs, presented in Sections 3.2 and 3.3, with each of the signal combining schemes, are analyzed and compared with this metric. The key parameters of the VLC system, the simulation scenarios developed for the two underground mining environments, and the parameters used in the ADRs are listed in Table 1.  
To ensure that ADRs can effectively receive the signal of at least one \(T_{x}\), and for a fair comparison, the ADRs half-angle FoV is fixed to \(60^{\circ}\), being a typical value of the PDs we find in the market. The overall effective area (\(N_{PD}\ A_{p}\)) for ADRs is also assumed to be of the same value. By varying the position of the \(R_{x}\) around all possible locations in the underground mining scenarios, we can calculate the UDR. Figure 9 compares UDR distributions reached by the hemi-dodecahedron ADR in the mining roadway scenario. As we can see, all the signal combining schemes present a high data rate. However, to achieve these high data rates, it is necessary to reduce the ICI, which was achieved in this work. It is possible to infer, according to Figure 9, that when the \(R_{x}\) is below a \(T_{x}\)s, it reaches the maximum UDR. This observation is valid for all the techniques analyzed. By comparing Figure 9a-c, the technique that achieves the highest data rate is MRC (a maximum value of 250 Mbps and a minimum value of 50 Mbps). In contrast, the technique that has the worst performance is the EGC (maximum value of 140 Mbps and minimum value of 20 Mbps). In addition, the lobes diameter of the MRC UDR distribution are the largest on the surface, which is also relevant as it will provide a higher transmission rate per area. This performance was expected because the mechanism used by this scheme also assigns weights to the interference, which improves the quality of the combined signal in the receiver. Figure 10 compares UDR distributions reached by the pyramidal ADR in the mining roadway scenario. It is possible to recognize that there are similar characteristics with respect to Figure 9. However, if we compare the schemes of both Figures 9 and 10, the hemi-dodecahedron ADR has larger lobes per area, in addition to reaching higher values of UDR, compared to the pyramidal ADR. This is due to the fact that the geometric distribution of the hemi-dodecahedron ADR has a better performance in the decrease of ICI and an increase of the SINR with respect to the pyramidal ADR. By comparing Figure 10a-c, the technique that achieves the highest data rate continues to be the MRC (a maximum value of 180 Mbps and a minimum value of 20 Mbps). In contrast, the technique that has the worst performance is the EGC (a maximum value of 100 Mbps and a minimum value of 10 Mbps). Figure 9: UDR distribution of the hemi-dodecahedron ADR in the mining roadway scenario: (**a**) MRC, (**b**) EGC, and (**c**) SBC schemes. Figure 11 compares UDR distributions reached by the hemi-dodecahedron ADR in the mine working face scenario.