# A Novel and Adaptive Angle Diversity-Based Receiver for 6G Underground Mining VLC Systems
## 4 Results and Discussion
### Distribution of the Received Power  
Figure 3 shows the distribution of the power received by the hemidodecahedral ADR with PDs with adaptive orientation, with a fixed orientation, and with the ToA method as well as the distributions for pyramidal ADRs with fixed PDs and with the ToA method. These distributions are calculated based on Equations (2) and (21). We evaluate the received power by keeping the coordinate \(z\) of the ADRs with a value of 1.8 m because it is a typical  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**UM Simulation Scenario** & **Values** & **Ref.** \\ \hline \hline
**Tunnel Parameters** & & \\ \hline Dimensions (\(w\times l\times h\)), m & \((3\times 6\times 5)\) & \\ Coordinates of the \(LED\)\((x,y,z)\), m & \(LED_{1}=(3,1.5,4.5)\), \(LED_{2}=(3,3,4.5)\), & \\  & \(LED_{3}=(3,4.5,4.5)\), \(LED_{4}=(-3,6,4.5)\) & \\ \hline \hline
**Channel and element parameters** & & \\ \hline AWGN power spectral density (A/Hz) & \(2.5\times 10^{-23}\) & [22] \\ LED rotation angle, (\({}^{\circ}\)) & 45 & [7] \\ LED tilt angle, (\({}^{\circ}\)) & 45 & [7] \\ Noise bandwidth (MHz) & 100 & [23] \\ Wall reflection coefficient, \(\rho_{w}\) & 0.6 & [7] \\ Wall rotation angle, (\({}^{\circ}\)) & \(U[0,180]\) & [7] \\ Wall tilt angle, (\({}^{\circ}\)) & \(U[0,180]\) & [7] \\ \hline \hline
**VLC transceiver parameters** & & \\ \hline Average transmitted power, \(P_{t}\) (W) & 5 & [24] \\ Band-pass filter of transmission & 1 & [6] \\ FoV, \(\Theta\) (\({}^{\circ}\)) & 70 & [24] \\ Gain of the optical filter & 1 & [24] \\ Lambertian mode number, \(m\) & 1 & [25,26] \\ LED wavelength, \(\lambda\) (nm) & 580 & [24] \\ Modulation type & OOK & [27] \\ Modulation bandwidth (MHz) & 50 & [27] \\ Modulation index & 0.3 & [27] \\ Optical filter bandwidth (nm) & 340 to 694.3 & [24] \\ Optical filter center wavelength (nm) & 580 \(\pm\) 2 & [24] \\ Optical filter full width half max (nm) & 10 \(\pm\) 2 & [24] \\ Physical active area, \(A_{p}\) (cm\({}^{2}\)) & 1 & [6] \\ Reflective element area, \(\Delta A_{w}\) (cm\({}^{2}\)) & 1 & [21] \\ Refractive index, \(m_{s}\) & 1.5 & [6] \\ Responsivity, \(R_{PD}\) (A/W) & 0.53 & [6] \\ Semi-angle at half power, (\({}^{\circ}\)) & 60 & [24] \\ \hline \end{tabular}
\end{table}
Table 1: UM-VLC system simulation parameters.  
position value of the communication devices in these scenarios. In addition, \(P_{t}\) is set to 5 W to provide constant lighting in the UM tunnel.  
In the first instance, we can see that by implementing the ToA method in the hemidodecahedral ADR, we improve the power received compared to the same ADR with fixed PDs by 20%. In addition, by implementing this method in the pyramidal ADR and comparing it with its pair with fixed PDs, we also improve the power received by 10%. However, if we compare them with our proposal and take as a precedent that the hemidodecahedral ADR by itself improves the efficiency of the received signal with respect to the pyramidal ADR, we can observe that the presented proposal (Figure 3a) presents the best performance in terms of the evaluated metric compared to its evaluative ADR peers. Indeed, we have power values between \(-45.3\) and \(-81.2\) dBm for the hemidecahedral ADR with PDs with adaptive orientation. This effect of improvement of the received power is due to the automatic orientation that the PDs have in the array. Therefore, wherever the ADR is in the UM-VLC scenario, it will always point its PDs in the direction that maximizes the power gain.  
Figure 3: Distribution of the received power in the UM-VLC scenario with (**a**) hemidodecahedral ADR with PDs with adaptive orientation, (**b**) hemidodecahedral ADR with PDs fixed, (**c**) hemidodecahedral ADR with the ToA method, (**d**) pyramid ADR with the ToA method, and (**e**) pyramid ADR with the PDs fixed.