## 3 Numerical Results
### Effect of Drone Azimuth Rotation  
The influence of drone azimuth rotation on the drone VLC is of great significance to be investigated. As for the NSPW drone VLC, as shown in Figure 7, it could be observed that the periodicity in energy efficiency performance is 180\({}^{\circ}\) in rotation angle cycle for the concerned positions of the terrestrial user, and the fluctuating energy efficiency performance appears under the same azimuth rotation angle of the NSPW drone. Specifically, for the side position and the side position 2 of terrestrial users, up to 2.87 Bits/J/Hz energy efficiency fluctuation can be achieved by leveraging of drone azimuth rotation angle. For the terrestrial side position 2, the maximum energy efficiency of \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Performance Metric**} & \multicolumn{3}{c}{**Lambertian Drone VLC**} & \multicolumn{3}{c}{**Z-Power Non-Lambertian Drone**} & \multirow{3}{*}{**NSPW Non-Lambertian Drone VLC**} \\  & & & & & **VLC** & & \\ \cline{3-8}  & & **Emitted Power** & **Emitted Power** & **Emitted Power** & **Emitted Power** & **Emitted Power of** & **Emitted Power of** \\  & & **of 100 mW** & **of 100 mW** & **of 100 mW** & **of 100 mW** & **100 mW** & **100 mW** \\ \hline \multirow{4}{*}{Achievable rate (Bits/Hz)} & Receiver & & & & 4.89 (side position), & 11.53 (side position), & 11.53 (side position), & 11.40 (side position), & 14.40 (side position 2) \\  & & & & & & 0.0066 (side position), & \\  & & & & & & 1.22 (side position) & 7.71 (side position) \\  & & 2.5 m & & & & & position 2) \\ \hline \multirow{4}{*}{Energy efficiency (Bits/J/Hz)} & Receiver & & & & 48.86 (side position), & 11.53 (side position), & 11.53 (side position), & position), \\  & & 63.83 & 13.03 & 46.71 & 11.31 & 77.56 (side position) & 14.40 (side position 2) \\ \cline{1-1}  & & & & & & 2) & 0.066 (side position), & \\ \cline{1-1}  & & & & & & 12.16 (side position), & 7.71 (side position 2) \\ \hline \multirow{4}{*}{Energy efficiency (Bits/J/Hz)} & Receiver & & & & 3.27 (side position), & 0.066 (side position), & \\  & & 2.5 m & & & & 12.16 (side position) & 7.71 (side position 2) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results summary of the emitted power effect for Lambertian and non-Lambertian drone VLC. Figure 7: Comparison of energy efficiency versus azimuth rotation angle for drone VLC with asymmetric NSPW light beam configuration. 14.40 Bits/J/Hz is achieved with the 0\({}^{\circ}\) drone azimuth rotation, while for the terrestrial side position, the minimum achievable rate of 11.53 Bits/J/Hz is achieved with the same drone azimuth rotation. And the maximum energy efficiency of 14.40 Bits/J/Hz is achieved for the terrestrial side position, when the drone azimuth rotation is varied to about 90\({}^{\circ}\). As for the corner position, once the drone azimuth rotation is up to about 50\({}^{\circ}\), the relevant maximum energy efficiency of 11.67 Bits/J/Hz is achieved. As for the situation of 2.5 m receiver altitude, the homologous periodicity in energy efficiency performance can be identified with the various drone azimuth rotations for the different aerial positions. Note that the rotation angle cycle is also 180\({}^{\circ}\) for the concerned three positions of the aerial user; diverse energy efficiency performances appear under the same azimuth rotation angle of the transmitter drone. The above figures of azimuth rotation effect indicate that the link performance of NSPW non-Lambertian drone VLC is highly relevant to the azimuth rotation angle of the involved drone, especially for the side position and corner position of the VLC receiver. The main reason for these phenomena is that the rotational asymmetry radiation characteristic of this distinct non-Lambertian beam. Objectively, these phenomena provide a novel potential solution to selectively enhance the coverage performance for users in a certain azimuth direction.