# Impact of Weather Factors on Unmanned Aerial Vehicles' Wireless Communications
## 3 Results and Discussion
### Atmospheric Weather Variations
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & \multicolumn{3}{c}{\(P_{\text{rx}}\):25 mW} & \multicolumn{3}{c}{\(P_{\text{rx}}\):75 mW} \\ \hline
**Atmospheric** & & & & & & \\
**Attenuation** & **Modulation** & & & & & \\
**Factors** & **(\(\downarrow\))** & & & & & \\
**(\(\downarrow\))** & & & & & & \\ \hline \multirow{6}{*}{\(\text{Gases}\)} & \multirow{2}{*}{\(\text{RPSK/QPSKK}\)} & 0.23 & 23.01 & & 0.23 & 23.01 & \\  & & (g/m\({}^{3}\)) & (g/m\({}^{3}\)) & & (g/m\({}^{3}\)) & (g/m\({}^{3}\)) & \\  & BPSK/QPSK & 4.000 & 4.000 & 0 & 6.901 & 6.900 & 1 \\  & 16-QAM & 2.636 & 2.636 & 0 & 4.556 & 4.555 & 1 \\  & 64-QAM & 1.636 & 1.636 & 0 & 2.895 & 2.895 & 0 \\  & 256-QAM & 1.000 & 1.000 & 0 & 1.727 & 1.727 & 0 \\ \hline \multirow{6}{*}{Clouds/Fog} & \multirow{2}{*}{\(\text{I}wd\)} & 0.05 & 10 & & 0.05 & 10 & \\  & (g/m\({}^{3}\)) & (g/m\({}^{3}\)) & & (g/m\({}^{3}\)) & (g/m\({}^{3}\)) & \\ \cline{1-1}  & BPSK/QPSK & 4.000 & 4.000 & 0 & 6.895 & 6.600 & 295 \\ \cline{1-1}  & 16-QAM & 2.636 & 2.636 & 0 & 4.558 & 4.505 & 53 \\ \cline{1-1}  & 64-QAM & 1.636 & 1.636 & 0 & 2.895 & 2.858 & 37 \\ \cline{1-1}  & 256-QAM & 1.000 & 1.000 & 0 & 1.727 & 1.727 & 0 \\ \hline \multirow{6}{*}{Rain} & \multirow{2}{*}{\(R_{r}\)} & 1 & 120 & & 1 & 120 & \\  & & (mm/h) & (mm/h) & & (mm/h) & (mm/h) & \\ \cline{1-1}  & BPSK/QPSK & 4.000 & 3.636 & 364 & 6.893 & 4.818 & 2075 \\ \cline{1-1}  & 16-QAM & 2.636 & 2.633 & 3 & 4.557 & 3.885 & 672 \\ \cline{1-1}  & 64-QAM & 1.636 & 1.635 & 1 & 2.894 & 2.818 & 76 \\ \cline{1-1}  & 256-QAM & 1.000 & 1.000 & 0 & 1.726 & 1.725 & 1 \\ \hline \hline \end{tabular} \(d\): 2000 m, \(h\): 400 m, \(T_{a}\): 25 \({}^{\circ}\)C, \(P_{a}\): 1013.25 hPa, \(B_{rd}\): 20 MHz.  
\end{table} 
Table 4: Comparison of \(f_{\text{max}}\) and \(\text{B}_{\text{red}}\) under different power transmissions. Our results demonstrate that, at a lower bandwidth corresponding to the lower frequency region (<5 GHz), the BER remains below the threshold of 1% for all modulation schemes and weather conditions considered. As attenuation decreases with a reduction in frequency, for UAVs operating at frequencies <1 GHz, the BER is anticipated to improve, resulting in enhanced communication reliability. Hence, for lower UAV operations in lower frequency regions and occupying smaller bandwidths, no explicit evaluation of BER is needed. In brief, the key insights can be summarized as follows:  
* \(f_{max}\) tends to reduce with reduction in power transmission and worsening of weather conditions
* \(f_{max}\) tends to increase with the increase in power transmission and weather conditions becoming milder
* At lower power transmissions, inclement weather conditions cause minimum bandwidth reduction
* At higher power transmissions, inclement weather conditions result in maximum bandwidth reduction
* Lower bandwidth reduction is seen with a higher order modulation scheme  
These observations, as seen in our simulation-based studies, are apt for algorithmic development to dynamically control the operating frequencies in UAV operations. Figure 12 is another representation of the results given in Table 4. It shows the variations in maximum operating frequency and bandwidth reduction resulting from alterations in meteorological conditions under distinct power transmissions and modulation schemes. The columns marked (a) and (b) represent the power transmissions of 25 mW and 75 mW, respectively. The plots in the top, middle, and bottom rows correspond to gases, clouds/fog, and rain-based attenuation and resulting \(f_{max}\) and \(B_{red}\) for various modulation schemes, respectively. Figure 12: Variations in maximum operating frequency and bandwidth reduction resulting from alterations in meteorological conditions under distinct power transmissions and modulation schemes. Figures in column (**a**) depict the results for a power transmission of 25 mW. Figures in column (**b**) illustrate the results for a power transmission of 75 mW. For all scenarios, distance and height are 2000 m and 400 m, respectively.