# Impact of Weather Factors on Unmanned Aerial Vehicles' Wireless Communications
## 3 Results and Discussion
### Atmospheric Weather Variations
The bandwidth reduction in MHz is shown in the \(B_{red\_LP}\) and \(B_{red\_HP}\) columns corresponding to the low and high-power modes, respectively. Given that both free-space path loss and weather-induced attenuation decrease at lower frequencies, maintaining the required SNR for a specified BER threshold necessitates a reduction in operating frequency when the power transmission decreases or weather conditions deteriorate. Consequently, the LPIW condition results in having the lowest values for \(f_{max}\). Conversely, an increase in power transmission and the presence of favorable weather conditions result in higher \(f_{max}\) attainment, as the increased path loss due to the utilization of higher operating frequency is mitigated by the elevated power transmission and reduced attenuation associated with mild weather conditions. As such, the HPMW condition results in having the highest values for \(f_{max}\). It can be observed in Table 4 that \(B_{rd}\) is minimally affected at lower power transmissions. This is attributable to the fact that, at lower power transmissions, the corresponding \(f_{max}\) is inherently smaller, and as weather conditions deteriorate, the increase in attenuation is comparatively smaller. The noise power remains constant due to the fixed temperature and operating bandwidth, resulting in a relatively smaller reduction in SNR. Consequently, no discernible difference in \(B_{rd}\) is observed for the gases and cloud/fog-influenced weather conditions at the assumed lower power transmission. The highest \(B_{rd,LP}\) of 364 MHz is observed in association with rain for BPSK and QPSK. The \(B_{rd}\) decreases substantially to 3 MHz and 1 MHz for 16-QAM and 64-QAM, respectively. No changes in \(f_{max}\) are observed for 256-QAM, making the corresponding \(B_{rd}\) equal to zero. By contrast, \(B_{rd}\) exhibits maximum susceptibility at higher power transmissions, as a greater value of associated \(f_{max}\) results in significant atmospheric attenuation under deteriorating weather conditions. With noise power remaining constant, this phenomenon leads to a more substantial degradation of SNR, consequently necessitating a larger reduction in \(f_{max}\), and ultimately resulting in maximum \(B_{rd}\). A bandwidth reduction of 1 MHz is observed for BPSK/QPSK and 16-QAM under gas-based inclement weather conditions, while the operating bandwidth remains unaffected for 64-QAM and 256-QAM due to their lower \(f_{max}\). In the presence of cloud/fog-based inclement weather conditions, higher atmospheric attenuation results in a greater reduction in \(f_{max}\), consequently leading to a more substantial \(B_{rd}\). Specifically, for BPSK/QPSK, 16-QAM, and 64-QAM, \(B_{rd}\) values of 295 MHz, 53 MHz, and 37 MHz are observed, respectively. Incoherent rainy conditions result in maximum \(B_{rd}\) due to the highest atmospheric attenuation. For BPSK/QPSK, 16-QAM, 64-QAM, and 256-QAM the \(B_{rd}\) values are 2075 MHz, 672 MHz, 76 MHz, and 1 MHz, respectively. Currently available UAVs' operations are based in the \(<\)10 GHz _bands_. Accordingly, our simulation for BER is for the frequency region of 1 to 10 GHz. Splitting this band in lower and higher regions, the lower bandwidth regions correspond to frequencies below 5 GHz.