# Flying Ad Hoc Networks: A New Domain for Network Communications
## 2 State of the Art
### Results
Figure 12: Example of a measurement of the complete radiation pattern and example of possible areas of interest for each communication link, which are highlighted in green for the U2U link and yellow for the U2G link: (**a**) X Plane, (**b**) Y Plane, and (**c**) Z Plane. was the gain of the antennas. For this U2G link, it must be adjusted to achieve a main lobe width of about 90 degrees, which allowed us to adjust it to the region of interest from 135\({}^{\circ}\) to \(-\)135\({}^{\circ}\). This gain presented its optimal value for the 2.4 GHz band with a gain of 8 dBi, compared to 10 dBi in the 5 GHz band. However, the 5 GHz option would provide a narrower lobe that did not fit our region of interest. On the other hand, for the U2U links, since an omnidirectional radiation pattern was necessary in the X plane (see Figure 12), the best results were obtained with the ARS-NT5B antennas in a vertical position, as can be seen in Figure 13.  
Figure 14: Radiation pattern of the isolated WiTi using the antennas configuration shown in Figure 13 in the U2G link working in 2.4 GHz: (**a**) X Plane, (**b**) Y Plane, and (**c**) Z Plane. Figure 13: The best antenna configurations of the WiTi as seen from above: 2.4 GHz band for the U2G link with APA-M25 antennas in horizontal position with 90\({}^{\circ}\) between them and 5 GHz band for the U2U link with ARS-NT5B antennas in vertical position. Figure 15: Radiation pattern of the isolated WiTi using the antennas configuration shown in Figure 13 in the U2U link working in 5 GHz: (**a**) X Plane, (**b**) Y Plane, and (**c**) Z Plane. The goal of the second set of experiments was to study the influence (if any) of the UAV chassis, the UAV motors (RPMs and vibrations produced in antennas and chassis), and the UAV propellers on the radiation pattern in both the 2.4 GHz and 5 GHz bands. To do so, the WiFi was located on-board the UAV, and continued operating as a client, thus transmitting data to the server device. Once inside the RF anechoic chamber, we took measurements in the following states: UAV off, UAV on with engines at 45% of its power with and without propellers, UAV on at 65% power without propellers, and UAV on at 95% power without propellers. The results obtained indicate that the influence of the drone in the radiation pattern was mainly due to the chassis. The impact of propellers, of the power of the engines, and of the vibration produced by the engines was negligible in our study. In our opinion, all the system is equilibrated without vibrations because we were using a brushless motor and the propellers were made of plastic. This result could be different if carbon fiber propellers were used, which requires further work. Regarding the effect of the UAV chassis, it was more notable in the Y and Z planes. Thus, the U2G link (Planes Y and Z) was more affected, with a variation of the received power of up to \(-10\) dB in the 2.4 GHz band (the band utilized for the U2G link), which means that the power falls to a tenth of the original value in both working bands. Regarding the X plane in the 2.4 GHz band, we could observe a \(-5\) dB in some angles, reducing the power to almost a quarter of its original value. Figure 16 illustrates the change in the radiation pattern when the WiFi was used alone or when it was used as a communication device on-board the UAV in the 2.4 GHz band in the X plane (see Figure 16a) and in the Y plane (see Figure 16b), and in the 5 GHz band in the X plane (see Figure 16c) and in the Y plane (see Figure 16d). The results obtained in the Z plane were identical to the Y plane. From these observations, incorporating the influence of UAV in propagation models could be done by modeling the UAV as additional system losses. For UAVs like the one employed in this study, the system loss was equivalent to \(-10\) dB on the U2G link and \(-5\) dB for the U2U link.