# Flying Ad Hoc Networks: A New Domain for Network Communications
## 2 State of the Art
### Experimental Setup  
This section details the hardware, software, and test bench used to study the complete radiation pattern in a fully-controlled experimental environment. The UAV used in the experiments was the IdeaflyIFLY-4S (Shenzhen Idea-Fly Technology Co.,Ltd, ShenZhen, China), a quadcopter with carbon fiber chassis, brushless motors, and interchangeable plastic propellers. A wireless communication module was added to this UAV; specifically, the open firmware router WiFi Board (hereinafter WiTi, mqmaker, Shenzhen, China) [66]. It is based on OpenWRT v14.07 with dual band and two antenna connectors for each band, thus allowing the connection of up to four antennas at the same time. The communication chipsets were the MT7602E that supports 802.11 b/g/n WiFi 2T2R and the MT7612E that supports 802.11 a/b/g/n/ac WiFi 2T2R, using the 2.4 GHz and 5 GHz bands, respectively. Both chipsets can work independently and concurrently. Figure 9 shows the UAV and the WiFi device. Two types of dual-band antennas were employed, namely, antennas with an omnidirectional radiation pattern and 5 dBi gain in both bands (ARS-NT5B, Alfa Network, Taipei, Taiwan) and directional patch antennas with a gain of 8 dBi for 2.4 GHz and 10 dBi for 5 GHz (APA-M25, Alfa Network, Taipei, Taiwan). The R&S ZVL spectrum analyzer (Rohde & Schwarz, Inc., Columbia, MD, USA) was used in reception to capture signals up to 6 GHz, along with the R&S receiver antenna HP906 (Rohde & Schwarz, Inc., Columbia, MD, USA) with a large reception bandwidth (between 1 GHz and 18 GHz) and a constant gain (10 dBi for 2.4 GHz and 11 dBi for 5 GHz). Finally, the employed RF anechoic chamber was a full chamber with isolation cones that prevent electromagnetic waves from bouncing off walls, ceilings, and floors. The dimensions of the RF anechoic chamber were 5.2 m \(\times\) 3.5 m \(\times\) 2.25 m. The rotary table INN-CO DE 3260-P was located inside the chamber and controlled by the digital controller INN-CO CO 2000.  
The UAV with the embedded WiFi were placed on the rotary table. The WiFi was configured to act as a transmitter (client) in a session of data transmission. To this end, the traffic generator iperf v2.0.9 [10] was used in its default configuration to send TCP (transport control protocol) traffic. A USB-WiFi device located inside the RF anechoic chamber and controlled by a computer from outside the chamber was used as the server of the session. While the rotary table was rotating, the ZVL spectrum analyzer connected to the HF906 antenna captured the power transmitted by the WiFi. Power measurements were taken every 10 degrees, in a bandwidth of 20 MHz centered on the center frequency with a resolution bandwidth of 3 kHz, thus eliminating the limits of the working band and remaining in a flat spectrum in frequency. The captured power was averaged and a value representing the power received for each rotation angle (36 in total) was obtained at a distance of 3 m and a height of 1.5 m (fulfilling the condition of far field for both working bands and both antennas). The complete test bench scenario is shown in Figure 10. Table 5 summarizes the test bench parameters.