## 3 Results and Analysis of the Ground Test
### Transmission Capability Test of the Airborne Communication System
#### 3.2.2 Test Method and Results  
In order to achieve test in the ground environment, a ground motion carrier is chosen for the communication system in the motion environment, approximating a bumpy flight state, and a ground simulation communication link is built. In this test, the manual pushing method is used in a suitable terrain, loading the communication antenna (Figure 5a). As shown in Figure 5a, the transmitting end is a flat antenna (with an equivalent diameter of 0.45 m) in the airborne mobile communication equipment. A parabolic antenna of 4.5 m is used to receive data in the ground station. The testing satellite is AsiaSat-5 communication satellite with a working frequency of 14,470 MHz. Static and dynamic tests are conducted at 256 Kbps, 512 Kbps, 1024 Kbps, and 2048 Kbps transmission bandwidths. The static test refers to the process where the onboard antenna is aligned with the satellite and no longer moves, while the dynamic test refers to the process of aligning the airborne antenna with the satellite and then moving the antenna base position along an 8-shaped trajectory on a site with a slight slope on the ground. During the testing process, the communication system will send the pre-stored image data to the processing center near the ground station via satellite. The processing center will then transmit the received images back to the communication system. Finally, the success rate of the first transmission is calculated.  
On 20 September 2020, the communication capability test on ground was conducted in an open parking lot in Beijing with a slope of 20\({}^{\circ}\). The road conditions were sandy and gravel, providing a certain shaking and bumpy environment for the test. The test results are shown in Table 4. As shown in the table, the transmission rate of the mobile communication equipment meets the requirement of 2 Mbps bandwidth. Under this bandwidth condition, the data packet loss rate is only 0.2% in the static environment, and data packet loss rate is 0.5% in the dynamic environment, both of which meet the requirements. Based on the use of image compression function (no less than 16 times), this indicates that 1080P video and high-resolution images of no less than 32 Mbps can be transmitted in real-time in the later stage.  
In summary, the dynamic environment provided by the ground test conditions of the communication equipment is relatively harsh compared to the flight environment, with a pitch slope close to 20\({}^{\circ}\), exceeding the typical aircraft sway amplitude of about 10\({}^{\circ}\). At the same time, simulate the vibration of the aircraft fuselage through testing on sand and gravel road surfaces. Therefore, the experimental results in this environment have high reference value. In addition, the airborne communication system is driven using servo motors and leaves a margin of over 30% for motor capability, which means that the communication system can maintain tracking accuracy in flight maneuvers that are more severe than ground test environments. The components used in the communication system are also wide temperature devices, and the machined parts have undergone surface anodizing or  
Figure 5: Photos of the testing systems. (**a**) The carrier of the mobile communication system in the ground test. (**b**) The system composition in the flight test.  
chrome plating treatment, which can adapt to external environments ranging from \(-30\)\({}^{\circ}\)C to 65 \({}^{\circ}\)C. The entire equipment was placed in a high and low temperature box for high and low temperature operation testing and assessment, and it can also maintain normal working conditions, indicating that the equipment can adapt to the airborne environment.