# Satellite IoT Edge Intelligent Computing: A Research on Architecture
## 4 Results and Discussions
### Satellite IoT Connectivity and Coverage Performance  
Unlike the ground-based IoT, the satellite IoT needs to consider high-speed dynamic topology. Fortunately, the satellite IoT can be designed based on satellite constellation, the network topology hasperiodic changes, and the motion of the nodes becomes predictable, which also facilitates the analysis of the satellite IoT. Below, we analyze the connectivity and coverage performance of the satellite IoT. We simulated the connectivity and coverage performance of the satellite IoT through the _STK11.5_ (Satellite Tool Kit) simulation software. The constellation of satellites is set to the 66/6/1 Walker constellation, with 66 satellites, 6 orbital planes, and 11 satellites per orbital plane. Each satellite has a height of 1500 km, an orbital inclination of 90\({}^{\circ}\), and a half-cone angle of 50\({}^{\circ}\) detected by the sensor. By setting the above parameters in the STK software, we can obtain pictures of different perspectives of the entire satellite IoT, as shown in Figures 5 and 6. Figure 5 shows the communication connection between each satellite in a real scene. The green line indicates the communication link between the satellite and the satellite. Assuming that a satellite communicates with four azimuth satellites, it can be found that these satellites form a network of multiple quadrilaterals, and the entire satellite Internet of Things is like a network covering the whole world. Figure 6 shows the projection of the communication link between each satellite in a two-dimensional plan view of the Earth. Due to the curvature of the Earth, under the two-dimensional plan of the Earth, the projection of the communication link between each satellite will be interlaced in the South Pole and the Arctic. The reason for this phenomenon is that, when the three-dimensional sphere is unfolded  
Figure 5: Three-dimensional plan of the satellite Internet of Things. (**a**) Observation point of Sat1205; (**b**) Observation point of Sat1404. Figure 6: Two-dimensional plan of the satellite Internet of Things. into a two-dimensional plane, the graphic display at the two-pole position is elongated, but, in reality, the communication link remains connected. The STK connection module can calculate the connection data for each satellite. Taking the satellite Sat1205 as an example, through the STK to simulate the trajectory of satellite motion, we observe the link connection of the Sat1205 satellite. By recording the link connection of the Sat1205 satellite, we can see that the Sat1205 satellite can maintain a stable communication link with the surrounding satellites within 24 hours of satellite motion. The connection characteristics of the satellite Sat1205 with the satellites Sat1105, Sat1204, Sat1206, and Sat1305 are shown in Table 1.  
As can be seen from the table, each satellite can establish a link with four adjacent satellites for a long time, and the link distance between two adjacent satellites in the same orbit remains unchanged (satellite Sat1205 has the same orbital surface as satellite Sat1204 and Sat1206). The link distance between satellites on adjacent orbital planes changes periodically. Next, we analyze the coverage performance of the satellite IoT. We simulated the global coverage performance of the satellite IoT through STK and calculated it at a point granularity of 3 deg. The percentage of global satellite IoT coverage and the ratio of different latitude coverage times during the day were recorded. Figure 7 shows the coverage characteristics of the entire satellite IoT sensor. By observing the coverage of the satellite IoT sensor in Figure 7, and using STK to calculate the coverage parameters, we record the coverage characteristics of the satellite IoT in Table 2. It can be found from Table 2 that the installed satellite IoT cumulative coverage rate is 100%, and the coverage time of different latitudes also reaches 100%.