# Application and Performance Evaluation of Resource Pool Architecture in Satellite Edge Computing
## 4 Experiment and Analysis
### Results Comparison
#### 4.2.2 Task Failure Rate  
Compared with the task success rate, the task failure rate is the ratio of the number of failed tasks to the total number of initiated tasks in the simulation time. Before analyzing the task failure rate, it should be emphasized that the process of mapping the relationship between the three demonstration satellites and the satellites in the simulation platform is: select one in the orbit of 3600 km, one in the orbit of 1100 km, and one in the orbit of 550 km. At the same time, because the visible window of 550 km orbit to the earth is very small, the sample demonstration satellite mapped with 550 km orbit changes periodically, while the other two are fixed in mapping. This is set to ensure the authenticity and randomness of the data. This paper counts the task failure rate in instances of failure caused by mobility, insufficient resources, and unsatisfied delay.  
The results of the task success rate can be seen in Figure 9, where it is shown that pooled and cooperative modes greatly improve the task success rate. We analyze the causes of task failure through Figures 10-12. As can be seen from Figure 10, pooled mode and cooperative mode can share resources, which solves the problem that arises when tasks fail without resources. The failure rate is reduced from 51.45% (peak at 75.00%) in isolated mode to 1.64% (peak at 8.57%) in both pooled and cooperative mode. However, resource sharing brings other problems. The first is in terms of delay. Both pooled mode and cooperative mode need to transfer information with other satellites, migrate tasks, and send information and executable software, which will cause delays. Tasks with high real-time requirements may lead to task failure. Therefore, in the pooled mode and cooperative mode, the task failure caused by delay is higher than that in the isolated mode. The task failure caused by delay in isolated mode is stable at approximately 25.19% in Figure 11, because it is only processed locally, and the task queue brings delay. The reason for the decrease in task failure rate in pooled mode and cooperative mode is that, when there are few tasks, the task planning algorithm pursues the resource load balance of the system and allocates tasks in the resource pool as much as possible, which will make some tasks fail with a probability of 57.40%.  
In addition to the two issues mentioned above that may cause task failure, mobility is also a key factor in satellites. Task failure due to mobility refers to the satellite leaving the target area due to the orbital motion of the satellite, or that it is invisible to other satellites. Figure 12 shows that the proportion of this part is small, up to only 3%. Interestingly, cooperative and pooled modes have higher failure rates caused by mobility than the isolated mode. The reason for analyzing the data is that the probability of delay and mutual invisibility caused by data transmission in resource sharing has increased, but the value is still very small. In the isolated mode, the task failure rate is relatively low because the task is only sent to the satellite visible to the target, and the task is only executed locally.  
Figure 9: Task success rate.