## 6 Results and Discussion
### Simulation Results and Disscusion
The reason is that the more computing resources tasks require, the fewer UEs that the LEO satellite can assist, many tasks are migrated to the BS for computing. The delay of OLC is the highest among all schemes, and the difference between OLC and JDORA-PGLMC is getting bigger and bigger. This proves that both the proper task offloading decision and the proper computing resource allocation are very important and can bring significant gain for UEs. As depicted in Figure 5, it is assumed that the data size of each task, i.e., \(a_{i}\) is the same, and the delay of all schemes increases with the increase of \(a_{i}\). Because bigger \(a_{i}\) will lead to higher task transmission delay and task migration delay. Moreover, when \(c_{i}\) is fixed, computing resources required by tasks are proportional to \(a_{i}\). In other words, task computing delay will also increase with the increase of \(a_{i}\). The delay of JDORA-PGLMC is much lower than that of JDORA-RDLMC, and the difference increases gradually, which indicates that potential game can make UEs' task offloading decisions effectively. The difference between JDORA-PGLMC's delay and JDORA-PGLMNC's delay represents the gain brought by migrating task from the satellite to the BS for computing. This gradually increasing difference proves the effectiveness and necessity of satellite-terrestrial coopera  
Figure 4: Delay vs. computation intensity. Figure 3: Delay vs. number of UEs. tion. The delay of JODRA-PGLMC is closest to that of OCO, and is furthest from that of OLC. This means that when \(N\) is small, e.g., \(N=40\), computation offloading can obtain more gain. The delay of JODRA-PGLMC is always the lowest among all schemes, which indicates that the proposed scheme can reduce UEs' task completion delay successfully. As shown in Figure 6, with the increase of computing resources of the satellite, i.e., \(F_{\rm S}\), the delay of all schemes except OLC presents a decreasing trend. In addition, the delay of JODRA-PGLMC, JODRA-PGLMNC, and OCO decreases slowly, while that of JODRA-RDLMC decreases rapidly. Because the more computing resources the satellite has, the more computing resources can be allocated to UEs' tasks, which reduces the task computing delay. However, computing resources of the satellite's MEC server are far less than those of the BS's MEC server, the gain brought for UEs is limited. Therefore, the number of UEs that offload tasks to the satellite for computing is relatively small. In JODRA-RDLMC, each UE is likely to offload its task to the satellite for computing, i.e., more tasks are computed by the satellite's MEC server. Therefore, its delay is affected by \(F_{\rm S}\) significantly. However, because the random decision is not optimal, its delay is high, even the highest when \(F_{\rm S}<12\) Gcycles/s. The delay of JODRA-PGLMC is lower than that of JODRA-RDLMC, indicating that a suitable task offloading decision can be obtained by potential game. Compared with JODRA-PGLMNC's delay, JODRA-PGLMC's delay is lower, and the difference between them is relatively stable, which illustrates that satellite-terrestrial cooperation is effective. The delay of OCO is higher than that of JODRA-PGLMC, which means that all UEs offload tasks to the MEC server is not optimal, and also indicates the importance of an appropriate task offloading decision. Because OLC is independent of computation offloading, its delay is not affected by changes of \(F_{\rm S}\), and remains unchanged basically. The great difference between its delay and JODRA-PGLMC's delay proves the effectiveness of the proposed scheme. As depicted in Figure 7, with the increase of computing resources of the BS, i.e., \(F_{\rm B}\), the delay of JODRA-PGLMNC and OLC remains unchanged basically, while the delay of other schemes decreases gradually. Since JODRA-PGLMNC and OLC do not involve the BS, their delay is not affected by the variation of \(F_{\rm B}\). The more computing resources the BS has, the more computing resources it can allocate to UEs' tasks, thus reducing task computing delay.