# Federated Learning-Based Service Caching in Multi-Access Edge Computing System
## 5 Experiment and Evaluation
### Performance Evaluation
#### 5.4.2 Comparison of Service Delay  
Figure 9 illustrates the average latency of the entire system during each operation. The evaluation is conducted by varying the computational capacity per MEC from 12 to 72 GHz in a system including 64 MEC servers and 300 users. SCFL demonstrates minimal delay when compared to the other approaches. When the computational resources of each server is set at 12 GHz, the delay incurred when using RC exceeds 200 s. In contrast, the corresponding latency for SCFL is approximately 140 s. On the other hand, as the resource capacity increases to 72 GHz, the latency of the complete system decreases to less than 80 s when using SCFL, compared to 105 s when using FLAE. This demonstrates the outstanding capability of SCFL in selecting suitable services. The substantial correlation between the services chosen and requests made by users enables handling these requests at the local MEC server rather than sending them to the cloud server, which increases the system latency.  
Figure 8: Service hit ratio with different numbers of MEC servers.  
Figure 7: Service hit ratio with different number of users.  
The service delay of the entire system in each operation time slot with different numbers of users is shown in Figure 10. The experiments include a simulation of systems with 64 MEC servers, each providing a computational capacity of 36 GHz. The number of users varies from 50 to 250. It can be seen that the number of service requests received by MEC servers increases as the number of users in the system increases. Consequently, the number of requests the cloud server handles increases, resulting in increased latency for the entire system. When the number of users is 50, the service latency in the system using SCFL and FLAE is 35 and 48, respectively. In addition, LFU, LRU, and RC cause a latency of 55, 57, and 73 s, respectively. When the number of users reaches 250, the use of SCFL results in a system latency of approximately 100 s. In comparison, FLAE reveals a latency of approximately 125 s under the same conditions. Moreover, implementing LRU and RC in a system with 250 users results in a delay of over 150 s. Therefore, SCFL demonstrates outstanding effectiveness in providing services to different numbers of users.  
Experiments are conducted to evaluate the overall latency of the system containing different numbers of MEC servers. The number of MEC servers increases from 16 to 64, with each server having a computational capacity of 36 GHz. The service is utilized by a total of 300 mobile users. Notably, the area and coordinates of the experimental area are unchanged. Therefore, when increasing the number of MEC servers, the coverage area of  
Figure 10: Service delay with different numbers of users.  
Figure 9: Service delay with different computational capacity of each MEC server.  
each MEC server will become smaller. The experimental results are shown in Figure 11. When the system comprises only 16 MEC servers, the average latency in a single round using SCFL is approximately 80 s, whereas that of the other methods exceeds 100 s. When the number of deployed servers is increased to 64, the system using SCFL experiences a minor increase in latency, reaching 90 s. In the same settings, RC, LRU, and LFU result in service delays of 170, 151, and 132 s, respectively. It is evident that using SCFL consistently results in minimal system delay compared to other approaches.