## 6 Results and Discussion
This is because when the arrival rate of mMTC increases at the beginning, the SCR also incrementally increases. After that, the SCR curves move into a peak or max value because all the C-RAN resources have started to be completely utilized. Further, we can observe from the figure that, in addition to the queuing model, increasing the queue size will improve the SCR of the mMTC service. When we increase the queue size from 4 to 8, the curve of the SCR shows better improvements. Therefore, increasing the queue size allows extra requests to potentially be queued. Since the requests of uRLLC have a fixed rate and those of mMTC have an increasing rate, this leads to more queued mMTC requests and a higher probability that mMTC services will complete their service connection. Hence, the SCR increases by increasing the queue size. Now, comparing the SCR using Methodologies II and III, it can be seen that Methodology III results in a higher SCR as compared with Methodologies II with no feedback link for interrupted mMTC requests. In regards to Methodology II, all interrupted mMTC requests will be forced to terminate the service even if the 2 QmMTC has available resources, and interrupted requests will be ignored during SCR calculations. However, the SCR behavior in Methodology III is improved as compared with that in Methodology II because the in-service mMTC requests that have been interrupted are given a second chance to join the queue and reat-tempt accessing resources. With this feedback link, Methodology III outperforms other methodologies in terms of SCR rate. In Figure 7, the PF of mMTC requests is depicted against the arrival rate of uRLLC. The main goal of this figure is to explain the effectiveness of Methodologies II and III when the arrival rate of the uRLLC request with the highest priority increases. As we can see from the figure, as the arrival rate of uRLLC requests increases, the PF for mMTC requests increases using all methodologies. The reason behind this behavior is that when eMBB and mMTC requests are forced to terminate by the higher priority slice, the arrival rate of uRLLC keeps increasing, thus increasing the usage of C-RAN resources. When the system accepts more uRLLC requests, many in-service eMBB or mMTC requests will be interrupted, and most of the BBUs will have been taken by the arrival of uRLLC requests. In addition, the PF of the mMTC requests does not improve much with or without using two queues (Methodology II). The reason is that when we allow the eMBB and mMTC requests to be queued, the interaction between them and the uRLLC request will be greater than when we have no queues. This interaction will result in an increase in the calculated PF. Figure 6: **mMTC** SCR as a function of the **mMTC** arrival rate. Therefore, allowing the arrival request of mMTC to be queued is not enough, and an effective method should be used to efficiently minimize the PF of mMTC. Methodology III is proposed to solve this issue by allowing all requests that have been interrupted to rejoin the queue while there are free spaces in it and it is not full. In addition, increasing the queue size to 2 QmMTC can also minimize the PF. Finally, it is clear that the idea of Methodology III can be selected as a better solution for having a lower PF. As illustrated in Figure 8, the average queuing delay of mMTC requests for both Methodology II and III is studied and compared. As we can see, the performance of Methodology II outperforms that of Methodology III in terms of average queuing delay. The reason for this is that when we allow the interrupted mMTC request to rejoin its queue, the average queue size will increase. Increasing the number of queued requests will increase the average queuing delay, as the queue length is directly proportional to the average delay as derived in the analytical model. Therefore, Methodology III reduces the PF of mMTC requests and increases their average queuing time. Therefore, there is a tradeoff between increasing the average delay and decreasing the PF for mMTC requests.