# A Framework for the Joint Placement of Edge Service Infrastructure and User Plane Functions for 5G
## 4 Framework Proposal
### UPF Placement Stages
#### 4.2.2 Near-Optimal UPF Placement
For the second group of services (see Figure 6) all the solutions had similar results for all the scenarios and values of capacity considered, except for \(C_{u}=1.5\) Tb/s in City_2, where NOUP_M1 obtained one UPF more than the other three methods. In general, a reduction in the number of UPFs with the increase of their capacity can be noticed. This result is more remarkable for the second group of services where the latency requirement is less strict. Furthermore, almost all the access nodes (with the exception of two isolated rural access nodes) were assigned to the required number of UPFs according to the reliability levels established. This showcases the assertiveness of the proposed strategies for the edge infrastructure and UPFs placement. #### 5.2.2 UPFs Utilization

The load distribution was measured only in the main UPFs because the backups do not have any access node assigned in normal network conditions. For services with high requirements in urban scenarios, the four solutions provide similar levels of UPF utilization for all values of capacity, as shown in Figure 7. Moreover, the load distribution in the UPFs is quite even, being the maximum load imbalance below 25%. On the contrary, in the rural scenario (see Figure 7c) the imbalance is always above 50% and it reaches almost 100% for \(C_{u}=1\) Tb/s. Furthermore, the UPFs average utilization is quite low with values between 10% and 40%. This behaviour is caused by isolated access nodes with

Figure 5: Number of UPFs vs. capacity for services with high requirements. Figure 6: Number of UPFs vs. capacity for services with low requirements. low user density and service demands. Due to these results in the rural scenario, the capacity of the UPFs was readjusted by considering a granularity factor of 0.25 Tb/s. Figure 8 represents the total number of UPFs obtained for each value of adjusted capacity. As it can be appreciated, most of the UPFs require low values of capacity, i.e., between 0.25 and 0.5 Tb/s. Moreover, regardless of the UPFs maximum capacity increase, their adjusted capacity remains below 1.5 Tb/s most of the time. Taking into consideration these new capacity values, the UPF utilization in the rural scenario was recalculated. After readjusting the UPFs capacity, their average utilization (see Figure 9) is always above 80% while their minimum utilization is higher than 20%. Nevertheless, the load imbalance is still quite large, with values between 45% and 80%. This metric could be further improved by considering a smaller granularity factor such as 0.1 Tb/s. In Figure 10, the UPF utilization for the second group of services is shown. The four solutions provide similar results in all the scenarios with an average UPF utilization above 90%. Moreover, the load distribution in the UPFs is quite balanced with the maximum imbalance below 25%. However, most of these UPFs are overloaded with a utilization ratio above 95%. This parameter can be improved by increasing the value of the \(\alpha\) factor, but at the cost of affecting the number of UPFs. Figure 8: UPF adjusted capacities vs. maximum capacity for services with high requirements. Figure 7: UPF Utilization vs. capacity for services with high requirements. Figure 9: UPF Utilization distribution in rural scenario after adjusting their capacity. It can be observed from Figures 7 and 10 that there is no significant difference in the UPF load distribution for the placement solutions with and without mobility consideration for either OUP or NOUP. #### 5.2.3 UPFs Relocations

The UPF relocations rate was determined by considering the service data rate and the frequency of handovers between the radio access nodes (i.e., BBUs). For each use case, a probability of handover was established according to their user mobility requirements and type of region. In Figures 11 and 12, the rate of UPF relocations for services with high and low requirements are depicted.