# mIoT Slice for 5G Systems: Design and Performance Evaluation
## 5 Performance Evaluations
### Simulation Results and Discussion
This is because the CP signaling for the 5 GS mIoT is mainly due in the initial phase of the traffic (establishment and updates, as seen in Figure 4), the re-setup phase involves a low CP signaling as performed on a VD-basis, i.e., the number of re-setups depends on the number of VDs and not on the number of PhDs. It is interesting to note that the reduction related to bearer signaling does not significantly vary when increasing U or T (Bearer Inactivity Timer). In particular, T does not influence the CP signaling in the considered scenario, while U has a very low impact: the case with device density of 104 UE/km2, U = 102 and U = 104 introduce a CP signaling reduction with respect to 4G of \(\sim\)49% and \(\sim\)53%, respectively. This is because, when increasing U, the number of establishment/re-setup/updates is slightly modified and, thus, the CP signaling reduction is almost unaffected. Another aspect to highlight in Figure 6 is the composition of the CP signaling for the 5 GS mIoT, which highlights how the signaling is mainly composed of bearer updates and this increases with the value of U. Focusing on the scenario with a device density of 104 UE/km2, the difference between establishment/re-setup and setup varies from one to four orders of magnitude for U = 102 to four U = 104, respectively. Considering that updates involve less load compared to establishment and re-setup, this analysis underlines how effective is the 5 GS mIoT solution in reducing the CP load in the CN, as increasing the value of U brings the benefit of reducing the number of establishments and re-setup. Figure 4: (**a**) Time variation of CP signaling in 4G; and (**b**) time variation of CP signaling with 5 GS mIoT (U = 100 and T = 1 min). The analysis considered AP = 30 min, 1 RAN node and 103 UE/km2. A further analysis of the impact of U can be seen in Figure 5, which plots the UP resource utilization for the scenario in Table 1. The higher is U, the higher is the number of PhDs re-using the same aggregate core network bearer and thus the higher is the resource utilization. It is thus clear that the size of U has a clear impact on the UP resource utilization. Although it may seem immediate that using higher U increases the benefits introduced by the 5 GS mIoT, it is worth underlining that higher U means higher number of PhDs and this might mean higher UP resource request (i.e., bandwidth) ACN bearer in case the network is required to simultaneously support the transmission by multiple PhDs of the same VD. This means that tuning U may depend on the available resources for the UP (i.e., network context): using higher U if enough UP resources are available or lower U on the contrary. High U may also introduce addressing issues as high large tag size requirements resulting in increased packet \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline RAN nodes & \(10^{4}\) \\ UE activation period (AP) & 30 min \\ UE density & \(10^{4}\) UE/km\({}^{2}\), \(10^{5}\) UE/km\({}^{2}\) \\ Maximum number of PhDs for a VD (U) & \(10^{2}\), \(10^{3}\), \(10^{4}\) \\ Bearer Inactivity Timer (T) & 1 min, 10 min, 20 min \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters for the analysis in Figures 5 and 6. Figure 5: **(a)** UP Resource Utilization with \(10^{4}\) UE/km\({}^{2}\); and **(b)** UP Resource Utilization with \(10^{5}\) UE/km\({}^{2}\). The analysis considered AP = 30 min, \(10^{4}\) RAN nodes and different values of U and T for the 5 GS mIoT. Figure 6: **(a)** CP bearer signaling with \(10^{4}\) UE/km\({}^{2}\); and **(b)** CP bearer signaling with \(10^{5}\) UE/km\({}^{2}\). The analysis considered AP = 30 min, \(10^{4}\) RAN nodes and different values of U (Maximum number of PhDs for a VD) and T (Bearer Inactivity Timer) for the 5 GS mIoT. overhead. Tuning of U, hence, should consider the above inverse performance impacts.