# Velocity-Aware Handover Self-Optimization Management for Next Generation Networks
## 4 Simulation and Performance Analysis
### Performance Evaluation  
#### 4.2.1 Fixed Values of HCPs  
The HO performance of various fixed HCPs is investigated and validated in this section. The performance represents the average values computed over all UEs in the cells throughout the simulation cycles under various UE speeds. The impact of the different fixed HOM levels on the system performance under different UE speeds are also investigated. The mobility robustness can be investigated using differentiated HOM and TTT settings for all UEs' mobile scenarios as shown Table 4. The performance of the different settings of HCPs is analyzed using two key performance indicators, namely, average HOP and average probability of HOPP.  
The effect of user mobility on the system performance is investigated. The average experienced HOP is obtained under different settings of HOM and TTT with respect to different mobile speed scenarios.  
\begin{table}
\begin{tabular}{l l l} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{3}{c}{**Value**} \\ \cline{2-3}  & **4G Macro Cell** & **5G Small Cell** \\ \hline Carrier frequency (GHz) & 2.1 & 28 [26] \\ Number of BS & 61 & 183 \\ Number of UEs/BS & 100 & 200 [7] \\ Cell radius (m) & 500 & 200 \\ Cell height (m) & 25 & 15 \\ System bandwidth (MHz) & 20 & 500 \\ Transmit power (dBm) & 46 & 30 [7] \\ Shadowing standard deviation (dB) & 8 & 10 \\ \hline Simulation area (\(\text{Km}^{2}\)) & & \(8\times 8\) \\ UE height (m) & & 1.5 \\ Mobility model & & Random direction model \\ Noise figure (dB) & & 9 \\ Thermal noise density (dBm/Hz) & & \(-174\) \\ TTT (ms) & & Adaptive \\ HOM (dB) & & Adaptive \\ HO execution time (ms) & & 50 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Simulation parameters.  
Figure 3 shows the average HOP over all mobile speeds and simulation times. In general, the reduction in the HOP leads to a significant reduction in the HOPP and the HOF. This phenomenon occurs because at low HOM levels and TTT intervals, UEs can perform early HO to the target cell. By contrast, high HOM level reduces the possibility of UE HO. The result also shows that the Set2 using a relatively high HOM and long TTT (HOM = 10, TTT = 2560) provides a significant reduction of the average HO probability compared to other settings' overall simulation time. However, the high HOP recorded in Set6 using a low value of HOM and short time of TTT (HOM = 0, TTT = 40).  
Figures 4 and 5 display the average probability of HOPP versus different mobile speed scenarios. The result shows that the highest achieved rate of HOPP is obtained by Set 6, which can be attributed to the low values of HCPs that cause the UE to bounce between the serving and target BSs. The lowest rate of the HOPP is obtained by Set 2 due to the high values of HCPs.  
The behavior of HOP and HOPP with different values of HOMs and TTTs is consistent with the effect of HOM on both parameters. At high TTT intervals, the HOP and HOPP rates decrease and reduce the signaling overhead, whereas at low intervals, both rates increase and raise the signaling overhead. The high UE speed may also cause a high RLF rate because neither the serving BS nor the target BS serves the UE.  
\begin{table}
\begin{tabular}{l c c} \hline \hline \multirow{2}{*}{**Set**} & \multicolumn{2}{c}{**HCPs**} \\ \cline{2-3}  & **HOM (dB)** & **TTT (ms)** \\ \hline Set1 & 5 & 480 \\ Set2 & 10 & 2560 \\ Set3 & 8 & 1500 \\ Set4 & 2 & 512 \\ Set5 & 10 & 320 \\ Set6 & 0 & 40 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Fixed HOM and TTT.  
Figure 3: Overall average HOP vs. HCP setting scenarios.