# Designing a Vertical Handover Algorithm for Security-Constrained Applications
## 4 Performance Evaluation and Results Discussion  
The proposed algorithm was simulated in a number of networking scenarios compared to the MIH standard. In the simulation scenario, we considered a UMTS network with 10 BSs and a Wi-Fi network with a number of APs. The important simulation parameters are given in Table 3. In a normal VHO scenario, each MU is programmed to perform a VHO from one network to another based on the RSS value. However, if an MU initiates an application that requires a secure connection, such as a banking application, the MU switches to the UMTS, which is more secure compared to a Wi-Fi network. Similarly, the UMTS provides coverage to a larger area compared to the Wi-Fi network; therefore, it reduces the frequent handovers. Further, each MU randomly opens a new application as soon as an old application is closed. Additionally, the MU is initially assigned a random number of applications at the beginning of the simulation. In the simulation, we first tested the idea of providing a secure connection to critical applications using the MIH standard. Secondly, we used the same scenario for the proposed algorithm. The results from both tests are depicted in the section. In Figure 3, the VHO delay of the proposed algorithm is compared with the MIH standard. We noticed that the MIH standard considered each application with equal priority; therefore, the VHO delay, in the case of security-constrained applications, always requires a high VHO delay compared to the proposed algorithm. In the case of a high VHO delay, there is a high possibility that the connection may drop, which will affect the overall performance of the system. On the other hand, in the case of the proposed algorithm, as soon as the MU opens a security-constrained application, the MU switches to the UMTS networks, even if the RSS threshold is not yet met. In the case of the proposed algorithm, the MU randomly opens the applications from a list of applications. In the experiments, we considered five different types of applications as follows: (1) background; (2) elastic applications; (3) video streaming; (4) audio streaming; and (5) security-constrained applications. Each application's type was assigned values from 1 to 5, which the MU used to recognize the priority of the applications. In the simulation, the MU, if using the proposed algorithm, always performs VHO if an application is selected from application type 5. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{**Simulation Parameter**} & \multicolumn{1}{c}{**Value**} \\ \hline Number of MUs & 15, 25, 50 & \\ MU movement model & Random waypoint mobility model (10 m/s) & \\ Propagation channel model & Two-ray ground & \\ UMTS network communication range & 1 km & \\ Wi-Fi network coverage & 100 m & \\ RSS threshold & \(-62\) dBm & \\ Traffic type & CBR & \\ Packet size & & 512 Bytes & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters used in the experiments. In Figure 4, we computed the total time required to complete the entire VHO process. A handover process consists of the following three phases: (1) handover initiation, which involves collecting all the required information, namely network parameters (e.g., coverage and latency), MU's preferences (e.g., security, service cost), and terminal parameters (e.g., speed and battery); (2) network selection, which involves evaluating and selecting the best available RAT according to the collected information; and (3) handover execution, which involves establishing and performing a connection to the selected RAT. To comparing the proposed algorithm with the MIH standard, we therefore computed the total VHO time to show the performance of the proposed algorithm. The total VHO time in the case of the proposed algorithm was less compared to the MIH standard because frequent handovers during the transfer of connection to the UMTS network for security-constrained applications were avoided.