## 6 Results
### Trust Threshold-Based Selection Mode
#### 6.1.1 Results Using Trust Threshold 30%  
* Random waypoint movement model  
Figure 3 shows that the privacy enhancement rate provided by the mode on the routing is almost the same. Using a low score limit of 30% allows the routers to select a large number of next hops as a relation score with the origin. More specifically, the Prophet and Epidemic routing show the same improvement. In the Epidemic, privacy preservation has been improved by 45% with different network sizes. It means that the intermediary routers can choose the next hop with stronger ties than the normal version in the privacy-aware version of the Epidemic protocol. In Prophet, the results are the same as the experiment with the Epidemic routing. A lower restriction in the selection method leads to modest privacy enhancement. Then, \"Spray and Wait\" maintains a stable rate, while other protocols show a small degradation until reaching 10% with a larger network. The \"Spray and Wait\" protocol controls the number of allowed copies of the transmitted message. Thus, even if the threshold is low and the network becomes more crowded, the routing decision keeps a high enhancement rate for the origin sender. For network efficiency values, the packet delivery ratio (PDR) and the average transmission time (ATT) vary according to the routing scheme, while the energy consumption is not affected. The remarkable difference is due to the specification of each algorithm. Spray and Wait limits the forwarding copies and surveys the reception by destination, resulting in a better delivery ratio and longer transmission time. The Prophet protocol is an enhanced version of the Epidemic protocol. It uses its predefined probabilities to improve forwarding, providing better PDR but not reducing the transmission time. Epidemic shows a small difference in the measurement of ATT between the two routing versions. Adding the selection in the forwarding process forces the routers to apply the privacy mode and check for candidates. Therefore, the average transmission time will be greater than the time in the normal version. \begin{table}
\begin{tabular}{c c} \hline
**Simulation Parameter** & **Value** \\ \hline Simulation Time & 1 h, 10 h \\ Simulation Space & 1000 m \(\times\) 1000 m, 10,000 m \(\times\) 8000 m \\ No. of Nodes & Variable from 40 to 300 nodes \\ Interfaces & Wi-Fi + Bluetooth \\ Bluetooth Interface & 10 m with 250 k \\ Wi-Fi Interface & 1500 k, 2500 k, 4500 k, 6000 k, 6750 k \\ Node Buffer Size & 5 MB \\ Size of Message & 500 KB-1 MB \\ Message TTL & 300 min \\ Routing Protocol & Epidemic, Prophet, Spray and Wait \\ Mobility Model & Random Way, Bus, Working Day \\ \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters and values. * Bus movement model  
Figure 4 shows the results using the bus movement. It confirms the previous outcomes. In Epidemic and Prophet, the privacy improvement reaches 45% for all hops, while in Spray and Wait, it reaches 55%. The enhancement is larger for the Spray and Wait protocol than the two other protocols because Spray and Wait controls the number of allowed copies of the transmitted message (i.e., is more selective), and then even if the network becomes more crowded, the routing decision keeps a high enhancement rate for the origin sender. For network efficiency parameters, we can see Spray and Wait routing generates a better rate for PDR and even provides very low packet overhead while having the highest ATT metric values. All three protocols maintain the same energy level consumption and improvement rate for intermediary nodes. The study confirms again that the privacy enhancement depends on the threshold value without affecting the network stability. * Working day movement model  
This model emulates larger space (10,000 m, 8000 m) and longer time (10 h) than the two previous models. Figure 5 shows the result for the working day movement model. The specifications of this model, with long duration and wide space, mean that the opportunity to meet new mobile nodes is very low.