# An Improved Hybrid Routing Protocol Combining MANET and DTN
## 4 Performance Evaluation  
The performance of the proposed protocol was evaluated by extending opportunistic network environment (ONE) simulator [23], which was developed by Helsinki University to simulate DTN protocol. The performance measures used in this simulation are delivery ratio, overhead ratio, and delivery latency and they are defined as follow:  
\[Delivery\ ratio=\frac{Number\ of\ delivered\ messages}{Number\ of\ created\ messages}, \tag{4}\]  
\[Overhead\ ratio=\frac{Number\ of\ relay\ passed\ messages-Number\ of\ delivered\ messages}{Number\ of\ delivered\ messages}, \tag{5}\]  
\[Delivery\ latency=\frac{Sum\ of\ latency\ of\ delivered\ messages}{Number\ of\ delivered\ messages}, \tag{6}\]  
Parameter values assumed in the simulation are summarized in Table 1.  
Figure 5 shows delivery ratio for varying the number of nodes from 20 to 200. The performance of the proposed protocol is evaluated for different threshold values, i.e., 0, 0.1, 0.2, 0.4, and 0.8, and it was compared with that of AODV (only MANET mode), PRoPHET (only DTN mode), and HSBR. As shown in Figure 5, AODV has the largest delivery ratio when the number of nodes is large but it has the smallest delivery ratio when the number of nodes is small. On the other hand, PRoPHET has the smallest delivery ratio when the number of nodes is large and it has similar delivery ratio with proposed protocol when the number of nodes is small. The proposed protocol has better delivery ratio than other protocols when the number of nodes is not high, i.e., when the number of nodes is smaller than 120 in this simulation. The proposed protocol has similar delivery ratio with HSBR protocol and it has slightly smaller delivery ratio than AODV when the number of nodes is high. In the proposed protocol, the proposed protocol with large values of delta has better delivery ratio when the number of nodes is small but the proposed protocol with small values of delta has better delivery ratio when the number of nodes is high. This is because, more message disseminations is more favorable for message delivery and results in higher delivery ratio when the number of nodes is small but smaller message dissemination, as shown in Equation (1). On the other hand, less message disseminations is more favorable for message delivery to avoid buffer overflow when the number of nodes is high. The result shows that the proposed protocol with appropriate promotion of message dissemination performs better than other protocols. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Simulation area (m\({}^{2}\)) & 1000 \(\times\) 1000 \\ Simulation time (s) & 10,800 \\ Message generation interval (s) & U[55; 65] \\ Message size (Mbytes) & U[0.5, 1.0] \\ MANET-DTN phase switching interval (s) & 60 \\ RREQ retransmission interval (s) & 20 \\ Number of RREQ retransmission & 3 \\ Buffer size (Mbytes) & 100 \\ Movement model & Modified random direction \\ Node speed (m/s) & U[0.5, 1.0] (default value) \\ Number of nodes & 60 (default value) \\ Transmission range (m) & 100 \\ Transmission speed (Mbps) & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameter values. Figure 6 shows overhead ratio for varying the number of nodes from 20 to 200 with different threshold values, i.e., 0, 0.1, 0.2, 0.4, and 0.8. AODV has the smallest overhead ratio and then HSBBR has the second smallest overhead ratio. In the proposed protocol, the proposed protocol with large values of delta has high overhead ratio due to more message dissemination and the proposed protocol with small values of delta has small overhead ratio due to less message dissemination. Since PRoPHET has much smaller delivery ratio than the proposed protocols, the overhead ratio sharply increases when the number of nodes is high, as seen from Equation (5). The result shows that the proposed protocol has higher overhead ratio due to more message dissemination. Figure 7 shows delivery latency for varying the number of nodes from 20 to 200 with different threshold values, i.e., 0, 0.1, 0.2, 0.4, and 0.8.