# Enhanced Message Replication Technique for DTN Routing Protocols
## 4 Simulation Studies
### Metrics' Performance  
The goal of the experiments was to test the impact of the EMRT on the Spray and Wait, EBR, and DBRP quota-based protocols by comparing the results with the original versions of these protocols. This means that the performances of these protocols were not compared with one another, but rather, the performance of the protocols with and without the EMRT was compared in order to validate the effectiveness of the EMRT. Six metrics, as defined in [31], were used in the analysis.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Total Simulation Time & 12 h \\ World Size & Helsinki, Finland, 5 \(\times\) 3 km\({}^{2}\) \\ Movement Model & Map-based model \\ DTN Routing Protocol & Spray and Wait, EBR, DBRP \\  & Tram: \(U\) (7,10) \\ Speed of Nodes (m/s) & Vehicles: \(U\) (2.7: 13.9) \\  & Pedestrian: \(U\) (0.5: 1.5) \\ Buffer Size & 20 MB \\ Number of Nodes & 50, 100, 150, 200, 250 \\ Date Rate & 54 Mbps \\ Interface Transmit Range & 140 m \\ Message Time to Live & 60 min \\ Node Movement Speed & Min = 0.5 m/s Max = 1.5 m/s \\ Message Creation Rate & One message per 25–35 s \\ Message Size & 100 KB \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of the simulation work.  
Figure 1: The network’s circumstances from each node’s perspective.  
The delivery ratio is a key metric used to evaluate the performance of a network. It is calculated as the ratio of the number of delivered messages (NDB) to the number of generated messages (NGB), as shown in Equation (3):  
\[\text{Delivery ratio}=\frac{NDB}{NGB} \tag{3}\]  
The overhead is defined as the ratio of the number of delivered messages (NDB) to the number of relay nodes (NRN), as shown in Equation (4):  
\[\text{Overhead ratio}=\frac{NDB-NRN}{NDB} \tag{4}\]  
The latency average, measured in seconds, is the average time it takes for messages to be delivered to their destination in the network. Unlike other network parameters such as the delivery ratio and overhead, which are expressed as ratios and do not have units, the latency average is given by Equation (5):  
\[\text{Latency average}=\frac{\sum_{i=1}^{NDB}t_{i}}{NDB} \tag{5}\]  
In order to account for the trade-off between different metrics and penalize protocols that unfairly optimize a single metric, three composite metrics--DL, DO, and DLO--were used to compare the delivery probability and conventional metrics as ratios. These metrics, which were introduced in [30; 31], are defined as follows:  
DL is a composite metric that is used to adjust the performance of a protocol if it is optimized for delivery ratio but has poor latency. DL is a ratio of the delivery ratio (DR) to the latency average (LA), and it can be calculated using Equation (6):  
\[\text{DL}=\text{DR}\times\frac{1}{\text{LA}} \tag{6}\]  
As defined in Equation (7), DO combines the DR and the overhead ratio (OR) to capture the trade-off between these two metrics.  
\[\text{DO}=\text{DR}\times\frac{1}{\text{OR}} \tag{7}\]  
Lastly, the trade-off between DR, LA, and OR is captured by DLO, as shown in Equation (8):  
\[\text{DLO}=\text{DR}\times\frac{1}{\text{LA}}\times\frac{1}{\text{OR}} \tag{8}\]