# An Improved Opportunistic Routing Protocol Based on Context Information of Mobile Nodes
## 3 Performance Analysis  
The performance of the proposed protocol is analyzed and compared with PRoPHET protocol with GRTR strategy and RPC protocol [19], which is one of the latest protocols while using history information. For performance analysis, opportunistic network environment (ONE) simulator is used to analyze the performance, which is one of the most widely used simulators for DTN [31; 32]. The parameter values assumed in the simulation are given in Table 1.  
Figures 5-7 show delivery ratio, overhead ratio, and delivery latency of the proposed protocol, PRoPHET, and RPC, for varying the buffer size of a mobile node, where delivery predictability, overhead ratio, and delivery latency are defined as follow:  
\[\text{delivery ratio}=\frac{\text{N}_{\text{dm}}}{\text{N}_{\text{cm}}} \tag{8}\]  
\[\text{overhead ratio}=\frac{\text{N}_{\text{rm}}-\text{N}_{\text{dm}}}{\text {N}_{\text{dm}}} \tag{9}\]  
\[\text{delivery latency}=\frac{\text{SD}_{\text{dm}}}{\text{N}_{\text{dm}}} \tag{10}\]  
where N\({}_{\text{dm}}\), N\({}_{\text{cm}}\), N\({}_{\text{rm}}\), and SD\({}_{\text{dm}}\) represent the number of successfully delivered messages, the number of created messages, the number of relayed messages, and the sum of the delays of the all delivered messages, respectively. Figure 5 shows delivery ratio for varying buffer size. The delivery ratios of all three protocols increase as the buffer size increases, since more buffer size can accommodate more messages, and thus more messages can be delivered successfully without removal at the buffer. The delivery ratio saturates as the buffer size increases, since the change of buffer size does not have significant effect on the delivery. The proposed protocol has better delivery ratio than both PRoPHET and RPC for fixed buffer size, since the proposed protocol can deliver messages more efficiently. Figure 6 shows overhead ratio by varying buffer size. The overhead ratios of all three protocols decrease as buffer size increases since the delivery probability increases as buffer size increases and the effect of increased number of successfully is more dominant in the calculation of overhead as in Equation (9). The proposed protocol has the smaller overhead than both PRoPHET and RPT for fixed buffer size, since it has higher delivery probability and it efficiently limits the number of forwarding by comparing the average distance and average time as well as delivery predictability. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Area Size (m\({}^{2}\)) & 4500 \(\times\) 3400 \\ Router & PRoPHET Router \\ \hline Movement model & pedestrians, car: Shortest Path Map Based Movement \\  & tram: Map Route Movement \\ \hline Speed (m/s) & pedestrian: U[0.5, 1.5] \\  & car: U[2.7, 13.9] \\  & tram: U[7; 10] \\ \hline Number of Node & 126 (default value) \\ Simulation Time (s) & 100,000 \\ Transmission range (m) & 10 \\ Packet transmission speed & 250 Kbyte/s \\ Buffer Size (Bytes) & 10, 20, 30 (default value), 40, 50, 60, 70, 80, 90, 100 M, \\ Message interval (s) & 25–35 (default value) \\ Message size (Bytes) & U[500 k\(\sim\)1 M] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation Parameter Values. Figure 7 shows delivery latency by varying buffer size. The delivery latencies of three protocols increase as buffer size increases, since more buffer size can accommodate more messages, and thus more time is needed for forwarding to another node during short contact duration. The proposed protocol has smaller delivery latency than both PRoPHET and RPC for fixed buffer size, since the proposed protocol efficiently limits the forwarding by comparing the average distance and average time, as well as delivery predictability. Figure 5: Delivery ratio for different buffer sizes. Figure 6: Overhead ratio for different buffer sizes. Figure 7: Divery latency for different buffer sizes. Figures 8-10 show the delivery ratio, overhead ratio, and delivery latency of the proposed protocol, PRoPHET, and RPC, by varying the message generation interval.