## 4 Performance Analysis  
In this section, we analyze the performance of the proposed protocol using an opportunistic network environment (ONE) simulator developed by Helsinki University [27; 28]. Then, we compare the performance of the proposed protocol with the PRoPHET protocol with the GRTR strategy, the PRoPHET protocol with the GRTR+ strategy, the PRoPHET protocol with the GTMX strategy, and the modified HESnW [25] protocol, with a confidence interval of 95%. The modified HESnW is selected as a comparing protocol since it is one of the latest protocols using the contact history information of a mobile node. In the modified HESnW protocol, which is called HEPRoPHET hereafter, we applied the concept of multiple probability of HESnW to the forwarding decision of PRoPHET protocol. In HEPRoPHET, a message is forwarded to another node either if the node has a higher delivery predictability or if the node's multiple probability is higher than the delivery predictability of the sending node when the deliver predictability of the node has a higher than transfer threshold. The performance of the proposed protocol is compared with the PRoPHET protocol with GRTR, PRoPHET with GRTR+, PRoPHET with GTMX, and HEPRoPHET in terms of delivery ratio, overhead ratio, and delivery latency, defined as follows:  
\[\text{delivery ratio}=\frac{\text{number of delivered messages}}{\text{number of created messages}} \tag{4}\]  
\[\text{overhead ratio}=\frac{\text{number of relayed messages}-\text{number of delivered messages}}{\text{number of delivered messages}} \tag{5}\]  
\[\text{delivery latency}=\frac{\text{sum of delivered messages}^{\prime}\text{ delay}}{\text{number of delivered messages}} \tag{6}\]  
We assume the parameter values for simulation as listed in Table 1, where U[x, y] denotes a uniform distribution between x and y. We also note that we randomly generate a source node and a destination node for a message out of the total 126 nodes. Figures 7-9 show the delivery ratio, overhead ratio, overhead ratio, and delivery latency for varying the buffer size of the pedestrian and car from 10 Mbytes to 90 Mbytes, where the buffer size of the trans is 10 times that of the varying buffer size of the pedestrian and car. In Figure 7, delivery ratios of all the compared protocols increase as the value of buffer size increases, because more messages can be accommodated in the buffer and thus the dropped messages decrease. Therefore, more messages can be delivered to the destination node successfully without being dropped during delivery due to the overflow of the buffer. The proposed protocol has the highest delivery ratio for all the considered buffer sizes since the proposed protocol efficiently restricts message forwarding by considering preP and, thus, the delivery ratio is the highest. Figure 8 shows the overhead ratio for different buffer sizes. Overhead ratios of all the protocols decrease as the value of the buffer size increases since the delivery ratio increases as the buffer size increases for all the protocols and, thus, the overhead ratio decreases as can be seen in Equation (5). We note that the effect of the increased relayed messages is minor since the number of generated messages is fixed. The overhead ratio of the proposed protocol is the smallest out of all the considered protocols since the proposed protocol restricts the forwarded messages efficiently and has a smaller number of forwarded messages. It also has a higher delivery ratio.