## 5 Performance Evaluation Results and Discussion
### Reduction in Cellular Traffic Compared with the Existing Method  
Figure 17 shows the ratio of cellular traffic in the proposed method to the cellular traffic in the existing method for the pedestrian case and the vehicle case (note that the 95% confidence interval is less than 0.0031 and not visible without exaggerating the y-axis of the plots). Figure 18 shows the ratio of the number of different successful bids between the existing method and the proposed method to 1970 data requests for the pedestrian case and the vehicle case. In Figure 18, the white bars show the ratio of the number of successful bids with the evaluation score in the proposed method being higher to the 1970 data requests, and the gray bars show the ratio of the number of successful bids with the evaluation score in the existing method being higher to the 1970 data requests.  
The results in Figure 17 show that, as the number of mobile hosts increases, the relative amount of cellular traffic decreases for both the pedestrian case and the vehicle case. This trend is reasonable because the number of one-hop neighbors of a mobile host is expected to increase as the number of mobile hosts increases. From Figure 17, we confirmed that the proposed method can reduce cellular traffic compared with the existing method.  
The results in Figure 18 show that, as the number of mobile hosts increases, so does the ratio for both the pedestrian and vehicle cases. In addition, the ratio of successful bids with the evaluation score in the proposed method being higher is much larger than the ratio of successful bids with the evaluation score in the existing method being higher. The former ratio increases as the number of mobile hosts increases for both the pedestrian and vehicle cases. In contrast, the ratio of data requests with a higher evaluation score for the existing method decreases as the number of mobile hosts increases for both the pedestrian and vehicle cases.  
Figure 17: Ratio of cellular traffic in the proposed method to cellular traffic in the existing method.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline \(T_{q}\) & 12.45 s \\ \hline \(T_{L}\) & 12.95 \\ \hline \(\theta_{n}\) & 20 \\ \hline \(R_{\text{max}}\) & 150 m \\ \hline \hline \end{tabular}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline \(T^{\prime}_{q}\) & 5 s \\ \hline \(T_{s}\) & 0.5 s \\ \hline \(M\) & 2 \\ \hline \(T_{b}\) & 1 s \\ \hline \(T_{w}\) & 1.6 s \\ \hline \hline \end{tabular}
\end{table}
Table 3: Parameters used by the existing method (left) and the proposed method (left and right).  
Figure 18: Ratio of the number of different successful bids between the existing method and the proposed method to the 1970 data requests.  
The evaluation score of a successful bid in the proposed method can differ from the evaluation score of a successful bid in the existing method because the proposed method can include a mobile host in \(S_{p}(q)\) that is not included in \(S_{e}(q)\), and it can also exclude a mobile host from \(S_{p}(q)\) that is included in \(S_{e}(q)\), as explained in Section 4.3. From Figure 18, we can say that \(S_{p}(q)\) includes mobile hosts that are not in \(S_{e}(q)\) more often than \(S_{p}(q)\) excludes mobile hosts in \(S_{e}(q)\) in our simulation scenario. We also note that the ratio of the number of different successful bids is larger for the vehicle case than for the pedestrian case. We think that this result is because the faster movement of vehicle hosts causes REPs to communicate with mobile hosts that are not in \(S_{e}(q)\) and faster movement of vehicle hosts causes REPs to fail to communicate with hosts in \(S_{e}(q)\) via D2D communication more often than in the pedestrian case.