## 4 Results
### Evolution of Simulation Results with the Number of Hops  
This section presents the results obtained for the three applications: bi- and monodirectional videoconference applications (A\({}_{Vd}\)BI and A\({}_{Vd}\)MO, respectively) and a monodirectional packet stream application (A\({}_{St}\)MO). Except for jitter, the results for A\({}_{St}\)MO are not plotted as they are generally similar to those of A\({}_{Vd}\)MO in terms of trends and metric values. In this section, the results are reported as an evolution of mean and median values according to the number of hops observed between the source and destination during the exchanges. The median value informs whether the distribution of the six average values used to compute the mean value is symmetrical. The distribution is symmetric when the mean and median values are superimposed. In an asymmetrical distribution, a median value lower than the mean value means that the higher values in the distribution influence the resulting mean value. Conversely, a median value higher than the mean value means that the lower values in the distribution influence it. \begin{table}
\begin{tabular}{c c} \hline \hline Road network & 5 km straight, one-way, three lanes \\ \hline Vehicle speed distribution & 95\% of vehicle speed ranges from 80\% to 120\% \\  & of 130 km/h for cars and 110 km/h for light trucks \\ \hline Physical and MAC Layer & IEEE 802.11p \\ \hline Routing protocol & TFD-OLSR, CBL-OLSR \\ \hline \multirow{6}{*}{Application traffic type} & Bidirectional videoconference application (A\({}_{Vd}\)BI) \\  & (6000-byte frames every 0.1 s) \\ \cline{2-3}  & Monodirectional videoconference application (A\({}_{Vd}\)MO) \\  & (12,000-byte frames every 0.1 s) \\ \cline{2-3}  & Monodirectional packet stream (A\({}_{St}\)MO) \\  & (12,000-byte application packets every 0.1 s) \\ \hline Application traffic duration & 50 s \\ \hline IP Hop distance estimation & 1 to 4 hops \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Synthesis of evaluation scenarios parameters. As previously shown [14], CBL-OLSR produces less routing traffic than TFD-OLSR, even when restricted to a single traffic direction (Figure 5). Such traffic is mainly induced by HELLO and TC messages. Since HELLO messages are generated by every node,  
Figure 5: Mean routing traffic in medium (S2) and high (S3) node density scenarios. Figure 6: Mean end-to-end delay in medium (S2) and high (S3) node density scenarios. the difference comes from the TC messages that are produced by elected nodes (TFD-OLSR multipoint relays and CBL-OLSR branch nodes). By reducing the number of nodes producing TC messages, CBL-OLSR greatly lowers induced routing traffic. This reduction is even greater as the density of network nodes increases from S2 (Figure 5a,c) to S3 (Figure 5b,d). Regarding the performance of both routing protocols for application traffic, it is clear that there is almost no difference when the exchanges occur directly between a source node and a destination node when they are oen hop apart or via a single relay node when they are two hops apart. Indeed, the exchanging nodes are too close, which limits the possibility of alternative routes and probably often leads to the same or similar two-hop routes. Figures 6 and 7 describe end-to-end packet delay and packet delay variation (i.e., jitter), respectively; end-to-end packet delays for A\({}_{St}\)MO are not shown as they are similar to those for A\({}_{Vd}\)MO (Figure 6b,c). The figures show that TFD-OLSR leads to longer delays than CBL-OLSR when the exchanging nodes are three hops away and beyond. Two explanations can be proposed for these results. The first one is that the branch node selection criteria in CBL-OLSR, which take into account the relative mobility of the nodes, often lead to shorter hops and therefore better link quality between the relays and their selectors (leaf-branch and branch-branch links). Figure 8 shows the mean distance between a node and its relays.