# Performance Analysis of Existing ITS Technologies: Evaluation and Coexistence
## 5 Adaptative Configuration  
This section addresses a significant challenge in the vehicular network: adapting the network configuration according to environment-changing situations. The idea is to provide guidelines to better support C-ITS services' diversity and their requirements. As mentioned in the previous sections, the different constraints and trade offs make it challenging to define an optimal solution with a single configuration. For example, in a real-life environment, the density of vehicles varies according to the capacity of the road infrastructure (e.g., urban, rural and highway), which allows us to predict and limit certain constraints such as density. In addition, data dissemination is ensured, on the one hand, by periodic messages between vehicles and the other entities and event messages triggered by road events. In this regard, we can differentiate two situations: The first one is periodic steady traffic configured with only one MCS coding depending on the message type (e.g., CAM or CPM). The second situation is combined traffic formed by different messages (e.g., CAM, DENM and CPM), where the optimal configuration depends on the message size. As shown in Table 5, the ideal configuration of these messages depends on the amount of data to be transmitted. In this table, the best coding to achieve the highest PRR (above 90%) has been presented. If there are multiple configurations for the same scenario, we have considered the one that provides the fastest update delay. Otherwise, we maintain them in case of performance equality. Figure 16: Coexistence LTE-V2X/ITS-G5: density sharing for packet size 1200 B. Figure 17 shows an example of mixed traffic (combined with different messages CAM, DENM and CPM), served by the ITS-G5 at several density levels. All messages are simultaneously configured by the same coding (MCS 2 or MCS 4). As shown in Figure 17, MCS 4 offers higher performance (in terms of PRR (above 90%) and range), especially in dense areas. This improvement is due to the ability of the channel configured with MCS 4 coding to absorb the combined traffic. However, as shown in Table 5, it is possible to have scenarios with simple traffic that require different configurations than MCS 4. Therefore, depending on the scenario, an optimal configuration trade off occurs when switching from combined traffic configured by this MCS 4 coding to other traffic operating with different optimal configurations. With the massive IoT deployment in road infrastructure, the amount of data exchanged between the different entities grows and changes from one location to another (e.g., urban, rural and highway). To better meet these environment-changing situations, it is necessary to adapt the configuration according to the environment's needs (density) and traffic variability. This adaptive configuration can be initiated as shown in the sequence diagram in Figure 18:  
* Either by a reconfiguration request following an event triggered by a vehicle, the request is encapsulated in a DENM message and broadcast directly to the other vehicles and the infrastructure: the RSU (road side unit) for ITS-G5 and the cellular network (C-ITS server) for LTE-V2X;
* Or by the platform road operator (Pfro) on the areas providing data perception. In this case, the request is encapsulated in a CPM message. Then, the road operator initiates  
Figure 17: Example of mixed traffic (combined with CAM, DENM, CPM) for ITS-G5. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Density** & **Packet Size 350 Bytes** & **Packet Size 800 Bytes** & **Packet Size 1200 Bytes** \\
**(Veh/km)** & **ITS-G5** & **LTE-V2X** & **ITS-G5** & **LTE-V2X** & **ITS-G5** & **LTE-V2X** \\ \hline
100 & MCS 2 & MCS 6 & MCS 2 & MCS 9 & MCS 4 & MCS 13 \\ \hline
200 & MCS 2 & MCS 9 & MCS 2, 4 & MCS 9 & MCS 4 & MCS 13 \\ \hline
300 & MCS 4 & MCS 9 & MCS 2 & MCS 9 & MCS 4 & MCS 13 \\ \hline
400 & MCS 4 & MCS 9 & MCS 2 & MCS 9 & MCS 4 & MCS 13 \\ \hline
500 & MCS 4 & MCS 9 & MCS 4 & MCS 9 & MCS 4 & MCS 13 \\ \hline \hline \end{tabular}
\end{table}