# Performance Analysis of Existing ITS Technologies: Evaluation and Coexistence
## 3 Performance Evaluation and Comparision
### Performance Evaluation and Comparision
#### 3.3.1 Performance of ITS-G5 Technology  
In this subsection, the ITS-G5 is evaluated for different packet lengths to determine their performance effects and identify the most efficient configurations. The channel configurations considered are provided by MCS 0, MCS 2 and MCS 4, corresponding to a transfer rate of 3 Mbit/s, 6 Mbit/s and 12 Mbit/s. ITS-G5 adopts the carrier sense multiple access with collision avoidance (CSMA-CA) protocol at the MAC layer to manage access to the communication medium. However, the CSMA/CA protocol showed a significantly high probability of collisions. In this context, ITS-G5 addresses congestion situations through the distributed congestion control (DCC) mechanism [31] to mitigate the risk of collisions. The DCC has been introduced for channel control and adjusts traffic loads dynamically by reducing exchanged information. It operates based on a DCC management that contains all information provided by DCC access (related to channel occupancy) and the controlled parameters to adjust traffic load. The DCC can adapt the traffic load through a set of algorithms, such as transmit power control (TPC), transmit ratio control (TRC) and transmit data rate control (TDC). As a result, the DCC can better support access management in high-traffic load situations using these algorithms. In Figure 3, we present the delay between generating the message by vehicles and its effective transmission. This delay reflects the time needed to channel access and transmit the packet. As shown in Figure 3, the packet delay increases according to the packet lengths and the density, with better performances for MCS 4, which offers the highest transfer rate. Depending on the channel capacity, the ITS-G5 controls the traffic by relying on the DCC to reduce the network load. This is visible for large packets, such as 1200 bytes, since it requires more time on the channel for transmission. This reduces the number of messages sent and keeps the QoS (transfer delay) to a minimum in ultra-dense areas. Finally, the configuration with MCS 4 provides a transfer rate of 12 Mbit/s, which explains a higher traffic absorption capacity than MCS 2 and MCS 0. Once we add this duration to the update delay, we find the lifetime of the message (date age), while the update delay is the time between successively received messages. For \begin{table}
\begin{tabular}{c c} \hline \hline
**LTE-V2X Mode 4** & \\ \hline Modulation and Coding Scheme & MCS6, MCS9, MCS13 \\ \hline Keep probability & 0.8 \\ \hline Resources selection Rsel & 0.2 (20\%) \\ \hline Sensing threshold & \(-\)110 dBm \\ \hline Allocation interval [T1, T2] & T1 = 1 ms ; T2 = 100 ms \\ \hline Sensing period & 1 s \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._ITS-G5, the packet delay is practically negligible compared to the update delay. As a result, the update delay and date age are almost similar in the following simulations. In a scenario of small message exchange (corresponding to the size of CAM message), as shown in Figure 4, the MCS 4 coding provides more performance in terms of range for high densities (\(\geq\)220 veh/km), as well as a delay (UD et DA) for 95% of the received messages. This is explained by the channel's ability to handle many messages in a dense environment. On the other hand, for low densities below 220 veh/km, MCS 2 coding becomes more efficient in terms of range (it can reach 200m with a PRR above 90%) and provides similar performance to MCS 4 coding in terms of delay. Figure 4: Evaluation for ITS-G5 technology (packet size 350 bytes). Figure 3: ITS-G5 packet delay for 100% of the generated packet. In Figure 5, the message size has increased to 800 bytes (corresponding to the amount of data carried by a DENM message). Therefore, the configuration with MCS 2 coding has the highest range for almost all scenarios with different densities. On the other hand, the channel capacity with MCS 4 keeps the best performance in terms of delay, especially for densities above 100 veh/km.