## 4 Conclusions  
Unlike a conventional network infrastructure, the possibility of achieving guaranteed high-level QoS is almost unattainable in the case of Vehicular Ad hoc Networks (VANETs). The reason is the absence of a consistent infrastructure and the environment's dynamism, which involves frequent and sudden changes in the topology. Typically, QoS routing technologies use a fixed and reliable line connection. Minimal emphasis is placed on a possible renewal. However, connections (routing paths) created in a dynamic infrastructure are influenced by speed, position, or delay. Due to the potentially high speeds achieved by vehicles, the emphasis is placed on the fastest possible way of transmitting warning messages. To achieve reliable real-time communication, the importance of high-performance routing protocols in VANETs is very high. Based on this knowledge, this study benchmarked the DSRC and LTE-based C-V2X technologies in terms of the PDR and end-to-end delay in the V2I context and urban scenarios. Regarding the LTE-based C-V2X, two technologies, i.e., LTE-Infrastructural and LTE Device-to-Device mode 3, were investigated. Using a fixed-topology transport network, we varied the traffic intensity, message generation frequency, and communication perimeter. Beyond the evident fact that the end-to-end latency tended to grow with the increase in the communication perimeter, message generation frequency, and traffic intensity, the simulation results showed major differences between the investigated technologies in terms of their sensitivity to changes in these simulation variables. Among the three investigated technologies, the DSRC performed well in the widest range of variations of the parameters. The LTE in the infrastructural mode was sensitive to increases in the message generation frequency, thus placing a higher signalization burden on the network, while the latency in LTE-D2D mode 3 grew rapidly with the increasing communication perimeter. In terms of the PDR, the DSRC yielded a stable performance with a PDR of greater than 96% under all of the conditions investigated. The LTE in the infrastructural mode achieved a PDR of between 50 and 92%, and the highest PDR values were achieved when both the communication perimeter and message generation frequency were low. Finally, the LTE-D2D in mode 3 constantly achieved a PDR \begin{table}
\begin{tabular}{c c c c} \hline \hline
**V2I Service** & **DSRC** & **LTE-Infrastructural** & **LTE-D2D** \\ \hline \multicolumn{4}{c}{**Low-frequency (1–2 Hz), low-latency (<100 milliseconds) services**} \\ \hline Slow and stationary vehicle & & \(\checkmark\) & - up to 600 m \& 1000 \\ warning & & \(\checkmark\) & vehicles per hour \\ Weather condition warnings & & \(\checkmark\) & - up to 600 m \& 1000 \\  & & \(\checkmark\) & vehicles per hour \\ Intersection management & & \(\checkmark\) & - up to 600 m \& 1000 \\  & & \(\checkmark\) & vehicles per hour \\ \hline \multicolumn{4}{c}{**Low-frequency (1–2 Hz), high-latency (<500 milliseconds) services**} \\ \hline Point of interest notification & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ Local electronic commerce & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ Media upload & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ Map updates & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ Cooperative flexible lane & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ change & & \(\checkmark\) & \(\checkmark\) - up to 600 m & 1000 \\ \hline \multicolumn{4}{c}{**High-frequency (10 Hz), low-latency (<100 milliseconds) services**} \\ \hline Electronic emergency brake & & \(\checkmark\) & \(\times\) & 1000 \\ light & & \(\times\) & 1000 \\ Emergency vehicle & & \(\checkmark\) & \(\times\) & 1000 \\ approaching & & \(\times\) & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Networking and connectivity requirements of the most popular V2I services and their fulfillment by the investigated communication technologies in the context of the selected urban scenario.