# A Roadside and Cloud-Based Vehicular Communications Framework for the Provision of C-ITS Services
## 6 Results  
The latencies measured between the OBU, RSU, and cloud MQTT broker using the setup described in the previous section, are presented below. Only the packet flow latencies from the OBU to the RSU and then to the cloud broker were measured to analyze the delays between the three different entities. All results are provided in milliseconds. A PDR of 99.91% was measured for the OBU-RSU ITS-G5 connection and 100% of the messages were successfully transmitted in the RSU-Broker LTE/fiber MQTT-based communication. The fiber optics connection-based results are presented in Table 2 and Figure 10. A sample size of 10000 transmitted CAMs is represented. The results show a lower latency between RSU and broker (10.32 ms) compared to the latency between OBU and RSU (17.49 ms), but with a higher variance. It is also worth noting that the OBU-RSU connection includes more processing and analysis of the exchanged packets across the several services, in particular more computing power is required for the computation of the cryptographic procedures by the Security service. Figure 10: Empirical CDF representation of the OBU (Facilities layer) to RSU (Facilities layer) to cloud broker (listening client) message delay with the RSU with a fiber optics connection to the Internet. The vertical dashed lines represent average values. Figure 9: Setup used for performance measurements. A stationed vehicle continuously broadcasts CAMs through ITS-G5 which are then forwarded by an RSU to the cloud MQTT broker. A lightweight client in the broker server records the received messages. Overall, the time that took for a CAM to reach an application using the cloud broker since it was generated was on average 27.81 ms, with a minimum delay of 21 ms and a maximum delay of 355 ms. The LTE connection-based results are presented in Table 3 and Figure 11. A sample size of 10000 transmitted CAMs is represented. Results show a noticeable increase in the delay (76.05 ms on average) compared to the fiber optics results (10.32 ms on average). The variance of the measured delays is also much higher, with a standard deviation of 325.32 ms versus 11.45 ms and a maximum of 4574 ms versus 355 ms. Overall, the time that took for a CAM to reach the cloud MQTT broker since it was generated was on average 93.5 ms with a minimum delay of 38 ms and maximum delay of 4592 ms. Comparing to a fiber optics connection, it should be preferred over an LTE one, specially for more time sensitive applications. This is only if fiber optic connectivity to the Internet is available at the spot of the RSU installation. As expected, the type of RSU connectivity to the Internet does not affect the performance of the OBU-RSU ITS-G5 communications, as the average delay remains about the same, 17.45 and 17.49 ms. These results include the processing of the CAM packets performed by both the protocol stacks of the OBU and RSU. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Mean** & **Std. Dev.** & **Min.** & **Max.** \\ \hline OBU-RSU & 17.49 & 2.45 & 13 & 164 \\ \hline RSU-Broker & 10.32 & 11.15 & 7 & 337 \\ \hline OBU-Broker & 27.81 & 11.45 & 21 & 355 \\ \hline \end{tabular}
\end{table} 
Table 2: OBU (Facilities layer) to RSU (Facilities layer) to cloud broker (listening client) delay results in milliseconds for with the RSU with a fiber optics connection to the Internet. Figure 11: Empirical CDF representation of the OBU (Facilities layer) to RSU (Facilities layer) to cloud broker (listening client) message delay with the RSU with an LTE connection to the Internet. The vertical dashed lines represent average values. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Mean** & **Std. Dev.** & **Min.** & **Max.** \\ \hline OBU-RSU & 17.45 & 1.19 & 13 & 92 \\ \hline RSU-Broker & 76.05 & 325.32 & 21 & 4574 \\ \hline OBU-Broker & 93.50 & 325.36 & 38 & 4592 \\ \hline \end{tabular}
\end{table} 
Table 3: OBU (Facilities layer) to RSU (Facilities layer) to cloud broker (listening client) delay results in milliseconds for the RSU with an LTE connection to the Internet.