# A Roadside and Cloud-Based Vehicular Communications Framework for the Provision of C-ITS Services
## 7 Conclusions  
Cooperative, Connected and Automated Mobility (CCAM) requires the design and implementation of reliable, scalable, and interoperable C-ITS infrastructure that combines both roadside equipment with cloud components, services, and platforms. The paper summarizes the roadside and cloud architecture devised for the deployment of C-ITS use cases under the scope of STEROID research project and the pan-European C-Roads \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Mean** & **Std. Dev.** & **Min.** & **Max.** \\ \hline OBU-RSU & 2.1 & 0.51 & 1 & 9 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: OBU (Access layer) to RSU (Access layer) delay results in milliseconds for packets with no processing associated. Figure 12: Empirical CDF representation of the OBU (Access layer) to RSU (Access layer) message delay. Sample size of 10,000 CAMs. The average values is indicated through the vertical line (2.1 ms). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Mean** & **Std. Dev.** & **Min.** & **Max.** \\ \hline ZeroMQ IPC & 0.383 & 0.054 & 0.213 & 1.579 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: ZeroMQ interprocess communication delay in milliseconds. A sample size of 10,000 requests of 500 bytes each. initiative in Portugal. This work focuses on the role of the roadside infrastructure and I2V communications in CCAM applications. An analysis using on-field performance test results of the devised architecture is provided. The obtained results prove the feasibility of the proposed architecture, showing that low end-to-end delays with small standard deviation values can be attained when the back-hauling communications between the RSUs and the cloud MQTT broker is implemented over a fiber optics connection to the Internet. On the other hand, when LTE cellular networks are employed for the exchange of data with the cloud system, higher average values are obtained, and, especially critical for real-time safety applications, large standard deviation and maximum delay values are observed. The performance of the implemented ETSI ITS-G5 protocol stack on both OBUs and RSUs devices was also evaluated by measuring the delay of a packet crossing the different layers of the communications stack. These measurements have also demonstrated the lightweightness of the developed solution. As future work, more tests with the deployed architecture will be performed, namely to study the reverse packet flow from the cloud MQTT broker to the OBU, which is an important metric considering the possibility of event dissemination by the C-ITS platform. Another important aspect to be taken into consideration is the scalability of the proposed architecture. Currently, all backhauling communications between the roadside infrastructure and the cloud C-ITS platform are centralized in a single MQTT broker. This solution performs well for a small to medium number of RSUs managed by the platform, but when many more units are deployed in the field, alternative strategies may need to be considered (e.g., hierarchical or distributed approaches, such as the introduction of Kafka clusters for enhanced message processing) to meet the pre-defined system requirements in terms of latency, availability and response time. Moreover, the impact of the security mechanism on the total delay will also be analyzed in order to understand if the use of specialized hardware for cryptographic processing could have a significant benefit. Finally, and taking advantage of the deployed cross-border corridors with Spain, interoperability tests with foreign partners will be carried out with the goal of testing standard-compliance aspects. In addition, latency measurements will also be evaluated for the OBUs crossing both countries, moving from the Portuguese PKI to the Spanish one (and vice versa) and all the related issues regarding certificate requests and ITS-S identity verification. Conceptualization, E.V., J.A., T.D. and J.F. ; methodology, E.V. and J.-A. ; software, E.V. ; validation, E.V., T.D. and A.V.S. ; formal analysis, J.A.