Wi-Fi based Functional Safety: an Assessment of the Fail Safe over EtherCAT (FSoE) protocol

The introduction of the Industrial Internet of Things (IIoT) is dramatically changing the concept of manufacturing, ensuring better production flexibility, efficiency, safety and security. In this scenario, Functional Safety Networks are ever more deployed, being networks that allow to implement functional safety systems, integrated and cooperating with factory communication infrastructures that are ever more characterized by the deployment of wireless communication systems. Unfortunately, nowadays, the lack of safety protocols targeted for wireless networks represents a bottleneck in the novel smart factory development process. Thus, functional safety over wireless is becoming a hot research topic. In this paper, we address the adoption of Wi-Fi to implement functional safety networks by exploiting the black channel approach, which is at the basis of the most popular functional safety protocols designed for wired networks. In practice, with such an approach, the safety protocol is not aware of the underlying communication system. We focus on a specific protocol, namely FailSafe over EtherCAT (FSoE) and investigate its behavior over Wi-Fi. To this aim, we developed an experimental set-up and conducted several tests to adequately assess safety, reliability and timing performance. Specifically, we addressed the achievable Safety Integrated Level (SIL), the number of network re-initializations and the message delivery times. The analysis provided encouraging results and revealed different behaviors concerned with the use of different transport layer protocols (TCP and UDP) that suggest interesting future activities.