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Safety-related applications are always of critical nature. Such systems are of two main types: safety monitoring and safety integration systems [45]. The former relates to quick safety reaction times to prevent physical damages to humans or materials, and the latter requires real-time communication and immediate reaction. Safety monitoring applications (e.g., gas leakage monitoring) may tolerate certain levels of delay and loss; however, safety integration systems (e.g., steam pressure control) require a communication network with very low latency, ultra-high reliability, and resiliency. Due to the impact of interference on wireless communication, safety integration systems rarely use wireless networks as their primary communication channel.

In addition, the transmission channel for safety systems must use a so-called safety protocol as the supervision mechanism [46, 47]. The protocol constantly verifies performance metrics of the transmission channel (e.g., latency, synchronicity, reliability). If the safety protocol detects any violation in its key metrics, the safety application is switched into an unsafe or fail-safe state. Considering that functional safety is a part of safety system that acts in response to risky circumstances, it exploits industrial automation and smart techniques to actively minimize system risk and failure.