# A Survey on the Application of WirelessHART for Industrial Process Monitoring and Control
## 2 Background of Process Automation
### Evolution of Wireless Networks in Process Automation  
Initially, the ZigBee wireless standard was developed to monitor and control different home automation products. Later, it was extended for specific industrial processes, but it was not suitable for regulatory and emergency classes because of its poor data reliability. ZigBee is highly suitable in monitoring and alerting systems, where energy savings is given priority [36]. The remaining communication protocols were explicitly developed for factory automation applications, where each of them was designated for various industrial application classes. WirelessHART, for example, was designed to support closed-loop supervisory and regulatory applications because of its efficient routing capabilities and high potential communication between multiple field devices to ensure multi-channel frequency hopping [37; 38]. ISA100.11a and WIA-PA are intended to provide more flexible coverage over all classes of industrial processes listed in Table 3. All these protocols use IEEE 802.15.4 as a physical standard and have a MAC layer with an equal number of channels.  
On the other hand, emergency systems require a latency of not more than 10 ms, reliable data transmission, and more parity. Thus, for these kinds of systems using a multi-hop network is not a suitable option because of network stability issues [6]. The communication standards examined here were mainly developed for monitoring and control category applications, such as open-loop and alerting systems, as shown in Table 3. The preferred standards among the existing IWSNs in industries were surveyed in 2012 and 2014; the results are summarized in Table 4[12]. The results indicated that one out of four users preferred WirelessHART, even though it faced a slight decline in the number of adopters. ISA100.11a has attracted adopters, which has resulted in a marginal growth in its implementation. The remaining wireless standards adopted among industrial users are WIA-PA, ZigBee, and Factory Automation. This gives WirelessHART a clear lead for use in the process automation industry [39; 40].  
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Category** & **Latency** & **Class** & **Description** & **End Function** & **Field Devices** \\ \hline Safety and & 10 ms & Emergency control & Always critical & Emergency shutdown & Vibration sensor Gas sensor Sprinklers \\ \hline Closed-loop & 10–100 ms & Regulatory control & Often critical & Field device control & Control valve Flow meter \\ \cline{3-6}  & & Supervisory control & Mostly non-critical & Control loops optimization & Flow meter \\ \hline Monitoring & & Open-loop control & Corrective maintenance & Manual process shutdown & \\ and Control & 100–1000 ms & Alerting systems & Preventive maintenance & Regular maintenance, Field device examinations & Proximity sensor DC motor Relays \\ \cline{3-6}  & & Monitoring systems & Periodic maintenance & Record maintenance, Event sequence recording & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Classes of industrial process automation.