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to monitor conditions while the equipment is in service is not possible with wires, but the knowledge gained from in-service monitoring can allow customers to predictively maintain this critical equipment, thereby avoiding unwanted and expensive downtime. To ensure flexible and cost-effective deployments, every node in an industrial WSN should be capable of running on batteries for at least five years, as this offers users the ultimate flexibility in coverage for IIoT applications. As an example of an industrial TSCH-based WSN, Analog Devices' SmartMesh products typically operate at well under 50µA, making it very feasible to operate for many years on 2AA batteries. In environments where there is a good source of harvested energy, it is possible to run nodes perpetually on energy harvesting (Figure 1). Time Matters Industrial monitoring and control networks are business critical. They underpin the systems that affect the basic cost of producing goods, and the timeliness of data is essential. In the past decade, deterministic TSCH-based WSN systems have been field proven in a wide range of monitoring and control applications. These time-slotted systems, such as WirelessHART, provide time-stamped, time-bounded data transmission. In these networks, nodes that require more opportunities to send data are automatically provisioned with more time slots, and low latency transmission through the network can be achieved through the provision of multiple time slots on successive paths in the network. This coordination of data transmission also dramatically improves the ability to deploy dense networks with frequent transmissions. Without a time schedule, non-TSCH wireless networks will collapse from the uncoordinated flood of radio traffic. Additionally, every packet in a TSCH network contains an accurate time stamp indicating the time it was sent, and network-wide time is also available at each node to coordinate control signals across a network of WSN nodes if required. The availability of time-stamped data enables data to be properly sequenced by the application even if it is received out of order, which can be helpful in diagnosing precise cause and effect in industrial applications where information from multiple sensors must be reconciled. Visibility to Network Operation Is Key Industrial networks are required to run continuously for many years, yet no matter how robust a network is, problems can still occur. The quality of a network that works well at installation may be affected by a variety of environmental factors during its operating life. Early and appropriate alerts to such issues are an important aspect of any industrial network, and the ability to quickly diagnose and remedy issues is key for quality of service. Not all wireless sensor networks are created equal when it comes to providing visibility to network management metrics. At a minimum, an industrial wireless network management system should provide visibility to: • Wireless link quality, measured in signal strength (RSSI). • End-to-end packet success rate. • Mesh quality, highlighting nodes that do not have sufficient alternate routes to maintain a reliable network. • Node status and battery life (where applicable). In the best industrial implementations, intelligent networks will remediate such issues by automatically rerouting data on alternate paths, while continuously upgrading the network topology to maximize connectivity (Figure 2). 26 Figure 1: Sensors Anywhere—Low Power Wireless Sensor Nodes Powered Perpetually by Harvested Energy, Such as This Thermal- Harvested Wireless Temperature Sensor from ABB, Can Be Placed Optimally to Gain Additional Data in an Industrial Setting Figure 2: Network Visibility—Network Management Software Provides Critical Visibility to the Health of the Wireless Network Such as in This SNAP-ON Software Utility from Emerson Process Management IoT

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