Wireless HART - How it works

WirelessHART is a wireless mesh network communications protocol for process automation applications. It adds wireless capabilities to the HART Protocol while maintaining compatibility with existing HART devices, commands, and tools.

Each WirelessHART network includes three main elements:

• Wireless field devices connected to process or plant equipment.  This device could be a device with WirelessHART built in or an existing installed HART-enabled device with a WirelessHART adapter attached to it.
• Gateways enable communication between these devices and host applications connected to a high-speed backbone or other existing plant communications network.
• A Network Manager is responsible for configuring the network, scheduling   communications between devices, managing message routes, and monitoring network health. The Network Manager can be integrated into the gateway, host application, or process automation controller.

The network uses IEEE 802.15.4 compatible radios operating in the 2.4GHz Industrial, Scientific, and Medical radio band. The radios employ direct-sequence spread spectrum technology and channel hopping for communication security and reliability, as well as TDMA synchronized, latency-controlled communications between devices on the network. This technology has been proven in field trials and real plant installations across a broad range of process control industries.

Each device in the mesh network can serve as a router for messages from other devices. In other words, a device doesn't have to communicate directly to a gateway, but just forward its message to the next closest device. This extends the range of the network and provides redundant communication routes to increase reliability.

The Network Manager determines the redundant routes based on latency, efficiency and reliability. To ensure the redundant routes remain open and unobstructed, messages continuously alternate between the redundant paths. Consequently, like the Internet, if a message is unable to reach its destination by one path, it is automatically re-routed to follow a known-good, redundant path with no loss of data. 

The mesh design also makes adding or moving devices easy. As long as a device is within range of others in the network, it can communicate.