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:

o    Wireless field devices connected to process or plant equipment.

o   Gateways/Access Points that enable communication between these devices and host applications connected to a high-speed backbone or other existing plant communications network.

o    A Network Manager 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 Time Division Multiple Access to ensure latency-controlled communications between devices on the network.  This technology has been proven in field trials and real customer 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 efficiency and reliability.  If a message is unable to reach its destination by the usual route, it is automatically re-routed to follow the next-best 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.

For flexibility to meet different application requirements, the WirelessHART protocol supports multiple messaging modes including one-way publishing of process and control values, spontaneous notification by exception, ad-hoc request/response, and auto-segmented block transfers of large data sets. This all-digital communication method reduces overhead and therefore power usage.

For more information visit www.hartcomm.org