WirelessHART

What is WirelessHART?

WirelessHART is a wireless communication protocol for process instrumentation that carries the commands and data of the wired HART protocol over a self-healing IEEE 802.15.4 mesh network in the 2.4 GHz band, and is standardised internationally as IEC 62591. It connects sensors and actuators to a DCS, SCADA system or maintenance application without signal cabling, with mandatory encryption and several redundant radio paths. WirelessHART is part of HART 7 and is maintained by the FieldComm Group. It is mainly used to extend existing plants where running cable is expensive, slow or impractical, such as in large or hazardous industrial environments.

🕰️ How did WirelessHART come about?

In 2004, members of what was then the HART Communication Foundation, including ABB, Emerson, Endress+Hauser, Pepperl+Fuchs and Siemens, started work on a wireless extension of HART. The radio technology came from Dust Networks, whose Time Synchronized Mesh Protocol (TSMP) already provided a low-power, time-synchronised mesh network.

The official title of the standard is Industrial networks – Wireless communication network and communication profiles – WirelessHART. Because the application layer is the same as wired HART, existing host systems and configuration tools can address wireless devices in the same way.

🧠 How does WirelessHART work?

WirelessHART combines four techniques that together provide reliability:

• IEEE 802.15.4 radio - 2.4 GHz ISM band at 250 kbit/s, the same physical layer as Zigbee and ISA100.11a
• Time slots (TDMA) - every second is divided into one hundred 10 ms slots; each device transmits only in the slots assigned to it, so there are no collisions and the radio sleeps the rest of the time
• Frequency hopping - the network hops to a different channel every slot, across 15 of the 16 available channels, and can blacklist busy channels, for example where they overlap with Wi-Fi
• Mesh with graph routing - every field device also acts as a router; the network manager calculates several routes in advance, so the network switches over by itself when a path fails

Which components make up a WirelessHART network?

🔐 How is WirelessHART secured?

Security is not optional in WirelessHART. Every message is protected with AES-128 in CCM mode, at two levels:

• Per hop (data link layer) - each radio packet carries a message integrity code based on the network key, so every forwarding device rejects forged or altered packets
• End to end (network layer) - the payload is encrypted with session keys for each communication pair, for example field device ↔ gateway, so intermediate devices forward the data but cannot read it
• Join key - a new device can only join with the correct join key; it cannot be read back through HART commands and can be unique per device
• Quarantine and rejection - the gateway can hold back an unknown device until an administrator has checked its manufacturer, type and tag
• Failed attempts - devices count messages with an invalid key and report them to the gateway, which enables monitoring

This encryption and authentication protect the radio part well. The weak spot usually lies elsewhere: the gateway with its web interface, shared join keys and the wired link to the DCS. A radio link also remains vulnerable to jamming; frequency hopping makes the network robust against accidental interference, but not against a deliberate jammer.

🏭 What is WirelessHART used for?

WirelessHART is mainly deployed in oil and gas, chemicals, pharmaceuticals and water and wastewater. Typical applications are:

• Additional measurement points - temperature, pressure, level and flow where no cable or spare I/O is available
• Condition monitoring - vibration of pumps and fans, bearing temperatures, steam traps and valves, as the basis for predictive maintenance
• Unlocking diagnostics - with an adapter, field devices that already run on 4-20 mA can be read wirelessly for diagnostic data, without changing the existing control loop
• Temporary measurements - during start-up, investigations or a turnaround
• Hard-to-reach locations - tank farms, rotating equipment and remote parts of a site

WirelessHART is primarily a monitoring network. Slow control loops are possible, but wired instrumentation remains the norm for fast control and for safety functions in a SIS. WirelessHART gateways are also named as a source for the second channel of NAMUR Open Architecture, which makes process data available for analytics outside the DCS.

🧭 How do you design a WirelessHART network?

Good design prevents most problems. The following steps and rules of thumb are widely used in practice:

1. List the measurement points - determine the required update rate for each point and whether it is for monitoring or control
2. Choose the gateway location - central in small networks; build larger networks outwards from the gateway, starting with the nearest devices
3. Provide enough neighbours - aim for at least three neighbours per device, so there is always an alternative route (redundancy)
4. Mind the obstacles - steel, tanks and concrete walls attenuate the signal strongly; mount antennas vertically and above obstructions
5. Spread the load - many devices with fast updates load the gateway; split them across several networks if needed
6. Document and check - record join keys, tags and network IDs in your asset inventory and check path stability after commissioning

In hazardous areas, both the instrument and the power module must be suitable for the zone under ATEX; many wireless transmitters are built to an intrinsically safe design. Under the Dutch Cybersecurity Act, in force since 15 August 2026, a wireless measurement network at an essential or important entity simply falls under the duty of care: include it in your risk assessment.

🛡️ How does WirelessHART fit into an IEC 62443 architecture?

In IEC 62443 terms, you treat the wireless network together with its gateway as a zone of its own. The link to the DCS or historian is a conduit, with a firewall that only allows the required protocols and directions (network segmentation). Practical measures:

• Use unique join keys per device instead of one shared key, and store them securely
• Enable the gateway’s access control list, so only known devices can join
• Disable unused services on the gateway and change default passwords
• Allow management traffic to the gateway only from a management zone
• Monitor the gateway logs for failed joins and unexpected rogue devices

🔄 How does WirelessHART differ from other wireless protocols?

The main alternative for wireless process instrumentation is ISA100.11a (IEC 62734), supplied mainly by Yokogawa and Honeywell. WirelessHART is used by vendors including Emerson, ABB, Endress+Hauser and Siemens.

❓ Frequently asked questions

Is WirelessHART an open standard?

Yes, WirelessHART is an open standard maintained by the FieldComm Group and published as IEC 62591. Devices from different manufacturers work together in the same network when they are registered under the FieldComm Group test programme.

Can WirelessHART be used for process control?

WirelessHART can support slow control loops, but in practice it is mainly used for monitoring and condition monitoring. For fast control loops and safety functions in an SIS, most companies still choose wired instrumentation.

How long does the battery of a WirelessHART device last?

The battery life of a WirelessHART device depends mainly on its update rate and on how many messages it forwards for other devices. Manufacturers quote up to about 10 years at an update rate of around one minute; with updates every second it is considerably shorter.

How secure is WirelessHART?

WirelessHART uses mandatory AES-128 encryption, per-hop integrity checks and keys per communication pair, which protects the radio part well. The biggest risks lie in shared join keys, a poorly secured gateway and interference from a deliberate jammer.

What is the difference between HART and WirelessHART?

HART communicates over the wired 4-20 mA loop, while WirelessHART sends the same HART commands wirelessly over an IEEE 802.15.4 mesh network. As a result, existing HART tools and host systems can configure and read wireless devices in the same way.

Does WirelessHART coexist with Wi-Fi?

WirelessHART and Wi-Fi both use the 2.4 GHz band, but they can operate side by side. WirelessHART hops between channels and can exclude busy ones; coordinating the Wi-Fi channels on site helps to limit interference.

📌 In summary

WirelessHART is the wireless variant of the HART protocol, standardised in IEC 62591, that connects process instruments to the control system through an encrypted, self-healing mesh network.

The protocol is reliable thanks to 10 ms time slots, frequency hopping and multiple routes per device, and secure thanks to mandatory AES-128 encryption with join, network and session keys. It is particularly suited to additional measurement points, condition monitoring and unlocking diagnostics in existing brownfield plants. Treat the gateway as a separate zone in your OT network and manage join keys as carefully as passwords.