What is IO-Link Wireless?
IO-Link Wireless is the wireless extension of IO-Link (IEC 61131-9), defined in IEC 61139-3, that lets sensors and actuators exchange process data, parameters and diagnostics with a wireless master over a 2.4 GHz radio link with a guaranteed 5 ms cycle time. The data model and way of working stay the same as wired IO-Link; only the physical layer is replaced by radio. Towards the PLC, the wireless master (W-Master) behaves like an ordinary IO-Link master. This brings the last metre of the IO wireless to places where a cable wears out, breaks or simply does not fit.
🧠 What problem does IO-Link Wireless solve?
Wired IO-Link uses an unshielded 3- or 5-core cable of up to 20 metres. That is cheap and robust as long as the sensor stays still. On moving parts, problems appear:
- Cable breaks and wear - cables in drag chains, on rotary tables or on robot arms wear out and are a well-known cause of unplanned downtime.
- Slip rings and connectors - rotary tables need slip rings, which require maintenance and are prone to faults.
- Tool changers - grippers and tools on a tool changer have connectors that take mechanical stress at every change.
- Retrofit - in existing machines (brownfield), pulling extra cables is expensive and often impossible without dismantling.
General-purpose wireless technologies such as Wi-Fi, Bluetooth and Zigbee do not solve this for factory automation: they were not designed for a fixed, short cycle time and, in an industrial environment, lose far more packets. IO-Link Wireless was therefore designed specifically for deterministic real-time communication on the shop floor.
🔧 How does IO-Link Wireless work technically?
IO-Link Wireless uses a single-hop star topology: every wireless device (W-Device) talks directly to the W-Master, with no mesh or relay stations. The key mechanisms are:
- Tracks via FDMA - a W-Master has up to five radio channels (tracks) that operate simultaneously on different frequencies.
- Time slots via TDMA - within a track, each device gets its own time slot. The master is the clock source and the devices synchronise to it, so there are no collisions.
- Three attempts per cycle - a 5 ms cycle is divided into three sub-cycles of roughly 1.66 ms. The first carries the normal exchange; the second and third are retries for packets that did not arrive.
- Frequency hopping - the radio hops to a different frequency every sub-cycle following a pseudo-random pattern, using 1 MHz channels and GFSK modulation.
- Adaptive blocklisting - the master scans the spectrum and removes channels used by other systems (Wi-Fi, for example) from its hopping table. This lets IO-Link Wireless coexist with existing networks.
The physical layer is based on that of Bluetooth Low Energy 4.2 (GFSK, 1 MHz channels), but the access method and the protocol on top of it are entirely its own; a W-Device is therefore not a Bluetooth device and does not talk to a smartphone.
| Feature | Typical value |
|---|---|
| Standard | IEC 61139-3:2023 (extension of IEC 61131-9) |
| Frequency band | 2.4 GHz ISM band, 1 MHz channels |
| Topology | Star, single hop, no mesh |
| Cycle time | 5 ms guaranteed for process data |
| Process data | Up to 32 bytes per device per cycle |
| Devices per W-Master | Up to 40 (5 tracks × 8 devices) |
| W-Masters per cell | Up to 3 side by side, 120 devices in total |
| Packet error rate | Below 10⁻⁹ (IO-Link community figure) |
| Range | About 10 metres, depending on environment and antenna |
| Roaming | Supported: a device can move to another master |
The packet error rate of less than one in a billion is compared with roughly 10⁻³ for Wi-Fi, Bluetooth and Zigbee under industrial conditions. These figures come from the IO-Link community itself; in practice, latency and reliability depend on the radio environment.
📚 How is IO-Link Wireless standardised?
The specification was completed in 2018 by the IO-Link community, which operates under the umbrella of PROFIBUS & PROFINET International. That specification, IO-Link Wireless System Extensions, has been updated since; version 1.1.3 belongs to the 2024 specification package, and a newer version is under review.
In November 2023, the IEC published the international standard IEC 61139-3:2023 (Industrial networks - Single-drop digital communication interface - Part 3: Wireless extensions). It describes the physical layer, data link layer and application layer for W-Masters and W-Devices. Integration with a fieldbus is deliberately out of scope: as with wired IO-Link, that remains the job of the master. The standard has also been adopted as a European standard (EN IEC 61139-3:2023).
🔄 How does it differ from IO-Link and other wireless protocols?
| Feature | IO-Link Wireless | IO-Link (wired) | WirelessHART |
|---|---|---|---|
| Medium | Radio, 2.4 GHz | Cable, max. 20 m | Radio, 2.4 GHz |
| Topology | Star, single hop | Point-to-point | Mesh |
| Cycle time | 5 ms | From about 0.4 ms (COM3) | Usually seconds |
| Target domain | Factory automation | Factory and process automation | Process automation |
| Moving parts | Very well suited | Cable wear | Limited |
| Standard | IEC 61139-3 | IEC 61131-9 | IEC 62591 |
WirelessHART and ISA100.11a are intended for process instruments that send a measurement once per second or less often over longer distances. IO-Link Wireless targets discrete sensors and actuators inside a machine, where milliseconds count. Compared with 5G, IO-Link Wireless is much simpler: no operator and no network infrastructure, just a local cell around one machine.
🏭 Where is IO-Link Wireless used?
- Rotary and indexing tables - sensors on the rotating part without a slip ring.
- Robot grippers and tool changers - a cobot or robot changes gripper, and the wireless device immediately reconnects to the master.
- Mobile platforms - AGVs, AMRs and shuttles that operate sensors or actuators at a station; roaming lets a device move from one master to another.
- Retrofit - a wireless bridge makes a wired IO-Link device wireless without new cable trays.
- Hard-to-reach zones - guarded machine sections, ovens with moving parts, or places where cleaning damages cables.
Typical sectors are assembly lines, packaging machines and intralogistics, for example conveyors and shuttle systems. Because parameters and diagnostics travel along with the process data, IO-Link Wireless fits well with condition monitoring and predictive maintenance as part of Industry 4.0.
🛠️ How do you approach an IO-Link Wireless project?
- Map the moving points - where do cable breaks, slip-ring maintenance or connector faults occur today? Those are the candidates with the fastest payback.
- Run a spectrum scan - measure which 2.4 GHz systems (Wi-Fi, Bluetooth, wireless handheld scanners) are active, and allow for metal shielding.
- Choose master and uplink - pick a W-Master with the right uplink to the PLC, for example ProfiNET or IP, and plan the tracks: at most eight devices per track.
- Pair the devices - W-Devices are bound to a master (pairing), for example by their unique device ID. Record that pairing in the machine documentation.
- Test under production conditions - check error statistics and retries while the machine is running, not only when it is idle.
- Handle safety separately - IO-Link Wireless is not a safety protocol. Emergency stops and guards remain within functional safety and are implemented with a certified solution.
In the Netherlands and the wider EU, radio equipment falls under the Radio Equipment Directive (RED, 2014/53/EU). Since 1 August 2025, cybersecurity requirements apply to radio equipment that can communicate over the internet itself, which mainly affects masters with a network connection. New products with digital elements also fall under the Cyber Resilience Act: reporting obligations from 11 September 2026 and full application from 11 December 2027.
🔐 How do you secure IO-Link Wireless?
Frequency hopping, blocklisting and retries make the link robust against interference, but that is not the same as cybersecurity. A deliberate jammer can disrupt the entire 2.4 GHz band, and radio signals do not stop at the wall.
- Ask about security features - do not assume the radio link is encrypted. Ask the supplier which encryption and pairing authentication the W-Master and W-Devices support.
- Restrict pairing - allow pairing only during commissioning, and control who may do so through access control on the engineering tools.
- Segment the master - place the W-Master in the machine segment of the OT network and apply network segmentation in line with the Purdue Model; broader segmentation limits the impact of a compromised device.
- Design for loss of link - the machine must stop safely if the wireless link drops out; that belongs in the control architecture.
Security for IO-Link Wireless is therefore mostly a matter of the surrounding network and procedures, not of the radio protocol alone.
❓ Frequently asked questions
How fast is IO-Link Wireless?
IO-Link Wireless guarantees a 5 ms cycle time for process data, including two retry attempts per cycle. That is slower than wired IO-Link, which works from about 0.4 ms, but more than enough for most discrete sensors and actuators. IO-Link Wireless is not intended for fast motion control.
How many devices can an IO-Link Wireless master handle?
An IO-Link Wireless master has up to five tracks with at most eight devices each, so up to 40 devices per master. Up to three masters can operate side by side in the same cell, giving 120 wireless devices in total.
Does IO-Link Wireless interfere with Wi-Fi?
IO-Link Wireless uses the same 2.4 GHz band as Wi-Fi, but it constantly hops between frequencies and removes occupied channels from its hopping table. This allows IO-Link Wireless to coexist with Wi-Fi and Bluetooth. A spectrum scan beforehand is still wise, because a heavily loaded band reduces the margin.
What is the range of IO-Link Wireless?
The range of IO-Link Wireless is about 10 metres, which suits a cell around a single machine or production line. Metal shielding and antenna position determine the actual range. For longer distances in the process industry, mesh protocols such as WirelessHART are the intended choice.
Is IO-Link Wireless an international standard?
Yes, IO-Link Wireless has been defined in IEC 61139-3 since November 2023, as an extension of the IO-Link standard IEC 61131-9. The underlying specification from the IO-Link community has existed since 2018.
Can I use IO-Link Wireless for an emergency stop?
No, IO-Link Wireless is not a safety protocol and is not intended for emergency stops or other safety functions. Those require certified solutions that meet functional safety requirements. IO-Link Wireless can, however, supply diagnostic and status information alongside such a safety system.
📌 In summary
IO-Link Wireless (IEC 61139-3) brings the IO-Link data model wirelessly to moving and hard-to-cable sensors and actuators, with a guaranteed 5 ms cycle time and up to 40 devices per master.
The protocol combines tracks, time slots, frequency hopping and retries into a deterministic radio link for industrial automation. It replaces cables on robot grippers, rotary tables and mobile platforms, but not safety engineering and not the basic rules of OT security.