Wireless has become popular in the industry for measuring devices. It took a long time and a lot of talk to convince users to try it, and some companies still hesitate to jump on board, but we’ve come a long way.

Wireless communication, together with Ethernet protocols, makes data collection from smart field devices easy. It integrates the data smoothly and seamlessly into dashboards based on the Industrial Internet of Things (IIoT) and Industry 4.0 concepts.

Unfortunately, it kept one bad habit of the automation world: proprietary programming. You often can only use one from the ocean of options. So let’s review the leading wireless protocols.

WirelessHART

This protocol stands as one of the most popular in the industry. The HART Communication Foundation (HCF) developed it in 2004 and in 2007 introduced it to the market.

Emerson Automation Solutions produced the first wirelessHART device and led the field with several others. In 2010, the International Electrotechnical Commission (IEC) approved the protocol by issuing the first wireless international standard, the IEC 62591.

How does it work?

WirelessHART works in a frequency of 2.4 gigahertz. It also uses time-division multiple access (TDMA) to synchronize the devices in the network, where communication happens in 10 ms.

Image of wireless communication
Image courtesy of automationforum.in

The protocol supports channel hopping as well, to avoid interference and reduce multi-path fading. Like other protocols, wirelessHART has a design based on the Open Systems Interconnection (OSI) model.

WirelessHART layers

  • Physical layer –  IEEE.15.4. and 2.4 GHz DSSS radio
  • Media access layer (MAC) –  802.15.4-2006 MAC and MAC service
  • Data link layer (DLL) –  time-slotted channel hopping, secure acknowledgements, clock propagation, hop-by-hop data integrity
  • Network layer – end-to-end encryption and data integrity, graph and source routing, joining
  • Transport layer – reliable delivery, connectionless service
  • Application layer
    • Process control: HART 7
    • Management: diagnostics, joining centralized network configuration, etc.
    • Security: key management
    • Application sublayer:  data encoding, encryption, and integrity, command and response structure

All wirelessHART devices work as routers or repeaters, extending the network length beyond the gateway. If the network encounters a block, it automatically reroutes the data.

WirelessHART uses the mesh network concept based on the IEEE 802.15.4 standard. It combines two methods, direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS), to keep communication reliable and secure.

Main elements

  • Field devices, either native or with wireless adapters
  • Gateways to connect field devices to controller using protocols such as HART-IP, Modbus TCP/IP, or EtherNet/IP
  • Network manager for setup, routing, and monitoring, in the gateway, host, or process controller

Usually, the distance will depend on where you apply the device. Often they have a max range of 250 meters, but some offer up to 1000 in an open area.

ISA 100.11a

The committee to establish the ISA 100 formed in 2005. This committee of 400 professionals from almost 250 companies set procedures and standards for wireless systems, focusing on field devices.

In 2009, the ISA Automation Standard Compliance Institute established the Wireless Compliance Institute and officially released ISA 100.11a on September 9, 2009. Then in 2010, the protocol received the IEC 62734 standard.

How does it work?

This flexible protocol supports multiple protocols, unlike WirelessHART, which only supports HART devices. Plus, as an open protocol, it has a long list of vendors offering solutions. The network provides reliable error detection and channel-hopping, TDMA and QOS support, and high security.

ISA 100.11a layers

  • Physical layer – IEE 802.15.4 and 2.4 DSSS radio
  • Media access layer (MAC) –  modified non-compliant version of IEEE 802.15.4-2006 MAC
  • Data link layer (DLL) – joining, graph source routing, clock propagation, channel- hopping, and more
  • Network layer – IEFT IPv6 and 6LoWPAN
  • Transport layer – connectionless UDP service, end-to-end encryption, data integrity
  • Application layer:
    • Process control – no process in application layer
    • Management –  diagnostics, joining, distributed network configuration, etc.
    • Security – key management
    • Application sublayer:  data encoding, object and method services structure

ISA-100.11a allows a mesh network, but you can use other setups. The best has all devices connecting directly to the gateway or some devices on a router connected to the gateway.

In the field, you can have routing devices, I/O devices, and portable devices. For infrastructure, you have a backbone router, gateway, system manager, and security manager. Here you can see these devices in a network.

Image of wireless communication
Image courtesy of plantservices.com

Bluetooth 5.0

This new protocol has features to make it the next standard for field setup.

Twice as fast with less energy: Bluetooth 5 increases bandwidth up to two megabits per second, reducing transfer time and accelerating updates. Furthermore, it uses a minimal amount of energy.

Four times more range: The last Bluetooth offered up to 50 meters in open areas, but only 10 indoors. Bluetooth 5’s range has 40 meters indoors and up to 200 in open areas, but only by decreasing bandwidth.

Eight times more broadcasting: Bluetooth 5 works efficiently with channels in 2.4 gigahertz bands. Now you have up to 37 broadcasting channels, hence more frequency diversity.

Image of wireless communication bluetooth 5
Image courtesy of process-worldwide.com

Also, you have larger packets, from 31 to 255 octets. Marques Brownlee made a good analogy on his YouTube channel. Before, you had two hallways for data transfer. Now, Bluetooth 5 gives you 30.

Interference detection and prevention: While Bluetooth can work with other wireless devices, you always need to avoid interference. So a function called Slot Availability Mask (SAM) detects potential interference and moves away from those channels. And that means 5 can boost connectivity and avoid packet loss.

IO-Link Wireless

This network consists of a gateway with devices connected in a star topology. If you have a wired device, then the network supports a bridge to send its data wirelessly. And you’ll need a handheld or other tool to set up.

IO-Link Wireless uses three types of data. Process data exchanges up to 32 bytes every cycle. Value status data confirms the process data. And parameter and diagnostic data provide conditions, warnings, failures, and such.

The proprietary problem

Many vendors use proprietary protocols, where you can only use their products in their networks. We have companies such as Schneider and OleumTech betting on proprietary, but why should a customer use a closed protocol instead of an open one?

Can anyone tell us why these companies do this? If you’ve heard a reason, please drop it in the comments. It looks like a “captive clientele” issue to me. However, open-protocol competitors design their pitches to convince users to reject proprietary products.

For a simple process with just one device, a proprietary option may cost less than a WirelessHART or ISA 100.11a solution. Of course, that makes a strong argument for many customers. But if you want to expand, then the advantage of an open standard will make itself known.

If you want to know about such products, you can Ask Alex!

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