While most of what I talk about is 802.11 based WiFi, there are more types of wireless communications to be found in an industrial and manufacturing environment. I tend to lump them all together in casual conversation. Perhaps I shouldn’t though as there are some significant differences between them and how they work.
While WiFi makes sense on the factory floor for maintenance techs, operators, vendors, and other OT folk, it doesn’t necessarily make sense for other communication needs. Obviously I am referring to the Industrial Internet of Things. All manner of small sensors that require machine to machine (or M2M) connections using different protocols are not really a good fit for WiFi. These devices are small, many run on batteries as opposed to permanent power sources, are relatively close together, and use minimal bandwidth. Additionally, their deployment locations can be difficult to get to and can be in fairly hostile environments.
Most wireless IIoT devices do not operate based on the 802.11 standard put forth by IEEE. They are actually based on the 802.15.4 standard that IEEE created to govern wireless personal area networks, or WPANs. This standard was developed for low data rate applications and extended life / low battery usage devices. 802.15.4 defines the PHY (physical) layer including modulation, frequency, power, and some other aspects. It also defines the MAC layer format of data handling. What is interesting is that the standard then stops, using only layer 1 and 2 of the OSI model, providing the base for developers to then build upon it and create what they wish. Frequencies are restricted by this standard. I don’t want to get into number of channels and channel bandwidths but worldwide it can use the ISM 2.4GHz band, in the Americas it can also use the 902 through 928 MHz band and in Europe, the 868 to 868.6 MHz band.
6LoWPAN is an acronym for “IPv6 over Low Power Wireless Personal Area Networks”. That was a mouthful wasn’t it? As the name implies, it was created to bring IPv6 connectivity to WPANs. It operates in the 902-928 MHz frequency band and has throughput values of up to 250 kbps. Mainstream uses for this include Smart Meters, home automation (like lighting and thermostats), and small sensor networks. The differentiator here is that 6LoWPAN devices can communicate with both 802.15.4 devices and IP network devices using a bridge between them.
Bluetooth Low Energy (BLE)
Bluetooth Low Energy, also known as Bluetooth 4.0, is standard Bluetooth’s low powered brother. It is designed for greater range and low power consumption to extend battery life for sensor devices. It does this by continually remaining in a sleep mode until a connection is initiated. BLE operates in the ISM 2.4 GHz band and has an effective range of up to 150 meters. BLE can be seen in industrial monitoring sensor networks and in other M2M/IIoT applications.
LoRaWAN (or just LoRa)
Unlike the other protocols discussed here, LoRa is not based upon an IEEE standard. It is based upon the proprietary LoRaWAN Open Standard produced by the LoRa Alliance. Also, it is not a short-range communication protocol, it is designed for long range (see what they did there? Long Range = LoRa; pretty sneaky, right?) and low power. Its effective range is 15 to 20 Kilometres and it operates in the 902-928 MHz band. Frequently it is deployed with industrial and environmental monitoring sensors in large areas like tank farms.
Wireless HART, based on the tried and true industrial HART protocol, is a unique animal when compared to others on this list. First, it creates a true flat MESH topology whereas all participating devices are both a single signal source and a repeater. This provides an incredibly reliable wireless foundation for communication. Second, it coordinates communications with the wireless devices in 10 ms time frames. This results in a collision free environment that reduces the lead and lag times during which a device must be active for Tx/Rx of data. It has been said that WirelessHART can match the 5 Nines of up time service (99.999%) that wired networks lay claim to. The average device has a range of up to 225 meters, but this can obviously be extended by relaying through multiple devices. It operates in the ISM 2.4 GHz band and maintains the low data rate of 250 kbps like the other 802.15.4 based wireless protocols.
Zigbee, named after the little dance honeybees do upon returning to the hive, is similar to its competitors as it is based on 802.15.4 standards. Unlike 6LoWPAN, Zigbee cannot easily communicate with other protocols. A big benefit with Zigbee nodes is that they can stay in sleep mode most of the time thus drastically increasing device battery life. It has a maximum data rate of 250 kbps and in the U.S. operates primarily in the ISM 2.4 GHz range and the 902-928 MHz range (though not very commonly). Typical applications for Zigbee are home automation, HVAC controls, and industrial equipment monitoring.
Like Zigbee, Z-Wave is a wireless technology designed for low power consumption and low data rates (up to a whopping 100 kbps). Un-like Zigbee though, there is inter-device compatibility, meaning any Z-Wave device type from different manufacturers should be able to communicate with one another in the same fashion as 802.11 WiFi devices. Z-Wave only operates in the 902-928 MHz frequency spectrum and has a range of about 100 meters. Common applications can be home automation, automated lighting, and sensor packages.
HaLow (pronounced “halo”) took 802.11 WiFi and dropped it to the 902-928 MHz band, made it low power for slow battery consumption, and was able to keep about 1 Mbps in data rates. Not too shabby if you ask me. The interesting thing is that while ratified in 2016, no devices were created/manufactured to use it until 2018-2019. Benefits for this include multi-vendor interoperability, native IP integration, and support of the latest in WiFi security. HaLow devices are starting to be seen in industrial sensors, building automation, and agricultural IoT. (I was going to make an AIoT joke until I realized AIoT is a thing, but not for agriculture. It stands for Artificial Intelligence of Things. Sorry farmers, it looks like you don’t get your own IoT designation.)
While this is not an exhaustive list of all types of IIoT connectivity, I think that these are the major players in the game and are the ones you are most likely to see in the field. I personally haven’t worked with every one of these, but I have felt that it is important to be aware of them and of the basics on how they operate. The last thing I want to happen is to encounter one, not know what it is and then stand around scratching my head in bewilderment in front of a client. That would be bad.
Below is a quick reference sheet in PDF format of the material discussed here. Download it, share it, print it out and let your four-year-old color on it, or maybe keep it around as a tidbit of useful information.
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