Feature: Communications
• WirelessHART: Tis IEEE 802.15.4-based protocol is a robust standard for industrial automation, supported by the HART Communications Foundation, ABB, Siemens and others. It uses a frequency-hopping mesh network with time synchronisation. By contrast, most WiFi-based communication protocols use the less-robust star network topology, where all devices connect to a central system. All communications are encrypted using 128-bit AES, and user access can be tightly controlled. Because WirelessHART uses a mesh
topology, data can be routed directly between devices, extending network range and forming redundant communication paths. So if one path fails, the sender automatically switches to another path. In addition, frequency hopping avoids interference issues. • 6LoWPAN: IPv6 over Low-Power
Wireless Personal Area Networks, known as 6LoWPAN, is a protocol that allows IPv6 packets to transmit over an IEEE 802.15.4-based network; very low power devices can connect to the Internet, well suited to IoT sensors and the like. • ZigBee: Tis standard is most
widely used in smart-home and building automation applications, and is one of the most established IEEE 802.15.4-based protocols. It allows nodes to remain in sleep mode most of the time, greatly extending battery life. It operates in the 2.4GHz band, with a fixed data transfer rate of 250kbit/s. It works with any network topology – star, tree or mesh, with tree and mesh extending its network range.
Bluetooth LE and cellular IoT Bluetooth Low Energy (BLE) is an alternative to IEEE 802.15.4, with low cost and low power being top priorities at the expense of speed and range. It operates at the same 2.4GHz frequency as standard Bluetooth, a key benefit being the native support it gets from mobile operating systems such as Android, iOS and Windows. Large electronics suppliers such as Logitech have invested greatly in R&D to make it the primary wireless-connectivity option for consumer devices. Te last few years have seen sensors,
remote controls, locks and handheld devices
www.electronicsworld.co.uk November 2022 21
use BLE for industrial automation tasks, a trend likely to increase in the future. In contrast to BLE and IEEE 802.15.4-based protocols for low-power short-range communications, cellular technologies support long-range wireless communications. 2G GSM has, however, been mostly superseded by 3G and 4G high-speed cellular protocols, commonly found in cellphones and IoT devices. The problem with these is that they require significant power, which in industrial applications (say for machine connectivity) means the system must be permanently connected to a wired power supply. Cellular LTE offers the highest data
transfer rates but at the cost of higher power consumption. LTE Cat-0 and Cat-1 connectivity are suitable for IoT devices. In contrast, LTE-M is a low-power cellular protocol designed specifically for machine- to-machine and IoT applications. In contrast with its relatively
widespread use in cellphones, industrial 5G applications are less mature, because consumers prioritise download speeds, whereas IIoT engineers prioritise low latency and ubiquitous coverage. In fact, low latency is of top importance in industrial automation. It’s true that the first 5G networks hold latency to under 30ms, with efforts to bring it down even further, to just 1ms. That’s fast enough for demanding real-time industrial control as well as monitoring, such as transmitting feedback signals in machine tools, for example.
One way that 5G reduces latency is with
network slicing, a technique that divides a network’s bandwidth into different virtual lanes that are individually managed. Some lanes are reserved for low-latency transmissions – with only industrial-control applications allowed to use them, for the quickest transmission.
LoRA Long-range wide-area network modulation (LoRA) is the low-cost wireless protocol of choice for remote and offshore applications in renewable energy, mining and logistics. Tis is a low-power wireless technology that can communicate over very long ranges on one battery – even to beyond 10km – for up to ten years. In short, LoRA is a non-cellular
technology operating in license-free frequency bands. It employs sub-GHz frequency bands, such as 433MHz and 915MHz, and spread-spectrum modulation based on chirp spread spectrum (CSS) modulation, making it well suited to IoT devices in remote locations that only need modest data transfer rates. LoRA also features 128-bit encryption and
authentication protocols. Another useful feature (especially in IIoT applications) is geolocation using trilateration (a surveying method) between devices. LoRA uses proprietary technologies
developed by Semtech, but also has a vast array of open-source elements. It’s supported (and device interoperability ensured) by the LoRa Alliance, a large association that includes IBM, Cisco, TATA, Bosch and Swisscom.
ZigBee is the most widely used in building automation applications
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