- March 27, 2019
By Pelle Svensson, u-blox
The numbers don‚Äôt lie: Bluetooth works, it is popular and it serves a huge ecosystem. Less well known, however, is the technology‚Äôs potential to offer wireless connectivity to industrial applications, even in the toughest environments.
By Pelle Svensson, Senior Principal Product Strategy, Product Strategy Short Range Radio, u-blox
Since it was developed in 1998 by the Bluetooth Special Interest Group (SIG), Bluetooth’s success in the consumer market – where it has become a feature in virtually every smartphone, tablet and PC – has made it a household name. According to the Bluetooth SIG, the number of Bluetooth device shipments is in the billions, growing at a 12 percent average compound annual growth rate to reach 5.2 billion units by 2022.
Less well known, however, is the technology’s potential to offer wireless connectivity to industrial applications, even in the toughest environments. The technology has reinvented itself time and again, most recently with the release of the Bluetooth 5 specifications in December 2016, augmenting its feature set and strengthening its position to serve new use cases. But what is often overlooked is that, at its very core, Bluetooth has a lot going for it when it comes to industrial applications.
Figure 1: Key features that benefit Bluetooth in harsh environments.
Here are seven strong arguments in favor of choosing Bluetooth to connect industrial applications.
#1 Bluetooth is highly immune to interference
Bluetooth operates on the unlicensed 2.4 GHz ISM (Industrial, Scientific, and Medical) frequency band. There, it coexists with a variety of other RF technologies, including Wi-Fi, ZigBee and other commercial applications, such as car alarms and video devices.
To make itself heard, Bluetooth uses a technique called adaptive frequency hopping. The 2.4 GHz ISM band is made up of 79 individual 1 MHz channels in Bluetooth Classic. In Bluetooth Low Energy (BLE) the spectrum is divided into 40 individual 2 MHz channels to allow for more relaxed RF design and further reduce cost. Messages are broken apart into small data packets and sent, one after the other, over separate channels, every 625 microseconds. The channel switches up to 1600 times per second following an agreed-upon sequence. Packets that don’t make it to the receiver intact are re-sent, and if the channel is to blame, it is flagged and avoided in further communication.
The result is wireless data transmission that reliably finds the optimal path to cut through the noise.
#2 Bluetooth supports high device density
By design, Bluetooth is highly optimized to support high device density, and multiple networks located in close proximity will continue to work with limited interference. The short data packages, ideal for industrial applications involving, for example, measurement and control, each spend only a short time in the air. Consequently, they don’t unnecessarily pollute the airwaves, minimizing interference with other devices.
Bluetooth further features automatic power control, only transmitting packets with the signal strength they need to reach the receiver device. In other words, they don’t shout when there’s no noise to cut through. This again frees airwaves, increasing the number of devices that can occupy the same frequency band without causing interference. It also has the additional benefit of saving power, which is particularly relevant for standalone, battery-operated devices.
And finally, it is optimized to coexist with Wi-Fi, which often shares the ISM band in industrial and consumer settings. Wi-Fi channels use 22 MHz bandwidth in the ISM band, which can concurrently accommodate up to three non-overlapping channels. Leveraging adaptive frequency hopping, Bluetooth is able to optimally exploit free airwaves, for example by transmitting BLE advertising data packets in the space between Wi-Fi channels.
#3 Bluetooth detects and corrects bit errors
When the signal-to-noise ratio is low, for instance in noisy environments, or when transmission distances are large, the probability of bit errors slipping into messages increases. In addition to detecting errors to optimize the channel-hopping scheme by avoiding unreliable channels, Bluetooth can, when necessary, use forward error correction (FEC) to correct bit errors on the receiver side. This involves adding redundant bits to the main message that the FEC algorithm can then use to correct errors. As we will see, this also helps Bluetooth reliably transmit messages over long distances and in noisy environments.
#4 Bluetooth fits into existing designs
Serial ports have been used for decades and continue to be relied on in industrial applications. The Bluetooth Serial Port Profile (SPP) emulates a full serial interface (RS232, RS422/485) with hardware handshaking via Bluetooth. A serial cable can be replaced by a wireless connection with point-to-point or multi-point operation. The SPP is used to exchange data between notebooks, control systems and other devices with a serial interface.
#5 Bluetooth offers more coverage than you’d think
Although Bluetooth is commonly associated with wireless communication on the order of meters, the technology has been shown to perform reliably over much greater distances. One study carried out investigations into the performance of a real-time sensor-actuator interface based on Bluetooth in harsh industrial environments.
The authors conclude that “wireless automation systems based on Bluetooth technology are extremely reliable due to their inherent system features like adaptive frequency hopping at high operating frequencies, error detection and correction. Neither parasitic machine emissions nor other radio systems or transceiver movements can impair the transmission, as long as distances are below 30 m.”
Bluetooth 5 offers an even longer range. In open-field conditions and using a good antenna, we were able to transmit a message over 1.7 kilometers using Bluetooth long-range mode (coded PHY).
Increased range is achieved in Bluetooth 5 long-range mode by increasing the duration of broadcast messages up to eight-fold in the most challenging scenarios. Coverage can be further expanded in dense environments by implementing a Bluetooth mesh network. In a mesh network, messages can be relayed from node to node until they reach their destination.
#6 Bluetooth works wherever you are
Bluetooth devices are all designed to meet the requirements of the same global standard. This plays right into the hands of device manufacturers, who do not have to worry about maintaining multiple SKUs to address a global market. The penetration of the technology into handheld devices also offers the opportunity to interact with Bluetooth devices from any smartphone or tablet via a dedicated application.
#7 Bluetooth is ideal for (Industrial) IoT applications
According to a report by Silvair, a provider of flexible lighting firmware packages for LED lighting and sensor devices, the radio performance of Bluetooth (in its low-energy variant) stands out against competing short-range wireless technologies, primarily in terms of speed, which improves efficiency, latency and responsiveness. Additionally, it is optimized for the transmission of many very small data packets, making it a perfect for IoT applications, not only in the connected home or city, but also in the connected industry.
#8 Bluetooth is highly secure by design
A number of features contribute to making Bluetooth a highly secure wireless technology. Adaptive frequency hopping, mentioned previously, depends on a pseudorandom hopping sequence known only by the transmitter and receiver. This means that an eavesdropper would have to track all available channels and correctly piece together the data packets into the message being sent.
Since Bluetooth 4.2, pairing of Bluetooth devices, a prerequisite for communication between them, uses a Federal Information Processing Standards (FIPS) compliant algorithm to generate a so-called elliptic-curve Diffie-Hellman (ECDH) public–private key pair. This feature, referred to as LE Secure Connections, prevents data being transferred from being intercepted in man-in-the-middle (MITM) attacks.
Bluetooth modules can also be made invisible to other Bluetooth devices, which means that potential hackers are unaware of their presence. Connections can only be established between devices that have been paired in advance.
Figure 2: Industrial applications of Bluetooth technology.
Reliable performance far into the future
In the 20 years since the founding of the Bluetooth SIG, the technology has been able to remain relevant by adapting to evolving use cases. Initially intended as a wireless means of synchronizing data between mobile phones, it soon served a range of use cases, typically involving data transfer between personal electronic devices. Today, BLE (starting at version 4.0) and Bluetooth 5.0 play in an entirely different league, serving use cases in the Internet of Things.
Since its inception, Bluetooth has proven itself as a robust connectivity solution for industrial manufacturing processes. Thousands of companies, in areas as diverse as industrial manufacturing, medical devices and down-well surveying, have successfully relied on Bluetooth for many years and will continue to do so into the future.
Flammini, Alessandra & Ferrari, P & Marioli, Daniele & Sisinni, Emiliano & Taroni, Andrea (2009). Wired and wireless sensor networks for industrial applications. Microelectronics Journal. 40. 1322-1336. 10.1016/j.mejo.2008.08.012.
A tale of five protocols, The ultimate guide to the IoT wireless communication landscape, February 2018.
Bluetooth Pairing Part 1: Pairing Feature Exchange, Bluetooth blog, Posted on March 29, 2016, Kai Ren.
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