Industrial Wireless New Choice: Bluetooth Low Energy Technology (BLE)

#Industry News ·2021-01-09 10:12:28

When you think of Bluetooth, it’s likely more about connecting headphones to smartphones, laptops, or stereo amplifiers. However, with the development of Bluetooth Low Energy (BLE), Bluetooth’s potential in industrial equipment communication is growing significantly.

Wireless communication in industry is nothing new. To date, most industrial wireless applications have involved Wi-Fi or Near Field Communication (NFC). However, interest in using Bluetooth for industrial wireless communication is increasing, with related surveys showing that about 7% of industrial companies currently report using Bluetooth.

One reason for the growing attention on Bluetooth compared to NFC is that, while both use wireless technology to exchange data, NFC devices can only connect to one other device at a time, whereas Bluetooth can support connections with up to seven devices simultaneously. Additionally, NFC uses electromagnetic wireless fields to connect devices—a potential issue in industrial environments often plagued by electromagnetic interference (EMI)—while Bluetooth uses direct radio transmission.

Mark Trautman, Strategic Account Manager at HMS, points out that the initial application of Bluetooth in industry relates to hard-to-reach sensors that are difficult or impossible to connect via direct cabling. Bluetooth’s mesh network topology is one of the main reasons for its suitability in this area. The technology also supports star topology applications. Moreover, since most people use Bluetooth daily, it is a familiar technology with significant potential in connected worker applications.

How Does Bluetooth Support Industrial Communication?

HMS Business Manager Zach Farmer notes that Bluetooth Low Energy (BLE) version 5.0 supports data transmission rates of up to 2 Mbps, while version 6.0, released in September 2024, supports up to 3 Mbps in the 2 MHz frequency band. Although the Bluetooth organization still supports classic Bluetooth technology, current research and development efforts are focused on BLE. As the name suggests, BLE consumes significantly less power compared to traditional Bluetooth.

While Bluetooth packets are not as large as those transmitted via Wi-Fi Ethernet, they do have sufficient capacity to carry most of the small-device CIP (Common Industrial Protocol) communications used by EtherNet/IP and DeviceNet.

Regarding the reliability of Bluetooth in industrial applications, Farmer mentions the technology’s frequency hopping and shifting capabilities. When one Bluetooth device attempts to establish a connection with another, they exchange information. Bluetooth devices also scan the surrounding area to understand network noise levels and avoid channels with excessive noise. If devices are initially unable to interact for some reason, Bluetooth devices hop to available channels within the frequency band to establish communication. Since the release of version 6.0, there are now three broadcast channels for BLE pairing and messaging, with the remaining 37 channels available as auxiliary broadcast channels when needed.

Bluetooth Security

Of course, security is a major concern for any wireless technology, and Bluetooth is no exception. BLE addresses this issue by sending randomized MAC addresses during the connection process. “The system uses an identity resolution key to confirm the MAC address,” Farmer explains. “Communication channels are also encrypted to prevent data sniffing. Therefore, unless you are a participant in the established connection channel, you cannot access the communication content.”

Bluetooth devices need to be in broadcast mode to be added to a network. Since devices are not always broadcasting to search for new devices to add, an explicit request is required to perform this action. This means that the devices participating in the connection are aware of each other’s identities, and there is no risk of third-party devices attempting to join and replicate the connection.

Industrial Applications of Bluetooth

Todd Wiese, System Architect and Principal Engineer at Rockwell Automation, explains: “Any sensor capable of using a broadcast access point can scan local Bluetooth devices and report the values they detect to that device.”

Devices can also use the PAWR (Periodic Advertising with Responses) feature developed in Bluetooth version 5.4. This provides the network with a time-sliced scheduling mechanism, allowing you to request a device group ID and then either implicitly request the current data value (similar to an aperiodic connection) or encode a request to a class instance property via a command, enabling the device to return data as a response to the event.

In this mechanism, the master device sends a broadcast related to the group ID identifying specific devices and generates sub-events. Sub-events include each device in the group, allowing them to respond within a specific time frame. Depending on the application’s needs, the response time can be as short as 5 or 10 milliseconds or as long as 1 second.

Wiese provides two examples, including battery-powered Power over Ethernet (PoE) devices and using smartphones to interact with devices.

For PoE devices, Bluetooth can be used to monitor their power consumption to estimate the remaining battery life. In such applications, you can “adjust the timing for querying devices based on your management approach,” Wiese says. “Of course, these communications still require a certain level of management, similar to ControlNet, where you must schedule tasks to ensure they align with the broadcast cycle intervals. But we have the capability to do that.”

Using the example of smartphones interacting with devices, Wiese explains how Bluetooth can be used to configure devices. “Here, we use the CIP application protocol on top of the encapsulation layer typically used for Ethernet. But we still use TLS to securely transmit information from the smartphone. Essentially, what we do is strip away the lower layers—the IP layer and below—and use TLS to create a secure context from the point of acquiring information to the device being communicated with. We can connect directly to the device or route the smartphone’s communication to endpoints of other devices on the Ethernet network via a gateway and establish a secure context.” This approach uses TLS to encapsulate information into a core packet and securely deliver it to individual devices.

Article reprinted from Control Engineering China.