How will Bluetooth® Channel Sounding Shape the Future of Device Positioning?

In September 2024, the Bluetooth SIG released Bluetooth® Core Specification Version 6.0, bringing several enhancements to the technology. Chief among these is the long-awaited arrival of Bluetooth® Channel Sounding, previously known as High Accuracy Distance Measurement (HADM). This represents the latest step in the evolution of Bluetooth® Low Energy’s (LE) positioning capabilities through the introduction of a new, secure, and fine-ranging ability, providing centimeter-level distance measurement between two Bluetooth® LE devices, a significant improvement over previous Received Signal Strength Indicator (RSSI) techniques.

Bluetooth® LE’s suite of positioning features has evolved considerably since it was first introduced in 2010, encompassing a combination of presence, directional, and distance measurement techniques. RSSI-based beacons and asset tracking devices enabled many Bluetooth® LE positioning use cases such as Find My item trackers, proximity marketing, indoor navigation, digital keys, and asset tracking, with accuracy typically in the 3-Meter (m) to 5-m range. In 2019, Bluetooth® Core Specification Version 5.1 introduced support for Direction Finding, enabled by Angle of Arrival (AoA) and Angle of Departure (AoD) positioning techniques to provide much higher accuracy location services compared to RSSI methods. These significantly enhanced Real-Time Location System (RTLS) and asset tracking accuracy to the sub-meter level, while also bringing significant improvements for indoor navigation systems within transportation hubs, hospitals, education campuses, stadiums, and other public venues.

The arrival of Bluetooth® Channel Sounding relies on a new protocol stack, including a new PHY layer that standardizes the techniques used to gather the signal phase and time delay information. This enhanced security and accuracy is achieved through two major positioning techniques known as Phase-Based Ranging (PBR) and Round-Trip Time (RTT). PBR enhances the accuracy, while RTT acts as an independent distance measurement technique that can help to counter potential man-in-the middle relay attacks when using PBR alone. PBR and RTT can be used independently, but combining them can significantly improve the security and accuracy of the solution, vital for secure access control applications. These bring a number of benefits, including centimeter-level accuracy, higher security, interoperability, reduced cost and complexity, and reduced power consumption.

While we are still in the early stages of adoption for Bluetooth® Channel Sounding, the unique presence of Bluetooth® technology in platform devices and connected devices has the potential to significantly expand the current market presence of distance awareness solutions. This includes more accurate Bluetooth® Find My solutions, secure digital key, and automotive access control solutions, as well as a whole range of new potential opportunities such as enhanced asset tracking, human interface devices that can switch between active and inactive states depending on proximity, proximity-based interactions such as device unlocking, geofencing-based home and building automation, and safer industrial Human Machine Interfaces (HMIs) that can only be used when at a certain distance from the equipment it is controlling.

There are several wireless technologies on the market, most notably Ultra-Wideband (UWB), Wi-Fi, and Bluetooth® LE, that can provide distance measurement capabilities. Each has its own unique benefits and trade-offs in terms of accuracy, power consumption, latency, range, scalability, ease of deployment, ecosystem enablement, and cost, among many others. However, one key advantage for Bluetooth® is that with the arrival of Bluetooth® Channel Sounding, almost any Bluetooth® LE-enabled device with a compatible chipset can be tracked more accurately without the need to embed a separate tag. For example, Bluetooth® LE-enabled remote controls, audio devices, connected toys, and games console controllers could all provide enhanced location awareness without the need for additional dedicated hardware. As more and more Bluetooth® platform devices integrate “Find My” capabilities, the rollout of Bluetooth® Channel Sounding-enabled connected devices can significantly expand the scale and accuracy of “Find My” and “Find My Device” networks, enabling a huge network of Bluetooth® “Find My” devices for more readily locating lost devices.

While alternative technologies such as UWB can provide higher accuracy and lower latency, for many applications, the centimeter-level accuracy, ubiquitous availability of Bluetooth® smartphones and platform devices, lower chipset costs, lower power consumption, reduced design complexity, and the avoidance of an additional radio could prove compelling enough to leverage standalone Bluetooth® Channel Sounding as an alternative to UWB fine-ranging across many distance measurements use cases. For example, if we take the personal tracker use case, there may be little benefit in knowing whether an item is 10 Centimeters (cm) away versus 30 cm, or even 1 m away depending on the size of the item. On the other hand, there may be a better user experience provided by UWB due to the ability to combine ranging with directional capabilities.

To achieve success, the Bluetooth® ecosystem will need to ensure swift adoption of compatible hardware, create tailored solutions for different use cases and form factors, and work with industry consortia such as the Car Connectivity Consortium (CCC) and the Connectivity Standards Alliance’s (CSA) Aliro to promote Bluetooth® Channel Sounding as another viable technology. The ecosystem will also need to educate the industry on the benefits of Bluetooth® Channel Sounding, take advantage of the ubiquitous Bluetooth® ecosystem, and look at ways in which Bluetooth® Channel Sounding can also work together with additional technologies, whether RSSI, Direction Finding, Wi-Fi, or UWB, to enable even more unique location services that can maximize performance, while reducing power consumption and deployment complexity.

Ultimately, Bluetooth® Channel Sounding is well positioned to provide a broader rollout of secure distance measurement solutions. Embedding this feature into the Bluetooth® core specification has the potential to scale rapidly and significantly enhance the availability of accurate, low-power, secure, and fine-ranging across a wide range of device types. This, in turn, will enable creating innovative location-based experiences such as accurate asset tracking, secure access control, and other innovative device-to-device interactions in the years to come. More information on Bluetooth® Channel Sounding can be found in ABI Research’s How Bluetooth® Channel Sounding Will Shape the Future of Device Positioning market research note.