Bluetooth® Channel Sounding enables high-precision positioning for digital keys and beyond

Imagine walking toward your car with your hands full of shopping bags, struggling to find your keys; or picture healthcare staff frantically searching for a piece of critical medical equipment in a hospital emergency; or see yourself wandering through a large shopping mall trying to locate a specific item. These everyday inconveniences highlight the need for smarter, more precise solutions.

Bluetooth® Channel Sounding strongly supports the growing demand for high-accuracy positioning. From digital car keys and personal item tracking to any application that requires precise distance measurement between two Bluetooth® devices, this technology will redefine the user experience.

As a pioneer and standard bearer of Bluetooth® technology, Silicon Labs is actively developing Bluetooth® Channel Sounding-based digital key solutions capable of achieving sub-meter level ranging accuracy. In a recent discussion, Lori Lee, senior director of APAC & China at the Bluetooth SIG, met with Anthony Zhou, China country manager at Silicon Labs, to discuss the key advantages of this solution, current market needs, and the broader potential of Bluetooth® Channel Sounding in digital key and other positioning use cases.

Q&A with Anthony Zhou from Silicon Labs

How is Silicon Labs using Bluetooth® Channel Sounding for digital key solutions, and what role will it play across the industry?

Silicon Labs is developing a digital key solution based on Bluetooth® Channel Sounding, leveraging phase-based ranging (PBR) and round-trip time (RTT) technologies to enable secure and precise distance measurement between devices. In use cases such as keyless car entry and access control, the system measures distance when an authorized device approaches. If the device is within a secure threshold, the vehicle unlocks automatically, enhancing both convenience and safety. The system can also activate specific doors, depending on proximity, by deploying multiple transmitters around the vehicle. This dual‑validation approach combines PBR and RTT to help mitigate relay attack risks and ensure secure access.

What security, accuracy, and user experience advantages does Bluetooth® Channel Sounding support?

Bluetooth® Channel Sounding uses phase-based ranging to accurately measure the distance between two devices. It also incorporates an auxiliary method called round-trip time (RTT) for distance measurement. The independent results from RTT can be used to verify and cross-check measurements obtained through phase-based ranging. This cross-verification process helps detect anomalies and enhances the overall security and reliability of the application. With this approach, Bluetooth® Channel Sounding can achieve sub-meter accuracy while significantly improving the security of distance measurement between Bluetooth® devices.

Bluetooth® Channel Sounding, when combined with multiple transmitters, can achieve sub-meter ranging accuracy. Unlike RSSI-based distance measurement, which is susceptible to environmental interference, Bluetooth Channel Sounding offers stronger resistance to interference and effectively mitigates issues caused by multipath signal reflections.

Notably, Silicon Labs has dedicated technical training and hands-on demonstrations on Bluetooth® technology at the upcoming Works With Developer Conference in Shenzhen, helping developers better understand and apply these innovations. As Bluetooth® technology is now widely integrated into smartphones, digital keys can be deployed directly onto mobile devices, eliminating the need for users to carry a separate car key. The security, precision, and improved user experience delivered by Bluetooth® Channel Sounding make digital keys more trustworthy and user friendly.

Its high accuracy ensures that digital key functionality remains stable and reliable, boosting user adoption. Furthermore, since Bluetooth® connectivity is already prevalent across a wide range of devices, digital key capabilities can be implemented without needing any additional hardware, significantly reducing deployment costs. These advantages provide strong support for widespread digital key adoption and will drive their expansion in automotive, access control, and other related fields.

What are automakers most concerned about when adopting digital key solutions?

From Silicon Labs’ perspective, automakers focus on several critical factors when evaluating digital key solutions: security, cost, performance, and user experience —each presenting unique challenges.

• Security: While Bluetooth® technology can provide secure links, the vehicle and the digital key must use highly secure Bluetooth® chips. Bluetooth® Channel Sounding enables Silicon Labs to prioritize security in our wireless SoCs, achieving PSA Level 3 and even Level 4 certifications.
• Cost: Consumers want the lowest total cost of ownership, which goes beyond just hardware BOM costs. Power efficiency is essential for longer battery life, enabling smaller batteries and reducing costs. High sensitivity also supports better signal quality and easier deployment. With Bluetooth® Channel Sounding, Silicon Labs can design new solutions with these needs in mind.
• Performance & user experience: Bluetooth® Channel Sounding enables Silicon Labs’ SoCs to support corresponding software development kits optimized for energy efficiency, making them ideal for applications that require precise location tracking and secure access control. Additionally, we provide development kits, such as Bluetooth® Channel Sounding RF boards and dual-antenna evaluation kits, to help developers build applications using the latest Bluetooth® standards quickly and easily.

With the rapid development of EVs and smart connected cars, what impact will digital keys have on the automotive ecosystem and user experience?

Amid the rapid growth of new energy vehicles and smart connected cars, the trend of digital keys becoming an industry standard is becoming increasingly clear, thanks to their ability to deliver better user experiences and enhanced security. As a key milestone in automotive technology, digital keys can deeply integrate with the vehicle’s intelligent systems as cars become more connected. This enables features such as automatic unlocking, remote control, and smart scenarios, significantly elevating both the vehicle’s intelligence and the overall user experience. Moreover, digital keys break the limitations of traditional car keys, enabling closer connections between the vehicle and its users, as well as between the vehicle and other smart devices.

Beyond automotive, how do you view the potential of Bluetooth® Channel Sounding in broader applications?

Bluetooth® Channel Sounding has significant potential in meeting the rising demand for precise tracking of assets and people across various environments. By providing real-time, highly accurate location data, it can revolutionize use cases such as asset tracking, pet tracking, and item finding.

• Consumer applications: Bluetooth® Channel Sounding enables location tracking for personal items and pets, as well as critical asset tracking in hospitals. Medical staff can more easily locate equipment like EKG machines or infusion pumps, often spread across different floors, ensuring faster response and higher efficiency.
• Industrial applications: In warehouses and construction sites, the technology enables electronic geofencing for tools and components. If an asset leaves the defined boundary, an alert is triggered — enhancing security and inventory management. In retail environments, Bluetooth® Channel Sounding, combined with electronic shelf labels, can transform indoor navigation by providing precise directions to specific products — down to the exact shelf. In transportation hubs such as airports or train stations, it simplifies navigation by offering accurate guidance to gates or platforms.

Additionally, Bluetooth® Channel Sounding can be combined with angle of arrival (AoA) and angle of departure (AoD) technologies to unlock even more innovative use cases. While AoA and AoD determine the object’s direction, Bluetooth Channel Sounding measures the distance, making this an ideal combination for smart locks and secure access systems.

To help IoT developers stay up to date on wireless technologies, Silicon Labs will host the Works With Developer Conference in Shenzhen on 23 October 2025, featuring technical training and hands-on demos focused on Bluetooth® connectivity, including Bluetooth® Channel Sounding, Bluetooth® PAwR, and Bluetooth® Mesh Networking. We warmly invite Bluetooth professionals to join us in building a smarter, more connected, and secure future.