Bluetooth® Channel Sounding: High-precision distance measurement and its implementation
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Bluetooth® Channel Sounding is a high-precision distance recognition feature adopted in Bluetooth® Core 6.0. This new feature has received significant attention across various industries as it achieves greater accuracy and security while keeping implementation costs low by leveraging the widely adopted Bluetooth ecosystem for location-based services applications.
Silicon Labs, playing a major role in IoT wireless connectivity, has contributed to the development of Bluetooth® Channel Sounding from the forefront of product development. At Bluetooth Tokyo Seminar 2024, Mr. Yasuaki Okada, senior FAE at Silicon Labs’ Japan office, presented on how to implement Bluetooth® Channel Sounding to achieve better accuracy. This article showcases a few of the highlights featured in Mr. Okada’s presentation.
A notable advantage is that relatively high-precision ranging is possible with just one antenna. However…Bluetooth® Channel Sounding supports up to four antenna paths and includes multiple security features as standard
Yasuaki Okada, Silicon Labs
Bluetooth® Channel Sounding: High-precision distance recognition
Bluetooth® Channel Sounding uses PBR (phase-based ranging) and RTT (round-trip time) and operates in the same 2.4GHz frequency band as Bluetooth Low Energy (LE). While still utilizing random hopping patterns for channel occupation, channel sounding uses 1MHz width per channel with 79 total channels (72 available for ranging after excluding advertising channels), compared to Bluetooth LE’s 2MHz width per channel with 40 total channels.
A major difference from previous ranging technologies is the introduction of two roles: initiator (device calculating distance to the opposing device) and reflector (device responding to the initiator), with ranging performed based on a connection between these devices. “A notable advantage is that relatively high-precision ranging is possible with just one antenna,” said Okada. “However, using multiple antennas improves accuracy when considering multipath effects. Bluetooth® Channel Sounding supports up to four antenna paths and includes multiple security features as standard.”
Channel sounding use cases
Channel sounding can be applied in various scenarios such as automotive remote keyless entry, enabling proximity-based locking/unlocking and user enhancements like seat adjustments upon detecting a person. It can also be used for loss prevention via geofencing, where alerts are triggered when tagged items are moved beyond a designated range in retail environments. It is similarly useful for access control and asset management in facilities like hospitals, tracking personnel and granting access only to authorized individuals while also simplifying asset management and tracking stay duration.
Channel sounding can be utilized in many location-based applications requiring high precision.
Bluetooth Channel Sounding and other ranging technologies
“At Silicon Labs, we are excited about the potential of Bluetooth® Channel Sounding which offers high accuracy in distance measurement, even with a single antenna,” said Okada “This makes it highly user friendly, though accuracy improves with the use of multiple antennas. One key advantage of Bluetooth Channel Sounding is that it is standardized for use after connection and encryption, making it ideal for secure applications.”
While Bluetooth® Channel Sounding offers excellent accuracy, it is important to recognize the complementary role of other Bluetooth technologies like RSSI and AoA/AoD. RSSI is widely used for estimating distance based on signal strength and works well in many scenarios, though environmental factors can affect accuracy. AoA/AoD provides another powerful tool for Bluetooth connectivity, measuring the relative angles between devices to determine their distance. While AoA/AoD does not always require a direct connection, its antenna array can become quite large due to the need to capture phase differences.
Each of these technologies — RSSI, AoA/AoD, and Bluetooth® Channel Sounding — has unique strengths, making it essential to choose the right one based on the application and specific use case. When used together, such as combining Bluetooth® Channel Sounding with AoA/AoD, Bluetooth technology can support highly accurate location-based services, even with a single device. This synergy holds great potential for enabling the next generation of user-friendly devices.
As Bluetooth® connectivity continues to evolve, we at Silicon Labs are committed to driving innovation with these technologies, ensuring that Bluetooth remains the leading solution for precise, scalable, and reliable wireless communication across industries.
Yasuaki Okada, Silicon Labs
“As Bluetooth connectivity continues to evolve, we at Silicon Labs are committed to driving innovation with these technologies, ensuring that Bluetooth remains the leading solution for precise, scalable, and reliable wireless communication across industries,” said Okada.
