Slightly advanced topic for today. It’s a new little specification in the new Bluetooth 6.0 standard which I think is interesting. Bluetooth Channel Sounding is a feature that enables precise distance measurement between Bluetooth devices.

Unlike earlier methods relying on signal strength (RSSI), Channel Sounding uses phase-based ranging and round-trip timing. These techniques leverage phase & frequency of radio BLE waves at 2.4GHz to calculate distances with potentially a few tens of centimeter precision even with large 50m+ line of sight ranges.
Here’s how it works: one BLE device sends a signal with a known phase and frequency. The second device echoes the signal back, maintaining phase continuity. By comparing phase shifts and factoring in timing, the system calculates the distance between devices. This will effectively give you much better precision than the older RSSI techniques. BLE 5.1 had introduced direction finding in Bluetooth based on the angle of arrival and angle of departure. However, the implementation issue was that you needed multiple antennas on either the transmitter or receiver end. Channel Sounding can work with a single antenna on each side making implementation easier.
Why does this matter? Think of the Locate Me feature in your phone or key trackers. With Channel Sounding, the search goes beyond “it’s nearby” to pinpoint exact locations, even in complex environments. The technology also enhances digital keys, ensuring your car or door unlocks only when you’re within a precise range, significantly improving security. It will have applications in indoor navigation, asset tracking, VR controller tracking etc. I very well see Apple ditching UWB tech in their air tags in the future for this tech as airtags do contain an additional BLE chip. Your future phones will definitely have this feature.
Exciting times ahead for BLE! If you’re curious to dive deeper, a fantastic white paper has recently been published on the official Bluetooth website. It’s a great read that keeps the concepts clear and jargon-free, definitely worth checking out!
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