Bluetooth Channel Sounding for Proximity-Based Security: Nordic’s Meter-Perfect Access Control

What if your front door only opened when you were exactly one metre away? No fumbling for keys, no app tapping—just your phone in your pocket and a Bluetooth signal that knows exactly how close you are. At Embedded World 2025, Nordic Semiconductor showcased a smart and simple way to enable Bluetooth channel sounding for proximity-based security.

Gone are the days of “close enough” unlocking. We’re entering the era of precise, permissioned proximity.

What Is Bluetooth Channel Sounding?

Put simply, Bluetooth channel sounding is a clever method of estimating distance using Bluetooth Low Energy (LE) signals—without requiring any additional hardware.

Rather than guessing proximity based on signal strength, which varies wildly in real-world conditions, channel sounding measures the phase shift of a signal as it bounces between two devices. Nordic’s demo used 72 frequencies to ensure accuracy. The result? Centimetre-level precision using existing Bluetooth infrastructure.

Why It’s Better Than Traditional Bluetooth Ranging

Traditional Bluetooth can detect that your phone is “near” your smart lock—but that could mean anything from 30 cm to 30 metres. That’s not ideal if you’re in your garden and your front door decides to unlock itself because you’re still technically “in range”.

With Bluetooth channel sounding for proximity-based security, you can tell the lock: “Only open when I’m within 1 metre.” That’s a whole new level of trust and control, all without new chips or power-hungry components.

How It Works (and Why Engineers Should Care)

Design engineers, here’s the fun part. Channel sounding sends a dedicated Bluetooth signal from Device A to Device B and back again. By analysing the phase shift of the returning signal across multiple frequencies, it calculates distance with surprising accuracy.

Crucially, this method works within the existing Bluetooth LE 6.0 spec. So if your product already supports Bluetooth LE, adding proximity-based security features doesn’t require a BOM overhaul—just some clever firmware and algorithmic magic.

Real-World Applications Beyond Locks

• Asset tracking: Think smart tags that alert you if something’s been moved—accurately.
• Find-my-device tech: Like AirTags, but without the ultra wideband chip or the battery drain.
• Hands-free access: From cars to industrial gates, enable secure entry only when the user is close enough to mean it.

And with upcoming support baked into Android and iOS APIs, this will soon be a plug-and-play upgrade for mobile-based security.

Nordic’s Bluetooth-Driven Future

Nordic Semiconductor’s approach is elegant: use what you’ve already got. By working within the Bluetooth spec and leveraging robust development kits, they’re making proximity-based security scalable, low-cost, and ready for mass deployment.

With Bluetooth channel sounding for proximity-based security, Nordic is unlocking a world where distance matters—and doors (or data) only open when they really should.

Find out more at nordicsemi.com.