For a car door to unlock when your phone approaches, or for an app to show more reliably how many meters remain to a lost item, knowing that a device “has Bluetooth” is no longer enough. Introduced with Bluetooth Core 6.0, Channel Sounding is designed to calculate the distance between two connected devices more precisely using the radio signal’s phase and round-trip time. However, advertising a product as Bluetooth 6.x does not necessarily mean this feature is actively available. Hardware, software, and app support must all be verified before purchase.
What does Channel Sounding change?
Traditional Bluetooth proximity solutions often use received signal strength, or RSSI, as a proxy for distance. Because walls, the human body, carrying a device in a pocket, antenna orientation, and interference can change signal strength, this method provides only an approximate answer to “Is it nearby?” and is not reliable for exact distance. Bluetooth Channel Sounding can instead use phase-based ranging (PBR) and round-trip time (RTT).
PBR evaluates phase differences across multiple frequencies to produce a finer distance estimate. RTT derives an independent distance bound from the time a signal takes to travel between two devices and back. The Bluetooth SIG says using both methods together provides an additional check, particularly against relay attacks that try to make a distance appear falsely short. This approach is important for car and door keys, item-finding systems, computers that unlock when a person approaches, and industrial security applications.
Do not treat “Bluetooth 6” as proof of support
Bluetooth Core versions contain many independent features, and manufacturers may not be required to implement all of them. A product page that says only “Bluetooth 6.0,” “next-generation Bluetooth,” or “precision finding” does not confirm Channel Sounding support. Look for the feature’s full name in the technical specifications, and check the manufacturer’s support documentation to learn which phones, operating-system versions, accessories, and apps it works with.
According to the Bluetooth SIG, Channel Sounding may require new protocol and physical-layer capabilities, so whether it can be added to an existing product through a software update depends on the hardware and manufacturer. For promises that it is “coming in a future update,” look for a published schedule, a supported model number, and evidence that the update has actually been distributed. Base your decision on what works on the day of purchase, not on a future possibility.
Verify support at both ends of the connection
Precise measurement takes place between two devices. Even if the phone is compatible, the feature will not work unless the tag, lock, or vehicle receiver has the required radio hardware and software; the reverse is also true. The manufacturer’s compatibility table should list the phone model, region, operating system, and accessory software together. For enterprise access systems, the hub, lock, mobile identity app, and management software should also be checked.
For an item-finding product, distinguish among nearby detection, direction guidance, and distance display. Channel Sounding primarily provides secure, precise distance information; the standard itself does not define a single direction-finding algorithm. To display direction, an app may combine other Bluetooth location features, multiple antennas, or another radio technology. Do not assume that an arrow on the screen is an inherent result of Channel Sounding alone.
Understand that it is not the same as UWB
Ultra-wideband (UWB) and Channel Sounding can provide similar user experiences in precise proximity scenarios, but they are different radio technologies. The presence of one does not prove the presence of the other. Manufacturers may combine Bluetooth RSSI for general proximity detection at a distance, Channel Sounding for precise distance measurement as the user approaches, and UWB for another precision-location stage. Which is “better” depends on the product’s antenna design, power consumption, software, environmental conditions, and security implementation.
A phone without UWB does not mean that every function of a Channel Sounding product will fail. Likewise, a phone with UWB cannot automatically perform precise measurements with every Bluetooth 6.x accessory. Rely on the manufacturer’s explicit compatibility list.
Ask security questions about digital keys
If a valuable asset such as a car, building, or safe will be opened, a claim of centimeter-level accuracy is not enough by itself. Find out whether the product uses PBR and RTT together, how the key can be revoked if the phone is lost, whether strong user authentication is available, and whether the system remains securely locked after a failed measurement. It is helpful if users can limit the automatic-unlock distance and review activity logs.
Although Channel Sounding includes mechanisms against relay attacks, no wireless feature can compensate for weak account security, an unprotected screen lock, or a compromised cloud account. Keep phone biometrics, a strong device passcode, remote-finding features, and a passkey or strong second factor for the account enabled. Apply time and permission limits when sharing a digital key.
How should it be tested in the real world?
Update the phone, accessory, and app software before the first pairing. During pairing, make sure you select the serial number or identifier of the product physically in your possession rather than an unknown nearby device. Read why the app requests location, nearby-device, and background-operation permissions; do not grant unexplained contacts or microphone access for basic functionality.
Test the distance display at several fixed points in an open area. Then reproduce everyday conditions by keeping the phone in a pocket or bag and holding it in different orientations. Walls, metal doors, crowds, and other 2.4 GHz devices can affect the result. When testing a digital lock, verify not only that it opens but also that it remains closed outside the specified threshold. In a controlled setting, test leaving the phone indoors while approaching from outside, closing the app, turning off Bluetooth, and enabling battery saver.
Do not treat a very low error observed in a single measurement as a continuous guarantee. Although the Bluetooth SIG discusses a goal of centimeter-level accuracy and approximate figures from early implementations, actual results vary with the antenna, transmit power, software algorithm, and environment. Review the error range, test conditions, and security behavior that the manufacturer specifies for its own product.
Purchase checklist
The product’s technical documentation should explicitly state “Bluetooth Channel Sounding”; both ends of the connection should support it; the required operating system and region should be specified; the manufacturer should document security and lost-device procedures; and real-world testing should be possible within the return period. Do not rely solely on the Bluetooth version number, the word “precise,” or the best distance claim achieved under laboratory conditions. This will help you distinguish the new standard’s actual benefits from a marketing label and assess compatibility and security together, especially in sensitive scenarios such as digital keys.<figure class="article-inline-image"><img src="/api/media/019ffc2e-347c-762b-a9f7-57f55af6b434?v=8676" alt="Testing the distance between a phone and a small tracker at different points" width="1200" height="675" loading="lazy"></figure><figure class="article-inline-image"><img src="/api/media/019ffc2e-3503-7886-bd6d-c6b3f56ffd37?v=8928" alt="Testing a smart door opening in a controlled manner as a phone approaches" width="1200" height="675" loading="lazy"></figure>