Bluetooth® Channel Sounding(Bluetooth 6.0) is the new benchmark for accurate and secure BLE localization. Compatible with Direction Finding AoA/AoD technology, it enables a wide range of applications such as secure georeferencing and intelligent access control.
ELA Innovation expertise:
This article is based on in-house training provided by ELA Innovation’s R&D / Design department.
Introduction: 15 years of Bluetooth® localization evolution
Bluetooth® localization has come a long way. Here are the key steps:
- 2010 – Find Me Profile: simple proximity detection, with no notion of distance.
- 2013 – Beacons & RSSI: approximate distance estimation for retail or museums, but limited precision and security.
- 2019 – Direction Finding (AoA/AoD): measurement of signal direction using RF phase, improved accuracy but distance still uncertain.
- Today – Channel Sounding (Bluetooth 6.0): precise, reliable and secure localization, suitable for digital keys, geotagging or “Find My” services.
Channel Sounding marks the entry of Bluetooth® into an era where distance becomes reliable, security is natively integrated, and use cases multiply.
1. What is Bluetooth® Channel Sounding and precise BLE localization?
Channel Sounding is an advanced feature that measures the distance between two Bluetooth® devices with precision and robustness.
It combines two complementary methods:
- Phase-Based Ranging (PBR ): ultra-precise distance measurement based on RF signal phase analysis.
- Round-Trip Timing (RTT ): measures signal travel time to eliminate ambiguities and enhance safety.
Channel Sounding operates in connected mode, compatible with Direction Finding (AoA/AoD) and Bluetooth 6.0 technologies.
3. How Channel Sounding estimates Bluetooth 6.0 distance
3.1 Phase-Based Ranging (PBR): ultra-precise distances
Analyzes the phase of RF signals for highly accurate estimation, even in complex radio environments.
3.2 Round-Trip Timing (RTT): distance validation
Measures signal round-trip time, serves as a check to eliminate ambiguities and protect against manipulation attempts.
By combining these two methods, Bluetooth® achieves a level of precision never seen before.
4. Enhanced Channel Sounding Bluetooth® security
Built-in mechanisms protect against :
- Spoofing: Bluetooth identity theft
- Relay / MITM: signal interception and retransmission
- Distance manipulation: deliberate false estimation of proximity
Key mechanisms :
- Advanced randomization: random tones, bit sequences and antenna paths
- PBR + RTT cross-validation: inconsistencies detected → alert
- Anomaly detection: suspicious phase variations or delays reported
5. Comparison of the main BLE localization technologies
| CISO | Angle of arrival / departure of departure | Channel Sounding | |
| Location metric | Distance estimation by measuring power level at reception | Calculating the relative angle between two points | Precise distance measurement by time-of-flight (ToF) and phase (PBR) |
| Antenna requirements | A single antenna | Antenna array required by the specification. | The use of multiple antennas is not required, but does improve accuracy. |
| Bluetooth® LE connectivity | Connected and unconnected modes | Connected and unconnected modes | Connected mode only |
| Performance | ± 5 m, highly sensitive to interference | ± 3° azimuth, ± 5° elevation Around 1m | ± 0.3 m for < 5 m with PBR ± 0.5 m for > 5 m with PBR |
| Benefits by Solution | Support for RSSI measurements in existing Bluetooth LE products | – Scalable solution for real-time position tracking. – Battery life from 5 to 10 years. | – Enhanced safety (proximity detection) – Centimeter accuracy. – Suitable for critical applications. |
| Energy consumption | Very low power consumption | Low power consumption | Slightly higher |
6. Bluetooth® Channel Sounding use cases
6.1Geo-Fencing applications
Channel Sounding creates ultra-precise control zones by measuring distance. In the automotive sector, this means unlocking on approach: the vehicle automatically detects the presence of its user and activates contactless access.
This technology also paves the way forpersonalized welcome functions. Lights, screens and air conditioning can be activated automatically as the user approaches, while the driver’s station adjusts the seat, mirrors and personal settings to suit the user’s profile.
Channel Sounding enables automatic locking and unlocking by proximity, reinforcing security and simplifying the user experience.
In retail, these capabilities are exploited for anti-theft protection and tracking of high-value items. Goods can be located in real time, and alerts or notifications are triggered as soon as a product leaves a defined area or is subject to unauthorized movement.
6.2Indoor facility management
In intelligent buildings and industrial facilities, Channel Sounding enables intelligent access control. Sensitive areas can be secured dynamically, with :
- Restricting access to unauthorized persons
- Sendsalerts to central systems in the event of prolonged presence
Access managers benefit from automatic authentication and seamless opening for authorized personnel, improving both security andoperational efficiency.
For asset management, Channel Sounding enables the approximate location of all mobile equipment and optimizes workflows within the plant.
6.3 Positioning and monitoring fixed equipment
Beyond people, Channel Sounding is effective for positioning static devices such as access points or anchors. The devices alternate the roles of initiator and reflector to achieve :
- Precise inter-device distance measurements
- Automatic construction of a geometric network map
These functions also enable rapid identification of anomalies: suspicious beacon movements, malicious manipulation attempts or abnormal position drifts are immediately detected.
Channel Sounding doesn’t just locate objects or people: it provides intelligent, secure mapping of the entire radio network, essential for critical installations.
FAQ – Bluetooth® Channel Sounding
Q1: How accurate is Channel Sounding?
The PBR + RTT combination provides highly accurate distance estimation, superior to RSSI or AoA/AoD methods alone.
Q2: What’s the difference between Channel Sounding and RSSI?
RSSI is based solely on the strength of the received signal, while CS uses the phase and travel time of the signal, improving precision and safety.
Q3: Does Channel Sounding work with AoA/AoD?
Yes, it is compatible and can complement directional measurement to offer precise distance + orientation.
Q4: Does Channel Sounding require Bluetooth 6.0?
Yes, CS technology is one of the advanced features introduced with Bluetooth 6.0.
Conclusion
Channel Sounding is a major advance in Bluetooth® localization, offering precision, reliability and security. Thanks to this technology, Bluetooth® becomes a strategic tool for critical applications: digital keys, access control, retail, intelligent buildings or secure georeferencing.
