Bluetooth Channel Sounding: Precise localization in industry and rescue operations

Distance Measurement With Bluetooth Centimeter-Accurate Positioning for Industrial And Safety-Critical Applications

2025-05-13 From | Translated by AI 3 min Reading Time

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Bluetooth channel sounding takes wireless localization to a new level of precision. Thanks to centimeter-accurate distance measurements, opportunities arise from safety-critical industrial applications to person localization in rescue operations.

Centimeter-accurate determination of distances with Bluetooth channel sounding. Accidents between humans and machines can be avoided.(Image: Metirionic) — Centimeter-accurate determination of distances with Bluetooth channel sounding. Accidents between humans and machines can be avoided.
(Image: Metirionic)

The integration of Bluetooth channel sounding in industrial and safety-critical applications opens up new possibilities for real-time location, collision avoidance, and secure access control. In contrast to classic methods such as RSSI (Received Signal Strength Indicator) or AoA (Angle of Arrival), which are based on signal strength or angle of arrival, channel sounding analyzes the complex channel transfer function (CTF) and uses it for precise distance measurement. This is done independently of environmental influences such as multipath propagation.

The Bluetooth standard does not specify a specific calculation method, but offers an open framework for algorithmic developments. Tools such as the Metirionic Advanced Ranging Stack (MARS) are available for developers. They enable localizations of 4 to 12 inches with complete channel impulse response (CIR) analysis. This is also possible in complex environments.

Technical Fundamentals: From PBR to MARS

A classic example is Phase-Based Ranging (PBR), which evaluates phase shifts over multiple frequencies. In simple line-of-sight scenarios (LoS), precise results are indeed possible. However, as soon as reflections come into play, such as in factory halls or urban environments, accuracy suffers significantly.

CIR-based methods like MARS convert the CTF into a time domain signal using IFFT. This allows the direct runtime component to be separated from reflected signal paths. The result: robust, interference-resistant distance measurements with submeter to centimeter accuracy, depending on system bandwidth.

Examples of Applications in the Field

Search and Rescue Operations (SAR): In alpine rescue scenarios or after building collapses, channel sounding enables accurate localization of buried individuals, even under debris or dense vegetation. With drones and BLE beacons, the search area can be automated and precisely narrowed down. In a simulated operation, a buried person was located on 20 m² (about 215 square feet) in less than twelve minutes. This is a time saving of over 60% compared to traditional methods.

Industrial Facility Management and Collision Avoidance: In production environments, the technology prevents accidents between humans and machines. For example, a forklift can automatically brake when a worker is within a defined radius. At the same time, integration into Bluetooth mesh networks allows efficient control of autonomous guided vehicles (AGVs) or lighting infrastructures.

Keyless entry and access control: Modern access systems benefit from the combination of physically based distance verification and cryptographic protection. Channel sounding with RTT extension reliably protects against relay and man-in-the-middle attacks. A real advancement compared to previous BLE-based passive keyless systems.

Agriculture and animal tracking: Bluetooth channel sounding not only optimizes tracking of large herds but also enables early detection of health problems based on movement patterns. Initial commercial solutions demonstrate that animal losses and resource use can be significantly reduced.

Evaluation Kits And Integration Depth

The Evaluation Kit DMK-54L.(Image: Metirionic) — The Evaluation Kit DMK-54L.
(Image: Metirionic)

With the Evaluation Kit DMK-54L for the Nordic nRF54L15, presented at the Embedded World 2025, developers can test the technology in real-world scenarios: from RTLS to access control to machine interaction. The platform is scalable, energy-efficient, and optimized for high integration capability.

Bluetooth channel sounding, in conjunction with advanced algorithms such as MARS, unlocks an unprecedented level of precision, robustness, and security based on existing Bluetooth infrastructures. Whether in the factory hall, in rescue operations, or at the gate: the technology provides a flexible foundation for new applications in the era of IoT, Industry 4.0, and digital security. (heh)

Channel Sounding: The new Bluetooth standard combines various proven methods for wireless distance measurement. (Image:AI-generated / DALL-E)

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