Bluetooth channel sounding—a new protocol stack designed to enable secure and precise distance measurement between two Bluetooth Low Energy (LE) devices—is propelling Bluetooth technology into a new era of location awareness. It offers true distance awareness while enhancing Bluetooth devices’ ranging capabilities.
Bluetooth channel sounding’s use spans from helping locate devices such as phones or tablets to digital security enhancements like geofencing. It can also be used in smart locks, pet trackers, vehicle keyless entry, and access control applications.
Hardware and software solutions are starting to emerge to fulfill the potential of Bluetooth channel sounding and provide sub-meter accuracy for Bluetooth-empowered devices. These solutions include reference boards, development kits, and software stacks.
Below are two design case studies demonstrating the potential of Bluetooth channel sounding technology.
Radio board and antenna hardware
Silicon Labs’ xG24 radio board—designed to work with Pro Kit—aims to help developers create and prototype products using Bluetooth channel sounding for precise distance estimation. Pro Kit includes a BRD4198A EFR32xG24 2.4 GHz +10-dBm radio board, a dipole antenna, and reference designs. It works with either a coprocessor with an external MCU or a wireless system-on-chip (SoC) with an integrated MCU.
Another xG24 Dev Kit features a dual-antenna PCB design and a channel sounding visualizer tool to allow developers to view distance measurements in real time. Single-antenna hardware offered in the Pro Kit has fewer antenna paths and limited multipath information, which makes it more suitable for basic Bluetooth channel sounding applications.
Figure 1 USB or coin cell powered development platform with a dual-antenna design and up to +10 dBm output power. Source: Silicon Labs
On the other hand, dual-antenna hardware offers higher accuracy, better spatial performance, and enhanced multipath resolution, making it suitable for advanced applications such as key fobs and tags that demand precise distance estimation (Figure 1). Its antenna diversity also bolsters signal quality and robustness.
Software stack
Bluetooth channel sounding technology uses phase-based ranging (PBR), round trip time (RTT), or both to accurately measure the distance between two Bluetooth LE-connected devices. PBR utilizes the principle of phase rotation in RF signals to determine precise distance between two devices. On the other hand, RTT, a communication channel, refers to the duration a signal takes to travel from the initiator to the reflector and back again.
The above solution from Silicon Labs uses both, employing RTT to verify and cross-check the PBR measurements. However, Metirionic, a German supplier of wireless ranging and positioning technologies, offers an alternative to both PBR and RTT by leveraging the channel impulse response (CIR) technique for highly accurate and reliable distance estimation.
Figure 2 The channel sound evaluation kit is built around Nordic Semiconductor’s nRF54L15 wireless MCU. Source: Metirionic
Its Bluetooth channel sounding evaluation kit—Metirionic Advanced Ranging Stack (MARS)—is a low-power signal-processing upper-layer software (Figure 2). It can run on Nordic’s nRF54L15 embedded MCU, on an external MCU or processor, or on a host PC to ensure precise, reliable and real-time ranging and location accuracy for industrial, Internet of Things (IoT), real-time location services (RTLS), logistics, and secure access applications.
Related Content
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- How Bluetooth Channel Sounding Compares to Other Location Tech
- Bluetooth Channel Sounding Improves Distance Estimation Accuracy
- New wireless MCUs feature software radio and Bluetooth channel sounding
- Rohde & Schwarz to show measurements on novel Bluetooth Channel Sounding signals
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