What you’ll learn:
- What is Bluetooth Auracast broadcasting?
- What is Bluetooth Channel Sounding?
The Bluetooth SIG showed off two new Bluetooth features at this year’s Consumer Electronics Show, including Auracast and Channel Sounding. I spoke with Dave Hollander, Bluetooth SIG Vice President of Marketing, and Damon Barnes, Bluetooth SIG Director of Technical Marketing, about these new features (watch the video above).
Auracast Brings Broadcasting to Bluetooth
In the past, Bluetooth was primarily a personal area network (PAN). A central device like a smartphone or PC could exchange audio with devices like microphones and headphones as well as I/O devices such as keyboards and mice.
Auracast targets a scenario where audio will be streamed to more than one Bluetooth audio device. This is akin to radio broadcasts or more similar to Wi-Fi connections to multiple devices like Wi-Fi speakers. Auracast broadcast nodes tend to be fixed and have a more robust power source, allowing for a higher-power transmitter that provides longer range operation.
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There are a number of use cases, such as providing broadcasts of meetings for each room in a museum, or in auditoriums. The latter is handy for those with hearing aids as well as those with earbuds and headphones. It could be very useful in noisy environments, supported by augmented-reality (AR) glasses with audio output.
Bluetooth Channel Sounding for Distance Measurement
Bluetooth Channel Sounding tales on an entirely different application—it can provide the distance between a pair of Bluetooth devices. The technology uses two different mechanisms.
Phased-based ranging (PBR) delivers precise measurements by checking the phase difference of reflected radio waves (Fig. 1). There’s an initiator and a reflector, with the initiator sending the initial signal. Multiple frequencies are used to improve the accuracy.
A secondary approach leverages round trip time (RTT) when sending packets (Fig. 2). It can be used to mitigate man-in-the-middle (MITM) security attacks. Encrypted data packets prevent spoofing by an attacker. The initiator determines the distance based on the RTT.
Bluetooth Position Information
Bluetooth Low Energy (BLE) supports angle-of-arrival (AoA) and angle-of-departure (AoD) methods of signal direction estimation, although not all devices have such support. At this point, channel sounding can provide distance measurements with about 10-cm accuracy, which is sufficient to determine if a device is in a room. It doesn’t include an angular component without the AoA or AoD support.
Position could also be determined using triangulation between multiple devices, but this is likely only useful for a small set of applications. Though other wireless positioning systems are available, the channel-sounding feature has the advantage of using existing Bluetooth support.
