Understanding Bluetooth Channel Sounding: How It Works, Benefits, and Applications

Introduction

Bluetooth technology is a prominent part of the wireless communication world. It enables indoor positioning and seamless connection between Bluetooth Low Energy (BLE) devices. Introduced in Bluetooth 6.0, Bluetooth Channel Sounding technology has attracted attention from many industries. It's known for the secure, precise-ranging capabilities of Bluetooth devices. But what exactly is it, and how can it be a game-changer in Bluetooth positioning? Follow the blog, and we'll dive into more details about Bluetooth Channel Sounding.

The History of Channel Sounding

Bluetooth positioning technology has been developed as industries keep requiring more accurate and secure tracking solutions. In the beginning, BLE used beacons to achieve simple proximity detection. These beacons sent out signals that nearby devices could pick up, estimating distance based on signal strength (RSSI). This made it possible for basic applications like simple asset tracking and proximity marketing.

In Bluetooth 5.1, Bluetooth technology made a great leap forward in positioning with Bluetooth Direction Finding. Bluetooth 5.1 introduced new methods like Angle of Arrival (AoA) and Angle of Departure (AoD) to make devices capable of sensing the direction of signals. Beyond that, it took accuracy to the next sub-meter level. These changes have transformed indoor navigation and location-based solutions.

What is Channel Sounding?

Bluetooth Channel Sounding is introduced in the Bluetooth 6.0 core specification for secure, fine-ranging between Bluetooth devices. It uses Phase-based Ranging (PBR) and Round-trip Time (RTT) to measure the distance, providing centimeter-level accuracy compared to the Received Signal Strength Indicator (RSSI). The combined use of these two methods makes Bluetooth Channel Sounding a considerable choice in applications requiring high security, such as digital keys and identity authentication.

How does Channel Sounding Work?

The secure, fine-ranging capability is achieved by two methods: Phase-based Ranging (PBR) and Round-trip Time (RTT).

Phase-based Ranging (PBR):

By measuring the phase difference of wireless signals, PBR technology can accurately determine the distance between two devices. There are two devices — the Initiator and the Reflector — involved in PBR. Here's how it works:

Signal Transmission: The Initiator sends out a radio signal with a known frequency and phase.

Signal Reception: The Reflector measures the phase of the received signal and sends a response back to the Initiator.

Phase Difference Measurement: The Initiator calculates the phase difference between the sent and received signals, which provides information on the signal’s travel time.

Distance Calculation: Using the known travel time and the speed of light or electromagnetic waves, the distance between the two devices is calculated.

Compared to solutions like RSSI, PBR offers more accurate measurements and is harder to manipulate.

Round-trip Time (RTT):

Round-trip Time (RTT) stands for the time it takes for a signal to travel from an Initiator to a Reflector and then back again to the Initiator. In a typical measurement system, the Initiator sends a signal to the Reflector. The Reflector then sends a response back to the Initiator. RTT is the total time taken for the signal to travel from the sender to the receiver and back. In Bluetooth Channel Sounding, RTT is used as a supplementary method to verify PBR measurements and prevent relay attacks from man-in-the-middle (MITM) attacks.

The Benefits of Channel Sounding

High-accuracy Distance Measurement: It provides precise distance measurements with centimeter-level accuracy, improving location tracking precision.

Security: The complexity of phase-based measurements makes it harder to spoof, enhancing security.

Enormous Bluetooth Device Ecosystem: Based on the standard Bluetooth protocol, the devices can leverage the large Bluetooth ecosystem and work seamlessly with other BLE devices and systems.

Low Power Consumption: BLE-enabled devices typically have long service lives. Some BLE-enabled sensors remain reliable for up to 5 years.

Versatility: In addition to Bluetooth Channel Sounding, Bluetooth 6.0 defines more new features to increase technical flexibility.

The Use Cases of Channel Sounding

Indoor Navigation

Bluetooth Channel Sounding performs well in areas where GPS signals are unreliable, like shopping malls, airports, and hospitals. It provides real-time indoor guidance that can enhance visitor experiences. Meanwhile, it ensures privacy protection in sensitive areas like hospitals.

Find My Solution

By accurately measuring the distance between devices, Channel Sounding can improve "Find My" applications. This can be used for locating lost items or tracking devices, offering reliable results even in crowded or signal-blocked areas.

Asset Tracking

Channel Sounding plays a key role in asset tracking solutions, ensuring the precise location of equipment or inventory in real-time. Its accuracy helps businesses track assets in warehouses, factories, logistics hubs, or other locations where high precision is required.

Proximity Marketing

With Channel Sounding, proximity-based marketing systems can target customers more effectively. By accurately determining customer locations, businesses can send personalized offers or advertisements when a customer is near a specific product or location.

The Comparsion of Channel Sounding and other Positioning Solutions

In comparing AoA vs channel sounding for positioning solutions, channel sounding provides a more detailed assessment of the wireless channel’s characteristics, including multipath effects, while AOA focuses on direction estimation. Here is the completely table of the comparison among channel sounding, AoA/AoD and RSSI:

The Future of Channel Sounding

The future of Bluetooth Channel Sounding looks promising. According to Bluetooth SIG, Bluetooth Channel Sounding provides huge technical flexibility to developers. It is set to address the location ambiguity issues in high-density environments, where traditional positioning methods may not work as well. A secure, fine-ranging positioning technology can help developers, especially in the IoT industry, unlock possibilities in more applications, such as high-value asset tracking, FindMy solutions, and digital solutions for end customers.