1 Introduction

Ranging is a process or method to determine the distance from one location or position to another. Bluetooth based ranging is currently used in many applications wherein distance between the two Bluetooth devices in range is determined by using the received signal strength indication (RSSI). Additionally, Bluetooth devices can be localized with distance measurement from multiple (at least three) Bluetooth devices in known fixed locations (also known as anchor nodes) using trilateration methods.

There are several ranging and localization enabled applications including:

• Smart access designs involving remote keyless entry, passive entry passive start (PEPS), and digital key access designs with broad adoption in automotive car access
• Item finding
• Asset tracking
• Localization
• Indoor navigation
• Proximity services

Optimum ranging designs address the following key factors to enable broad proliferation and adoption of the technology in a wide range of distance measurement applications:

• High accuracy
• Long range
• Low power
• Increased security
• Real time user experience
• Low system cost
• Easy for broad market scalability and adoption

The upcoming Bluetooth Channel Sounding (CS) feature considers all of these factors to provide a new high-accuracy distance measurement method between two Bluetooth devices.

The Bluetooth specification has been evolving since the inception by adding new features to not only enable new markets and applications but also, address challenges or limitations in existing applications to make use of the Bluetooth ecosystem that already exists to enhance user experience and lower the overall system cost. On the same lines, the upcoming Bluetooth Channel Sounding feature is expected to enhance existing ranging designs and enable new applications.

Bluetooth LE uses narrow band technology that supports long range and low power wireless data communication. The Bluetooth channel sounding feature uses phase-based ranging across multiple frequency tones to perform high accuracy distance measurement and round-trip time of flight measurements to mitigate man-in-the-middle based security threats against distance manipulation. Additionally, the Bluetooth LE radio technology has been adopted in majority of the smart phones and in a growing number of IoT devices, thereby, paving an easy path to broad market scalability and adoption compared to other wireless ranging technologies.

The following sections include the basics of Channel Sounding feature and procedure for performing secure ranging.