Silicon Labs is utilizing the unique Bluetooth Channel Sounding technique to create a wide range of high accuracy SoCs, modules, and other wireless products for various wireless applications. This technique has been developed by the Bluetooth Technology Group to unlock the true potential of IoT. This technique creates a seamless web of interconnectedness by enabling the highest accuracy distance measurement for intelligent and context-aware systems such as smart door locks, access systems, and asset tracking and management.
How Does Channel Sounding Work?
Channel sounding is a method for estimating distances between two devices, designated as the initiator and the reflector. They exchange information across 72 RF physical channels, with the initiator transmitting first, followed by the reflector's response. This alternating transmission and reception enable precise distance measurements. The technique employs Phase-Based Ranging (PBR) or Round-Trip Time (RTT) or both for accurate coordination across the 2.4 GHz spectrum. It also supports one to four antenna paths to improve measurement accuracy and reliability.
Round Trip Time (RTT)
Round trip time (RTT) in a communication channel refers to the duration a signal takes to travel from the initiator to the reflector and back again. By assessing the Time of Flight (ToF) — the time it takes for a packet to be exchanged between the initiator and the reflector — the distance can be estimated. To achieve this, both devices record the Time of Arrival (ToA) and the Time of Departure (ToD). Analyzing the differences between ToA and ToD for both the initiator and the reflector provides the data necessary for a reliable distance calculation. Additionally, in terms of security, since time cannot be reversed, RTT is considered highly secure.
Phase-Based Ranging (PBR)
Phase-Based Ranging (PBR) utilizes the principle of phase rotation in RF signals to determine distances. In this process, the initiator sends a signal with specific frequency and amplitude information, and the reflector measures the phase of this received signal before sending a response. By comparing the phase differences between the signals from both devices, their relative distance can be determined. PBR offers a significant security advantage, especially compared to methods like RSSI (Received Signal Strength Indicator). The complexity of manipulating phase information makes PBR a more secure technology for distance measurement.
Channel Sounding Use Cases
Vehicle Access Entry
One primary use-case for Channel Sounding is remote keyless entry to a vehicle. It is used for zonal detection through ranging to authenticate approaching users and unlock the vehicle. It utilizes Bluetooth Ranging through the established connection between the data channels - in this case, the key fob or phone and the anchor points on the car.
Indoor Ranging
Channel Sounding offers a solution for facilities like hospitals and warehouses, enabling both restricted access and asset tracking. It authenticates and allows entry to authorized individuals at doorways, enhancing security. It can also be used to monitor assets such as medical equipment or other high-value items.
Key Applications for Bluetooth Channel Sounding
Proximity Awareness: To develop Bluetooth Low Energy enabled devices that are used in securely controlling and restricting access to spaces. Examples include geofencing, door locks, and keyless entry.
Locating Solutions: For applications like asset management and personal item tracking. It provides the perfect blend of precision and convenience. Examples include warehouse management, pet tracking, and item tracking.
Click here to learn more about Silicon Labs' target applications for Bluetooth Channel Sounding.
Click here to learn more about various Bluetooth SoC solutions from Silicon Labs.
