Bluetooth’s New Era: The Role Of Channel Sounding And Adaptable Testing Solutions

By Jake Harnack and Alejandro Escobar Calderon

Bluetooth technology has experienced a remarkable transformation since its inception, evolving from a basic tool for data transfer to a near-ubiquitous wireless technology used for audio streaming, location services, and smart-home networks. As sales of Bluetooth-enabled devices nears 5 billion units per year in 2024, the Bluetooth standard is evolving beyond its core functionality of point-to-point data transfer and audio streaming to better support location tracking services that require secure, high-accuracy distance measurements. While the Bluetooth Low Energy (LE) specification currently supports presence, distance, and direction measurements, the upcoming Bluetooth Channel Sounding feature aims to significantly improve the security and accuracy of distance measurements between Bluetooth devices, ensuring the technology keeps up with the ever-evolving needs of users in this space.

Location services for connected devices

Location services have become a key application area for wireless connectivity standards, both at an enterprise-level for commercial asset tracking and supply-chain management, and at a consumer-level for tracking personal items and securely accessing a vehicle or home. The ubiquity and low power consumption of Bluetooth make it an ideal technology for location services, and the number of Bluetooth devices that support location services is expected to grow at a 22% CAGR for the next 5 years. However, to meet the needs of emerging technology in this space, the Bluetooth standard required a more accurate and secure method of measuring distance than the existing implementation based on received signal strength indicator (RSSI).

Understanding channel sounding

Distance measurements in Bluetooth LE are currently based on RSSI, which measures the relative power of a received signal and calculates the distance between two devices from the path loss. While straightforward to implement and useful as a coarse distance measurement, RSSI is susceptible to interference, vulnerable to man-in-the-middle attacks, and not as accurate as other methods. Bluetooth Channel Sounding vastly improves the accuracy and security of distance measurements in Bluetooth LE. By leveraging a combination of phase-based ranging and time-of-flight measurements, it can significantly increase distance measurement accuracy down to tens of centimeters.

This combination of security and high accuracy is critical for applications like automotive digital keys, which not only require a vehicle to detect when its owner is nearby or inside the car, but also use it prevent any unauthorized users from accessing or starting the car. In a Bluetooth Channel Sounding procedure, the vehicle and key exchange tones at multiple frequencies across the standard 2.4 GHz Bluetooth band and measure the phase offsets to calculate distance. For an added layer of security, a channel sounding procedure can also include a round-trip-time measurement to ensure that the key is physically close to the vehicle and not subject to a relay attack.

How test is impacted by recent Bluetooth advancements

Given the importance of phase measurements in a channel sounding procedure, new PHY layer tests were defined to measure the phase of a channel sounding tone, calculate the detrended phase, and ensure phase stability. Various other tests such as modulation characteristics (df1/df2/df3/df4), modulation spectrum, power ramp, and antenna switching integrity are also supported by software such as NI’s RFmx Bluetooth. While Bluetooth Channel Sounding is the newest feature today, other substantial changes to the Bluetooth LE specification are right around the corner. With proposals to enable higher data throughput up to 7.5 Mbps and open additional spectrum in the 5/6 GHz band, partnering with a knowledgeable test vendor is the only way to ensure reliable performance and time-to-market in a rapidly evolving landscape.

NI’s RF solutions offer flexibility and precision, supporting detailed measurements and simulations to ensure devices meet high standards of performance. With NI’s RFmx software, you can tackle Bluetooth testing challenges head-on through precise, automated measurements and enhanced analysis capabilities, ensuring reliable performance and compliance. NI’s commitment to innovation and adaptability is vital as Bluetooth technology continues to advance, providing companies with the tools needed to navigate the complexities of new technologies and maintain quality standards. In the ever-evolving landscape of wireless technology, those organizations that elevate their teams with the right tools and processes will be able to capture the opportunity that lies ahead. To learn more, click here.

Alejandro Escobar Calderon is a senior solution marketer at NI/Emerson Test & Measurement.