Bluetooth® is a ubiquitous wireless technology that improves the connectivity experience for millions of users. It’s reached a point where the novelty of instantly pairing data, audio and video content with headphones, speakers, keyboard and smartphones has all but worn off. So, does Bluetooth have anything left in its bag of tricks? Of course.

Bluetooth continues to evolve, and the most prominent updates fall into three categories. Let’s check the progress across each area, beginning with a relative newcomer that’s transforming location-based applications, Bluetooth channel sounding. Next, we’ll explore a high data throughput (HDT) feature for low-latency, lossless audio streaming. We’ll conclude with a look at updated specifications from the Bluetooth Special Interest Group (SIG) for enabling 5- and 6-GHz frequency bands.

Channel Sounding Improves Accuracy and Security of Location Finding

Introduced in 2010, Bluetooth Low Energy (LE) has expanded the convenience of wireless connectivity across a range of low-power products, for example, location-based asset tracking used to locate lost luggage or monitor in-transit commercial shipments. 

Typically, asset trackers have relied heavily on Received Signal Strength Indicator (RSSI) technology to measure the power level of the incoming radio signal. The power of the signal is, in simple terms, related to the distance from the source.

RSSI based method

But RSSI has weaknesses: it’s only accurate to about three to five meters and can’t correct for signal degradation due to physical obstacles, even common occurrences such as having your phone in your pocket. Also, it’s insecure and vulnerable to “relay attacks” that trick it into incorrectly measuring distance. This flaw can be used in vehicle thefts, for example, by allowing an attacker to intercept the signal and dupe the car into behaving as if the key fob is closer than it is.

The Bluetooth SIG has been working on these issues by adding new localization techniques to the Bluetooth LE standard, including angle of arrival and angle of departure measurement methods. While these new techniques have helped, they have their own limitations. 

In 2024, the Bluetooth SIG ratified a new specification called channel sounding, which is transforming the precision and security of Bluetooth location services by providing accuracy to around 50 cm. This is expected to improve the user experience across applications that rely on location, including asset tracking, geofencing, door locks and keyless entry while blocking “man in the middle” attacks by unlocking a car door only when the owner is in close proximity.

Channel sounding employs two mechanisms: phase-based ranging (PBR) and round-trip time (RTT) measurements. PBR relies on phase rotation in the radio signal to calculate the distance. The initiator device sends a radio signal with specific frequency and amplitude information, and the reflector measures the phase of the incoming signal before sending back the response. This procedure is repeated over the entire 2.4-GHz ISM band. Devices can then compute the relative distance between them by comparing the phase differences. PBR yields highly precise distance estimation. Channel sounding also uses RTT, where two devices exchange the signal and measure time of departure (TOD) and time of arrival (TOA) to compute one-way distance between devices (TOF). RTT is secure due to its use of cryptographically generated random sequences for measuring round trip propagation delay. By combining PBR and RTT, one can measure distance precisely and securely. 

Phase-Based Ranging (PBR)

While there are other wireless standards, such as UWB, are secure and accurate down to a few centimeters, channel sounding and UWB will share the stage as complementary technologies. Bluetooth enables secure and relatively precise location applications for low-cost and low-power devices, while UWB focuses on applications that need highly secure and centimeter-level accuracy. There are automotive secure-car-access applications where both channel sounding and UWB will be used, enhancing the user experience by providing secure and precise access control.

With deep expertise in PHY layer testing, LitePoint addresses the demands of Bluetooth channel sounding through its IQxel family of testers – purpose-built to perform comprehensive and accurate physical layer measurements. The focus revolves largely around phase measurement accuracy, frequency verification, and power-ramp profile measurements of both the transmitter and receiver. 

Each of these test cases must be run across different symbol rates and channel sounding modes to validate device performance, as both initiator and reflector. Having a tool that provides a simple interface to seamlessly automate these test cases and run them in loops is invaluable.

Bluetooth SIG Strives to Commercialize HDT As a Value-Added Feature

 Another Bluetooth SIG initiative is the HDT (High Data Throughput) amendment, designed to enhance existing Bluetooth use cases and unlock new possibilities such as low-latency audio streaming and data transfer. As the name suggests, HDT introduces significantly higher data rates – up to 7.5 Mbps – enabled by high-order QAM modulation. This results in:

• Nearly 4× faster data transfer
• Up to a 4× increase in throughput
• Greater spectral efficiency
• Improved energy efficiency by optimizing radio usage and reducing re-transmissions
• Enhanced reliability with robust RF performance and forward error correction

These advancements make Bluetooth HDT a powerful enabler for next-generation wireless applications, especially in audio and real-time data environments.

HDT brings unique challenges to Bluetooth devices which now have to select components to support higher order modulations such as 16 QAM and still keep low development costs and power profiles. Test instruments measure RF performance, including error vector magnitude (EVM), frequency error and bit error. LitePoint partners with silicon vendors to help them characterize their device performance and participates in HDT interoperability testing organized by the Bluetooth SIG.

Bluetooth SIG Interoperability testing events help device manufacturers validate their designs throughout the product development cycle. This hands-on involvement ensures that Bluetooth devices comply with specifications and interoperate seamlessly with other certified devices, accelerating time to market and enhancing product reliability.

Unlocking New Bands, Unleashing New Possibilities

The universal appeal of Bluetooth Low Energy is due in part to the fact that it operates on over 40 channels in the unlicensed frequency band at 2.4 GHz, thus simplifying rollout around the world. But these frequencies are congested, with multiple other technologies jostling for space, which can lead to dropouts and glitches for Bluetooth users.

To support the continued evolution of Bluetooth technology, an initiative is underway to expand Bluetooth HDT operation into higher spectrum bands, including the unlicensed 5- and 6-GHz bands. This strategic expansion aims to unlock new levels of performance, enabling higher throughput, lower latency, improved accuracy and better coexistence with other wireless technologies. By leveraging these additional spectrum resources, Bluetooth is positioned to meet the growing demands of next-generation applications and maintain its role as a leading wireless connectivity standard well into the future.

Wireless Spectrum Worldwide

As Bluetooth expands into higher frequency bands, new challenges emerge for device manufacturers, particularly around channel access mechanisms and global regulatory compliance. Operating in the 5- and 6-GHz bands introduces complex coexistence and coordination requirements with other wireless technologies such as WLAN. Historically, Bluetooth operated solely in the 2.4-GHz band, and test equipment was designed accordingly. LitePoint is prepared for this evolution. Our instruments support frequencies up to 7.3 GHz, enabling comprehensive testing for next-generation Bluetooth devices and ensuring reliable performance in these newly adopted spectrum bands.

Even As It Matures, Bluetooth Continues to Innovate

Bluetooth has a detailed roadmap to enable new features such as channel sounding and HDT to improve user experiences, while future developments such as higher frequency bands will provide the technology needed for new use cases in the years ahead.

For all these developments, it’s essential to have accurate, robust test capabilities. LitePoint has the expertise to provide simpler, faster and better test outcomes for any Bluetooth device.