Bluetooth: New Specifications and New Capabilities

March 18, 2025

Blog

Bluetooth: Past and Present

The Bluetooth name, logo, and core capabilities have been around for decades, becoming almost ubiquitous in the world of wireless communication. Even among the non-tech-savvy, Bluetooth permeates life in the modern world. From cell phones to smart watches, tablets, laptops, headphones, and everything in between, the past and current iterations of Bluetooth are unavoidable

Figure 1. Applications of Bluetooth technology (source: Bluetooth SIG)

The next evolution of Bluetooth will enable so much more in an ever-changing and connected world. As devices become more intelligent and better connected, the demand placed on wireless technologies is in turn, continuing to rise. If the current rate of development follows the same trajectory as in recent decades, the demand for better and more reliable wireless capabilities will only continue.

As a result, the Bluetooth specification is also evolving and introducing several significant changes. With some exciting new technologies set to enable many more applications, Bluetooth could become even more critical in an increasingly modern and wireless world.

Bluetooth New Features

The Bluetooth specification is undergoing several significant changes that will drive new products and test requirements, including Channel Sounding (CS), Higher Data Throughput (HDT), and Higher Frequency Bands. These are new technologies that will enable Bluetooth to be much more practical in new applications and verticals, such as asset localization and high-resolution audio.

Channel Sounding

Distance measurements in Bluetooth have traditionally been based on the Received Signal Strength Indicator (RSSI), a method that estimates the distance between two devices by measuring the relative power of a received signal. While this approach is easy to implement and provides a rough distance estimate, it has limitations—it’s prone to interference and is susceptible to man-in-the-middle attacks. It lacks the precision required by modern applications, with an accuracy of just 3 to 5 meters.

Bluetooth Channel Sounding represents a significant improvement, offering enhanced accuracy and security in distance measurements. This new feature leverages a combination of phase-based ranging and time-of-flight measurements to deliver distance accuracy down to tens of centimeters with enhanced security. Such precision is crucial for applications like automotive digital keys, where a vehicle must accurately detect when its owner is nearby or inside, while also preventing unauthorized access.

The Bluetooth Channel Sounding feature defines two device roles: an Initiator and a Reflector. Both devices must have a Bluetooth LE Controller that supports the Bluetooth Channel Sounding feature, and either device can kick off a Bluetooth Channel Sounding procedure.

Figure 2. Bluetooth Channel Sounding applications in the Bluetooth stack, occurring between an Initiator and Reflector

The new method for securely measuring distance involves a combination of Round Trip Time (RTT) and Phase-Based Ranging (PBR). While not new in wireless communications, these present a new capability that will be necessary for the development of Bluetooth-enabled devices. To ensure Bluetooth LE devices can perform a channel-sounding procedure, new physical-layer measurements are necessary, including power ramp, clock drift estimation, phase measurements, etc..

The inclusion of Channel Sounding presents a differentiated development for Bluetooth in the world of wireless communications. Potential applications for Bluetooth Channel Sounding capabilities are asset localization, real-time location services, digital keys, proximity detection, and more.

While these applications are an exciting new prospect for Bluetooth, they do come with technical challenges. Phase, synchronization, and timing will all require more attention in the development and testing.

Higher Data Throughput (HDT)

As the name implies, Higher Data Throughput enables higher data rates by utilizing higher-order modulation schemes up to 16-QAM.

 

Table 1. Bluetooth HDT Data Rates

Figure 3. Bluetooth Modulation Schemes

Higher-order modulation schemes come with the benefit of an increase in the number of transmitted bits per symbol and higher data throughput; however, this also stresses the receiver sensitivity as there are much smaller decision areas for each constellation point. Bluetooth wireless systems using 16-QAM must perform better to ensure high accuracy and maintain a sufficiently low BER.  As a result, stricter EVM measurements will be required during testing.

While still not on the level of Wi-Fi or cellular EVM requirements, this nonetheless presents a new challenge and may stress the capabilities of Bluetooth test systems.

 

Table 2. Proposed EVM limits of Bluetooth for Various Data Rates

Higher Frequency Bands

Traditionally, Bluetooth has operated in the 2.4 GHz ISM band. Up until now, these frequencies have been more than sufficient for the technical requirements of the standard.

Figure 4. Spectrum Use for Various Wireless Standards

However, the 2.4 GHz band has limited bandwidth and is used by several other wireless standards. Utilizing additional, higher-frequency bands not only opens up additional spectrum but also improves the latency and speed of the transmission, making it more applicable for applications like high-resolution audio and data streaming.

Of course, this will not come without new development challenges, such as the need for instrumentation to cover additional frequencies, and coexistence testing and coordination with Wi-Fi and cellular standards that operate in channels adjacent to those proposed for Bluetooth use.

New Applications

New applications for Bluetooth have been alluded to throughout the discussion of their new enabling technologies. These technologies are necessary to make Bluetooth a viable alternative in areas like high-resolution audio and asset localization.

Asset localization, in particular, seems to be of significant interest to the wireless industry. With its new channel-sounding capabilities, Bluetooth has the potential to be used in areas where it was not previously viable, due to poor location accuracy.

An increase in potential applications also means an increase in demand. In the past, a large part of Bluetooth’s appeal has been its simplicity, ease of development, and fast time-to-market. For this to be the case with new HDT and CS capabilities, tests must play a key role in faster time-to-market, lowering cost, and gaining valuable insights from data.

Test Implications

While all these new developments present many benefits and potential new applications for the Bluetooth standard, they inevitably present new challenges in the development (and test) of new devices.

Additionally, one of the key differentiators in the use of Bluetooth is its simplicity, and in turn, lower overall cost to develop and manufacture devices. This has no doubt contributed to the vast quantity of devices utilizing Bluetooth. Keeping costs low, and time-to-market fast, is critical in a segment of the wireless world that has come to expect fast releases of new, low-cost devices. Addressing new developmental challenges, while keeping costs low, can be partially addressed by improved efficiency in test, both with instrumentation and test methodology.

Some of the test challenges associated with the technological developments discussed in this article include:

• EVM limit: a crucial measure of the overall performance of an RF transmitter, EVM limits are much lower with HDT, meaning test instrumentation must follow suit.
• Frequency range: Transitioning from the 2.4 GHz range to 5/6 GHz may not seem like a big leap in the context of the rest of the wireless world, but for dedicated Bluetooth test instruments, this presents a significant change that could increase costs and change test methodologies by adding new test cases.
• Better synchronization: There are multiple challenges with Channel sounding such as real-time frame exchanges, phase coherency, time accuracy, and frequency hopping. This adds an increased emphasis on timing and synchronization, due to the new methodologies with which distance is measured. If measurements such as RTT and PBR include synchronization with DC or digital instrumentation, this need is even more pronounced.
• More measurement types: HDT and especially channel sounding will likely present many more test cases throughout the development process of new devices. Especially in validation, as all parameters are swept and iterated across all possible scenarios.
• Scalability and futureproofing: Wireless devices are often enabled with not just Bluetooth, but Wi-Fi, other IoT, and cellular capabilities. A hardware and software platform able to accommodate all these requirements can provide a differentiated advantage for test and development.
• Coexistence testing and coordination with Wi-Fi/other wireless standards: operation in new frequency ranges means coexistence with adjacent channels that previously were not a concern.

Conclusion

The changes to the Bluetooth specification discussed in this article are substantial, but not unprecedented in the wireless world. This continues a long-standing trend of a world with more devices and better connectivity. Despite this, new challenges to the design and development of future Bluetooth-enabled devices are set to change test methodology and impact design cycles.

It is also worth noting that older iterations of Bluetooth will likely be with us for the foreseeable future. Many devices will continue to support both Bluetooth Classic and Bluetooth LE and may choose not to support the newer HDT or channel-sounding physical layers.

While challenges are expected, there is also opportunity. Bluetooth can pave the way for new IoT use cases, even with the added challenges that HDT and CS will introduce. With proper tools in place, and with proper consideration of design and development changes, Bluetooth can continue to be a simple, low-cost, and ubiquitous technology, accessible to billions worldwide.

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Alejandro Escobar is an RF product marketing engineer at Emerson Test & Measurement, helping test and validation engineers understand the value of efficient, scalable, and technically capable RF test solutions to help improve time-to-market, reduce test overhead, and draw meaningful insights from test data. He holds a B.Sc. in Mechanical Engineering from Texas A&M University. 

Jake Harnack is a principal product manager at Emerson Test & Measurement, currently focused on application and driver software that tests wireless standards such as Wi-Fi, Bluetooth, and 5G NR. He holds a B.Sc. in Mechanical Engineering from Kansas State University.