Various technologies blossomed: How the combination of ultra-wideband and low-power Bluetooth can achieve innovation

More and more of our everyday digital devices, including smartphones, door locks, and even the latest cars, now use a wireless capability called spatial awareness. A digital device with spatial awareness can understand where it is relative to other devices and then respond to changes in the positions of those devices. Spatial awareness makes it easier for us, the users of these digital devices, to get through our days.

Take a spatially aware door lock, for example. This lock, which could be installed on a car door, warehouse entrance, or front door, senses the approach of the smartphone you are carrying and automatically unlocks when you are close enough to enter. Similarly, the door lock can sense your departure and automatically relock when you are far enough away to indicate that you have left.

Another way spatial awareness can help us humans is by finding things we have misplaced. You can attach a small tracking device to your wallet, glasses, or remote control, and the next time you can’t find the item, your smartphone can use its spatial awareness to locate it and guide you to it. Your smartphone can even present an image with an augmented reality view on the screen to guide you to the lost object.

Interacting with spatially aware devices is simple and intuitive, but designing a human-machine experience that supports spatial awareness can be quite challenging because there are many steps involved. In addition, developers have discovered that using two different wireless technologies, Bluetooth low energy and ultra-wideband, can create an enhanced solution for spatial awareness.

The Bluetooth Low Energy (BLE) portion of the design provides a low-power method to identify the presence of other devices through passive proximity detection. The ultra-wideband (UWB) portion of the design provides precise positioning capabilities based on wideband ranging, which can detect small changes in distance and direction of movement. After detecting a nearby object, the BLE side of the design triggers the UWB side and uses the data generated by the UWB to communicate the location and direction of movement to the human-machine interface.

Implementing these interactions between BLE, UWB, and human-machine interfaces can be tricky. It involves complex embedded algorithms and sophisticated RF design. In addition, the end product requires thorough testing to ensure that the two wireless technologies can work together seamlessly.

Here are some things developers need to consider when using spatial awareness.

Proximity sensing and communication via Bluetooth Low Energy (BLE)

Because of its widespread use, Bluetooth is a logical choice for IoT devices. According to the 2021 Market Update from the Bluetooth Special Interest Group (SIG), the standards organization that oversees Bluetooth specifications and licensing, an estimated 13 billion Bluetooth-enabled IoT devices are already in use. The Bluetooth SIG has played a major role in the success of BLE because they not only define the communication protocol, but also enforce compliance through a certification program. The result is that BLE is ubiquitous and universally interoperable. Developers can be confident that BLE-enabled devices will be able to communicate with other BLE-enabled devices they encounter, and end users don't have to worry about device setup and configuration.

Interoperability makes BLE an excellent choice for short-distance data transmission between two points. In applications using spatial awareness, this means BLE can be used for configuration, link negotiation, and communication human-machine interfaces.

BLE can also be used for positioning, but it is not as accurate as UWB in determining the exact location of an item. BLE uses a technology called Received Signal Strength Indicator (RSSI) to calculate distance. This is the same technology used by other popular positioning protocols, including Wi-Fi. RSSI measurement uses signal strength to indicate distance, which is based on the idea that the closer the signal, the stronger it is, but this method is more susceptible to problems such as RF interference and human obstruction. If the application needs to go beyond BLE's level of spatial awareness, then UWB comes into play.

Precise positioning through ultra-wideband (UWB)

UWB, recently defined by the IEEE in 802.15.4a/z, is a wireless standard that provides more accurate readings than any other positioning technology currently in use, including BLE and Wi-Fi. Using time-of-flight (ToF) and angle-of-arrival (AoA) calculations, UWB can accurately determine location to within +/-10cm.

The latest version of UWB is based on military radar applications. It differs from other wireless protocols in that it uses pulse signals as short as 2ns. Also, unlike the narrowband in the more crowded 2.4 GHz spectrum where BLE, Wi-Fi and some proprietary solutions operate, UWB uses a wide bandwidth of 500 MHz in the 6-8 GHz spectrum.

UWB’s unique structure means it can accurately perform secure ranging while using very little power to send signals, providing a very stable connection with little interference, even in challenging RF environments.

A winning combination

The combination of BLE and UWB positioning benefits a wide range of use cases including smart home, automotive, consumer and industrial.

Going back to the door lock example, the car door automatically opens when you approach it, which is the best experience provided by BLE and UWB. BLE can perform initial discovery at the adjacent external boundary, and then coordinate with multiple anchor points around the car body to activate UWB ranging. The newly activated UWB anchor can detect the corresponding UWB radio in the smartphone. Using coordinated ToF and AoA measurements, these UWB radios can ensure highly accurate distance measurements.

A similar handoff between BLE and UWB happens in an item tracker. A small, battery-powered tag can be attached to a bag, car keys, a pet's collar, or anything else you might lose. BLE associates the tracker with your phone. Pairing the two BLE endpoints enables encrypted BLE communications for privacy. Later, when you can't find what you're looking for, you can initiate a search using an app on your phone. BLE looks for relevant tags, and once in close proximity, BLE activates UWB ranging, and your app guides you to the exact location of the lost item.

Meeting the design challenge

The combination of BLE and UWB means that each protocol can provide key features to create a better user experience. However, developing a design from concept to product using the combined wireless technologies presents unique challenges to developers.

Coding firmware and designing hardware to realize the full combined potential of BLE and UWB requires expertise in each technology. In addition, understanding how the two technologies can be integrated together in a system means paying attention to many other factors, including non-volatile memory and RAM limitations, system-level current consumption budgets, and board design constraints.

The benefits of using the same supplier

Designers need to rely on reliable and easy-to-integrate BLE and UWB solutions that can ideally work in conjunction with each other in a single system. One way to ensure that BLE and UWB ICs can be successfully integrated into a product is to work with a single supplier that can provide both ICs.

For example, NXP offers BLE and UWB system-on-chip (SoC) options for space-constrained designs, and pre-certified PCB module variants of BLE and UWB solutions through module partners. In addition, designing hardware with NXP's reference designs and design guides puts system developers in a leading position and ensures that customer boards are designed to meet optimal RF and other performance metrics.

Combining BLE and UWB software in a single project also presents its own set of challenges. This is another situation where choosing a single vendor can help, as you are more likely to find software components that work together. For example, NXP's MCUXpresso SDK provides pre-integrated UWB drivers, BLE stacks, other key system components (such as bootloaders), and application layer functions, demonstrating UWB-driven use cases in a set of reference examples.

NXP's Finder V3 reference board serves as an additional design tool, providing best hardware design guidelines and tightly integrated embedded software. This reference design demonstrates the use case of Finder, including a small battery-powered board that supports BLE proximity and discovery, UWB ranging, and even a demonstration mobile application with source code.

The Finder V3 reference design is based on the QN9090 wireless MCU and Trimension SR040, NXP’s UWB solution tailored for UWB tracking applications. The Trimension SR040 supports time difference of arrival (TDoA) in real-time location service (RTLS) tags and is designed to meet the upcoming requirements of the FiRa Consortium for UWB.

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By leveraging the complementary characteristics of BLE and UWB, developers can unlock innovative user experiences and help make our connected world more seamless and reliable.

To learn more about how NXP makes BLE and UWB work better together, check out the many optimizations included in our UWB Development Kit.

author :

Parker Dorris Automotive BLE Product Manager, NXP

Parker Dorris is a product manager for NXP's automotive BLE products. In addition, he helps manage NXP's connected product software, focusing on ease of use and some third-party ecosystem collaboration. Parker has more than 15 years of experience as a firmware developer and marketing manager for microcontrollers and wireless technologies.