The decades-old technology takes on a new life by providing location precision to 10 cm, and it operates indoors.

Ultra-Wideband (UWB) — a decades-old wireless technology for high-data-rate communication — has been reborn as a precise, secure, real-time technology for localization. IEEE and the recently established FiRa Consortium guide this rebirth, with specifications that create a foundation for using UWB to develop secure, interoperable, and state-of-the-art capabilities. Examples include hands-free access control, location-based services, and peer-to-peer communication use formats that safely coexist and complement today’s most popular wireless technologies, including satellite navigation, Wi-Fi, and Bluetooth.

From high-speed comms to secure ranging
Originally considered for use in radar applications in the 1960s, UWB was later adapted for use as an Orthogonal Frequency-Division Multiplexing (OFDM) technology (standardized in IEEE 802.15.3) as an ultra-high data rate transfer technology of up to 480 Mbps at close range. The expectation was that UWB would deliver the high-data-rate communication needed for digital home applications, but 802.11 Wi-Fi, with its longer range and higher data rates, ultimately triumphed and UWB essentially went away.

In recent years, however, UWB has re-emerged as a highly accurate, highly precise, secure approach to location and ranging. This newly transformed UWB technology uses impulse radio signals to find the relative position of peer devices with a very high degree of accuracy and can operate with Line of Sight (LoS) at up to 200 m under ideal conditions. The use of the wideband spectrum means UWB uses little power to send signals and provides stable connectivity, with little to no interference.

IEEE has standardized the new UWB format in 802.15.4, with additional work by the FiRa Consortium, a member-driven organization dedicated to the development and widespread adoption of interoperable UWB technologies.

Wireless co-existence with enhanced performance
UWB can operate from 3.1 GHz to 10.6 GHz, as defined by FCC. UWB won’t replace the wireless technologies used today for location services. Instead, it can be used to enhance location identification by delivering more precise readings than any other technology currently in use. Compared to Wi-Fi and Bluetooth, which can narrow an item’s location to within an area of about 150 cm, UWB has a location accuracy of 10 cm, and requires fewer anchors to cover the same area. Also, UWB can provide this high level of accuracy indoors, where GPS has difficulty operating, for extended navigational capabilities. Figure 1 highlights some of the new UWB characteristics.

UWB’s unique pulse signal makes it so accurate and precise. The very fast transmission of steep and narrow pulses, refreshed at a rate of 200 to 1000 times per second, make it possible to mark signal timing with a higher degree of certainty, so the usual Time of Flight (ToF) and Angle of Arrival (AoA) calculations, used for decades by location and ranging applications, produce more exact results that with other technologies (Figure 2).

Another feature of UWB is that the pulses resist a common difficulty, known as the multipath effect, which is what happens when radio signals reach the receiver by more than one path, due to reflection or refraction caused by natural or manmade objects close to the main signal path. Immunity to multipath further provides positioning accuracy, considering that inaccuracy is also caused by multipath effects. Immunity to narrowband fading and jamming helps make UWB a very robust technology option, too.

Recent work in standardization
The basis for UWB as a localization technology is IEEE standard 802.15.4. An important addition to UWB, defined in the 802.15.4z specification, is an extra portion of the physical layer (PHY) used to send and receive packets of data. The new feature adds cryptography, random number generation, and other techniques that make it harder for an external attacker to manipulate UWB communications.

IEEE 802.15.4 is a broad standard that defines different PHYs for devices operating in various license-free brands in various geographic regions. For UWB specifically, IEEE 802.15.4 provides definitions for the PHY layer, the MAC layer (which is a sub-layer of the Data Link layer), and a number of other sublayers (Figure 3). Before anyone implementing a real-world UWB IC could use the standard, however, several key operating characteristics needed refinement and optimization. The FiRa Consortium took on this task, with a focus of defining the details of UWB to ensure an interoperable ecosystem across chipsets, devices, and services infrastructures.

After a year of concentrated effort by internal working groups, the FiRa Consortium has released their first technical requirement specifications for the UWB PHY and MAC layers. Both specifications are based on the High Rate Pulse (HRP) portion of the IEEE 802.15.4-2015 technical specification and 802.15.4z/D8 draft amendment for fine-ranging UWB technology. According to the FiRa Consortium, the UWB MAC Technical Requirements defines elements such as how ranging protocol works, types of ranging that are supported, the parameters and format of the messages that are exchanged, and how ranging messages are encrypted. Similarly, the FiRa Consortium PHY Technical Requirements Specification document leverages select portions of the IEEE specification to facilitate interoperability between FiRa Consortium Certified UWB-enabled products. The new specifications will serve as the foundation for the FiRa Consortium’s upcoming certification program.

New use cases
UWB’s unique combination of signal characteristics — easy to identify, resistant to noise and reflection, separate from other signals — makes it an excellent choice for measuring distance and addressing a wide range of compelling new use cases.

The arrival of a detailed UWB specification, which includes dedicated security mechanisms and is designed for interoperability, means engineers can confidently begin work developing these new capabilities. Also, smartphone manufacturers and other makers of mobile devices are beginning to integrate UWB into their products. This helps widen the infrastructure for UWB services and build momentum for UWB features.

UWB will enable intuitive systems that blend seamlessly into daily routines. Hands-free access control will make it more secure and more intuitive to unlock doors and enter buildings. GPS-style location services, delivered indoors, will make it easier to navigate large spaces like shopping malls, educational campuses, and healthcare facilities. Device-to-device communication will enable smarter mobility in home, retail, and enterprise applications (Figure 4).

UWB shows promise in automotive applications, where manufacturers are already demonstrating cars with UWB features. VW has demoed UWB-access to cars based on a UWB-enabled car key. BMW presented mobile car access with UWB November 2019 (Figure 5). The lock on a car door can recognize your movements and unlock automatically, as you approach, while effectively resisting the relay attacks that cause issues in present-day smart-key designs. The Car Connectivity Consortium (CCC) serves as standardization body for such car access solutions. The CCC’s website has outlined the enablement of handsfree smart car access in its CCC Release 3, which specifies Secure digital key management, automotive BLE for communication and UWB technology for precise and secure localization. These supplements are set up to further develop the opportunities for smart device makers and vehicle manufacturers to enhance the evolving digital lifestyle.

Big OEMs and bodies like the FiRa Consortium carefully assess and test UWB’s abilities to function on large scale in a variety of use cases. Standardization work opens the field for a wide set of use cases.

Charles Dachs is the general manager and vice president of Secure Embedded Transactions at NXP Semiconductors. Previously, he worked with Philips Semiconductors, Philips Research, and CERN.