Why you should care about ultra-wideband - fine-grained location sensing isn’t just for lost luggage

Kurt Marko Profile picture for user kmarko October 11, 2019
What is ultra-wideband and why should you care anyway? Spoiler - there's an Apple angle...


Engineers have a timeless adage about standards: they’re great because there are so many to choose from. Standards come and go, and once abandoned for something new, few ever make a comeback more than a decade later, much less in an entirely different field, but that’s what’s happening to ultra-wideband (UWB) radio technology.

The story of how a technology initially developed as a wireless replacement for HDMI cables got resurrected as a mechanism for fine range location sensing and ended up in the latest iPhone 11 is interesting enough. However, more germane to enterprises are the recent advancements in UWB technology and industry alliances that open up numerous consumer and enterprise applications, particularly once the technology is on millions of phones and other devices.

What is UWB and what makes it different?

Unlike most wireless communication technologies, UWB operates over a large swath of radio spectrum, specifically 500 MHz or higher. In contrast, Wi-Fi and LTE radio bands are about one-tenth as wide, typically between 20 and 80 MHz. Taking such a huge chunk of spectrum requires UWB radios to have an extremely high base frequency, with the FCC authorizing UWB applications the unlicensed use of the range between 3.1 GHz and 10.6 GHz.


Source: What UWB Does; FiRa website.

The ultra wide band and high frequency also allow UWB to operate at very low power, however, the combination of high base frequency and low power limits the signal range, with typical implementations useful to about 10 meters. The wide bandwidth also means UWB has little interference with other RF sources, providing stable connectivity even in crowded radio environments. High frequencies also allow UWB devices to provide high positional accuracy, to within a few centimeters, by using techniques to precisely measure the transit time between UWB beacons and the reliever.

Operating over such short distances, paired with the ability to precisely calculate the distance between two devices adds a layer of security to UWB not present in other wireless technologies since, according to FiRa, a UWB industry group:

Any attempt to intercept and amplify the signal, during a relay attack, will only delay the arrival of the responding device’s acknowledgement signal, making it clear to the UWB-based lock that the responding device is actually farther away, not closer.


Source: How UWB Works; FiRa website.

As mentioned above, FiRa is an industry consortium designed to promote UWB applications and interoperability that is comprised of companies working with the technology. Its members are building a new generation of UWB devices and applications upon a foundation of the IEEE 802.15.4 standard for short-range, low-power wireless devices. fiRa's mission is to support relevant IEEE standards work to improve performance and define test methods while extending it with a standards certification program and application layer standards and APIs that are out of the IEEE's scope.

Many usage scenarios, but car access security the first test case

FiRa breaks the uses for UWB into three broad categories - hands-free access control, location-based services and peer-to-peer services — with applications across five markets, as shown in the following graphic. The first, access control, is an area of active development by UWB component makers and car companies, however, expect it to quickly spread to building security systems. FiRa describes the process of unlocking a door via UWB this way (emphasis added):

The identification process happens in an instant, and the door only unlocks if the user and the credential are both present and heading towards the door from the “outside”, so people without proper identification and clearance don’t gain entry. To make the setup more efficient, and prevent needless opening and closing, operation can be configured with various parameters such as not opening if you turn away from the door before you reach a certain point or if you simply stand within a certain distance of the door. UWB technology knows if you’re approaching or leaving, and understands what side of a door you’re on, so the lock and unlock functions happen at the right times, in response to your movements and positioning.


Source: FiRa website; UWB Use Cases

Although the possibilities of an ultra-low power technology for highly accurate positional sensing and secure short-range communications are many, component suppliers must first develop standards-compatible devices that developers in other industries can use to embed UWB in their products. This chicken-and-egg deadlock was broken earlier this year when chip vendor NXP Semiconductors used its developer conference to announce its entry into UWB sensors designed for industrial, mobile, automotive and smart infrastructure applications.

NXP’s technology preview was quickly followed by an agreement between the company and Volkswagen to develop a UWB security system that would use UWB to replace the low-band UHF transmitters in car key fobs. The VW system exploits the ability of UWB to provide highly-accurate position and movement information, using AI models to learn personalized user gestures and even walking patterns as security tokens. Over time, VW sees UWB being useful for other vehicle security and automation scenarios such as, “automated trailer hitch activation, in-cabin passenger detection, automated valet parking, hands-free parking, lot access and drive-through payment.” According to Maik Rohde, Volkswagen’s head of body electronics and car access:

The first UWB application we see is in theft protection – another security milestone which you will see in volume Volkswagen car models starting this year. But this is only the beginning. UWB, especially when combined with high-precision sensors and Artificial Intelligence, can deliver further benefits. Some of these you can experience in our concept car.

What’s Apple up to?

VW replacing their wireless key fobs with something more convenient and secure is one thing, but nothing raises the collective conscience of consumers and industry executives faster than Apple adopting a new technology. Thus, curiosity about UWB skyrocketed when Apple announced that it incorporated the technology in a proprietary U1 chip embedded in the three new iPhone 11 models. The company has been customarily coy about its intentions, with only a brief acknowledgment of the chip in its iPhone launch presentation and this statement on its product website:

Additional Features: The new Apple-designed U1 chip uses Ultra Wideband technology, the first ever in a smartphone, for spatial awareness. With iOS 13.1 coming on September 30, AirDrop gets even better with directionally aware suggestions.

Apple-watcher Jason Snell at SixColors explains the initial UWB application this way (emphasis added):

Right now, the only feature Apple has announced involving the U1 is a modified version of AirDrop that uses that precision location to determine if another iPhone 11 is close (and, believe it or not, if it’s pointing at your phone), and pops that device to the very top of your AirDrop interface. UWB can be used to transfer data at up to 27 megabits per second, which is faster than Bluetooth LE, but slower than Wi-Fi. I don’t know if Apple’s using UWB to do the data transfer or just using it for location finding and then switching to a peer-to-peer Wi-Fi connection for fast file transfers, which is what usually happens when using AirDrop between devices.

However, Apple doesn’t go to the expense of developing and embedding a new component in hundreds of millions of iPhones without some significant plans that justify the space in those space-starved devices. Earlier this year, there were abundant rumors of Apple using UWB in a Tile-like ID tag for highly accurate location tracking, however, there are several other applications in the FiRa taxonomy above that would be even more compelling in a phone, including:

  • Indoor mapping and navigation with much greater precision than GPS- or Bluetooth LE-based systems.
  • Smart home and vehicle access and control using a phone or Apple Watch (if, when Apple adds UWB to its Watch) to replace a key fob.
  • Augmented Reality that uses precise location and movement information in apps.
  • Mobile payments that are more secure than NFC by being resistant to eavesdropping attacks and able to define a precise, limited bubble around the payer’s location.

Whatever Apple ends up introducing, you can bet it will unleash a torrent of copycats jumping on the UWB bandwagon.

My take

UWB is the sort of infrastructure plumbing that won’t affect most organizations in the short term, but that could have fascinating and profitable applications over time. However, like most foundational infrastructure technologies, UWB isn’t the sort of thing that one can just drop into a product or business situation, but something that requires ample R&D and planning for development, implementation and system integration. That’s a long-winded way of saying that UWB should be on the technology watch list for retailers, manufacturers, healthcare providers and other organizations that might benefit from a secure wireless communication technology that also provides high-precision positional data and doesn’t interfere with other wireless systems.


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