The operating concept is simple. Once a device that is equipped with a UWB radio such as a smartphone, wristband, or smart key comes into range of another UWB device, the devices start ranging. The ranging is done by performing Time of Flight (ToF) measurements between the devices. The TOF is calculated by measuring the roundtrip time of challenge/response packets. Depending on the type of the application (e.g. in case of asset tracking, device localization), either the mobile or the fixed UWB device calculates the precise location of the device. In the case where the device is running an indoor navigation service, it is required to know its relative location to the fixed UWB anchors and calculate its position on the area map.
UWB uses very large channel bandwidth (500 MHz) with short pulses of about 2 ns each; this helps achieve centimeter accuracy. The UWB positioning process happens in an instant, so the mobile device’s movements can be tracked very accurately in real time.
The FiRa Consortium supports the 500 MHz band in the Channel 5 to Channel 14 range. As Channel 9 offers the greatest worldwide regulatory acceptance, it is the only channel for which support is considered to be mandatory across FiRa Certified™ devices.
UWB-Enabled Devices Understand Motion and Relative Position
The real-time accuracy of UWB measurements means a UWB-enabled system can know, with a very high degree of certainty, the precise location of a device and whether it’s stationary or moving toward or away from a given object. For example, a UWB-enabled system can sense if you’re moving toward a locked door and it can know if you’re on the inside or outside of the doorway, to determine if the lock should remain closed or open when you reach a certain point.
The precise accuracy of UWB ranging allows the use cases to define the exact intent range to avoid false triggering. For example, if you live in a house with an attached garage, the UWB-enabled system can be configured to know when your car approaches that it is time to open the garage door so you can park your car when you come home from shopping. Or that it is time to unlock the entryway from the garage to the kitchen so you can bring in your groceries.
UWB Delivers Higher Security
Today’s technologies for ranging primarily rely on signal strength to determine distance and location. They measure the device’s signal strength and assume a strong signal means the device is close by. Attackers have found a way to trick these systems, using what’s called a relay station attack. In this type of attack, the legitimate wireless signals used to unlock a door are intercepted and amplified, causing the door to open even though the key isn’t close by.
What’s missing in these approaches is the precise calculation of actual physical distance, and this is exactly what UWB brings to the application. With UWB, 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. Any UWB signal that attackers succeed in intercepting and boosting won’t trick a UWB-equipped lock into opening. Moreover, the extension of IEEE 802.15.4z adds PHY level protection to all known attacks on legacy UWB radio.