UWB Enables Secure and High Precision Fine Ranging Localization
UWB (Ultra-Wideband) is defined in the IEEE standard 802.15.4. First deployed in the early 2000s, UWB (at the time marketed as WiMedia) was geared towards high-speed transmission USB replacement, but it never achieved wide commercial adoption. UWB has recently seen a renewed interest with the development of the 802.15.4z amendment. This amendment, updating the PHY and MAC layers of the technology is geared towards low data rate connectivity for high precision, secure ranging applications.
With high precision and secure fine ranging capabilities, UWB can be used to determine the distance between peer devices up to 200 m apart with centimeter-level of accuracy. UWB is uniquely suited for a wide range of applications requiring location such as secure hands-free access control (car key, mobile phone or badge), real-time indoor positioning (RTLS) or Location-Based Services for smart homes, smart factories, transportation or healthcare.
What is ToF?
UWB uses Time of Flight (ToF) to determine the distance between peers. ToF measures the propagation time that it takes for the RF signal to travel between the transmitter and receiver. This time measurement multiplied by the speed of light determines the distance with high accuracy. Compared to other technologies relying on measured signal strength to evaluate distance, UWB provides a higher degree of accuracy and security.
The ToF measurement process between UWB peers is called two way ranging (TWR), because peers exchange a series of request and response messages with embedded timestamps. The Round Trip Time (RTT) is used to determine the ToF as described in the graph to the right.
Two Way Ranging (TWR) between a UWB tag (mobile phone, keyfob, badge) and an anchor measures their relative distance, this method is used for example for secure access applications where access will be granted based on the proximity of the tag device.
With a UWB distributed anchor network in place, the TWR mechanism can be used for trilateration of the tag’s position for 2D or 3D absolute positioning, this method is used in RTLS applications.
Angle of Arrival (AoA) is an expanding option to measure the angle of an incoming signal using multiple antennas. Positions can be determined by having multiple angles, multiple distances or combinations hereof.
Thereby providing both distance and relative position.
Access technologies, like Bluetooth® or RFID, rely on measurement of signal strength to evaluate distance and can be subjected to relay/man-in-the-middle attacks. During a relay attack, the communication from the valid key is spoofed by amplifying its signal strength and tricking the receiver into believing that the key is nearby. Conversely UWB cannot be spoofed by a simple relay attack, as its distance measurement is not based on signal strength but on time. A relay/replay attack will add latency to the message transmission and therefore achieve the opposite effect, by indicating that the key is further away from the receiver.
At the PHY layer, the 802.15.4z amendment provides additional security to UWB by adding a set of pseudo-random pulses generated using AES-128 encryption. Only the sender and receiver can decode the packets with the share key, ensuring protection against relay attack.
UWB can achieve better than 10 cm positioning accuracy. Unlike other transmission technologies that also provide positioning, UWB uses a very wide channel width from 500 MHz to over 1 GHz with very short pulses (<2ns). Comparatively Bluetooth® uses 1 MHz channel width and Wi-Fi up to 160 MHz. The large channel width and short pulse make this technology immune to the multipath effects of signal propagation that narrowband signals are vulnerable to. Therefore, it is capable of providing high accuracy even in an environment with interference sources from reflection or refraction and makes it a great technology for deployment in residential or industrial environments.
How Do You Test UWB Devices?
For R&D, manufacturing or certification testing, UWB’s device testing includes compliance verification and performance validation.
The FiRa Consortium promotes the development and adoption of UWB secured fine ranging and positioning capabilities of interoperable UWB devices. A key component of this mission is ensured by the FiRa Certification Program. This program is designed to verify that candidate devices conform to the FiRa Consortium requirements and test specifications.
ToF Calibration and Verification
Successful deployments of UWB devices depend on the accuracy of their fine ranging capabilities. As a ± 100 ps error results in ToF measurement results in ± 3 cm position accuracy, it is easy to understand why particular care should be given in the calibration and verification of ToF measurements.
UWB (802.15.4) Measurement Specification
|Spectrum Mask||Transmit spectrum mask|
|Symbol Modulation Accuracy||Correlation to reference pulse (%)|
|Carrier Frequency Offset||Carrier frequency error (kHz)|
|Chip Clock Error||Error in ppm|
|Chip Frequency Error||Error in Hz|
|Pulse Main Lobe Width||Width of main lobe in time (ns)|
|Pulse Side Lobe Power||Power relative to main lobe (%)|
|Power (Preamble & Data)||Average power of complete data capture (dBm)|
|Pulse Jitter||Jitter in ps|
|Pulse NMSE||Normalized Mean Square Error (ppm)|
The next-gen, fully-integrated, one-box test solution for physical-layer testing of devices enabled with UWB technology. It’s ideal for both R&D characterization and high-volume production, making it the perfect platform to enable a cost-effective, seamless transition from the lab to production. IQgig-UWB+ is a complete UWB test solution.
With Integrated DUT and tester control IQfact+™ application software provides quick and reliable results for both calibration and verification. LitePoint works with the leading UWB chip manufacturers such as NXP and Qorvo/Decawave to provide a turnkey solution that integrates optimized test and calibration routines.
As the first test equipment vendor to join the FiRa™ Consortium, LitePoint is committed to ensuring seamless UWB Fine Ranging end-user experiences by contributing to standards and certification programs to foster interoperability.