College Researchers Have Developed A More Precise UWB

Published: February 6, 2024

XRLoc is aimed at gaming, augmented reality and other immersive experiences in which the location and orientation information is key

A group of researchers at University of California San Diego and Osaka University have developed a localization technology that boasts greater accuracy than standard ultra-wideband (UWB) systems, even with a single anchor device.

The solution employs both UWB and LoRa transmissions to help coordinate multiple tag reads and save energy. The team released a white paper regarding this system—they call it XRLoc—which they say provides location accuracy of a few centimeters or less.

The technology could be used in extended reality (XR) applications such as gaming as well as augmented- and mixed-reality systems for immersive, interactive and realistic user experiences, says Dinesh Bharadia, UCSD professor in the Department of Electrical and Computer Engineering at the Jacobs School of Engineering.

The goal is to provide highly granular location data with a fraction of the infrastructure requirements of other real-time locating (RTLS) solutions, says Bharadia.

Limits of Traditional UWB

Traditional UWB systems require multiple anchors (or readers) installed around an area such as warehouse or public area to identify location of UWB tags.

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Such installations tend to be expensive and bulky to integrate into products such as consumer electronics, according to Bharadia, which has resulted in limited deployments.

XRLoc, on the other hand, consists of a localization tag which is attached to objects or people being tracked, detected by just one localization anchor.

Under the Hood

The anchor consists of six Decawave DW1000 UWB modules and a Semtech LoRa SX1272 radio. The anchor then interacts with an UWB and LoRa based tag by transmitting and receiving over both frequencies.

The system works by measuring the difference of the received ultra-wideband signals between a tag and multiple antennas.

As the tag’s signal travels, it reaches each antenna within the reader at a slightly different phase and time. The system combines these differences to accurately measure the tag’s location in 2D space.

The system includes a particle filter, used to overcome innate distance-sensitive measurement biases that are part of UWB systems.

With the particle filter, Bharadia says, “We can sample our environment more sparsely and slowly converge to our ideal location over a few packets.”

LoRa Combined with UWB

The use of LoRa transmission in conjunction with UWB helps further coordinate multiple tags and saves energy.

When multiple tags transmit UWB signals to the same XRLoc modules simultaneous or overlapping transmissions from two tags can corrupt the read data, explains Bharadia. To address this, the anchor device is designed to transmit beacons of LoRa signals in a time-interleaved manner in which each tag is given a specific time slot to transmit within.

By coordinating multiple tags, the system saves transmission energy over the lifetime of the tag because it only transmits within its assigned time slots.

During testing, the researchers found that with six, five and four antennas, they gained corresponding median location accuracy of 4.7, 6.9 and 28.7 centimeters.

Extended Reality

For tasks such as gaming or virtual reality applications, the technology can help generate a virtual representation of tagged objects including their position and movement. Applications could then range from enhancing virtual gaming experiences to improving workplace safety, according to Bharadia.

In the lab, the researchers used their system to play a life-size chess game with mugs, retrofitted with off-the-shelf UWB tags, transforming each mug into a virtual chess piece.

As the pieces were moved around a plain, unmarked table, the system was able to track their movements in real-time with centimeter-level accuracy. The software then displayed the actions for users wearing virtual reality headsets, as chess game pieces of a chess board.

Binaural Audio

The technology could help those listening to music, watching a program or engaging in a conversation over their laptop or mobile device, the researchers predict.

Binaural audio consists of an immersive sound experienced by an individual based on their location. In this case, the system knows the exact location and orientation of an individual and the sound is adjusted according to UWB responses from tags.

These UWB (and LoRa) based tags could be built into the headphones or smart glasses to identify not only exactly where the individual is, but the orientation of their head as they listen, and even move around a room.

By identifying the location of a user’s ears, a system would automatically adjust the volume and timing to simulate the way the user would naturally hear it. The sound could be played through a pair of headphones, accordingly.

“Imagine you are in an environment in which there are three people who want to watch three different things or listen to three different songs. You beamform [focus the transmission toward the receiving device directional audio to each of those three people,” Bharadia said.

Ease of Installation

Bharadia and his team have been talking to technology companies to begin piloting or adopting the technology for a variety of use cases.

The group is now working on creating a demo of that smart speaker that will further highlight the possibilities.

In the coming years, Bharadia predicts the reader devices will be integrated within TVs or connected to laptops. Even in public places, he says, the system could locate a user, then deliver a laptop’s audio in a natural way without requiring headphones—if the user has UWB in their glasses.

Key Takeaways:
  • Academic research leads to UWB accuracy at the sub-centimeter level.
  • The technology, developed at the University of California, San Diego (UCSD) could enable a variety of virtual reality and audio precision-based solutions for those with smart glasses or similar devices.