High-Precision Ranging Matters: Uncovering the Potential of Ultra-Wideband Radios in Real-World Applications
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Cao, Yifeng
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Abstract
Ultra-wideband (UWB) radio is an upcoming wireless technology characterized by an extremely large bandwidth (> 500MHz). Such a wide band enables UWB to perform ranging in decimeter-level accuracy, making it a superior option for accurate localization. The recent incorporation of UWB in mobile devices like iPhones, Samsung smartphones and AirTags has demonstrated its feasibility in medium-range positioning. However, we believe the potential of UWB is still under-explored even in today's market for three reasons. First, accurate ranging measurement is an important modality in extensive sensing applications beyond localization, including physical distancing, human action recognition, autonomous parking, etc. Merely using UWB for object positioning ignores the vast possibilities to apply UWB in the general mobile computing field. Second, most current use cases of UWB focus on the baseband. The potential of UWB's carrier wave, and particularly its phase, has not been exploited. Third, as a radio technology working on an independent band, UWB does not interfere with other widely used wireless technologies, including Wi-Fi, Bluetooth, etc.
The objective of this dissertation is to explore and extend the possibilities of UWB, enabling various applications. Our exploration demonstrates that introducing UWB can both achieve better performance in solving a problem which is traditionally tackled by other technologies, and open the gates to new applications. We proposed UWB's applications in four areas in this dissertation. In the first work 6Fit-a-Part, we use UWB to achieve accurate and real-time physical distancing using a custom wearable device. More specifically, we design a one-to-all ranging protocol that is able to accurately estimate the distance to neighboring devices and warn the user if the distance falls below a certain established threshold within a short time. This work still employs UWB's fundamental ranging capabilities, but targets a more challenging dynamic, multi-user ranging scenario. Our second work ITrackU goes one step further to answer the question whether UWB can be used to perform high-precision tracking. In this work, we present a system that enables millimeter-level tracking of a pen-like instrument across a large surface by fusing UWB with inertial sensors (IMU). The core idea that permits mm-level tracking is to use UWB carrier phase captured from multiple vantage points. Fusing the phase measurements with IMU offers the ability to perform continuous tracking despite wireless occlusions. Continuing on the UWB-IMU fusion approach, the third work ViSig extends the use of UWB to human action recognition with wearable devices. In this work, UWB primarily provides inter-appendage distance measurements while IMU captures the angles (or orientation) of different body segments. The results show that by deploying only a small number of sensors (6) on the body, we can achieve >90% accuracy in interpreting various body signal applications such as cricket umpire signals, baseball umpire signals, crane signals, flag semaphore, and football official signals. Finally, in the fourth work, we show UWB can even be applied in the online authentication field, where the location of a token close to the login device is an important consideration. We present a UWB-based two-factor authentication (2FA) platform, called UWB-Auth, designed as carriable or wearable devices, which eliminates various social engineering attacks including phishing attack, 2FA-fatigue attack, co-located attack, etc, while maintaining short authentication. The evaluation with our custom prototype shows UWB-Auth completes the whole authentication process in 4 seconds, and completely rejects malicious requests when the adversary is 20cm and 10 degrees outside a small valid physical area near the login device. Overall, we have significantly expanded the application space for UWB beyond the traditional indoor localization and lost-and-found use cases. In doing so, we have made algorithmic and architectural innovations which are expected to become cornerstones in future research around UWB.
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Date
2024-04-15
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Dissertation