Ultra-Precise Synchronization for TDoA-based Localization Using Signals of Opportunity

Precise localization is one key element of the Internet of Things (IoT). Especially concepts for position estimation when Global Navigation Satellite Systems (GNSS) are unavailable have moved into the focus. One crucial component for localization systems in general and precise runtime-based position...

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Bibliographic Details
Published in:arXiv.org 2023-06
Main Authors: Maul, Thomas, Klob, Sebastian, Joerg, Robert
Format: Article
Language:English
Subjects:
Algorithms
Carrier frequencies
Clock synchronization
Cramer-Rao bounds
Cross correlation
Estimates
Frequency synchronization
Global navigation satellite system
Internet of Things
Localization
Lower bounds
Run time (computers)
Time synchronization
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Summary:Precise localization is one key element of the Internet of Things (IoT). Especially concepts for position estimation when Global Navigation Satellite Systems (GNSS) are unavailable have moved into the focus. One crucial component for localization systems in general and precise runtime-based positioning, in particular, is the necessity of ultra-precise clock synchronization between the receiving base stations. Our work presents a software-based approach for the wireless synchronization of spatially separated base stations using a low-cost off-the-shelf frontend architecture. The proposed system estimates the time synchronization, sampling clock offset, and carrier frequency offset using broadcast signals as Signals of Opportunity. In this paper, we derive the theoretical lower bound for the estimation variance according to the Modified Cramer-Rao Bound. We show that a theoretical time synchronization accuracy in the range of ps and a frequency synchronization precision in the range of milli-Hertz is achievable. An algorithm is presented that estimates the desired parameter based on evaluating the Cross-Correlation Function between base stations. Initial measurements are conducted in a real-world environment. It is shown that the presented estimator nearly reaches the theoretical bound within a time and frequency synchronization accuracy of down to 200 ps and 6 mHz, respectively.
ISSN:2331-8422