A Deferred Synchronization Method to Enhance UWB-TDOA Positioning Accuracy

Ultra-wideband (UWB) positioning, utilizing the time difference of arrival (TDOA) technique, is renowned for its high positioning update rates and centimeter-level accuracy in Internet of Things (IoT) scenarios, such as smart living and smart production. However, achieving such precision requires nanosecond-level synchronization accuracy in UWB network anchors. Inspired by the primary source of synchronization errors—unpredictable future clock deviations—this article introduces a novel deferred+3S-KF wireless clock synchronization (WCS) method. It departs from conventional methods, which attempt to better predict future clock deviations. Instead, to obtain a more accurate estimate of clock deviation parameters during the tag message arrival period, the calculation for mapping arrival times is deferred until the next clock correction package (CCP) arrives. In this way, with just tens of milliseconds of real-time positioning performance sacrificed, it allows for obtaining minimal measurement uncertainty of the first-order clock deviation parameters of the period (100–150 ps, corresponding to DWM1000 timestamp accuracy). The 3-Stage Kalman filter (3S-KF)-based WCS model is employed in this method to achieve more precise clock deviation tracking and accurate time mapping. Compared to the conventional 3S-KF WCS method, the experimental results demonstrate that our proposed unidirectional (CCPs are only broadcast by the reference anchor, with no response required) deferred+3S-KF WCS method can reduce the static positioning accuracy STD.V by 27.1%, achieving 5.82 cm STD.V, 6.44 cm RMSE, and 9.62 cm ME.