Resilient Time Synchronization Opportunistically Exploiting UWB RTLS Infrastructure

Ultra wide band (UWB)-based solutions for real-time localizations are starting to be widely diffused. They use two-way ranging (TWR) scheme achieving indoor positioning accuracy well below 10 cm. These wireless devices are based on counters with picosecond resolution, which could also be used for node time synchronization. This work aims to propose an opportunistic approach for transparently obtaining multiple accurate time synchronization from low-cost infrastructure of real-time location systems (RTLS). After the description of the proposed approach, the idea is demonstrated using off-the-shelf UWB modules from Decawave and their related software. Thanks to hardware timestamping support inside the core architecture, the realized wireless station is able to simultaneously lock and track several time references generated by the UWB module. The extensive experimental characterization evaluates both the uncertainty of the reference signal generated by the UWB receiver and the time synchronization uncertainty of the whole host system running a proportional integrative (PI) control loop for locking the master reference clock. The time reference pulses are delivered by the UWB modules with a maximum jitter on the order of 40 ns, whereas the synchronization uncertainty is less than 10 ns.