Clock Synchronization Using Linear Programming, Multicasts, and Temperature Compensation
Henning Puttnies, Eike Bjoern Schweissguth, Dirk Timmermann, Jörg Schacht · 2019
Clock (or time) synchronization is essential for many applications in the Industrial Internet of Things (IIoT). Hence, it is a vital research field and important field of standardization ambitions. The most accurate protocols like PTP and gPTP need specialized hardware to reach their maximum precision. Without this hardware, they cannot compensate massive packet delays. It was shown that approaches based on linear programming (LP) can mitigate this problem. However, changes in the clock frequency lead to nonlinear clocks, which are not well compensated by LP-based approaches. As a consequence, we propose the SLMT approach that uses LP, multicasts, and temperature compensation for time synchronization. To the best of our knowledge, SLMT is the first synchronization approach that combines LP and one-way exchange or multicasts, respectively. Consequently, it is efficient regarding the number of messages. Furthermore, to the best of our knowledge, SLMT is the first synchronization approach that combines LP with a temperature compensation in order to mitigate LP's conceptual drawback with nonlinear clocks. In an extensive evaluation and comparison to many state-of-the-art approaches, we show that SLMT outperforms these approaches, especially under harsh conditions like rapid temperature changes and unknown non-negligible network delays.