Low-Power Global Time Synchronization for the Contiki-NG Operating System

Abstract: Time synchronization is a well-known problem in low-power embedded wireless networks. While many synchronization protocols exist, usually they are not standard-compliant or do not provide synchronization of a global calendar time which is required by many applications, such as event correlation and certificate validation. To solve this problem, two novel synchronization approaches are proposed utilizing local synchronization information provided by the IEEE 802.15.4 Time Slotted Channel Hopping (TSCH) protocol. Evaluation results show that both solutions significantly outperform a simpler SNTP-based solution in regards to data and energy consumption, and time accuracy. The most performant solution---based on TSCH Enhanced Beacon frames---had the best performance but required a slight deviation from the TSCH standard. A limitation in time accuracy measurement methodology did not allow to see accuracy below a few milliseconds but still showed up to two orders of magnitude improvement over time accuracy achieved by using only SNTP protocol. The thesis conveys that a good global time synchronization performance can be achieved by utilizing well-known standard protocols, resulting in implementations with relatively low complexity.