Compensating software timestamping interference from periodic non-interruptable tasks

For distributed measurements to be consistently aligned a global notion of time within the network is necessary. Clock synchronization performance is hampered by delays and jitter accumulated not only in the network, but also in the timestamping procedures of the devices being synchronized. The resources available on such sensors are often constrained, both by cost and power consumption. Software solutions on single processor systems are common. While the synchronization process is critical, it usually has a supporting role and therefore cannot be assumed to have the highest priority. This paper analyzes the influence of periodic, non-interruptable tasks (e.g. measurements) on the timestamping process, presents mathematical models for simulation and a modified median filter to efficiently deal with these errors.