Main Benefits of National Timing Grid of Ireland – National Timing Grid of Ireland

GNSS and atomic clock as a time source

Atomic clocks provide a very stable frequency signal. Thanks to this exceptional frequency stability, atomic clocks are used as a time source all around the world. To align those stable frequency signals in time most devices use Global Navigation Satellite Systems to phase lock atomic clocks to accurate time. Even though GNSS is a very reliable system, it experiences failures over time.

In case of GNSS failure atomic clocks provide a very long-term stability and would guarantee that over a 14-day period those clock would drift as little as 200 ns apart (if properly steered and conditioned). However, over a longer period of times those atomic clocks would inevitably drift apart, as there would be no common time scale available (currently provided by a GNSS, most likely GPS, to be specific). In case the GNSS provides inaccurate information (e.g. the incident from January 2016, where UTC derived from GPS was biased by -13 µs), atomic clocks could be affected too.

Each individual atomic clock provides great value to its owner, but having them combined, or interlinked, would enable creation of a much more resilient timing infrastructure – National Timing Grid of Ireland.

The main objectives of the initiative in the first phase are:

Near real time tracking of stability against other atomic clocks providing early warnings in case of performance degradation.
Direct traceability to UTC through UTC(NSAI) instead of UTC through GNSS (e.g., UTC(NIST) through GPS time).
PTP link stability evaluation.

The main objectives of the initiative in the first phase are:

Any feedback implementation (improvements) etc.
IEEE 1588 PTP links verification and monitoring.
Improved holdover in case of GNSS degradation through a common timescale observation and steering.
GNSS time stability observation (GPS, Galileo, BeiDou, GLONASS) and failure detection.
Improved robustness to GNSS failures and glitches.

Third phase:

Any feedback implementation (improvements) etc.
Options for sub-nanoseconds time transfer: 1588 PTP WR links.