Key role of Timing and Synchronisation
Precise Time and Synchronisation (Timing&Sync) is crucial to a range of strategic activities. This is especially the case for Critical Infrastructure (CI), a system or asset essential for maintaining such vital societal functions as health, safety, security, economic and social well-being of people. GNSS is often used to provide this Timing & Sync service in CI.
GNSS can be used to provide both Timing & Synchronisation:
- Timing: GNSS provides direct and accurate access to Coordinated Universal Time (UTC).
- Synchronisation: Synchronisation between receivers at different locations can be established and maintained using GNSS reference time. In addition, a master clock synchronises itself using the time provided by GNSS, redistributing this time to the slave clocks disseminated within the systems.
NTP and PTP are protocols for clock synchronisation between computer systems. They can rely on GNSS as a time source. Key stakeholders in Timing&Sync are telecommunication network operators, associations like ENTSO-E in Energy, and regulatory bodies (these are highly regulated markets).
The user needs related to Timing&Sync depend heavily on the application. The accuracy requirements start from low in finance transactions (order of milliseconds) to medium for Energy and most Telecom applications (order of microseconds), whereas Satcom services have high accuracy needs (order of nanoseconds).There is an increasing interest in GNSS authentication and improved robustness to interference. In Energy, independence and continuity of service are also increasingly valuable. This is part of a global trend of a continuous security improvement.
GNSS role for Timing and Synchronisation applications
- In Satellite Communication (SATCOM), GNSS is used for TDMA (Time Division Multiple Access) timing on the satellite links and terrestrial links and NTP (Network Time Protocol) type services for IT/network/satellite monitoring/control.
- In Professional Mobile Radio (PMR) and Cellular Networks (Cellular), GNSS is used for the synchronisation of timeslots and for handovers between base stations.
- In Public Switched Telephone Networks (PSTN), GNSS is used as a backup in case timing information from atomic clocks is lost. GNSS reference time can be used for time of day, traffic timing and time slot management. Many telecom networks employ local oscillators that enable service to be temporarily maintained in case of GNSS loss.
Energy: Network automatic protection of systems (Wide Area Measurement Systems/ Wide Area Control Systems) are using Phasor Measurements Units (PMUs) as a source of Timing&Sync information for Network Monitoring (current use) and Automatic Protection (future use). Automatic Protection requires a high level of accuracy and redundancy at PMU level. PMUs are deployed across remote locations of the power network (nodes), with internal time references currently based on GNSS receivers.
Finance: Financial services rely on very powerful IT systems and networks requiring a high level of availability, security and reliability. GNSS is used for Synchronisation and Time Stamping functions to log events or quotes in a chronologic manner. There is a widespread use of transfer protocols like NTP/PTP to distribute time (a NTP Primary Server can be connected to about 1500/2000 NTP clients).