Microsemi’s new TimeSource Enhanced Primary Reference Time Clock (ePRTC) solution, based on ITU-T G.8272.1, is a highly accurate, reliable and autonomous source of time, frequency and phase synchronization, regardless of the availability of GNSS.
This brief video discusses the concepts around the PRTC, GNSS Vulnerability, and the benefits of ITU-T G.8272.1, the ePRTC. It features Greg Wolff of Microsemi, recorded at the ePRTC product launch at the ITSF conference in Prague.
Background: ITU Standards for Primary References
When looking at the evolution of Primary Reference standards, developed by the ITU, the original requirement was for a Primary Reference Clock (PRC) called G.811. The G.811 required a PRC that delivers 1 part in 10E11 frequency accuracy and is suitable for timing and synchronization of other clocks within a network.
As packet timing requirements emerged, ITU developed the Primary Reference Time Clock (PRTC) standard to include the requirements for time and phase for transport over a packet network. This standard is known as G.8272 and was originally published in 2012. The G.8272 standard describes a clock that delivers <100 nS time and phase performance suitable for packet networks.
Today’s Standard: The ePRTC, per ITU-T G.8272.1
There is a new ITU standard (ITU-T G.8272.1) with an aim to achieve the following results:
- Increase performance for time and phase to meet the requirements of emerging mobile access network technologies.
- Improve security for protection against GNSS outages.
The new standard is called the Enhanced Primary Reference Timing Clock (ePRTC). This new standard (G.8272.1) calls for performance levels and reliability that will set the foundation for time, phase, and frequency for many years to come.
ePRTC Key attributes
Key attributes of an ePRTC include:
- Support for a high level of accuracy (<30 ns), subject to more stringent output performance requirements, as compared to existing PRTC systems.
- An ePRTC is an autonomous source of time that utilizes one or two co-located atomic clocks to provide the required performance for both time and frequency, even when GNSS is completely lost.
- An ePRTC delivers a higher level of operational reliability to ensure operators can maintain the required time and frequency service performance for long periods, regardless of the availability of GNSS.
The objective of the ePRTC solution is to generate time by producing its own autonomous TimeScale. The TimeScale provides time, phase, and frequency that are aligned and calibrated to the GNSS signal over time. The TimeScale is generated and maintained autonomously based on the stability of the atomic clocks. The frequency stability of the atomic clocks serves as a reference for the ePRTC time scale. This is the key distinguishing feature when comparing an ePRTC to a PRTC. In the case of a PRTC, time is essentially coming directly from GNSS. In the ePRTC, a locally generated TimeScale is generated.
For more info on the Microsemi TimeSource ePRTC: