Precision Time for Industry

Time transfer is a scheme where multiple sites share a precise reference time. The technique is commonly used for creating and distributing standard time scales such as Universal Coordinated Time (UTC) and International Atomic Time (TAI). White Rabbit Precision Time Protocol (PTP-WR) is one of the best performing time transfer techniques.

Outperforming existing capabilities, providing accurate (<200 ps), resilient and secure timing traceable to Coordinated Universal Time (UTC), it is able to exploit telecommunication fibre networks, enabling its use in widespread applications. This project has developed the metrological capacities required to accelerate the industrial adoption of PTP-WR, through improved hardware and calibration techniques, implemented in industrial environments.

The WRITE Project main achievements:

a) WRITE developed improved and scalable calibration techniques for (PTP-WR), which have been proven to be reliable, and that now ensure the capability has a complete dissemination chain with an accuracy better than 200 ps.

b) WRITE developed architectures and methods for redundant and resilient time transfer to industrial end users.

c) WRITE developed a new generation of PTP-WR hardware, offering an accuracy below 200 ps and an unprecedented frequency instability of <6×10-15 over an observation time of 100 s (Allan deviation).

d) WRITE disseminated Universal Time Coordinated UTC(k) time scales using PTP-WR from NMIs to industrial users (telecommunication, aerospace, electronic manufacturers).

e) WRITE contributed to the revision of the IEEE-1588 standard for PTP in 2020, which was updated to include White Rabbit as “High Accuracy option” in the IEEE-1588-2019 standard.

The need met by the project:

There is an increasing demand for synchronisation networks that provide precise time and frequency: e.g. telecommunication operators building 5G mobile communication networks, the power-grid sector utilising smart grids, the financial sector needing to comply with EU regulations, and scientific users. International recommendations are driving improvements to current timing and UTC traceability. For example, in finance the European ‘Markets in Financial Instruments Directive’ (MiFID II), issued by the European Securities and Markets Authority, requires improved accuracy and traceability on time stamping of financial transactions from January 2018. In addition, industrial needs require solutions that are easily standardised.

PTP-WR is a technique suited for dissemination of Universal Coordinated Time UTC(k) time scales and frequency. However, whilst the calibration techniques required for PTP WR were well developed in specific, dedicated fibre links where the parameters are well known, there was still a need to develop improved scalable calibration techniques that would match different telecommunication networks.

Currently, time and frequency dissemination for most industrial applications is realised through radio signals and satellite time broadcasting, such as the widely used Global Navigation Satellite System (GNSS). However, GNSS broadcasting suffers from integrity and resilience weaknesses, since the weak power received from the satellites on Earth make spoofing, hacking and disturbance due to space weather a real threat. Techniques with higher resilience and with built in redundancy are therefore required.

The current best achievable time transfer accuracy is 2 ns – 5 ns using high quality GNSS receivers, which corresponds to a frequency resolution of 10-14 over one day measurement time, but this requires specific receivers and competences only available in national metrology institutes and very specialised scientific laboratories. Industry generally relies on less highly-performing GNSS timing equipment that is usually limited to an accuracy of 10 ns – 100 ns.

WRITE demonstrated that PTP-WR offers a reliable solution for time dissemination, offering much better performance of 200 ps accuracy and resolution of 6×10-15 over 100 s measurement time. Moreover, PTP-WR over fibre is more resilient to attacks, since it is not affected by jamming or spoofing. WRITE definitely demonstrated that PTP‑WR strongly outperforms the commonly used techniques.

At the beginning of the project, in-field dissemination of Universal Coordinated Time UTC(k) time scales and frequency over optical fibres was still to be reliably demonstrated. WRITE implemented several dissemination PTP-WR links over fibre, suited for industrial needs, with a solid UTC dissemination. WRITE demonstrated real tests in production or industrial environments, which are fundamental to boost the uptake by industry and other sectors.