Virtual Primary Reference Time Clock (vPRTC)

Resilient Timing For Today’s Networks

Critical infrastructures for communications, transportation, energy, and data centers need accurate and precise clocks. The Global Navigation Satellite System (GNSS) has been deployed across these industries as the only way to deliver local 100 ns timing accuracy. This has resulted in an exponential growth of GNSS timing solutions in mission-critical applications. From a purely technical perspective, this has worked very effectively and efficiently. From a reliability standpoint, however, the pervasive use of GNSS has created a significant vulnerability and security exposure for these applications.


The requirements for timing and synchronization are shifting from accuracy and precision to security and resiliency. Simply delivering an accurate timing instance is no longer enough. Designers of critical infrastructure must ensure that their timing source can be validated and trusted, that they maintain network-wide visibility and monitoring and, most importantly, that they have resiliency in the form of backups and protection when something goes wrong, because it will.

Three Components of Robust vPRTC


Monitoring and protection are provided by our secure BlueSky™ GNSS firewall technology:

  • Creates highly secure GNSS systems to calibrate and align the vPRTC solution to UTC
  • Shields your critical infrastructure from GNSS jamming and spoofing attacks


High-precision atomic system clocks are at the heart of the vPRTC system:

  • Provide an autonomous time scale that can maintain accurate time if GNSS is impaired
  • Represent the world standard in timekeeping


Our portfolio of solutions help establish a trusted timescale:

  • TimeProvider® 4100 Enhanced Primary Reference Time Clock combines the atomic clock and validated GNSS inputs
  • High-performance PTP boundary clocks distribute time over your wide area network with a budget of less than 5 ns per hop
  • TimePictra® Synchronization Management System monitors and manages these functions

Video: How vPRTC Works


GPS Hardening Against GNSS Spoofing and Jamming

The virtual Primary Reference Time Clock (vPRTC) is a highly secure and resilient network-based timing architecture that has been developed to meet the expanding needs of modern critical infrastructures. The vPRTC is simple in concept. It blends proven timing technologies into a centralized and protected source location and then uses commercial fiber optic network links and advanced IEEE® 1588 Precision Time Protocol (PTP) boundary clocks to distribute 100 ns PRTC timing where it is needed in end points that might be hundreds of kilometers away. The central locations receive their UTC time traceability from GNSS via highly protected and validated receivers. Advanced firewall technologies continuously monitor for threats in the form of GNSS spoofing or jamming attacks to assure that only valid signals from the sky are passed to the central clock. The vPRTC uses industry-proven cesium atomic clocks to establish 30 ns guaranteed accuracy traceable to UTC. If an invalid GNSS signal is detected or denied, the vPRTC source maintains ±100 ns traceability to UTC for a minimum of 14 days.

With these highly resilient clocks in place, critical infrastructure operators can use their secure fiber network to distribute protected timing to all necessary locations. Just as a GNSS-satellite-based timing system distributes timing to end points using open-air transmission, the vPRTC distributes timing using the fiber network. The difference is that the operator remains 100% in control of the network and can secure it as necessary. The vPRTC architecture can be deployed as the sole source of timing or it can be deployed as a backup to GNSS timing solutions.