Precision Time Protocol

About: Precision Time Protocol is a research topic. Over the lifetime, 604 publications have been published within this topic receiving 6006 citations. The topic is also known as: PTP & IEEE 1588.

IEEE 1588 standard for a precision clock synchronization protocol for networked measurement and control systems

Abstract: This paper discusses the major features and design objectives of the IEEE-1588 standard. Recent performance results of prototype implementations of this standard in an Ethernet environment are presented. Potential areas of application of this standard are outlined.

The white rabbit project

Abstract: Reliable, fast and deterministic transmission of control information in a network is a need for many distributed systems. One example is timing systems, where a reference frequency is used to accurately schedule time-critical messages. The White Rabbit (WR) project is a multi-laboratory and multi-company effort to bring together the best of the data transfer and timing worlds in a completely open design. It takes advantage of the latest developments for improving timing over Ethernet, such as IEEE 1588 (Precision Time Protocol) and Synchronous Ethernet. The presented approach aims for a general purpose, fieldbus-like transmission system, which provides deterministic data and timing (sub-ns accuracy and ps jitter) to around 1000 stations. It automatically compensates for fiber lengths in the order of 10 km. This paper describes the WR design goals and the specification used for the project. It goes on to describe the central component of the WR system structure the WR switch - with theoretical considerations about the requirements. Finally, it presents real timing measurements for the first prototypes of WR hardware.

Method and apparatus for synchronizing measurements taken by multiple metrology devices

Abstract: Apparatus includes at least two devices that communicate with each other, wherein a first one of the at least two devices having an IEEE 1588 precision time protocol interface, the interface including one or more components configured for communications in both a wired manner and a wireless manner with a second one of the at least two devices. The second one of the at least two devices having an IEEE 1588 precision time protocol interface, the interface including one or more components configured for communications in both a wired manner and a wireless manner with the first one of the at least two devices. Wherein one of the at least two devices includes a master clock and the other one of the at least two devices includes a slave clock, wherein the master clock communicates a time to the slave clock and the slave clock is responsive to the communicated time from the master clock to adjust a time of the slave clock if necessary to substantially correspond to the time of the master clock, thereby time synchronizing the at least two devices together.

Performance Analysis of Kalman-Filter-Based Clock Synchronization in IEEE 1588 Networks

Abstract: Performances in network-based synchronization depend on several related factors, including the instability of local clocks, the rate at which timing information is exchanged, and the accuracy of the resulting correction estimates. This paper analyzes these effects and their relationships, showing how these may affect the design of an IEEE 1588 Precision Time Protocol synchronization scheme. This paper introduces a state-variable clock model for which realistic parameters can be obtained for different kinds of clocks from experimental measurements of Allan variance plots. A Kalman-filter-based clock servo employing this model is developed, and a simulation analysis of the behavior of clock regulation and the effect of parameter variations on its performances is presented.

White Rabbit Precision Time Protocol on Long-Distance Fiber Links

Abstract: The application of White Rabbit precision time protocol (WR-PTP) in long-distance optical fiber links has been investigated. WR-PTP is an implementation of PTP in synchronous Ethernet optical fiber networks, originally intended for synchronization of equipment within a range of 10 km. This paper discusses the results and limitations of two implementations of WR-PTP in the existing communication fiber networks. A 950-km WR-PTP link was realized using unidirectional paths in a fiber pair between Espoo and Kajaani, Finland. The time transfer on this link was compared (after initial calibration) against a clock comparison by GPS precise point positioning (PPP). The agreement between the two methods remained within ${\pm }{2}\; \text{ns}$ over three months of measurements. Another WR-PTP implementation was realized between Delft and Amsterdam, the Netherlands, by cascading two links of 137 km each. In this case, the WR links were realized as bidirectional paths in single fibers. The measured time offset between the starting and end points of the link was within 5 ns with an uncertainty of 8 ns, mainly due to the estimated delay asymmetry caused by chromatic dispersion.