Grand Master List Verification for IEEE 802.1AS Time Continuity
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Solution Overview
Problem
In Factory Automation (FA) networks using IEEE 802.1AS time synchronization protocol, time continuity is not guaranteed when conventional stations not implementing the method coexist with IEEE 802.1AS compliant stations, leading to potential discontinuity and incorrect control due to large time changes.
Innovation Solution
A communication system with a list reference station that records a grand master list and corrects its time based on this list, ensuring time continuity by verifying the sender station's code in time distribution frames, preventing large time changes and maintaining network synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If every station implements the time synchronization method of Patent Literature 1, then time continuity can be guaranteed, but device complexity increases and compatibility with conventional stations is reduced
Solution Approach 1:
The system divides stations into two types: list reference stations that implement the full time synchronization method with grand master list verification, and conventional stations that use standard IEEE 802.1AS. This segmentation allows the complex reliability-enhancing mechanism to be applied only where needed while maintaining simplicity for other stations.
Solution Approach 2:
The grand master list acts as an intermediary data structure that list reference stations use to verify the legitimacy of time distribution frames. By introducing this intermediate verification layer, the system ensures time continuity without requiring all stations to implement the complex verification logic.
2Reliability
If list reference stations verify sender station codes against the grand master list, then large time changes are suppressed, but measurement precision requirements increase
Solution Approach 1:
The grand master list is pre-populated with the station codes of legitimate grand masters before time synchronization begins. This preliminary preparation allows list reference stations to quickly verify incoming time distribution frames by simple code matching, reducing the precision requirements during runtime verification.
Data Source
AI summary
A list distribution station of a communication station includes processing circuitry to record, in a memory, a grand master list containing a station code of a grand master and a station code of a communication station synchronized with the grand master, and receive a priority notification frame which contains, as a sender station code, a station code of a present grand master in the communication system. The processing circuitry is further included to decide, when notified of the station code of the present grand master, whether or not to update the grand master list based on the notified station code of the present grand master and the grand master list, and upon having decided to update the grand master list, to update the station code of the present grand master station on the grand master list with the notified station code of the present grand master station.