PTP Communication Apparatus Path Switch Delay Compensation
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Solution Overview
Problem
Time accuracy degradation occurs during synchronization processing with a time server when switching between different length transmission paths in a communication apparatus using Precision Time Protocol (PTP), due to differences in transmission delays between outbound and return packet paths.
Innovation Solution
A communication apparatus with two network interfaces connected to different transmission paths calculates a statistical transmission delay value by averaging multiple immediate transmission delay values, reducing the impact of temporary disturbances and maintaining synchronization accuracy by adjusting its time offset accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the communication apparatus includes two network interfaces connected to different transmission paths to improve robustness, then system reliability is improved, but time synchronization accuracy deteriorates due to transmission delay differences between paths
Solution Approach 1:
The system performs preliminary actions by calculating and storing transmission delay characteristics for each transmission path before switching occurs. When a path switch is detected, the system retrieves the pre-calculated delay characteristics of the new path and applies compensation, avoiding time accuracy degradation without requiring delay recalculation after switching.
Solution Approach 2:
The system changes parameters by dynamically adjusting the transmission delay compensation value based on the specific transmission path being used. Each path has its own delay characteristics, and the system modifies the compensation parameter accordingly when switching between paths, ensuring accurate time synchronization regardless of which path is active.
2Productivity
If the communication apparatus switches transmission paths to maintain communication continuity, then system availability is improved, but time synchronization accuracy deteriorates due to unaccounted transmission delay changes
Solution Approach 1:
The system implements feedback by continuously monitoring transmission path status and detecting switches. When a path switch is detected, the system retrieves the appropriate transmission delay characteristics for the new path and adjusts the time synchronization compensation accordingly, ensuring continuous accurate synchronization despite path changes.
Solution Approach 2:
The system performs preliminary actions by pre-calculating and storing transmission delay characteristics for each available path before switching occurs. This allows the system to immediately apply the correct compensation when switching paths, maintaining time synchronization accuracy without interruption to communication continuity.
3Speed
If the system uses immediate transmission delay values for synchronization, then responsiveness is improved, but time synchronization accuracy deteriorates due to temporary disturbances affecting individual measurements
Solution Approach 1:
The system performs preliminary actions by calculating multiple immediate transmission delay values and determining a statistical characteristic (such as average or median) before using it for synchronization. This pre-calculated statistical value is then used as the transmission delay compensation, providing both responsiveness and immunity to temporary disturbances.
Solution Approach 2:
The system uses feedback by continuously measuring immediate transmission delay values and updating the statistical characteristic accordingly. This allows the system to maintain an accurate representation of the transmission delay while filtering out temporary disturbances through statistical processing, balancing responsiveness with precision.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A communication apparatus for connection to a time source apparatus via a first transmission path and a second transmission path performs packet communication with the time source apparatus according to Precision Time Protocol by using either the first transmission path or the second transmission path, synchronizes a time on the communication apparatus with a time on the time source apparatus by using a transmission delay value of the first transmission path if a transmission path used for the packet communication is the first transmission path, switches the transmission path if a predetermined condition is satisfied, and synchronizes the time on the communication apparatus with the time on the time source apparatus by using a transmission delay value of the second transmission path different from the transmission delay value of the first transmission path if the transmission path is switched from the first transmission path to the second transmission path.