Time Transmission Correction Device for PTP Link Asymmetry
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Solution Overview
Problem
The Precision Time Protocol (PTP) assumes equal uplink and downlink delays, leading to errors in time synchronization accuracy due to link asymmetry, particularly intra-device delays in transmission paths.
Innovation Solution
A time transmission correction device is introduced, which includes a first clock unit for synchronizing time information, a second clock unit for frequency synchronization, a delay setting unit to set a transmission delay, and a time adjustment unit to correct time shifts. This device sets a certain delay to absorb link asymmetry, ensuring accurate time synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTP protocol is used for time synchronization via packet network, then time information can be distributed economically and reliability of GNSS reception can be improved, but time synchronization accuracy deteriorates due to link asymmetry between uplink and downlink delays
Solution Approach 1:
A time transmission correction device is introduced as an intermediary component between the master node and slave node. This device includes a delay setting unit that equalizes the uplink and downlink transmission delays by introducing appropriate delay adjustments. The correction device acts as a mediator that compensates for the link asymmetry in the packet network, allowing the PTP protocol to maintain both reliability and accuracy in time synchronization.
Solution Approach 2:
The invention changes the delay parameter in the transmission path by using a delay setting unit to adjust and equalize the uplink and downlink delays. By dynamically modifying the delay parameter through the correction device, the system compensates for link asymmetry and restores time synchronization accuracy while maintaining the economic benefits of packet network distribution.
2Measurement precision
If delay setting unit is introduced to equalize uplink and downlink delays, then time synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The time transmission correction device serves as a dedicated intermediary component that centralizes the delay equalization function. Rather than complicating existing nodes, the invention introduces a separate correction device that specializes in delay adjustment, thereby improving accuracy while containing complexity in a dedicated module rather than distributing it across the entire system.
Data Source
AI summary
[Problem] To provide a time synchronization mechanism that is not affected by link asymmetry between time synchronization devices.[Solution] A DC 4 used in a time transmission system that transmits and receives a PTP packet between a master node 1 and a slave node 2 via the DC 4 and synchronizes time of the slave node 2 based on time information on the transmission and reception includes a PTP clock unit 12 that synchronizes time information by the arrived PTP packet, a frequency clock unit 21 that synchronizes time information by a frequency signal, a delay setting unit 22 that sets, such that a transmission delay of the PTP packet between the master node 1 and the slave node 2 becomes a setting delay Lmax, a waiting time of the PTP packet based on a time difference between a departure time of the PTP packet and an arrival time of the PTP packet at the DC 4, which is determined from the time information of the frequency clock unit 21, and a time adjustment unit 26 that corrects a time shift from reference time in the time information of the frequency clock unit 21 based on the time information of the PTP clock unit 12.