Time Synchronization via Multi-Wavelength Path Delay Compensation
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Solution Overview
Problem
Current time synchronization methods in network communication, such as the 1588 protocol, face inaccuracies due to differences in path delays between receiving and transmitting directions, leading to errors in time synchronization, especially in TD-SCDMA and future LTE/Wimax networks, which require precise time and phase synchronization.
Innovation Solution
A method that involves sending time packets over multiple wavelengths to automatically measure and calculate absolute time deviations between nodes, allowing for precise synchronization by compensating for path delays in both directions, independent of the 1588 protocol, thereby ensuring accurate time synchronization between nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the 1588 protocol is used to calculate path delay and absolute time deviation, then time synchronization between master and slave devices is achieved, but time synchronization error occurs due to difference between path delay in receiving direction and path delay in transmitting direction
Solution Approach 1:
The patent segments the time synchronization process into multiple measurement stages: measuring path delay in transmitting direction using timestamps from master to slave, measuring path delay in receiving direction using timestamps from slave to master, calculating the difference between these delays, and applying compensation. This segmentation allows each direction's delay to be measured and corrected independently, resolving the synchronization error caused by assuming equal bidirectional delays.
2Measurement precision
If manual measurement and correction of time synchronization error is performed using OTDR to measure fiber lengths, then time synchronization accuracy is improved, but the process becomes complicated and requires repeated measurements when transmission path changes
Solution Approach 1:
The system performs self-measurement and self-correction of time synchronization errors using automated timestamp exchanges between master and slave devices. The slave device automatically measures path delays in both directions, calculates the time synchronization error, and applies compensation without requiring external OTDR equipment or manual intervention. This eliminates the complexity of manual fiber length measurement and enables automatic adaptation when transmission paths change.
Solution Approach 2:
The patent implements a feedback mechanism where the slave device continuously measures path delays, calculates time synchronization errors, and applies real-time compensation to maintain accurate synchronization. The system automatically detects and corrects delays without requiring external measurement tools, providing continuous self-adjustment based on actual transmission conditions.
3Measurement precision
If fiber lengths of lines in both directions are measured manually using OTDR, then time synchronization error can be calculated and compensated, but the process is time-consuming and inaccurate when transmission path changes due to network deployment or maintenance
Solution Approach 1:
The system performs preliminary automatic measurement of path delays in both transmitting and receiving directions using timestamp exchanges before time synchronization is established. By pre-measuring and storing these delay values, the system eliminates the need for time-consuming manual OTDR measurements when transmission paths change, enabling rapid recalculation and compensation of time synchronization errors.
Data Source
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AI summary
The present invention relates to the network communication field, and discloses a time synchronization method, which includes: a first node sends a first time packet at a first time over a first working wavelength; a second node receives the first time packet at a second time; the first node sends a second time packet at a third time over a second working wavelength, and the second node receives the second time packet at a fourth time; and calculates an absolute time deviation between the second node and the first node according to the first time, the second time, the third time, the fourth time, a first signal transmission rate corresponding to the first working wavelength, and a second signal transmission rate corresponding to the second working wavelength, and synchronizes the local time between the second node and the first node. Further, a time synchronization system and a node device are disclosed.