Time Synchronization in Passband Transmission Systems
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Solution Overview
Problem
Current time synchronization methods face challenges in achieving high precision, particularly in passband transmission systems like DMT and OFDM, where continuous signal transmission makes it difficult to determine symbol boundaries and obtain time stamp information.
Innovation Solution
A method and system that obtain time stamps at specific positions of symbols in both the master and slave clocks, using a predetermined specific position as the trigger edge, and adjust the slave clock to synchronize with the master clock based on these time stamps, even in systems that transmit signals continuously in units of symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If synchronization pulse signal is used to trigger time stamp obtaining in optical and Ethernet systems, then time synchronization can be implemented, but this method cannot be applied to passband transmission systems with continuous symbol transmission
Solution Approach 1:
The patent changes the triggering parameter from external synchronization pulse edges to internal symbol structure features (specific sample positions within symbols). This allows the time stamp obtaining mechanism to adapt to passband transmission systems where continuous symbol transmission eliminates obvious signal boundaries, while maintaining measurement precision through deterministic sampling at defined symbol positions.
2Measurement precision
If time stamps are obtained at signal edges in continuous symbol transmission systems, then measurement can be performed, but obvious boundaries between symbols do not exist making time stamp information difficult to obtain
Solution Approach 1:
The patent segments the continuous symbol transmission stream into discrete measurement points by selecting specific sample positions within symbols (e.g., first time-domain sample). This segmentation creates artificial but deterministic measurement boundaries that enable time stamp obtaining without requiring natural signal transitions or obvious symbol boundaries.
Solution Approach 2:
The patent introduces an intermediary reference (specific symbol position definition) that mediates between the continuous symbol transmission and the discrete time stamp measurement requirement. This intermediary provides a deterministic mapping point that enables precise time stamp obtaining without directly detecting symbol boundaries.
3Measurement precision
If IEEE1588 PTP basic mechanism is used for time synchronization, then synchronization between master and slave clocks can be achieved, but high-precision time synchronization is hard to implement in passband systems
Solution Approach 1:
The patent modifies the IEEE1588 PTP mechanism by changing the triggering parameter from external synchronization pulse edges to internal symbol structure features. This parameter change maintains compatibility with the basic PTP framework while enabling high-precision time synchronization in passband transmission systems through deterministic sampling at defined symbol positions.
Data Source
AI summary
A method, apparatus, and system for time synchronization are disclosed. The method comprising: obtaining a master sending time stamp, a slave receiving time stamp, a slave sending time stamp, and a master receiving time stamp; and adjusting the time of the slave clock according to the offset calculated from the time stamps to synchronize with the clock time of the master clock. With the present invention, in passband transmission systems that transmit signals continuously in units of symbols, the time synchronization is implemented between the master clock and the slave clock.