PON Time Synchronization via GTC Frame Header Timestamping
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Solution Overview
Problem
The existing time synchronization methods, such as IEEE 1588, are not supported in 'Ethernet over GEM' mode due to the loss of the time stamp generating point in the GEM frame, which prevents effective synchronization of clocks in Passive Optical Networks (PONs).
Innovation Solution
The method involves sending clock packets with their transmission times in downstream frames, using the packet time stamp generating point located at the last bit of the physical synchronization field in the GTC TC frame header, allowing for accurate synchronization of both master and slave clocks across the PON, enabling multiple encapsulation modes like IEEE 1588 in 'Ethernet over GEM' mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IEEE 1588 time synchronization method is used in PON, then time synchronization can be achieved, but it is not supported in 'Ethernet over GEM' mode due to loss of time stamp generating point
Solution Approach 1:
The patent introduces an intermediary mechanism by defining a specific time stamp generating point in the GTC TC frame header (at the physical synchronization field) that acts as a mediator between the PON protocol layer and the IEEE 1588 time synchronization protocol. This intermediary time stamp point enables Ethernet over GEM mode to support IEEE 1588 synchronization without requiring changes to the underlying PON protocol structure.
2Ease of operation
If time stamp is generated at GEM frame level, then Ethernet over GEM mode can operate, but the time stamp generating point is lost preventing synchronization
Solution Approach 1:
The patent shifts the time stamp generation from the traditional GEM frame level to a higher dimensional level in the protocol stack - specifically to the GTC TC frame header level. This dimensional shift in the protocol layer allows time stamping to occur at a point where synchronization information can be reliably captured while still supporting Ethernet over GEM encapsulation.
3Reliability
If IEEE 1588 synchronization is implemented, then clock synchronization is achieved, but it cannot be implemented in 'Ethernet over GEM' mode
Solution Approach 1:
The patent makes the time synchronization mechanism universal by defining a time stamp generating point in the GTC TC frame header that serves multiple functions: it supports both traditional PON modes and Ethernet over GEM mode, and enables IEEE 1588 synchronization across different encapsulation modes. This single time stamp point provides multi-functionality for different operational modes.
Data Source
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AI summary
The present invention relates to optical communications and discloses a master clock time synchronization method, slave clock time synchronization method, system and optical network device in a Passive Optical Network (PON) for the purpose of resolving time synchronization in Ethernet over Gigabit PON Encapsulation Method (GEM) mode. The PON master clock time synchronization method includes: predefining a rule for matching packet time stamp generating points; sending a first clock packet carried in a first downstream frame; acquiring time at a packet time stamp generating point that matches the frame data of the first downstream frame at the PON Media Access Control (MAC) layer and regarding the acquired time as the time the first clock packet is sent; and sending a second clock packet in a second downstream frame, where the second clock packet carries the time the first clock packet is sent.