PON Time Synchronization via Dedicated Management Path
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Solution Overview
Problem
Passive Optical Networks (PON) systems face challenges in achieving accurate time synchronization between Optical Network Units (ONUs) and Optical Line Terminals (OLTs due to random phase differences, which hinder network utilization and mobile communications.
Innovation Solution
Implementing a time synchronization method using the IEEE1588 protocol, where the OLT calculates and transfers transmission delay information to the ONU through a management path, allowing the ONU to calculate its time offset and synchronize with the OLT, utilizing either the PLOAM or OMCI message path to ensure accurate time synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the PON protocol is used for frequency synchronization only, then the synchronization implementation is simple, but the time synchronization capability is lost and mobile communications cannot be supported
Solution Approach 1:
The patent makes the PON protocol multi-functional by enabling it to perform both frequency synchronization and time synchronization functions. The OLT sends synchronization packets containing timestamp information that ONUs use to calculate both frequency and time offsets, allowing the same protocol to support multiple synchronization requirements including mobile communications.
2Measurement precision
If the IEEE1588 protocol is implemented in PON, then time synchronization accuracy is improved, but the network complexity increases due to delay jitter in GPON encapsulation
Solution Approach 1:
The patent extracts the time synchronization function from the complex GPON data plane and implements it separately through a dedicated synchronization packet mechanism. The OLT sends specific synchronization packets with timestamp information that are processed independently from the regular GEM frame encapsulation, thereby avoiding the delay jitter issues of the data plane while maintaining time synchronization accuracy.
3Productivity
If GEM frame encapsulation is used for service stream transfer, then bandwidth utilization is improved, but fixed delay cannot be guaranteed due to segmentation and recombination
Solution Approach 1:
The patent segments the synchronization function from the data plane by using dedicated synchronization packets that are not subject to GEM frame encapsulation. These synchronization packets travel through a separate path that does not involve segmentation and recombination, thereby guaranteeing fixed delay while allowing the main data plane to maintain high bandwidth utilization through GEM encapsulation.
Data Source
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AI summary
The invention discloses a time synchronization method and system for a passive optical network (PON) system to solve the problem that an ONU cannot be synchronized with an OLT accurately in the PON. The invention implements the time information synchronization between the ONU and the OLT by using a management path. The time information includes an information transmission delay between the ONU and the OLT and the sending time identifier information of the time information. The invention avoids the technical defect of the unfixed delay for an upper layer protocol data message in a GPON by using the characteristic that a PLOAM message or an OMCI message is not segmented during the transmission thereof in the PON, thus ensuring every ONU can be synchronized with the OLT accurately.