Pre-interleaving Physical Synchronization Blocks in PON
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Solution Overview
Problem
In next-generation passive optical networks, inter-codeword interleaving of the physical synchronization block (PSBd) makes it difficult for optical network units (ONUs) to frame synchronize due to the spread-out sequence, complicating the location of the PSync pattern and superframe counter (SFC) in the bit pattern.
Innovation Solution
The method involves generating a predetermined number of codewords where the first N codewords comprise interleaved blocks of the physical synchronization block, ensuring the PSBd forms a consecutive sequence at the beginning of the physical layer data frame through inter-codeword interleaving, allowing for easy synchronization by the ONUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inter-codeword interleaving is performed on the physical synchronization block, then burst errors are spread over several codewords improving FEC performance, but the PSBd no longer forms a consecutive sequence making frame synchronization difficult
Solution Approach 1:
The physical synchronization block is divided into multiple segments (first synchronization block, second synchronization block, etc.) that are distributed across different codewords. Each segment contains a portion of the PSBd bits, allowing the PSBd to be spread over multiple codewords while maintaining synchronizability through the structured segmentation approach.
Solution Approach 2:
The patent applies preliminary interleaving of the physical synchronization block before the main data transmission. By pre-interleaving the PSBd segments onto different codewords in advance, the system prepares the synchronization structure to withstand burst errors while maintaining the ability to locate and synchronize using the distributed segments.
2Reliability
If the physical synchronization block is spread out over multiple bits through interleaving, then error distribution is improved, but the location of PSync pattern and superframe counter becomes difficult
Solution Approach 1:
The PSBd is segmented into multiple blocks that are distributed across different codewords. Each segment contains a portion of the synchronization information, allowing the system to maintain error distribution benefits while providing multiple reference points for synchronization detection.
Solution Approach 2:
The patent uses the distributed synchronization blocks to provide feedback mechanisms for frame synchronization. The ONUs can use the scattered PSBd segments across multiple codewords to verify and maintain synchronization status, with the superframe counter providing feedback on frame positioning despite the interleaved structure.
Data Source
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AI summary
The present invention discloses a method in an optical line terminal communicatively connected to a plurality of optical network units, comprising: generating a predetermined number of codewords for a downstream frame, wherein, the first N codewords comprise in their first bit values at least one block of b bits of a physical synchronization block corresponding to the downstream frame, N ≥2, b≥1; wherein, the blocks of the physical synchronization block are interleaved on the first N codewords; performing inter-codeword interleaving on the predetermined number of codewords, thereby obtaining a physical layer data frame, wherein, the physical synchronization block forms a consecutive sequence at the beginning of the physical layer data frame; and transmitting the physical layer data frame to the plurality of optical network units.