PON ONU PSync Field Synchronization Reliability
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Solution Overview
Problem
Current PON synchronization methods, particularly in 50G-PON systems, face increased synchronization failures due to higher Bit Error Rates (BER) and shorter average times between failures, as existing PSync field lengths and error bit allowances are insufficient for reliable synchronization.
Innovation Solution
The implementation of a variably-sized PSync field with lengths greater than 64 bits, such as 128 or 192 bits, and increased error bit allowances (K values greater than 10), along with inverted and repeating sequences, enhances synchronization reliability and allows for clock recovery, reducing synchronization failures to intervals of several years.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PSync field length is increased to improve synchronization reliability, then the synchronization failure rate decreases, but the processing complexity and time increase
Solution Approach 1:
The PSync field is segmented into multiple sub-sequences (first sub-sequence and second sub-sequence), where the second sub-sequence is an inverted form of the first. This segmentation allows the receiver to perform matching operations on smaller units while maintaining overall synchronization reliability, thereby reducing processing complexity despite the increased total field length.
Solution Approach 2:
The ONU performs preliminary matching of the PSync field bits to a pre-stored sequence before full frame processing. By conducting this matching operation in advance and using the match result to guide subsequent processing, the system achieves high synchronization reliability with optimized processing complexity, as the pre-stored sequence enables quick comparison decisions.
2Duration of action of stationary object
If the PSync field length is increased to reduce synchronization failures, then the average time between failures increases, but the bandwidth utilization decreases
Solution Approach 1:
The system changes the parameter of PSync field length to specific values (128 bits or 192 bits) that optimize the balance between synchronization reliability and bandwidth utilization. These parameter choices extend the average time between synchronization failures to several years while maintaining acceptable bandwidth usage, as the increased length provides more redundancy without proportionally increasing overhead.
Solution Approach 2:
The PSync field uses an excessive number of bits (greater than 64 bits) for synchronization purposes, which extends the average time between failures to several years. This partial redundancy approach ensures that even with higher BER in 50G-PON systems, the synchronization remains reliable without requiring excessive bandwidth, as the additional bits provide error margin rather than increasing overall frame size proportionally.
3Reliability
If higher K values are used to allow more error bits, then synchronization reliability improves, but the precision of synchronization detection decreases
Solution Approach 1:
The PSync field is divided into sub-sequences that are matched separately, allowing the system to apply different K values to different segments. This segmentation enables the receiver to tolerate more errors in individual sub-sequences (higher K) while maintaining overall synchronization detection precision through the combined matching result of multiple segments.
Solution Approach 2:
The system performs preliminary matching with a pre-stored sequence to identify potential synchronization points before applying error tolerance thresholds. This preliminary action allows the receiver to first locate candidate positions with reasonable precision, then apply higher K values to confirm synchronization, thereby maintaining both detection precision and reliability.
Data Source
AI summary
An ONU is provided. The ONU comprises a receiver configured to receive a first PON frame from an OLT, the first PON frame comprising a first PSBd field, the first PSBd field comprising a first PSync field, the first PSync field comprising first bits, and a first quantity of the first bits being greater than 64 bits; and a processor coupled to the receiver and configured to perform synchronization of the first PON frame by matching the first bits to a pre-stored sequence.