LDPC Windowed Decoding for Variable-Throughput Optical Links
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Solution Overview
Problem
Optical transmission systems face challenges in handling various throughputs without changing the circuit configuration, particularly in supporting multi-level encoding with existing error correction methods that require different redundancy levels for each bit, leading to complex configurations and inefficiencies.
Innovation Solution
The optical transmission/reception device configures variable window sizes and decoding iteration counts based on throughput input to the error correction decoding unit, allowing for multi-level encoding that adapts to different throughputs without altering the circuit configuration, using a single type of LDPC convolutional code for efficient error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different redundancy levels are used for each bit in multi-level encoding, then error correction performance is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter of redundancy level from being fixed per bit to being dynamically adjustable based on throughput. By varying the redundancy level parameter according to the input throughput, the system achieves different error correction performances for different throughputs without requiring multiple dedicated circuits, thus resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent introduces dynamic adaptability by making the redundancy level variable rather than static. The error correction decoding unit can dynamically adjust the redundancy level based on the input throughput, allowing the same circuit to adapt to different operational conditions and achieve optimal error correction performance across various throughputs without increasing circuit complexity
2Adaptability or versatility
If multiple error correction circuits are provided for different redundancy levels, then adaptability to various throughputs is improved, but device complexity increases
Solution Approach 1:
The patent makes a single error correction decoding unit universal by enabling it to handle multiple redundancy levels. The decoding unit can process codewords with different redundancy levels (e.g., R=1/3, R=2/5, R=3/7) by adjusting its internal parameters, eliminating the need for multiple dedicated circuits and achieving throughput adaptability without increasing device complexity
Solution Approach 2:
The system achieves adaptability to various throughputs by changing the redundancy level parameter within a single error correction decoding unit. This parameter change allows the same circuit to be configured for different error correction requirements, providing versatility without requiring multiple physical circuits
3Reliability
If spatially-coupled LDPC code with large combined code length is used, then error correction performance is improved, but decoding circuit scale and delay increase
Solution Approach 1:
The patent segments the decoding process by processing codewords in units of smaller block lengths rather than using a single large combined code length. This segmentation allows the decoding circuit to maintain a manageable scale while still achieving good error correction performance by processing data in manageable chunks, thus resolving the contradiction between reliability and device complexity
Data Source
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AI summary
Provided is an optical transmission/reception device including: an error correction encoding unit (23) configured to encode a sequence to be transmitted with one type of LDPC code; and an error correction decoding unit (36) configured to decode a received sequence encoded with the LDPC code. The error correction decoding unit (36) performs decoding processing for the received sequence based on a check matrix of an LDPC convolutional code. The decoding processing is windowed decoding processing, which is performed by using a window extending over one or more check submatrices. A window size of the window and a decoding iteration count are configured to be variable, and the window size and the decoding iteration count are input from a control circuit connected to the error correction decoding unit.