Multilevel Coding Split Between Soft and Hard FEC Decoding
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Solution Overview
Problem
High power consumption and complexity of conventional soft forward error correction (FEC) decoding in optical fiber transmission systems, particularly at increasing data transmission rates, necessitate a balance between error correction capabilities and power efficiency.
Innovation Solution
A multidimensional multilevel coding (MLC) system that combines soft FEC and hard FEC encoding, where most significant bits (MSBs) are processed by a soft FEC encoder and least significant bits (LSBs) by a hard FEC encoder, with redundancy generated to form labels mapping to constellation points, reducing the load on soft FEC decoders and enhancing error correction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft FEC decoding is used to improve error correction capability, then reliability is improved, but power consumption increases significantly
Solution Approach 1:
The patent segments the label bits into two groups: MSBs processed by soft FEC decoder and LSBs processed by hard FEC decoder. This segmentation allows the system to apply the more reliable but power-intensive soft FEC decoding only to the more critical MSBs, while using the simpler hard FEC decoding for LSBs, thereby reducing overall power consumption while maintaining error correction capability.
Solution Approach 2:
The patent applies different decoding qualities to different parts of the data structure. MSBs are decoded with high quality (soft FEC) because they have greater impact on error correction, while LSBs are decoded with lower quality (hard FEC) since they are less critical. This local differentiation optimizes the balance between reliability and power consumption.
2Reliability
If soft FEC decoding is used to improve error correction capability, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the decoding task into two segments: soft FEC decoding for MSBs and hard FEC decoding for LSBs. This segmentation reduces the overall decoding complexity by limiting the computationally intensive soft FEC decoding to only the necessary MSBs, while handling LSBs with simpler hard FEC decoding.
Solution Approach 2:
The patent applies different decoding complexities to different bit positions. MSBs receive high-complexity soft FEC decoding to ensure reliability, while LSBs receive low-complexity hard FEC decoding. This local quality approach optimizes the trade-off between error correction capability and device complexity.
Data Source
AI summary
A multidimensional multilevel coding (MLC) encoder comprises a soft forward error correction (FEC) encoder receiving first bits for generating soft FEC encoded bits, a redundancy generator receiving a subset of the soft FEC encoded bits for generating redundant bits, and a hard FEC encoder receiving second bits for generating hard FEC encoded bits. Combinations of the soft FEC encoded bits, the redundant bits, and the hard FEC encoded bits form labels for mapping to a plurality of constellation points. A MLC decoder comprises a redundancy decoder, a soft FEC decoder and a hard FEC decoder. The redundancy decoder combines log-likelihood-ratios (LLR) of soft FEC encoded bits received from the MLC encoder to allow the soft FEC decoder to produce decoded bits. Decoding of hard FEC encoded bits by the hard FEC decoder is conditioned on values of the bits decoded by the soft FEC decoder.