Neural Decoding of Concatenated Codes for NAND Flash Reliability
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Solution Overview
Problem
Flash memory devices, such as NAND flash memory, experience errors due to noise and interference during programming and read operations, which existing error correction codes struggle to address effectively, especially under high stress conditions.
Innovation Solution
A memory system utilizing a deep neural network (DNN) decoder that performs soft decoding by receiving log-likelihood ratios, determining extrinsic estimation functions, and updating LLR values through iterative processes to correct errors, improving error correction capability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional error correction codes are used for NAND flash memory, then programming speed can be maintained, but error correction capability deteriorates under high stress conditions
Solution Approach 1:
The patent replaces traditional algebraic decoding algorithms with a neural network-based system that uses soft computing to decode error correction codes. The neural network processes log-likelihood ratios and syndrome information to directly output corrected codewords, eliminating the need for complex algebraic algorithms like Berlekamp-Massey or Euclidean algorithms, thereby reducing decoding complexity while maintaining or improving error correction capability under stress conditions
Solution Approach 2:
The patent changes the operational parameters of error correction by using soft information (log-likelihood ratios) instead of hard decisions, and by adjusting the neural network's internal parameters (weights and biases) through training on synthetic data that models various stress conditions. This allows the system to adapt to changing channel conditions and maintain high reliability without increasing decoding complexity
2Reliability
If strong error correction codes are used, then error correction capability improves, but programming speed deteriorates
Solution Approach 1:
The patent performs preliminary training of the neural network offline using synthetic data that models various stress conditions and error patterns. This pre-computes the optimal decoding behavior, so that during actual programming and decoding operations, the neural network can quickly process received signals without requiring complex real-time computations, thereby maintaining high programming speed while achieving strong error correction capability
Solution Approach 2:
The patent uses synthetic training data that copies and models various stress conditions and error patterns that might occur in real NAND flash memory operations. By training on these copied scenarios, the neural network learns to handle real stress conditions efficiently, achieving strong error correction without the overhead of complex real-time processing that would slow down programming operations
Data Source
AI summary
Systems, methods, non-transitory computer-readable media configured to perform operations associated with a storage medium. One system includes the storage medium and an encoding/decoding (ED) system, the ED system being configured to receive a set of input log-likelihood ratios (LLRs) of a component of the plurality of components, determine an extrinsic estimation function based on a set of features of the set of input LLRs, analyze the extrinsic estimation function to obtain a plurality of extrinsic LLR values, map the plurality of extrinsic LLR values to an input LLR of the set of input LLRs, and output, for each component, a plurality of updated LLR values based on the mapping.


