Memory Decoder LLR Updating for Channel Mismatch Recovery

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Solution Overview

Problem

Existing memory systems face inefficiencies in decoding data due to suboptimal log likelihood ratios (LLRs) used for decoding, which can lead to slower decoding processes and incomplete data recovery, especially when actual conditions differ from assumed or estimated conditions.

Innovation Solution

A method where a controller in a memory system pauses the convergence process to update LLR values based on calculated reliability characteristic values, using both magnitude and sign components of reliability metric values to generate updated a posteriori and a priori LLR values, allowing for improved decoding by adapting to actual storage conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional decoding schemes use fixed LLR values based on assumed or estimated conditions, then the decoding process is simpler to implement, but decoding accuracy and convergence speed deteriorate when actual conditions differ from assumptions

Engineering Contradiction:
Improvedecoding accuracyVSAvoiddecoding process complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements dynamic LLR value adjustment during the convergence process. The controller pauses the convergence process at intermediate stages to recalculate LLR values based on current reliability characteristic values, allowing the decoding process to adapt to actual channel conditions rather than relying on fixed initial assumptions. This dynamic approach improves decoding accuracy while managing complexity through structured pausing and recalculation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent introduces feedback mechanisms where the convergence process monitors its own progress and uses intermediate results to update LLR values. By pausing convergence and recalculating reliability metrics based on current decoding state, the system feeds back improved information to subsequent decoding iterations, creating a self-correcting process that enhances accuracy.

Inventive Principle:
Principle #23Feedback

2Productivity

If the convergence process runs continuously without interruption, then decoding speed is maintained, but decoding accuracy deteriorates when initial LLR assumptions are incorrect

Engineering Contradiction:
Improvedecoding speedVSAvoiddecoding accuracy
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements periodic interruption of the convergence process at predetermined stages. Instead of continuous operation, the controller pauses convergence at intermediate points to recalculate LLR values, then resumes the process. This periodic action allows the system to maintain overall decoding speed while periodically correcting accuracy issues that arise from initial assumption mismatches.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent performs preliminary recalculation of LLR values at intermediate stages before the convergence process completes. By pausing and updating reliability characteristic values based on current decoding state, the system prepares improved LLR values in advance for the next convergence phase, ensuring better accuracy in subsequent iterations without significantly delaying overall decoding.

Inventive Principle:
Principle #10Preliminary action

3Reliability

If LLR values are updated dynamically during convergence, then decoding accuracy improves under varying conditions, but computational overhead and processing time increase

Engineering Contradiction:
Improvedata recovery reliabilityVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent implements partial updates of LLR values at selective convergence stages rather than continuous updates. The controller pauses convergence at predetermined intermediate points to recalculate reliability characteristic values, performing updates only when necessary to correct significant assumption mismatches. This partial action approach improves data recovery reliability while minimizing unnecessary computational overhead and processing time.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentUS10938421B2Decoding optimization for channel mismatch
Publication Date: 2021.03.02 SANDISK TECHNOLOGIES LLC
  • US10938421B2 patent drawing
  • US10938421B2 patent drawing
  • US10938421B2 patent drawing

AI summary

A memory system configured to decode a data set may pause a convergence process to update reliability metric values. The memory system may utilize a positive feedback system that updates the reliability metric values by analyzing current a posteriori reliability metric values to calculate average estimated reliability characteristic values associated with a memory error model. The updates to the reliability metric values may provide increased error correction capability and faster decoding.