LDPC Codeword Decoding With Parity Sectors for Disk Read Recovery

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Solution Overview

Problem

Prior art data storage devices face inefficiencies in decoding codewords due to reliance on Viterbi-type detectors, which can increase signal noise, whereas using parity sectors for updating reliability metrics is more effective in compensating for all sources of signal noise, leading to suboptimal convergence of codewords during read operations.

Innovation Solution

Emphasizing the use of parity sectors over Viterbi-type detectors for updating reliability metrics, particularly through iterative LDPC decoding and generating multiple parity sectors across data segments to optimize codeword convergence and reduce the need for heroic data recovery procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Viterbi-type detectors are used for decoding codewords, then signal noise is increased, but decoding speed is maintained

Engineering Contradiction:

Improvedata recovery performanceVSAvoidsignal noise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the decoding process into two distinct phases: (1) initial LDPC decoding attempts to converge codewords, and (2) parity sector processing handles un-converged codewords. This segmentation allows the system to avoid using Viterbi-type detectors during initial decoding, thereby reducing signal noise while maintaining decoding capability through the alternative parity sector approach.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces parity sectors as an intermediary mechanism between the read operation and final data recovery. Instead of directly using Viterbi-type detectors on raw signals, the system first processes data through LDPC decoding and uses parity sectors to update reliability metrics of un-converged codewords, thereby mediating the decoding process to avoid noise amplification.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If parity sectors are used for updating reliability metrics, then convergence efficiency is improved, but processing complexity increases

Engineering Contradiction:

Improvecodeword convergence efficiencyVSAvoiddecoding process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent implements a dynamic decoding strategy where the system adaptively switches between LDPC decoding and parity sector processing based on convergence status. The decoder dynamically identifies un-converged codewords and applies parity sector updates only to those specific codewords, rather than processing all codewords uniformly, thereby optimizing convergence efficiency while managing complexity through selective processing.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The parity sector mechanism serves itself by automatically identifying and processing only the un-converged codewords that need attention. The system self-manages the decoding workflow by monitoring convergence status and directing parity sector updates to specific codewords, reducing the need for external intervention and simplifying overall system control despite the enhanced processing capability.

Inventive Principle:

Principle #25Self-service

3Reliability

If multiple parity sectors are generated across data segments, then data recovery performance is improved, but storage overhead increases

Engineering Contradiction:

Improvedata recovery performanceVSAvoidstorage overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by generating parity sectors specifically for data segments containing un-converged codewords rather than uniformly across all data segments. This localized approach ensures that parity processing resources are concentrated where needed, improving data recovery performance for problematic segments while avoiding unnecessary storage overhead in segments that have already converged successfully.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system discards the conventional approach of uniformly applying Viterbi-type detection to all codewords and recovers efficiency by selectively applying parity sector processing only to un-converged codewords. This selective recovery strategy improves overall data recovery performance while minimizing the storage and processing overhead associated with parity sectors.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS10530390B2Data storage device employing memory efficient processing of un-converged codewords

Publication Date: 2020.01.07 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A data storage device is disclosed comprising a head actuated over a disk comprising a data track having at least a first data segment and a second data segment. A first plurality of codewords are generated, and a first parity sector is generated over the first plurality of codewords. The first plurality of codewords and the first parity sector are written to the first data segment. A second plurality of codewords are generated, and a second parity sector is generated over the second plurality of codewords. The second plurality of codewords and the second parity sector are written to the second data segment. During a read operation the data segments of the data track are processed sequentially to decode the codewords using a low density parity check (LDPC) decoder, wherein the reliability metrics of un-converged codewords are stored in a codeword buffer and updated using the respective parity sector.