GLDPC Soft Decoding with Selective Hard-Decision Switching

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Solution Overview

Problem

Existing Generalized Low-Density Parity Check (GLDPC) decoding methods face challenges in efficiently correcting errors, particularly due to high latency, power consumption, and vulnerability to trapping sets, as they often require complex soft decoding processes that are not always necessary.

Innovation Solution

A decoder system that initially attempts hard decoding for GLDPC code words and switches to soft decoding using channel hard decisions or soft reliability measures only when necessary, reducing complexity and power consumption by selectively applying soft decoding based on predefined criteria, such as the number of failed component codes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If soft decoding is always applied to GLDPC code words, then error correction capability is improved, but power consumption and processing complexity increase significantly

Engineering Contradiction:

Improveerror correction capabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The system dynamically selects between hard decoding and soft decoding modes based on the decoding status of component codes. The decoder controller monitors whether component codes are successfully decoded and adaptively switches the decoding mode for the current code word, making the system flexible rather than static.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Soft decoding is applied selectively only to specific code words that require it (those where component codes fail to decode), rather than uniformly to all code words. This localized application of the more powerful soft decoding reduces overall power consumption while maintaining error correction capability where needed.

Inventive Principle:

Principle #3Local quality

2Reliability

If soft decoding is always applied to GLDPC code words, then error correction capability is improved, but processing time and latency increase

Engineering Contradiction:

Improveerror correction capabilityVSAvoiddecoding latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Instead of always applying the full soft decoding process, the system applies only hard decoding when sufficient (when component codes succeed), and uses soft decoding only when necessary (when component codes fail). This partial application reduces average processing time while maintaining error correction capability when needed.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If complex soft decoding processes are applied to all code words, then error correction capability is improved, but device complexity increases

Engineering Contradiction:

Improveerror correction capabilityVSAvoiddecoding process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The decoding process is segmented into two distinct stages: a first decoding stage using component codes (hard decoding), and a second decoding stage using the main GLDPC decoder (soft decoding). This segmentation allows the system to attempt simpler decoding first and only invoke the more complex soft decoding when necessary.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #15Dynamics

4Use of energy by stationary object

If hard decoding is used for all code words, then power consumption and processing time are reduced, but error correction capability deteriorates due to trapping sets

Engineering Contradiction:

Improvepower consumptionVSAvoiderror correction capability

Core Design Contradiction:

Use of energy by stationary objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The decoder controller provides feedback by monitoring the decoding results of component codes and using this information to determine whether to proceed with soft decoding. This feedback mechanism ensures that soft decoding is triggered only when hard decoding fails, optimizing the balance between power consumption and error correction capability.

Inventive Principle:

Principle #23Feedback

5Device complexity

If hard decoding is used for all code words, then device complexity is reduced, but decoding performance deteriorates due to trapping sets

Engineering Contradiction:

Improvedecoding process complexityVSAvoiderror correction capability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10084481B2GLDPC soft decoding with hard decision inputs

Publication Date: 2018.09.25 APPLE INC

AI summary

A decoder includes circuitry and a soft decoder. The circuitry is configured to receive channel hard decisions for respective bits of a Generalized Low-Density Parity Check (GLDPC) code word that includes multiple component code words, including first and second component code words having one or more shared bits, to schedule decoding of the GLDPC code word, and following the decoding, to output the decoded GLDPC code word. The soft decoder is configured to receive the channel hard decisions corresponding to the first component code word, to further receive soft reliability measures that were assigned to the shared bits in decoding the second component code word, and to decode the first component code word based on the channel hard decisions and the soft reliability measures.