Permutation Scrambling for Flash Memory Shaped Data

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Solution Overview

Problem

Existing data scrambling methods, such as XOR-based techniques, fail to preserve the proportion of 1's and 0's in shaped data, leading to a random distribution and potential program disturb effects in flash memory due to repetitive patterns.

Innovation Solution

Permutation scrambling, which reorders bit locations using a pseudo-random or random prime integer, ensuring that the proportion of 1's and 0's is maintained, and can be reversed for data recovery, is implemented in data storage devices like SSDs and flash memory cards.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If XOR-based scrambling is applied to shaped data, then repetitive patterns are removed and data appears more random, but the proportion of 1's and 0's is lost and becomes substantially random distribution

Engineering Contradiction:

Improveremoval of repetitive patternsVSAvoidloss of shaped proportion

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent introduces an intermediary element (the scrambling sequence with controlled bit proportion) that mediates between the shaped data and the memory storage. This intermediary sequence has the same bit proportion as the original shaped data, allowing it to preserve the shaping characteristics while still providing scrambling functionality to eliminate repetitive patterns.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the parameter of the scrambling sequence to match the bit proportion of the shaped data. Instead of using a traditional random sequence with 50% bit proportion, the scrambling sequence is generated with the same proportion of 1's and 0's as the input shaped data, thereby preserving the shaping characteristics during the scrambling process.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If shaped data is stored directly to memory, then memory wear is reduced due to non-random distribution, but repetitive patterns cause program disturb effects

Engineering Contradiction:

Improvereduction of memory wearVSAvoidprogram disturb effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces scrambling as an intermediary processing step between shaping and memory storage. The scrambling operation with controlled bit proportion acts as a mediator that eliminates harmful repetitive patterns while preserving the beneficial bit proportion characteristics, thus preventing program disturb effects without compromising memory wear reduction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potentially harmful effect of repetitive patterns into a benefit by using a scrambling sequence that itself has the same bit proportion as the shaped data. The scrambling process eliminates repetitive patterns (harmful) while the controlled bit proportion ensures the scrambled data still provides wear reduction benefits (useful).

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS8666068B2Method for scrambling shaped data

Publication Date: 2014.03.04 SANDISK TECHNOLOGIES LLC

AI summary

A method includes, in a data storage device, receiving data having a particular proportion of zero values and one values and scrambling the data to generate scrambled data that has the particular proportion of zero values and one values.