Variable Bit Spacing for Magnetic Recording Error Reduction

Solution Overview

Problem

Certain bit patterns written to magnetic recording media result in higher error rates during readback, affecting detection and correction capabilities, while others have lower error rates, offering opportunities for optimization.

Innovation Solution

A system that analyzes and classifies patterns based on error rates, adjusting bit spacing by increasing resolution for error-prone patterns and decreasing it for patterns with low errors, using pre-write procedures and look-up tables to implement fractional bit spacing adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If uniform bit spacing is used for all patterns, then writing and reading processes are simple, but error rates vary significantly across different patterns

Engineering Contradiction:

Improvereadback error rateVSAvoidbit spacing control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by assigning different bit spacing values to different bit patterns based on their error characteristics. Specifically, patterns with higher error rates are assigned larger bit spacing values to improve detectability, while patterns with lower error rates use smaller bit spacing values. This is implemented through a lookup table that maps each pattern to its optimal bit spacing value, allowing the system to optimize reliability locally for each pattern type.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the bit spacing parameter dynamically based on the pattern being written. Instead of using a fixed bit spacing for all patterns, the system adjusts the bit spacing parameter according to the specific pattern's error characteristics. This parameter change is achieved by modifying the write channel's bit spacing control to select from multiple predefined spacing values based on pattern identification.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If bit spacing is increased for error-prone patterns, then detection capability improves, but storage capacity decreases

Engineering Contradiction:

Improvepattern detection capabilityVSAvoiddata storage capacity

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent applies local quality by assigning different bit spacing values to different bit patterns based on their error characteristics. Specifically, patterns with higher error rates are assigned larger bit spacing values to improve detectability, while patterns with lower error rates use smaller bit spacing values. This is implemented through a lookup table that maps each pattern to its optimal bit spacing value, allowing the system to optimize reliability locally for each pattern type.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by selectively adjusting bit spacing only for specific patterns that require it, rather than increasing bit spacing for all data. The system identifies patterns with high error rates and applies increased spacing only to those cases, leaving other patterns with standard or reduced spacing. This partial application of the spacing adjustment minimizes the overall impact on storage capacity while still improving detection for problematic patterns.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If bit spacing is decreased for low-error patterns, then storage capacity increases, but reliability may be compromised

Engineering Contradiction:

Improvestorage capacityVSAvoidreadback accuracy

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by assigning different bit spacing values to different bit patterns based on their error characteristics. Specifically, patterns with higher error rates are assigned larger bit spacing values to improve detectability, while patterns with lower error rates use smaller bit spacing values. This is implemented through a lookup table that maps each pattern to its optimal bit spacing value, allowing the system to optimize reliability locally for each pattern type.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by selectively adjusting bit spacing only for specific patterns that require it, rather than increasing bit spacing for all data. The system identifies patterns with high error rates and applies increased spacing only to those cases, leaving other patterns with standard or reduced spacing. This partial application of the spacing adjustment minimizes the overall impact on storage capacity while still improving detection for problematic patterns.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10482918B1Changing bit spacing for selected symbols written to a magnetic recording medium

Publication Date: 2019.11.19 SEAGATE TECH LLC

AI summary

A set of patterns written to a magnetic recording medium are found that result in a relatively high and/or low error when read back. Upon writing subsequent to the determining of the set of patterns, one pattern of the set of the patterns is identified within a data segment ready to be written to the magnetic recording medium. The data segment is written with a changed bit spacing in response to identifying that the one pattern of the set of the patterns is within the data segment.