RLL Modulation Encoding with Sliding-Window Constraint Shaping
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Solution Overview
Problem
Current data storage systems face challenges in improving capacity due to limitations in modulation encoding with tight global and interleave constraints, particularly in RLL codes, which struggle to exclude synchronization patterns and achieve efficient high-rate codes compatible with existing tape drives.
Innovation Solution
The method involves sliding-window encoding to tighten global constraints while relaxing interleave constraints, using unique substitute sequences that violate interleave run-length limits, allowing for efficient implementation of RLL codes with improved global and interleave constraints, ensuring compatibility with synchronization patterns and enhancing data storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tight global and interleave constraints are imposed in RLL codes, then synchronization patterns can be excluded and reliability is improved, but data storage capacity is reduced
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional tight (G, I) constraints to a new constraint regime where the global constraint G is significantly tightened while the interleave constraint I is relaxed. This is achieved through sliding-window encoding that enforces run-length limits on sliding windows of the bit stream, allowing longer runs in interleaved positions while maintaining overall synchronization pattern exclusion, thereby increasing storage capacity without sacrificing reliability
2Productivity
If high-rate modulation codes are used to increase data storage capacity, then productivity is improved, but the ability to maintain tight run-length constraints is compromised
Solution Approach 1:
The patent applies segmentation by dividing the bit stream into overlapping sliding windows and applying run-length constraints independently to each window position. This segmentation approach allows the encoder to maintain high coding rates while ensuring that no window violates the global run-length constraint, effectively decoupling the high-rate requirement from constraint satisfaction
Solution Approach 2:
The patent employs dynamic constraint enforcement through sliding-window encoding where the constraint application moves dynamically through the bit stream. Unlike static codeword-boundary constraints, the sliding window continuously adjusts its position, allowing the encoder to adaptively satisfy run-length constraints while maintaining high data rates, thus resolving the contradiction between productivity and precision
Data Source
AI summary
A method for producing N-bit output words of RLL-encoded data having both a global constraint Go and an interleave constraint Io on bits of a first value includes receiving N-bit input words of RLL-encoded data having both a global constraint Gi and an interleave constraint Ii on bits of like value; and producing the output words from respective input words by sliding-window encoding of each input word to replace predetermined bit-sequences with respective substitute sequences such that Go<Gi; wherein each substitute sequence is unique and violates a run-length limit associated with the interleave constraint Ii such that Io>Ii.