LTO-5 RLL Encoding to Limit ECC Error Propagation

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Solution Overview

Problem

Existing RLL codes in magnetic and optical data storage face challenges in minimizing error propagation and header error rates, particularly when used with ECC schemes like two-way interleaved RS encoding over GF(16), as they are prone to significant error bursts that exceed the error correction capability of the RS code.

Innovation Solution

The development of rate-(s(K+1)/(s(K+1)+1) TCMTR(j,k,t,a) codes, which encode data using an (s+1)-bit block with K unencoded symbols, reduces error propagation and header error rates by eliminating likely error events at the detector output, allowing for efficient error correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional RLL codes are used in magnetic and optical data storage, then data recording and reproduction can be performed, but error propagation is significant and exceeds the error correction capability of RS codes

Engineering Contradiction:

Improveerror correction capabilityVSAvoiderror propagation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the fundamental parameters of RLL codes by introducing a new code structure with modified constraints. The new code uses a different encoding approach that fundamentally alters the error propagation characteristics, reducing the maximum number of erroneous symbols from multiple symbols to at most one symbol per RS codeword, making errors correctable by the existing RS code.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces inexpensive header redundancy bits that can be sacrificed to prevent error propagation. By adding these extra check bits in the header portion of the data structure, the system can detect and contain errors before they propagate through the entire codeword, effectively using low-cost redundancy to protect against harmful error propagation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If header redundancy is increased to reduce error propagation, then error correction improves, but storage capacity is reduced

Engineering Contradiction:

Improveheader error rateVSAvoidstorage capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by concentrating error protection resources specifically in the header portion of the data structure rather than uniformly across all data. The enhanced redundancy and error protection are localized to the header, which contains critical metadata, while the main data portion maintains higher storage efficiency. This selective approach protects the most important information without unnecessarily reducing overall storage capacity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7432834B1RLL encoding for LTO-5 tape

Publication Date: 2008.10.07 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Method and apparatus are provided for encoding and decoding rate-(s(K+1)/s(K+1)+1) TCMTR(j,k,t,a) codes, where s is the ECC symbol size in bits and K is the number of unencoded symbols that are interleaved with an (s+1)-bit encoded block at the output of a rate-s/(s+1) encoder that encodes the r-th s-bit symbol. K=m/s−1 where m=s(K+1) is the total number of bits to be encoded. Error propagation is reduced, thus allowing the ECC code to correct errors efficiently. Header error-rate is also reduced by eliminating occurrence of likely error events at the detector output. Although initially an RLL code may be designed for an ECC symbol size of s bits, the RLL encoding of the present invention may be used in conjunction with ECC schemes that utilize symbol sizes other than s bits.