LTO-5 RLL Encoding to Limit Error Propagation and Header Errors
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Solution Overview
Problem
Current RLL codes in magnetic and optical data storage face challenges in minimizing error propagation and header error rates, particularly at moderate normalized linear densities, where error correction codes struggle to effectively handle short channel error bursts.
Innovation Solution
The development of rate-(s(K+1))/(s(K+1)+1) TCMTR(j,k,t,a) codes, which encode data input sequences into output sequences that satisfy specific constraints (j, k, t, and a constraints) to reduce error propagation and header error rates by interleaving and precoding the data, allowing for efficient error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RLL codes are used in magnetic and optical data storage, then data can be recorded and reproduced, but error propagation occurs and header error rates increase, particularly at moderate normalized linear densities
Solution Approach 1:
The patent segments the data stream into synchronized codeword objects (SCOs) with headers and data portions. The header contains synchronization markers and control information that are separately encoded from the data portion. This segmentation allows error correction codes to be applied specifically to headers with appropriate redundancy, isolating header errors from data errors and preventing error propagation across the entire codeword.
Solution Approach 2:
The patent applies preliminary error correction encoding to headers before the main data encoding. Headers are encoded with Reed-Solomon codes and interleaved with data, creating a structured format where error correction can be performed in stages. This preliminary action on headers ensures that synchronization and control information remain intact even when data portions experience errors.
2Reliability
If error correction codes are applied to headers with increased redundancy, then header reliability improves, but codeword length and storage overhead increase
Solution Approach 1:
The patent applies different encoding schemes and redundancy levels to different parts of the codeword. Headers receive enhanced error correction with Reed-Solomon codes and interleaving, while data portions use standard RLL encoding. This local quality approach optimizes reliability where needed (headers) without unnecessarily increasing redundancy throughout the entire codeword, maintaining efficiency in data storage regions.
3Ease of manufacture
If RLL encoding is applied to eliminate undesired sequences, then recording and reproduction processes are facilitated, but likely error events occur at the detector output
Solution Approach 1:
The patent employs preliminary anti-action by designing RLL codes with specific transition constraints that prevent error-prone patterns before recording. The encoding scheme incorporates minimum and maximum transition run constraints that eliminate sequences likely to cause detection errors. Additionally, synchronization markers with specific transition patterns are inserted to provide reliable reference points that counteract the effects of RLL encoding on error susceptibility.
Data Source
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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 5-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.