| 摘要 |
A method and apparatus for encoding, detecting and decoding data in a Partial Response (PR) class-IV magnetic recording storage system that does not require the conventional interleave constraint and therefore minimizes the path memory and latency of a sequence detector such as the Maximum Likelihood (ML) Viterbi detector. Rather than encoding an interleave constraint to ensure merging of path memories in the detector, the parity of the encoded codewords is utilized in selecting tile correct sequence out of the unmerged paths. The encoding technique encodes the data using two groups of codewords; the first group causes the path memories of the sequence detector to merge into one survivor sequence and the second group causes the path memories to merge into two survivor sequences different in only one bit and thus different in parity. The correct survivor sequence is thereby selected according to the parity of the codeword being detected. Parity is determined during the encoding process such that codewords from the second group follow codewords with even or odd parity. By looking ahead to the following codeword during the detection process, the parity of the current codeword being detected is determined and the correct survivor sequence selected. Further, the encoding technique provides the ability to correct for certain errors in the detected sequence when a "1" bit is erased due to noise in the system.
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