Viterbi bit detection method and device

A Viterbi bit detector for detecting the bit values of bits of a channel data stream stored on a record carrier along an N-dimensional channel tube, N being at least two, of at least two bit rows one-dimensionally evolving along a first direction and being aligned with each other along at least a second of N−1 other directions, said first direction together with said N−1 other directions constituting an N-dimensional lattice of bit positions, said Viterbi bit detector comprising a Viterbi bit detection unit for application of a row-based one-dimensional Viterbi bit detection method independent for each of the bit rows of said channel tube, said Viterbi bit detection unit comprising:

• means for calculating branch metrics for all possible state transitions in a Viterbi trellis of a one-dimensional row-based Viterbi detector, said transitions representing a number of subsequent bits in said bit row, said bits being the central-row bits of a cluster of the N-dimensional lattice of bits, said calculating being based on the difference of the received HF signal value with respect to a reference level, wherein said reference level depends on all bits of said cluster, said cluster comprising, in addition to the central-row bits, a number of primary neighboring bits in each of a number of neighboring bit rows on each side along said N−1 other directions of said central bit row along which the one-dimensional Viterbi bit detector is applied, and wherein preliminary bit decisions for the primary neighboring bits in the neighboring bit rows are used for determining the reference level to be used for calculating said branch metrics;
• and
• means for selecting the bit value for the central bit of said cluster of the N-dimensional lattice of bits, corresponding with said received HF signal value, based on the calculated branch metrics.

A method of reproducing a user data stream, said user data stream being error correction code and modulation code encoded into a channel data stream and stored on a record carrier, said reproducing method comprising a Viterbi bit detection method for detecting the bit values of bits of the channel data stream stored on the record carrier along an N-dimensional channel tube, N being at least two, of at least two bit rows one-dimensionally evolving along a first direction and being aligned with each other along at least a second of N−1 other directions, said first direction together with said N−1 other directions constituting an N-dimensional lattice of bit positions, a modulation code decoding method and an error correction code decoding method,

• wherein said Viterbi bit detection method comprises the steps of:
• applying a row-based one-dimensional Viterbi bit detection method independent for each of the bit rows of said channel tube;
• calculating branch metrics for all possible state transitions in a Viterbi trellis of a one-dimensional row-based Viterbi detector, said transitions representing a number of subsequent bits in said bit row, said bits being the central-row bits of a cluster of the N-dimensional lattice of bits, said calculating being based on the difference of the received HF signal value with respect to a reference level, wherein said reference level depends on all bits of said cluster, said cluster comprising, in addition to the central-row bits, a number of primary neighboring bits in each of a number of neighboring bit rows on each side along said N−1 other directions of said central bit row along which the one-dimensional Viterbi bit detection method is applied, and wherein preliminary bit decisions for the primary neighboring bits in the neighboring bit rows are used for determining the reference level to be used for calculating said branch metrics;
• and
• selecting the bit value for the central bit of said cluster of the N-dimensional lattice of bits, corresponding with said received HF signal value, based on the calculated branch metrics.

A reproduction device for reproduction of a user data stream, said user data stream being error correction code and modulation code encoded into a channel data stream and stored on a record carrier, said reproduction device comprising a Viterbi bit detector for detecting the bit values of bits of the channel data stream stored on the record carrier along an N-dimensional channel tube, N being at least two, of at least two bit rows one-dimensionally evolving along a first direction and being aligned with each other along at least a second of N−1 other directions, said first direction together with said N−1 other directions constituting an N-dimensional lattice of bit positions, a modulation code decoder and an error correction code decoder,

• wherein said Viterbi bit detection unit comprising:
• means for calculating branch metrics for all possible state transitions in a Viterbi trellis of a one-dimensional row-based Viterbi detector, said transitions representing a number of subsequent bits in said bit row, said bits being the central-row bits of a cluster of the N-dimensional lattice of bits, said calculating being based on the difference of the received HF signal value with respect to a reference level, wherein said reference level depends on all bits of said cluster, said cluster comprising, in addition to the central-row bits, a number of primary neighboring bits in each of a number of neighboring bit rows on each side along said N−1 other directions of said central bit row along which the one-dimensional Viterbi bit detector is applied, and wherein preliminary bit decisions for the primary neighboring bits in the neighboring bit rows are used for determining the reference level to be used for calculating said branch metrics;
• and
• means for selecting the bit value for the central bit of said cluster of the N-dimensional lattice of bits, corresponding with said received HF signal value, based on the calculated branch metrics.

An optical recorder comprising a Viterbi bit detector for detecting the bit values of bits of a channel data stream stored on a record carrier along an N-dimensional channel tube, N being at least two, of at least two bit rows one-dimensionally evolving along a first direction and being aligned with each other along at least a second of N−1 other directions, said first direction together with said N−1 other directions constituting an N-dimensional lattice of bit positions, said Viterbi detector comprising a Viterbi bit detection unit for application of a row-based one-dimensional Viterbi bit detection method independent for each of the bit rows of said channel tube, said Viterbi bit detection unit comprising:

• means for calculating branch metrics for all possible state transitions in a Viterbi trellis of a one-dimensional row-based Viterbi detector, said transitions representing a number of subsequent bits in said bit row, said bits being the central-row bits of a cluster of the N-dimensional lattice of bits, said calculating being based on the difference of the received HF signal value with respect to a reference level, wherein said reference level depends on all bits of said cluster, said cluster comprising, in addition to the central-row bits, a number of primary neighboring bits in each of a number of neighboring bit rows on each side along said N−1 other directions of said central bit row along which the one-dimensional Viterbi bit detector is applied, and wherein preliminary bit decisions for the primary neighboring bits in the neighboring bit rows are used for determining the reference level to be used for calculating said branch metrics;
• and
• means for selecting the bit value for the central bit of said cluster of the N-dimensional lattice of bits, corresponding with said received HF signal value, based on the calculated branch metrics.