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EP0133480A2
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Method and apparatus for decoding the output signal of a partial-response communication or recording-device channel
Assignee: International Business Machines Corp
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Filing: 1984-07-11
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Granted: —
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Expires: 2004-07-11
Abstract
Abstract A maximum-likelihood sequence decoder is used with a partial-response signaling system for processing sequences of sampled values from a communication channel or recording device. The partial-response signals can be duobinary, dicode, or partial-response class-IV. The maximum-likelihood decoding for each sequence is based upon a two-state trellis. lnstead of two survivor metrics for the two states, only a difference metric is generated which is simpler but sufficient for the decoding process. The decoder comprises survivor metric determining circuitry (81...99) which, from each input sample (y<sub>n</sub>) and a previous difference metric (DJ<sub>n</sub>-<sub>3</sub>) determines a new difference metric (DJ<sub>n-1</sub>), two additional binary values (b<sup>+</sup>, b-) for the two survivor sequences, as well as a binary output value (b) for making a selection among the two survivor sequences.
Inventors
- 👤 François Bernard Dolivo
- 👤 Gottfried Ungerboeck
- 👤 Thomas David Howell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 07:50
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03006; H04L25/03178; H04L25/03184; H04L2025/0335; H04L2025/03356; H04L2025/03369; H04L25/03203
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
125 words
A method for maximum-likelihood sequence decoding of the output signal of a communication or recording device channel, the output signal being based upon an original sequence of binary symbols an = +1 or -1, n being an integer time index, the output signal being filtered and sampled to obtain samples y with intersymbol interference of the partial-response type, characterized in that this method, for determining the most likely transmitted or recorded sequence of binary symbols, comprises the steps of: decoding the sample sequences based upon a state transition model having only two possible states at each sampling instant; and recursively computing a metric representing the difference between two not explicitly computed survivor metrics, each survivor metric measuring the probability of the binary survivor sequence obtained.
Claim 2
Independent Claim
125 words
A method for maximum-likelihood sequence decoding of the output signal of a communication or recording device channel, the output signal being based upon an original sequence of binary symbols an = +1 or -1, n being an integer time index, the output signal being filtered and sampled to obtain samples y with intersymbol interference of the partial-response type, characterized in that this method, for determining the most likely transmitted or recorded sequence of binary symbols, comprises the steps of: decoding the sample sequences based upon a state transition model having only two possible states at each sampling instant; and recursively computing a metric representing the difference between two not explicitly computed survivor metrics, each survivor metric measuring the probability of the binary survivor sequence obtained.
Claim 3
Dependent Claim
97 words
A method according to claim 1, for decoding of signal samples y of the partial-response class-IV type described by polynomial 1-d 2 , characterized in that two binary decision symbols for extending two binary survivor sequences stored in path memory are generated at each sampling instant, the sign of the difference metric is used to determine, at each sampling instant, which one of the two survivor sequences is the more probable from which the decoder output is to be selected, and the sequences of even and odd indexed samples Yn are independently decoded in an interleaved procedure.
Claim 4
Independent Claim
204 words
A method of maximum-likelihood sequence decoding of the output signal of a communication or recording device channel, said channel synchronously transmitting or recording a sequence of binary symbols an = +1 or -1, n being an integer symbol time index, said output signal being filtered and sampled to obtain samples y with intersymbol interference of the partial-response classes described by the polynomials 1+d, 1-d, or 1-d 2 , the method determining from the samples y the most likely transmitted or recorded sequence of binary symbols, characterized by the steps of: recursively computing a difference metric at each sampling instant, which metric represents the difference between implicit survivor metrics, each implicit survivor metric indicating the probability of occurrence of the binary survivor sequence obtained and stored in the path memory of a decoder for two possible states in the state transition diagrams underlying the decoding process, and generating two binary decision symbols and using these to extend the binary survivor sequences stored in the path memory, the sign of the difference metric determining at each sampling instant which one of the survivor sequences currently stored in the path memory is the more probable sequence from which the output of the decoder is to be selected.
Claim 5
Independent Claim
204 words
A method of maximum-likelihood sequence decoding of the output signal of a communication or recording device channel, said channel synchronously transmitting or recording a sequence of binary symbols an = +1 or -1, n being an integer symbol time index, said output signal being filtered and sampled to obtain samples y with intersymbol interference of the partial-response classes described by the polynomials 1+d, 1-d, or 1-d 2 , the method determining from the samples y the most likely transmitted or recorded sequence of binary symbols, characterized by the steps of: recursively computing a difference metric at each sampling instant, which metric represents the difference between implicit survivor metrics, each implicit survivor metric indicating the probability of occurrence of the binary survivor sequence obtained and stored in the path memory of a decoder for two possible states in the state transition diagrams underlying the decoding process, and generating two binary decision symbols and using these to extend the binary survivor sequences stored in the path memory, the sign of the difference metric determining at each sampling instant which one of the survivor sequences currently stored in the path memory is the more probable sequence from which the output of the decoder is to be selected.
Claim 6
Dependent Claim
58 words
A method according to claim 3, for maximum-likelihood sequence decoding of sample signals with intersymbol interference of the partial-response class-IV type being described by polynomial l-d 2 , characterized in that the two sequences of even and odd indexed samples y n are independently decoded based upon independent state transition diagrams with two states at each sampling instant.
Claim 7
Dependent Claim
182 words
Apparatus for maximum-likelihood sequence decoding of sample sequences with intersymbol interference of the partial-response class-IV type described by polynomial 1-d 2 , said apparatus having a whitened match filter (13), sampling means (15), and survivor sequence storage and updating means (21), characterized by metric value determining circuitry (19; Fig. 6) which comprises: means (91) for adding a recent sample value (y n-1 ) and the range limited difference of said recent sample value (y n-1 ) and a previous difference survivor metric (DJ n-3 ), and for delivering a new difference survivor metric (DJ n-1 ); means (85) for subtracting a new sample (y ) from a recent difference survivor metric (DJ n-2 ); means (81) for limiting the output of the subtracting means (85) to a range between +1 and -1 and for generating two intermediate binary decision values (b + n-2 and b - n-2 ); n-2 means (97) connected to the output of said adding means (91) for generating a binary output value (b n-1 ) representing the sign of the new difference survivor metric (DJ n-1 ) .
Claim 8
Dependent Claim
182 words
Apparatus for maximum-likelihood sequence decoding of sample sequences with intersymbol interference of the partial-response class-IV type described by polynomial 1-d 2 , said apparatus having a whitened match filter (13), sampling means (15), and survivor sequence storage and updating means (21), characterized by metric value determining circuitry (19; Fig. 6) which comprises: means (91) for adding a recent sample value (y n-1 ) and the range limited difference of said recent sample value (y n-1 ) and a previous difference survivor metric (DJ n-3 ), and for delivering a new difference survivor metric (DJ n-1 ); means (85) for subtracting a new sample (y ) from a recent difference survivor metric (DJ n-2 ); means (81) for limiting the output of the subtracting means (85) to a range between +1 and -1 and for generating two intermediate binary decision values (b + n-2 and b - n-2 ); n-2 means (97) connected to the output of said adding means (91) for generating a binary output value (b n-1 ) representing the sign of the new difference survivor metric (DJ n-1 ) .
Claim 9
Dependent Claim
87 words
Apparatus according to claim 5, characterized in that the inputs of said adding means (91) are connected through clocked registers (83, 89) to a sample input (y n ) and to the output of the limiting means (81), respectively, the inputs of said substracting means (85) are connected to said sample input (y ) and, through a clocked register (87), to the output of said adding means, respectively, so that output values can be generated for even and odd indexed sample values independently in a pipelined process.
Claim 10
Dependent Claim
152 words
Apparatus for maximum-likelihood sequence decoding of sample sequences with intersymbol interference of the partial-response class-IV type described by polynomial 1-d 2 , said apparatus having a matched filter (13), sampling means (15), and survivor sequence storage and updating means (21), characterized by metric value determining means (19; Fig. 7) which comprises: means (103) for adding a new sample value (z ) and a range limited previous difference survivor metric (DJ n-2 ), and for delivering a new difference survivor metric (DJ n ) ; means (81a) for limiting the value of a recent difference survivor metric (DJ n-1 ) to a range between +1 and -1 and for generating two intermediate binary decision values (b + n-1 and b n-1 ); and means (111) connected to the output of said adding means (103) for generating a binary output value (b ) re- presenting the sign of the new difference survivor metric (DJn).
Claim 11
Dependent Claim
152 words
Apparatus for maximum-likelihood sequence decoding of sample sequences with intersymbol interference of the partial-response class-IV type described by polynomial 1-d 2 , said apparatus having a matched filter (13), sampling means (15), and survivor sequence storage and updating means (21), characterized by metric value determining means (19; Fig. 7) which comprises: means (103) for adding a new sample value (z ) and a range limited previous difference survivor metric (DJ n-2 ), and for delivering a new difference survivor metric (DJ n ) ; means (81a) for limiting the value of a recent difference survivor metric (DJ n-1 ) to a range between +1 and -1 and for generating two intermediate binary decision values (b + n-1 and b n-1 ); and means (111) connected to the output of said adding means (103) for generating a binary output value (b ) re- presenting the sign of the new difference survivor metric (DJn).
Claim 12
Dependent Claim
81 words
Apparatus according to claim 7, characterized in that the inputs of said adding means (103) are connected to a sample input (z ) and, through a clocket register (101), to the output of said limiting means (81a), respectively, and said the output of said adding means (103) is connected through a clocket register (105) to the input of said limiting means (81a), so that output values can be generated for even and odd indexed sample values independently in a pipelined process.
References Cited (Backward Citations)
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