US 7,065,701 B2Granted

Method for iteratively decoding block turbo codes and recording medium for storing iterative decoding program of block turbo codes

AssigneeElectronics and Telecommunications Research Institute

InventorsSooyoung Kim, Woo-Seok Yang, Ho-Jin Lee

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Abstract

A method for iteratively decoding a block turbo code includes: receiving a signal frame formed of a product code obtained by serially concatenating block codes; forming a reliability array for signal demodulation and initializing extrinsic reliability information; performing a complexity-reduced soft decision output Viterbi decoding algorithm for all of the codewords existing on a current axis and calculating extrinsic reliability using soft decision output information output as a result of the decoding; checking whether an iterative decoding completion condition is satisfied, and outputting a decoded value and terminating an iterative decoding process when the condition is satisfied; and normalizing reliability information when the condition is not satisfied, performing reliability equalization, and repeating the decoding process for a next axis.

Claims12

Dependent claims

A method for iteratively decoding a block turbo code, comprising:

(a) receiving a signal frame formed of a product code, said product code being obtained by serially concatenating block codes transmitted from a transmission port;
(b) forming a reliability array for use as an input for signal demodulation and initializing extrinsic reliability information of the reliability array;
(c) performing a complexity-reduced soft decision output Viterbi decoding algorithm on all codewords existing on a current axis of the signal frame, and calculating extrinsic reliability information to be used in a next axis using soft decision output information output as a result of performing the complexity-reduced soft decision output Viterbi decoding;
(d) checking whether an iterative decoding completion condition is satisfied when the step (c) is completed, and outputting a decoded value to terminate the iterative decoding process when the iterative decoding completion condition is satisfied;
and
(e) normalizing the extrinsic reliability information calculated in the step (c) when the iterative decoding completion condition is not satisfied, performing reliability equalization work, and repeating the complexity-reduced soft decision output Viterbi decoding process for a next axis,
wherein the step (c) comprises:
(c1) calculating a ratio of a number of paths extended at a current point of time to a maximum number of paths and estimating a reference path metric using statistics of a path metric, when a total number of existing paths S of a trellis at the current point of time is larger than a maximum number of paths to be sustained, A;
(c2) assigning the reference path metric as a minimum path metric value at a current point of time, when the total number of existing paths of the trellis at the current point of time for the block code is smaller than the maximum number of paths to be sustained (S<A);
(c3) selecting a path having a better path metric than the reference path metric calculated in the step (c1);
(c4) assigning a reliability at a node at the current point of time as a difference value between the reference path metric calculated in step (c1) and the path metric of an automatically generated surviving path if reliability cannot be defined at the node;
and
(c5) comparing reliability at previous points of time with reliability assigned at the current point of time for the path assigned in the step (c4), and assigning the reliability at the previous points of time as a minimum value amongst them.

10 more elements

A method for iteratively decoding a block turbo code, comprising:

(a) receiving a signal frame formed of a product code, said product code being obtained by serially concatenating block codes transmitted from a transmission port;
(b) forming a reliability array for use as an input for signal demodulation and initializing extrinsic reliability information of the reliability array;
(c) performing a complexity-reduced soft decision output Viterbi decoding algorithm on all codewords existing on a current axis of the signal frame, and calculating extrinsic reliability information to be used in a next axis using soft decision output information output as a result of performing the complexity-reduced soft decision output Viterbi decoding;
(d) checking whether an iterative decoding completion condition is satisfied when the step (c) is completed, and outputting a decoded value to terminate the iterative decoding process when the iterative decoding completion condition is satisfied;
and
(e) normalizing the extrinsic reliability information calculated in the step (c) when the iterative decoding completion condition is not satisfied, performing reliability equalization work, and repeating the complexity-reduced soft decision output Viterbi decoding process for a next axis,
wherein the equalization of reliability in the step (e) comprises:
(e1) calculating an average avg1 of the extrinsic reliability value of an information-word part calculated in each codeword, and an average avg2 of the extrinsic reliability value of a parity-word part calculated in each codeword;
(e2) calculating a ratio (avg1/avg2) of an average of the reliability value of the parity-word part to the average of the reliability value of the information-word part;
and
(e3) comparing the ratio of the average of the reliability value with a threshold value, and performing an equalization process if it is determined to be needed.

8 more elements

A recording medium for storing an iterative decoding program of a block turbo code for storing a program executable by a computer so that an iterative decoding process is performed using a complexity-reduced SOVA for a product code of a block code, the recording medium comprising:

(a) program means for receiving a signal frame formed of a product code, said product code being obtained by serially concatenating block codes transmitted from a transmission port;
(b) program means for forming a reliability array for use as an input for signal demodulation and initializing extrinsic reliability information of the reliability array;
(c) program means for performing a complexity-reduced soft decision output Viterbi decoding algorithm on all codewords existing on a current axis of the signal frame, and calculating extrinsic reliability information to be used in a next axis using soft decision output information calculated as a result of the complexity-reduced soft decision output Viterbi decoding;
(d) program means for checking whether an iterative decoding completion condition is satisfied after performing the step (c), and outputting a decoded value to complete the iterative decoding process when the iterative decoding completion condition is satisfied;
and
(e) program means for normalizing the calculated extrinsic reliability information when the iterative decoding completion condition is not satisfied in (d), performing reliability equalization work, and repeating the complexity-reduced soft decision output Viterbi decoding process for a next axis,
wherein the step (c) comprises:
(c1) program means for calculating a ratio of a number of paths extended at a current point of time to a maximum number of paths and estimating a reference path metric using statistics of a path metric, when a total number of existing paths S of a trellis at the current point of time is larger than a maximum number of paths to be sustained, A;
(c2) program means for assigning the reference path metric as a minimum path metric value at a current point of time, when the total number of existing paths of the trellis at the current point of time for the block code is smaller than the maximum number of paths to be sustained (S<A);
(c3) program means for selecting a path having a better path metric than the reference path metric calculated in the step (c1);
(c4) program means for assigning a reliability at a node at the current point of time as a difference value between the reference path metric calculated in step (c1) and the path metric of an automatically generated surviving path if reliability cannot be defined at the node;
and
(c5) program means for comparing reliability at previous points of time with reliability assigned at the current point of time for the path assigned in the step (c4), and assigning the reliability at the previous points of time as a minimum value amongst them.

10 more elements

(a) program means for receiving a signal frame formed of a product code, said product code being obtained by serially concatenating block codes transmitted from a transmission port;
(b) program means for forming a reliability array for use as an input for signal demodulation and initializing extrinsic reliability information of the reliability array;
(c) program means for performing a complexity-reduced soft decision output Viterbi decoding algorithm on all codewords existing on a current axis of the signal frame, and calculating extrinsic reliability information to be used in a next axis using soft decision output information calculated as a result of the complexity-reduced soft decision output Viterbi decoding;
(d) program means for checking whether an iterative decoding completion condition is satisfied after performing the step (c), and outputting a decoded value to complete the iterative decoding process when the iterative decoding completion condition is satisfied;
and
(e) program means for normalizing the calculated extrinsic reliability information when the iterative decoding completion condition is not satisfied in (d), performing reliability equalization work, and repeating the complexity-reduced soft decision output Viterbi decoding process for a next axis,
wherein the equalization of reliability in the step (e) comprises:
(e1) program means for calculating an average avg1 of the extrinsic reliability value of an information-word part calculated in each codeword, and an average avg2 of the extrinsic reliability value of a parity-word part calculated in each codeword;
(e2) program means for calculating a ratio (avg1/avg2) of an average of the reliability value of the parity-word part to the average of the reliability value of the information-word part;
and
(e3) program means for comparing the ratio of the average of the reliability value with a threshold value, and performing an equalization process if it is determined to be needed.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/273,256Filed 18 Oct 2002
Priority: KR 2001-775988 Dec 2001
Published: US 2003/0110437 A112 Jun 2003
Granted: 20 Jun 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H03M 13/2963
Particular turbo code structure: turbo-block codes, i.e. turbo codes based on block codes, e.g. turbo decoding of product codes
G11B 20/1833
Error detection or correction; Testing , e.g. of drop-outs: by adding special lists or symbols to the coded information
H03M 13/4138
Using the Viterbi algorithm or Viterbi processors: soft-output Viterbi algorithm based decoding, i.e. Viterbi decoding with weighted decisions
H03M 13/658
Representation or format of variables, register sizes or word-lengths and quantization: scaling by multiplication or division