JP2008152915A - Read channel decoder, read channel decoding method and read channel decoding program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve error correction capability without increasing a circuit scale in an iterative read channel decoder having an inner decoder and an outer decoder.
Error correction correction units 110, 120, and 130 correct error corrections of DAE units 43, 45, and 47, respectively, and normalization units 141 to 144 have the best performance of LDPC units 151 to 154, respectively. The input information of the LDPC units 151 to 154 is normalized, and the decoding algorithm of the LDPC units 151 to 154 is changed so that the channel information is fully utilized. When the LDPC units 151 to 154 update the log likelihood ratio LLR (q _ji ), input prior information Λ _a (x _i ) that is channel information is always added.
[Selection] Figure 3

Description

  The present invention relates to a read channel decoder, a read channel decoding method, and a read channel decoding program for decoding data recorded after being encoded on a recording medium by repeating decoding by an inner decoder and decoding by an outer decoder. In particular, the present invention relates to a read channel decoder, a read channel decoding method, and a read channel decoding program that can prevent performance deterioration due to simplification of the inner decoder and increase error correction capability.

  The recording / reproducing apparatus is equipped with a powerful error correction function in order to reproduce the recorded signal without error. Only after this error correction can the recorded signal be reliably restored from an unstable signal containing noise.

  In recent years, error correction in a recording / reproducing apparatus has been realized mainly by a combination of two methods called PRML (Partial Response Maximum Likelihood) and ECC (Error Correcting Code). PRML is a scheme that regards a recording channel as a partial response channel (PR channel) having intersymbol interference and generally performs maximum likelihood detection using a Viterbi detector. On the other hand, the ECC corrects an error that cannot be corrected by the Viterbi detector, and a Reed-Solomon code is generally used. General explanations regarding Viterbi detectors and Reed-Solomon codes are given in many documents, for example, in Non-Patent Document 1.

  FIG. 4 is a functional block diagram showing a main configuration of a recording / reproducing system of a magnetic disk apparatus which is a typical example of the recording / reproducing apparatus. As shown in the figure, the recording / reproducing system of the magnetic disk device is roughly composed of a hard disk controller (HDC) 1, a read channel (RDC) 2 and a preamplifier 3.

  When recording data on a magnetic disk, first, a parity is added to the recording data by the CRC encoder 4 and the ECC encoder 5 in the HDC 1. Here, a CRC (Cyclic Redundancy Check) code is used to detect erroneous ECC correction.

  Next, the RDC 2 sends the recording data to the preamplifier 3 via the encoder 6, the recording compensator 7, and the driver 8. Here, the encoder 6 uses an RLL code or the like for stabilizing clock recovery by the PLL. In addition, the recording compensator 7 performs a compensation process that slightly widens the inversion interval at a position where the magnetization inversion is adjacent. Finally, the preamplifier 3 generates a write current to the recording head by the driver 9.

  On the other hand, when reproducing the data recorded on the magnetic disk, the analog voltage from the reproducing head is first amplified by the amplifier 10 and then sent to the RDC 2. The RDC 2 performs a conversion to a digital signal via a variable gain amplifier (VGA) 12, a low-pass filter (LPF) 13, and an AD converter (ADC) 14 after thermal asperity detection processing in the TA detection unit 11. After performing waveform equalization by the FIR filter 15, the decoder 16 performs Viterbi decoding.

  In the RDC 2, a PLL 17 that controls the timing for sampling the signal and an automatic gain controller (AGC) 18 that controls the gain of the variable gain amplifier 12 are also mounted.

  Then, the decoding result by the RDC 2 is returned to the HDC 1, and after error correction is performed by the ECC decoder 19 in the HDC 1, it becomes the reproduction data through the CRC checking unit 20.

  Further, turbo codes, low density parity codes (LDPC) and the like have been proposed as new codes / decoding schemes that replace the PRML scheme. These encoding / decoding methods are collectively referred to herein as iterative methods because they are decoded by iterative calculation. A typical example of the iterative method is a turbo code disclosed in Patent Document 1.

  The turbo code is a parallel concatenation code in which two recursive systematic convolutional codes (RSC) are connected via a random interleaver, and decoding is an iterative calculation using two decoders. Do by.

  Although the turbo code was devised in the field of communication, Non-Patent Document 2 discloses a plurality of systems in which this is applied to the PR channel of the recording / reproducing system. FIG. 5 is a functional block diagram showing a configuration of an encoder and a decoder when a turbo code is applied to a PR channel of a recording / reproducing system.

  As shown in FIG. 5A, when the turbo code is applied to the PR channel of the recording / reproducing system, the encoder uses two element encoders (constituent encoders) 21 and 23 as random interleavers 22 (in FIG. 5, π To display a serial concatenation. At this time, the encoder close to the channel is called an inner encoder, and the other is called an outer encoder.

  In fact, in the PR channel, since the channel itself can be regarded as a convolutional encoder, the inner encoder 23 does not need to be clearly provided. However, a complementary encoder called a precoder may be used to make a recursive systematic convolutional code.

  Various types of outer encoders 21 have been proposed, such as those using two RSCs and those using one RSC. Further, there are cases where the LDPC disclosed in Non-Patent Document 3 is used, or the product code (TPC: Turbo Product Code) shown in Non-Patent Document 4 is used.

  On the other hand, as shown in FIG. 5B, the iterative decoder is composed of two element decoders called an inner decoder 24 and an outer decoder 26. The inner decoder 24 performs decoding corresponding to the inner encoder 23, and the outer decoder 26 performs decoding corresponding to the outer encoder 21. Further, the inner decoder 24 may be called a channel decoder.

  A characteristic point of the iterative method is that it performs maximum a posteriori probability (MAP) decoding. Therefore, both of the two element decoders are soft input / soft output (SISO). Soft-Out) Decoder. Here, the SISO decoder is a decoder that outputs reliability information such as 0.4 or 0.9 instead of outputting a hard decision result such as 0 or 1.

で表現される。ただし、

である。 For example, the inner decoder calculates the posterior probability of the information symbol x _k before encoding under the condition that the read signal sequence y _k (k = 1 to N) from the channel is given, and the posterior probability Is the total probability information that is the log-likelihood ratio (LLR) of the probability that x _k is 1 and the probability that x _k is 0

It is expressed by However,

It is.

Further, prior information Λ _a (x _k ) obtained prior to decoding is also input to the inner decoder in the form of log likelihood ratio. The inner decoder calculates total probability information Λ (x _k ) in the equation (1) from the prior information Λ _a (x _k ) and the read signal sequence y _k . Also, extrinsic information obtained by subtracting prior information Λ _a (x _k ) from total probability information Λ (x _k )

Λ _e (x _k ) = Λ (x _k ) −Λ _a (x _k )
And the external information Λ _e (x _k ) is transmitted to the other decoder.

Here, the decoding procedure will be described with reference to FIG. The read signal sequence y _k first enters the inner decoder 24. The inner decoder 24 calculates and outputs the external information Λ _e (x _k ) from the read signal sequence y _k and the prior information Λ _a (x _k ) output from the outer decoder 26. The output external information Λ _e (x _k ) becomes channel information Λ _a (x ′ _k ) of the outer decoder via the deinterleaver 25 (shown in FIG. 5).

The outer decoder 26 outputs all information probabilities Λ (u _k ) and external information Λ _e (x ′ _k ) of the information sequence from the channel information Λ _a (x ′ _k ). This external information Λ _e (x ′ _k ) is again used as the prior information Λ _a (x _k ) of the inner decoder 24 via the interleaver 27 (indicated as π in FIG. 5).

Then, after the processes of the inner decoder 24 and the outer decoder 26 are repeated a predetermined number of times, the determination unit 28 performs threshold processing on the total probability information Λ (u _k ) output from the outer decoder 26. Decoding is achieved.

  Here, as a specific calculation method of SISO decoding for codes defined by state transitions such as convolutional codes, there is a BCJR algorithm, which is described in detail in Non-Patent Document 5. In general, the BCJR algorithm is used for both the inner encoder and the outer encoder. However, when an LDPC code is used as the outer encoder, the sum-product method introduced in Non-Patent Document 6 is used. In addition, Non-Patent Document 6 describes a general description of the iterative method. These iterative methods have a higher error correction capability than the PRML method, and are regarded as promising as next-generation encoding methods.

  However, the iterative method has a drawback that the circuit scale increases in proportion to the number of iterations. This is due to the fact that it is difficult to repeatedly use the same circuit when the data transfer rate is high, and therefore, the circuit for the number of repetitions is mounted.

  FIG. 6 is a functional block diagram showing a configuration of an iterative read channel decoder. Here, the interleaver and the deinterleaver are assumed to be included in the outer decoder.

  As shown in the figure, in this read channel decoder 30, since the number of iterations is four, 31-38 inner / outer decoders are required, and when a decoder based on the BCJR algorithm is used as the inner decoder, The circuit scale becomes very large.

  As a countermeasure, Non-Patent Document 6 introduces a method using simplified DAE (Decision Aided Equalization) as an inner decoder. FIG. 7 is a diagram showing a configuration of a read channel decoder using DAE. As shown in the figure, the read channel decoder 40 includes a BCJR unit 41, DAE units 43, 45 and 47, LDPC units 42 to 48, and a determination unit 49.

The BCJR unit 41 is an inner decoder using the BCJR algorithm, and calculates and outputs external information Λ _e (x _k ) from the read signal sequence y _k . Like the read channel decoder 40, when the DAE method is used as a simplified inner decoder, accuracy is required for the input prior information. Therefore, the inner decoder using the BCJR algorithm or the like is used at the first iteration. Is used.

The DAE units 43, 45 and 47 are inner decoders using the DAE method, and calculate and output external information Λ _e (x _k ) from the read signal sequence y _k and the prior information Λ _a (x _k ). The external information Λ _e (x _k ) is prior information input by the LDPC units 42 to 48.

The LDPC units 42 to 48 are outer decoders using LDPC as outer codes, and calculate external information using the external information Λ _e (x _k ) output from the DAE units 43, 45, and 47 as prior information. This external information becomes prior information Λ _a (x _k ) of the next inner decoder.

The determination unit 49 is a processing unit that frequently processes the total probability information Λ (u _k ). Specifically, when the total probability information Λ (u _k ) is negative, 0 is determined, and the total probability information Λ ( If u _k ) is positive, 1 is output.

  As described above, the read channel decoder 40 uses a decoder using the DAE method for the inner decoder, thereby preventing an increase in circuit scale, which is a drawback of the iterative method.

When LDPC is used as the outer code, a decoder using the sum-product method introduced in Non-Patent Document 6 is used as the outer decoder. In the decoder using this sum-product method, the check matrix M is j × i, the log likelihood ratio from bit to check is LLR (q _ji ), and the log likelihood ratio from check to bit is LLR (r _ji ), If the total probability information is Λ (x _i ), the input prior information Λ _a (x _k ) and the output external information Λ _e (x _k ) are repeatedly calculated using the decoding algorithm shown in FIG.

FIG. 8 is a flowchart showing the decoding algorithm of the decoder using the sum-product method, that is, the processing procedure of the LDPC units 42 to 48 shown in FIG. As shown in the figure, the LDPC units 42 to 48 first initialize the log likelihood ratio LLR (q _ji ) from bit to check with input prior information Λ _a (x _k ) that is channel information. That is, LLR (q _ji ) = Λ _a (x _i ) is set (step S801).

ここで、

である。 Then, using the log-likelihood ratio LLR (q _ji ) from bit to check, the log-likelihood ratio LLR (r _ji ) from check to bit is updated as in equation (2) (step S802).

here,

It is.

Then, using the log-likelihood ratio LLR (r _ji ) from check to bit and the input prior information Λ _a (x _i ), the total probability information Λ (x _i ) is obtained as in equation (3) (step S803). .

Then, for the next iteration, the output external information Λ _e (x _i ) and the log-likelihood ratio LLR (q _ji ) from bit to check are updated as in equations (4) and (5) (step S804). ).

  Then, it is checked whether or not the above-described processing has been executed a predetermined number of times (step S805). If the predetermined number of times has not been executed, the processing returns to step S802 and the above-described processing is repeated. On the other hand, when the above-described process is executed a predetermined number of times, the decoding process is terminated.

US Pat. No. 5,446,747 (page 10, FIG. 1) S. Lin and DJ Costelo, Jr., "Error control coding: fundamentals and applications", Prentis・ Prentice-Hall, 1983 "Turbo Decoding for PR4: Parallel Versus Serial Concatenation" by T. Souvignier et al., Proceeding ITriple International Conference on Communications (Proc. IEEE Int. Conf. On Communications), 1999, p. 1638-1642 RG Gallager, "Low-Density Parity-Check Codes", Cambridge, Massachusetts (MA): MIT Press 1963, p. 47-69 RM Pyndiah, “Near-optimum decoding of product codes: block turbo codes”, iTriple E Transactions on Communications (IEEE Trans. On Communications), 1998, Vol. 46, No. 8, p. 1003-1010 LR Bahl et al., “Optimal decoding of linear codes for minimizing symbol error rate” I Triple E Transactions Information Theory, 1974, Vol. 20, p. 248-87 Z. Wu, “Coding and iterative detection for magnetic recording channels”, Kluwer Academic Publishers 2000, p. 71-87

  However, if the decoding algorithm of the inner decoder is simplified by using DAE instead of BCJR like the read channel decoder 40, there is a problem that the performance of the inner decoder is deteriorated.

Also, in LDPC used for the outer decoder, the input prior information Λ _a (x _i ) that is channel information is used only for initialization of LLR (q _ji ), so that it is output to the inner decoder after the second iteration. There is a problem that the channel information is not utilized in the output external information Λ _e (x _i ).

  The present invention has been made in order to solve the above-described problems caused by the prior art, and prevents a deterioration in performance due to the simplification of the inner decoder and improves the error correction capability. An object is to provide a channel decoding method and a read channel decoding program.

  In order to solve the above-described problems and achieve the object, the present invention provides a read channel decoder that decodes data encoded and recorded on a recording medium, and is based on a signal sequence read from the recording medium. An inner decoding means for generating information relating to data decoding reliability as external information, and decoding using a low-density parity code, and calculating information relating to the data decoding reliability by a decoding process using iterative calculation And outer decoding means that uses the external information generated by the inner decoding means for each iterative calculation during one decoding process.

  The present invention is also a read channel decoding method for decoding data recorded after being encoded on a recording medium, wherein information relating to reliability of decoding of the data based on a signal sequence read from the recording medium is external information. And the external information generated by the inner decoding step when the information about the reliability of decoding of the data is calculated by the decoding process using iterative calculation. And an outer decoding step that is used for each iterative calculation during one decoding process.

  Further, the present invention is a read channel decoding program for decoding data recorded after being encoded on a recording medium, wherein information relating to reliability of decoding of the data based on a signal sequence read from the recording medium is external information And the external information generated by the inner decoding procedure when the information about the reliability of decoding of the data is calculated by the decoding process using the iterative calculation. And an outer decoding procedure that is used for each iterative calculation during one decoding process.

  According to the present invention, information relating to the reliability of data decoding is generated as external information based on the signal sequence read from the recording medium, decoding using a low-density parity code is performed, and information relating to the reliability of data decoding is obtained. Since the external information generated at the time of calculation by the decoding process using iterative calculation is used for each iterative calculation during one decoding process, the error correction capability can be improved.

  Exemplary embodiments of a read channel decoder, a read channel decoding method, and a read channel decoding program according to the present invention will be explained below in detail with reference to the accompanying drawings.

  First, the configuration of the read channel decoder according to the present embodiment will be described. FIG. 1 is a functional block diagram showing the configuration of the read channel decoder according to the present embodiment. Here, for convenience of explanation, functional units that play the same functions as the respective units of the read channel decoder 40 shown in FIG.

  As shown in the figure, this read channel decoder 100 includes a BCJR unit 41, three DAE units 43, 45 and 47, three error correction correction units 110, 120 and 130, and four normalization units 141. 144, four LDPC units 151-154, and a determination unit 49.

The error correction correction units 110, 120, and 130 are processing units that correct the output external information Λ _e (x _k ) of the DAE units 43, 45, and 47, respectively, and the input prior information Λ _a of the DAE units 43, 45, and 47, respectively. Correction is performed based on (x _k ) and output external information Λ _e (x _k ). Since these error correction correction units 110, 120, and 130 all have the same configuration, the following description will be made taking the error correction correction unit 110 as an example.

In the DAE method, the read signal sequence: y _{i: i = k + 1 to k +} μ and the prior information Λ _a (x _{i: i} External information Λ _e (x _k ) is calculated and output using _{= k−} μ _{~ k +} μ _{, i} ≠ _k ). Here, if the sign of the output external information Λ _e (x _k ) is inverted with respect to the input prior information Λ _a (x _k ), correction is performed by DAE.

  Therefore, the error correction correction unit 110 detects whether or not the correction is correct, and performs correction processing when the error correction is correct. FIG. 2 is a functional block diagram showing the configuration of the error correction correction unit 110 shown in FIG.

As shown in FIG. 5A, the error correction correction unit 110 includes a DELAY 111, a detection unit 112, and a correction unit 113. The DELAY 111 is a processing unit that delays the input advance information Λ _a (x _k ) by the DAE processing time, and the detection unit 112 is generated by the input advance information Λ _a (x _k ) delayed by the DELAY 111 and the DAE unit 43. This processing unit detects erroneous correction using the output external information Λ _e (x _k ). The correction unit 113 is a processing unit that corrects the output external information Λ _e (x _k ) generated by the DAE unit 43 when the detection unit 112 detects an erroneous correction.

FIG. 6B is a diagram showing details of the detection unit 112. As shown in FIG. 5B, the detection unit 112 detects correction by exclusive OR (EOR) of codes of Λ _a (x _k ) and Λ _e (x _k ). In addition, if the absolute value of the output external information Λ _e (x _k ) is smaller than the absolute value of the input prior information Λ _a (x _k ), it is determined to be erroneous correction. Therefore, the comparator | Λ _a (x _k ) |> | Λ _e (x _k ) | is detected, and the result of correction detection and logical product (AND) are used as detection results.

FIG. 8C is a diagram illustrating an example of the configuration of the correction unit 113. As shown in FIG. 6C, the correction unit 113 outputs the output external information Λ _e (x _k ) as it is based on the detection result if it is not erroneous correction, and an indefinite value ( 0) is output. FIG. 6D is a diagram showing another example of the configuration of the correction unit 113. Based on the detection result, the output external information Λ _e (x _k ) is output as it is when the correction is not an error, and the error correction is performed. In the case of, the sign of the output external information Λ _e (x _k ) is inverted and output.

As described above, the error correction correction unit 110 detects whether or not the output external information Λ _e (x _k ) generated by the DAE unit 43 has been erroneously corrected. When the error correction is detected, the output external information Λ _Since the value of _e (x _k ) is corrected, the error correction capability of the read channel decoder 100 can be enhanced.

  The normalization units 141 to 144 are processing units that perform normalization processing according to the output distribution of the BCJR unit 41 and the DAE units 43, 45, and 47. Generally, the outer decoder has an input distribution with the best performance, and the performance of the outer decoder can be improved by performing a normalization process according to the output distribution of the inner decoder.

Therefore, normalization processing is performed as Λ _e (x _k ) = Λ _e (x _k ) × A / M based on the maximum absolute value M of the inner decoder and the normalized value A. Here, A can be obtained by an algorithm used for the inner decoder, or can be obtained by an experiment in advance from a mounted real circuit. In addition, the normalization unit 141 uses values different from the normalization units 142 to 144 as the values of A and M in order to normalize the output of the BCJR unit 41.

  As described above, the normalization units 141 to 144 perform the normalization process according to the output distribution of the BCJR unit 41 and the DAE units 43, 45, and 47, so that the performance of the outer decoder is improved and the read channel decoding is performed. The error correction capability of the device 100 can be increased.

  LDPC units 151 to 154 are outer decoders using LDPC as outer codes. However, these LDPC units 151 to 154 perform decoding using a decoding algorithm different from that of the LDPC units 42 to 48 as described below.

FIG. 3 is a flowchart showing the processing procedure of the decoding process of the LDPC units 151-154. As shown in the figure, these LDPC units 151 to 154 first initialize the log-likelihood ratio LLR (q _ji ) from bit to check with 0. That is, LLR (q _ji ) = 0 is set (step S301).

ここで、

である。 Then, the log likelihood ratio LLR (q _ji ) from bit to check is updated by adding the input prior information Λ _a (x _i ) which is channel information (step S302), and this updated log likelihood ratio LLR Using (q _ji ), the log likelihood ratio LLR (r _ji ) from check to bit is updated as in equation (6) (step S303).

here,

It is.

Then, using the log-likelihood ratio LLR (r _ji ) from check to bit and the input prior information Λ _a (x _i ), the total probability information Λ (x _i ) is obtained as in equation (7) (step S304). .

Then, for the next iteration, the output external information Λ _e (x _i ) and the log-likelihood ratio LLR (q _ji ) from bit to check are updated as in equations (8) and (9) (step S305). ).

  Then, it is checked whether or not the above-described process has been executed a predetermined number of times (step S306). If the predetermined process has not been executed, the process returns to step S302 and the above-described process is repeated. On the other hand, when the above-described process is executed a predetermined number of times, the decoding process is terminated.

As described above, since the LDPC units 151 to 154 always add the input prior information Λ _a (x _i ) that is channel information when updating the log likelihood ratio LLR (q _ji ), the external information is calculated. In some cases, channel information is utilized, and the error correction capability of the read channel decoder 100 can be enhanced. Also, by substituting equation (7) into equations (8) and (9), the calculation processing of the input prior information Λ _a (x _i ) is canceled out, so that the amount of calculation is equivalent to the conventional algorithm.

  As described above, in this embodiment, the error correction correction units 110, 120, and 130 correct the error correction of the DAE units 43, 45, and 47, respectively, and the normalization units 141 to 144 are the LDPC units 151 to 154, respectively. The input information of the LDPC units 151 to 154 is normalized so that the performance of the LDPC units 151 to 154 is optimized, and the decoding algorithm of the LDPC units 151 to 154 is changed so that the channel information is fully utilized. It is possible to prevent performance degradation due to use, and to improve the error correction capability of the read channel decoder 100.

  In this embodiment, the read channel decoder 100 including the error correction correction units 110 to 130, the normalization units 141 to 144, and the LDPC units 151 to 154 has been described. However, it is necessary to use all of these functional units. Alternatively, some of these functional units can be used.

  For example, it is possible to use only the error correction correction units 110 to 130, the LDPC unit to use a conventional decoding algorithm, only the normalization units 141 to 144, and the LDPC unit to use a conventional decoding algorithm Is possible. It is also possible to use the LDPC units 151 to 154 and not use the error correction correction units 110 to 130 and the normalization units 141 to 144. Furthermore, it is also possible to implement the present invention only for specific repetitive parts, such as using only the error correction correction unit 110 and not using the error correction correction units 120 and 130.

  In this embodiment, the read channel decoder has been described. However, a read channel decoding program having the same function can be obtained by realizing the configuration of the read channel decoder by software. Therefore, a computer system that executes these read channel decoding programs will be described.

  FIG. 9 is a diagram illustrating an example of a computer system 900 that executes a read channel decoding program. As shown in the figure, the computer system 900 includes an MPU (Micro Processing Unit) 901, a ROM (Read Only Memory) 902, a RAM (Random Access Memory) 903, an input / output unit 904, and a PC interface 905. Have

  The MPU 901 is an arithmetic device that executes a program. Here, the MPU 901 executes a read channel decoding program stored in the ROM 902. The ROM 902 is a memory that stores a read-only program and data, and stores a read channel decoding program prior to execution of the program.

  The RAM 903 is a memory in which data can be written, and stores temporary data and the like created by the MPU 901 when the program is executed. The input / output unit 904 is a processing unit that exchanges data with the outside.

  The PC interface 905 is an interface with a personal computer used for program development and the like, and is used for loading of a program developed by the personal computer, exchange of debug information with the personal computer, and the like.

(Appendix 1) A read channel decoder that decodes data encoded and recorded on a recording medium by repeating decoding by an inner decoder and decoding by an outer decoder,
A read channel decoder, comprising: correcting means for correcting the output information based on input information and output information of the inner decoder to generate input information to the outer decoder.

(Supplementary note 2) The read channel decoder according to supplementary note 1, further comprising normalization means for normalizing input information to the outer decoder in accordance with a distribution of output information of the inner decoder.

(Supplementary Note 3) The outer decoder performs decoding using a low-density parity code, and calculates input information about the reliability of decoding of the data by iterative calculation. The read channel decoder according to appendix 1 or 2, wherein

(Supplementary Note 4) The correction means includes detection means for detecting an error correction of the inner decoder based on input information and output information of the inner decoder, and inner decoding based on the error correction detected by the detection means. The read channel decoder according to appendix 1, 2 or 3, further comprising correction means for correcting output information of the detector and generating input information to the outer decoder.

(Supplementary note 5) The read channel decoder according to supplementary note 4, wherein the detecting means detects an erroneous correction of the inner decoder by comparing input information and output information of the inner decoder.

(Supplementary note 6) The read channel decoder according to supplementary note 4, wherein the correction means corrects the output information of the inner decoder as indefinite when an erroneous correction is detected by the detection means.

(Supplementary note 7) The supplementary note 4, wherein the correction means corrects the output information by inverting the sign of the output information of the inner decoder when an erroneous correction is detected by the detection means. Read channel decoder.

(Supplementary note 8) A read channel decoder for decoding data encoded and recorded on a recording medium by repeating decoding by an inner decoder and decoding by an outer decoder,
A read channel decoder, comprising: normalization means for normalizing input information to the outer decoder according to a distribution of output information of the inner decoder.

(Supplementary note 9) A read channel decoder for decoding data encoded and recorded on a recording medium,
Inner decoding means for generating, as external information, information relating to the reliability of decoding of the data based on a signal sequence read from the recording medium;
An outer decoding unit that performs decoding using a low-density parity code and uses the external information generated by the inner decoding unit for each iteration calculation when calculating information on the reliability of decoding of the data by iterative calculation; ,
A read channel decoder comprising:

(Supplementary note 10) An iterative decoder for decoding data by repeating decoding by an inner decoder and decoding by an outer decoder,
An iterative decoder comprising correction means for correcting the output information based on input information and output information of the inner decoder to generate input information to the outer decoder.

(Supplementary note 11) A read channel decoding method for decoding data encoded and recorded on a recording medium by repeating decoding by an inner decoding step and decoding by an outer decoding step,
A read channel decoding method comprising: a correction step of correcting the output information based on input information and output information of the inner decoding step to generate input information to the outer decoding step.

(Supplementary note 12) The read channel decoding method according to supplementary note 11, further comprising a normalization step of normalizing input information to the outer decoding step according to a distribution of output information of the inner decoding step.

(Supplementary note 13) In the outer decoding step, decoding is performed using a low-density parity code, and input information of the outer decoding step is calculated for each iteration calculation when calculating information related to the decoding reliability of the data by iteration calculation. The read channel decoding method according to appendix 11 or 12, wherein the read channel decoding method is used.

(Supplementary Note 14) The correction step includes a detection step of detecting an erroneous correction of the inner decoding step based on input information and output information of the inner decoding step, and an inner decoding based on the erroneous correction detected by the detection step. 14. The read channel decoding method according to appendix 11, 12 or 13, further comprising: a correction step of correcting output information of the step and generating input information to the outer decoding step.

(Supplementary note 15) The read channel decoding method according to supplementary note 14, wherein the detection step detects an erroneous correction of the inner decoding step by comparing input information and output information of the inner decoding step.

(Supplementary Note 16) A read channel decoding program for decoding data recorded after being encoded on a recording medium by repeating decoding by an inner decoding procedure and decoding by an outer decoding procedure,
A read channel decoding program, wherein a correction procedure for correcting the output information based on the input information and output information of the inner decoding procedure to generate input information for the outer decoding procedure is executed by a computer.

(Supplementary note 17) The read channel decoding according to supplementary note 16, wherein a normalization procedure for normalizing input information to the outer decoding procedure in accordance with a distribution of output information of the inner decoding procedure is further executed by a computer program.

(Supplementary Note 18) In the outer decoding procedure, decoding is performed using a low-density parity code, and input information of the outer decoding procedure is calculated for each iteration calculation when calculating information regarding the reliability of decoding of the data by iteration calculation. 18. The read channel decoding program according to appendix 16 or 17, characterized by being used for

(Supplementary note 19) The correction procedure includes a detection procedure for detecting an erroneous correction of the inner decoding procedure based on input information and output information of the inner decoding procedure, and an inner decoding based on the erroneous correction detected by the detection procedure. The read channel decoding program according to appendix 16, 17 or 18, wherein a correction procedure for correcting output information of the procedure and generating input information for the outer decoding procedure is executed by a computer.

(Supplementary note 20) The read channel decoding program according to supplementary note 19, wherein the detection procedure detects an erroneous correction of the inner decoding procedure by comparing input information and output information of the inner decoding procedure.

It is a functional block diagram which shows the structure of the read channel decoder which concerns on this Embodiment. It is a functional block diagram which shows the structure of the error correction correction | amendment part shown in FIG. It is a flowchart which shows the process sequence of the decoding process of a LDPC part. It is a functional block diagram which shows the main structures of the recording / reproducing system of a magnetic disc apparatus. It is a functional block diagram which shows the structure of the encoder and decoder in the case of applying a turbo code to PR channel of a recording / reproducing system. It is a functional block diagram which shows the structure of an iterative read channel decoder. It is a figure which shows the structure of the read channel decoder using DAE. It is a flowchart which shows the process sequence of the LDPC part shown in FIG. It is a figure which shows the computer system which concerns on this Embodiment.

Explanation of symbols

1 HDC
2 RDC
3 Preamplifier 4 CRC Encoder 5 ECC Encoder 6 Encoder 7 Recording Compensator 8, 9 Driver 10 Amplifier 11 TA Detector 12 VGA
13 LPF
14 ADC
15 FIR
16 Decoder 17 PLL
18 AGC
19 ECC Decoder 20 CRC Checking Unit 21 Outer Encoder 22, 27 Random Interleaver 23 Inner Encoder 24, 31, 33, 35, 37 Inner Decoder 25 Inverse Interleaver 26, 32, 34, 36, 38 Outer Decoder 28, 39, 49 Judgment unit 30, 40, 100 Read channel decoder 41 BCJR unit 42, 44, 46, 48, 151, 152, 153, 154 LDPC unit 43, 45, 47 DAE unit 110, 120, 130 Error correction Correction unit 111 DELAY
112 detection unit 113 correction unit 141, 142, 143, 144 normalization unit 900 computer system 901 MPU
902 ROM
903 RAM
904 Input / output unit 905 PC interface

Claims (3)

A read channel decoder for decoding data encoded and recorded on a recording medium,
Inner decoding means for generating, as external information, information relating to the reliability of decoding of the data based on a signal sequence read from the recording medium;
Decoding using a low density parity code, external information generated by the inner decoding means when calculating information related to the reliability of decoding of the data by decoding using iterative calculation is performed in one decoding process. An outer decoding means used for each iterative calculation;
A read channel decoder comprising: A read channel decoding method for decoding data encoded and recorded on a recording medium,
An inner decoding step for generating, as external information, information on reliability of decoding of the data based on a signal sequence read from the recording medium;
Performing decoding using a low-density parity code, and calculating external information generated by the inner decoding step when calculating information related to the reliability of decoding of the data by decoding using iterative calculation. An outer decoding step used for each iterative calculation;
The read channel decoding method characterized by including. A read channel decoding program for decoding data encoded and recorded on a recording medium,
An inner decoding procedure for generating, as external information, information on reliability of decoding of the data based on a signal sequence read from the recording medium;
Performing decoding using a low-density parity code, and calculating external information generated by the inner decoding procedure when calculating information related to the reliability of decoding of the data by decoding using iterative calculation. An outer decoding procedure used for each iterative calculation;
A read channel decoding program that causes a computer to execute.

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