KR20080085943A - Method for repetition modulation/demodulation using low density parity check code and apparatus for optical information recoding/reproducing by using the same - Google Patents

Abstract

A repetitive modulation/demodulation method using a low density parity check code and an optical information recoding/reproducing apparatus using the method are provided to improve a decoding performance by repeatedly executing demodulation and LDPC(Low Density Parity Check) decoding during reproduction of optical information. A repetitive modulation/demodulation method using a low density parity check code comprises an initial probability information calculating step(S110) of calculating initial probability by demodulating a data page; a simulated output data generating step(S120) of generating simulated output data by executing LDPC decoding using the initial probability information; an integrity testing step(S130) of testing the integrity of the simulated output data; a data output step of outputting the modulated output data if the integrity of the simulated output data is not abnormal; and a repetitive decoding step of executing LDPC decoding by re-calculating the initial probability information by re-modulating the simulated output data if the integrity of the simulated output data is abnormal.

Description

Method for repetition modulation / demodulation using low density parity check code and apparatus for optical information recoding / reproducing by using the same}

1 is a block diagram showing an optical information recording / reproducing apparatus according to the present invention.

2 is a block diagram showing modulation of optical information by the optical information recording / reproducing apparatus according to the present invention.

3 is a block diagram showing demodulation of optical information by the optical information recording / reproducing apparatus according to the present invention.

4 is a flowchart showing an optical information demodulation process by the optical information recording / reproducing apparatus according to the present invention.

5 is a graph illustrating an error rate due to encoding of a 2: 4 modulation code according to the present invention.

** Explanation of symbols in main part of drawing **

100: optical information recording / playback

110: light source

120: light splitter

130: multiplexer

140: spatial light modulator

150: optical information detector

170: input data processing unit

180: output data processing unit

The present invention relates to an iterative modulation and demodulation method using a low density parity check code and an optical information recording / reproducing apparatus using the same, and more particularly, to a low-density parity check code in an optical information recording / reproducing apparatus. Repeated modulation and demodulation method using a low density parity check code to improve the decoding performance by repeatedly performing demodulation and LDPC decoding when reproducing optical information using " LDPC " It is about.

Optical information processing apparatuses for processing optical information include compact discs (CDs), digital versatile discs (DVDs), HD-DVDs, Blu-ray discs, near field optical processing apparatuses, and the like. Recently, as the demand for the next generation storage system having a large capacity is increased, the optical information processing apparatus using holography has been attracting attention.

An optical information processing apparatus using holography superimposes an information beam and a reference beam including image information of input data onto an optical information recording medium and irradiates an interference pattern resulting from the interference pattern. Is recorded on the optical information recording medium.

In order to reproduce the recorded optical information, when the reference light is irradiated onto the optical information recording medium, the reference light is diffracted by the interference pattern to generate the reproduced light. If the recording reference light and the reproduction reference light are the same, reproduction light containing the same optical information as the optical information included in the signal light during recording is generated.

On the other hand, the image of the data page reproduced by the reproduction light is detected through a light receiving array element such as a complementary metal-oxide semiconductor (CMOS) or a charge coupled device (CCD). The detected data page is restored to output data through a series of demodulation and decoding processes.

In the case of reproducing holographic digital data from a recording medium, a signal reproduced by the intensity of laser light as a light source, distortion caused by a lens, scattering in the system, and various factors has an overall distribution of intensity.

Moreover, the reference light having Gaussian distribution has little reproduction error rate since it exhibits a certain level of light intensity in the center area of the reproduced data page, but the reproduction error rate is abrupt because the light timing is lower than a certain level in the corner area of the data page. There has been a growing problem.

The most common method of decoding holographic digital data from data reproduced on a recording medium is by using a threshold value, which uses an average or 0.5 value of each pixel and a threshold value of a local page. It is divided in a manner.

In the case of the former (using a threshold value), if the average or the value of the pixel is larger than 0.5, it is read as 1, and if it is smaller than that, it is read as 0.

In this case, however, the code rate is high, but the reproduction error rate (particularly, the reproduction error rate at the corners of the page) is very high.

On the other hand, in the latter case (using a local threshold), a playback signal of one page is divided into several regions, and different threshold values are applied to each divided region, i.e., the closer to the center of the page, the higher the threshold value is. In this case, 1 and 0 are determined by applying a relatively low threshold value as the distance from the center of the page (the closer to the edge).

However, this method has the advantage of high code rate and low reproduction error rate, but has a problem of incompatibility between various systems when the noise pattern is different.

Accordingly, methods for reducing the reproduction error rate have been developed. Recently, in addition to 2: 4 balanced modulation code conversion or 6: 8 balanced modulation code conversion, a method of modulating and demodulating data using an LDPC decoder has been developed. It is used.

Accordingly, the development of various modulation and demodulation methods using balanced modulation code conversion and LDPC codes has emerged, and an optical information processing device and optical information that can further improve the accuracy of demodulated data using balanced modulation code conversion and LDPC codes The development of a treatment method is required.

The present invention has been made to solve the above problems, iterative modulation and demodulation method using a low-density parity check code to improve the decoding performance by repeatedly performing modulation and LDPC decoding during optical information reproduction, and using the same An object thereof is to provide an optical information recording / reproducing apparatus.

In the repeated modulation and demodulation method using the low density parity check code according to the present invention for achieving the above object, in the demodulation method of the data page detected by the optical information recording / reproducing apparatus, demodulating the data page to obtain the initial probability information Calculating initial probability information calculating step, generating mock output data by performing LDPC decoding using the initial probability information, generating a mock output data, integrity checking step of checking the integrity of the mock output data, A data output step of outputting the simulated output data when there is no abnormality in the integrity, and repetitive modulation of the simulated output data when the integrity of the simulated output data is abnormal to calculate the initial probability information again to perform LDPC decoding Decoding step.

The iterative decoding step may include: generating a virtual data page for the simulated output data by virtually modulating the simulated output data, identifying pixel position information of the virtual data page, and according to the pixel position information. Changing pixel information of a data page, demodulating the data page with changed pixel information to recalculate initial probability information, and performing LDPC decoding using the calculated initial probability information to generate simulated output data And, it is preferable to include the step of performing the integrity check step again.

In the integrity check step, it is preferable to perform a parity check on the simulated output data.

The pixel information may be location information of an on pixel of a virtual data page generated by virtually modulating the simulation output data.

An optical information recording / reproducing apparatus using a low density parity check code according to the present invention for achieving the above object includes a light source, an optical splitter for separating light emitted from the light source into reference light and signal light, and loading data into the signal light. A spatial light modulator, a detector for detecting reproduction light reproduced on a recording medium by the reference light, and encoding the data into the LDPC and modulating the encoded data through balanced modulation code conversion to generate a data page. And an input data processor for providing the generated data page to the spatial light modulator and the data page detected by the detector to calculate initial probability information and perform LDPC decoding using the initial probability information. Simulated output data when the integrity of the simulated output data is abnormal Through the modulation of the iterative decoding and a data output processing unit that changes the page data to generate output data.

Preferably, the input data processor includes an LDPC encoder for converting the data to perform LDPC encoding, and a modulator for modulating the data encoded by the LDPC encoder by balanced modulation code conversion.

The output data processor includes a demodulator for demodulating data pages detected by the optical information detector to calculate initial probability information of the data pages, and generating simulated output data through LDPC decoding using the initial probability information. LDPC decoder that outputs output data according to the integrity state of the simulated output data, and if there is an abnormality in the integrity of the simulated output data, a virtual data page is generated using the simulated output data, and the position information of the pixel is calculated. And a data page processor for changing the pixel information of the data page according to the position information of the pixel calculated by the virtual modulator and providing the changed data page to the demodulator.

The LDPC decoder may perform parity check on the simulated output data and convert the simulated output data into output data when the simulated output data has no integrity.

The pixel information may be on pixel position information of a virtual data page generated by virtually modulating the simulation output data.

The optical information reproducing apparatus using the low density parity check code according to the present invention for achieving the above object comprises a light source for emitting light, a detector for detecting the reproduction light reproduced on the recording medium by the light, Initial probability information is calculated by demodulating the data page detected by the detector, and LDPC decoding is performed using the initial probability information, and if the integrity of the generated simulated output data is abnormal, modulation and iterative decoding by the simulated output data is performed. It is provided with an output data processing unit for generating the output data by changing the data page through.

The output data processor includes a demodulator for demodulating data pages detected by the optical information detector to calculate initial probability information of the data pages, and generating simulated output data through LDPC decoding using the initial probability information. LDPC decoder that outputs output data according to the integrity state of the simulated output data, and if there is an abnormality in the integrity of the simulated output data, a virtual data page is generated using the simulated output data, and the position information of the pixel is calculated. And a data page processor for changing the pixel information of the data page according to the position information of the pixel calculated by the virtual modulator and providing the changed data page to the demodulator.

The LDPC decoder may perform parity check on the simulated output data and convert the simulated output data into output data when the simulated output data has no integrity.

The pixel information may be on pixel position information of a virtual data page generated by virtually modulating the simulation output data.

In the description of the present invention, the names of the elements defined are defined in consideration of functions in the present invention, and should not be understood as meanings that limit the technical elements of the present invention. May be referred to by other names in the art. In addition, the code added to each component is described for convenience of description, and the contents shown in the drawings in which these codes are described do not limit each component to the range in the drawing.

In addition, as long as the functional similarity and identity thereof, even if the modified embodiment is adopted, it can be seen as an equivalent configuration, and even if the embodiment in which the modified part of the configuration is employed, it can be seen as an equivalent configuration.

Hereinafter, an iterative modulation and demodulation method using a low density parity check code and an optical information recording / reproducing apparatus using the same will be described in detail with reference to the accompanying drawings.

First, the optical information recording / reproducing apparatus according to the present invention will be described with reference to FIG. 1 is a block diagram showing an optical information recording / reproducing apparatus according to the present invention.

As shown, the optical information recording / reproducing apparatus 100 according to the present invention includes a light source 110, a beam splitter 120, a multiplexer 130, and a spatial light modulator 140. ), An optical information detector 150, an input data processor 170, and an output data processor 180.

The light emitted from the light source 110 is separated into the reference light (R) and the signal light (S) through the light splitter (120). The reference light R passes through the first shutter 125a and is reflected by the multiplexer 130 to be incident on the optical information recording medium D at a predetermined angle.

The signal light S passes through the second shutter 125b and enters the spatial light modulator 140 after the path is changed by the reflector 130a. In this case, the data page provided by the input data processor 170 is input to the spatial light modulator 140.

 The input data processor 170 converts the input data into a data page, which is a page unit of binary data, through LDPC encoding and modulation code conversion, and provides the input data to the spatial light modulator 140.

The spatial light modulator 140 optically modulates the data page information input from the input data processing unit 170 to generate a two-dimensional imaged data page, and projects it onto the incident signal light S to optically record the information. It enters into (D).

When the reference light R and the signal light S are incident on the optical information recording medium D, an interference pattern generated by the interference between the incident reference light R and the signal light S inside the optical information recording medium D. According to the intensity of the light induced generation of mobile charge (light induced generation of mobile charge) occurs and the interference pattern is recorded.

The multiplexer 130 adjusts the angle at which the reference light R is incident on the optical information recording medium D to implement angle multiplexing. The multiplexer 130 is preferably provided with a rotating mirror such as a galvano mirror.

On the other hand, in order to reproduce the recorded data, only the reference light R may be irradiated to the optical information recording medium D. During reproduction, the first shutter 125a passes the reference light R separated by the light splitter 120, while the second shutter 125b blocks the signal light S.

At this time, the reference light R irradiated from the multiplexer 130 through the first shutter 125a is diffracted by an interference pattern recorded on the optical information recording medium D, so that reproduction light having an image of a data page is obtained. Is generated. The reproduced light is detected by the optical information detector 150 as an image of the data page. The image of the detected data page is converted into output data by the output data processor 180.

The optical information detector 150 is composed of a light receiving arrangement such as a CMOS or a CCD. Equalizer 160 may employ a well known configuration such as a minimum mean square error (MMSE) equalizer.

The output data processor 180 repeatedly performs demodulation code conversion and LDPC decoding on the data page detected as the image state by the optical information detector 150, and converts the data page into final output data.

Hereinafter, the modulation of the optical information by the above-described input data processing unit 170 will be described with reference to the accompanying drawings. Each element mentioned below should be understood with reference to the above description and drawings.

2 is a block diagram showing modulation of optical information by the optical information recording / reproducing apparatus according to the present invention.

As shown, the input data processor 170 generates a data page through LDPC encoding and modulation code conversion. Here, the modulation code conversion may use 2: 4 balanced modulation code conversion or 6: 8 balanced modulation code conversion.

First, the input data processing unit 170 will be briefly described. The input data processing unit 170 generates the LDPC encoder 172 and the LDPC encoder 172 to encode the LDPC code using the input data. And a modulator 174 for changing the LDPC code based on the modulation code conversion. Here, the modulation code conversion may use 2: 4 balanced modulation code conversion or 6: 8 balanced modulation code conversion.

According to the input data processor 170, as the optical information data is input, the LDPC encoder 172 generates an LDPC code corresponding to the data, and the generated LDPC code is modulated by the modulator 174 to generate a data page. do.

The modulation-converted data page is loaded onto the signal light S by the spatial light modulator 140, and the signal light S on which the optical information is loaded is incident on the recording medium D while being connected to the reference light R. Optical information is recorded by the interference of.

On the other hand, the demodulation of the optical information by the optical information recording / reproducing apparatus according to the present invention is performed by the output data processing unit 180 of the optical information recording / reproducing apparatus.

Meanwhile, iterative demodulation of the optical information by the above-described output data processing unit 180 will be described with reference to the accompanying drawings. Each element mentioned below should be understood with reference to the above description and drawings.

3 is a block diagram showing demodulation of optical information by the optical information recording / reproducing apparatus according to the present invention, and FIG. 4 is a flowchart showing the optical information demodulating process by the optical information recording / reproducing apparatus according to the present invention. 5 is a graph showing the error rate by encoding the 2: 4 modulation code according to the present invention.

First, the output data processor 180 will be described briefly. The output data processor 180 includes a demodulator 182, an LDPC decoder 184, a virtual modulator 186, a data page processor 188, and the like.

Here, the demodulator 182 demodulates the data page while obtaining initial probability information for demodulation of the data through modulation code conversion of the image of the data page read by the optical information detector 150.

The LDPC decoder 184 performs decoding by the LDPC code through initial probability information and data obtained by the demodulator 182, and checks the integrity of the decoded data through parity check.

The LDPC decoder 184 outputs optical information by using the decoded data as output data when the decoded data has no abnormality in integrity, and outputs the decoded data by the virtual modulator 186 when there is a defect in the decoded data. To send.

The virtual modulator 186 virtually modulates the mock output data that has been decoded but has a defect to grasp position information of the on pixel by the mock output data.

Finally, the data page processor 188 increases the detection value at the position of the on pixel of the data page detected by the optical information detector 150 according to the on pixel position information of the mock output data modulated by the virtual modulator 186. The demodulator 182 is provided.

Hereinafter, an operation of the output data processor will be described with reference to FIG. 4.

First, as the optical information detector 150 detects a data page in the reproduction light reproduced by the optical information recorded on the recording medium, the data page detected by the demodulator 182 demodulates through modulation code conversion and simultaneously the data. Initial probability information for decoding the page is calculated (step S110).

Thereafter, the LDPC decoder 184 generates simulation output data by performing initial probability information of the data page and decoding by the LDPC code (step S120). In addition, the LDPC decoder 184 checks the integrity of the generated simulated output data through parity check on the generated simulated output data (step S130).

At this time, if the integrity of the data is verified in the integrity check of the simulated output data (step S140), the simulated output data whose integrity is confirmed is converted into output data by the LDPC decoder 184 and output (step S180).

On the other hand, if the integrity of the data is not confirmed in the integrity check of the simulation output data, that is, if a defect is found in the mother output data (step S140), the virtual modulator 186 modulates the simulation output data to generate a virtual data page. The location information of the pixel from the generated virtual data page is determined (step S150).

Thereafter, the data page processor 188 increases the detection value for the on pixel of the data page detected by the optical information detector 150 based on the position information of the on pixel identified in the virtual data page, thereby increasing the pixel of the data page. The information is changed (step S160).

In addition, the demodulator 182 demodulates the data page in which the pixel information of the pixel turned on by the data page processing unit 188 through modulation code conversion and calculates initial probability information for decoding of the data page again (step). S170).

Thereafter, the LDPC decoder 184 performs decoding by the LDPC code based on the newly calculated initial probability information to generate simulated output data once again (step S120). Once again, the LDPC decoder 184 checks the integrity of the generated simulation output data through parity check, etc., and determines whether to convert the simulated output data into output data.

Therefore, by repeatedly performing the above-described process, it is possible to obtain improved initial probability information through repetitive demodulation when reproducing optical information stored in the recording medium D, and by repeating LDPC decoding, the recording medium D It is possible to improve the reproduction efficiency of the optical information stored in the.

On the other hand, Figure 5 is a graph showing the performance of the demodulation method according to 2: 4 balanced modulation code conversion in SNR vs. BER in the optical information recording / reproducing apparatus according to the present invention.

'2: 4 mod of FIG. 5. + LDPC 'is a case where modulation is performed using conventional 2: 4 balanced modulation code conversion and LDPC code, and' combined 2: 4 mod. + LDPC 'is a case where repetitive demodulation is performed by using the initial probability information of the demodulator disclosed in the present invention and the positional information of the pixel on which the LDPC decoder is turned on.

In this case, the Nyquist size is 1.4, LDPC codes having a length of 1800 and a code rate of 0.9 in a channel with pixel spreading and additive white Gaussian noise (AWGN) added, and 2: 4 balanced modulation. Using code conversion, the increment value for the on-pixel was set to 1/10 of the noise deviation.

The demodulation is performed using a typical 2: 4 balanced modulation code conversion and LDPC code. + LDPC ', and' combined 2: 4 mod. 'Which performs iterative demodulation using the initial probability information of the demodulator and the position information of the pixel which is turned on by the LDPC decoder. Comparing + LDPC 'shows that BER by repeated demodulation according to the present invention is improved over BER by conventional demodulation.

Although described in detail with respect to preferred embodiments of the present invention as described above, those of ordinary skill in the art, without departing from the spirit and scope of the invention as defined in the appended claims Various modifications may be made to the invention. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

For example, the present invention may be implemented by adding a component having another additional function or replacing the component with another component. However, all other modified embodiments include the essential elements of the present invention should be considered to be included in the technical scope of the present invention.

As described above, according to the iterative modulation and demodulation method using the low density parity check code and the optical information recording / reproducing apparatus using the same, the decoding performance is improved by repeatedly performing demodulation and LDPC decoding when optical information is reproduced. In this case, the optical information reproduction efficiency can be improved.

Claims (13)

In the demodulation method of the data page detected by the optical information recording / reproducing apparatus, Initial probability information calculating step of demodulating the data page to calculate initial probability information, A simulation output data generation step of generating simulated output data by performing LDPC decoding using the initial probability information; An integrity check step of checking the integrity of the simulated output data; A data output step of outputting the simulation output data when there is no abnormality in the integrity of the simulation output data; And repetitively modulating the simulated output data to recalculate the initial probability information to perform LDPC decoding, if the integrity of the simulated output data is abnormal. The method of claim 1, wherein the iterative decoding step, Virtually modulating the simulated output data to generate a virtual data page for the simulated output data; Identifying pixel position information of the virtual data page; Changing pixel information of the data page according to the pixel position information; Recalculating initial probability information by demodulating the data page having changed pixel information; Iterative modulation and demodulation method using the LDPC, characterized in that for performing the LDPC decoding using the calculated initial probability information re-calculated to generate the simulation output data, and performing the integrity check step again. The method of claim 2, The integrity checking step, iterative modulation and demodulation method using an LDPC, characterized in that for performing parity check on the simulated output data. The method of claim 2, And the pixel information is position information of an on pixel of a virtual data page generated by virtually modulating the simulated output data. Light Source, A light splitter separating the light emitted from the light source into a reference light and a signal light, A spatial light modulator for loading data into the signal light; A detector for detecting reproduction light reproduced on the recording medium by the reference light; An input data processor which encodes the data to the LDPC, modulates the encoded data through balanced modulation code conversion to generate a data page, and provides the generated data page to the spatial light modulator; After demodulating the data page detected by the detector to calculate the initial probability information and performing LDPC decoding using the initial probability information, if the integrity of the generated simulated output data is abnormal, modulation and repetition by the simulated output data is performed. And an output data processor for changing the data page through decoding to generate output data. The method of claim 5, wherein the input data processing unit, An LDPC encoder converting the data to perform LDPC encoding; And a modulator for modulating the data encoded by the LDPC encoder by balanced modulation code conversion. The method of claim 5, wherein the output data processing unit, A demodulator for demodulating the data pages detected by the optical information detector to calculate initial probability information of the data pages; An LDPC decoder for generating simulated output data through LDPC decoding using the initial probability information and outputting the output data according to the integrity state of the simulated output data; A virtual modulator for generating a virtual data page using the simulated output data and calculating pixel position information when there is an abnormality in the integrity of the simulated output data; And a data page processing unit for changing the pixel information of the data page according to the position information of the pixel calculated by the virtual modulator, and providing the changed data page to the demodulator. The method of claim 7, wherein And the LDPC decoder performs parity check on the mock output data and converts the mock output data to output data when the mock output data has no integrity. The method of claim 7, wherein And the pixel information is on pixel position information of a virtual data page generated by virtually modulating the simulated output data. A light source that emits light, A detector for detecting reproduction light reproduced on the recording medium by the light, After demodulating the data page detected by the detector to calculate the initial probability information and performing LDPC decoding using the initial probability information, if the integrity of the generated simulated output data is abnormal, modulation and repetition by the simulated output data is performed. And an output data processor for changing the data page through decoding to generate output data. The method of claim 10, wherein the output data processing unit, A demodulator for demodulating the data pages detected by the optical information detector to calculate initial probability information of the data pages; An LDPC decoder for generating simulated output data through LDPC decoding using the initial probability information and outputting the output data according to the integrity state of the simulated output data; A virtual modulator for generating a virtual data page using the simulated output data and calculating pixel position information when there is an abnormality in the integrity of the simulated output data; And a data page processor for changing pixel information of the data page according to the position information of the pixel calculated by the virtual modulator and providing the changed data page to the demodulator. The method of claim 10, And the LDPC decoder performs parity check on the mock output data and converts the mock output data to output data when the mock output data has no integrity. The method of claim 10, And the pixel information is on pixel position information of a virtual data page generated by virtually modulating the simulated output data.

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