KR20120071109A - Method and apparatus for determining iterative decoding of decoder - Google Patents

Method and apparatus for determining iterative decoding of decoder Download PDF

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Publication number
KR20120071109A
KR20120071109A KR1020100132712A KR20100132712A KR20120071109A KR 20120071109 A KR20120071109 A KR 20120071109A KR 1020100132712 A KR1020100132712 A KR 1020100132712A KR 20100132712 A KR20100132712 A KR 20100132712A KR 20120071109 A KR20120071109 A KR 20120071109A
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South Korea
Prior art keywords
decoder
decoding
error
ctc
iterative decoding
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KR1020100132712A
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Korean (ko)
Inventor
문영진
임광재
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한국전자통신연구원
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Priority to KR1020100132712A priority Critical patent/KR20120071109A/en
Publication of KR20120071109A publication Critical patent/KR20120071109A/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/37—Decoding methods or techniques, not specific to the particular type of coding provided for in groups H03M13/03 - H03M13/35
    • H03M13/3746—Decoding methods or techniques, not specific to the particular type of coding provided for in groups H03M13/03 - H03M13/35 with iterative decoding
    • H03M13/3753—Decoding methods or techniques, not specific to the particular type of coding provided for in groups H03M13/03 - H03M13/35 with iterative decoding using iteration stopping criteria
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/65—Purpose and implementation aspects
    • H03M13/6502—Reduction of hardware complexity or efficient processing

Abstract

PURPOSE: A method and apparatus for determining iterative decoding of a decoder are provided to reduce unnecessary repetition by changeably controlling the Iterative decoding operation of a CTC decoder according to radio channel environments. CONSTITUTION: An iterative decoding determination part(24) includes an error count part(241), a comparison part(242), and a repetition determination part(243). The iterative decoding determination part further includes a threshold value setting part(244). The error count part produces errors by comparing second decoding data for hard decision outputted from the first decoder with fourth decoding data for the hard decision outputted from a second decoder. The comparison part compares counted errors with a threshold value. The repetition decision part performs iterative decoding based on a comparison result of the comparison part.

Description

Method and apparatus for determining iterative decoding of decoder

The present invention relates to a decoder, and more particularly, to a method and apparatus for determining whether or not to repeatedly decode a decoder.

Recently, mobile wireless communication systems require reliable transmission of high-speed multimedia data, and strong channel coding schemes are required for reliable transmission of high-speed multimedia data.

The CTC (convolution turbo code) method has a relatively simple decoding algorithm, but shows a significant performance improvement during iterative decoding. In addition, it is known as a robust channel coding technique that can guarantee reliability even in a wireless fading channel environment. The CTC encoder consists of two convolutional encoders and an interleaver connecting them. The first convolutional encoder encodes the input data and outputs the output data, and the second convolutional encoder encodes the interleaved input data through the interleaver and outputs the output data. That is, two convolutional encoders generate coded data for original data and coded data for interleaver data.

Meanwhile, the CTC decoder outputs a soft decision value by using a maximum a posteriori (MAP) algorithm that can generate soft decision output information for each bit, and uses an iterative decoding technique to improve decoding performance. . Optimum performance can be achieved if the CTC decoder repeatedly performs an infinite number of decoding operations, i.e., an infinite number of iterations. A method of operating the CTC decoder by determining the number of iterations in advance within the performance range is used.

Conventionally, a method of verifying the performance of a CTC decoder in various wireless channel environments through simulation and determining an appropriate number of repetitions based on the verification result is used. However, this approach is not only impossible to verify for every possible radio channel environment through simulation, but also has the disadvantage that it is impossible to determine the appropriate number of iterations in real time and variably in a constantly changing radio channel environment.

The problem to be solved by the present invention is to provide a method and apparatus for more efficiently determining whether the decoder is repeated decoding.

Another object of the present invention is to provide a method and an apparatus capable of determining in real time and variably whether or not to repeatedly decode a CTC decoder.

A method according to a feature of the present invention for the above problem is a method for determining the iterative decoding in a decoding device comprising a first decoder and a second decoder, the decoding data for hard decision output from the first decoder and the Calculating an error of the decoded data for hard decision output from the second decoder; Comparing the calculated error with a preset threshold value; Determining to perform iterative decoding if the error is larger than a threshold; Receiving an error check result on the decoded data for hard decision output from the second decoder when the error is smaller than a threshold; If the error check result indicates success without an error, determining that the operation of the decoding device is stopped; And resetting the threshold if the error check result indicates an error in error and determining that the decoding device performs repeated decoding.

According to an embodiment of the present invention, it is possible to variably adjust whether or not the CTC decoder performs repetitive decoding according to a wireless channel environment and to reduce unnecessary repetition. Accordingly, the average repeat decoding number of the CTC decoder can be reduced in the receiving device, and additionally, by applying a hybrid automatic repeat request (HARQ), the system performance can be improved by retransmission when the predetermined number of repeats is exceeded.

1 is a diagram showing the structure of a transmission and reception apparatus according to an embodiment of the present invention.
2 is a diagram illustrating a structure of a CTC decoding unit according to an embodiment of the present invention.
3 is a diagram illustrating a structure of an iterative decoding determining unit according to an embodiment of the present invention.
4 is a flowchart of a method of determining an iterative decoding according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise.

Hereinafter, a method and apparatus for determining the number of iterations of a decoder according to an embodiment of the present invention will be described with reference to the drawings.

1 is a diagram showing the structure of a transmission and reception apparatus according to an embodiment of the present invention.

As shown in FIG. 1, a transmission device 1 according to an embodiment of the present invention includes a cyclic redundancy check (CRC) insertion unit 11, a convolution turbo code (CTC) code unit 12, a modulator 13, and the like. A transmitter 14, and the receiver 2 includes a receiver 21, a demodulator 22, a CTC decoder 23, an iterative decoding determiner 24, and a CRC checker 25. .

The CRC inserting unit 11 of the transmitting device 1 inserts and outputs a CRC in the source data to be transmitted, and the CTC coder 12 encodes and outputs the data in which the CRC is inserted. The modulator 13 modulates the encoded data and transmits it through the transmitter 14.

Meanwhile, the receiver 21 of the receiver 2 receives a signal transmitted through a wireless section, and the demodulator 22 demodulates the received signal. The demodulator 22 detects a signal using a maximum likelihood (ML) method and generates a log-likelihood ratio (LLR) value for soft-decision upon channel decoding.

The CTC decoder, that is, the CTC decoder 23 acquires data by decoding the demodulated signal and repeatedly performs an operation of decoding the data by the determined number of repetitions. In particular, the CTC decoder 23 decodes a transmission symbol encoded and transmitted by a CTC code from a transmitting device, and determines and outputs a final decoding bit based on the input LLR values. The CTC decoder 23 according to an embodiment of the present invention determines the final decoding bit based on three LLR values. The CTC decoding unit 23 is an LLR value for soft decision on the original data provided from the demodulator 22, an LLR value for soft decision on the parity data value received through the CTC decoding unit after receiving the raw data, and the CTC. The data interleaved through the interleaver included in the decoder uses the LLL value for soft decision on the parity value passed through the CTC decoder.

The CRC checker 25 checks whether there is an error based on the output value of the CTC decoder 23, and outputs final data according to the check result.

The iterative decoding determination unit 24 determines whether or not iterative decoding is performed based on the output data of the CTC decoding unit 23, and also determines whether or not it is repeated decoding based on the check result of the CRC check unit 25.

2 is a view showing a specific structure of the CTC decoding unit 23 according to an embodiment of the present invention.

As shown in FIG. 2, the CTC decoder 23 according to an embodiment of the present invention includes a first decoder 231, a second decoder 232, a demultiplexer 233, a first interleaver 234, and a first decoder. Two interleaver 235 and deinterleaver 236.

The first decoder 231 decodes the inputted information bits and outputs them, and the first interleaver 234 rearranges, interleaves, and outputs the inputted information bits, and the second decoder 232 outputs the first interleaver 234. Decode and output the information bits rearranged by The second interleaver 235 interleaves the bits output from the first decoder 231 and outputs the bits to the second decoder 232. The deinterleaver 236 outputs the bits output from the second decoder 232 in the original order. Rearranged to be deinterleaved and outputted to the first decoder 231.

The demultiplexer 233 provides parity bits inputted to the first decoder 231 and the second decoder 232, respectively, and the parity bits inputted to the demultiplexer are parity bits obtained from the received signal. For convenience of explanation, we will call it "receive parity bit."

The detailed operation of each component in the CTC decoding unit 23 having such a structure will be described.

The first decoder 231 decodes the input information bit, the received parity bit, and the parity bit, which is a surplus information value that is a result of decoding performed in the previous decoding process. Specifically, the first decoder 231 provides the original data provided from the demodulator 22. First data D1 for soft decision on information bits), second data D2 for soft decision on received parity bits provided from demultiplexer 233, and second decoder 232. Decoding is performed using the third data D3, which is an LLR value for soft decision, for the parity bit, and the first decoded data OD1 for soft decision and the second decoded data for hard decision (OD2). )

The second decoder 232 includes data D4 in which the first decoded data OD1 of the first decoder 231 is interleaved through the second interleaver 235, and a reception parity bit provided from the demultiplexer 233. The second data D2, which is an LLR value for soft decision, and the first data, which is an LLR value for soft decision, for the original data are decoded using the data D1 'interleaved by the first interleaver 234. The third decoded data OD3 for soft decision and the fourth decoded data OP4 for hard decision are output. The third decoded data OP3 output from the second decoder 232 is deinterleaved through the deinterleaver 236 and then input to the first decoder 231, which is parity output through the second decoder 232. It serves as third data D3, which is an LLR value for soft decision on a bit.

In general, the first and second decoders 232 repeatedly perform the decoding process based on the input data until a satisfactory performance is obtained. In an embodiment of the present invention, the number of iterations to perform the process is determined through simulation. Rather than being set in advance, it is determined in real time based on the decoded and output values.

To this end, the iterative decoding determiner 24 according to the embodiment of the present invention has the following structure.

3 is a diagram illustrating a structure of an iterative decoding determining unit according to an embodiment of the present invention.

The iterative decoding determiner 24 according to an exemplary embodiment of the present invention includes an error counting unit 241, a comparator 242, and an iterative determining unit 243 as shown in FIG. 3, and in addition, a threshold setting unit 24. (244) more.

The error counting unit 241 compares the second decoded data OP2 for hard decision output from the first decoder 231 with the fourth decoded data for hard decision output from the second decoder 232 to obtain an error. Calculate. This can also be said to count errors.

The comparator 242 compares the counted error with a threshold value.

The iteration determination unit 243 performs iterative decoding until the error counted based on the comparison result of the comparison unit 242 becomes smaller than the threshold value. That is, if the counted error is larger than the threshold, it is determined to perform repeated decoding, and if the counted error is smaller than the threshold, it is determined to stop decoding.

In particular, the iterative decision unit 243 checks the CRC check unit 25 so that the CRC check unit 25 performs a CRC check on the final output value of the CTC decoder 23 when the counted error is smaller than the threshold value. Enable it. The threshold for repetition determination is reset according to the check result of the CRC check unit 25. For example, if the final hard decision value of the CTC decoder 23 fails as a result of the CRC check, the threshold value is reset to another value through the threshold value setting unit 244 and repeated decoding is performed. On the other hand, if the final hard decision value of the CTC decoding unit 23 is successful as a result of the CRC check, the decoding process is terminated.

As described above, according to the embodiment of the present invention, it is possible to variably determine whether the CTC decoder 23 repeatedly decodes the signal according to the characteristics of the received signal. If the maximum number of iterations of the CRC check is determined in advance, it is possible to prevent the decoding process from falling into an infinite repetition condition in a state where the radio channel environment is not good. For example, after setting the maximum number of iterations of the CRC check, after the number of times the CRC is checked for the final decoded data of the CTC decoding unit 23, the repeated decoding is terminated. In this case, repetitive decoding may be stopped and a hybrid automatic repeat request (HARQ) may be performed. In this way, if HARQ is additionally applied and the predetermined number of repetitions is exceeded, system performance may be improved through retransmission.

Next, a repetition number determination method according to an embodiment of the present invention will be described based on an iterative decoding determination unit having the above structure.

4 is a flowchart illustrating a method for determining the number of repetitions according to an embodiment of the present invention.

The signal which is subjected to CTC encoding processing from the transmitting apparatus 1 and transmitted is received by the receiving apparatus 2 and then input to the CTC decoding unit 23, and the CTC decoding unit 23 decodes the input signal. The first to fourth decoded data are output as described above. The first decoded data of the first decoder 231 and the third decoded data of the second decoder 232 for soft decision are processed through the second interleaver 235 or the deinterleaver 236 to perform the second decoder 232. Or it is input to the first decoder 231 and reprocessed. Since the operation of the CTC decoding unit 23 is a known technique, a detailed description thereof will be omitted.

The iterative decoding determiner 24 according to an exemplary embodiment of the present invention uses the second decoded data OD2 and the second decoder 232 for hard decision output from the first decoder 231 of the CTC decoder 23. The fourth decoded data OD4 for outputting hard decision is received and operated as follows.

First, as shown in FIG. 4, the iterative decoding determiner 24 calculates an error between the second decoded data OD2 and the fourth protected data (S100 to S120). The calculated error is compared with a preset threshold value (S130).

As a result of the comparison, the iterative decoding determining unit 24 determines to perform iterative decoding when the error is larger than the threshold value, and continues to enable the CTC decoding unit 23. Accordingly, iterative decoding of the CTC decoding unit 23 is performed (S140).

On the other hand, when the error is smaller than the threshold value, the iterative decoding determiner 24 enables the CRC checker 25 to perform an error check on the final decoded data finally output from the CTC decoder 23. (S150).

If the result of the error check on the final decoded data of the CRC checker 25 is a success without an error, the iterative decoding determiner 24 stops decoding of the CTC decoder 23 (S160 to S170).

However, if the error check result of the final decoded data of the CRC check unit 25 is a failure with an error, the iterative decoding determination unit 24 resets the threshold value and causes the CTC decoder 23 to perform the iterative decoding.

At this time, in order to prevent such repeated decoding from being continued, if the error check result of the final decoded data of the CRC check unit 25 is unsuccessful, the iterative decoding determination unit 24 counts the number of times the error check is performed. In operation S180, the counted number is compared with a preset CRC check maximum iteration number. If the counted number is smaller than the maximum number of iterations of the CRC check, the threshold value is reset (S190), and the CTC decoder 23 performs the repeated decoding (S140). Here, the maximum number of iterations of the CRC check can be appropriately changed according to the radio channel environment and requirements.

However, if the counted number is larger than the maximum number of CRC check repetitions, the CTC decoding unit 23 stops decoding (S170). In this case, if HARQ is additionally applied, system performance may be improved through retransmission when a predetermined number of repetitions is exceeded.

Through this process, the number of repetitions of the CTC decoder can be adjusted variably according to the wireless channel environment, and unnecessary repetitive decoding can be reduced. Due to this effect, the receiving apparatus can reduce the average number of CTC decoding repetitions.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (1)

In a method for determining repetitive decoding in a decoding device including a first decoder and a second decoder,
Calculating an error between the decoded data for hard decision output from the first decoder and the decoded data for hard decision output from the second decoder;
Comparing the calculated error with a preset threshold value;
Determining to perform iterative decoding if the error is larger than a threshold;
Receiving an error check result on the decoded data for hard decision output from the second decoder when the error is smaller than a threshold;
If the error check result indicates success without an error, determining that the operation of the decoding device is stopped;
Resetting the threshold and determining that the decoding device performs repeated decoding if the error check result indicates an error in error.
It includes, iterative decoding determination method.
KR1020100132712A 2010-12-22 2010-12-22 Method and apparatus for determining iterative decoding of decoder KR20120071109A (en)

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