KR20140077767A - Apparatus and method for decoding iteratively - Google Patents

Apparatus and method for decoding iteratively Download PDF

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Publication number
KR20140077767A
KR20140077767A KR1020120146889A KR20120146889A KR20140077767A KR 20140077767 A KR20140077767 A KR 20140077767A KR 1020120146889 A KR1020120146889 A KR 1020120146889A KR 20120146889 A KR20120146889 A KR 20120146889A KR 20140077767 A KR20140077767 A KR 20140077767A
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KR
South Korea
Prior art keywords
parity
information
unit
likelihood ratio
interleaving
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KR1020120146889A
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Korean (ko)
Inventor
김혁
구본태
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한국전자통신연구원
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Priority to KR1020120146889A priority Critical patent/KR20140077767A/en
Publication of KR20140077767A publication Critical patent/KR20140077767A/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H04L1/1819—Hybrid protocols; Hybrid automatic repeat request [HARQ] with retransmission of additional or different redundancy

Abstract

The present invention enables a turbo decoder to perform reliable decoding with only a small amount of parity when performing a parity automatic retransmission request in a wireless communication system or an image encoding system, and more particularly, to a hybrid automatic repeat request (HARQ) It is possible to reduce the number of unnecessary retransmissions by increasing the reliability of the iterative decoding apparatus when the automatic retransmission is required in the wireless communication system supporting the DVC system or when the parity is automatically retransmitted in the DVC system, Apparatus and method are disclosed.

Description

[0001] APPARATUS AND METHOD FOR DECODING ITERATIVELY [0002]

The present invention relates to an iterative decoding apparatus and method, and more particularly, to a turbo decoding apparatus capable of performing reliable decoding with only a small amount of parity when performing a parity automatic retransmission request in a wireless communication system or an image encoding system, In particular, when an automatic retransmission is requested in a wireless communication system supporting a hybrid automatic repeat request (HARQ) scheme or when parity is automatically retransmitted in a distributed video coding (DVC) system, And an unnecessary number of retransmissions can be reduced by increasing reliability.

BACKGROUND ART Hybrid Automatic Repeat Request (HARQ) is an advanced type of Automatic Repeat Request (ARQ), in which a retransmission is attempted in order to reduce error and loss of a packet, And retransmits the packet using the information of the packets previously transmitted. The HARQ is divided into a chase combining (CC) scheme and an incremental redundancy (IR) scheme.

The CC scheme operates using both the retransmitted packet and the signal information of previously transmitted packets. At this time, the packet to be retransmitted transmits the initially transmitted original packet as it is. That is, since the CC scheme attempts to receive the original packet and all the retransmitted packets in combination, a combining effect inherent to HARQ occurs.

The IR scheme uses a coding scheme such as a Turbo code, a Rate Compatible Punctured Convolutional (RCPC) code, or an LDPC (Low Density Parity Check) code. Blocks are generated. In the initial transmission, only the original packet except the redundant information is transmitted. If the transmission fails, the redundant information block is transmitted without transmitting the original packet. That is, for the retransmission request of the IR scheme, surplus information generated by encoding is transmitted instead of the original packet. At this time, the receiving end receives only the original packet in the initial transmission. When the redundant information block is received in the retransmission request, the receiving end attempts to combine the original packet and all the retransmitted packets and thus receives the combined packet. And a coding gain can be obtained.

However, in the IR scheme HARQ, the redundant information received by the retransmission is combined with the previously transmitted information in the input buffer of the receiving end so that channel decoding is performed, so that decoding is performed according to the designated initial value every time.

On the other hand, in the Distributed Video Coding (DVC) system, after attempting to decode by transmitting surplus information similar to the IR scheme of HARQ, if the retransmission is requested, another surplus information block is retransmitted to use more surplus information In this case, since the decoding is performed from the designated initial value, if the required amount of parity can not be obtained, the retransmission is requested again.

The present invention can perform reliable decoding with only a small amount of parity data when requesting retransmission of parity data automatically or automatically retransmitting parity data in a wireless communication system or a distributed image coding system And to provide an iterative decoding apparatus and method.

According to the present invention, when automatic retransmission of parity data is required in a wireless communication system supporting HARQ, or when parity data is automatically retransmitted in an image encoding system, surplus information stored as a result of an iterative decoding operation is re- It is an object of the present invention to provide an iterative decoding apparatus and method capable of increasing the reliability of an iterative decoding operation result so as to converge more quickly and reducing an unnecessary extra retransmission process that may occur after iterative decoding .

According to an aspect of the present invention, there is provided an iterative decoding apparatus comprising: an input buffer for storing input data symbols; An internal metric calculator for calculating metrics necessary for performing an iterative decoding operation on the input data symbols stored in the input buffer and accumulating the calculated metrics; A log likelihood ratio calculation unit for calculating a log likelihood ratio of the metric to the parity in the metrics accumulated by the internal metric calculation unit; An interleaving / deinterleaving operation unit for calculating parity residue information by performing interleaving and deinterleaving on the log likelihood ratio of the metric for the parity; A surplus information extracting unit for extracting a parity residue information value to be used for size adjustment from the parity residue information; And a scaling unit for scaling the size of the parity residue information extracted by the parity information extraction unit and transmitting the adjusted parity residue value to the input buffer.

According to the present invention, when a wireless communication system or a distributed image encoding system requests retransmission of parity data automatically or retransmits parity data automatically, the iterative decoding apparatus performs highly reliable decoding with only a small amount of parity data There is an effect to be able to.

Also, according to the present invention, when automatic retransmission of parity data is required in a wireless communication system supporting the HARQ scheme, or when parity data is automatically retransmitted in an image encoding system, surplus information stored as a result of an iterative decoding operation is newly received It is possible to increase the reliability of the channel decoding result so as to converge more quickly and to reduce an unnecessary redundant retransmission process that may occur after channel decoding.

Fig. 1 is a block diagram for explaining a configuration of an iterative decoding apparatus in a system for automatically requesting retransmission.
2 is a block diagram for explaining a configuration of an iterative decoding apparatus in which size adjustment of surplus information according to the present invention is performed.
FIG. 3 is a flowchart illustrating an iterative decoding method in which size adjustment of surplus information according to the present invention is performed.

Hereinafter, an iterative decoding apparatus and method according to the present invention will be described with reference to the accompanying drawings. Prior to the detailed description of the present invention, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

In the present invention, a system that requests retransmission automatically corresponds to a Hybrid Automatic Repeat Request (HARQ) system in a wireless communication system and a Distributed Video Coding (DVC) system in an image coding system. In the present invention, an iterative decoding apparatus for turbo encoding will be described as an example among various encoding schemes such as turbo code, RCPC code, LDPC code, and the like of a surplus increase (IR) scheme.

Fig. 1 is a block diagram for explaining a configuration of an iterative decoding apparatus in a system for automatically requesting retransmission.

1, an iterative decoding apparatus 100 in a system for automatically requesting retransmission includes a deinterleaver 110, an input buffer 120, an internal metric calculator 130, a log likelihood ratio calculator 140, An interleaving / deinterleaving operation unit 150, and a redundancy information storage unit 160. [

The receiver 110 performs a reverse puncturing on the received symbol according to the puncturing pattern when the transmitted input data symbol is received first.

The input buffer 120 stores the input data symbol subjected to the inverse puncturing by the de-correlator 110 and transmits the stored input data symbol to the internal metric calculator 130. [

The internal metric calculation unit 130 calculates the metrics necessary for performing an iterative decoding operation on the input data symbols stored in the input buffer 120, and accumulates the calculated metrics. At this time, the internal metric calculator 130 may perform a metric calculation on the input data symbols stored in the input buffer 120, and may calculate a state metric of the calculated branch metric to accumulate the calculated state metric.

The log likelihood ratio calculation unit 140 calculates a log likelihood ratio of the metrics accumulated by the internal metric calculation unit 130. The log likelihood ratio calculation unit 140 transmits the calculated log likelihood ratio to the interleaving / deinterleaving operation unit 150.

The interleaving / deinterleaving operation unit 150 performs interleaving and deinterleaving operations on the log likelihood ratio calculated by the log likelihood ratio calculating unit 140, and stores the redundant information, which is the result of the interleaving and deinterleaving operations, (160).

The redundancy information storage unit 160 stores redundancy information, which is a result of the interleaving and deinterleaving operations performed by the interleaving / deinterleaving operation unit 150. At this time, the surplus information stored in the surplus information storage unit 160 in the next iterative decoding operation according to the iterative decoding rule of the turbo decoding is transmitted to the input buffer 120 and added to the next symbol, and the metric calculated by the inner metric calculation unit 130 Used in calculations.

If it is determined that the decoding reliability is low according to a predetermined criterion after the last iterative decoding, the parity data symbol is requested to be retransmitted. In the IR scheme, in addition to the previously transmitted symbols, parity data Symbol. Here, a condition for requesting retransmission of a parity data symbol or a concrete retransmission scheme is not well known in the art and is not included in the scope of the present invention, so a description thereof will be omitted.

These parity data symbols are deinterleaved through the deinterleaver 110 and used in the input buffer 120 to combine with the existing data symbols to perform decoding. In this case, when the first iteration decoding operation is performed,

All of the information is initialized to zero and computed. After the second iteration decoding operation is performed, the newly calculated excess information is affected by newly transmitted data symbols and used for internal metric calculation.

However, the previously computed and stored redundant information are probabilistic estimates of the received received data symbols, and generally have a more accurate probability value than the newly transmitted data symbols. Further, in the case of distributed image coding, error-free parity data symbols are transmitted in comparison with erroneous systematic data symbols. Therefore, when calculating the branch metrics using newly received parity data symbols after retransmission is requested, By using the redundant information, the decoding result with much higher reliability can be obtained, and the turbo device can converge to the desired reliability more quickly, thereby reducing unnecessary number of retransmissions.

In this process, surplus information can be used as it is, and if it is appropriately resized, erroneous probability values that can be included in surplus information can be adjusted to a correct probability value more quickly. However, since the size adjustment may be different in the case of the wireless communication system and the distributed image coding, it is necessary to find the optimum value and adjust the size.

2 is a block diagram for explaining a configuration of an iterative decoding apparatus in which size adjustment of surplus information according to the present invention is performed.

Referring to FIG. 2, an iterative decoding apparatus 200 in which size adjustment of surplus information according to an embodiment of the present invention is performed includes a descrambler 210, an input buffer 220, an internal metric calculator 230, An interleaving / deinterleaving unit 250, an excess information storing unit 260, a redundancy information extracting unit 270, and a size adjusting unit 280. The interleaving /

When the transmitted input data symbol is received, the descrambler 210 performs a reverse puncturing on the received symbol according to the puncturing pattern.

The input buffer 220 stores the input data symbol subjected to the inverse puncturing by the de-correlation unit 210, and transmits the stored input data symbol to the internal metric calculation unit 230.

The internal metric calculation unit 230 calculates the metrics necessary for performing an iterative decoding operation on the input data symbols stored in the input buffer 220, and accumulates the calculated metrics. At this time, the internal metric calculation unit 230 may perform a metric calculation on the input data symbols stored in the input buffer 220, and may calculate a state metric of the calculated branch metrics to accumulate the calculated state metrics.

The log likelihood ratio calculation unit 240 calculates the log likelihood ratio of the metrics accumulated by the internal metric calculation unit 230. [ The log likelihood ratio calculating unit 240 includes a systematic log likelihood ratio calculating unit 242 and a parity log likelihood ratio calculating unit 244. The systematic log likelihood ratio calculating unit 242 calculates And the parity log likelihood ratio calculation unit 244 calculates the log likelihood ratio of the metrics for the parity part. The log likelihood ratio calculation unit 240 transmits the log likelihood ratio calculated for the metrics for the systematic part and the log likelihood ratio calculated for the metrics for the parity part to the interleaving / deinterleaving operation unit 250. [

The interleaving / deinterleaving operation unit 250 performs interleaving and deinterleaving operations on the log likelihood ratio calculated by the log likelihood ratio calculating unit 240. The systematic interleaving / deinterleaving operation unit 252 includes a systematic interleaving / deinterleaving operation unit 252 and a parity interleaving / deinterleaving operation unit 254. The systematic interleaving / deinterleaving operation unit 252 includes a systematic interleaving / And the parity interleaving / deinterleaving operation unit 254 performs interleaving and deinterleaving operations on the log likelihood ratio for the parity part. The interleaving / deinterleaving operation unit 250 performs interleaving and deinterleaving operations on the systematic redundancy information, which is the result of performing the interleaving and deinterleaving operations on the log likelihood ratio for the systematic part, and the log likelihood ratio for the parity part. And transmits the parity residue information, which is the result of the execution, to the surplus information storage unit 260.

The redundancy information storage unit 260 stores redundancy information, which is a result of the interleaving and deinterleaving operations performed by the interleaving / deinterleaving operation unit 250. The redundant information storage unit 260 includes a systematic redundancy information storage unit 262 and a parity redundancy information storage unit 264. The systematic redundancy information storage unit 262 includes a systematic interleaving and deinterleaving operation unit 252, and the parity redundancy information storage unit 264 stores parity residue information received from the parity interleaving / deinterleaving operation unit 254. The parity redundancy information storage unit 264 stores parity residue information received from the parity interleaving /

The surplus information extraction unit 270 extracts surplus information values to be used for size adjustment among the surplus information stored in the surplus information storage unit 260. [ The surplus information extraction unit 270 includes a systematic surplus information extraction unit 272 and a parity redundancy information extraction unit 274. The systematic surplus information extraction unit 272 extracts a systematic surplus information storage unit 262 The parity redundancy information extraction unit 274 extracts the systematic remnant information values to be used for size adjustment among the systematic surplus information values stored in the parity redundancy information storage unit 264, And extracts the parity residue information value. The systematic / parity redundancy information values used for size adjustment extracted by the systematic surplus information extraction unit 272 and the parity redundancy information extraction unit 274 are stored in the systematic / parity redundancy information stored in the redundancy information storage unit 260 The average value of the absolute value or the average value of the absolute value or the value previously found through the experiment can be set and used, and the stored surplus information value can be used without performing the normalization by using 0.

The resizing unit 280 adjusts the magnitude of the surplus information value extracted by the surplus information extracting unit 270 and transfers the adjusted surplus information value to the input buffer 220. The systematic scaling unit 282 scales the systematic redundancy information values extracted by the systematic redundancy information extraction unit 272. The systematic scaling information unit 282 scales the systematic scaling information The parity size adjusting unit 284 adjusts the size of the parity residue information value extracted by the parity redundancy information extracting unit 274 to the input buffer 220, And transmits the size-adjusted parity residue information 294 to the input buffer 220. [ That is, in the next iterative decoding operation according to the iterative rule while the subsequent iterative decoding operation is performed, the systematic / parity redundant information extracted from the previously calculated systematic / parity redundant information extraction units 272 and 274 The systematic / parity redundancy information values are adjusted in the systematic / parity size adjusters 282 and 284 and the systematic / parity redundancy information values 292 and 294, which are the resultant values, are transmitted to the input buffer 220, The iterative decoding operation proceeds. In addition, when the iterative decoding operation is completed, the decoded data is output and the systematic / parity redundant information stored as a result of the last iterative decoding operation is transferred to the memory outside the iterative decoding apparatus 200, The data symbols are combined with the retransmitted data symbols. While the iterative decoding operation is performed in the iterative decoding apparatus 200, the input data symbol values used when calculating the internal metrics are used as the value obtained by adding appropriately sized systematic / parity redundant information values 292 and 294 do.

Hereinafter, with reference to FIG. 3, an iterative decoding method in which size adjustment of surplus information according to the present invention is performed will be described. Hereinafter, a part of the iterative decoding apparatus according to the present invention will be described with reference to FIG.

FIG. 3 is a flowchart illustrating an iterative decoding method in which size adjustment of surplus information according to the present invention is performed.

Referring to FIG. 3, the iterative decoding method according to the present invention receives an input data symbol transmitted first (S300), and performs an iterative decoding operation on the input data symbol according to an iteration rule (S310). The optimal systematic / parity redundancy information value is extracted every time the iteration decoding operation is performed and the extracted systematic / parity redundancy information value is adjusted (S320).

If it is determined in step S330 that the next iteration decoding operation should be performed, the systematic / parity redundancy information value adjusted in step S320 is added to the input data symbol value in step S340. , The steps S310 to S330 are repeatedly performed until the last iterative decoding operation is completed.

If the last iteration is completed, the decoded data is output and the systematic / parity redundancy information stored as a result of the last iteration decoding operation is transferred to the memory outside the iterative decoding apparatus (S350) So that it can be combined with the retransmitted data symbols when retransmission of the symbols is performed.

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

200: Iterative decoding device
210: Stele study
220: Input buffer
230 internal metric calculation unit
240: log likelihood ratio calculation unit
250: Interleaving / deinterleaving operation unit
260: Surplus information storage unit
270: Surplus information extracting unit
280:

Claims (1)

An input buffer for storing input data symbols;
An internal metric calculator for calculating metrics necessary for performing an iterative decoding operation on the input data symbols stored in the input buffer and accumulating the calculated metrics;
A log likelihood ratio calculation unit for calculating a log likelihood ratio of the metric to the parity in the metrics accumulated by the internal metric calculation unit;
An interleaving / deinterleaving operation unit for calculating parity residue information by performing interleaving and deinterleaving on the log likelihood ratio of the metric for the parity;
A surplus information extracting unit for extracting a parity residue information value to be used for size adjustment from the parity residue information; And
And a scaling unit for scaling the parity residue information value extracted by the parity information extraction unit and transmitting the adjusted parity residue value to the input buffer.
KR1020120146889A 2012-12-14 2012-12-14 Apparatus and method for decoding iteratively KR20140077767A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102157213B1 (en) * 2019-08-21 2020-09-17 단암시스템즈 주식회사 Apparatus and method for decoding data using double buffers and signal converting apparatus using the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102157213B1 (en) * 2019-08-21 2020-09-17 단암시스템즈 주식회사 Apparatus and method for decoding data using double buffers and signal converting apparatus using the same

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