KR20070117223A - Method of decoding using a plurality of parity check matrices - Google Patents

Abstract

A method of decoding using a plurality of parity check matrices is provided to perform decoding of unstable channel information on the basis of stable channel information. According to a method of performing LDPC(Low Density Parity Check) encoding using a parity check matrix, a code word obtained by encoding information bits by a first parity check matrix is received from a transmitter. An NACK signal is transmitted according to the result of decoding the received code word by the first parity check matrix. A retransmission signal for the NACK signal is received from the transmitter. A first part of the received code word is decoded by a second parity check matrix. The retransmission signal includes a parity bit generated by the second parity check matrix for a second part of the information bits.

Description

Method of decoding using a plurality of parity check matrices}

1 is a view showing the structure of a mobile communication channel to which the present invention and the prior art are applied.

2 to 4 illustrate a retransmission scheme according to the prior art.

5 to 6 are diagrams illustrating a retransmission scheme according to the prior art and the present invention.

7 is a diagram illustrating the concept of a subblock on a parity check matrix.

8 is an example of a conventionally proposed model matrix.

9 is a diagram illustrating a concept in which a model matrix is extended to a parity check matrix.

10 is a diagram illustrating a conventional LDPC decoding method according to the present invention.

11A through 11C are block diagrams illustrating a method of performing decryption according to an embodiment of the present invention.

12 is a block diagram illustrating a method of selecting information bits used when encoding and decoding according to the present embodiment.

FIG. 13 is a block diagram illustrating still another example of a method of selecting information bits used when encoding and decoding according to the present embodiment.

14 is a block diagram illustrating still another example of a method of selecting information bits used when encoding and decoding according to the present embodiment.

The present invention relates to a Low Density Parity Check (LDPC) code, and more particularly, to a method of performing LDPC decoding using a plurality of parity check matrices.

1 is a view showing the structure of a mobile communication channel to which the present invention and the prior art are applied. Hereinafter, the structure of a mobile communication channel will be described with reference to FIG. 1. In order to transmit the data to be transmitted from the transmitter without loss or distortion in the radio channel, a channel coding procedure is performed. As the channel coding technique, there are various techniques such as convolutional coding, turbo coding, and LDPC coding. Data that has undergone the channel coding procedure may be transmitted as a single symbol by collecting a plurality of bits when transmitted through a wireless channel. In this case, a procedure in which several bits are mapped to one symbol is called modulation.

The modulated data is converted into a signal for multiplex transmission through a multiplexing process or a multiple access method. As the multiplexing method, various methods such as CDM, TDM, and FDM exist. In FIG. 1, an example of orthogonal frequency division multiplexing (OFDM) is illustrated. The signal that has passed through the multiplexing block is changed into a structure suitable for transmission to one or more multiple antennas and transmitted to a receiver through a radio channel. Data transmitted in the course of passing through the wireless channel may experience fading and thermal noise, which may cause distortion of the data.

The modulated data is transmitted to a receiver through a wireless channel. In this process, the transmitted data may experience fading and thermal noise, which may cause distortion of the data. After receiving the distorted data, the receiving end performs a series of procedures in the reverse order. A demodulation operation of converting the data mapped to the symbol into a bit string is performed, and the distorted data is restored to the original data through a channel decoding process.

The apparatus for performing channel coding generates a parity check derived from an H matrix or an H matrix, which is a parity check matrix used to generate parity bits to be added to input data (Systematic Bits). It stores G matrix, which is a parity check generate matrix. That is, the transmitting end includes an encoder for generating parity bits through the H or G matrix and the input data. The apparatus for performing channel decoding checks whether the inputted data (Systematic Bits) are properly recovered through the H matrix and the operation of the received data (distorted Systematic Bits + Parity Bits). Rerun

The modulation includes Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16-QAM), 64-QAM, 256-QAM, and the like. For example, 16-QAM maps a sequence of data that has undergone Channel Encoding procedure to one symbol in units of 4 bits during modulation. In demodulation, 16-QAM demaps one symbol of data received through a wireless channel into four bits.

Hereinafter, a data retransmission scheme that can be used with the present invention will be described. The type of the data retransmission scheme is various. Hereinafter, a hybrid automatic repeat request (HARQ) scheme will be described. HARQ is a technology that combines ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) codes. In the ARQ scheme, when an error is detected in data received at a receiver, the receiver requests a retransmission to a transmitter. ARQ techniques include Stop-And-Wait, Selective Repeat, and Go-Back-N, depending on the retransmission method. In the Stop-And-Wait scheme, as shown in FIG. 2, when the transmitting end transmits data and the receiving end receives an acknowledgment (ACK) message indicating that data has been successfully received at the receiving end, the transmitting end transmits the next data and the receiving end receives the data. If a NACK message is received from the terminal that data has not been successfully received, the method fails to send the data again.

On the other hand, in the Go-Back-N method, the transmitting end first sends N pieces of data, and sequentially receives ACK messages from the receiving end. 3 shows a case where N = 7, where the number N of data sent without receiving an ACK is called a window size. When the transmitting end receives the NACK message for the k-th data, the transmitter sequentially transmits data from the k-th data.

4 shows a Selective Repeat method. In the Selective Repeat method, as in the Go-Back-N method, data is transmitted with a window size of N without receiving an ACK or NACK message, and selectively retransmission is performed only for data receiving the NACK message. Perform.

In the above-described HARQ scheme, when retransmission is performed in the ARQ scheme, the HARQ scheme is a method of combining the transmitted data and the retransmitted data and restoring the data through an FEC code. Divided into Chase Combining technique is a method of increasing the reception success rate for the data at the receiver by increasing the reception signal to noise ratio (SNR) by combining the transmission data and retransmission data at the receiver as shown in FIG.

On the other hand, the Incremental Redundancy technique (hereinafter referred to as 'IR technique'), when retransmitted by the transmitter as shown in FIG. It is a method of increasing reception success rate by lowering a code rate of data.

Hereinafter, the LDPC code will be described. The concept of the LDPC code is as follows.

을 만족하도록 부호가 구성된다는 점이다. 이 선형 부호의 일종으로서, 최근에 주목받는 LDPC 부호는 1962년 Gallager에 의하여 처음 제안되었다. 이 부호의 특징으로는 패리티 체크 행렬의 원소가 대부분 0으로 이루어지고, 0이 아닌 원소의 수는 부호 길이에 비하여 적은 수를 가지도록 하여 확률을 기반으로 한 반복적 복호가 가능한 점이다. 처음 제안된 LDPC 부호는 패리티 체크 행렬을 비체계적인(non-systematic) 형태로 정의하였고, 그것의 행과 열에 균일하게 적은 무게(weight)를 갖도록 설계되었다. The linear code can be described by the generation matrix G or parity check matrix H. The characteristic of linear code is that for all codewords c,

The sign is constructed to satisfy. As a form of this linear code, a recent notable LDPC code was first proposed by Gallager in 1962. The characteristic of this code is that the elements of the parity check matrix are mostly 0, and the number of non-zero elements has a smaller number than the code length, so that it is possible to perform iterative decoding based on probability. The first proposed LDPC code defines the parity check matrix in a non-systematic form and is designed to have a uniformly low weight in its rows and columns.

Here, the weight means the number of 1s included in a column or a row in the matrix.

Since the density of nonzero elements on the parity check matrix H of the LDPC code is small, the decoding complexity is low. In addition, the decoding performance is also better than the existing codes, showing a good performance close to Shannon's theoretical limit. The LDPC code, however, was a hardware technology that was difficult to implement at the time and has not attracted much attention for more than 30 years. In the early 1980s, a method of iterative decoding using a graph was developed, and various algorithms were developed to actually decode the LDPC code using the graph. The sum-product algorithm can be extracted as the representative algorithm.

Hereinafter, the features of the LDPC code will be described. LDPC codes have high error correction performance, which allows for an improvement in communication speed and capacity. The LDPC code may be applied to a high speed wireless LAN capable of transmitting hundreds of Mbit / s in combination with a multiple input multiple output (MIMO) system, and may be applied to high speed mobile communication having a transmission speed of 1 Mbit / s or more at 250 km / h. It can also be applied to optical communication of 40Gbits / s or more. In addition, the high error correction performance of the LDPC code may improve the transmission quality, thereby enabling quantum encrypted communication that reduces the number of retransmissions in a low quality communication path. In addition, due to the low complexity and excellent loss compensation of the LDPC code, lost packets can be easily recovered, which makes it possible to transmit content of the same quality as TV quality through the Internet and mobile communication. Due to the wide coverage and large capacity of LDPC, 10GBASE-T transmissions up to the 100m range, previously considered impossible, are possible with LDPC codes. At the same time, the transmission capacity of a single satellite transmitter in the 36MHz band can be increased by 1.3 times to 80Mbit / s. These advantages are being adopted as the next generation channel coding method in IEEE802.16 system and IEEE802.11 system for high frequency efficiency.

The structured LDPC is described below.

In order to use the LDPC code includes a matrix H to use, uses a parity check matrix H is most 0 and a part 1 of an element (elemnet), the H matrix, since the size of the H matrix size by more than 10 ⁵ bits It requires a large amount of memory to represent. The structured LDPC technique is a method of representing elements of the H matrix used for LDPC encoding and decoding as sub-blocks having a constant size as shown in FIG. 7. In IEEE802.16e, the subblock is represented by one integer index to reduce the size of memory required to store the H matrix. The subblock may be various matrices, for example, a permutation matrix of a constant size.

In the structured LDPC technique, instead of storing a matrix of 1 or 0 in a specific memory, only one integer (that is, an index) needs to be stored. Can be reduced.

For example, when the size of the codeword reflected in the IEEE802.16e standard is 2304 and the code rate is 2/3, the model matrix used for LDPC encoding / decoding is shown in FIG. Same as 8.

As shown in FIG. 8, the structured LDPC matrix of IEEE802.16e consists of -1, 0 and positive integer elements. -1 is a zero matrix of all elements 0 and 0 represents an identity matrix. Positive integer elements other than -1 and 0 are permutation matrices in which the identity matrix is shifted to the right by a positive integer. That is, when the constituent elements of the matrix are three, the permutation matrix is expressed by shifting the unit matrix three times to the right.

9 is a diagram illustrating a method of expressing a matrix according to the aforementioned positive integer, that is, shift number. When a specific H matrix is structured and expressed as a matrix of 4 * 4 size (that is, a sub block), if the specific sub block is denoted as 3, the sub block becomes the matrix of FIG.

Hereinafter, the LDPC encoding method will be described.

In the general LDPC encoding method, a generation matrix G is derived from an LDPC parity check matrix H to encode an information bit. In order to derive the generation matrix G, the inspection matrix H is configured in the form of [P ^T : I] through a Gaussian Reduction method. When the number of information bits is k and the size of an encoded codeword is n, the P matrix is a matrix in which the number of rows is k and the number of columns is nk, and I is K is the identity matrix whose k column size is k.

The generation matrix G becomes a [I: P] matrix when the check matrix H is expressed as [P ^T : I]. If the encoded information bits of k-bit size are represented in a matrix, the number of rows is 1 and the number of columns is k. In this case, the code word c is described as follows.

In the above formula, x represents a systematic part and xP represents a parity part.

)을 이용하여, 상기 수학식 1에서 H^T을 곱하면, 하기 수학식 2 같은 수학식을 얻을 수 있다. 하기 수학식 2에 부합하는 패리티 비트를 정보 비트(x) 뒤에 추가하여 코드워드 c를 얻을 수 있다. On the other hand, in the case of encoding by the Gaussian Reduction method as described above, a large amount of calculation is performed, and a method of directly encoding the H matrix without inducing the G matrix by designing the shape of the H matrix into a special structure. Use That is, H ^{T in the} form of a transpose of the G matrix and the H matrix. The product of 0 (that is,

By multiplying H ^T by Equation 1, Equation 2 can be obtained. A codeword c may be obtained by adding a parity bit corresponding to Equation 2 after the information bit x.

Hereinafter, the LDPC decoding method will be described.

The coded data in the communication system includes noise in the process of passing through the wireless channel of FIG. 1, and the receiving end represents a process of decoding data through the procedure of FIG. 10. The decoding block of the receiving end obtains the information bit (x) from the received signal (c ') with noise added to the coded code (c), and finds it using the property of cH ^T = 0. That is, when the received codeword is c ', the value of c'H ^T is calculated, and if the result is 0, the first k bits in c' are determined as the information bits x. If the value of c'H ^T is not 0, a decoding technique such as a sum-product algorithm through a graph is used to find c 'whose value of c'H ^T satisfies 0. Recover bit (x).

Hereinafter, the code rate of the LDPC code will be described.

In general, a code rate (R) is as follows when the size of the information bit is k and the size of the codeword actually transmitted is n.

R = k / n

The code rate is as follows when the row size of the H matrix required for LDPC encoding and decoding is m and the size of the column is n.

R = 1-m / n

As described above, in the conventional LDPC code, since the encoding and decoding are performed by the H matrix, the structure of the H matrix is very important. That is, since the performance of encoding and decoding is greatly affected by the structure of the H matrix, the design of the H matrix is most important.

In case of performing communication using LDPC code, there is a problem in applying a retransmission scheme. That is, since the parity check matrix used during initial transmission and retransmission following NACK transmission is different, there is a problem in that all of the codewords need to be retransmitted when performing retransmission according to NACK.

The present invention has been proposed to solve the above-described problems of the prior art, and an object of the present invention is to propose a method of applying a retransmission scheme when encoding is performed using a plurality of parity check matrices.

Another object of the present invention is to propose a decoding method that can be applied to retransmission using a plurality of parity check matrices.

Another object of the present invention is to provide an LDPC decoding method that can apply various retransmission schemes such as HARQ.

According to an aspect of the present invention, there is provided a method of performing LDPC decoding using a parity check matrix, the method comprising: receiving a codeword encoded with an information bit by a first parity check matrix from a transmitting end; Transmitting a NACK signal according to a result of decoding the received codeword by the first parity check matrix; Receiving a retransmission signal for the NACK signal from the transmitting end; And decoding the first portion of the received codeword by a second parity check matrix using the retransmission signal, wherein the retransmission signal is the second portion of the second portion of the information bits. And parity bits generated by the parity check matrix.

Preferably, when the decoding is successful by the second parity check matrix,

The method may further include re-decoding the received codeword by the first parity check matrix using the decoded first portion.

The receiving end according to the present invention comprises: a radio module for receiving a signal transmitted from a transmitting end and transmitting a control signal for requesting retransmission to the transmitting end; A memory for storing a codeword transmitted by the transmitting end and a plurality of parity check matrices; And a decoding module for acquiring a signal from at least one of the radio module and the memory, performing LDPC decoding, and determining whether to transmit a NACK signal according to the decoding result.

The receiving end according to the present invention includes a plurality of parity check matrices and performs LDPC decoding. The receiving end receives and decodes the data first transmitted from the transmitting end. The data includes information bits and parity bits. In case of failure by decoding the data, a NACK signal is transmitted to the transmitting end.

The construction, operation and effects of the present invention will be embodied by one embodiment of the present invention described below. Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

According to the structured LDPC described above, a matrix representing a parity check matrix with a subblock having a specific size (for example, z * z size) is called a model matrix. Each sub block of the model matrix may be extended to various kinds of matrices by a specific index, and the model matrix has the index as a component of the model matrix. Each sub block of the model matrix may be determined in various ways according to the index. Hereinafter, it is assumed that the index is a shift number for a unit matrix of a specific size z * z. In addition, when the index is -1, the sub block having the index of -1 is a zero matrix of a specific size z * z.

The model matrix is extended to a specific parity check matrix according to the index, so that encoding and decoding are performed by the model matrix, and that encoding and decoding is performed by a specific parity check matrix generated by the model matrix. Means.

11A through 11C are block diagrams illustrating a method of performing decryption according to an embodiment of the present invention. Each block of FIGS. 11A to 11C refers to the sub block. That is, the example of decoding according to FIGS. 11A-11C is based on the model matrix. However, since the decoding according to the present invention may be performed by a model matrix or a parity check matrix, the present invention is not limited to the example of FIGS. 11A to 11C. Each block of FIGS. 11A-11C may have any index (ie, shift number).

The decoding method according to the present embodiment may be performed at a receiving end having different parity check matrices. The receiving end has the same parity check matrix or model matrix as the transmitting end performing LDPC encoding, and performs decoding using this matrix.

Hereinafter, the decoding method according to FIG. 11A will be described.

First, the transmitting end performs encoding by using a specific first matrix. The particular first matrix comprises an information word portion A corresponding to the information bits one-to-one and a parity portion B for generating parity bits. For convenience of explanation, at least one information bit corresponding to the information word portion A of the first matrix is referred to as a first information bit a, and is generated by the parity portion B of the first matrix. The at least one parity bit being referred to is referred to as a first parity bit (b). The transmitting end transmits a codeword including the first information bit a and the first parity bit b to the receiving end. In order to transmit the codeword, various modulation methods may be applied and various antenna techniques may be applied.

The receiving end may obtain a codeword by receiving a signal transmitted by the transmitting end. The first information bit and the first parity bit included in the codeword are distorted by the channel. Therefore, the codeword acquired by the receiving end includes a distorted first information bit a 'and a distorted first parity bit b'. The receiving end preferably stores the distorted first information bit a 'in a separate memory. The receiving end performs a syndrome check on the distorted first information bit a 'and the first parity bit b'. Since the LDPC code is a code capable of error checking and error correction, decoding may be performed to restore the distorted first information bit a 'to the first information bit a without distortion. If the reception end fails in the synthesis check (syndrome check fail), the NACK (Negative Acknowledge) signal is transmitted to the transmitting end.

The transmitting end receiving the NACK signal performs encoding using a specific second matrix. The transmitting end first tries to encode to transmit the first information bit (a). After the transmitting end receives the NACK, the second end of the information bit (a _p ) corresponding to any one of the first information bit (a _p ) to try to encode again. The second matrix includes an information word portion C corresponding to the information bits one-to-one and a parity portion D for generating parity bits. The second information bit a _p corresponds to any part of the first information bit a, and corresponds one-to-one to the information word part C of the second matrix. At least one parity bit generated by the parity portion D of the second matrix is called a second parity bit d.

The transmitting end transmits the second parity bit d. That is, the retransmission signal for the NACK signal is the second parity bit (d). The receiving end obtains the second parity bit d 'distorted by the wireless channel.

As described above, the receiving end may store the distorted first information bit a 'in a separate memory. The receiving end performs decoding through a first portion of the distorted first information bits a 'and a distorted second parity bit d' stored in a memory. Hereinafter, a first portion of the distorted first information bits a 'is referred to as an a _p ' bit. The distorted first information bit a 'is divided into the a _p ' bit and the remaining a _r 'bit. The receiving end decodes the a _p 'bit and the distorted second parity bit d' by the second matrix. If decryption is successfully performed at the receiving end, that is, if the succession of the succession test (syndrome check success) or the CRC check success (CRC check success) is performed A (Procedure A) of FIG. 11A. On the other hand, when the receiving end does not successfully decode, the NACK signal is transmitted to the transmitting end.

Hereinafter, the process A will be described.

The process A is a case where the decoding is successful by the second matrix. Since the LDPC code is a code capable of error correction as well as error detection, the a _p 'bit is corrected to a _p ''bit through a decoding process. The a _p '' bit is a known value because the bits have been successfully decoded, and the a _p '' bit is a unknown value since the bits have not been successfully decoded. In step A, decoding of the distorted first information bit a 'is performed again. However, if the decoding of the distorted first information bit a 'is performed, the same result is obtained. Therefore, decoding is performed on the currently unknown value a _r 'bit and the known value a _p ''bit. In summary, in step A, decoding is performed by the first matrix, but decoding is performed on a _r 'bit, a _p ''bit, and b' bit.

If the result of the decoding through the process A is successful, the transmitting end recovers the first information bit (a) first transmitted by the transmitting end, and thus the retransmission scheme is stopped. If the result of decoding through the A process is unsuccessful, the first information bit (a) transmitted by the transmitting end cannot be recovered, and thus the retransmission scheme is stopped. If the process A fails, it is preferable to perform encoding and decoding with a matrix other than the first matrix.

Hereinafter, a case in which the decoding end by the second matrix fails in the receiving end and transmits a NACK signal to the transmitting end will be described with reference to FIG. 11B.

The transmitting end encodes a specific third information bit using a third matrix. The third information bit is part of the first information bit a or the second information bit a _p . According to a specific rule, when the second information bit a _p is divided into a _p0 bit and a _p1 bit, the third information bit may be the a _p1 bit. The third matrix includes an information word part E and a parity part F that correspond one-to-one to the third information bit. The transmitting end transmits the third parity bit f, which has been encoded using the third matrix, to the receiving end. The receiving end obtains a distorted third parity bit f '.

The receiving end performs decoding using the third matrix. As described above, the receiving end stores the distorted first information bits a 'in a separate memory. The receiving end performs decoding through a second portion of the distorted first information bits a 'and the distorted third parity bits f'. As described above, the distorted first information bit a 'is divided into the a _p ' bit and the remaining a _r 'bit according to a specific rule. In addition, the a _p 'bit may be divided into a _p0 ' bit and a _p1 'bit according to a specific rule. In this case, a second portion of the distorted first information bit a 'is referred to as a _p1 ' bit.

The receiving end decodes the a _p1 'bit and the distorted third parity bit d' by the third matrix. If the decoding process is successfully performed at the receiving end, that is, if the succession of the check of the syndrome (syndrome check success) or the success of the CRC check (CRC check success), the process B of FIG. 11B is performed. On the other hand, if the receiving end has not successfully decoded, the NACK signal is transmitted to the transmitting end.

Hereinafter, the process B will be described.

The process B is a case where the decoding is successful by the third matrix. In this case, according to the error correction characteristic of the LDPC code, the a _p1 'bit is corrected to a _p1 ''bit through a decoding process. The a _p1 '' bit is a known value because the bits have been successfully decoded, and the a _p1 '' bit is a unknown value because the bits have not been successfully decoded yet. In the process B, the decoding on the a _p 'is performed again. However, since decoding of the distorted first information bit a _p ′ results in the same result, decoding of the current unknown value a _p0 ′ and a known value a _p1 ″ bit is performed. In summary, in the process B, decoding is performed by the second matrix, but decoding is performed on a _p0 'bit, a _p1 ''bit, and d' bit.

If the result of decoding through the process B is successful, the receiving end recovers the a _p 'bit. As described above, since the distorted first information bit a ′ may be divided into the a _p ′ bit and the a _r ′ bit, when the a _r ′ bit is recovered, the distorted first information bit a a. ') Can restore everything. Therefore, the receiving end performs process A of FIG. 11A again. That is, decoding is performed using the first matrix with respect to the information bits recovered through the process B and the a _r 'bits and the b' bits stored in the memory.

If the result of decoding through the B process is unsuccessful, the first parity bit (a) transmitted by the transmitting end cannot be recovered, and thus the retransmission scheme is stopped.

Hereinafter, a case in which a decoding by the third matrix fails at the receiving end and transmits a NACK signal to the transmitting end will be described with reference to FIG. 11C.

The transmitting end encodes a specific fourth information bit using a fourth matrix. The fourth information bit is part of the first information bit or the a _p1 bit. According to a specific rule, when the a _p1 bit is divided into a _p10 bit and a _p11 bit, the fourth information bit may be divided into the a _p11 bit. The fourth matrix includes an information word part (G) and a parity part (H) corresponding one-to-one to the fourth information bit. The transmitting end transmits the fourth parity bit h, which has been encoded using the fourth matrix, to the receiving end. The receiving end obtains a distorted fourth parity bit h '.

The receiving end performs decoding using the fourth matrix. As described above, the receiving end stores the distorted first information bits a 'in a separate memory. The receiving end performs decoding through a third portion of the distorted first information bits a 'and the distorted fourth parity bits h'. As described above, the distorted first information bit a 'is divided into the a _p ' bit and the remaining a _r 'bit according to a specific rule. In addition, the a _p 'bit may be divided into a _p0 ' bit and a _p1 'bit according to a specific rule. In addition, the a _p1 'bit is divided into a _p10 ' bit and a _p11 'bit according to a specific rule. In this case, a third portion of the distorted first information bit a 'is referred to as a _p11 ' bit.

The receiving end decodes the a _p11 'bit and the distorted fourth parity bit h' by the fourth matrix. If the decoding process is successfully performed at the receiving end, that is, if the succession of the check of the syndrome (syndrome check success) or the success of the CRC check (CRC check success), the process B of FIG. 11B is performed. On the other hand, if the receiving terminal does not successfully decode, it is determined that normal reception is impossible and the retransmission scheme is stopped.

The receiving end according to the example of FIGS. 11A to 11C uses four parity check matrices. In addition, when decoding is performed using each parity check matrix, decoding is performed by selecting a part of the first received distorted information bits a '. The method of selecting some of the first received distorted information bits a 'follows a certain rule. The above rule also applies to a method of selecting information bits used when generating parity bits retransmitted at the transmitting end.

Hereinafter, a method of selecting some of the first received distorted information bits a 'will be described.

12 is a block diagram illustrating a method of selecting information bits used when encoding and decoding according to the present embodiment.

12 shows 45 bits of distorted information bits received at the receiving end and 45 bits of information bits transmitted at the transmitting end. The receiving end may classify the 45-bit distorted information bits as shown in FIGS. 12 (a), 12 (b), 12 (c), and 12 (d). In addition, the transmitter may classify the 45-bit information bits as shown in Figs. 12 (a), 12 (b), 12 (c), and 12 (d). That is, FIG. 12 illustrates four methods of classifying 45-bit information bits transmitted and received by the transceiver.

As shown in FIG. 12A, when the transmitting end transmits the first information bit a and the corresponding parity bit (not shown), the receiving end receives the distorted first information bit a '. Decode If the transmitting end performs retransmission after the receiving end fails to decode the distorted first information bit a 'and sends a NACK, the receiving end reconstructs the retransmitted bit and the illustrated a _p ' bit. Decrypt That is, decoding is performed by selecting a _p 'bits among the a' bits. In addition, if the transmitting end retransmits after the receiving end fails to decode the a _p 'bit and sends a NACK, the receiving end decodes the retransmitted bit and the a _p1 ' bit. . In addition, if the transmitting end performs retransmission after the NPL fails to decode the a _pl 'bit, the receiving end performs decoding on the retransmitted bit and the illustrated a _p11 ' bit.

The receiving end stores the distorted first information bit a 'in a memory provided in the receiving end, and when the decoding operation is performed, the receiving end accesses the memory and partially selects the first information bit a'. Use bits.

The rules for determining the information bits used by the receiving end for the multi-stage decoding operation and the rules for determining the information bits used for the multi-stage encoding operation are the same. As shown in FIG. 12, when the transmitting end performs encoding on the second information bit a _p , the receiving end transmits a _p corresponding to the second information bit among the a 'bits stored in the memory. 'Read bit. In addition, when the transmitting end performs encoding on the third information bit a _p1 and transmits it, the receiving end reads a _p1 'bit corresponding to the third information bit among the a' bits stored in the memory.

The four division methods illustrated in FIG. 12 may be determined according to the parity check matrix. That is, when decoding is performed by using a specific first parity check matrix, decoding may be performed by selecting a distorted information bit according to the method of FIG. 12 (a). In addition, when decoding is performed using a specific second parity check matrix, decoding may be performed by selecting a distorted information bit according to the method of FIG. 12 (b).

Although parity check matrices used for decoding the information bits of (a), (b), (c), and (d) of FIG. 12 may all be different, information bits that a transmitting and receiving end should use for encoding and decoding. Since the location of the signal is known, even if the transmitter retransmits only the parity bits without retransmitting the information bits, decoding can be performed using the retransmitted parity bits.

FIG. 13 is a block diagram illustrating still another example of a method of selecting information bits used when encoding and decoding according to the present embodiment.

13 illustrates another example of dividing 45 bits of information bits into four methods. That is, when the receiving end receives all of the 45 bits (a ') and the first parity bit (not shown) corresponding thereto as shown in FIG. 13 (a), ACK / NACK by decoding the a' bit and the parity bits. Send a signal. If the NACK signal is transmitted, the receiving end receives the second parity bit (not shown) generated by the a _p bit of FIG. 13 (b), and the second parity bit of FIG. 13 (b). The ap 'bit can be decoded.

14 is a block diagram illustrating still another example of a method of selecting information bits used when encoding and decoding according to the present embodiment.

According to the present embodiment, the receiving end requests retransmission from the transmitting end and performs decoding using information bits different from the former. 12 to 14 only illustrate an example of various methods of selecting information bits according to the present embodiment, and the present invention is not limited to the specific numerical values of FIGS. 12 to 14.

11A to 11C perform decoding according to four parity check matrices, and examples of FIGS. 12 to 14 select received bits according to the four parity check matrices. The four parity check matrices may be separate parity check matrices. That is, even if the characteristics of the four parity check matrices are different from each other, the decoding method according to the present embodiment can be applied. However, it is preferable that the plurality of parity check matrices used in this embodiment are matrices corresponding to the plurality of code rates. 11A through 11C perform decoding using the first to fourth matrices. The first matrix corresponds to a specific first code rate, the second matrix corresponds to a specific second code rate, the third matrix corresponds to a specific third code rate, and the fourth matrix corresponds to a specific fourth code rate. It is preferable to correspond.

If the first code rate is the highest code rate, the second code rate is the second highest code rate, the third code rate is the third high code rate, and the fourth code rate is the fourth high code rate, The decoding method according to the present embodiment can be applied to the IR technique.

That is, the receiver performs decoding by using the first matrix, and transmits a NACK signal to the transmitter when decoding fails. Thereafter, the transmitting end retransmits only parity bits without transmitting information bits again. In case of retransmission, the code rate is changed from the first code rate (for example, 3/4) to the second code rate (for example, 2/3) for correct decoding at the receiving end. The receiving end performs decoding using the second matrix. If decoding fails, a NACK signal may be transmitted to the transmitting end instructing to encode at a lower code rate (that is, a third code rate or a fourth code rate). In addition, when decoding is successfully received by receiving the parity bit corresponding to the second code rate, process A of FIG. 11A may be performed to decode the codeword corresponding to the first code rate. In summary, the receiving end according to the present embodiment decodes the codeword corresponding to the higher code rate if the decoding succeeds, and decodes the codeword corresponding to the lower code rate if the decoding fails.

The decoding method according to this embodiment may be based on a structured LDPC code. The LDPC code structured as described above is a method of representing a parity check matrix in sub-blocks having a specific size (for example, z * z size). That is, the parity check matrix is extended from a specific model matrix. The present embodiment selects and decodes various information bits. If the z factor of the sub-block is varied, decoding of information bits of various sizes is advantageous.

The specific code rate and the size and weight of the matrix are just examples for describing the present invention, and the present invention is not limited to the above-described specific numerical values. That is, the conditions such as the code rate can be freely changed.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

Hereinafter, the effect of the present invention will be described.

The decoding method according to the present invention proposes a method of applying a retransmission scheme when encoding is performed using a plurality of parity check matrices.

According to the present invention, it is possible to succeed in decoding from a low code rate. That is, the unstable channel information may be decoded on the channel information based on the stable channel information.

The problem of conventional LDPC decoding is that the complexity of decoding increases rapidly when the number of repetitions increases. However, the present invention proposes a method for quickly converting unstable channel information into stable channel information. Therefore, the cost of the overall system can be reduced by using the decoding method according to the present invention.

Claims (9)

In a method for performing LDPC decoding using a parity check matrix, Receiving a codeword obtained by encoding an information bit by a first parity check matrix from a transmitting end; Transmitting a NACK signal according to a result of decoding the received codeword by the first parity check matrix; Receiving a retransmission signal for the NACK signal from the transmitting end; And Decoding the first portion of the received codeword by a second parity check matrix using the retransmission signal; The retransmission signal includes a parity bit generated by the second parity check matrix with respect to a second portion of the information bits. The method of claim 1, If decoding fails by the second parity check matrix, Transmitting a NACK signal to the transmitting end Decoding using a plurality of parity check matrix, characterized in that further comprising The method of claim 1, If decoding is successful by the second parity check matrix, Re-decoding the received codeword by the first parity check matrix using the decoded first portion Decoding using a plurality of parity check matrix, characterized in that further comprising The method of claim 3, The re-decoding step, Decoding at least one bit corresponding to a portion of the received codeword except for the first portion and the decoded first portion. A method of decoding using a plurality of parity check matrices The method of claim 1, The received codeword is stored in memory A method of decoding using a plurality of parity check matrices The method of claim 1, The first parity check matrix corresponds to a specific first code rate, The second parity check matrix is a method of decoding using a plurality of parity check matrix, characterized in that corresponding to a specific second code rate The method of claim 6, The first code rate is higher than the second code rate decoding method using a plurality of parity check matrix, characterized in that The method of claim 1, At least one of the first parity check matrix and the second parity check matrix is decoded using a plurality of parity check matrices, wherein the at least one of the first parity check matrix and the second parity check matrix is extended from a specific model matrix. In the LDPC decoding apparatus, A wireless module for receiving a signal transmitted from a transmitting end and transmitting a control signal for requesting retransmission to the transmitting end; A memory for storing a codeword transmitted by the transmitting end and a plurality of parity check matrices; And A decoding module for acquiring a signal from at least one of the wireless module and the memory to perform LDPC decoding and determining whether to transmit a NACK signal according to the decoding result. Including but not limited to, The decoding module decodes a codeword transmitted by the transmitting end into a first parity check matrix and decodes a part of the retransmitted parity bit and the codeword into a second parity check matrix. LDPC decoding device.

Images