KR20080045021A - Method for a retransmission using a low density parity check code - Google Patents

Abstract

A retransmission method using an LDPC(Low Density Parity Check) code is provided to satisfy dense characteristics by using a split method for splitting a column in a high code rate. A retransmission method using an LDPC includes a first encoding process, a parity bit transmission process, and a part transmission process. The first encoding process is performed to encode transmission data to be transmitted to a receiving terminal by using a parity check matrix formed with a plurality of rows split from one row. The parity bit transmission process is performed to transmit party bits selected from the parity bits generated through the first encoding process, and the parity bit. The part transmission process is performed to transmit a part of the residual parity bits except for the selected parity bits when a NACK signal is received from the receiving terminal.

Description

Method for a retransmission using a Low Density Parity Check code}

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.

FIG. 9 is a diagram illustrating a method of expressing a matrix according to the aforementioned index, that is, a shift number.

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

FIG. 11A illustrates an example of a parent matrix used in a second method for supporting the IR scheme as a model matrix.

11B is a block diagram illustrating a method of cutting and using one mother matrix in accordance with a code rate.

12 is one mother matrix used in the present embodiment.

FIG. 13 is an example of dividing one row of the model matrix of FIG. 12 into two rows.

14 is an example of dividing one row of the model matrix of FIG. 13 into two rows.

FIG. 15 is an example of dividing one row of the model matrix of FIG. 14 into two rows.

FIG. 16 shows an example of dividing one row of the model matrix of FIG. 15 into two rows.

17 through 22 are new equivalent matrices in which rows and columns are exchanged according to this embodiment.

23 to 24 show model matrices used for decoding in this embodiment.

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

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. 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 is 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 (Information bits or Systematic Bits). Generation Matrix Contains the G 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 correctly recovered by performing an H matrix and an operation on the received data (distorted Systematic Bits + Parity Bits), and performs an operation upon recovery failure. 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 indicating that the data was not successfully received, the method fails to send the failed 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 the 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. As a representative algorithm, the sum-product algorithm can be derived.

Hereinafter, the features of the LDPC code will be described. LDPC codes have high error correction performance, which allows for improvements 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.

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. The model matrix means a parity check matrix composed of at least one subblock represented by the number of shifts described below. The model matrix may be generated by extending the parity check matrix by a method described below. Therefore, encoding and decoding by a specific model matrix is the same as encoding and decoding by a parity check matrix generated by extending from the corresponding model matrix.

As shown in FIG. 8, the structured LDPC matrix may be represented by '-1', '0' and a positive integer. When the index is '-1', it indicates a zero matrix of a specific size, and when the index is '0', it indicates an identity matrix of a specific size. In an index having a positive integer except '-1' and '0', the index represents a shift number. When a subblock is represented by an index of '1', the subblock is shifted '1' times in a specific direction in the unit matrix.

FIG. 9 is a diagram illustrating a method of expressing a matrix according to the aforementioned index, that is, a shift number. When a specific parity check matrix is structured and expressed as a matrix of 4 * 4 size (ie, a sub block), when the specific sub block is represented by an index of '3', the sub block becomes the matrix of FIG. 9.

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.

[Equation 1]

In the above formula, x denotes an information part or systematic part, and xP denotes 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.

[Equation 2]

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 receiver obtains the information bit (x) from the received signal (c ') in which noise is 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 (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.

[Equation 3]

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.

[Equation 4]

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.

Hereinafter, the problems of the prior art will be described.

In the case of retransmission according to the IR scheme, the code rate of the initial transmission and the retransmission should be different. In this case, using different model matrices in order to apply different code rates may cause a problem that the IR technique cannot be supported. For example, when the first model matrix used in the first transmission and the second model matrix used after receiving the NACK signal are different from each other, the parity bit generated by the first model matrix and the second model matrix are different. There is a problem that combined reception at the receiving end is not possible because the parity bits generated by the PBs are different.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and an object of the present invention is to propose an LDPC encoding method supporting various H-ARQ techniques.

Another object of the present invention is to propose a model matrix of improved performance.

It is a further object of the present invention to propose a retransmission scheme using a model matrix of improved performance.

Summary of the Invention

In order to achieve the above object, the present invention provides a method for performing LDPC encoding using a parity check matrix, wherein a new parity check matrix is generated by separating one row included in a specific parity check matrix into a plurality of rows. step; And performing encoding on transmission information to be transmitted to a receiving end by using the generated parity check matrix.

In addition, the present invention provides a method for performing retransmission by using an LDPC code, comprising: performing a first encoding on transmission information to be transmitted to a receiving end by using a parity check matrix including a row in which a plurality of rows are combined; step; Transmitting the encoded transmission information to the receiving end; When receiving a NACK signal from the receiving end, performing a second encoding on the transmission information using a parity check matrix obtained by reconstructing the combined row into the plurality of rows; And transmitting the parity bit additionally generated by the second encoding to the receiving end, wherein the combined plurality of rows does not overlap components having a weight in an information word portion in a column direction. It is characterized by.

Work of invention Example

The construction and operation 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.

In general, two methods have been proposed to support the incremental redundancy (IR) scheme for LDPC codes.

The first method is a puncturing method for puncturing at least one of an information bit and a parity bit included in an LDPC codeword generated by the LDPC encoding method. The puncturing method is preferably performed on parity bits.

By performing the puncturing technique, the code rate can be adjusted. That is, since the code rate is adjusted according to Equation 4, a high code rate can be obtained by performing a lot of puncturing, and a low code rate can be obtained by performing a little puncture. This feature can be used to perform the IR technique.

The second method for supporting the IR technique is to cut a mother matrix and use it for encoding.

FIG. 11A illustrates an example of a parent matrix used in a second method for supporting the IR scheme as a model matrix.

One parent matrix may be divided and used as shown in FIG. 11B. 11B is a block diagram illustrating a method of cutting and using one mother matrix in accordance with a code rate. As shown in FIG. 11B, one mother matrix may be divided into several, and each separated matrix supports a specific code rate.

The transmitter according to the second method may cut the model matrix of FIG. 11A as shown in FIG. 11B to communicate according to a desired code rate.

This embodiment proposes a separate method distinguished from the first method or the second method described above.

More specifically, this embodiment proposes to split one row included in a given mother matrix into a plurality of rows. Rows that are separated are separated into a plurality of rows. In addition, the encoding may be performed by changing the order of the rows of the new mother matrix composed of the separated rows or by changing the order of the columns of the new mother matrix composed of the separated rows.

This embodiment generates a new model matrices using a technique of splitting one row into a plurality of rows. Since the new model matrices generated according to the present embodiment support a plurality of code rates, according to the present embodiment, various code rates can be supported without applying the puncturing technique. In addition, the IR scheme may be applied based on various code rates.

Hereinafter, a method of dividing one row into a plurality of rows according to the present embodiment will be described.

Equation 5a

One 0 One One One 0 0 One One 0 0 One One 0 0

[Equation 5b]

0 0 One 0 One 0 0 0 One 0 0 0 One One 0

One 0 0 One 0 0 0 One 0 0 0 One 0 One 0

The row of Equation 5a may be divided into two rows of Equation 5b according to the present embodiment. The row of equation (5a) has 15 columns, of which weights are 1, 3, 4, 5, 8, 9, 12, 13th component.

According to the present embodiment, when one row is divided into a plurality of rows, any one of the plurality of rows has a weight at a position where weight existed in the row before the separation. That is, the first row of Equation 5b has a weight on the third, fifth, ninth, and thirteenth components. In addition, the second row of Equation 5b has a weight on the 1st, 4th, 8th, and 12th components.

In summary, when dividing rows according to the present embodiment, the separated rows have exclusively divided components having weights in the rows before the separation.

On the other hand, even if there were no components with weight in the row before separation, the separate rows may have weight.

The row of Equation 5a does not have weight in the 14th component. However, the two rows of Equation 5b separated according to the present embodiment may all have weight in the 14th component. If a plurality of separated rows have weight at the same position, if the sum of the weights of the corresponding columns is an even number, the weights may be ignored because of the modulo operation. That is, according to the present exemplary embodiment, when the sum of the weights of the even columns becomes even, the plurality of rows may be weighted even if the rows before separation are not weighted.

In conclusion, in the case of separating the rows according to the present embodiment, the separated rows have exclusively divided components having weights in the rows before the separation. In addition, when a row is divided into a plurality according to the present embodiment, the components of a row may be adjusted to have a sum of weights of even columns.

Equation 6a

   A B C D E

One 0 One 0 0 One 0 One 0 0

Equation 6a shows one row before being separated. Also, A, B, C, D, and E are variables corresponding to the first, third, sixth, eighth, and ninth columns, respectively.

According to the structure of the row of Equation 6a, the variables A, B, C, and D must satisfy the following equation.

[Equation 6b]

A + B + C + D = 0 (mod 2)

Equation 6c

   A B C D E

One 0 0 0 0 One 0 0 One 0

0 0 One 0 0 0 0 One One 0

Equation 6c shows two rows separated according to this embodiment. Also, A, B, C, D, and E are variables corresponding to the first, third, sixth, eighth, and ninth columns, respectively.

The two rows of Equation 6c exclusively divide the first, third, sixth, and eighth components in accordance with the above-described rules of the present embodiment. In addition, the two rows of Equation 6c have weights such that the sum of the weights of the columns is equal in the same position (the ninth position) according to the rule of the present embodiment described above.

In this case, the variables A, B, C, D, and E must satisfy the following equation according to the structure of the row of Equation 6c.

Equation 6d

A + C = E (mod 2)

B + D = E (mod 2)

In this case, when the respective expressions of Equation 6d are summed, a relationship of A + B + C + D = 2E (mod 2) = 0 is established. Therefore, the equation of Equation 6a can also be obtained through Equation 6c. That is, even if the rows are separated according to the present embodiment, the solution before the separation does not change.

According to the above equation, even if the rows of the parity check matrix are separated according to the present embodiment, it can be seen that the existing solution is not modified. Therefore, the codeword corresponding to the solution satisfying the check equation Hc ^T = 0 by the unparalleled parity check matrix H is the check equation H'c ' ^T = by the parity check matrix H' separated according to the present embodiment. Satisfies zero.

The matrix of FIG. 12 is a model matrix, and an index indicated in each subblock of the matrix represents a shift number. In FIG. 12, the subblock in which the shift number is not indicated is a subblock having an index of '-1'. That is, the subblock in which the shift number is not represented represents a zero matrix.

As shown, the model matrix of FIG. 12 is composed of four rows and 24 columns. The model matrix of FIG. 12 supports a code rate of 5/6.

The model matrix of FIG. 12 is divided into an information word portion corresponding to an information bit and a parity portion corresponding to a parity bit. In Fig. 12, the column indicated by index 0 (hereinafter referred to as 'column 0') to the column indicated by index 19 (hereinafter referred to as 'column 19') are information word parts. In FIG. 12, the parity portion is a column indicated by index 20 (hereinafter referred to as 'column 20') and a column indicated by index 23 (hereinafter referred to as 'column 23').

This embodiment is characterized by splitting one row.

FIG. 13 is an example of dividing one row of the model matrix of FIG. 12 into two rows. Row 504 of FIG. 12 is divided into rows 504A and 504B of FIG. In this case, it can be seen that components having a weight of rows 0 to 23 are exclusively separated. Also, it can be seen that the shift number of '127' is added to column 24. In this case, since the sum of the weights of column 24 is even, its effect is ignored by modulo operation. Accordingly, it can be seen that the model matrix of FIG. 13 is a matrix equivalent to the model matrix of FIG. 12.

Meanwhile, the matrix of FIG. 13 supports a code rate of 4/5 because the number of rows and columns is increased by one. 13, it can be seen that various code rates can be supported without puncturing.

14 is an example of dividing one row of the model matrix of FIG. 13 into two rows. Row 503 of FIG. 13 is divided into rows 503A and 503B of FIG. In this case, it can be seen that the components having weights of columns 0 to 23 are exclusively separated. Also, it can be seen that the shift number of '119' is added to column 25. In this case, since the sum of the weights of column 25 is an even number, the influence is ignored by modulo operation. Therefore, it can be seen that the model matrix of FIG. 14 is a matrix equivalent to the model matrix of FIG. 12 or 13.

Meanwhile, the matrix of FIG. 14 supports a code rate of 20/26 since the number of rows and columns is increased by one.

FIG. 15 is an example of dividing one row of the model matrix of FIG. 14 into two rows. Row 501 of FIG. 14 is divided into rows 501A and 501B of FIG. In this case, it can be seen that the components having weights of columns 0 to 23 are exclusively separated. Also, it can be seen that the shift number of '117' is added to column 26. In this case, since the sum of the weights in column 26 is even, its effect is ignored by modulo operation. Accordingly, it can be seen that the model matrix of FIG. 15 is equivalent to the model matrix of FIGS. 12 to 14.

Meanwhile, the matrix of FIG. 15 supports a code rate of 3/4 because the number of rows and columns has increased by one.

FIG. 16 shows an example of dividing one row of the model matrix of FIG. 15 into two rows. Line 502 of FIG. 15 is divided into lines 502A and 502B of FIG. 15. In this case, it can be seen that the components having weights of columns 0 to 23 are exclusively separated. Also, it can be seen that the shift number of '113' is added to column 27. In this case, since the sum of the weights of column 27 is even, its influence is ignored by modulo operation. Accordingly, it can be seen that the model matrix of FIG. 16 is equivalent to the model matrix of FIGS. 12 to 15.

Meanwhile, the matrix of FIG. 16 supports a code rate of 20/28 since the number of rows and columns has increased by one.

The model matrix of FIGS. 13 to 16 further included nonzero components such that the sum of the columns was even when the rows were separated. In this case, it is preferable that the non-zero added component takes into account the characteristics of cycle 4 and cycle-6. In other words, the non-zero component added is preferably determined such that the number of cycles 4 and 6 is minimized.

When the model matrix of FIGS. 13 to 16 is extended to the parity check matrix, the following matrix characteristics are obtained. The following example is a case where the sub-blocks of the model matrix are 24 * 24 size.

Cycle -4 Cycle -6 Average VAR degree Fig. 12 (r = 5/6) 0 9672 3.08 Figure 13 (r = 4/5) 0 5832 3.04 Fig. 14 (r = 10/13) 0 3384 3.00 Figure 15 (r = 3/4) 0 1944 2.96 Fig. 16 (r = 5/7) 0 1056 2.93

The non-zero component added as above has fewer cycles and fewer weights than the low code rate parity check matrix.

Hereinafter, a method of performing encoding and decoding by using the model matrix according to the present embodiment will be described.

For example, a new equivalent matrix may be generated by exchanging rows and columns of the model matrix of FIG. 16. In other words, a new equivalence matrix can be created using row and column permutation techniques.

17 is a new equivalent matrix with rows and columns exchanged according to this embodiment. The model matrix of FIG. 17 may be obtained by swapping row 0 and row 1 of FIG. 16.

18 is a new equivalent matrix with rows and columns exchanged according to this embodiment. The model matrix of FIG. 18 may be obtained by exchanging columns 23 and 27 of FIG. 17.

19 is a new equivalent matrix with rows and columns exchanged according to this embodiment. By exchanging column 26 and column 20 of FIG. 18, the model matrix of FIG. 19 may be obtained.

20 is a new equivalent matrix with rows and columns exchanged according to this embodiment. The model matrix of FIG. 20 may be obtained by exchanging column 20 and column 21 of FIG. 19.

21 is a new equivalent matrix with rows and columns exchanged according to this embodiment. By exchanging columns 27 and 22 of FIG. 20, the model matrix of FIG. 21 may be obtained.

Figure 22 is a new equivalent matrix with rows and columns exchanged according to this embodiment. By exchanging columns 21 and 24 of FIG. 21, the model matrix of FIG. 22 can be obtained.

Referring to the model matrix of FIG. 22, it can be seen that the parity part is composed of a dual diagonal. That is, in the actual system, it is more efficient to use the structure of the parity parts that are continuous with each other as shown in FIG.

The transmitting end according to the present embodiment performs encoding using the mother matrix proposed in the present embodiment, and generates 'coding blocks' from columns 0 to 27. The coding block refers to a grouping of information bits and parity bits corresponding to 28 columns of a model matrix. That is, coding blocks 0 to 27 correspond to one LDPC codeword. In addition, the coding block corresponding to the information word part is called an "information word block", and the coding block corresponding to the parity part is called a "parity block".

The model matrices of FIGS. 12 to 22 are generated by row separation, row exchange, and column exchange according to the present embodiment. Accordingly, the transmitting end or the receiving end may freely design the model matrices of FIGS. 12 to 22 according to the method proposed in this embodiment after storing one model matrix. For example, the transmitter or the receiver may store only the matrix of FIG. 12 and convert the matrix of FIG. 12 into one of the matrixes of FIGS. 13 to 22 as the code rate is changed.

When encoding is performed using the model matrix of FIG. 22, 20 information word blocks corresponding to columns 0 to 19 and 8 parity blocks corresponding to columns 20 to 27 are generated. In this case, since the model matrix of FIG. 22 is exchanged for columns, one LDPC codeword has a sequential block structure as shown in Equation 7 below.

[Equation 7]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 26, 20, 27, 21, 25 , 22, 24, 23]

In Equation 7, each number represents a coding block corresponding to each column of FIG. 22.

Hereinafter, an IR technique according to the present embodiment will be described.

The transmitting end may perform encoding using the model matrix of FIG. 22. When encoding is performed according to the model matrix of FIG. 22, coding blocks corresponding to 28 columns are generated. In other words, 20 blocks corresponding to columns 0 to 19 become information word blocks, and parity blocks are generated for eight blocks corresponding to columns 20 to 27.

In this case, the transmitting end may determine to perform the initial transmission according to a code rate of 5/6 by combining various pieces of information.

To support a code rate of 5/6, 20 information word blocks and 4 parity blocks must be transmitted. Accordingly, the transmitting end generates an LDPC codeword composed of information word blocks corresponding to columns 0 to 19 and parity blocks corresponding to columns 21, 21, 22, and 23 and transmits the LDPC codeword to the receiving terminal. In other words, 20 information word blocks and 4 parity blocks may be transmitted to support a code rate of 5/6.

In summary, the transmitting end uses the codeword of Equation 8 for the first transmission.

[Equation 8]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23]

Since the current code rate is 5/6, the receiver according to the present embodiment performs LDPC decoding using the model matrix of FIG. 23. The model matrix of FIG. 23 is the same matrix as the model matrix of FIG. Therefore, decoding is performed at a 5/6 code rate.

If decoding fails after decoding with the model matrix of FIG. 23, the receiving end may transmit a NACK.

The transmitting end receiving the NACK performs a retransmission by lowering the code rate. For example, retransmission can be performed at a code rate of 20/26.

In this case, it is preferable that the transmitting end does not perform new encoding and uses only the 24th and 25th parity blocks that have already been generated for retransmission. That is, the transmitting end additionally transmits only parity blocks 24 and 25.

The receiving end performs decoding by receiving parity blocks 24 and 25 additionally transmitted. That is, decoding can be performed at a code rate of 26/20. 24 is an example of a model matrix used by a receiving end to decode retransmitted data. The matrix of FIG. 24 is the same as the matrix of FIG.

The receiving end additionally receives parity blocks corresponding to columns 24 and 25, information blocks already stored (information blocks corresponding to columns 0 to 19) and parity blocks (numbers 20, 21, Parity blocks corresponding to columns 22 and 23 are combined to perform decoding.

The above-described example is an example of performing initial transmission at a code rate of 5/6, and performing retransmission at a code rate of 20/26 when a NACK is received. The present invention also relates to a method of additionally retransmitting only a parity block as a code rate changes.

The model matrix proposed in this embodiment is only an example for explaining the present invention. Therefore, the present invention is not limited to the model matrix proposed in this embodiment.

In addition, since the specific code rate, repair of retransmission, etc. used for describing this embodiment are only examples for explaining the present embodiment, the present invention is not limited thereto.

In addition, the model matrix according to the present embodiment may be used for various communication techniques other than retransmission.

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.

Model matrices that support low code rates are sensitive to the effects of cycle-4 and cycle-6. Also, the average column degree is smaller than the model matrix supporting high code rate. That is, a low code rate model matrix has a sparse property compared to a code matrix with a high nonzero weight.

However, in order to support various code rates with one parent matrix, the upper part of the parent matrix must be dense and the lower part of the parent matrix must be structurally set. However, the present invention is designed to support sparse nonzero weights at a low code rate and to satisfy the dense property by using a splitting technique at high code rates, so that the LDPC code can be designed more efficiently.

Claims (2)

In the method for performing LDPC encoding using a parity check matrix, Generating a new parity check matrix by separating one row included in a specific parity check matrix into a plurality of rows; And Performing encoding on transmission information to be transmitted to a receiving end by using the generated parity check matrix Consists of How to perform LDPC encoding using parity check matrix In a method for performing retransmission using an LDPC code, Performing a first encoding on transmission information to be transmitted to a receiving end by using a parity check matrix in which one row is divided into a plurality of rows; Transmitting the selected part of the plurality of parity bits generated by the first encoding and the parity bits; And When receiving a NACK signal from the receiving end, transmitting any part of the parity bits except the selected part Consists of How to perform retransmission using LDPC code

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