KR20090084641A - Method for determining transport block size and signal transmission method using the same - Google Patents

Abstract

A method for determining a transport block size and a signal transmitting method using the same are provided to improve the efficiency of a system by minimizing the attached dummy bit in a rate matching process. A transmission block is mapped to the code block corresponding to the determined number by determining the number of the code block to be mapped. A CRC is attached to the code block. An encoding is performed in each code block attaching the CRC through a turbo encoder including the internal interleaver. The encoded code block is transmitted. The size of the transmission block is one among the predetermined transmission block size combination so that the sum of the length of the CRC attached to the arbitrary code block and the arbitrary code block corresponds to the length of the input bit of the internal interleaver.

Description

METHOD FOR DETERMINING TRANSPORT BLOCK SIZE AND SIGNAL TRANSMISSION METHOD USING THE SAME}

Hereinafter, a method of efficiently determining the size of a data block or a transport block in a wireless communication system and a method of transmitting a signal using the same will be described.

In a general communication system, information transmitted from a transmitter is transmitted through a coding using a forward error correction code to correct an error occurring in a channel at a receiver. The receiving end demodulates the received signal and then decodes the error correcting code to restore the transmission information. In this decoding process, errors in the received signal caused by the channel are corrected.

There are various kinds of error correcting codes, but hereinafter, turbo code will be described by way of example. The turbo code consists of a recursive systematic convolution encoder and an interleaver. There is an interleaver for facilitating parallel decoding in actual implementation of the turbo code. One kind of this is a quadratic polynomial permutation (QPP) interleaver. Such a QPP interleaver is known to maintain good performance only for certain data block sizes. Here, the "data block" means block unit data transferred from an upper layer to the physical layer and may be referred to as a "transport block."

On the other hand, the performance of the turbo code is known to be good as the data block size increases, in the actual communication system, for the convenience of the actual implementation, the data block of more than a certain size is divided into several small data blocks to perform the encoding (encoding) . The divided small data block is called a code block. Code blocks generally have the same size, but due to the size limitation of the QPP interleaver, one code block of several code blocks may have a different size. Interleaving is performed to reduce the effects of burst errors that occur during transmission on a wireless channel after an error correction encoding process in units of code blocks having a predetermined interleaver size. And it is mapped to the actual radio resources and transmitted.

Since the amount of radio resources used during the actual transmission is constant, rate matching should be performed on the encoded code blocks. Generally, rate matching consists of puncturing or repetition. Rate matching may be performed in code block units encoded such as WCDMA of 3GPP. Alternatively, the systemic part and the parity part of the encoded code block may be separated and performed separately.

1 is a view for explaining the basic operation of the turbo encoder.

As shown in FIG. 1, a turbo encoder receiving one code block may divide the code block into an information part S and a surplus parts P1 and P2. The separated information portion S and the surplus portions P1 and P2 may be interleaved through a subblock interleaver, respectively, and then stored in a circular buffer.

Although FIG. 1 illustrates performing rate matching by separately separating an information part and a redundant part of a code block, the present invention is not limited thereto. Code rate is assumed to be 1/3.

Although various transport block sizes should be defined according to service types of higher layers, it is preferable to quantize transport block sizes in order to efficiently perform such signaling of various transport block sizes. When quantization, a dummy bit is added to match a source data block transmitted from an upper layer to a data block size of a physical layer, and quantization is preferably performed so that the amount of dummy bits added is minimal.

According to an aspect of the present invention, when encoding a turbo block by transmitting a transport block received from a higher layer and performing encoding by a turbo encoder, a method of increasing system efficiency by minimizing dummy bits attached in a rate matching process as described above. To provide.

According to an aspect of the present invention for solving the above problems, the transmission block divided into code block units is set to match the input bit length of the internal interleaver of the turbo encoder, in which case the CRC is attached to the transport block and code block units. In consideration of this, a transport block size is set and a method for transmitting a signal using the same is provided.

According to a specific embodiment, determining the number of code blocks to be mapped to a transport block and mapping the transport blocks to code blocks corresponding to the determined number; Attaching a CRC to each of the code blocks; Performing encoding through a turbo encoder including an internal interleaver in each of the code blocks to which the CRC is attached; And transmitting the encoded code block, wherein the size of the transport block is equal to the sum of the length of any one of the code blocks and the length of the CRC attached to the one code block. The present invention proposes a signal transmission method corresponding to any one of a combination of transport block sizes preset to correspond to an input bit length of an interleaver.

In this case, the input bit length of the internal interleaver of the turbo encoder may be predetermined as a combination of specific bit lengths.

Under this assumption, when the number of code blocks to be mapped to the transport block is one, the size of the transport block is a value obtained by adding the length of the CRC to the input bit lengths of the internal interleaver, which are predetermined as a combination of specific bit lengths. It may correspond to any one of the transport block size combination including the.

In addition, when the number of code blocks to be mapped to the transport block is two or more under the same conditions, it is preferable that the transport block is divided into two or more code blocks having the same length and mapped.

This can be generalized as

That is, when the size of the transport block is N, the number of code blocks to be mapped to the transport block is M, the length of each of the M code blocks is N _C , and the length of the CRC is L, Size N,

N = M * N _C -L

The size of the transport block may be set to any one of transport block size combinations in which the N _C + L is set to correspond to input bit lengths of the internal interleaver, which is predetermined as a combination of specific bit lengths. This may be the case.

More specifically, the input bit length of the internal interleaver of the turbo encoder may be set to correspond to the K value according to the index "i" of Table 1 below.

TABLE 1

Under this assumption, when the number of code blocks to be mapped to the transport block is one, the size of the transport block may be any one of transport block size combinations including values obtained by adding the length of the CRC to K values of Table 1. This may be the case.

In general terms, when the size of the transport block is N, the number of code blocks to be mapped to the transport block is M, the length of each of the M code blocks is N _C , and the length of the CRC is L, The size N of the transport block,

N = M * N _C -L

The size of the transport block may correspond to any one of transport block size combinations in which the N _C + L is set to correspond to the K values in Table 1.

Further, the transport block size N is according to the number M of code blocks to be mapped to the transport block.

A selected length of combinations such as may be used.

In addition, the present embodiment includes receiving information on a modulation and coding scheme (MCS) and available resource region size from a receiving end; And determining any one of the preset transport block size combinations as the size of the transport block based on the received information, and under this condition, the size of the transport block according to the received information is set in advance. When not included in the transport block size combination, the maximum transport block size not exceeding the size of the transport block according to the received information among the preset transport block size combinations is used, or in the received information among the preset transport block size combinations. The minimum transport block size exceeding the transport block size may be used, or the transport block size having the smallest difference from the transport block size according to the received information among the preset transport block size combinations may be used.

On the other hand, another embodiment of the present invention includes the steps of attaching a first CRC of size L to a transport block of size N; Dividing the transport block to which the first CRC is attached into M code blocks having an N _C length; Attaching a second CRC having a size of L to each of the divided M code blocks; Performing encoding through a turbo encoder including an internal interleaver in the M code blocks to which the second CRC is attached; And transmitting the encoded M code blocks, wherein the size N of the transport block is:

N = M * N _C -L

The N _C + L is set to have a length of any one of the internal interleaver input bit length of the turbo encoder. (N, N _C , M, L are natural numbers)

On the other hand, another embodiment of the present invention comprises the steps of mapping a transport block of size N to one or more code blocks; Performing encoding through a turbo encoder including an internal interleaver in the one or more code blocks; And transmitting the encoded codeblock, wherein the size N of the transport block is a transport block size selected from a transport block size combination consisting of all or part of the values described in Table 2 below. N is a natural number).

TABLE 2

According to each embodiment of the present invention as described above, when performing the encoding by the turbo encoder by dividing the transport block received from the upper layer into code blocks, the dummy bit due to the internal interleaver input bit length limitation of the turbo encoder The addition can be eliminated, allowing for efficient signal transmission.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced.

The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are omitted or shown in block diagram form, centering on the core functions of each structure and device, in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

As described above, the interleaver inside the turbo code is known to show excellent performance only for a specific data block size. When the data block size is larger than a predetermined size, segmentation is performed into a plurality of code blocks. However, due to the limitation of the interleaver size as described above, the data block size may not be divided into code blocks of the same size.

However, since the channel quality indicator should be equally applied to all code blocks divided in the data block, it is preferable to divide them so that the size of the code blocks is the same. When the size of the data block or the size of the divided code block is different from the size of the turbo code internal interleaver, a dummy bit is inserted, which decreases transmission efficiency.

This requires consideration of the internal interleaver input bit length of the turbo encoder, which is a direct cause of the insertion of dummy bits, and the length of each data block while attaching a CRC to the transport block and the code block in which the transport block is divided for channel coding. Can be changed and a consideration is needed.

First, the above-described CRC attachment process will be described in detail.

A CRC for error detection is attached to a transport block delivered from an upper layer, and a CRC may be attached to each code block in which a transport block is segmented for implementation convenience.

2 and 3 are diagrams for explaining a process of attaching a CRC by dividing a long transport block into a short code block in a 3GPP system.

In a 3GPP system, a long transport block (TB) is divided into a plurality of short code blocks (CBs), followed by encoding on each of the short code blocks, and then put together again. Will be sent. In more detail with reference to each step of Figure 2 as follows.

First, a long length of a transport block goes through a CRC encoding process, and then a CRC is attached to the transport block (S101). Thereafter, the full length transport block attached to the CRC is divided into code blocks having a plurality of short lengths (S102). The CRC is attached to the long length of the transport block, and the form in which the CRC-attached transport block is divided into a plurality of code blocks is illustrated in reference numerals 201 to 203 of FIG. 3. However, if the length of the transport block received from the upper layer is less than a predetermined length configurable as one code block, substantially the maximum length of the internal interleaver of the turbo encoder (for example, 6144 bits in the 3GPP LTE system) The process of dividing may be omitted, and in this case, the process of attaching the CB CRC may also be omitted.

In the meantime, each of the plurality of code blocks having a short length is subjected to a CRC attaching process through a CRC encoding process (S103). That is, as shown by reference numeral 204 of FIG. 3, each code block includes a CRC.

In addition, the code blocks to which the CRCs are attached are input to the channel encoder and subjected to channel coding process (S104). Thereafter, each code block is transmitted to the receiver through a rate matching process (S105), a code block concatenation, and a channel interleaving process (S106).

Therefore, the following embodiment proposes to set the size of a transport block in consideration of the process of attaching the CRC of two steps as described above. In addition, in an embodiment of the present invention, when a transport block is mapped to one code block because it is smaller than or equal to a predetermined size, it is proposed to set only one CRC.

Under this assumption, first, a case in which a transport block is mapped to one code block will be described. In order to set the dummy bit attachment not necessary when the transport block is mapped to one codeword, in this embodiment, the length N plus one CRC length is equal to the internal interleaver input bit length of the turbo interleaver. I suggest setting it up. Table 3 below shows the internal interleaver input bit length combination of the turbo encoder.

TABLE 3

Therefore, in the present embodiment, when the transport block is mapped to one code block, the internal interleaver input bit length (K) of the turbo encoder as shown in Table 3 is set to the length obtained by subtracting the length of the CRC attached to the transport block. It is desirable to. Assuming that the length of the CRC attached to the transport block is 24 bits, the transport block size N when the transport block is mapped to one code block may be K-24 in Table 3 above, that is, in this embodiment The transport block size may be selected and used among the combinations shown in Table 4 below.

TABLE 4

Meanwhile, the following description will be generalized as a case in which one transport block is divided into one or more code blocks and mapped.

When a transport block is divided into two or more code blocks, as described above with reference to FIGS. 2 and 3, a transport block CRC is attached to the transport block, and a code block CRC is also attached to each of the divided code blocks. . Under this assumption, in order to eliminate the addition of dummy bits, it is preferable that the sum of the size of an arbitrary code block and the size of the CRC attached to the code block has the input bit size of the internal interleaver as shown in Table 3 above.

In addition, the present embodiment proposes to set the divided codewords to have the same size. If the size of the code blocks generated by the division of the transport block is different due to the interleaver size limitation inside the turbo encoder, as in this embodiment, the size of the transport block in advance considering the internal interleaver size of the turbo encoder This is because there is no reason to set the size of each code block differently.

A method of setting the size of a transport block according to the present embodiment under such an assumption is as follows.

4 is a diagram illustrating a principle of size setting of a transport block according to an embodiment of the present invention.

First, it is assumed that a CRC having an L length is added to a transport block TB having a size N. If the size of the transport block TB is greater than or equal to the maximum length of the internal interleaver, the transport block is divided into a plurality of code blocks CB, and in FIG. 4, M code blocks CB ₁ to CB _M having the same Nc bit length. Shown in the figure).

Meanwhile, a CRC having an L length is similarly attached to each of the M code blocks.

Thus, if the code block to be divided according to the present embodiment is set to the same length, and considering the length of the two CRC to be attached, the size N of the transport block satisfies the following relationship.

[Equation 1]

N + L * M + L = M * (Nc + L) => N = M * Nc-L

If the CRC of 24 bits in length is used, Equation 1 may be set to N = M * Nc−24.

On the other hand, the divided code block is input to the internal interleaver of the turbo encoder in the form of CRC attached to each code block. Therefore, in the present embodiment, as shown in FIG. 4, it is proposed to set the length of the CRC attached to each code block to match the input bit length K of the internal interleaver shown in Table 3 above. This is represented by the following equation.

[Equation 2]

Nc + L = K

Through this, the present embodiment proposes to use the following transport block size. Table 5 below shows a case where one transport block is mapped to 25 code blocks.

TABLE 5

Table 5 considers a case in which one transport block is divided into 25 code blocks while satisfying the conditions of Equations 1 and 2, and those skilled in the art within a range satisfying the conditions of Equations 1 and 2 Can sufficiently infer an additional transport block size to the values shown in Table 5 above.

By transmitting the signal through the embodiment of the present invention as described above, it is possible to eliminate the addition of dummy bits due to the input bit length limitation of the turbo encoder, thereby improving system performance.

Meanwhile, in consideration of both the case where the above-described transport block is mapped to one code block and transmitted and the case in which the transport block is divided into two or more code blocks and mapped, the available transport block can be represented as follows.

TABLE 6

That is, in the signal transmission method according to the present embodiment, the transport block is set to have a length corresponding to any one of the values shown in Table 6 above. Table 6 lists all possible cases as a transport block size that does not require dummy bit insertion according to the present invention. Instead of using all the values of Table 6 in consideration of signaling overhead, a subset of Table 6 is used. It can also be shared between the transmitting and receiving end.

Meanwhile, in order to actually inform the receiver of the size of the transport block, the transmitter can express the transport block size by a combination of a modulation and coding rate and an allocated resource size. The modulation and coding rate is determined by the scheduler by the channel quality indicator transmitted from the receiver, and the size of the allocated resource is also considered in consideration of resources for transmitting control information and resources for reference signal for channel estimation. Decide

5 shows an example of a resource structure.

In FIG. 5, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. Assuming a resource structure as shown in FIG. 5, assume that a resource for transmitting control information is three symbols, and assuming two transmit antennas, 120 data are transmitted in one resource block (RB). There is a resource element (RE) available for this purpose.

In this case, assuming that the modulation and coding rate are 64 QAM and 0.6504, respectively, and the number of allocated RBs is 10, the size of a data block that can be transmitted is 4658 bits. Since it exists between 4608 bits and 4672 bits in Table 3, if a rule for determining one of the two sizes is determined, the size of the data block can be determined according to various modulation and coding rates and the allocated resource size.

As in the aforementioned example, when the size of the data block that can be actually transmitted and the size of the data block that can be supported do not match, the size of the data block that can be actually transmitted can be determined by the following rule.

Iv) a method of determining the maximum supported data block size not exceeding the actual transmittable data block size;

Ii) a method of determining the minimum supportable data block size exceeding the actual transmittable data block size

Iv) a method of determining a supportable data block size that is the smallest difference from the actual transmittable data block size;

Here, the data block may correspond to a transport block when one transport block is transmitted through one code block, or may be viewed as a code block when one transport block is transmitted through two or more code blocks.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can.

Although the signal transmission method according to the above embodiments has been described with reference to the 3GPP LTE system, it can be applied by the same principle to any communication system that is given a length limitation of input bits in the encoding step and uses a predetermined combination of transport block sizes. have.

1 is a view for explaining the basic operation of the turbo encoder.

2 and 3 are diagrams for explaining a process of attaching a CRC by dividing a long transport block into a short code block in a 3GPP system.

4 is a diagram illustrating a principle of size setting of a transport block according to an embodiment of the present invention.

5 shows an example of a resource structure.

Claims (12)

Determining a number of code blocks to be mapped to a transport block and mapping the transport blocks to code blocks corresponding to the determined number; Attaching a CRC to each of the code blocks; Performing encoding through a turbo encoder including an internal interleaver in each of the code blocks to which the CRC is attached; And Transmitting the encoded codeblock; The size of the transport block may be any one of a combination of transport block sizes set in advance such that the sum of the lengths of arbitrary code blocks of the code blocks and the length of the CRC attached to the arbitrary code blocks corresponds to the input bit length of the internal interleaver. One, signal transmission method. The method of claim 1, And the input bit length of the internal interleaver of the turbo encoder is predetermined as a combination of specific bit lengths. The method of claim 2, When the number of code blocks to be mapped to the transport block is two or more, The transport block is divided into two or more code blocks having the same length, and mapped. The method of claim 2, When the size of the transport block is N, the number of code blocks to be mapped to the transport block is M, the length of each of the M code blocks is N _C , and the length of the CRC is L, The size N of the transport block, N = M * N _C -L Satisfying And the size of the transport block corresponds to any one of transport block size combinations in which the N _C + L is set to correspond to input bit lengths of the internal interleaver, which is predetermined as a combination of specific bit lengths. The method of claim 1, The input bit length of the internal interleaver of the turbo encoder is according to the K value according to index "i" of Table 1 below. TABLE 1

Signal transmission method. The method of claim 5, wherein When the size of the transport block is N, the number of code blocks to be mapped to the transport block is M, the length of each of the M code blocks is N _C , and the length of the CRC is L, The size N of the transport block, N = M * N _C -L Satisfying The size of the transport block corresponds to any one of transport block size combinations in which the N _C + L is set to correspond to the K value of Table 1. The method of claim 6, The transport block size N is according to the number M of code blocks to be mapped to the transport block.

The selected length of the combinations such as is used. The method of claim 1, Receiving information on a modulation and coding scheme (MCS) and an available resource region size from a receiving end; And Determining any one of the preset transport block size combinations as a size of the transport block based on the received information; When the size of the transport block according to the received information is not included in the preset transport block size combination, using the maximum transport block size not exceeding the size of the transport block according to the received information of the preset transport block size combination , Signal transmission method. The method of claim 1, Receiving information on a modulation and coding scheme (MCS) and an available resource region size from a receiving end; And Determining any one of the preset transport block size combinations as a size of the transport block based on the received information; When the size of the transport block according to the received information is not included in the preset transport block size combination, using the minimum transport block size that exceeds the size of the transport block according to the received information of the preset transport block size combination, Signal transmission method. The method of claim 1, Receiving information on a modulation and coding scheme (MCS) and an available resource region size from a receiving end; And Determining any one of the preset transport block size combinations as a size of the transport block based on the received information; If the size of the transport block according to the received information is not included in the preset transport block size combination, the transport block size having the smallest difference from the size of the transport block according to the received information among the preset transport block size combinations is selected. Signal transmission method used. Attaching a first CRC of size L to a transport block of size N; Dividing the transport block to which the first CRC is attached into M code blocks having an N _C length; Attaching a second CRC having a size of L to each of the divided M code blocks; Performing encoding through a turbo encoder including an internal interleaver in the M code blocks to which the second CRC is attached; And Transmitting the encoded M codeblocks, The size N of the transport block, N = M * N _C -L Has a size that satisfies The N _C + L is set to have any one of the internal interleaver input bit length of the turbo encoder. (N, N _C , M, L are natural numbers) Mapping a transport block of size N to one or more code blocks; Performing encoding through a turbo encoder including an internal interleaver in the one or more code blocks; And Transmitting the encoded codeblock, The size N of the transport block is a transport block size selected from transport block size combinations consisting of all or part of the values described in Table 2 below. TABLE 2

, Signal transmission method. (Where N is a natural number)

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