KR101331053B1 - Apparatus and Method for Encoding using Turbo Code, and Unit and Method of Permutation - Google Patents

Abstract

The present invention discloses a coding apparatus and method using a turbo code, and a permutation substituent and permutation substitution technique. According to an embodiment of the present invention, an encoding apparatus using a turbo code may include recursive systematic convolutional codes (3 bits) input from first to third blocks each consisting of N bits to form a first surplus bit. a first encoder for outputting parity bits); A permutation substituent for permutating the three bits; A second encoder for outputting a second surplus bit by performing circular convolutional convolutional encoding on the three bits that have been sequentially substituted; And a puncturer for adjusting the code rate by selectively removing the first and second excess bits in consideration of a code rate of a preset turbo code.

Description

Apparatus and Method for Encoding using Turbo Code, and Unit and Method of Permutation

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoding apparatus and method using turbo codes, and more particularly, to an encoding apparatus and method using turbo codes and a permutation substituent and permutation substitution technique capable of improving the performance of error correction.

The present invention is derived from the research carried out as part of the high-performance satellite return link connection core technology development project of the Korea Communications Commission [Task Management No .: 2009-F-039-01, Title: Development of core technology for high efficiency satellite return link connection ].

In general, digital data may cause errors during transmission due to wired / wireless link / channel noise or other data transmission. Therefore, each communication system employs an error correction technique to correct an error occurring during transmission.

Turbo Code, one of the typical error correction techniques, is a Forward Error Correction (FEC) technique that encodes and transmits an input block using turbo codes, thereby lowering the error occurrence rate during transmission. Make corrections possible too.

The turbo code shows better performance as the minimum Hamming Distance (MHD) is larger, which is greatly affected by interleaving, or permutation. Hereinafter, the method of permutation replacement of each turbo protection will be briefly described.

First, since uniform or regular interleaving uses a rectangular matrix method, interleaving is performed well even when the error pattern weight is 2 or 3, but the decoding weight of the decoder is changed. Since this does not improve the performance of error correction by interleaving, there is a problem that is greatly affected by the error pattern of a square or a rectangular shape.

In addition, in the non-uniformity interleaving method, even when the error pattern weight is 2 or 3, the error pattern is well scattered, so that the codewords of each code can be dispersed well, the decoding weight can be increased, and the gain of substitution And it has the advantage of exponentially improving performance.

Therefore, many non-uniform interleaving schemes are applied to turbo codes. Among them, the double-binary turbo code of the RCS standard is evaluated as a powerful forward error correction technique very close to the limit of Shannon, but the error floor phenomenon occurs at a low code rate. This has been pointed out and there is a need for improvement.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide an encoding apparatus and method using a turbo code that can improve error correction capability of turbo protection by increasing the hamming distance of input data input in parallel 3 bits, and permutation substituents and permutations. In providing a substituent technique.

It is still another object of the present invention to provide an encoding apparatus and method using a turbo code and a permutation substituent and permutation substitution technique that can provide a permutation substitution technique that can increase a hamming distance of input data input in parallel three bits.

According to an embodiment of the present invention, an encoding apparatus using a turbo code may include recursive systematic convolutional codes (3 bits) input from first to third blocks each consisting of N bits to form a first surplus bit. a first encoder for outputting parity bits); A permutation substituent for permutating the three bits; A second encoder for outputting a second surplus bit by performing circular convolutional convolutional encoding on the three bits that have been sequentially substituted; And a puncturer for adjusting the code rate by selectively removing the first and second excess bits in consideration of a code rate of a preset turbo code.

According to another aspect of the present invention, a permutation convertor may include: a first exchange of bits of at least two blocks among the three blocks when a sequence of three bits received from three blocks each consisting of N bits is a multiple of two; Substituents; A second substituting unit for checking a residual value obtained by dividing the sequence numbers of the three bits interchanged by 4 and changing the sequence numbers of the three bits in the respective blocks in different ways according to the remaining values; And an ordering unit for replacing and arranging the order of the bits of the three blocks in the changed order.

According to another aspect of the present invention, an encoding method using a turbo code includes a first surplus by converting three bits respectively received from first to third blocks each consisting of N bits into recursive systematic convolutional codes. Outputting a parity bit; Permutating the 3 bits in a predetermined manner; Outputting a second surplus bit by performing circular convolutional convolutional encoding on the 3 bits which have been sequentially substituted; And when the mother code rate according to the combination of the 3 bits, the first surplus bit, and the second surplus bit is different from a predetermined code rate, selectively remove the first and second surplus bits to reduce the code rate. It characterized in that it comprises a step of adjusting.

According to another aspect of the present invention, a permutation method may include sequentially receiving each bit of the first block, the second block, and the third block, each of which is composed of N bits, and the order k of each bit (0 ≦ k ≦). A constant of N); Exchanging bits of at least two blocks of the three blocks when the order of each bit is a multiple of two; Identifying a remainder value obtained by dividing the sequence number of each bit by four, and changing the sequence number of the three bits interchanged in each block in different ways according to the remainder value; And arranging by replacing the order of the bits of the three blocks in the changed order.

According to the present invention, by applying a puncturing technique and a permutation substitution technique to the input data input in parallel 3 bits, there is an effect that can increase the minimum hamming distance by more than 50% compared to the conventional two-input turbo code. Therefore, the present invention can greatly improve the error correction performance of the transmission and reception data compared to the conventional turbo code.

1 is a block diagram showing an encoding device using a turbo code according to the present invention.
Figure 2 is a block diagram showing a permutation substituent in accordance with the present invention.
Figure 3 is a simulation graph showing the BER performance according to permutation substitution according to the present invention.
4 is a simulation graph showing the BER performance according to the puncturing according to the present invention.
5 is a flowchart illustrating a turbo encoding method according to the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms " comprises, " and / or "comprising" refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

Hereinafter, an encoding apparatus using a turbo code according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a block diagram showing an encoding device using a turbo code according to an embodiment of the present invention.

As shown in FIG. 1, the encoding apparatus 10 using a turbo code according to an exemplary embodiment of the present invention may include a first encoder 101, a permutation converter 200, a second encoder 102, and a puncturer 300. And a codeword generator 400.

The first encoder 101 converts three bits of input data (A bits, B bits, and C bits) received from the first block, the second block, and the third block into eight states (8-state) or 16 states (16), respectively. -State) The first parity bit is output by recursive systematic convolutional codes.

In this case, the first block, the second block, and the third block include N information bits in total of 3N information bits. That is, when the information bits to be encoded are 3N, the first block includes the first through Nth information bits, the second block includes the N + 1 through 2Nth information bits, and the third block contains 2N + 1. It may include the first to 3N th information bits.

The permutation converter 200 interleaves, i.e., permutates, the input data (A bits, B bits, and C bits) in each manner between and within each block. The detailed configuration of the permutation substituent 200 will be described later with reference to FIG. 2.

The second encoder 102 outputs a second surplus bit by performing 8-state or 16-state cyclically-convolutional convolutional coding of permutated input data (A bits, B bits, and C bits). do.

The puncturing unit 300 adjusts coding rates of the first block, the second block, and the third block by selectively removing the first and second redundant bits.

For example, the puncturing unit 300 may adjust the code rate by selectively removing the first and second surplus bits, respectively, when the order of each bit is odd and even. Hereinafter, the puncturing machine 300 will be described in more detail with reference to FIG. 3.

Meanwhile, the codeword generator 400 selectively receives 3 bits and a first surplus bit and a second surplus bit from the puncturing unit 300 to generate an encoded codeword.

Meanwhile, the encoding apparatus 10 using the turbo code according to an exemplary embodiment of the present invention further includes an operation unit 600 and a determination unit 500, and includes a permutation converter using the operation unit 600 and the determination unit 500. The variables used for permutation substitution of 200) can be determined.

The calculation unit 500 calculates a minimum hamming distance using candidates of permutation substitution parameters according to a predetermined code rate and a state, and the determination unit 600 performs the permutation having the largest calculated minimum hamming distance. The candidate for the substitution parameter is determined as the permutation substitution parameter of the permutation substituent 200.

Hereinafter, a permutation substituent according to an embodiment of the present invention will be described with reference to FIG. 2. 2 is a block diagram showing a permutation substituent according to an embodiment of the present invention.

As shown in FIG. 2, the permutation substituent 200 according to the embodiment of the present invention includes a first substituent 210, a second substituent 220, and an array 230.

When the order of the input data (A bits, B bits, and C bits) is a multiple of 2, the first permutation unit 210 includes bits of two or more blocks (ie, A bits, B bits) of the first to third blocks. And two or more bits of the C bits).

For example, the first substitution unit 210 may exchange bits of the first block, which is the first block, and the third block, which is the last block.

The second substituent 220 may be used in the first to third blocks in different ways according to the remaining values obtained by dividing the sequence of the A bits, the B bits, and the C bits by the first substituent 210 by four. Change the order of bits, B bits, and C bits.

The second substitution unit 220 may change the order of A, B, and C bits according to Equation 1 below. Where j is the changed order of the A, B and C bits, k is the original order of the A, B and C bits, P is the permutation parameter shown in Table 1 below, and Q is Is a result calculated by substituting the permutation substitution parameters shown in Table 1 below in Equation 2 when the remaining values are 0, 1, 2, and 3, respectively.

Here, the permutation substitution parameters may be variously set according to a predetermined code rate and a state of permutation substitution, and the second permutation unit 220 may have various permutations set as shown in Table 1 below. Among permutation parameters, a permutation substitution parameter having a relatively high minimum Hamming Distance (MHD) is used.

The listing unit 230 outputs the A 'bits, the B' bits, and the C 'bits, which are listed in the order changed by the second substitution unit 220.

On the other hand, the permutator 200 may be provided with a permutation substitution parameter from the outside, or a calculation unit for calculating the minimum hamming distance, respectively using candidates of permutation substitution parameters according to a predetermined code rate and the state ( 240, and a determination unit 250 for determining the candidate of the permutation substitution parameter having the largest calculated minimum hamming distance as the permutation substitution parameter of the second substitution unit 220.

Hereinafter, the permutation substitution pattern of the first substitution unit 210 according to the embodiment of the present invention will be described with reference to FIG. 3. FIG. 3 is a simulation graph illustrating BER performance when the first substitution unit uses permutation substitution patterns (patterns 1 to 5) as shown in Table 2 below.

From the graph of FIG. 3, it can be seen that the first substituent 210 has excellent performance when using the pattern 1, which exchanges A bits and C bits, among the permutation substitution patterns shown in Table 2 above. Therefore, in the present specification, the case where the first substitution unit 210 uses the pattern 1 is taken as an example.

Hereinafter, a puncturing pattern of the puncturing machine 300 according to an embodiment of the present invention will be described with reference to FIG. 4. FIG. 4 is a simulation graph illustrating BER performance when the puncturing machine 300 according to an embodiment of the present invention uses the puncturing patterns (case 1, case 2, and case 3) shown in Table 3 below.

In FIG. 4, the first to third blocks are composed of a total of four bits (ie, N = 4), and the bit values of each block are all '1'. Or, a case of using a double-binary turbo code of the RCS standard and puncturing at a 3/4 code rate in a 16-state turbo code having a parent code rate of 3/5 will be described as an example.

In the graph of FIG. 4, it can be understood that BER performance is best when the puncturing pattern of Case 2 is applied than when the puncturing pattern of Case 1 and the puncturing pattern of Case 3 are applied. Therefore, in the present specification, a case in which the puncturing machine 300 applies the puncturing pattern of case 2 has been described as an example.

Of course, according to the permutation of the present invention, when the puncture is not performed, the BER performance of 0 (when the mother code rate is 3/5) is better than 1, 2, and 3 when puncturing is performed. However, considering the transmission efficiency, puncturing is often required. Therefore, in the present invention, even if the code rate is adjusted, the puncturing of the pattern does not significantly decrease compared to the parent code rate.

Hereinafter, a turbo encoding method according to an exemplary embodiment of the present invention will be described with reference to FIG. 5. 5 is a flowchart illustrating a turbo encoding method according to an embodiment of the present invention.

Referring to FIG. 5, the encoding apparatus 10 using a turbo code performs cyclically convolutional coding on A bits, B bits, and C bits, and outputs a first surplus bit (S510).

Subsequently, the encoding apparatus 10 using the turbo code permutates 3 bits in a predetermined manner (S520). That is, when the order of three bits is a multiple of two, the encoding device 10 using the turbo code swaps the bits of one block and another block in the first to third blocks with each other, and divides the order of the three bits by four. According to the value, the order of each interchanged bit in the block including each interchanged bit is replaced in the above-described manner.

Subsequently, the encoding apparatus 10 using the turbo code performs cyclically-convolutional convolutional coding on the permutated 3 bits to output the second surplus bits (S530).

Thereafter, the encoding apparatus 10 using the turbo code determines whether the mother code rate according to the combination of the 3 bits, the first surplus bits, and the second surplus bits is equal to the preset code rate (S540).

If the mother code rate according to the combination of the surplus bits is equal to the preset code rate, the encoding apparatus 10 using the turbo code turbo-encodes 3 bits, the first surplus bits, and the second surplus bits (S560).

On the other hand, if the mother code rate is different from the preset code rate, the encoding apparatus 10 using the turbo code selectively adjusts the code rate by selectively removing the first and second surplus bits through puncturing (S550).

As described above, according to the present invention, the puncturing technique and the permutation substitution technique are applied to input data input in parallel 3 bits, and the minimum Hamming distance can be increased by 50% or more compared to the conventional two-input turbo code by using the turbo code. have. Therefore, the present invention can greatly improve the error correction performance of the transmission / reception data compared with the conventional turbo code.

While the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that various modifications, Of course, this is possible. Accordingly, the scope of protection of the present invention should not be limited to the above-described embodiments, but should be determined by the description of the following claims.

Claims (20)

A first encoder for outputting a first parity bit by converting three bits respectively received from the first to third blocks each having N bits into recursive systematic convolutional codes;
A permutation substituent for permutating the three bits;
A second encoder for outputting a second surplus bit by performing circular convolutional convolutional encoding on the three bits that have been sequentially substituted; And
A puncturing device for adjusting the code rate by selectively removing the first and second surplus bits in consideration of a code rate of a preset turbo code
Including;
The permutation substituent,
If the order of the three bits is a multiple of two, among the first to third blocks, the bits of the first block and the last block are interchanged with each other, and according to the remaining value obtained by dividing the order of the three bits by four, To replace the order of each bit replaced in the block containing the respective bit,
The puncturing machine,
And encoding the code rate by selectively removing the first and second redundant bits when the order of the three bits is odd and even. delete The method of claim 1,
An arithmetic unit configured to calculate a minimum hamming distance using candidates of permutation substitution parameters according to a predetermined code rate and a state; And
A determination unit for determining a candidate of the permutation substitution parameter having the largest calculated minimum hamming distance as a permutation substitution parameter of the permutation substituent
Encoder using a turbo code further comprising. The method of claim 3, wherein the permutation substituent,
Coding apparatus using a turbo code that replaces the order of each of the interchanged bits by using the equation j = (P * k + Q + 3) mod N for providing a different result value according to the remaining value ( K is a sequence of the 3 bits, P is the permutation substitution parameter, and Q is a constant determined by the permutation substitution parameter and the remainder value. delete The method of claim 1, wherein the puncturer,
And if the sequence number is odd, removes the first excess bit, and if the sequence number is even, removes the second excess bit. The method of claim 1,
A codeword generator for generating an encoded codeword by selectively receiving the 3 bits and the first surplus bit and the second surplus bit from the puncturing unit.
Encoder using a turbo code further comprising. delete delete delete delete Outputting a first parity bit by converting three bits respectively received from the first to third blocks each consisting of N bits into recursive systematic convolutional codes;
Permutating the 3 bits in a predetermined manner;
Outputting a second surplus bit by performing circular convolutional convolutional encoding on the 3 bits which have been sequentially substituted; And
If the mother code rate according to the combination of the 3 bits, the first surplus bit and the second surplus bit is different from a predetermined code rate, the code rate is adjusted by selectively removing the first surplus bit and the second surplus bit. Steps to
Including;
The permutation step is,
If the order of the three bits is a multiple of two, swapping bits of a first block and a last block among the first to third blocks; And
Substituting the order of each bit in a block containing each bit that is interchanged according to the remaining value of the 3-bit order divided by 4.
Including;
Wherein the adjusting comprises:
Selectively removing the first redundant bit and the second redundant bit when the order of the three bits is odd and even
Encoding method using a turbo code comprising a. delete delete delete delete delete delete delete delete

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