KR20100096850A - Method and device for puncturing, descrambling method thereof - Google Patents

Abstract

PURPOSE: A puncturing method, a puncturing device thereof, and a decoding method in a puncturing process are provided to increase an error detection performance by connecting a CRC code to control information to be transmitted. CONSTITUTION: A generator(210) generates cordwords which is convoluted by connecting a CRC code to control information with k bits. A first calculation unit(220) looks for a minimum free distance and a hamming weight of generated codewords. A second calculator(230) calculates the number of the punctured bits. A code unit(240) obtains the combination and progression of the codewords. A puncturing unit(250) punctures the position of the minimum element among the elements of the progression. An exclusion unit(260) excludes an adjacent position from a puncturing candidate not to puncture the adjacent position.

Description

Method and device for puncturing, descrambling method

The present invention relates to a punching method and apparatus therefor, and a decoding method in punching. In particular, the present invention provides a puncturing method and apparatus and control at the time of transmitting a PLCP (Physical Layer Convergence Procedure) control information in a wireless LAN (WLAN) standard IEEE (Institute of Electrical and Electronics Engineers) 802.11p physical layer A method of decoding information.

The present invention is derived from the research conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Promotion. [Task management number: 2007-F-039-02, Task name: VMC technology development].

In many communication protocols, it is common to transmit control information of short length before transmitting a large amount of information.

The WLAN standard IEEE 802.11p physical layer transmits a PLCP header part of control information before sending a large amount of information. In general, a convolutional code is used to transmit a short length of information, and the PLCP header is also transmitted using a convolutional code. At this time, if the PLCP header part fails to be transmitted, it is important to transmit this control information correctly because the PLCP header part is retransmitted or distortion occurs in a large amount of information received after the PLCP header.

Decoding of convolutional codes is achieved by the optimal lattice path generation method. Since the optimal path obtained at this time is always a valid codeword, the optimal grid path generation decoding method does not provide an error detection capability. To compensate for this, algorithms that add error detection capability to convolutional codes are well known.

The receiver generates the received information as the most likely path, decodes it into a codeword, and performs an error check to determine whether or not it is a suitable codeword. If an error occurs, recreate it with the next most likely path, and try this method a certain number of times. If an error is determined even in the last time, the decoding is determined to be a failure.

The receiver also uses a Cyclic-Redundancy Check (hereinafter referred to as "CRC") code for error detection. The CRC code is a code for error detection. The CRC code is used as the additional information by adding the remainder divided by the generator polymomial of the CRC code. The information thus made is transmitted through the channel, and CRC code check is performed on the received information to determine whether an error occurs in the transmitted information. It is generally well known that the error detection capability is improved as the length of the CRC code increases. On the other hand, as the CRC code becomes longer, the code rate decreases and the length of the transmitted code becomes longer.

The technical problem to be achieved by the present invention is to add a CRC code in the puncturing method and apparatus, and the puncturing method to maintain a constant code rate and length of the code, and to minimize the loss of error correction capability of the convolutional code is degraded due to puncturing Is to provide a decoding method.

Method of puncturing the control information received from the puncturing apparatus prior to receiving the information according to the characteristics of the present invention for achieving the above object

Generating convolutional coded codewords by concatenating a cyclic redundancy check (CRC) code to the control information having a specific bit, calculating a hamming weight of the generated codewords, and finding a minimum free distance; Obtaining a set of codewords based on the above, obtaining a sequence based on the set, and finding the smallest element among the elements included in the sequence, and drilling the position of the smallest element.

The apparatus for puncturing the control information received from the puncturing apparatus prior to receiving the information according to another feature of the present invention is

A generation unit for generating convolutional codewords by concatenating a Cyclic-Redundancy Check (CRC) code to the control information having a specific bit, a first calculator for calculating a Hamming weight of the generated codewords to find a minimum free distance; A coder for obtaining a set of codewords based on the minimum free distance, a coder for obtaining a sequence based on the set, and a puncturer for drilling the position of the smallest element by finding the smallest element among the elements included in the sequence Include.

In addition, when the control information is punctured on the basis of convolutional codewords by concatenating a cyclic-redundancy check (CRC) code to control information received from the puncturing device before receiving the information according to another feature of the present invention, the control How to decrypt the information

Generating and decoding the control information using a first grid path; determining whether an error has occurred based on a CRC code check after generating and decoding the first grid path; and when the error occurs, Generating and decoding a second lattice path, determining whether an error has occurred based on a CRC code check after generating and decoding the second lattice path, and receiving the retransmission of the control information when the error occurs. Steps.

According to an embodiment of the present invention, the CRC code is concatenated with information to be transmitted, thereby increasing error detection capability, fixing code rate using puncturing, and minimizing loss of error correction capability.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “… module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. Can be.

Hereinafter, a drilling method, an apparatus thereof, and a decoding method when drilling according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a frame structure of a packet protocol data unit of a physical layer according to an embodiment of the present invention.

Referring to FIG. 1, a frame of a packet protocol data unit (hereinafter referred to as a "PPDU") is a preamble unit 110 called a physical layer convergence procedure (hereinafter referred to as "PLCP"). ), A signal unit SIGNAL 120 and a data unit DATA 130.

The PLCP preamble unit 110 includes 12 orthogonal frequency division multiplexing (OFDM) symbols, and the signal unit 120 includes one symbol as shown in the PLCP header 140.

The PLCP header 140 includes a plurality of bits coded in a half rate binary phase shift scheme (BPSK), that is, a rate field (RATE) 141, a reserved bit 142, and a length bit (LENGTH bit). ) 143, a parity bit unit 144, a tail bit unit 145, and a service bit unit 146. In addition, the data unit 130 includes a protocol service data unit (PHY Service Data Unit, hereinafter "PSDU") field including actual payload data, a tail part, and a pad bit part. .

According to an embodiment of the present invention, the rate field 141 and the length bit 143 in the PLCP header 140 are important information, which is used as information of short length. In addition, one bit of the parity bit unit 144 is used for error detection when information is transmitted, and the signal unit 120 generates a total of 2 ¹⁶ codewords.

Hereinafter, it is assumed that one bit of the reserve bit 142 and one bit of the parity bit unit 144 may be used as the CRC code in the signal unit 120.

According to the puncturing method according to an embodiment of the present invention, the assumed CRC code is concatenated and transmitted to the control information.

Next, the structure of the drilling device 200 will be described in detail with reference to FIG. 2.

2 is a block diagram showing the structure of a perforation device according to an embodiment of the present invention.

Referring to FIG. 2, the drilling apparatus 200 may include a generation unit 210, a first calculation unit 220, a second calculation unit 230, a sign unit 240, a perforation unit 250, and an exclusion unit 260. ).

Next, a drilling method according to an embodiment of the present invention will be described in detail with reference to FIG.

3 is a flowchart illustrating a drilling method according to an embodiment of the present invention.

비트)(codeword)들을 생성한다(S301). The received large amount of information has a short length of control information to be sent before sending the information, which is input to the punching device 200, as shown in Figure 3, the generating unit 210 of the punching device 200 ) Is a codeword convolutionally coded by concatenating a CRC code to control information having a short length, that is, k bits.

Codewords are generated (S301).

The punching device 200 according to the embodiment of the present invention uses the CRC code as a code for error detection. In this case, the error detection capability is generally improved as the length of the CRC code is increased. However, as the length of the CRC code increases, the code rate decreases and the length of the codeword to be transmitted increases. In order to solve this disadvantage, the punching device 200 punches in a manner of increasing the code rate.

)를 찾는다(S302). 또한, 천공에 의해 감소된 최소 자유거리는

이다. The first calculator 220 calculates a hamming weight of the generated codewords, and calculates a minimum free distance:

(S302). Also, the minimum free distance reduced by perforation

to be.

을 최대화 한다. 여기서, 천공 방법은 천공에 의해 발생하는

을 최대화할 수 있는 방법 중 하나를 제안하는 것이다. Since puncturing reduces the number of bits of the codeword to be transmitted, and the minimum free distance after puncturing is smaller than the minimum free distance of the parent code, the performance after puncturing is generally not as good as that of the parent code. That is, in order to minimize the loss of error correction capability according to an embodiment of the present invention is generated by the puncture

Maximize. Here, the drilling method is generated by the drilling

One way to maximize this is to suggest.

)를 계산한다(S303). 여기서, 천공해야 하는 비트의 수(

)는 수학식 1과 같이 나타낼 수 있다. The second calculator 230 may determine the number of bits to be punctured (

) Is calculated (S303). Where the number of bits to be drilled (

) May be expressed as in Equation 1.

)와 CRC 부호를 연접하지 않은 부호어의 길이(n)의 차이만큼 천공을 한다. Specifically, in order to constantly transmit the code rate, the second calculator 230 concatenates the CRC code and then encodes the length of the coded codeword (

) Is punctured by the difference of the length (n) of the codewords not concatenated with the CRC code.

)을 구한다(S304, S305). The coder 240 is a set of codewords S and a sequence (

) Is obtained (S304, S305).

)에서부터 최소 자유거리와 천공해야 하는 비트의 수를 더한값(

) 사이의 해밍무게를 가지는 모든 부호어들의 집합(S)을 구한다. 여기서 해밍무게는 부호어 내에서 영(0)이 아닌 성분(비트)의 개수이다.Specifically, the sign 240 is the minimum free distance (

) Plus the minimum free distance plus the number of bits to drill (

Get a set S of all codewords with Hamming weight between Here, the Hamming weight is the number of nonzero components (bits) in the codeword.

The set S according to the embodiment of the present invention may be represented by Equation 2.

은 집합(S)의 원소 개수이다. here,

Is the number of elements in the set (S).

)을 구한다. 여기서, 수열(

)은 수학식 3과 같이 나타낼 수 있다. In addition, the coder 240 may add a number of 1s to each bit position of all codewords in the set S.

) Where a sequence (

) Can be expressed as in Equation 3.

)의 원소(

) 중 가장 작은 원소(

)를 찾아 그 위치(

)를 천공한다(S306). 이때, 가장 작은 원소(

) 즉, 천공할 대상인 천공후보들이 복수개 존재하는 경우, 최소 자유거리(

)인 부호어들을 수집하여 수열(

)과 같은 수열'(

)을 생성한다. 다음, 천공후보들을 수열'(

)에서 재비교하여 가장 작은 원소를 찾아 선택하고, 그 중에서도 같은 값이 존재하는 경우 임의로 하나를 선택하여 그 위치를 천공한다. Perforation 250 is a sequence (

Element of

Smallest element ()

) And its location (

Puncture) (S306). Where the smallest element (

In other words, when there are a plurality of candidates for drilling, the minimum free distance (

) To collect a sequence of codewords

A sequence such as) "(

). Next, drill candidates' (

) To find and select the smallest element, and, if the same value exists, select one at random and puncture the position.

)를 천공한 후, 제외부(260)는 인접한 위치는 천공을 하지 않기 위해서 (

)는 천공후보에서 제외한다(S307).location(

After puncturing, the exclusion unit 260 does not puncture adjacent positions (

) Is excluded from the puncture candidate (S307).

)를 모두 천공하였는지 판단한다 (S308). 천공해야 하는 비트의 수(

)가 남아 있는 경우, 천공부(250)는 천공해야 하는 비트의 수(

)를 모두 천공할 때까지, 수열(

)의 원소(

) 중 가장 작은 원소(

)를 찾아 그 위치(

)를 천공한다.Next, the puncturing part 250 may determine the number of bits to be punctured (

It is determined whether all perforations) (S308). The number of bits that need to be drilled (

), The puncturing part 250 may determine the number of bits to be punctured (

) Until all the holes are drilled,

Element of

Smallest element ()

) And its location (

Perforate).

Hereinafter, assuming that 1 bit of the reserve bit 142 and 1 bit of the parity bit unit 144 can be used as a CRC code, a puncturing method according to an embodiment of the present invention has a length of 4 for control information having 16 bits. An example of concatenating and puncturing a CRC code is described.

First, ① generating unit 210 generates 2 ¹⁶ codewords convolutionally coded by concatenating CRC codes with control information having 4 bits.

)를 구한다. 이때, 최소 자유거리(

)는 12이다. ② The first calculation unit 220 calculates the Hamming weight of each of the 2 ¹⁶ codewords to determine the minimum free distance (

) Where the minimum free distance (

) Is 12.

)를 구한다:

= 4③ The second calculation unit 230 is the number of bits to be drilled (

Find:

= 4

)을 구한다④ The coder 240 is a set (S) and a sequence of codewords (

Find)

:

)의 원소 중 가장 작은 원소(

)를 찾아 그 위치(

)를 천공한다⑤ The perforation 250 is a sequence (

Is the smallest element of)

) And its location (

Perforate)

를 천공한다: 1, 2, 51, 52 중 2를 선택: first

Punch: Choose 2 from 1, 2, 51, 52

)는 천공후보에서 제외한다.⑥ exclusion unit 260 is adjacent to the position not to puncture (

) Are excluded from drilling candidates.

)는 천공후보에서 제외하고, 다음

을 찾는다: 51, 52 중 51을 선택: (

), Except for the puncture candidate

Look for: 51, 52 Choose 51

)가 남아 있는 경우, 세 번째, 네 번째

: (49, 4)를 천공한다. ⑦ Number of bits to drill

), The third and fourth

: Drill (49, 4).

Next, a method of decoding the convolutional code during drilling according to an embodiment of the present invention will be described in detail with reference to FIG. 4.

4 is a flowchart illustrating a decoding method when puncturing according to an embodiment of the present invention.

비트)(codeword)들을 생성한다. First, the generation unit 210 of the punching device 200 concatenates and encodes a CRC code to control information having a short length, that is, k bits,

Generate codewords.

Referring to FIG. 4, in the convolutional code decoding method according to an embodiment of the present invention, the generation unit 210 generates and decodes the received control information as the first most likely lattice path (S401).

After decoding the received control information, the generation unit 210 determines whether an error has occurred through the CRC code check (S402).

If an error occurs as a result of the determination, the generation unit 210 generates and decodes the received control information as the second grid path (S403).

After generating and decoding the received control information as the second grid path, the generation unit 210 determines whether an error has occurred through the CRC code check (S404).

비트)를 사용한다. 또한, 생성부(210)는 CRC부호 검사를 한 후 발생할 수 있는 복호 오류가 발생하였는지 판단한다(S405, S407). 복호 오류가 발생한 것으로 판단되면, 생성부(210)는 에러가 발생한 것으로 판단한다(S406, S408). 반면에, 생성부(210)는 복호 오류가 아니라고 판단되면, 성공한 것으로 인정한다(S409).The generation unit 210 decodes the codeword when it is determined that the CRC code check result of the step S402 and step S404 is not an error (

Bit). In addition, the generation unit 210 determines whether a decoding error that may occur after the CRC code check occurs (S405 and S407). If it is determined that a decoding error has occurred, the generation unit 210 determines that an error has occurred (S406 and S408). On the other hand, if it is determined that the generation unit 210 is not a decoding error, it is recognized as successful (S409).

Next, if it is determined that the error of the two CRC code check results, the generation unit 210 recognizes that the failure and requests the sender to retransmit the control information (S410).

In the puncturing method according to an embodiment of the present invention, a frame error rate (hereinafter referred to as "FER") is used to compare the performance according to the CRC code. Here, FER may be represented as in Equation 4.

은 S406 단계에서 발생한 에러율이며,

은 S408 단계에서 발생한 에러율이고,

은 S410단계에서 발생한 오류율이다. here,

Is the error rate generated in step S406,

Is the error rate occurred in step S408,

Is the error rate generated in step S410.

Next, the performance according to the drilling method according to an embodiment of the present invention will be described in detail with reference to FIGS.

5 is a view showing the performance according to the drilling method according to an embodiment of the present invention, Figure 6 is a view showing the FER performance for the length of the CRC code according to the drilling method according to an embodiment of the present invention.

First, it is assumed that the number of CRC codes is four according to the puncturing method according to the embodiment of the present invention.

Referring to FIG. 5, a result when the number of CRC codes is 4 and a result when the number of CRC codes is 4 according to a method other than the method according to the embodiment of the present invention are shown.

의 성능을 나타내는 지점(A)에서 본 발명의 실시예에 따른 천공 방법이 임의로 천공한(Random 1,2,3)보다 0.25dB가량 개선되었다. Random is the result of experimenting with FER performance after randomly selecting 4 punching positions. Experimental results show that FER

In the point (A) showing the performance of the puncturing method according to an embodiment of the present invention was improved by about 0.25dB than the random puncture (Random 1,2,3).

In FIG. 6, FER performance is compared when E _b / N ₀ (dB) is 2 dB and 3 dB according to the number of concatenated CRC codes.

Referring to FIG. 6, when the number of concatenated CRC codes is 4, the best FER performance is shown.

As described above, the puncturing method, the puncturing decoding method, and the apparatus according to the embodiment of the present invention can minimize the loss of error correction capability.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram illustrating a frame structure of a packet protocol data unit of a physical layer according to an embodiment of the present invention.

2 is a block diagram showing the structure of a perforation device according to an embodiment of the present invention.

3 is a flowchart illustrating a drilling method according to an embodiment of the present invention.

4 is a flowchart illustrating a decoding method when puncturing according to an embodiment of the present invention.

5 is a view showing the performance according to the drilling method according to an embodiment of the present invention.

6 is a view showing the FER performance for the length of the CRC code according to the drilling method according to an embodiment of the present invention.

Claims (14)

In the method for puncturing the control information received from the puncturing device before receiving the information, Generating convolutional codewords by concatenating a cyclic redundancy check (CRC) code to the control information having a specific bit; Calculating the Hamming weight of the generated codewords to find the minimum free distance; Obtaining a set of codewords based on the minimum free distance, and obtaining a sequence based on the set, and Finding the smallest element among the elements included in the sequence and drilling the position of the smallest element Perforation method comprising a. The method of claim 1, Puncturing the position of the smallest element Calculating the number of bits to be drilled, After puncturing the smallest element, the adjacent position of the smallest element is a first element, which is an element that exists in front of the smallest element so as not to puncture, and a second element which is after the smallest element. Removing the element from the puncture candidate, and Determining whether the number of bits has been punctured Perforation method comprising more. The method of claim 2, Determining whether the number of bits is all punctured If the number of bits to be punctured remains, finding the smallest element of the elements of the sequence until the number of bits to be punctured is all drilled, and drilling the position of the smallest element. Perforation method comprising a. The method of claim 2, Calculating the number of bits Calculating a difference between a length of an encoded codeword after concatenating the CRC code and a length of a codeword not concatenating the CRC code. Perforation method comprising a. The method of claim 1, Obtaining a sequence based on the set Obtaining a set of codewords having the Hamming weight between the minimum free distance plus the minimum free distance plus the number of bits to be punctured, and Obtaining the sequence by adding a specific number for each bit position of the code words in the set; Perforation method comprising a. In the device for puncturing the control information received from the puncturing device prior to receiving the information, A generation unit for generating convolutional codewords by concatenating a cyclic redundancy check (CRC) code to the control information having a specific bit; A first calculation unit calculating a hamming weight of the generated codewords and finding a minimum free distance; A code part which obtains a set of code words based on the minimum free distance, and obtains a sequence based on the set, and Perforation unit for finding the smallest element among the elements contained in the sequence, and punctures the position of the smallest element Perforation device comprising a. The method of claim 6, A second calculator for calculating the number of bits to be punched Perforation device further comprising. The method of claim 7, wherein The second calculation unit And a concatenation device for calculating the number of bits based on a difference between a length of an encoded codeword after concatenating the CRC code and a length of a codeword not concatenating the CRC code. The method of claim 6, The code part Obtaining a set of codewords having the Hamming weight between the minimum free distance and the minimum free distance plus the number of bits to be punctured, and adding the sequence by adding a specific number for each bit position of the codewords in the set. Obtain the perforation device. The method of claim 6, After puncturing the position of the smallest element, the adjacent position of the smallest element is a first element, which is an element existing in front of the smallest element so as not to puncture, and an element located behind the smallest element. Exclusion to exclude second element from drilling candidate Perforation device further comprising. In the case of puncturing control information based on codewords concatenated by concatenating a cyclic-redundancy check (CRC) code to control information received from a puncturing device prior to receiving the information, the method of decoding the control information, Generating and decoding the control information as a first grid path; Determining whether an error has occurred based on CRC code check after generating and decoding the first grid path; When the error occurs, generating and decoding the control information as a second grid path; Determining whether an error has occurred based on a CRC code check after generating and decoding the second lattice path; and Resending the control information when the error occurs Decoding method when puncturing comprising a. The method of claim 11, Determining whether the error has occurred If the error does not occur, determining whether a decoding error that may occur after the CRC code check has occurred; and Determining that an error occurs in the decoding apparatus when the decoding error occurs Decoding method when puncturing comprising a. The method of claim 12, And a frame error rate is used to compare the performance according to the CRC code based on the error rate at which the decoding device has an error. The method of claim 12, Determining that the decoding of the control information is successful when the decoding error does not occur Decoding method when puncturing comprising a.

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