KR100282070B1 - A method of encoding and decoding error detecting codes using convolutional codes - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a convolutional encoding and decoding method of an error detection code.

2. The technical problem to be solved by the invention

The present invention performs a cyclic redundancy check (CRC) of a convolutional coded error detection code to determine whether there is an error before completely decoding all convolutional coded cyclic redundancy check (CRC) bits. The convolutional encoding and decoding method of the error detection code, which can be transmitted quickly and skips the process of adding tail bits to the end of the error detection codeword in the convolutional encoding process, improves transmission efficiency by reducing overhead. The purpose is to provide.

3. Summary of Solution to Invention

The present invention includes a first step of convolutionally encoding and transmitting an error detection codeword without addition of tail bits; Determining whether an error is detected by using a register value of the convolutional decoder while decoding the convolutional coded error detection code; And a third step of transmitting the decrypted message up to the point in time at which it is determined whether or not an error is detected.

4. Important uses of the invention

The present invention is used for a convolutional encoder and a convolutional decoder.

Description

Convolutional coding and decoding method of error detection code {A METHOD OF ENCODING AND DECODING ERROR DETECTING CODES USING CONVOLUTIONAL CODES}

The present invention relates to a convolutional encoding and decoding method of an error detection code, and more particularly, to a convolutional encoding and decoding method of an error detection code capable of performing error correction and error detection by convolutionally encoding and decoding an error detection code.

FIG. 1 is a diagram illustrating a configuration of a general convolutional encoder, and FIG. 2 is an explanatory diagram of a method of convolutional coding a codeword of a conventional error detection code. A conventional convolutional encoding and decoding method will now be described with reference to FIGS. 1 and 2.

In general, when convolutionally encoding a codeword of an error detection code, a convolution of a convolutional code called tail bits at the end of the error detection coded codeword (or an error detection codeword divided when the convolutional encoder divides a message). A method of adding a number '0' smaller than the constraint length and convolutional coding the error detection coded codeword and tail bits together is used.

In decoding the convolutional coded codeword as described above, when the survival path is continuously obtained according to time, and the decoding depth is Γ, the survival path at that time at time t ( outputs a decoded bit or bit block corresponding to a (t-Γ) time point corresponding to a survival path, and decodes the error detection codeword by performing the decoding as much as the length of the error detection codeword through this process. The error detection codeword was used to determine an error by performing a cyclic redundancy check (CRC).

Referring to the conventional coding method as described above as follows.

Generate message 110101 If the polynomial of the generator polynomial detects and encodes a CRC code using CRC-4 with g (x) = x ⁴ + x ³ + x ² + x + 1, then codeword 1101011010 is encoded. Get If the codeword is to be encoded by a convolutional encoder having an impulse response of g ⁽¹⁰⁾ = (111) and g ⁽¹⁾ = (101) as shown in Fig. 1, the constraint length of this convolutional code Two '0's, one less than length, are added as tail bits to pass 110101101000 to the convolutional encoder. At this time, as the output of the convolutional encoder, (11,01,01,00,10,00,01,01,00,10,11,00) is obtained. 2 illustrates a process of convolutionally encoding the error detection codeword 1101011010.

Next, as an example of convolutional decryption, a hard decision decoding method will be described for convenience of description.

An error occurs in the 4th and 15th bits of the convolutional codeword (11,01,01,00,10,00,01,01,00,10,11,00) convolutionally coded above (11,00,01, A process of decoding 00,10,00,01,11,00,10,11,00 is illustrated in FIG. 3 using a trellis diagram.

First, it is assumed that the reception is started by the decoder from time 0 (t = 0), the time received by 2 bits is set as the unit time, and the decoding depth is set to 4 (Γ = 4). ). At time k (t = k), the value of time point (k-4) above the survival path calculated up to this point is output. In this way, the decoded codeword 1101011010 is obtained. When the CRC is performed on the decoded error detection codeword, it can be seen that there is no error. Thus, (110101) except the CRC bit can be obtained as the decoded message. In FIG. 3, a value in a dotted rectangle is a partial path metric value, and a portion in which a survival path is represented by a dotted line instead of a solid line has two paths having the same partial path metric value. There are more than one, indicating that one of them was chosen at random.

In the conventional method as described above, although the cyclic redundancy check (CRC) portion of the error detection code does not include the user information, but is merely used to confirm the presence or absence of an error of the user information, By treating the information and the cyclic margin check (CRC) bits identically, the cyclic margin check (CRC) bits are completely decoded by the same method as the user information, and then the cyclic margin check (CRC) is performed. The transmission of the transmission message was delayed due to a long time, and tail bits were added when the convolutional encoding was performed, resulting in a decrease in transmission efficiency due to a large overhead.

In order to solve the above problems, the present invention provides a decoding rate by performing a cyclic margin check (CRC) of a convolutional coded error detection code before completely decoding all the convolutional coded cyclic margin check (CRC) bits. The present invention provides a convolutional encoding and decoding method of an error detection code capable of quickly transmitting a transmission message.

In addition, another object of the present invention, by omitting the transmission of the tail bits at the end of the error detection codeword in the convolutional coding process, convolutional coding of the error detection code to improve the transmission efficiency by reducing overhead And a decoding method.

1 is an exemplary configuration diagram of a general convolutional encoder.

2 is an explanatory diagram of a method of convolutionally coding a codeword of a conventional error detection code.

3 is an explanatory diagram of a method of decoding a convolutional coded error detection code according to the present invention;

4 is an explanatory diagram of register contents of a convolutional code decoder to which the present invention is applied;

5 is a flowchart of a convolutional coding method according to the present invention;

6 is a flowchart of a convolutional decoding method according to the present invention;

In the convolutional encoding and decoding method of the present invention for achieving the above object, in the convolutional encoding and decoding method applied to the convolutional encoder and decoder, convolutional encoding of the error detection codeword without addition of tail bits is transmitted. First step; Determining whether an error is detected by using a register value of the convolutional decoder while decoding the convolutional coded error detection code; And a third step of transmitting the decoded message up to a point in time at which it is determined whether or not an error is detected.

Meanwhile, the convolutional decoding method of the present invention includes a convolutional decoding method applied to a convolutional decoder, comprising: a first step of determining whether a length m of a cyclic margin check bit is greater than or equal to a decoding depth Γ when a convolutional codeword is received; As a result of the determination in the first step, when the length m of the cyclic margin check bit is greater than or equal to the decoding depth Γ, the convolutional decoder outputs up to (n + m) -Γ bits, and outputs (n + m) A second step of performing a cyclic margin check by adding the Γ bits and the Γ bits in each state register of the convolutional decoder; As a result of the determination of the first step, when the length m of the cyclic margin check bit is smaller than the decoding depth Γ, the convolutional decoder outputs up to n bits, and outputs the n bits and the status registers of the length three decoders. a third step of performing a cyclic filter test by adding m bits; And after performing the cyclic margin check, determine whether there is any state in which no error is detected, and if there is any state in which no error is detected, determine that the first n bits output from the convolutional decoder are transmitted as an error-free message. And a fourth step of determining that no message error has been detected if none of the conditions have not been detected.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

3 is an explanatory diagram of a method of decoding a convolutional coded error detection code according to the present invention, and shows an example of decoding according to the present invention by using a trellis diagram.

In one embodiment of the present invention, a hard decision decoder having a decoding depth of 4 is used as an encoder as in the example described in the conventional method. I will use it. 3 is a diagram used to explain an example of a conventional decoding method, but the present invention operates in the same manner as the conventional method until the time t = 10.

4 is an explanatory diagram of register contents of a convolutional code decoder to which the present invention is applied.

As shown in the figure, the output decoded until time t = 10 is 11010, in which 0000,0001,1010,1111 are stored in registers corresponding to states S ₀ , S ₁ , S ₂ , and S ₃ , respectively.

In the conventional method of completely decoding even convolutional coded cyclic redundancy check (CRC) bits, the register value at time t = 10 has no meaning. In the present invention, however, the cyclic redundancy check (CRC) bit is used for error detection. Therefore, the error detection is performed by using the contents of the register, since it is not necessary to completely decode the signal.

At this time, the method of using the value of the register is as follows.

Assuming that decoding is performed until time t = 14, when a survival path corresponding to state S ₀ when time t = 10 is selected, a cyclic redundancy check (CRC) value to be decoded is time t. The cyclic redundancy check (CRC) value to be decoded when the survival path corresponding to the state S ₁ when the state S ₀ when = ₀ and the time t = 10 is selected is time t = 10. When the surviving path corresponding to the state S ₂ at the state S ₁ is 0001 and the time t = 10 is selected, the cyclic redundancy check (CRC) value to be decoded is the time at the time t = 10. When the survival path corresponding to the state S ₃ at the state S ₂ is 1010 and the time t = 10 is selected, the cyclic redundancy check (CRC) value to be decoded is the state S at the time t = 10. The register value of ₃ is 1111.

Therefore, it can be seen that the cyclic redundancy check (CRC) output decoded when decrypted to the survival path corresponding to each state at time t = 10 is the same as the contents of the register of each state at time t = 10. Can be.

Therefore, instead of waiting for decoding until time t = 14, error detection may be performed by using a cyclic redundancy check (CRC) value included in the output and register until time t = 10. In this case, if the error detection is performed by a method such as syndrome calculation in each state, it can be seen that there is no error when decoding along the survival path when the state S ₂ at the time t = 10. In this case, the decoded output 11010 may be obtained as a decoded message. In other words, if at least one of the four states is not detected, the decoded message can be sent. (In this case, since the systematic code is used as the error detection code, the error is determined. This is a case where the transmission message can be known, even if an error detection code for which the transmission message is unknown at the time of error detection is used, the time for determining whether the error is detected is shortened.)

As described above, the decoder can perform error detection at time t = 10 and decode the transmitted message. Therefore, when the convolutional encoder transmits a signal only by convolutionally encoding only the error detection codeword 1101011010 and transmitting only (11,01,01,00,10,00,01,01,00,10), the decoder Message 110101 may be decrypted. That is, it is not necessary to add tail bits in the convolutional encoding process, thereby reducing the number of signals to be transmitted, thereby increasing transmission efficiency.

The contents of the present invention as described above will be described in detail with reference to the flowcharts of FIGS. 5 and 6.

5 is a flowchart of a convolutional coding method according to the present invention.

First, when n-bit (n is a natural number) message to be transmitted is prepared (51), m-bit (m is a natural number) cyclic redundancy check (CRC) bit is added to the n-bit message (52) and summed (n). + m) After generating a bit error detection codeword (53), the generated error detection codeword is convolutionally coded and transmitted (54).

In this case, the convolutional encoding of the error detection codeword is directly performed without attaching tail bits of one bit smaller than the constraint length of the convolutional code added to the error detection codeword in the conventional convolutional coding method. As a result, the transmission efficiency can be increased.

6 is a flowchart of a convolutional decoding method according to the present invention.

First, upon receiving the convolutional codeword (61), it is determined whether the length m of the cyclic redundancy check (CRC) bit is greater than or equal to the decoding depth Γ (62), and the length m of the cyclic redundancy check bit is the decoding depth Γ. If greater than or equal, the convolutional code decoder outputs up to (n + m) -Γ bits (63), and outputs (n + m) -Γ bits of the output and the Γ bits in each status register of the decoder. A cyclic margin check (CRC) is performed by adding the cyclic margin check (CRC) bit portions (? Bit at the end of the m bit cyclic margin check bits) (64). In this case, a cyclic margin check is performed to determine whether there is any state in which no error is detected (65). If there is any state in which no error is detected, the first n bits output from the decoder are judged as an error-free message and transmitted. If there is no state in which no error is detected (66), it is determined that a message error is detected (67).

On the other hand, if the length m of the cyclic redundancy check bit is smaller than the decoding depth Γ, the decoder outputs up to n bits (68), and outputs the last m bits of the output n bits and the Γ bits in each state register of the decoder. Cyclic cyclic check (CRC) (69) (or the first output n + m-Γ bits and the Γ bits in the register may be combined to perform a cyclic margin check (CRC)). In this case, a cyclic margin check is performed to determine whether there is any state in which no error is detected (65). If there is any state in which no error is detected, the first n bits output from the decoder are judged as an error-free message and transmitted. If there is no state in which no error is detected (66), it is determined that a message error is detected (67).

By performing the decoding as described above, the decoding can be performed earlier by the decoding depth Γ time (when m <Γ by the length m of the cyclic redundancy check bit) compared with the conventional method.

As described above, the present invention has been described with the hard decision decoding as a decoder for convenience of explanation. However, the present invention can be extended to soft decision decoding in addition to hard decision decoding. .

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention improves the decoding speed by performing a cyclic redundancy check (CRC) of the convolutional coded error detection code before completely decoding all the convolutional coded cyclic redundancy check (CRC) bits. In this case, the transmission message can be transmitted quickly and the transmission process is omitted by adding tail bits to the end of the error detection codeword in the convolutional encoding process, thereby reducing overhead and improving transmission efficiency.

Claims (5)

In a convolutional coding and decoding method applied to a convolutional encoder and decoder, A first step of convolutionally encoding and transmitting the error detection codeword without addition of tail bits; Determining whether an error is detected by using a register value of the convolutional decoder while decoding the convolutional coded error detection code; And A third step of delivering the decrypted message until the time at which the error is detected Convolutional encoding and decoding method comprising a. The method of claim 1, Determining whether an error is detected using a register value of the convolutional decoder, The convolutional encoding and decoding method of claim 1, wherein if there is at least one state in which each error of each register of the convolutional decoder is not detected, there is no error. The method according to claim 1 or 2, The second step, A fourth step of determining whether the length m of the cyclic margin check bit is greater than or equal to the decoding depth Γ when receiving the convolutional codeword; As a result of the fourth step, when the length m of the cyclic margin check bit is greater than or equal to the decoding depth Γ, the convolutional decoder outputs up to (n + m) -Γ bits, and outputs (n + m) A fifth step of performing a cyclic margin check by adding the? Bit and the? Bit in each state register of the convolutional decoder; As a result of the determination in the fourth step, when the length m of the cyclic margin check bit is smaller than the decoding depth Γ, the convolutional decoder outputs up to n bits, and outputs the n bits and the status registers of the convolutional decoder. a sixth step of performing a cyclic filter test by adding the m bits; And After performing a cyclic slack check, it is determined whether there is any state in which no error was detected, and if there was any state in which no error was detected, it was determined that no error was detected. Seventh Step Determining Detected Convolutional encoding and decoding method comprising a. The method of claim 3, wherein The third step, If it is determined that no error is detected in the seventh step, the convolutional encoding and decoding method according to the first n bits output from the convolutional decoder is determined as a message without error and transmitted. In the convolutional decoding method applied to the convolutional decoder, Receiving a convolutional codeword, determining whether the length m of the cyclic redundancy check bit is greater than or equal to the decoding depth Γ; As a result of the determination in the first step, when the length m of the cyclic margin check bit is greater than or equal to the decoding depth Γ, the convolutional decoder outputs up to (n + m) -Γ bits, and outputs (n + m) A second step of performing a cyclic margin check by adding the Γ bits and the Γ bits in each state register of the convolutional decoder; As a result of the determination of the first step, when the length m of the cyclic margin check bit is smaller than the decoding depth Γ, the convolutional decoder outputs up to n bits, and outputs the n bits and the status registers of the length three decoders. a third step of performing a cyclic filter test by adding m bits; And After performing the cyclic margin check, it is determined whether there is any state in which no error is detected. If there is any state in which no error is detected, the first n bits output from the convolutional decoder are judged as an error-free message, , Step 4 for determining that a message error has been detected if none of the conditions have not been detected Convolutional decoding method comprising a.