JP6549889B2 - Decoding apparatus, receiver, wireless transmission system and error detection method - Google Patents

Description

  The present invention relates to a decoding device, a receiver, a wireless transmission system, and an error detection method.

  In digital wireless transmission, generally, an error correction code represented by a convolutional code is used to correct an error occurring in a propagation path. FIG. 3 is a diagram showing a configuration example of the transmitter 30 and the receiver 40 in the case of using a convolutional code.

  The transmitter 30 includes a convolutional encoding unit 31, a modulation unit 32, a power amplification unit 33, and a transmission antenna 34. The convolutional coding unit 31 performs convolutional coding on the input digital signal. The modulation unit 32 modulates the signal after convolutional coding, the power amplification unit 33 performs power amplification of the signal after modulation, and transmits the signal from the transmission antenna 34.

  The receiver 40 includes a reception antenna 41, a reception amplification unit 42, a demodulation unit 43, and a convolutional code decoding unit 44. The reception amplification unit 42 amplifies the reception signal of the reception antenna 41, and the demodulation unit 43 demodulates the amplified signal. The convolutional code decoding unit 44 performs convolutional code decoding on the demodulated signal and outputs a digital signal. Hard-decision Viterbi decoding or soft-decision Viterbi decoding is widely used as decoding of convolutional codes.

  If the quality of the propagation path is poor, errors may be left (included) in the signal after decoding of the convolutional code, and the remaining errors may affect the subsequent system of the receiver. For example, in the case of an audio signal, there arises a problem that a large noise is generated on the receiving side. Here, if it is possible to detect that an error is included in the decoded signal, it is possible to take measures to prevent the influence on the subsequent system. For example, in the case of an audio signal, generation of noise can be prevented by taking measures such as not reproducing the audio signal containing an error.

  As a method of detecting whether or not an error is included in a digital signal, there is a method of using an error detection code represented by a CRC (Cyclic Redundancy Check) code (for example, see Patent Documents 1 to 3).

  FIG. 4 is a diagram showing a configuration example of the transmitter 30a and the receiver 40a in the case of using an error detection code. In FIG. 4, the same components as in FIG. 3 will be assigned the same reference numerals and descriptions thereof will be omitted.

  In the transmitter 30 a, an error detection coding unit 35 is provided at a stage before the convolutional coding unit 31. The error detection coding unit 35 performs error detection coding on the input digital signal. Thereafter, as with transmitter 30, convolutional coding, modulation and power amplification are performed.

  In the receiver 40a, an error detection and decoding unit 45 is provided at a stage subsequent to the convolutional code decoding unit 44. The error detection decoding unit 45 performs error detection decoding on the signal after decoding the convolutional code, and outputs error detection information indicating whether the digital signal obtained by the error detection decoding and the digital signal includes an error. Do.

JP 2014-209699 A JP, 2014-112815, A Unexamined-Japanese-Patent No. 2015-23460

  When using an error detection code, it is necessary to add an error detection bit to the digital signal. However, depending on the wireless transmission system, the number of bits of the transmission unit (frame) is small, and the addition of the error detection bit may make it impossible to secure a necessary error correction coding rate and a transmission rate of information.

  For example, it is assumed that one frame is 39 bits and the error correction coding rate is 2/3 (= 0.67). In this case, as shown in FIG. 5 (b), a 13-bit error correction code is added to the 26 information bits shown in FIG. 5 (a).

  Here, it is assumed that a 4-bit error detection code needs to be added for error detection. Since 39 bits are reached by the information bits (26 bits) and the error correction code (13 bits), to add a 4-bit error detection code, as shown in FIG. 5C, the error correction code is added. A method of reducing the number of 4 bits and adding an error detection bit and a method of reducing an information bit by 4 bits and adding an error detection bit as shown in FIG. 5D can be considered.

  However, if the error correction code is reduced, the coding rate becomes 10/13 (= 0.77), and the error correction capability is reduced. Also, reducing the information bits will reduce the information transmission rate. Therefore, there is a need for a technique for detecting whether or not an error is included in a signal after decoding while suppressing deterioration in communication performance such as a reduction in error correction capability and a reduction in information transmission rate.

  An object of the present invention is to solve the above-described problems, and to suppress deterioration in communication performance, and to detect whether or not an error is included in a signal after decoding, a receiver, a wireless transmission system, and An object of the present invention is to provide an error detection method.

In order to solve the above problems, the decoding device according to the present invention receives a signal on which convolutional coding has been performed as an error correction code for a digital signal, decodes the input signal, and outputs a decoded signal. A decoding apparatus, comprising: a soft decision Viterbi decoding unit performing soft decision Viterbi decoding on the input signal; a hard decision Viterbi decoding unit performing hard decision Viterbi decoding on the input signal; and the soft decision Viterbi decoding unit A decoding result for outputting first error detection information indicating whether or not an error is included in the output signal of the decoding device based on whether or not the decoding result of the hard decision Viterbi decoding unit matches the decoding result of the hard decision Viterbi decoding unit And a comparison unit.

  Preferably, the decoding device according to the present invention further comprises an output unit for outputting one of the decoding result of the soft decision Viterbi decoding unit and the decoding result of the hard decision Viterbi decoding unit as the output signal.

  Further, in the decoding device according to the present invention, the input signal is a signal obtained by performing convolutional coding after error detection coding is performed on a digital signal, and the decoding result of the soft decision Viterbi decoding unit And an output unit for outputting one of the decoding results of the hard decision Viterbi decoding unit, error detection decoding is performed on the decoding result output from the output unit, and a signal after decoding is output as the output signal, It is preferable to further include an error detection and decoding unit that outputs second error detection information indicating whether the output signal contains an error.

  In the decoding device according to the present invention, preferably, the output unit outputs the decoding result of the soft decision Viterbi decoding unit.

  Further, in order to solve the above problems, a receiver according to the present invention receives a signal on which convolutional coding has been performed as error correction coding for a digital signal, decodes the received signal, and decodes the received signal. A receiver that outputs a signal, comprising any one of the above-described decoding devices, which decodes the received signal.

Further, to solve the above problems, a wireless transmission system according to the present invention comprises a transmitter for wirelessly transmitting a signal subjected to convolutional encoding as an error correction code for a digital signal; A radio transmission system comprising: a receiver for performing decoding and outputting a signal after decoding, the receiver comprising: a soft decision Viterbi decoding unit for performing soft decision Viterbi decoding on the received signal; A hard decision Viterbi decoding unit that performs hard decision Viterbi decoding on a signal, and whether the decoding result of the soft decision Viterbi decoding unit matches the decoding result of the hard decision Viterbi decoding unit And a decoding result comparison unit that outputs first error detection information indicating whether the output signal includes an error.

Further, in order to solve the above problems, in the error detection method according to the present invention, a signal subjected to convolutional coding as error correction coding for a digital signal is input, and decoding is performed on the input signal. An error detection method in a decoding apparatus for outputting a signal, comprising: performing soft decision Viterbi decoding on the input signal; performing hard decision Viterbi decoding on the input signal; and performing the soft decision Viterbi decoding Outputting first error detection information indicating whether the output signal of the decoding apparatus contains an error based on whether the decoding result matches the decoding result of the hard decision Viterbi decoding Including.

  According to the decoding device, the receiver, the wireless transmission system, and the error detection method according to the present invention, whether or not an error is included in the signal after decoding is detected without deteriorating the transmission rate of the information and the error correction capability. be able to.

It is a figure showing the composition of the radio transmission system concerning a 1st embodiment of the present invention. It is a figure which shows the structure of the radio | wireless transmission system which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of a related transmitter and receiver. It is a block diagram which shows the other structural example of a related transmitter and receiver. It is a figure for demonstrating the subject of a prior art.

  Hereinafter, embodiments of the present invention will be described.

First Embodiment
FIG. 1 is a diagram showing the configuration of a wireless transmission system 1 according to a first embodiment of the present invention.

  The wireless transmission system 1 shown in FIG. 1 includes a transmitter 10 and a receiver 20.

  The transmitter 10 wirelessly transmits a signal obtained by performing convolutional coding on a digital signal (for example, a voice signal). The receiver 20 receives the transmission signal of the transmitter 10, decodes a convolutional code for the reception signal, and outputs the digital signal obtained by the decoding to a subsequent system (for example, an audio reproduction system).

  Next, configurations of the transmitter 10 and the receiver 20 will be described with reference to FIG.

  First, the configuration of the transmitter 10 will be described.

  The transmitter 10 shown in FIG. 1 includes a convolutional encoding unit 11, a modulation unit 12, a power amplification unit 13, and a transmission antenna 14.

  The convolutional coding unit 11 receives a digital signal, performs convolutional coding on the input digital signal, and outputs the signal after convolutional coding to the modulation unit 12.

  The modulator 12 modulates the output signal of the convolutional encoder 11 according to a predetermined modulation scheme, and outputs the modulated signal to the power amplifier 13.

  The power amplification unit 13 amplifies the power of the output signal of the modulation unit 12 and transmits it from the transmission antenna 14.

  Next, the configuration of the receiver 20 will be described.

  The receiver 20 shown in FIG. 1 includes a reception antenna 21, a reception amplification unit 22, a demodulation unit 23, and a decoding device 24.

  The reception amplification unit 22 amplifies the signal transmitted from the transmitter 10 and received by the reception antenna 21, and outputs the amplified signal to the demodulation unit 23.

  The demodulation unit 23 demodulates the output signal of the reception amplification unit 22 by a demodulation method corresponding to the modulation method of the transmitter 10, and outputs the signal after demodulation to the decoding device 24.

  The decoding device 24 decodes the convolutional code with respect to the output signal of the demodulation unit 23, and outputs the digital signal obtained by the decoding as an output signal to the subsequent system. Further, the decoding device 24 outputs error detection information indicating whether or not an error is included in the output signal based on the result of decoding of the convolutional code.

  The decoding device 24 includes a soft decision Viterbi decoding unit 25, a hard decision Viterbi decoding unit 26, an output unit 27, and a decoding result comparison unit 28. The output signal of the demodulator 23 is input to the soft decision Viterbi decoder 25 and the hard decision Viterbi decoder 26.

  The soft decision Viterbi decoding unit 25 performs soft decision Viterbi decoding on the input signal (the output signal of the demodulation unit 23), and outputs the decoding result to the output unit 27 and the decoding result comparison unit 28.

  The hard decision Viterbi decoding unit 26 performs hard decision Viterbi decoding on the input signal (the output signal of the demodulation unit 23), and outputs the decoding result to the output unit 27 and the decoding result comparison unit 28.

  The output unit 27 outputs one of the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26 as an output signal of the decoding device 24 to the system at the subsequent stage of the receiver 20. In general, soft decision Viterbi decoding can obtain better bit error rate characteristics than hard decision Viterbi decoding. Therefore, the output unit 27 normally outputs the decoding result of the soft decision Viterbi decoding unit 25 as an output signal of the decoding device 24.

  The decoding result comparison unit 28 outputs error detection information (first error detection information) based on comparison between the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26. More specifically, the decoding result comparison unit 28 generates a soft decision Viterbi decoding unit in an arbitrary frame section, for example, in a frame section divided by 24 bits in the case of a digital audio signal in which one sample is quantized by 24 bits. The result of decoding 25 is compared with the result of decoding of the hard decision Viterbi decoder 26.

  In general, even if the decoding method is different, there is a characteristic that when the error correction succeeds without any error remaining, the decoding results match. In addition, when the decoding method is different, there is a characteristic that the probability that the remaining error bits are different is high when the error correction fails.

  Based on these characteristics, when the decoding result of the soft decision Viterbi decoding unit 25 matches the decoding result of the hard decision Viterbi decoding unit 26, the decoding result comparison unit 28 includes an error in the output signal of the decoding device 24. It outputs error detection information indicating that it is not possible. On the other hand, when the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26 do not match, the decoding result comparison unit 28 indicates that the output signal of the decoding device 24 contains an error. Output error detection information.

  As described above, according to the present embodiment, the decoding device 24 includes the soft decision Viterbi decoding unit 25 that performs soft decision Viterbi decoding, the hard decision Viterbi decoding unit 26 that performs hard decision Viterbi decoding, and the soft decision Viterbi decoding unit 25. The decoding result comparison unit 28 outputs error detection information indicating whether an output signal of the decoding device 24 includes an error based on the comparison between the decoding result and the decoding result of the hard decision Viterbi decoding unit 26.

  As described above, when the results of different decoding methods are compared, if the error correction is successful, the decoding result matches, and if the error correction fails, the error bit remains differently, so the decoding result is There is a high probability that they do not match. Therefore, by comparing the decoding result of the soft decision Viterbi decoding with the decoding result of the hard decision Viterbi decoding, it is possible to detect whether an error is included in the output signal. Also, since no error detection code is used, error detection can be performed while suppressing deterioration in communication performance such as a decrease in error correction capability and a decrease in information transmission rate.

Second Embodiment
In the first embodiment, although the example in which the error detection code is not used is described, there is also a wireless transmission system in which the addition of the error detection code is permitted. However, even when an error detection code is used, a so-called “error miss” may occur, in which no error is determined even though an error is included in the signal after decoding. There is a need to reduce the frequency of false negatives.

  In the first embodiment, an example in which error detection information is obtained from a result of decoding of a convolutional code without using an error detection code has been described. The present invention can also be applied to digital wireless transmission using an error detection code, and by applying the present invention, the frequency of occurrence of false negative can be reduced. Hereinafter, a second embodiment of the present invention will be described.

  FIG. 2 is a diagram showing the configuration of a wireless transmission system 1a according to a second embodiment of the present invention.

  The wireless transmission system 1a shown in FIG. 2 is different from the wireless transmission system 1 according to the first embodiment in that the transmitter 10 is changed to the transmitter 10a and the receiver 20 is changed to the receiver 20a. And are different.

  The transmitter 10a wirelessly transmits a signal subjected to error detection coding and convolutional coding to the digital signal. The receiver 20 receives the transmission signal of the transmitter 10, decodes the reception signal (convolutional code decoding and error detection decoding), and outputs the digital signal obtained by the decoding to the subsequent system.

  Next, the configurations of the transmitter 10a and the receiver 20a will be described with reference to FIG.

  First, the configuration of the transmitter 10a will be described.

  The transmitter 10a shown in FIG. 2 is different from the transmitter 10 shown in FIG. 1 in that an error detection coding unit 15 is added.

  The error detection coding unit 15 is provided at the previous stage of the convolutional coding unit 11, performs error detection coding such as CRC coding on the input digital signal, and convolutes the signal after error detection coding. It is output to the encoding unit 11. Thereafter, as in the transmitter 10, convolutional coding, modulation and power amplification are performed, and a signal is transmitted from the transmitting antenna.

  Next, the configuration of the receiver 20a will be described.

  The receiver 20a shown in FIG. 2 is different from the receiver 20 shown in FIG. 1 in that the decoding device 24 is changed to the decoding device 24a.

  The decoding device 24a includes a soft decision Viterbi decoding unit 25, a hard decision Viterbi decoding unit 26, an output unit 27a, a decoding result comparison unit 28, and an error detection decoding unit 29.

  The soft-decision Viterbi decoder 25 and the hard-decision Viterbi decoder 26 respectively perform soft-decision Viterbi decoding and hard-decision Viterbi decoding on the input signal (the output signal of the demodulator 23) as in the first embodiment. The decoded result is output to the output unit 27a and the decoded result comparison unit 28.

  The output unit 27a receives the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26, and outputs one of them to the error detection decoding unit 29. As described above, in general, soft decision Viterbi decoding can obtain better bit error rate characteristics than hard decision Viterbi decoding. Therefore, the output unit 27 a normally outputs the decoding result of the soft decision Viterbi decoding unit 25 to the error detection decoding unit 29.

  As in the first embodiment, the decoding result comparison unit 28 performs error detection information (first error detection) based on comparison between the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26. Output information).

  The error detection and decoding unit 29 performs error detection decoding on the output signal of the output unit 27a, and the digital signal obtained by the error detection and decoding and error detection information indicating whether or not the digital signal contains an error (2) error detection information) is output to the subsequent system.

  As described above, the decoding result comparison unit 28 outputs error detection information (first error detection information) obtained by comparing the decoding results of the soft decision Viterbi decoding unit 25 and the hard decision Viterbi decoding unit 26. Further, the error detection decoding unit 29 outputs error detection information (second error detection information) obtained by the error detection decoding. Therefore, the decoding device 24a according to the present embodiment includes the error detection information (first error detection information) obtained from the decoding of the convolutional code and the error detection information (second error detection information obtained from the error detection decoding). Outputs two pieces of error detection information.

  In the subsequent system, when at least one of the first error detection information and the second error detection information indicates that an error is included in the output signal, it is possible to take measures to prevent the influence of the error. By doing this, the possibility of adverse effects on the system due to the inclusion of errors can be reduced.

  As described above, even in the case of using an error detection code, an error miss may occur, and it is required to reduce the occurrence frequency of the error miss. The receiver 40a shown in FIG. 4 only obtains the error detection information from the error detection decoding, and can not reduce the frequency of occurrence of the error miss.

  On the other hand, in the decoding device 24a according to the present embodiment, the error detection information (first error detection information) obtained from the decoding of the convolutional code and the error detection information (second error detection) obtained from the error detection decoding Since two pieces of error detection information (information) can be obtained, it is possible to reduce the frequency of missed errors.

  For example, when the decoding result of the soft decision Viterbi decoding unit 25 including an error is output to the error detection decoding unit 29 via the output unit 27a, an error miss occurs in the error detection decoding unit 29, and an output signal is generated. Error detection information may be output indicating that no error is included.

  In this embodiment, since an error is included in the decoding result of the soft decision Viterbi decoding unit 25, there is a possibility that the decoding result of the soft decision Viterbi decoding unit 25 and the decoding result of the hard decision Viterbi decoding unit 26 do not match. high. Therefore, since the decoding result comparison unit 28 is highly likely to output error detection information indicating that an error is included, it is possible to reduce the frequency of occurrence of an error miss.

  As described above, according to the present embodiment, the decoding device 24 a includes the soft decision Viterbi decoding unit 25 that performs soft decision Viterbi decoding, the hard decision Viterbi decoding unit 26 that performs hard decision Viterbi decoding, and the soft decision Viterbi decoding unit 25. A decoding result comparison unit 28 that outputs error detection information (first error detection information) based on comparison between the decoding result and the decoding result of the hard decision Viterbi decoding unit 26, the soft decision Viterbi decoding unit 25, and the hard decision Viterbi decoding And an error detection / decoding unit 29 which performs error detection decoding on any of the decoding results of the unit 26 and outputs error detection information (second error detection information).

  Therefore, two types of error detection information are obtained: error detection information (first error detection information) based on convolutional code decoding and error detection information (second error detection information) based on error detection decoding. It is possible to reduce the frequency of missed notices.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, functions included in each block can be rearranged so as not to be logically inconsistent, and a plurality of blocks can be combined into one or divided.

DESCRIPTION OF SYMBOLS 10, 10a Transmitter 11 Convolutional encoding part 12 Modulation part 13 Power amplification part 14 Transmission antenna 15 Error detection encoding part 20 Receiver 21 Reception antenna 22 Reception amplification part 23 Demodulation part 24, 24a Decoding device 25 Soft decision Viterbi decoding part 26 Hard-decision Viterbi Decoding Unit 27, 27a Output Unit 28 Decoding Result Comparison Unit 29 Error Detection Decoding Unit

Claims (7)

A signal that is input as a signal subjected to convolutional coding as error correction for a digital signal, is decoded with respect to the input signal, and outputs the signal after decoding,
A soft decision Viterbi decoding unit that performs soft decision Viterbi decoding on the input signal;
A hard decision Viterbi decoding unit for performing a hard decision Viterbi decoding on the input signal;
A first error detection indicating whether the output signal of the decoding apparatus includes an error based on whether the decoding result of the soft decision Viterbi decoding unit matches the decoding result of the hard decision Viterbi decoding unit A decryption result comparison unit that outputs information;
A decoding apparatus comprising: In the decoding device according to claim 1,
A decoding apparatus characterized by further comprising: an output unit for outputting one of the decoding result of the soft decision Viterbi decoding unit and the decoding result of the hard decision Viterbi decoding unit as the output signal. In the decoding device according to claim 1,
The input signal is a signal subjected to convolutional coding after error detection coding is performed on a digital signal,
An output unit configured to output one of a decoding result of the soft decision Viterbi decoding unit and a decoding result of the hard decision Viterbi decoding unit;
Second error detection information that performs error detection decoding on the decoding result output from the output unit, outputs a signal after decoding as the output signal, and indicates whether the output signal includes an error An error detection and decoding unit that outputs
The decoding apparatus further comprising: In the decoding device according to claim 2 or 3,
The output unit outputs the decoding result of the soft decision Viterbi decoding unit. A receiver that receives a signal subjected to convolutional coding as error correction coding for a digital signal, decodes the received signal, and outputs the decoded signal.
A receiver comprising the decoding device according to any one of claims 1 to 4, wherein the decoding device decodes the received signal. A wireless transmission comprising: a transmitter for wirelessly transmitting a signal subjected to convolutional encoding as error correction to a digital signal; and a receiver for receiving the signal, decoding the received signal, and outputting the decoded signal A system,
The receiver is
A soft decision Viterbi decoding unit that performs soft decision Viterbi decoding on the received signal;
A hard decision Viterbi decoding unit that performs hard decision Viterbi decoding on the received signal;
A first error detection indicating whether the output signal of the receiver includes an error based on whether the decoding result of the soft decision Viterbi decoding unit matches the decoding result of the hard decision Viterbi decoding unit A decryption result comparison unit that outputs information;
A wireless transmission system comprising: A method for detecting an error in a decoding apparatus which receives a signal subjected to convolutional coding as error correction for a digital signal, decodes the input signal, and outputs the decoded signal.
Performing soft decision Viterbi decoding on the input signal;
Performing hard decision Viterbi decoding on the input signal;
The first error detection information indicating whether or not the output signal of the decoding apparatus contains an error based on whether or not the decoding result of the soft decision Viterbi decoding and the decoding result of the hard decision Viterbi decoding match. Step to output,
An error detection method comprising:

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