JP2002368723A - Detector, error correction device, and receiver using the error correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detector that can reduce deterioration in a signal of transmission data by using data before error correction when correction errors exist in the processing after error correction and to provide an error correction device, and a receiver using the error correction device. SOLUTION: A block code recovery section 45 recovers a received abbreviated Reed Solomon code to be a Reed Solomon code (RS[255, 239]). An error correction section 46 corrects an error in a code word and an inspection section 47 checks whether or not the block code after correction is corrected in excess of the error correction capability. Further, an abbreviated block code storage section 43 stores an abbreviated block code given to an error correction device 41 and a selection section 44 selects output data depending on an error correction flag received from the inspection section 47 to provide an output of the selected output data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction confirmation device for error correction, an error correction device, and a receiver using the error correction device.

[0002]

2. Description of the Related Art Generally, in order to cope with a bit error occurring when digital data is transmitted, a check code having an error correcting capability is added and transmitted, and an error position is detected and corrected in accordance with the check code on a receiving side. Is used. Further, in order to make the data after error correction more reliable, the check codes are efficiently allocated to the error correction capability and the error detection capability, and error correction processing for minimizing error correction is performed. In addition, confirmation processing is performed to determine whether or not the data after the error correction has been corrected.

Here, after transmitting data to which error correction parity has been added as digital data of a shortened block code, a method of determining whether or not data after error correction has been completely corrected is performed by using a received code. A method of performing error correction processing on a word, calculating the syndrome again for the result, and confirming whether the result becomes “0” or the like is adopted.

A conventional example of this kind will be described with reference to the drawings.

FIG. 1 is a block diagram of a conventional detecting device for detecting whether a corrected signal has been corrected beyond the block code correction capability.

In FIG. 1, a conventional detecting device for detecting whether or not a corrected signal has been corrected beyond the block code correcting capability includes a syndrome operation unit 11, an error value, an error position polynomial operation unit 12, an error It comprises a numerical value / error position calculation unit 13, a data delay unit 14, a correction unit 15, a re-syndrome calculation unit 16, and a re-syndrome evaluation unit 17.

[0007] The syndrome calculation unit 11 performs a syndrome calculation on the input codeword. The error numerical value and error position polynomial calculation unit 12 calculates an error numerical value polynomial and an error position polynomial from the syndrome. The error numerical value and error position calculation unit 13 calculates an error numerical value and an error position from the polynomial. The data delay unit 14 accumulates input data input from the syndrome operation unit 11. The correction unit 15 corrects an error. The re-syndrome calculation unit 16 calculates the syndrome again for the codeword after the error correction.
The re-syndrome evaluation unit 17 evaluates whether the error correction was correctly performed based on the value of the re-syndrome.

In a correction confirmation device for error correction,
The code word is the syndrome operation unit 11 and the data delay unit 14
Is input to The data delay unit 14 is delayed until the error numerical value and the operation result of the error position operation unit 13 are output. The syndrome of the codeword is obtained by the syndrome operation unit 11 and output to the error numerical value and error locator polynomial operation unit 12. The error numerical value and error position polynomial calculation unit 12 calculates an error numerical value polynomial and an error position polynomial from the syndrome. The error numerical value and error position calculating unit 13 calculates an error numerical value and an error position using the error numerical value polynomial and the error position polynomial. The correction unit 15 performs error correction on the codeword data stored in the data delay unit 14 using the error value and the error position. In the re-syndrome operation unit 16, the syndrome is obtained again for the codeword on which the error correction has been performed by the correction unit 15, and based on the result, the re-syndrome evaluation unit 17 evaluates whether the data after the error correction is correct. I do.

If the result of the re-syndrome is "0",
If it is correctly corrected and if it is other than "0", there is an erroneous correction in the error correction, which means that the code has been corrected beyond the code correction capability.

[0010]

However, the conventional detection device for detecting whether or not the corrected signal has been corrected beyond the block code correction capability needs to calculate the syndrome again, and the processing is not performed. There was a problem of becoming complicated.

Accordingly, the present invention has been made in view of the above-mentioned problems, and a detection device which can detect whether or not a corrected signal has been corrected beyond the block code correction capability with a simple process. An object of the present invention is to provide a correction device for performing correction and a receiver using the error correction device.

[0012]

In order to solve the above problems, the present invention employs means for solving the problems having the following features.

According to the first aspect of the present invention, there is provided a block code reproducing section for inserting a stuffing symbol to reproduce a block code before shortening from a shortened block signal, and an error correcting section for performing error correction using the reproduced block code. In a detection device having a correction unit and a detection unit that detects whether the signal corrected by the error correction unit has been corrected beyond the block code correction capability, the detection unit,
It is characterized in that it is detected whether or not the signal corrected based on the corrected stuffing symbol value exceeds the block code correction capability.

According to the first aspect of the present invention, in the detection device, the checking unit determines whether the signal corrected based on the corrected stuffing symbol value exceeds the block code correction capability. By detecting this, it is possible to provide a detection device that can detect whether or not the corrected signal has been corrected beyond the block code correction capability with simple processing.

According to a second aspect of the present invention, in the detection device according to the first aspect, the inspection unit determines that the corrected stuffing symbol value differs from the original stuffing symbol value by a predetermined number or more. , It is determined that the corrected signal has been corrected beyond the block code correction capability.

According to a second aspect of the present invention, in the detection device according to the first aspect, the inspection unit determines that the corrected stuffing symbol value differs from the original stuffing symbol value by a predetermined number or more. By judging that the corrected signal has been corrected beyond the block code correction capability, it is possible to provide a detection device that can make a determination only by comparing the values of the stuffing symbols.

According to a third aspect of the present invention, there is provided the detection apparatus according to the first or second aspect, a shortened block code storage unit for storing the input shortened block code, an output of the detection apparatus, and the shortening. And a selection unit for selecting one of the outputs of the converted block code accumulation unit, wherein the selection unit is controlled by an output from the inspection unit.

According to the third aspect of the present invention, the detecting device according to the first or second aspect, a shortened block code accumulating unit for accumulating the inputted shortened block code, an output of the detecting device, and the shortening. A selection unit that selects one of the outputs of the generalized block code accumulation unit, and the selection unit is selectively controlled by an output from the inspection unit, thereby providing an error correction device using the detection device. Can be provided.

According to a fourth aspect of the present invention, there is provided a receiver using the error correction device according to the third aspect.

According to the invention described in claim 4, it is possible to provide a receiver using the error correction device described in claim 3.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing embodiments of the present invention, the features of block codes will be described.

In general, in a block code, only a code of a specific length can be obtained depending on the generation method. For example, in the case of Reed-Solomon code, 8 bits (1 byte)
Is treated as one symbol, and when error correction is performed in symbol units, the length of a code (codeword) including data and parity for error correction must be 255 bytes.

The number of bits that can be corrected is determined in principle. For example, R is a kind of Reed-Solomon code.
With the S [255, 239] code (data length 239 bytes, parity length 16 bytes), up to 8 bytes, which is half the parity length, can be corrected. Error correction processing (decoding processing) for data containing an error exceeding this correction range
Is characterized in that the bit error rate is deteriorated compared to before the error correction.

Next, the shortening of the block code will be described. As described above, the block code needs to be a code word having a fixed length, and therefore, the length of data to be transmitted does not always match the length of data suitable for an error correction code. In such a case, a technique called shortening is used. The method of shortening will be described below with reference to FIG.

FIG. 2 is a diagram for explaining an example of shortening.

The Reed-Solomon code (RS
[255, 239]) 21 is an MPEG2 TS (Transp
ort Stream) packet 22, stuffing symbol 2
3, and an error correction parity 24.

Further, a shortened Reed-Solomon code (RS
[204,188]) 25 is the stuffing symbol 2
3 except for an MPEG2 TS packet 22 and an error correction parity 24.

FIG. 2 shows a case where an error correction parity 24 is added to an 188-byte MPEG2 TS packet 22 which is data to be transmitted using an RS [255, 239] code 21 which is a kind of Reed-Solomon code. think of. In this case, since the data length is fixed at 239 bytes, a predetermined predetermined value of data (stuffy symbol 23) for 51 bytes which is insufficient is added to generate a 16-byte error correction parity 24. Thus, a Reed-Solomon code 21 is created.

However, since the stuffing symbol 23 has only the role of filling the shortage of the data length, it is not added when data is actually transmitted, but is added before error correction is performed on the receiving side and transmitted. The data length is made as short as possible to reduce the transmission capacity, and the bandwidth is used effectively. This is called shortening, and the data transmitted here is shortened Reed-Solomon code (RS [204,
188]) 25.

Next, the principle of the present invention will be described with reference to FIG.

FIG. 3 is a diagram for explaining an example of an error correction detection method in error correction.

FIG. 3 shows a shortened Reed-Solomon code (RS [20]) as an error correction code added to digital data.
4,188]) 25 and 51 bytes of “0” are used as the stuffing symbol 23.

If the received data 31 contains only an error within 8 bytes, which is the error correction capability, 5
Both the 1-byte stuffing symbol 23 and the 188-byte data 31 are completely corrected.

However, when an error exceeding 8 bytes exceeding the error correction capability is included, both the stuffing symbol 23 and the data 31 are erroneously corrected.

That is, when the stuffing symbol 23 that is all “0” is not detected as all “0”, it can be confirmed that at least the error correction has been corrected beyond the block code correction capability. .

When the stuffing symbol 23, which is supposed to be "0", is erroneously corrected, the probability of being detected as "0" or "1" is equal.
/ 2. The probability that the 51-byte static symbol 23 of all "0" of the embodiment is detected as all "0" in spite of being erroneously corrected is extremely high to 1/2 408 (51 bytes x 8 bits). It is possible to detect that the error correction is low and almost completely corrected beyond the correction capability of the block code.

Therefore, if the error correction has been correctly performed, the corrected data is output. If the error correction has not been correctly performed, the data portion before the error correction is output. Degradation can be prevented.

Next, an embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a diagram of an example of a detection device and an error correction device.

4 includes an error correction device 41, a detection device 42, a shortened block code storage section 43, and a selection section 44. The detecting device 42 includes a block code reproducing unit 45, an error correcting unit 46, and a checking unit 47.

The block code reproducing section 45 adds a stuffing symbol to the input shortened Reed-Solomon code (RS [204,188]) to reproduce the Reed-Solomon code (RS [255,239]) before shortening. I do. The error correction unit 46 corrects the error of the code word, and the check unit 47 detects whether the data after the error correction has been corrected beyond the correction capability of the block code. Further, the shortened block code storage unit 43 stores the shortened block codes input to the error correction device 41, and the selection unit 44 controls the data to be output under the control of the error correction flag output from the check unit 47. Select and output.

The shortened Reed-Solomon code (RS [204,188]) input to the error correction device 41 is MPEG
2 is obtained by adding error correction parity (16 bytes) to the TS packet data (188 bytes).

The shortened Reed-Solomon code (RS [2
04,188]) is input to the detection device 42 and the shortened block code accumulation unit 43.

The shortened block code storage section 43 stores the input data as it is.

The block code reproducing section 45 adds a 51-byte stuffing symbol, which is all "0", to the shortened Reed-Solomon code (RS [204,188]) to generate a Reed-Solomon code (RS [255,239]).
To play. The Reed-Solomon code is sent to an error correction unit 46.
And corrects the error, and selects the data after the error correction
Then, the stuffing symbol after error correction is output to the checking unit 47.

The checking unit 47 compares whether the stuffing symbol after error correction matches the stuffing symbol (all “0”) added by the block code reproducing unit 45, and instructs the selecting unit 44 to match. If "1",
If they do not match, an error correction flag such as "0" is output.

According to the result of the error correction flag, if the flag is "1" (coincidence), the selection unit 44 selects the error correction unit 46.
The corrected MPEG2 TS packet output from
If the flag is "0" (mismatch), the MPEG-2 TS packet before error correction is output from the shortened block code stored in the shortened block code storage unit 43.

In the inspection section 47 of the present invention,
A flag can be output in accordance with the number of errors in the compared data, and the selection unit 48 can edit data or the like based on the flag output from the inspection unit 47.

Next, FIG. 5 shows a configuration example of the receiver.

The receiver shown in FIG.
1, an error correction device 41 and a video / audio decoding unit 52 are provided. The error correction device 41 includes a detection device 42, a shortened block code storage unit 43, and a selection unit 44.

FIG. 5 shows a receiving system for digital satellite broadcasting.

The digitally modulated wave transmitted through the transmission path is converted into a shortened Reed-Solomon code (RS [2
04, 188]). The shortened Reed-Solomon code is output to the detection device 42 and the shortened block code storage unit 43. The detection device 42 performs the above-described reproduction and error correction of the block code, and detects whether or not the block code has been corrected beyond the correction capability, and outputs an error correction flag and the TS packet (data portion) of MPEG2 after error correction. Output to the selection unit 44.

In the selecting section 44, according to the result of the error correction flag, if there is a match, the error corrected MPEG2
Is output to the video / audio decoding unit 52, and if the flags do not match, the uncorrected MPEG2 TS packet from the shortened block code stored in the shortened block code storage unit 47 , To the audio decoder 52.

The video / audio decoder 52 can reduce the deterioration of data during transmission by decoding the selected MPEG-2 TS packet data input from the selection unit 44.

FIG. 6 shows the effect of using the detection device, the error correction device, and the receiver using the same in the error correction of the present invention.

FIG. 6 is a diagram plotting a bit error rate of transmission data with respect to a required C / N (ratio of signal power to noise power at a receiver input terminal).

FIG. 6 shows the required C / N on the horizontal axis and the bit error rate on the vertical axis.
The plot values when error correction processing is performed are shown.

The plot values in the case where no error correction processing is performed on the Reed-Solomon code are shown.

By practicing the present invention, a plot value as shown in FIG. 6 can be obtained, the required C / N can be improved, and the signal degradation in transmission data can be reduced.

The input data used in the description of the present invention is not limited to the shortened Reed-Solomon code, but may be any signal to which specific data can be added.

The number of bytes of the stuffing symbol varies depending on the type of the block code to be shortened, and the value of the data is not limited to “0”.

[0062]

As described above, according to the present invention, when data after error correction is incorrectly corrected, signal deterioration in transmission data is reduced by using data before error correction processing. Detection device, error correction device,
And a receiver using the error correction device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a detection device in a conventional error correction.

FIG. 2 is a diagram for explaining an example of shortening.

FIG. 3 is an example of a diagram for explaining an error correction detection method in error correction.

FIG. 4 is a diagram illustrating an example of a detection device and an error correction device.

FIG. 5 is a diagram for describing a configuration example of a receiver.

FIG. 6 is a diagram for explaining an effect example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Syndrome operation part 12 Error numerical value, error position polynomial operation part 13 Error numerical value, error position operation part 14 Data delay part 15 Correction part 16 Re-syndrome operation part 17 Re-syndrome evaluation part 21 Reed-Solomon code (RS [255,239]) 22 MPEG-2 TS packet 23 Stuffing symbol 24 Error correction parity 25 Shortened Reed-Solomon code (RS [204, 18
8]) 31 data 41 error correction device 42 detection device 43 shortened block code storage unit 44 selection unit 45 block code reproduction unit 46 error correction unit 47 inspection unit 51 digital decoding unit 52 video and audio decoding unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5B001 AA01 AA06 AA11 AC01 AC04 AD06 5C059 MA00 RB10 RF02 RF05 RF07 SS06 TA76 TB03 TC22 TD18 UA04 5J065 AA01 AB01 AC02 AD01 AD11 AE07 AF02 AG02 AG03 AH01 AH09 GA02

Claims (4)

[Claims] 1. A block code reproducing unit that inserts a stuffing symbol and reproduces a block code before shortening from a shortened block signal, an error correcting unit that performs error correction using the reproduced block code, and an error correcting unit. A detection unit for detecting whether or not the signal corrected by the block code correction capability has been corrected beyond the block code correction capability, the inspection unit, the corrected signal based on the value of the stuffing symbol corrected Detecting whether or not is corrected beyond the block code correction capability. 2. The detection device according to claim 1, wherein the inspection unit is configured to, when the corrected stuffing symbol value differs from the original stuffing symbol value by a predetermined number or more, block code the corrected signal. A detection device for determining that correction has been made beyond the correction capability. 3. A detection device according to claim 1, wherein a shortened block code storage unit stores the input shortened block code; and an output of the detection device and an output of the shortened block code storage unit. An error correction device, comprising: a selection unit that selects one of the control units, wherein the selection unit is controlled by an output from the inspection unit. 4. A receiver using the error correction device according to claim 3.