JP2001237808A - Encoding device for cyclic redundancy check and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encoding device for cyclic redundancy check that can revise the number of protection object bits for cyclic redundancy check and the number of bits for redundancy check for each transmission frame depending on a transmission line error rate. SOLUTION: A CRC protection object bit group revision means 1 revises a protection object bit group depending on a transmission line error rate for each transmission frame and a CRC generation polynomial revision means 5 revises a generation polynomial in response to the protection object bit group to revise the number of bits. A CRC calculation means 6 calculates an output corresponding to the number of the protection object bits and a CRC addition means 7 adds the number of the protection object bits to a voice code stream and decodes the resulting stream to enhance the quality of audible sense of a decoded voice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding apparatus for a cyclic redundancy check mounted on a digital voice communication apparatus such as a digital portable telephone and a method thereof.

[0002]

2. Description of the Related Art Conventionally, in a digital portable telephone or the like, a speech signal is efficiently compressed into a code string (hereinafter referred to as a speech code string).
A speech encoding device is mounted to transmit the data. If an error is added on the transmission path when transmitting the speech code string, if the decoding is performed as it is, the decoded speech will be degraded. Therefore, protection measures against transmission path errors must be taken, and as a protection measure, an encoding device for cyclic redundancy check is used.

FIG. 8 is a characteristic diagram showing the relationship between the number of continuous error frames for a certain bit and the decoded speech quality using a conventional coding apparatus for cyclic redundancy check.

When the number of consecutive error frames is in the range of a, the degree of quality deterioration due to the guarantee processing is stronger,
Decoding as it is without protecting the bits reduces the quality degradation. When the number of consecutive error frames is in the range of b, if the decoding is performed without compensation, the degree of quality deterioration is increased. Therefore, it is possible to reduce the quality deterioration by protecting the bits and performing the compensation processing. Deterioration due to compensation processing is d for degradation c due to no compensation processing
Can be represented by

For example, in Japanese Patent Application Laid-Open No. 8-265304 (adaptive coding error control system), error detection is performed for each decoding result, and a decoding result in which no error is detected is regarded as a correct reception result. .

[0006]

However, in the conventional coding apparatus for cyclic redundancy check, the coding method must be determined according to the bit sensitivity at the time of designing the apparatus. Accordingly, the protection target bit group and the number of bits for redundancy check may not be changed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is desirable to change a protection target bit group for redundancy check and the number of bits for redundancy check for each transmission frame according to a transmission path error rate. It is an object of the present invention to provide an encoding device for cyclic redundancy check capable of performing the following.

[0008]

SUMMARY OF THE INVENTION An encoding apparatus for cyclic redundancy check of the present invention changes a group of bits to be protected for cyclic redundancy check according to a transmission path error rate, and outputs the changed group of bits to be protected and speech. Bit number changing means for changing the number of cyclic redundancy check bits from the code string.

With this configuration, the protection target bit group for the cyclic redundancy check and the number of bits for the cyclic redundancy check are changed according to the transmission path error rate, so that the quality of the decoded speech due to the transmission path error or the compensation processing is changed. Deterioration can be reduced and audibility can be further improved.

The coding apparatus for cyclic redundancy check of the present invention comprises:
Bit group changing means for changing the protection target bit group for the cyclic redundancy check according to the transmission path error rate, and changing the number of bits for changing the number of cyclic redundancy check bits from the changed protection target bit group and the speech code string Means.

With this configuration, the bit number changing means changes the protection target bit group for the cyclic redundancy check in accordance with the transmission path error rate, and the bit group changing means changes the protection target bit group and the speech code string. By changing the number of bits for the cyclic redundancy check from the above, the protection target bit group for the cyclic redundancy check and the number of bits for the cyclic redundancy check can be changed for each transmission frame according to the transmission path error rate.

The encoding apparatus for cyclic redundancy check of the present invention comprises:
Bit group changing means for changing the protection target bit group for the cyclic redundancy check according to the transmission path error rate; and calculation means for calculating the number of cyclic redundancy check bits from the changed protection target bit group and the speech code string. Adding means for adding the number of bits for cyclic redundancy check calculated by the calculating means to the bit string.

With this configuration, the number of bits for cyclic redundancy check is calculated by the calculating means from the protection target bit group changed by the bit group changing means and the speech code string, and calculated by the adding means. By adding the number of cyclic redundancy check bits to the bit sequence, it is possible to reduce the quality degradation of the decoded speech due to transmission path errors and compensation processing,
Hearing quality can be further improved.

The coding apparatus for cyclic redundancy check of the present invention comprises:
Bit group changing means for changing a protection target bit group for cyclic redundancy check according to a transmission path error rate; generator polynomial changing means for changing a generation polynomial for cyclic redundancy check from the changed number of protected bits; A calculating means for calculating the number of bits for the cyclic redundancy check from the generated generator polynomial and the speech code string; and an adding means for adding the number of bits for the cyclic redundancy check calculated by the calculating means to the bit string. .

With this configuration, the generator polynomial for the cyclic redundancy check is changed from the bit group to be protected changed by the bit group changing means, and the cyclic redundancy check bit is calculated from the changed generator polynomial and the speech code string. By calculating the number in the calculation means and adding the calculated number of bits for the cyclic redundancy check to the bit string, it is possible to reduce the quality degradation of the decoded voice due to the transmission path error and the compensation processing, and to further improve the audibility quality.

The encoding method for cyclic redundancy check of the present invention comprises:
Changing the protection target bit group for the cyclic redundancy check according to the transmission path error rate; and changing the number of cyclic redundancy check bits from the changed protection target bit group and the speech code string. To do.

By doing so, the protection target bit group for the cyclic redundancy check is changed according to the transmission path error rate,
Further, by changing the number of cyclic redundancy check bits from the changed protection target bit group and the speech code string, the quality degradation of decoded speech due to transmission path errors and compensation processing is reduced,
Hearing quality can be further improved.

The encoding method for the cyclic redundancy check of the present invention comprises:
Changing the protection target bit group for cyclic redundancy check according to the transmission path error rate; calculating the number of cyclic redundancy check bits from the changed protection target bit group and the speech code string; Adding the number of bits for redundancy check to the bit string.

By doing so, the protection target bit group for the cyclic redundancy check is changed according to the transmission path error rate,
The number of cyclic redundancy check bits is calculated from the changed protection target bit group and the speech code string, and the calculated number of cyclic redundancy check bits is added to the bit string, so that the decoded speech due to a transmission path error or compensation processing is obtained. The quality deterioration can be reduced, and the audible quality can be further improved.

The encoding method for the cyclic redundancy check of the present invention comprises:
A step of changing a protection target bit group for a cyclic redundancy check according to a transmission path error rate, a step of changing a generator polynomial for a cyclic redundancy check from the changed protection target bit group, and a changed generation polynomial and voice A step of calculating the number of bits for cyclic redundancy check from the code string; and a step of adding the calculated number of bits for cyclic redundancy check to the bit string.

By doing so, the protection target bit group for the cyclic redundancy check is changed according to the transmission path error rate,
The generator polynomial for cyclic redundancy check is changed from the changed protection target bit group, and then the number of cyclic redundancy check bits is calculated from the changed generator polynomial and the speech code string. Is added to the bit string, it is possible to reduce the deterioration of the quality of the decoded speech due to the transmission path error and the compensation processing, and to further improve the audibility quality.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The main object of the present invention is to set a protection target bit group for cyclic redundancy check and the number of bits for cyclic redundancy check to a transmission path error rate in a wireless environment in a mobile communication system such as a digital cellular phone. An object of the present invention is to improve the quality of decoded speech by changing the transmission frame in response.

Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a coding apparatus for cyclic redundancy check showing a configuration according to Embodiment 1 of the present invention.

In FIG. 1, a cyclic redundancy check (CRC: Cycli
c Redundancy Check) protection target bit group changing means 1 changes the protection target bit group according to the transmission path error rate. The CRC calculating means (calculating means) 2 calculates the input speech code string and the number of bits to be protected changed by the bit group changing means 1. CRC adding means (adding means) 3
Adds the number of bits calculated by the CRC calculation means 2 to the speech code string and sends it to the transmission path.

Next, the operation of the first embodiment will be described with reference to FIG. FIGS. 2 to 4 are characteristic diagrams showing the relationship between the channel error rate and the decoded voice quality for a certain number of bits.
3 illustrates three characteristic diagrams.

In the case of FIG. 2, if the decoding is performed without performing the compensation process on the error bit group regardless of the transmission path error rate, the degree of quality deterioration becomes large L, so that the error bit group is always protected. When the compensation processing is performed, K can improve the decoded voice quality, and can reduce the quality deterioration.

3 and 4, the quality degradation N and O due to decoding without compensating for the number of error bits and the quality degradation M and M due to compensation for the number of error bits are determined by the transmission path error rate. It can be seen that the magnitude of P changes.

In FIGS. 3 and 4, quality degradation N, N, due to decoding without performing compensation processing on the number of error bits.
O is larger, the number of bits is protected in the transmission path error rate, and the quality degradation M, P when the compensation processing is performed.
Can be reduced.

On the other hand, with regard to the transmission path error rate in which the quality degradation due to the compensation processing for the number of error bits is larger, the quality degradation can be reduced by directly decoding without protecting the number of error bits. Therefore, the protection target bit group changing means 1 for the cyclic redundancy check determines whether or not to protect each bit according to the transmission path error rate.

Next, an example of how to change the protection target bit group for the cyclic redundancy check in the cyclic redundancy check protection target bit group changing means 1 will be described. For each bit group, the sensitivity to the quality degradation of the decoded speech with the bit number error is measured in advance.

Here, as shown in FIG. 5, some thresholds A to C are set, and the number of bits higher than the thresholds A to C is classified into classes. As the transmission path error rate increases, the thresholds are decreased as B and C, and the bit groups having higher sensitivity than those thresholds are set as the protection target bit groups for the cyclic redundancy check.

As described above, by changing the protection target bits for the cyclic redundancy check in accordance with the transmission path error rate, it is possible to suppress the deterioration of the quality of the decoded voice due to the transmission path error or the compensation processing, and to improve the audibility quality. it can.

(Embodiment 2) FIG. 6 shows a coding apparatus for cyclic redundancy check showing a configuration in Embodiment 2 of the present invention.

In FIG. 6, the CRC protection target bit group changing means 1 changes the protection target bit group for the cyclic redundancy check according to the transmission path error rate. CRC
The generator polynomial changing means 5 changes the generator polynomial for cyclic redundancy check according to the changed protection target bit group.

The CRC calculating means (calculating means) 6 calculates the number of bits to be protected based on the input speech code string and the output of the CRC generating polynomial changing means 5. The CRC adding means (adding means) 7 adds the number of CRC bits calculated by the CRC calculating means 6 to the speech code string.

Next, the operation of the second embodiment will be described. In FIG. 6, the operations of the CRC protection target bit group changing unit 1, the CRC calculating unit 6, and the CRC adding unit 6 are the same as those of the first embodiment, and therefore only the operation of the CRC generating polynomial changing unit 7 will be described. .

The CRC generating polynomial changing means 7 changes the CRC generating polynomial based on the change of the CRC protected bit group output from the CRC protected bit group changing means 1. For example, in a transmission frame with a high transmission path error rate and an increased number of bits to be protected, the error bit oversight rate can be reduced by increasing the order of the CRC bit generation polynomial and increasing the number of CRC bits.

As described above, the CRC generating polynomial changing means 7
Then, according to the CRC protection target bit group changed by the CRC protection target group changing means 4, the degree of the CRC bit generation polynomial is changed, and the CRC bit group is changed, thereby lowering the error bit oversight rate. Can be. By doing so, it is possible to reduce the quality degradation of the decoded voice due to the transmission path error, and to further improve the audibility.

(Embodiment 3) FIG. 7 shows a coding apparatus for cyclic redundancy check showing a configuration according to Embodiment 3 of the present invention. In FIG. 7, CRC protection target bit group changing means 1
Is designed to change the CRC protection target bit group according to the transmission path error rate.

The CRC calculating means includes a CRC bit number changing means 9 according to the input speech code string and the protection target bit group changed by the CRC protection bit group changing means 4.
Can output the calculated signal.

The CRC bit number changing means 9 can change the number of bits to be protected by the CRC based on the calculation output of the CRC calculating means 8.

The CRC adding means 10 changes the number of bits used for error detection among the CRC bits, thereby adding the CRC bit number changed by the CRC bit number changing means 10 to the speech code string. .

Next, the operation of the third embodiment will be described. In FIG. 7, the operations of the CRC protection target bit group changing unit 1, the CRC calculating unit 8, and the CRC adding unit 10 are as follows.
Since the operation is the same as that of the second embodiment, the operation of the CRC bit number changing means 10 will be described.

The CRC bit number changing means 9 changes the CRC bit number based on the calculation output of the CRC calculating means 8 and sends the changed CRC bit number to the CRC adding means 10, and the CRC changed by the CRC adding means 10 The number of bits can be added to the speech code string.

For example, in a transmission frame having a high transmission path error rate and an increased number of bits to be protected, the CRC calculation means 8
By changing the number of CRC bits in the CRC bit group calculated in step (1) and adding it to the speech code string, the number of bit groups used for error detection can be increased, and the error bit oversight rate can be reduced.

In the CRC calculating means 9, a sufficiently high-order CRC
The CRC bits are calculated using a generator polynomial. As described above, of the calculated CRC bits, the number of bits used for error detection among the calculated CRC bits is changed and added to the speech code string in accordance with the number of bits of the CRC protection target changed by the number of bits of CRC protection target 9. Accordingly, the error bit oversight rate can be reduced. By doing so, it is possible to reduce the quality degradation of the decoded voice due to the transmission path error, and to further improve the audibility.

In the first to third embodiments described above, the CRC protection bit group changing unit changes the CRC protection bit group in accordance with the transmission path error rate, so that the transmission path error or the compensation processing is performed. Thus, it is possible to reduce the degradation of the decoded voice due to

In a transmission frame having a high transmission path error rate and an increased number of CRC protection target bits, an error bit oversight rate becomes high. Therefore, by increasing the number of CRC bits used for error detection, the error bit oversight rate can be reduced, the degradation of decoded speech due to a transmission path error is reduced, and the audibility quality can be further improved.

[0049]

As described above, according to the present invention, a protection target bit group for cyclic redundancy check and the number of bits for redundancy check can be changed for each transmission frame according to the transmission path error rate. An encoding device for inspection can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a coding apparatus for cyclic redundancy check according to Embodiment 1 of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a transmission path error rate and decoded speech in the apparatus of FIG.

FIG. 3 is a characteristic diagram showing a relationship between a transmission line error rate and decoded speech in the apparatus of FIG. 1;

FIG. 4 is a characteristic diagram showing a relationship between a transmission line error rate and decoded speech in the apparatus of FIG. 1;

FIG. 5 is a characteristic diagram showing a relationship between a bit sensitivity and a bit number in the device of FIG. 1;

FIG. 6 is a block diagram showing a configuration of a coding apparatus for cyclic redundancy check in Embodiment 2 of the present invention.

FIG. 7 is a block diagram showing a configuration of a coding apparatus for cyclic redundancy check according to Embodiment 3 of the present invention.

FIG. 8 is a characteristic diagram obtained by using a conventional encoding device for cyclic redundancy check;

[Explanation of symbols]

1 CRC protection target bit group changing means (bit group changing means) 2, 6, 8 CRC calculating means (calculating means) 3, 7, 10 CRC adding means (adding means) 5 CRC generating polynomial changing means (generating polynomial changing means) 9 CRC protection target bit number changing means (bit number changing means)

Continued on the front page F term (reference) 5B001 AA04 AB03 AD06 5J065 AA01 AB01 AC02 AD04 AE06 AF03 AH13 AH20 5K014 AA01 BA06 EA08 FA11 FA13 GA02 HA10 5K067 AA01 AA23 BB02 EE02 EE10 HH21 HH26

Claims (7)

[Claims] A bit number changing means for changing a protection target bit group for a cyclic redundancy check according to a transmission path error rate, and changing a cyclic redundancy check bit number from the changed protection target bit group and a speech code string. A coding apparatus for cyclic redundancy check, comprising: 2. A bit group changing means for changing a protection target bit group for a cyclic redundancy check according to a transmission path error rate, and determining a cyclic redundancy check bit number from the changed protection target bit group and a speech code string. An encoding device for a cyclic redundancy check, comprising: a number of bits to be changed. 3. A bit group changing means for changing a protection target bit group for a cyclic redundancy check in accordance with a transmission path error rate, and determining a cyclic redundancy check bit number from the changed protection target bit group and a speech code string. An encoding device for cyclic redundancy check, comprising: a calculating means for calculating; and an adding means for adding the number of bits for cyclic redundancy check calculated by said calculating means to a bit string. 4. A bit group changing means for changing a group of bits to be protected for a cyclic redundancy check according to a transmission path error rate, and a generator polynomial for changing a generator polynomial for a cyclic redundancy check from the changed group of bits to be protected. Changing means, calculating means for calculating the number of bits for cyclic redundancy check from the changed generator polynomial and the speech code string, and adding means for adding the number of bits for cyclic redundancy check calculated by the calculating means to the bit string, An encoding device for a cyclic redundancy check, comprising: 5. A step of changing a group of bits to be protected for a cyclic redundancy check according to a transmission path error rate, and a step of changing the number of bits for a cyclic redundancy check from the changed group of bits to be protected and a speech code string. And a coding method for a cyclic redundancy check. 6. A step of changing a protection target bit group for cyclic redundancy check according to a transmission path error rate, and a step of calculating the number of bits for cyclic redundancy check from the changed protection target bit group and a speech code string. And a step of adding the calculated number of bits for cyclic redundancy check to the bit string. A coding method for cyclic redundancy check. 7. A step of changing a group of bits to be protected for a cyclic redundancy check according to a transmission path error rate, and a step of changing a generator polynomial for a cyclic redundancy check from the changed group of bits to be protected. Calculating the number of bits for cyclic redundancy check from the generated polynomial and the speech code string, and adding the calculated number of bits for cyclic redundancy check to the bit string. Encoding method.