JPH11122228A - Data communication method/device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction of communication speed by permitting a transmission side to transmit final retransmission data without adding an error detection code when the number of retransmission times, which can be requested, is limited. SOLUTION: When a retransmission request and the frame number of a frame, which is retransmission-requested, are inputted from B, a transmission side retransmission controller 107 transmits a memory address corresponding to the frame number and a control signal to a retransmission memory 103. A signal for selecting the retransmission memory is sent to a selector 104 and the frame number to a frame number adder 106. When the retransmission request is not the final retransmission request, a transmission side retransmission controller 107 outputs an on-control signal to an error detection encoder 105 and outputs an off-control signal when it is the final retransmission request. Namely, the data as it is corresponding to the retransmission request of the retransmission memory 103 is outputted to a communication line only by adding the frame number in the case of the final retransmission request.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an automatic retransmission system (A
The present invention relates to a data communication method and apparatus using a communication method called RQ (Automatic Repeat Request), and is particularly suitable for a data communication method and apparatus when the number of retransmissions is limited.

[0002]

[Prior art]

Reference: Japanese Patent Application Laid-Open No. 8-65279, "ARQ Communication Method and Apparatus Using Weighted Majority Decoding" An error correction technique using a communication method called automatic retransmission (ARQ) is disclosed in the above-mentioned reference.

One of the communication methods for ensuring that correct data can be transmitted even in an erroneous environment such as wireless communication is a communication method called the automatic repeat request (ARQ) described above. This communication method is a communication technique based on error detection and data retransmission, and is based on the following communication operation.

[0004] First, on the transmission side, data to be transmitted (encoded bit string) is divided into units called frames, and an error detection code such as a CRC (cyclic redundancy check) code and a frame number are added to the communication path. Sent to

[0005] On the other hand, the receiving side checks whether there is an error in the received frame using an error detection code. The frame in which the error is not confirmed is passed to the subsequent processing unit, and the frame number of the frame in which the error is confirmed is notified to the transmitting side, and retransmission of the same frame is requested.

[0006] Upon receiving the retransmission request (ARQ signal), the transmitting side transmits the frame specified by the retransmission request again.
By such a communication procedure, accurate data transmission is realized even on a transmission path having an error.

[0007] However, when an error is confirmed again for a frame retransmitted by such a communication method, the retransmission operation is repeated for the same frame, resulting in an increase in transmission delay time and a decrease in communication speed. Therefore, it is necessary to limit the number of retransmissions.

This will be described with reference to an actual example. As a communication in which an increase in transmission delay time is a problem, there is a two-way video communication such as a videophone. Generally, the display delay time allowed in bidirectional video communication is about 300 msec. If the display delay is longer than this, smooth communication cannot be performed. However, the encoding / decoding processing of a moving image requires 1
Since a time of about 50 msec is required, a substantial time that can be devoted to retransmission of the video is about 150 msec. In addition, since the response delay time of the communication channel is about 100 msec, the actual number of retransmissions is about 1 to 2 times.

FIG. 2 is a functional block diagram showing a configuration of a moving picture communication apparatus using a communication method called an automatic retransmission method (ARQ). Note that, of the functional block groups shown in FIG. 2, upper functional block groups 201 to 207 correspond to the transmitting terminal, and lower functional block groups 208 to 212
Corresponds to the receiving terminal. Therefore, in the figure, part A is a downlink communication path, and part B is an uplink communication path.

The communication operation of the moving picture communication device shown in FIG. 2 will be described. The image data input from the terminal 201 is compressed by the moving image encoder 202 and then divided into units called frames. When there is no retransmission request, this output is input to the error detection encoder 205 via the selector 204, while the retransmission memory 2 is prepared for a future retransmission request.
03. The frame data input to the error detection encoder 205 is added with an error detection code such as a CRC code in the error detection encoder 205, and is further added with a frame number in a subsequent frame number addition unit 206. Output to the communication path.

On the receiving side, a frame number detector 208 and an error detector 209 check the received frame data for the frame number and the presence or absence of an error. If there is no error, the frame data is passed to the video decoder 211, and the process proceeds to the next frame. If there is an error, the receiving side retransmission controller 210 notifies the transmitting side retransmission controller 207 of the occurrence of the error and the frame number. Upon receiving this, the transmitting side retransmission controller 207
The same frame held in the retransmission memory 203 is controlled to be transmitted again.

The receiving-side retransmission controller 210 monitors the frame number from the frame number detector 208 and, if the same frame is erroneous a plurality of times, controls so as not to request retransmission more than the limited number of times.

With the above operation, relatively accurate data transmission can be realized without increasing the transmission delay time even on an erroneous transmission path.

However, if the number of retransmissions is limited, complete error correction cannot be performed.

Therefore, in the case of the above document, a majority decision is made after weighting each bit of a plurality of retransmission frames obtained as a result of error detection in accordance with the reception state (depending on the reception level, etc.) of each frame. Thus, the bit error rate is improved, and relatively reliable data can be obtained even when the number of retransmissions is limited.

[0016]

However, even with the communication method disclosed in the above document, there are the following problems.

That is, if the error is not corrected even if the frame is repeatedly retransmitted an allowed number of times, the data after the weighted majority decision in consideration of the reception level and the like is output to the subsequent circuit, but the reliability of this data is improved. Therefore, it is necessary to repeat retransmission several times, and there is a problem that it is difficult to effectively adapt to a bidirectional moving image communication application that requires real-time properties.

Further, in the prior art, redundant bits for error detection are always added for majority decision, so that
Under usage conditions in which the number of retransmissions is limited to about one or two, not only the reliability cannot be improved by majority decision, but also the reduction in communication speed due to redundant bits has been a problem.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a data communication method and apparatus which can reduce the communication speed less or improve the reliability as compared with the related art.

[0020]

[Means for Solving the Problems]

(A) In order to solve this problem, in the present invention, the presence or absence of an error included in communication data is detected on the receiving side, and if an error is detected, an automatic retransmission requesting the transmitting side for automatic retransmission of the communication data is performed. In a data communication method for performing data communication using a method, the following is performed. The same applies to the data communication device.

That is, when there is a limit to the number of retransmissions that can be requested, the transmitting side transmits the final retransmission data without attaching an error detection code.

The receiving side performs decoding processing on the last retransmitted data without performing error detection processing.

By using such a data communication method, the communication time occupied by retransmitted data can be shortened, and a reduction in communication speed can be suppressed. As a result, especially in the case of communication data that requires real-time transmission, it is possible to avoid deterioration in quality due to reduction in communication time.

(B) Further, in the present invention, an automatic retransmission method for detecting the presence or absence of an error included in communication data on the receiving side and requesting the transmitting side to automatically retransmit the communication data when an error is detected. In a data communication method for performing data communication using the following, the following is performed. The same applies to the data communication device.

That is, when there is a limit to the number of retransmissions that can be requested, the transmitting side transmits the final retransmission data with an error correction code instead of an error detection code.

The receiving side performs error correction processing on the final retransmitted data without performing error detection processing, and decodes the data after error correction.

By using such a data communication method, the reliability of the final retransmitted data can be improved,
Accordingly, the quality can be improved.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) First Embodiment A first embodiment of a data communication method and device according to the present invention will be described below with reference to the drawings, taking a moving image communication device as an example.

(A-1) Configuration of the First Embodiment A feature of the moving picture communication apparatus according to the first embodiment is that, when the number of retransmissions is limited, the last retransmission data (hereinafter referred to as “last retransmission data”). ) Is to prevent a reduction in communication speed by not adding redundant bits for error detection.

FIG. 1 shows a functional block configuration of a moving image communication apparatus having such a communication function. It should be noted that, among the functional block groups shown in FIG.
1 to 107 correspond to the transmitting terminal, and the lower functional block groups 108 to 112 correspond to the receiving terminal. Therefore, in the figure, part A is a downlink communication path, and part B is an uplink communication path.

First, the configuration of the transmitting terminal will be described.

The transmitting terminal has an image data input terminal 10
1, a video encoder 102, a retransmission memory 103, a selector 104, an error detection encoder 105, a frame number adder 106, and a transmission side retransmission controller 107.

Here, the moving image encoder 102 is a means for compressing image data input from the image data input terminal 101 and dividing the image data into frame units for error detection. The encoded frame unit data is output to the retransmission memory 103 and the selector 104.

The retransmission memory 103 is a memory provided in preparation for a retransmission request from the reception side, and is a means controlled by a control signal and a memory address given from the transmission side controller 107. Here, the retransmission memory 103
The frame unit data is held in a predetermined area corresponding to the transmission frame number, and is read from the area and output to the selector 104.

The selector 104 is connected to the transmission side retransmission controller 10.
7 is a means for outputting the selected frame unit data to the subsequent stage in accordance with the instruction of the control signal given from 7.

The error detection encoder 105 is means for executing an error detection encoding process under the control of the transmission side retransmission controller 107. Here, the error detection encoder 105
If the control signal from the transmission side retransmission controller 107 is an ON control signal, an error detection code such as a CRC code is generated and added to the input data. If the control signal is an OFF control signal, The data is output to the subsequent stage as it is.

The frame number adder 106 is a means for adding the frame number given from the transmission side retransmission controller 107 to the input data and transmitting the input data to the communication path.

The transmission side retransmission controller 107 is a means for managing transmission frames, and includes a counter for generating a frame number, a counter for counting the number of retransmission requests, a comparator for identifying the number of retransmissions, and other circuits. It is composed of Here, the count value of the counter that generates the frame number is incremented each time frame unit data is output from the video encoder 102.

The transmission-side retransmission controller 107 supplies a memory address and a control signal to the retransmission memory 103, an input selection signal to the selector 104, and the error detection encoder 10.
5, a signal indicating the final retransmission is sent to the frame number adder 1
06 is given a signal indicating the transmission frame number.

The retransmission controller 107 receives a retransmission request signal and its frame number from the retransmission controller 110 via the communication channel via a communication channel, and controls the retransmission operation based on the information.

Next, the configuration of the receiving terminal will be described.

The receiving terminal is provided with a frame number detector 10
8, an error detector 109, a receiving-side retransmission controller 110, a video decoder 111, and a decoded image output terminal 112.

Here, the frame number detector 108 is means for detecting the frame number from the received data received via the communication path, and sends the received data after deleting the frame number to the error detector 109 at the subsequent stage. Output. Note that the frame number detector 108 gives the detected frame number to the receiving-side retransmission controller 110.

The error detector 109 is the receiving side retransmission controller 1
Means for controlling in accordance with a control signal given from the control signal 10; when an on control signal is given, it is checked whether or not there is an error in the received data by using an error detection redundant bit included in the received data; When a signal is given, the received data from which the error detection redundant bits have been deleted is output as it is to the subsequent stage.

The receiving-side retransmission controller 110 is means for managing the transmission of a retransmission request, and includes a counter for counting the number of retransmission requests for the same frame, a comparator for identifying the number of retransmissions, and other circuits. It is configured. When the frame number is input from the frame number detector 108, the receiving side retransmission controller 110 has a function of checking the number of data retransmissions of the frame number from the count value of the counter. , Error detector 1
09 while giving an off control signal, otherwise
An ON control signal is provided to the error detector 109.

When the receiving side retransmission controller 110 detects that there is no error in the frame subjected to the error detection processing based on the input from the error detector 109, the counter for counting the number of retransmissions corresponding to the processed frame number. Operate to reset. Conversely, upon detecting the presence of an error in the error-detected frame by the input from the error detector 109, the receiving-side retransmission controller 110 increments a counter for counting the number of retransmissions corresponding to the processed frame number. Then, a retransmission request is transmitted to the communication path together with the frame number.

The moving image decoder 111 expands the received data that has been compression-encoded and restores the data before compression, and combines the data divided in frame units to decode the original image data. It has become.

(A-2) Transmission / Reception Operation Next, the transmission / reception operation of the video communication apparatus according to the first embodiment will be described.

(A) Transmission operation (a-1) Operation when no retransmission request is input First, the operation of the transmitting terminal when no retransmission request is input will be described. At this time, the transmission side retransmission controller 107 processes the value of the internal counter as a frame number. That is, a memory address and a control signal indicating an area corresponding to the counter value are sent to the retransmission memory 103, and the counter value is sent to the frame number adder 106, and the above-described processing is performed on each.

Since no retransmission request has been input, a signal for selecting the output of the moving picture encoder 102 is given to the selector 104, and an ON control signal is given to the error detection encoder 105. That is, when there is no retransmission request, new encoded data output from the video encoder 102 is
After the error detection coding process, the frame number is added to the frame number and the frame number is output.

(A-2) Operation when retransmission request is input Next, the operation of the transmitting terminal when the retransmission request and the frame number of the frame requested to be retransmitted are input will be described. At this time, transmission-side retransmission controller 107 performs a control operation such that data corresponding to the frame number for which retransmission has been requested from reception-side retransmission controller 110 is transmitted.

Here, the frame requested to be retransmitted is a frame transmitted in the past, and is held in the retransmission memory 103. Therefore, the retransmission memory 103 is provided with a memory address and a control signal indicating a region corresponding to the frame number for which retransmission has been requested from the transmission side retransmission controller 107.
Similarly, a signal for selecting the retransmission memory 103 is supplied to the selector 104 from the transmission side retransmission controller 107. Further, the frame number is supplied from the transmission side retransmission controller 107 to the frame number adder 106.

By the way, the transmission side retransmission controller 107 determines whether or not the count value of the counter for counting the number of retransmissions for the same frame (the number of retransmission requests) matches the maximum number of retransmissions, using a comparator. If the count value does not match the maximum number of retransmissions, an ON control signal is output to the error detection encoder 105 because retransmission may be performed again. On the other hand, if the count value matches the maximum number of retransmissions, no retransmission is performed thereafter, so that an off control signal is output to error detection encoder 105.

That is, if there is a retransmission request and it is not the last retransmission request, data corresponding to the retransmission request stored in retransmission memory 103 is error-detection coded, and the frame number of the retransmission request is added. Output to the communication path. Conversely, if there is a retransmission request and it is the last retransmission request, the data corresponding to the retransmission request stored in the retransmission memory 103 is output to the communication path by simply adding the frame number as it is.

(B) Reception operation (b-1) Operation when received data is not final retransmission data First, operation when reception data is not final retransmission data will be described. At this time, the data subjected to the above processing is input to the frame number detector 108 from the communication channel.
The frame number detector 108 detects the frame number from the received data and transmits it to the receiving side retransmission controller 110. Also, the received data from which the frame number has been deleted is sent to the error detector 109.

Here, upon receiving the frame number from the frame number detector 108, the receiving side retransmission controller 110 checks the number of retransmissions of the data of the frame number with a counter for counting the number of retransmission requests. Here, since it is not the maximum number of retransmissions, an ON control signal is output to the error detector 109, and the error detection operation of the error detector 109 is executed.

The error detector 109 checks whether there is an error in the received data using the error detection redundant bit included in the received data, and transmits the result to the retransmission controller 110 on the receiving side. If there is no error, the received data from which the error detection redundant bits have been deleted is sent to the video decoder 111.

If no error is detected, the receiving side retransmission controller 110 resets the count value of the counter corresponding to the processing frame number, and if an error is detected, counts the number of retransmissions of the frame. In addition to incrementing the counter, the frame number and the retransmission request are output to the communication path.

(B-2) Operation when received data is final retransmission data Whether or not received data is final retransmission data is recognized by the retransmission controller 110 on the receiving side. Receiving side retransmission controller 110
When a frame number is input from the frame number detector 108, the number of retransmissions of data of the frame number is checked by a counter for counting the number of retransmission requests. Here, since the operation is performed when the received data is the final retransmission data, it is determined that the count value matches the maximum number of retransmissions.

Then, reception side retransmission controller 110 gives an off control signal before error detection processing in error detector 109 is started, and prohibits the processing. This allows
The error detector 109 operates to output the received data as it is to the image decoder 111 at the subsequent stage (the error detection redundant bits are not originally added, so the deletion processing is not performed). As a result, the received data is expanded in the video decoder 111 and output as video data.

(A-3) Effect of First Embodiment The effect of the first embodiment will be described with reference to FIG. In this figure, hatched portions represent redundant bits for error detection. Also, this figure shows a case where the maximum number of retransmissions is limited to one, and there is an error in the transmission of "frameN-1" and "frameN". In this example, "
The error of frameN "is not corrected by retransmission.

When the receiving terminal detects an error by receiving up to the redundant bits of “frameN−1”, it sends out a retransmission request signal (ARQ) to the transmitting side.

In the case of the conventional example ((a) in the upper part of the figure),
The transmitting terminal that has received the retransmission request signal (ARQ) adds an error detection code to "frameN-1" which is the final retransmission data, and executes retransmission.

However, when the retransmission request signal (ARQ) is received, since “frameN + 1” is being transmitted, “frN”
ameN-1 '"is transmitted after the transmission of" frameN + 1 "is completed.

One of the receiving terminals has “frameN-
When 1 '"is received, error detection is performed, and after confirming that there is no error, the data is sent to the subsequent stage. Similarly, when"frameN'"is retransmitted, error detection is performed. In the case of "", an error is detected again. However, due to the limitation of the number of retransmissions for maintaining real-time performance, data is passed to a subsequent process together with a signal for identifying an error.

On the other hand, in the case of the first embodiment, redundant bits for error detection are not added to the final retransmission data. Therefore, the “fram” retransmitted by the receiving terminal is
When eN-1 '"is received, the data is passed to the subsequent processing without performing the error detection processing. Also,"frameN'"is processed in the same manner. This error can be detected because an unknown code appears in the process of decoding the moving image, etc. That is, it does not matter if the final retransmission data does not include the redundant bit for error detection. .

In the prior art, redundant bits are always added to transmission data. However, in the first embodiment, since redundant bits are not added to the final retransmission data, the retransmission data is transmitted through the communication path. Occupation time can be shortened accordingly. That is, a decrease in communication speed can be suppressed. In particular, in a moving image communication application, a decrease in communication speed is reduced, so that image quality can be improved.

(B) Second Embodiment A second embodiment of a data communication method and apparatus according to the present invention will be described below with reference to the drawings, taking a moving image communication apparatus as an example.

(B-1) Configuration of the Second Embodiment A feature of the moving picture communication apparatus according to the second embodiment is that an error correction redundant bit is added to the final retransmission data instead of an error detection redundant bit. The point is to improve the reliability of data.

FIG. 4 shows a functional block configuration of a moving image communication apparatus having such a communication function. In the case of FIG.
The same and corresponding parts as those in FIG. 1 are denoted by the same reference numerals. The upper functional block group corresponds to the transmitting terminal, and the lower functional block group corresponds to the receiving terminal.

As can be seen from FIG. 4 and FIG.
The moving picture communication apparatus according to the embodiment differs from the first embodiment in that an error correction encoder 401, a selector 402, an error corrector 403, and a selector 404 are newly provided.

Here, the error correction encoder 401 provided in the transmitting terminal is a circuit provided for adding an error correction redundant bit to the last retransmitted data as described above, The converter 105 is provided in parallel.

The selector 402 selects the error correction encoder 40
1 and an output of the error detection encoder 105 are provided to output to the frame number adder 106, and are switched and controlled by the transmission side retransmission controller 107 '. Has become.

On the other hand, the error corrector 403 provided in the receiving terminal is a circuit provided for correcting the error when the received data is the final retransmitted data, and is used for processing other received data. Error detector 10 provided
9 are provided in parallel.

The selector 404 is a circuit provided to output one of the output of the error corrector 403 and the output of the error detector 109 to the video decoder 111.
The switching is controlled by the receiving-side retransmission controller 110 '.

In this embodiment, the switching of the processing operation for the final retransmission data is performed by the selectors 402 and 40.
4, the on / off control signal input to the error detection encoder 105 and the error detector 109 in the case of the first embodiment is unnecessary.

(B-2) Transmission / Reception Operation Next, the transmission / reception operation of the moving picture communication apparatus according to the second embodiment will be described. Note that the basic operation in the second embodiment is the same as that in the first embodiment, and thus the description will be focused on the changed portions. That is, only the transmission / reception operation for the final retransmission data will be described, and the description of the operation other than the transmission / reception of the final retransmission data will be omitted.

FIG. 5 shows transmission / reception signals in the case of the second embodiment. In the figure, hatched portions indicate redundant bits for error detection, and black portions indicate redundant bits for error correction. Also, in this figure, it is assumed that the maximum number of retransmissions is limited to one, and "frameN-1" and "fra
It is assumed that there was an error in the transmission of "meN".

When the retransmission request is notified from the reception terminal, the transmission retransmission controller 107 'of the transmission terminal checks the number of retransmission requests of the frame, and determines whether or not this is the last retransmission request. I do.

Here, if it is determined that the request is the final retransmission request, the selector 402
A control signal is output so as to select the output No. 1. As a result, a retransmission frame to which an error correction code has been added is output to the communication path.

On the other hand, in the receiving terminal, the receiving-side retransmission controller 110 ′ monitors the frame number given from the frame number detector 108 to determine whether or not the current reception data is the last retransmission data.

Here, when it is determined that the data is final retransmission data transmitted in response to the final retransmission request, a control signal is output to selector 404 so as to select the output of error corrector 403. Thereby, the final retransmission data transmitted via the communication path after being error-correction-coded at the transmitting terminal is error-corrected at the receiving terminal,
This will be provided to the video decoder 111 ′.

(B-3) Effect of the Second Embodiment As described above, according to the second embodiment, the final retransmission data is subjected to error correction coding, so that a small error can be corrected. As a result, the reliability of the final retransmission data can be improved.

For example, in the case of the first embodiment, the error of "frameN" could not be corrected by repeating the retransmission operation, but in the case of the second embodiment,
By performing error correction coding at the time of final retransmission, "fram"
eN "can be transmitted without error.

(C) Third Embodiment A third embodiment of a data communication method and apparatus according to the present invention will be described below with reference to the drawings, taking a moving image communication apparatus as an example.

(C-1) Configuration of Third Embodiment The moving picture communication apparatus according to the third embodiment further advances the function of the second embodiment, and includes an error added to the final retransmission data. The correction code is characterized by obtaining more reliable data by attempting to correct errors not only in the last retransmitted data but also in past erroneous data.

FIG. 6 shows a functional block configuration of a receiving terminal of a moving image communication apparatus having such a communication function. However, in the third embodiment, since the same terminal as the transmitting terminal of the moving picture communication device according to the second embodiment is used as the transmitting terminal, it is omitted in FIG. FIG.
In this case, the same and corresponding parts as those in FIG. 4 are indicated by the same and corresponding reference numerals.

As can be seen from FIG. 6 and FIG.
The moving image communication apparatus according to the second embodiment has the same configuration as the moving image communication apparatus according to the second embodiment except that a memory 601 and a selector 602 are added to a receiving terminal.

Here, the memory 601 is a storage means for storing data in which an error is detected by the error detector 109 among the past received data, and the selector 602 reads out the data from the memory 601. It is provided to output either one of the received data and the data received from the communication path to a subsequent circuit.

(C-2) Transmission / Reception Operation Next, the transmission / reception operation of the moving picture communication apparatus according to the third embodiment will be described with reference to FIG.

Note that the error correction code cannot have sufficient correction capability when the number of redundant bits is small. For this reason, errors may not be corrected by the error correction processing. Even if an error remains, this is not always recognized as having an error.

Therefore, in the third embodiment,
The final retransmission data is error-corrected by the error corrector 403 (see FIG. 7).
After the process 1), the result is input to the error detector 109 to check for an error (process 2 in FIG. 7). When an error is detected in this process, erroneous data of the same frame received in the past is read from the memory 601, error correction is performed (process 3 in FIG. 7), and error detection is performed again (FIG. 7). FIG. 7 processing 4).

Specifically, the operation is as follows. First, a case where received data other than the last retransmission data is received will be described. At this time, the frame number detector 108
Is supplied to an error detector 604 via a selector 602, and it is determined whether or not an error exists in the received data.

Here, if no error is detected, the received data is output to the video decoder 111 via the selector 404, but if an error is detected, the received data is output via the selector 404. Stored in the memory 601,
At the same time, a retransmission request is output from the receiving side retransmission controller 110 ″ to the transmitting side terminal.

However, even if the retransmission request is repeated, error-free data cannot be received. As a result, when the final retransmission data to which the error correction code is added is received, the received data is transmitted to the error corrector 403. And performs error correction processing. However, even if such an error correction process is performed, it is unknown whether or not the correction result contains an error.

Therefore, the correction result, that is, the selector 40
4 is output to the selector 60 via the memory 601 again.
2, the presence or absence of an error is detected. At this time, the receiving side retransmission controller 110 ″ is
2 outputs a control signal to select the output of the memory 601.

As a result, the output of the error corrector 403 is input to the error detector 109, and it is confirmed whether the error contained in the received data has been corrected.

Here, when an error is detected again, the receiving side retransmission controller 110 ″ reads out the data of the same frame held in the memory 601 because the past error was detected, and Perform error correction.

Subsequently, this is fed back to the error detector 109 via the selector 602, and the error detection processing is executed again. Here, if an error is detected again, the memory 60
Another data is read out from 1 and the same processing is repeated.
It is assumed that the error correction redundant bits and the error detection redundant bits for the data of the same frame number are held in the error corrector 403 and the error detector 109.

If error-free data is obtained by repetition, the data is supplied to the moving picture decoder 111, and the error correction processing is completed.

On the other hand, if an error remains even after performing the above-described processing for all data, the reception data having the error is supplied to the video decoder 111 together with the identification signal indicating the error. The operation is performed.

(C-3) Effect of Third Embodiment As described above, according to the third embodiment, the error detection code added to the received data retransmitted due to the detection of the error and the error detection code Apply error correction code (for error correction code, only for the last retransmission data, for error detection code, at other times) to the same data transmitted at different timings, and apply error correction to the received data after error correction. Is detected, and if there is no error, the decoding operation is performed using the error, so that more reliable data can be obtained.

(D) Other Embodiments In the above embodiment, the case where the present invention is applied to a moving image communication device used for moving image data communication has been described. Other image data may be used, and audio data and binary data may be used.

[0104]

As described above, according to the present invention, in the data communication method and apparatus for performing data communication using the automatic retransmission method, when the number of retransmissions that can be requested is limited,
The transmitting side transmits the final retransmitted data without attaching an error detection code, and the receiving side occupies the retransmitted data by executing the decoding process without performing the error detection process on the final retransmitted data. Communication time can be shortened,
A reduction in communication speed can be suppressed. As a result, especially in the case of communication data that requires real-time transmission, it is possible to avoid deterioration in quality due to reduction in communication time.

As described above, according to the present invention, in the data communication method and apparatus for performing data communication using the automatic retransmission method, if there is a limit to the number of retransmissions that can be requested, Data is transmitted with an error correction code instead of an error detection code, and the receiving side performs error correction processing on the final retransmitted data without performing error detection processing, and decodes the data after error correction. By performing the processing, the reliability of the final retransmission data can be improved. Thereby, the quality can be improved accordingly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a data communication device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional device.

FIG. 3 is a diagram illustrating a transmission / reception operation of the data communication device according to the first embodiment.

FIG. 4 is a block diagram showing a second embodiment of the data communication device according to the present invention.

FIG. 5 is a diagram showing a transmission / reception operation of the data communication device according to the second embodiment.

FIG. 6 is a block diagram showing a third embodiment of the data communication device according to the present invention.

FIG. 7 is a diagram illustrating a transmission / reception operation of a data communication device according to a third embodiment.

[Explanation of symbols]

101: image data input terminal, 102: moving image encoder, 103: retransmission memory, 104: selector, 105 ...
Error detection encoder, 106 ... frame number adder, 10
7, 107 ': transmission side retransmission controller, 108: frame number detector, 109: error detector, 110, 110', 1
10 ″: Retransmission controller on the receiving side, 111: Video decoder, 1
12: decoded image output terminal, 401: error correction encoder,
402, 404, 602: selector, 403: error corrector, 601: memory.

Claims (10)

[Claims] 1. A receiving side detects the presence / absence of an error included in communication data, and when an error is detected, performs data communication using an automatic retransmission method for requesting an automatic retransmission of the communication data to a transmission side. In the data communication method, if there is a limit on the number of retransmissions that can be requested, the transmitting side transmits the final retransmission data without attaching an error detection code. 2. The communication system according to claim 2, wherein the receiving side detects the presence or absence of an error included in the communication data, and when the error is detected, performs data communication using an automatic retransmission method that requests the transmission side to automatically retransmit the communication data. In the data communication method, if there is a limit to the number of retransmissions that can be requested, the receiving side performs decoding processing on final retransmission data without performing error detection processing. 3. The receiving side detects the presence or absence of an error included in the communication data, and if an error is detected, performs data communication using an automatic retransmission method that requests the transmission side to automatically retransmit the communication data. In the data communication method, if there is a limit to the number of retransmissions that can be requested, the transmitting side transmits the final retransmission data with an error correction code instead of an error detection code. 4. The receiving side detects the presence or absence of an error included in the communication data, and if an error is detected, performs data communication using an automatic retransmission method that requests the transmission side to automatically retransmit the communication data. If there is a limit to the number of retransmissions that can be requested in the data communication method, the receiving side must perform error correction processing on the final retransmitted data without performing error detection processing, and decode the error-corrected data. Characteristic data communication method. 5. The data communication method according to claim 4, wherein when an error is detected in the final retransmitted data after error correction,
The error correction process is performed again on the same data that was previously received and held in the storage unit,
If no error is detected in the corrected data, a data communication method characterized by decoding the error correction result of the previously received data instead of the final retransmission data. 6. A method for detecting the presence or absence of an error included in communication data on a receiving side, and, when an error is detected, transmitting data using an automatic retransmission method for requesting an automatic retransmission of the communication data to a transmitting side. In the communication apparatus, on the transmitting side, an error detection coding means for adding an error detection code to the transmission data and outputting the same, a retransmission memory for holding the transmission data in preparation for a retransmission request, and a retransmission number at which the current retransmission data can be requested. Retransmission control means for determining whether or not the final retransmission data when there is a restriction, and controlling the error detection coding process not to be performed on the final retransmission data when the data is the final retransmission data. Data communication device. 7. A method for detecting the presence or absence of an error included in communication data on a receiving side, and, when an error is detected, data for communicating data using an automatic retransmission method for requesting an automatic retransmission of the communication data to a transmitting side. In the communication device, on the receiving side, error detecting means for detecting an error in the received data, and when an error is detected from the detection result in the error detecting means, retransmission requesting means for requesting the transmitting side to retransmit the corresponding data. If the current received data is the last retransmitted data when there is a limit to the number of retransmissions that can be requested, it is determined before the error detection processing by the error detection means, and if it is determined to be the last retransmission data, the error detection processing is performed. A data communication device comprising: retransmission control means for performing control so as not to be executed. 8. A method for detecting the presence or absence of an error included in communication data on a receiving side, and, when an error is detected, a data for communicating data using an automatic retransmission method for requesting an automatic retransmission of the communication data to a transmission side In the communication apparatus, on the transmitting side, an error detection coding means for adding an error detection code to the transmission data and outputting the same, a retransmission memory for holding the transmission data in preparation for a retransmission request, and a retransmission number at which the current retransmission data can be requested. Retransmission control means for judging whether or not the data is the last retransmission data when there is a limit, and controlling the error detection coding process not to be performed on the final retransmission data when the data is the last retransmission data; and And an error correction coding means for adding an error correction code to the final retransmitted data that is not executed and outputting the result. 9. A method for detecting presence / absence of an error included in communication data on a receiving side, and, when an error is detected, a data for communicating data using an automatic retransmission method for requesting an automatic retransmission of the communication data to a transmitting side. In the communication device, on the receiving side, error detecting means for detecting an error in the received data, and when an error is detected from the detection result in the error detecting means, retransmission requesting means for requesting the transmitting side to retransmit the corresponding data. If the current received data is the last retransmitted data when there is a limit to the number of retransmissions that can be requested, it is determined before the error detection processing by the error detection means, and if it is determined to be the last retransmission data, the error detection processing is performed. Retransmission control means for controlling not to be executed, and an error correction means for executing error correction encoding processing on the final retransmission data for which the error detection encoding processing is not executed. Data communication apparatus, characterized in that it comprises and. 10. The data communication apparatus according to claim 9, wherein, when an error is detected in the final retransmitted data after error correction, the retransmission control unit determines whether the same data is the data received earlier, The error correction processing is performed again on the data held in the data storage memory, and if no error is detected in the corrected data, the error is obtained from the data read from the error data storage memory in place of the final retransmitted data. A data communication device for controlling decoding of the error-corrected data.