JPH09224018A - Automatic retransmission transmission method, transmitter and receiver thereof - Google Patents

Abstract

(57) Abstract: A dictionary is transmitted between a transmission side and a reception side when efficient encoding is performed while updating the dictionary and an automatic retransmission transmission system is used, and errors frequently occur and cannot be detected. Eliminate the disagreement. When no error is detected on the receiving side, a codeword δr (k) (kth frame) newly added in the frame is transmitted to the transmitting side, and when the transmitting side receives the codeword δr (k). , New codeword δs (k) in the corresponding frame that was held
If the values do not match, the coding dictionary is set to the initial state Ds (o), and the coding dictionary is used to code again from the kth frame and retransmit, and an initialization notification is transmitted. Upon receiving the initialization notification, the receiving side changes the decryption dictionary to the initial state Dr (o) and decrypts it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compresses and encodes input data using a coding dictionary on the transmitting side, and gives a new code word to a character in the input data which is not in the coding dictionary to give a coding dictionary. While transmitting the coded data and the updated codeword in frame units while updating, the receiving side determines whether the received frame is correctly received.If it is not received correctly, the retransmission request is notified to the transmitting side, and If received, the encoded data of the received frame is decoded using the decoding dictionary, the decoding dictionary is updated using the received update codeword, and at least the retransmission request is received by the transmitting side, at least The present invention relates to an automatic retransmission transmission method for retransmitting coded data of an erroneous frame on the reception side, a transmission device thereof, and a reception device.

[0002]

2. Description of the Related Art V.V. transmitted and received between data modems in a public telephone network. The 42 frame configuration is shown in FIG. 7A. In the receiving modem (Receiver), which sequentially includes a 9-bit start flag, an address field, a control field, and an information field, an 18-bit frame check sequence and a 9-bit end flag, a frame check sequence (FCS) ), An error-free communication path is realized by performing error detection and making a reception notification or a retransmission request to the transmitting modem (Sender) using the backward channel. In such an error-free communication path, V. FC
And V. V.34 used in a data modem compliant with the H.34 standard. With a data compression function such as 42 bis, it is possible to obtain throughput several times higher than the transmission rate. V. Four
2bis is the ZLW method (Ziv-lempel-Welc
This is a data compression method using a dictionary called the h method).
In this method, encoding and decoding are performed by referring to the entry words of the dictionary. At the same time, efficient data compression can be realized by increasing the number of entry words of the dictionary. This encoding / decoding method is generally called ZL method or LZ method, and the same initial dictionary is provided on the transmitting side and the receiving side, and the transmitting side refers to the encoding dictionary to perform encoding. At the same time, a new code word is given to a character that does not exist in the dictionary to update the dictionary, and the decoding dictionary on the receiving side is also updated accordingly, so that both dictionaries are always in the same state and efficient compression transmission is performed. The encoding, decoding, dictionary updating algorithms and the like are described in, for example, "Introduction to Document Data Compression Algorithms" by Tomohiko Uematsu, CQ Publishing, October 15, 1994, pages 174-208.

In FIG. 7B, from Sender to Receive
r shown in FIG. 42 frames are Stop-an
4 shows a change in the dictionary state when d-Wait, that is, when a frame is transmitted by using a retransmission control method that waits for a response from the receiving side every time the frame is transmitted. The frame is being transmitted as indicated by the solid line. A code word compression-coded by a dictionary is stored in each frame having a number. By sending such a compression codeword, the sender's dictionary (encoding dictionary) is Ds (0), Ds (1), ..., Ds (k-1), and Receive.
The er dictionary (decoding dictionary) is Dr (0), Dr (1), ..., Dr.
Updated with (k-1). Focusing on the k-th frame, the sender and the receiver use the dictionaries Ds (k-1) and Dr (k-1) having the same contents to encode and decode the k-th frame. Is maintained even when the frame is retransmitted. In FIG. 7B, Receiver
The kth frame indicated by the diagonal line is a retransmission request because the frame check sequence (FCS) has determined that the frame is an error frame, and the sender has retransmitted the data. Since it is (encoded data), encoding is not necessary at the time of retransmission and dictionary update is not performed. Therefore, the dictionary states Ds (k-1) and Dr (k-1) at the time of the first transmission of the kth frame are held. When error detection is performed accurately in this way, Sende
The identities of both the r and Receiver dictionaries are preserved and correct decoding is guaranteed.

FIG. 8A shows an example of a conventional Sender device configuration. After the input data is temporarily stored in the input buffer 11, the encoder 12 refers to the encoding dictionary built therein, and if it can be referred, the codeword (compressed codeword) is transmitted to the transmission buffer 13 and transmitted at any time. Ready to go. Characters that cannot refer to the dictionary by the input data are newly registered in the encoding dictionary, and the contents of the encoding dictionary are updated. The signal from the Receiver is received by the ARQ frame control device 14, and further the error detection device 15
If there is no error in the reception of the signal and the signal is a retransmission request, the switching device 16 is controlled by this, the switch 17 is switched to the contact a side, and the retransmission buffer 1
On the contrary, if the coded data stored in 8 is a reception signal or a reception notification, the switching device 16 is controlled and the switch 17
Of the encoded data stored in the transmission buffer 13 after being turned to the contact n side, respectively.
Is sent to the Receiver via the. The ARQ frame control devices 14 and 19 establish frame synchronization and ARQ.
After exchanging control information necessary for control, a compression code is constructed in an ARQ frame, and then they are transmitted and received. The data transmitted from the ARQ frame control device 19 is always accumulated in the retransmission buffer 18 at the same time as the transmission. R
If the signal from the receiver is judged to be erroneous, it is ignored and the transmission process is restarted from the time when the retransmission request and the reception notification signal can be correctly received (there is no error as a result of error detection).

FIG. 8B shows an example of the configuration of a conventional Receiver. Send with ARQ frame controller 21
The error detection device 22 performs error detection on the data received from r. As a result, if there is an error, a resend request is sent, and if no error is detected, a reception notification is sent to the sender by the ARQ frame control device 23. As a result of the error detection, if it is determined that there is no error, the received data is sent to the receiving buffer 24, and further, the decoder 25 refers to the dictionary (decoding dictionary) built in the receiving data and transmits the original data from the compression codeword. The data is decoded and stored in the output buffer 26.

[0006]

However, as compared with a wired communication path such as a public telephone network, in a wireless communication path in which errors frequently occur, the effect of error non-detection depending on an error pattern cannot be ignored. As shown in FIG. 9A corresponding to FIG. 7B, if the k-th frame (indicated by diagonal lines) sent from the Sender is received by the Receiver and there are too many errors, error non-detection occurs.
Since the cever does not know that the k-th frame is an error frame, it performs a decoding process in the same manner as a correct frame and sends a reception notification to the sender. As a result, the dictionary Dr (k) updated by Receiver is Send.
The contents are different from the dictionary Ds (k) updated to the kth frame by er, and it becomes difficult for Receiver to correctly decode the (k + 1) th frame and thereafter.

A detailed example of such a dictionary mismatch is shown in FIG. 9B.
Shown in In the sender, the character ab is newly registered in the codeword 001011011 in the (k−1) th frame, and further, the characters (a, ..., Dec) are registered as new codewords and sent to the Receiver. Correspondence tables of the codewords and characters that have been updated and are owned by Sender and Receiver match, that is, the dictionaries match, and the dictionary is expanded by registering the dictionary thereafter to improve the coding efficiency. Since the contents of both dictionaries are kept the same, the newly registered codeword 001 is not detected in the kth frame due to the above-mentioned error non-detection.
Even though 100101 was sent, 001000
When it is received as 11, since it is a code word corresponding to the already registered map in the Receiver, the decoding dictionary Dr (k) in the kth frame is the coding dictionary Ds (k in the kth frame. ) Will be different content. As a result, it cannot be guaranteed that the k-th frame and subsequent frames are correctly decoded.

[0008]

According to the automatic retransmission transmission method of the present invention, input data is compression-encoded on the transmitting side using an encoding dictionary, and characters that are not in the encoding dictionary in the input data are compressed. Then, the coded data and the updated codeword are transmitted frame by frame while a new codeword is given to update the coding dictionary, and the receiving side determines whether or not the received frame is correctly received. If not, it sends a resend request to the sender, and if it is received correctly, it decodes the coded data of the received frame using the decoding dictionary and updates the decoding dictionary using the received codeword. , When the sender receives the retransmission request,
At least in the automatic retransmission transmission method of retransmitting coded data of an erroneous frame on the receiving side, when it is determined that the receiving side is correctly received, the update code word in the received frame is transmitted to the transmitting side, On the transmitting side, the update code word from the receiving side is compared with the corresponding update code word on the transmitting side, and if the two do not match, the coding dictionary in the coding dictionary in the frame preceding the mismatched transmission frame is used. And the data of the inconsistent transmission frame is encoded by using the dictionary, the encoded data and the dictionary change notification are transmitted, and the receiving side receives the dictionary change notification, and decodes accordingly. The encoding dictionary is changed and the encoded data of the received frame is decoded using the dictionary.

According to the transmission device of the present invention, the input data from the input buffer is input to the encoder, compression encoded using the encoding dictionary, and the encoded data is transmitted frame by frame. When a new codeword is given to a character string that is not in the encoding dictionary to update the encoding dictionary, a codeword corresponding to the character string in the dictionary is transmitted in the same frame, and a resend request is received. In an automatic retransmission transmission transmitter that retransmits the encoded data of the corresponding frame in the encoding buffer, an input data buffer that stores the input data for at least 1 RTF, and a code that stores a codeword generated by encoding A word buffer, a comparator that compares the received codeword with the codeword of the corresponding frame in the additional dictionary buffer,
If the comparison result of the comparator does not match, the input buffer is switched to the input data buffer to supply data to the encoder, and the dictionary used for encoding of the encoder is predetermined from the mismatch detection frame. And a means for notifying the change.

According to the receiving apparatus of the third aspect of the invention, error detection is performed for each received frame, and if there is no error, the received coded data is decoded using the decoding dictionary, the dictionary is updated, and the received frame is converted into a received frame. When an error is detected, the receiving device of the automatic retransmission transmission that transmits a retransmission request for the frame to the transmitting side is provided with means for returning the decoding dictionary to the initial state when the dictionary change notification is received. Characterize.

According to the receiving apparatus of the fourth aspect of the invention, error detection is performed for each received frame, and if there is no error, the received coded data is decoded using the decoding dictionary, the dictionary is updated, and the received frame is updated. When an error is detected, a receiving device for automatic retransmission transmission that transmits a retransmission request for the frame to the transmitting side receives an additional dictionary buffer in which the received codeword is stored and a dictionary change notification. And a means for changing the decoding dictionary to a decoding dictionary in a previous frame which is predetermined by using the contents of the additional dictionary buffer.

[0012]

FIG. 1A shows a transmission method of the present invention in S
The time chart in the Example applied to the top-and-Wait retransmission control system is shown, and the same code | symbol is attached | subjected to the part corresponding to FIG. 9A. Focusing on the shaded kth frame, the frame is encoded by Sender, and the new codeword δs (k) obtained as a result is at least 1 RTF.
Between (round trip frames), that is, Sender
A new code obtained by decoding with the reception notification when it is held in the dictionary buffer for the time from the start of transmission by the receiver until the reception notification or resend request by the Receiver is notified to the Sender, and when an error cannot be detected by the Receiver. The word δr (k) is transmitted to the sender by the backward channel (thick line in the figure) in the retransmission control. In Sender, δr (k) received in the backward channel and δ in the Sender's dictionary buffer
s (k) is compared, and when they are different, it is considered that no error has been detected (there was an error but could not be detected), and the Sender
In, the dictionary is initialized to the state of the dictionary before the error non-detection frame, that is, Ds (k) is copied to the initial dictionary Ds (0). Subsequently, the unencoded data of the k-th frame is re-encoded using the initialized dictionary and transmitted to the transmission buffer. This re-encoded data is the Receiver
Notify that the dictionary has been initialized when sending to. The underlined Ds (0) in FIG. 1A indicates the copied dictionary. Rece
Upon receiving the initialization notification signal, the server copies Dr (k) to the initial dictionary Ds (k), and the dictionary is initialized. The update of the initialized dictionary starts at the time of coding the kth frame. As a result of the comparison between δr (k) sent in the backward channel and δs (k) in the sender, if both match, the dictionary is not initialized and normal transmission control of the next frame is performed.

For reference, FIG. 1B shows a state in which newly registered codewords are compared frame by frame. In Sender, δs (k-1) in the (k-1) th frame and received δr (k-1) match, but the comparison of δs (k) in the kth frame with received δr (k) results in the kth frame. It can be seen that the codewords obtained by the encoding (the underlined portions) do not match. When this discrepancy is detected,
As described above, the dictionary is initialized, the input data of the k-th frame is encoded by this dictionary and transmitted, and the initialization of the dictionary is notified.

FIG. 2 shows the transmission according to the present invention.
An example of the device configuration of r) is shown. In FIG. 2, parts corresponding to those in FIG. 8A are designated by the same reference numerals. In this embodiment, the input data input from the input buffer 11 to the encoder 12 is temporarily stored in the input data buffer 31.
Each data in 1 and 31 can be switched by the switch 32 and supplied to the encoder 12. The initial state dictionary initially stored in the dictionary memory in the encoder 12 is stored in the initial dictionary buffer 33, and the new code word created by the encoding and added to the dictionary in the encoder 12 is It is also stored in the additional dictionary buffer. Further Recei
code word sent from the server and additional dictionary buffer 34
The comparison with the codeword of the corresponding ARQ frame in
Done in

If an error is detected by the error detector 15 with respect to the signal from the Receiver, and as a result, no error is detected and the content is a resend request, the changeover switch 17 moves the changeover switch 17 to the contact a side for resending. The encoded data in the buffer 18 is sent to the ARQ frame controller 14. On the contrary, when the content of the signal from the Receiver is the reception notification, first, the changeover switch 17 of the changeover device 16 changes the contact n
Side, then the Receipt by the backward channel
The code word δr (k) sent from the ver and the code word δs (k) sent in the corresponding ARQ frame held in the additional dictionary buffer 34 are compared by the comparator 35. If the comparison result does not match, the changeover switch 3 is used by the changeover device 16.
2 is connected to the input data buffer 31 side, and the buffer 3
The data of the kARQ frame in 1 is transmitted to the encoder 12. Further, the initial state dictionary Ds (0) stored in the buffer 33 before that is copied to the dictionary in the encoder 12 to perform dictionary recovery. Therefore, the data of the kARQ frame is encoded by the initial state dictionary Ds (0) and further transmitted by the ARQ frame controller 19. Δ in the comparator 35
If r (k) and δs (k) match, the state of the dictionary in the encoder 12 is held, and the switch 17 causes the switch 17 to the transmission buffer 13 side and the switch 32 to the input buffer 11 side. In this state, the data in the transmission buffer 13 is sent to the ARQ frame controller 19.

FIG. 3A shows a receiving device Rece according to the present invention.
An example of the configuration of the server is shown. In FIG. 3A, parts corresponding to those in FIG. 8B are given the same reference numerals. The initial state Dr (o) in the dictionary in the decoder 25 is stored in the initial state dictionary buffer 41, and a new code word sent by Sender is added to the dictionary in the decoder 25 and added to the dictionary. As the update is made, the new codeword δr (k) is added to the additional dictionary buffer 4
It is also stored in 2. Further, the error detector 22 performs error detection on the signal received from the Sender, and when an error is detected, the received signal is supplied to the reception buffer 24 and also to the notification detector 33 to detect the notification. Bowl 3
If there is a dictionary change notification in the signal, 3 detects this and sets the decoding dictionary to the initial state.

When an error is detected in the ARQ frame by the error detection processing by the error detector 22, a retransmission request signal is sent to the Sender via the ARQ controller 23, and the code word δr (k in the buffer 42. ) Is not sent. If no error is detected by the error detector 22,
The new codeword δr (k) of the ARQ frame decoded by the decoder 25 and stored in the buffer 42 is Sen.
controlled to send to der. See also Sender
Therefore, when the dictionary change notification signal, in this example, the initialization notification signal is received, the initial state dictionary Dr (0) accumulated and placed in the buffer 41 by the notification detector 43 becomes the decoding dictionary in the decoder 25. It is copied and the dictionary is restored.

In the above, when the received δr (k) and the δs (k) in the buffer do not match at the sender, the encoding dictionary and the decoding dictionary are changed to the initial state dictionaries. The dictionary state in any of the frames before the detected ARQ frame k may be set. This embodiment will be described with reference to FIG. To recover the dictionary, set the updated δs (k) to 1 as a result of frame encoding and decoding.
It is held in the Sender's additional dictionary buffer 34 during RTF, and δ sent by the backward channel
The point of comparison with r (k) is the same as in the previous embodiment. The dictionary buffer 33 stores not the initial state dictionary but the dictionary in the encoder 12 of the previous frame determined in advance from δs (k) held in the additional dictionary buffer 34. In this example, the dictionary Ds (k-1) one ARQ frame before is stored. Similarly, in Receiver, the buffer 41 stores in the buffer 42 a predetermined previous frame (S) before δr (k).
Decoding dictionary of the same frame as the ender) is stored,
That is, in this example, the decoding dictionary Dr one frame before ARQ frame
(k-1) is stored.

In FIG. 3B, reception δr (3) and buffer 34
As a result of comparison with δs (3) in the above, if they do not match, S
Ender is the dictionary Ds (2) stored in the buffer 33.
Is copied to a dictionary in the encoder 12, the third frame is re-encoded by using this dictionary, then retransmitted and a dictionary rewind notification signal is transmitted to the Receiver. Recei
Under the condition that the dictionary rewind notification signal is used, Dr (2) stored in the buffer 41 is copied to the dictionary in the decoder 25, and the dictionary is rewound (rewind). These copied dictionaries are underlined in the figure.
As a result, the identities of the Sender and Receiver dictionaries are maintained.

Next, the sender does not wait for the response of the Receiver and sends the encoded data in the form of ARQ frames one after another, and when a resend request is received, the sender resends the encoded data from the requested ARQ frame. ,
An example in which the present invention is applied to a so-called Go-Back-N retransmission control system is shown in FIG. 4A. No error is detected in the Receiver, the additional codeword δr (3) of the frame 3 is transmitted, and in the Sender, the 1RTF additional dictionary buffer 34
The δs (3) stored in the above is compared with the δr (3) transmitted in the backward channel, and if they do not match, the dictionary Ds (6) of the encoder 12 is stored in the initial state dictionary buffer 33. The initial state dictionary Ds (0) in the above is copied, the coding dictionary is initialized, an initialization notification signal is transmitted to the Receiver, and the initialized dictionary is used to retransmit the third frame and subsequent frames. Data input data buffer 3
It is extracted from 1, re-encoded, and re-transmitted. Receive
In r, when the initialization notification signal is received, D in the buffer 41
Initialize the decoding dictionary by copying r (0) into the decoding dictionary Dr (6). Each input data is held in the sender input data buffer 31 until the corresponding frame δr (k) is received after the encoded data is transmitted and the comparison process is completed.

Next, the Sender sequentially converts the code and data into ARQ frames without waiting for a Response from the Receiver and transmits the ARQ frames. When there is a retransmission request, only the encoded data of the frame requested to be retransmitted is selected and retransmitted. . A case where the present invention is applied to a so-called Selective-Repeat retransmission control method will be described. Selectiv
In the e-Repeat method, a frame that is retransmitted due to an error is not received until the frame that is received in advance and received before the frame and accumulated in the reception buffer is decoded. As shown in FIG. 4B, when the frame 3 is an error frame and the retransmission request for the error is normally detected, the sender retransmits the frame 3 in the retransmission buffer 18, and the receiver receives the retransmission frame 3. Then receive frames 3 to 6 as Receiver
Decrypt while updating the decryption dictionary of.

Next, consider the case where no error is detected in frame 8. The sender compares the δs (8) held in the dictionary buffer 34 for one RTF with the δr (8) transmitted by the backward channel, and no error is detected and there is a mismatch. Therefore, the coding dictionary Ds (11) ) To Ds in buffer 33
(0) is copied, the dictionary is initialized, an initialization notification signal is transmitted to the Receiver, and subsequently, the initialized dictionary is used to output the 8th to 1st bits in the input data buffer 31.
Data of one frame is re-encoded and then retransmitted. Rece
When receiving the initialization notification signal, the decoding dictionary D
Ds (0) in the buffer 41 is copied to s (11), and the decoding dictionary is initialized.

An example of rewinding the dictionary when no error is detected in the Go-Back-N retransmission control method will be described with reference to FIG. 5A. When no error is detected in frame 3 in Sender, 1R in Sender
When δs (3) held in the dictionary buffer 34 during TF is compared with δr (3) transmitted by the backward channel, and if it is determined that no error is detected due to mismatch, it is held in the buffer 33. The frame before δs (3), which is the frame 3, in this example, the coding dictionary Ds (2) of the immediately preceding frame is copied to the current coding dictionary Ds (6) to rewind the coding dictionary and roll it. The return notification signal is transmitted to the Receiver, and the changed dictionary is used to take out the data of the third and subsequent frames from the input data buffer 31, re-encode the data, and re-transmit the data. Upon receiving the rewind notification signal, the Receiver copies Dr (2) in the buffer 41 to the decoding dictionary Dr (6), rewinds the decoding dictionary, and then performs decoding processing. It should be noted that the third frame is retransmitted by the sender, since the encoded data is retransmitted, the encoding dictionary is not updated.

An example of rewinding the dictionary when no error is detected in the Selective-Repeat retransmission control method will be described with reference to FIG. 5B. If there is an error in frame 3 and the resend request is detected normally, Se
nder carries the encoded data of frame 3 in the transport buffer 1
When the frame 3 is received, the receiver decodes the frames 3 to 6 while updating the decoding dictionary.

Next, consider the case where no error is detected in frame 8. First, the sender compares δs (8) held in the dictionary buffer 34 for one RTF with δr (8) transmitted by the backward channel. If it is determined that they do not match and no error is detected, the encoding dictionary Ds (11)
Ds (7) in the buffer 33 is copied to the buffer 33, the dictionary is rewound, a rewind notification signal is transmitted to the Receiver, and the data of the 8th to 11th frames are buffer 31 using the rewound dictionary. , Re-encode and retransmit. Upon receiving the rewind notification signal, the Receiver copies Ds (7) in the buffer 41 to the decoding dictionary Ds (11) to rewind the decoding dictionary.

When the codeword δs (k) in the additional dictionary buffer 34 and the codeword δr (k) sent from the Receiver do not match at Sender, the error non-detection rate and compression rate when the dictionary is initialized The relationship is shown in FIG. 6A. The ZLW method is used as the compression method, and 160 bits is regarded as one frame, and the compression rate is the result obtained by computer simulation. The curve 51 shows the case where the input data length is 27 kB and the curve 52 shows the case where the input data is 530 kB. Is. In an environment where non-detection frequently occurs at 1% or more, the compression rate starts to slightly decrease, but the decrease in compression rate due to dictionary recovery at 1% or less is small, and it can be seen that the dictionary recovery functions effectively.

FIG. 6B shows the relationship between the error non-detection rate and the compression rate when the dictionary is rewound to that of the immediately preceding frame when the error non-detection is detected by the sender. The ZLW method is used as the compression method, and 160 bits is regarded as one frame, and the compression rate is a result obtained by computer simulation. The curves 53 and 54 each have an input data length of 25 k.
This is the case of B, 530 kB. The high compression rate can be maintained by rewinding the dictionary even in an environment where undetection frequently occurs at 1% or more.

As can be understood from the above description, in the present invention, when the codeword δr (k) from the Receiver and the additional codeword δs (k) of the corresponding frame k in the buffer 34 do not match, the sender's Set the encoding dictionary to the initial state dictionary D
s (o) or dictionary Ds (k-1) used for encoding in the immediately preceding frame
However, the point is to change to the dictionary used for encoding in the frame before the frame k. Which frame should be changed is determined in advance, and the sender sends a dictionary change notification. , Receiving the dictionary change notification, the dictionary may be changed so that the sender's encoding dictionary and the decoding dictionary match.

When the dictionary is not in the initial state but is changed to the dictionary Ds (k-1), Dr (k-1) of the immediately preceding frame, as in the above example, in Sender, D is stored in the buffer 33 in FIG.
When s (k-1) is always held, that is, when the coding dictionary is updated, the dictionary is copied in the buffer 33 accordingly, and similarly, the Receiver always stores Dr 41 in the buffer 41. Let (k-1) be retained. In addition,
The initial state dictionary is stored in the ROM as the encoding dictionary and the decoding dictionary, and the code word added for updating the dictionary is in the RAM.
Buffers 33 and 41, for example, in order to store them in the dictionaries Ds (k-1) and Dr (k-1) of the immediately preceding frame.
To update the dictionary in the buffer 33,
It is sufficient to copy it to 41 and update it. In the above description, when changing the dictionary to the initial state, the buffer 42 is omitted by the Receiver, and when no error is detected by the error detector 22, the new code word obtained by the decoder 25 is immediately subjected to ARQ frame control. It may be sent to the device 23.

[0030]

As described above, according to the method of the present invention, even in the transmission system in which many errors occur, even if the error cannot be detected due to too many errors, the sender can detect the error non-detection. By changing the dictionary to the state before the corresponding frame, and changing the Receiver dictionary accordingly, it is possible to always match the Sender and Receiver dictionaries, correct decoding is performed, and a high compression rate is achieved. Can be maintained.

The transmitting device and the receiving device of the present invention are effectively used to implement the method of the present invention.

[Brief description of drawings]

FIG. 1A is a time chart showing a state of changes in Sender and Receiver frames and a dictionary when the dictionary is initialized and changed when an error is not detected in the Stop-and-Wait retransmission control method, and B is a codeword unit. FIG. 7 is a diagram showing a state of comparing the dictionary buffer update parts of FIG.

FIG. 2 is a block diagram showing an embodiment of a transmission device of the present invention.

FIG. 3A is a block diagram showing an embodiment of a receiving apparatus of the present invention, and B is a diagram corresponding to FIG. 1A in the case of rewinding and changing the dictionary when an error is not detected in the Stop-and-Wait retransmission control system. is there.

FIG. 4A is a diagram in the case of initializing and changing a dictionary when an error is not detected in the Go-Back-N retransmission control system.
Corresponding figure, B is Selective-Repeat
FIG. 2B is a diagram corresponding to FIG. 1A in the case where the dictionary is initialized and changed when no error is detected in the retransmission control method.

FIG. 5A is a diagram showing a case where the dictionary is rewound and changed when an error is not detected in the Go-Back-N retransmission control method.
Diagrams corresponding to A and B are Selective-Repea
FIG. 1B is a diagram corresponding to FIG. 1A in the case where the dictionary is rewound and changed when no error is detected in the t-retransmission control method.

FIG. 6A is a diagram showing an example of the relationship between the error non-detection rate and the compression rate when the dictionary is changed, and FIG. 6B is a diagram showing an example of the relationship between the error non-detection rate and the compression rate when the dictionary is rewound and changed. is there.

FIG. 7: A is V. 42 is a diagram showing a 42-frame structure, and B is a V.V.
42 error correction procedure. It is a figure corresponding to FIG. 1A at the time of applying a 42bis data compression function.

FIG. 8 is A. 42 error correction procedure. 42bis
A block diagram showing a configuration of a conventional transmission device to which a data compression function is applied, B is a V.V. 42 error correction procedure. 42b
It is a block diagram which shows the structure of the conventional receiver which applied the is data compression function.

9A is a diagram for explaining a case where a dictionary mismatch occurs when an error non-detection occurs when data compression is applied to a conventional error correction procedure, and B is a dictionary mismatch seen in codeword units. It is a figure which shows the example of.

Claims (4)

[Claims] 1. A transmission side compresses and encodes input data using an encoding dictionary, and a new code word is given to a character string in the input data that is not in the encoding dictionary to update the encoding dictionary. While transmitting the coded data and the update codeword in frame units, the receiving side determines whether the received frame was received correctly.If it is not received correctly, it sends a resend request to the transmitting side and receives it correctly. If it is done, the coded data of the received frame is decoded using the decoding dictionary, the decoding dictionary is updated using the received codeword, and at least when the retransmission request is received by the transmitting side, In the automatic retransmission transmission method in which the receiving side retransmits the encoded data of an erroneous frame, when it is determined that the receiving side has correctly received, the update codeword in the received frame is Send to the sending side, the sending side compares the code word from the receiving side with the corresponding sending side code word, and if they do not match, the coding dictionary in the frame before the mismatched sending frame When the encoding dictionary is changed to and the data of the mismatch transmission frame is encoded using the dictionary, the encoded data and the dictionary change notification are transmitted, and the receiving side receives the dictionary change notification, An automatic retransmission transmission method characterized in that the decoding dictionary is changed in accordance with this and the encoded data of the received frame is decoded using the dictionary. 2. The input data from the input buffer is input to the encoder, compression encoded using the encoding dictionary, the encoded data is transmitted frame by frame, and the characters in the input data that are not in the encoding dictionary are input. A new code word is given to the column to update the coding dictionary, and the code word corresponding to the character string in the dictionary is transmitted in the same frame, and when the resend request is received, the correspondence in the coding buffer is received. In a transmitter of automatic retransmission transmission for retransmitting coded data of a frame, an input data buffer for accumulating the input data for at least 1 RTF, a codeword buffer for accumulating a codeword generated by encoding, and If the comparison result of the comparator for comparing the code word with the code word of the corresponding frame in the buffer for additional dictionary and the comparison result of the comparator do not match, Switch from the input buffer to the input data buffer to supply data to the encoder, and change the dictionary used for encoding of the encoder to a state before the mismatch detection frame in advance and notify of the change. A transmitter for automatic retransmission transmission, comprising: 3. An error detection is performed for each received frame, and if there is no error, the received coded data is decoded using a decoding dictionary, the dictionary is updated, and when an error is detected in the received frame, An automatic retransmission transmission receiving device for transmitting a retransmission request to a transmitting side, comprising means for returning the decoding dictionary to an initial state when a dictionary change notification is received. 4. An error detection is performed for each received frame. If there is no error, the received coded data is decoded using a decoding dictionary, the dictionary is updated, and when an error is detected in the received frame, In a receiving device for automatic retransmission transmission that sends a retransmission request to the transmission side, the contents of the additional dictionary buffer are used when the additional dictionary buffer storing the received codeword and the dictionary change notification are received. And a unit for changing the decoding dictionary to a decoding dictionary in a previous frame determined in advance by: