JP2707456B2 - Image information transmission device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image information transmission device.

[Prior Art] A facsimile apparatus that transmits image information in accordance with an error correction mode (hereinafter abbreviated as ECM) of the G3 standard recommended by CCITT has been put to practical use.

In this ECM, the transmitting side sets a 256-byte or 64-byte image information of each page in a maximum of 256 data frames conforming to HDLC to form a data signal of one block, and transmits the data signal in units of one block. I do.

The receiving side receives the data signal, checks a transmission error for each frame, and if an error occurs, requests retransmission of image information of the frame.

When the retransmission is requested, the transmitting side forms a data signal of one block based on the image information of the requested frame and retransmits the data signal.

By the way, in recent years, car phones and MCA (Multic Channel
Access) system is used for facsimile communication. In such a case, a transmission error is likely to occur because the line state is likely to deteriorate using a wireless line.

Therefore, when performing communication using the ECM, the retransmission operation is often performed repeatedly.

FIG. 9 shows an example of a transmission control procedure in such a case. For example, the transmitting side now has a block of data signals PIX and PPS.E having eight image information frames.
Assume that an OP signal has been transmitted.

In the example shown in the figure, the receiving side receives the data signal, detects a transmission error for five frames, sends out a PPR signal in which the error frame position for the five frames is set, and requests retransmission. .

Next, the transmitting side transmits the image information of the five frames for which retransmission has been requested as the first retransmission data signal PIX R1.

Thereafter, transmission errors occur continuously, and the retransmission processing is repeated. That is, all 5 frames for the retransmitted data signal PIX R1 have errors for 3 frames for the second retransmitted data signal PIX R2, and 2 frames for the 3rd retransmitted data signal PIX R3, and the receiving side has PPR. A retransmission request is made by each signal.

Then, after the third retransmission process, the transmitting side transmits a CTC signal to notify the downshift of the data transmission speed from 4800 bps to 2400 bps, and the receiving side responds by transmitting a CTR signal. .

Next, the transmitting side repeats the retransmission in the same manner, and for the fourth and fifth retransmission data signals PIX R4, R5, respectively,
A frame error has occurred, and transmission has been successful with the sixth retransmission data signal PIX R6.

[Problems to be Solved by the Invention] As described above, conventionally, one block of data signal PIX
For every retransmission operation of Ri, PPS.
Communication of predetermined procedure signals such as EOP signal and PPR signal is performed.

By the way, the inventor has measured the communication time when the conventional facsimile apparatus performs communication according to the procedure shown in FIG. 9 by experiments. According to the measurement, the communication time spent for correctly transmitting the image information of two frames after the downshift was as follows.

That is, the communication time of each procedure signal is the data signal PIX
R4 is 3250 ms, data signal PIX.R5 is 2145 ms, data signal PI
X.R6 2150ms, PPS.EOP signal 1380ms, PPR signal 2275m
s, MCF signal was 1260 ms, and DCN signal was 1245 ms. Then, when these are summed up, it becomes 18740 ms. In the above example, about 19 seconds were spent for retransmission of two frames.

Thus, in the conventional ECM, when the line condition is bad,
There is a problem that the retransmission process is repeated and the communication time becomes longer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image information transmitting apparatus which can solve the above-mentioned problems and shorten the communication time.

[Means for Solving the Problems] To achieve the above object, according to the present invention, when the retransmission is requested, the transmitting side arranges a plurality of the same data frames in the data signal and transmits the data signal, while the receiving side performs retransmission. The frame number of the requested data frame is stored, and the frame number set in each data frame received by the retransmission request is compared with the frame number of the requested retransmission to confirm whether the requested frame is the retransmission requested frame. In the case of a frame for which retransmission has been requested, image information of a corresponding data frame is extracted.

[Operation] When a certain condition is satisfied, the transmitting side arranges a plurality of same data frames in one data signal and transmits the same.
The receiving side can select the correct one from among the plurality and use it as the received information.

Therefore, even if a transmission error occurs, a data error rarely occurs in all of a plurality of frames, so that correct image information can be transmitted by one retransmission.

As a result, the number of times a procedure signal for repetition of retransmission is communicated is reduced, so that the communication time is reduced.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of an in-vehicle facsimile system according to one embodiment of the present invention. In the figure, a facsimile apparatus 1 is connected to a car telephone apparatus 3 via an interface circuit 2, and a handset 4 for a telephone call and a predetermined operation of the car telephone is connected to the interface circuit 2.

In the facsimile machine 1, a scanner 11 reads a document image and extracts image information of a predetermined resolution, and a plotter 12 records the image information on a recording sheet. The encoding / decoding section 13 encodes image information to be transmitted and decodes received image information. The image memory 14 temporarily stores image information of one block to be transmitted and received.

The modem 15 modulates and demodulates image information and transmits the same, and also transmits various procedure signals in a transmission control procedure. The communication control section 16 executes transmission control by the ECM to execute predetermined facsimile communication.

The operation display section 17 displays the operation state of the apparatus and the like and performs various operations. The system control unit 18 includes a microcomputer system,
The respective parts are controlled to execute a predetermined operation of the facsimile apparatus.

Next, the transmission / reception operation of the facsimile apparatus 1 will be described by taking as an example a case where facsimile communication is performed between the vehicle-mounted facsimile systems of the present embodiment.

FIG. 2 shows the operation on the transmitting side in this case, FIGS. 3 (a) and 3 (b) show the operation on the receiving side, and FIG. 4 shows an example of a transmission control procedure between the two.

That is, on the transmission side, first, an operator sets a transmission original on the facsimile apparatus 1 and performs a predetermined reading operation. As a result, the facsimile apparatus 1 reads the original image, encodes the image information, and stores it in the image memory 14 (process 101).

Next, the transmitting-side operator calls the receiving-side operator by a predetermined calling operation of the handset 4 and negotiates to perform facsimile communication. Here, the sender
The starting operation for transmission and the receiving side perform the starting operation for reception, respectively (FIG. 2, process 102, FIG. 3 (a)).
Processing 201).

As a result, the facsimile machine 1 on the transmitting / receiving side is activated, and first, the receiving side sends out a CED signal and a DIS signal,
Next, the transmitting side transmits the DCS signal, the modem training signal, and the TCF signal. In this example, the TCF signal is transmitted at a data transmission speed of 4800 bps.

The receiving side now performs modem training.
Now, if this modem training is successful, CF
An R signal is transmitted, and the transmitting side confirms this. More than,
This is the message pre-procedure on the transmitting / receiving side (Fig. 2, process 10).
3, FIG. 3 (a), processing 202).

Next, the transmitting side reads out the image information of one block to be transmitted from the image memory 14 (FIG. 2, processing 104), and performs a predetermined frame conforming to HDLC by a known technique (processing 105). And the data signal PIX thus formed
And a procedure signal. Now, assuming that the image information to be transmitted is only one block, a PPS.EOP signal indicating the end of one block and the end of a page is transmitted as the procedure signal (process 106).

This data signal PIX is a known signal, and as shown in FIG. 5, a synchronization signal section in which a number of flag sequences F are arranged, an encoding information section in which image information is set, and an image information frame. Is completed and a return information section indicating return to the transmission control procedure. The encoded information section is composed of up to 256 frames FCDF0 to FCDFn, and the return information section is composed of three frames RCP1 to RCP3.

Each of the frames FCDFi and RCPi is formed in the data format of the HDLC frame. The frame FCDFi includes a flag sequence F, an address field A, a control field C, a facsimile control field FCF, a facsimile information field FIF, a frame check sequence FCS, and a flag sequence F.

In each of the above fields, each of the fields other than the facsimile information field FIF and the facsimile control field FCF is 1-byte data. The flag sequence F is for identifying the start and end of a frame, and is data of "0111 1110". Since address designation is not required in facsimile communication, all "1" data are set in the address field A in a facsimile apparatus using a normal telephone line network.

The control field C indicates the last frame in the encoded information section and the return information section, and is set to "1100 1000" in the last frame and "1100 0000" in other frames.

The facsimile control field FCF indicates the type of a frame, and information "FCD" indicating an image information frame is set in the encoding information section, and information "RCP" indicating the end of the image information is set in the return information section. "Is set.

Facsimile Information Field FIF
Is present only in the frame of the coded information section, in which a frame number No from 0 to 255 and a coded image information CD having a fixed number of bits of 256 bits or 64 bits are set. In the case of the last frame FCDFn, the image information CD
, Dummy data of all "0" for setting the data to be set with the RTC code to the above-mentioned constant bit is set.

In the frame check sequence FCS, a CRC code for detecting a transmission error of each data of the frame is set.

The facsimile machine 1 on the receiving side receives the data signal transmitted in the above format (FIG. 3 (a)).
Process 203), and sequentially stores them in a data buffer (not shown).
Then, synchronization is established by detecting the preamble flag sequence F (process 204), and an HDLC frame following the preamble is determined (process 205).

Next, first, each frame FCDF of frames FCDF0 to FCDFn
For each i, detection of the address field A, detection of the control field C, and detection of the information "FCD" in the facsimile information field FIF are sequentially executed. Then, when they are correctly detected (Y in step 206)
From the process 207, the process 207 Y, the process 208, and the process 208 (Y), and read the frame number No.
9).

Next, when the reception is not the first reception, that is, the reception in response to the retransmission request (N in processing 210), the image information CD of each frame is extracted and sequentially stored in the main image memory 14 (processing 21).
1).

By the way, when receiving data in this way, the reception result of the image information of each frame in one block is stored as error frame data as 256-bit data corresponding to the frame. Then, at the start of the reception process, all the bits of the 256-bit data are set to the “error present” state.

Therefore, the transmission error of each frame is checked using the CRC code of the frame check sequence FCS (processing 21).
2) If there is no error, the corresponding bit of the error frame data is reset (process 213). And
The same operation is repeated for the next frame (processing 203
What). If a transmission error is detected by the above check (N in process 212), the process for the next frame is executed as it is (to process 203).

When the reception of the encoded information section is completed, a signal of the return information section is received next. In this case, the information "FCD" is not detected in the facsimile information field FIF, and the information "RCP" is detected. When this "RCP" is detected (N in processing 208, processing 214, Y in processing 214), the data of each of the frames RCP1 to RCP3 is checked using a CRC code (processing 215).

If there is no error in the data (Y in step 215), it is next determined from the error frame data whether there is a transmission error in the received data signal (step 21).
6). If there is a transmission error (Y in step 216),
It is determined whether a retransmission request is possible (process 217). That is,
If the PPS.EOR signal is transmitted from the transmitting side, retransmission is aborted and retransmission cannot be requested.
Since the S.EOP signal has been received, a retransmission request can be made.

In this case (Y in step 217), a PPR signal in which the error frame data is set is transmitted, and a request for retransmission of the error frame is made (step 218). Then, the next data signal to be retransmitted is received (to process 203). If there is no error frame (N in process 216),
The above reception processing ends.

On the other hand, when the address field A or the control field C is not detected in each frame FCDFi (N in processing 206, N in processing 207), and when the information “RCP” is not detected (N in processing 214), The detection state is cleared (step 219), and the process returns to the data signal reception (step 203). If an error is detected in frames RCP1 to RCP3 (N in process 215), the process returns to data signal reception (to process 203). Note that due to such various detection errors, the last frame of one block may not be correctly identified, and the reception state may be held in the process 203. In this case, a timer routine (not shown) is provided, and when a data signal is not received for a predetermined time, the processing from processing 216 is executed.

As a result, when the address field A and the control field C are not detected, the bits of the corresponding frame of the error frame data remain set to the "error present" state. Even if the information "RCP" is not detected, or if an error is detected in frames RCP1 to RCP3, if the image information of one block up to that point has been normally received without error, the image information is Is valid.

Through the above reception processing, the received image information for each frame is stored in the image memory 14. If there is a frame configuration error or image information data error due to a transmission error, a request for retransmission of those frames is made.

Here, for example, it is assumed that the transmitting side has transmitted image information of eight frames to frames FCDF0 to FCDF7 in the data signal PIX. At this time, as shown in FIG. 4, if a transmission error occurs in five of the eight frames, a PPR signal is transmitted from the receiving side, and
A request for retransmission of the five frames is made.

When the retransmission is requested in this manner (Y in FIG. 2, process 107), the transmitting side checks the number of retransmissions already executed (process 108). In the present example, the number of retransmissions is zero. As described above, if the number of retransmissions is three or less, N in process 108), and then the number of frames requested to be retransmitted is determined (process 109). In this example, the number of frames is 5
It is. As described above, when the number of frames exceeds three frames (N in process 109), a variable N that is the number of repetitions of the next data signal transmission operation is set to 1 (process 110).

Then, the image information of each requested frame is read from the image memory 14 (process 111), and a predetermined frame is formed in accordance with the HDLC in the same manner as described above (process 112). As shown in (1), it is transmitted as the first retransmission data signal PIX R1 (process 113).

Next, the variable N is set to N = N-1 (step 114), and the value of the variable N is checked (step 115). In the present example, the variable N = 0. In this case (Y in processing 115), after transmitting the PPS.EOP signal which is a procedure signal (processing 116), it waits for a response from the receiving side (to processing 107).

On the other hand, the receiving side receives the retransmitted data signal, detects the information "FCD" of each frame FCDFi in the same manner as described above (FIG. 3 (a), Y in the process 208), and outputs the frame number No.
Is read (FIG. 9B, processing 209). Then, in the case of retransmission / reception (process 210), the read frame number No.
It is determined whether or not the frame is the frame for which retransmission has been requested, based on whether or not the frame is indicated by the error frame data indicating the frame for which retransmission has been requested (process 220).

Here, if the frame has been requested to be retransmitted (step 220
(Y), the storage position of the image memory 14 corresponding to the frame number No is determined (process 221), and the received image information is stored at that position (process 222). Next, a data error of the image information is checked (step 212), and if there is no error (step 2).
12) The corresponding bit of the error frame data is reset (step 213).

If the frame is not a retransmission requested frame (step 22
(N of 0), for example, since the frame number No. is considered to be a transmission error, the image data is not stored, the detection state of each frame data is cleared (process 219), and the next data signal is received. (To process 203).

The above processing is executed for each received frame,
Here, a frame that could not be received correctly is requested to be retransmitted again. In addition, the retransmission operation is executed from the transmitting side in the same manner.

In the example of FIG. 4, an error has occurred in all five frames with respect to the first retransmission data signal PIX R1, and a retransmission request has been made.

Next, a three-frame error occurs with respect to the second retransmission data signal PIX R2, and a two-frame error occurs with respect to the third retransmission data signal PIX R3, and a retransmission request is similarly issued.

When the retransmission request is received and the retransmission has already been performed three times as shown in this example (Y in processing 108 in FIG. 2), the transmitting side transmits a CTC signal to increase the data transmission rate from 4800 bps. Shift down to 2400 pbs (process 117). When the number of retransmission-requested frames becomes three or less (processing
109), the variable N is set to 3 (process 118).

As a result, as described above, the fourth retransmission data signal
PIX R4 is transmitted (steps 111 to 113). Also, in this case, since the variable N = 3, when the variable N = N−1 (process 114), the variable N does not become 0 (N in process 115),
The transmission of the retransmission data signal PIX R4 is repeated three times (to process 111).

Now, for example, on the receiving side, after reception of the retransmission data signal PIX R3, the image memory 14, as shown in FIG. 6 (a), image information cd ₀ ~cd ₇ of each frame FCDF1~FCDF7
There are stored, and image information cd ₁ and cd ₃ of them is a data error. In this case, in the error frame information, as shown in FIG.
correctness of cd ₀ ~cd ₇ is shown.

In this state, assume that the first retransmission data signal PIX R4 has been received. In the retransmission data signal PIX R4, the facsimile information field FIF includes (c) in FIG.
As shown in, the image information cd ₁ and cd ₃ with each frame number no ₁ and no ₃ is transmitted is set.

Here, it is assumed that a data error has occurred in the frame number no ₁ and the image information cd ₃ due to a transmission error.

At this time, the receiving side first reads the frame number no ₁ and determines whether or not the frame number is a frame number requested to be retransmitted indicated by the error frame data shown in FIG.
In this case, since the frame number no ₁ has a data error, it is determined that the frame is not the frame for which retransmission was requested, and the image information
cd ₁ is not ejected.

Next, since there is no data error in the frame number no ₃ , the image information cd ₃ is extracted and stored in a predetermined area in the image memory 14. However, since the data is determined to be a data error by the error check using the CRC code, the error frame data is not reset as shown in FIG.

Next, it is assumed that the second retransmission data signal PIX R4 is received, and at this time, as shown in FIG. 7 (c), the frame number no ₃ has an error. In this case, the image memory 14 contains
While the image information cd ₁ is stored in the image memory 14, the error check is OK, so as shown in FIG.
The corresponding bit of the error frame data is reset to indicate that the reception was successful. On the other hand, the frame number
Since no ₃ is an error, the image information c
d ₃ is not taken out.

Next, receives a retransmission data signal PIX R4 of the third, this time, as shown in FIG. 8 (c), image information cd ₁ is assumed to be an error. In this case, as shown in FIG.
Since the frame number no ₁ indicates that normal reception has already been performed by the error frame data, the image information cd ₁ is not extracted. On the other hand, at this time, since both the frame number no ₁ and the image information cd ₃ are correct, the image information cd ₃ is stored in the image memory 14 and the corresponding bits of the error frame data are stored as shown in FIG. Reset.

Thus, image information cd ₀ ~cd ₇ in the image memory 14, it becomes free from error all.

When there is no error frame in this way (N in step 217 in FIG. 3A), the receiving side executes a predetermined post-message procedure and ends the above receiving processing.

When the retransmission request is no longer made on the transmitting side (see FIG. 2).
N) of the process 107, the corresponding message post-procedure is executed, and the transmission process ends.

As described above, in the present embodiment, when the number of retransmission frames becomes three or less, the transmitting side transmits the data signal three times, thereby transmitting the same frame three by three. Then, the receiving side takes out the image information having the correct frame number from the three, and checks for a data error. If the data error is correct, the reception is determined to be normal.

Therefore, even if a transmission error occurs, a data error rarely occurs in all of a plurality of frames, so that correct image information can be transmitted by one retransmission.

As a result, the number of communication of the procedure signal for repeating retransmission is reduced as compared with the related art, so that the communication time is shortened.

By the way, the inventor has measured the communication time when the facsimile apparatus of the present embodiment performs communication according to the procedure shown in FIG. 4 by experiments. According to the measurement, the communication time spent for correctly transmitting the image information of two frames after the downshift was as follows.

That is, the communication time of each procedure signal is the data signal PIX
R4 was 3250 ms, the PPS.EOP signal was 1380 ms, the MCF signal was 1260 ms, and the DCN signal was 1245 ms, for a total of 13635 ms.

Thus, in the present embodiment, the communication time spent for correctly transmitting the image information of two frames is about 14 seconds, which is about 5 seconds compared to the conventional 19 seconds shown in FIG. Has been shortened.

In the above embodiment, the same frame is transmitted a plurality of times when the number of retransmission frames becomes three or less. However, it is needless to say that the number of frames can be arbitrarily set. Also, the same frame is transmitted a plurality of times, such as when the retransmission operation is repeated a certain number of times,
Even if other conditions are arbitrarily set in advance for the communication result, the present invention can obtain the same effect.

Furthermore, when transmitting the same frame, the data signal having the frame configuration shown in FIG. 5 is transmitted three times. However, it is needless to say that the number of retransmissions can be set arbitrarily, The return information section may be transmitted once, and the encoded information section alone may be transmitted a plurality of times.

[Effects of the Invention] As described above, according to the present invention, when a certain condition is satisfied, the transmission side arranges and transmits a plurality of identical data frames in one data signal, so that a transmission error occurs. However, since data errors rarely occur in a plurality of frames, correct image information is transmitted by one retransmission, so that the number of times of communication of a procedure signal for repetition of retransmission is reduced, thereby shortening communication time. Will be done.

[Brief description of the drawings]

FIG. 1 is a block diagram of an in-vehicle facsimile system according to one embodiment of the present invention, FIG. 2 is an operation flowchart of a transmission process, FIGS. 3 (a) and (b) are operation flowcharts of a reception process, FIG. Is a time chart showing an example of a transmission control procedure, FIG. 5 is a diagram showing a frame configuration of a data signal, and FIG.
8 to 8 are explanatory diagrams of the image information extracting process on the receiving side, and FIG. 9 is a time chart showing an example of a conventional transmission control procedure. 1 ... facsimile machine, 2 ... interface circuit,
3 ... car phone device, 4 ... handset, 11 ... scanner, 12 ... plotter, 13 ... encoding / decoding unit, 14 ...
... Image memory, 15 ... Modem, 16 ... Communication control unit, 17 ...
... operation display unit, 18 ... system control unit.

Claims (1)

(57) [Claims] 1. A transmitting side transmits a data signal formed by setting a frame number and image information in each data frame of a fixed format, and a receiving side receives the data signal and detects a transmission error. Then, the transmitting side is notified of the frame number in which the error has occurred, and a retransmission request is made.
An image information transmitting apparatus for retransmitting a data frame of the frame number for which retransmission has been requested, wherein the transmitting side includes, when a retransmission is requested, arranging a plurality of same data frames in the data signal and transmitting the same data frame. On the receiving side, an error frame information storage unit for storing a frame number of the data frame requested to be retransmitted, a frame number set in each data frame received by the retransmission request and the retransmission request An image information transmitting apparatus comprising: a retransmission request frame confirming unit for collating with a frame number; and an image information extracting unit for extracting image information of each data frame having the same frame number.