JPH08172424A - Error retransmission system in facsimile equipment - Google Patents

Abstract

PURPOSE: To prevent transmission time from being prolonged by eliminating the retransmission repetition of error frames in a demodulation unstable section in the facsimile communication of an ECM system. CONSTITUTION: When encoding data and PPS-EDP are transmitted from a transmission side, a reception side returns PPR and requests the retransmission of the first and third frames of the error frames. On the transmission side, a communication control part 12 which is informed of a fact that the error frames are the first and third frames from a retransmission frame management part 15 recognizes that the first frame is included in the error frames for which the retransmission is requested, instructs a synchronizing signal generation part 16, lets expansion synchronizing signals (500ms) be generated and transmits training signals, the expansion synchronizing signals, the first and third frames and the PPS-EOP. On the reception side, reception within the unstable section is evaded by the expansion synchronizing signals and the first frame is normally received along with the third frame and MCF is returned. On the transmission side, DCN is transmitted and the transmission of facsimile signals is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error resending method in a facsimile apparatus capable of error correction mode (ECM) method facsimile communication.

[0002]

2. Description of the Related Art In a standard retransmission method in a conventional facsimile apparatus capable of ECM method facsimile communication, a first method and a fallback method in which a frame size is reduced and retransmission is performed as a method for shortening transmission time by repeating retransmission. There is a second method for efficiently performing.

As an example of using the first method, the "facsimile communication system" disclosed in Japanese Patent Laid-Open No. 3-40557 is cited. In this facsimile communication system, when the transmitting side receives a notification of a retransmission request, Based on a predetermined criterion such as the number of frames of the image information requested to be retransmitted or the number of times the frame number is received, it is determined whether or not the frame size of the image information is to be changed. The transmission information indicating the change of the frame size is added to the signal and transmitted, and when this transmission information is transmitted, the reception side adds the transmission information indicating the change of the frame size to the predetermined facsimile control signal and transmits it. The transmitter associates the frame number before changing the frame size with the frame number after changing the frame size when retransmitting after changing the frame size. These frame numbers are added to the image information and transmitted, and the receiving side makes a resend request based on this transmitted frame number after changing the frame size, thereby reducing the occurrence rate of data errors due to line noise. There is.

Further, as an example of using the above-mentioned second method, "data transmission device having ECM function" described in Japanese Patent Laid-Open No. 4-252664 will be cited. When the number of frames of the retransmission request is R and the number of allowable frames of error occurrence is P,
The R> P state detection means for outputting R> P information when the R> P state is detected from the retransmission request signal from the partner terminal and the number of retransmission requests for the same block when the partner terminal requests retransmission are counted. By providing the counting means for outputting the C information when the counted value reaches the set value C and the data transmission rate control means for falling back the data transmission rate when the R> P information or the C information is obtained. , Resending time is saved and communication cost is reduced.

FIG. 4 is a diagram showing an example of error resending in the error resending method of a conventional facsimile apparatus.

Referring to FIG. 4, first, the facsimile apparatus on the transmission side uses the ECM standard procedure, that is, the training signal, the standard synchronization signal (having a length of 200 ms), and then the first frame, the second frame, and the third frame. ，… ，
The encoded data composed of the final frame is transmitted to the public line.

However, if it is assumed that the public line has a large line distortion and the incoming level is low, the facsimile machine on the receiving side receives a training signal, performs high-speed modem training, and then demodulates. 1st within 300ms of unstable section with high probability of error occurrence
An error (indicated by a cross) will occur in the frame. It is also assumed that an error (indicated by a mark X) happens to occur in the third frame due to a normal cause.

After the above encoded data is transmitted from the transmission side, PP
When S-EOP (partial page signal-procedure end signal) is transmitted, the receiving side returns PPR (partial page request signal) to request retransmission of the first and third frames of the error frame.

Next, the first frame and the third frame are retransmitted from the transmitting side by the same procedure, but an error occurs again in the first frame within 300 ms of the unstable section. Here, if it is assumed that the normal error occurrence factor is recovered when the third frame is retransmitted, the third frame is normally received.

Therefore, the PPS-EOP is transmitted from the transmitting side after the first frame and the third frame, and the receiving side requests retransmission of the first frame of the error frame by PPR.

Next, the first frame is retransmitted from the transmitting side by the same procedure, but the first frame is 300 m in the unstable section.
The error occurs again within s.

Therefore, the PPS-EOP is transmitted from the transmitting side following this first frame, and the PPR-EOP is transmitted on the receiving side.
The signal requests the retransmission of the first frame of the error frame. On the other hand, the transmitting side transmits a CTC (correction continuation signal) and the receiving side returns a CTR (correction continuation response signal).

Then, a fallback procedure is performed to complete the transmission. That is, the transmitting side transmits the PPS-EOP after transmitting the training frame and the standard synchronization signal (200 ms) and then the first frame due to the speed reduction, and the receiving side normally receives the first frame and receives the MCF ( A message confirmation signal) is returned, and finally the transmitting side transmits DCN (disconnect command signal) to the receiving side.

As described above, since the retransmission of the first frame is repeated, it takes time to complete the transmission after the fallback. Even if the fallback is performed efficiently, it takes communication time due to the fallback procedure and the transmission speed reduction.

[0015]

Generally, one of the causes of ECM error retransmission in a public line for facsimile communication is a problem of poor line quality such as distortion and a problem of modem capacity on the receiving side. .

Under such a bad condition that the line distortion is large and the incoming level is low, it may take some time for the demodulation to become stable after receiving the modem training signal on the receiving side. A demodulation error is likely to occur in the unstable section.

In the above-mentioned first conventional method, in the encoded data area, the frame size is divided into small sections to suppress the spread of errors and reduce the amount of retransmitted data. However, the transmission of the first frame is received. When entering the unstable section on the side, there is a high possibility that the first frame will be repeatedly retransmitted, and it will take a long time to complete the error retransmission.

In the second conventional method, the number of error frames is counted to reduce the transmission speed when the number of error frames is equal to or more than a predetermined value. There is a high possibility that an error will occur in one frame, and if either the standard fallback procedure is used for transmission without increasing the number of error frames, or if the transmission speed is reduced by counting the number of accumulated error frames, it is more than necessary. There is a problem that the speed decreases and it takes a long time to complete the retransmission of the error frame.

Therefore, when there is an unstable section after modem training in ECM communication of facsimile, it is necessary to avoid the section and perform data transmission.

It is an object of the present invention to provide an error resending method in a facsimile apparatus in which a long transmission time is prevented by eliminating the repetition of error frame resending in a demodulation unstable section in ECM type facsimile communication. Especially.

[0021]

According to the present invention, in a facsimile apparatus capable of error correction mode type facsimile communication, a frame number identifying means for identifying a frame number of an error retransmitted frame and a frame before the facsimile encoded data. And a synchronization signal length changing means for changing the length of the synchronization signal added to the synchronization signal length changing means, the synchronization signal length changing means standardizing the length of the synchronization signal when the error retransmission frame includes the first frame. An error resending method in a facsimile apparatus is obtained, which is characterized in that the error resending frame is retransmitted with a length longer than the length.

Further, the synchronization signal length changing means retransmits the error retransmission frame with the length of the synchronization signal as the standard length when the error retransmission frame does not include the first frame. An error resending method in a facsimile machine that operates is obtained.

[0023]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an error resending method in a facsimile apparatus of the present invention. 2 is a diagram showing a configuration example of a facsimile signal transmitted from the facsimile apparatus in FIG. 1, (a) shows an example in which a standard synchronizing signal is added, and (b) shows an example in which an extended synchronizing signal is added. Is shown. Further, FIG. 3 is a diagram showing an example of error retransmission in the present embodiment, where (a) shows the case where the first frame is included and (b) shows the case where the first frame is not included.

Referring to FIG. 1, a facsimile machine 1 capable of ECM type facsimile communication according to the present embodiment is connected to an exchange 3 through a public line 2. The facsimile apparatus 1 includes a control section 11 for controlling all sequence control in the apparatus, a communication control section 12 for controlling retransmission of coded data, signals for communication procedures and error frames, and a modem for modulating / demodulating facsimile signals. Thirteen
A network control unit 14 that interfaces with the exchange 3 through the public line 2, a retransmission frame management unit 15 that manages a frame to be retransmitted by identifying a frame number of an error frame, and encoded data according to an instruction from the retransmission frame management unit 15. And a sync signal generator 16 for generating a standard sync signal and an extended sync signal to be added before.

Next, referring to FIG. 2, the transmission facsimile signal is composed of a modem training signal, a synchronizing signal, and encoded data (HDLC frame), and the synchronizing signal generating section 16 receives from the retransmission frame managing section 15. When the retransmission frame does not include the first frame according to the instruction,
The standard synchronization signal shown in (a) is generated, and when the retransmission frame includes the first frame, the extended synchronization signal shown in FIG. 2 (b) is generated.

Next, the operation of this embodiment will be described with reference to FIG.

With respect to the retransmission operation when the retransmission frame includes the first frame, referring to FIG. 3A, first, the facsimile apparatus on the transmission side uses the ECM standard procedure, that is, the training signal and the standard synchronization signal (200 ms). The encoded data composed of the first frame, the second frame, the third frame, ...
Send to.

However, assuming that the public line 2 has a large line distortion and the incoming level is low, the facsimile machine on the receiving side receives a training signal and performs high-speed modem training. 1st within 300ms of unstable section with high probability of demodulation error
An error (indicated by a cross) will occur in the frame. It is also assumed that an error (indicated by a mark X) happens to occur in the third frame due to a normal cause.

Following the above encoded data from the transmitting side, PP
When the S-EOP is transmitted, the reception side returns the PPR and requests the retransmission of the first frame and the third frame of the error frame.

On the transmission side, the retransmission frame management section 15 informs the communication control section 12 that the error frame is the first frame and the third frame based on this PPR. From this notification, the communication control unit 12 recognizes that the error frame requested to be retransmitted includes the first frame, and instructs the synchronization signal generation unit 16 to extend the synchronization signal (to guard the unstable section 300 ms). (A length of 500 ms) is generated, the extended synchronization signal, the first frame and the third frame are transmitted subsequently to the training signal, and the PPS-EOP is further transmitted.

On the receiving side, an extended synchronization signal (500 ms)
By this, reception within the unstable section (300 ms) is avoided, so that the error is suppressed from spreading to the first frame, and normal reception is performed.

If the normal error occurrence factor is recovered when the third frame is retransmitted, the retransmitted third frame is also normally received. Therefore, the MCF is returned from the receiving side, and the transmitting side transmits DCN to complete the transmission of the facsimile signal.

Next, regarding the retransmission operation when the retransmission frame does not include the first frame, referring to FIG. 3 (b), the facsimile apparatus on the transmission side first follows the standard procedure of ECM.
That is, training signal, standard synchronization signal (200m
After s), the encoded data composed of the first frame, the second frame, the third frame, ..., And the final frame and PPS-EOP are transmitted to the public line 2.

However, it is assumed that the public line 2 has good line quality and has no unstable section, but an error (indicated by a mark X) happens to occur in the second frame and the third frame due to normal factors. The receiving facsimile machine receives the training signal, performs high-speed modem training, and then returns the PPR to return the second error frame.
Request retransmission of frame and third frame.

On the transmission side, the retransmission frame management section 15 informs the communication control section 12 that the error frame is the second frame and the third frame based on this PPR. The communication control unit 12 recognizes from this notification that the error frame requested to be retransmitted does not include the first frame, and instructs the synchronization signal generation unit 16 to send the standard synchronization signal (2
00 ms) and transmits a standard synchronization signal, a second frame and a third frame after the training signal,
Further, PPS-EOP is transmitted.

Here, if it is assumed that the normal error occurrence factor has been recovered when the second and third frames are retransmitted, the retransmitted second and third frames are normally received. Therefore, the MCF is returned from the receiving side, the transmitting side transmits DCN, and the transmission of the facsimile signal is completed.

In this embodiment, the length of the extended sync signal is set to 500 ms, but it goes without saying that it is not limited to this.

[0039]

As described above, according to the present invention, in a facsimile machine capable of ECM type facsimile communication, a frame number identifying means for identifying a frame number of an error resending frame and a facsimile coded data are added in front of the frame number identifying means. Synchronization signal length changing means for changing the length of the synchronization signal. The synchronization signal length changing means makes the length of the synchronization signal longer than the standard length and retransmits the error retransmission frame when the first frame is included in the error retransmission frame. Even when there is an unstable section with a high probability, there is an effect that the possibility of completing the transmission by retransmitting the error frame once without reducing the transmission rate becomes extremely high.

Further, by applying the present invention, the reliability at the time of transmitting the first part of the transmission data is improved. Therefore, when the normal line condition is assumed, the sending time of the standard synchronizing signal should be shortened as much as possible. This has the effect of further increasing communication efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an error resending method in a facsimile apparatus of the present invention.

2A and 2B are diagrams showing a configuration example of a facsimile signal transmitted from the facsimile apparatus in FIG. 1, in which FIG. 2A shows an example in which a standard synchronizing signal is added, and FIG. 2B shows an example in which an extended synchronizing signal is added. Show.

FIG. 3 is a diagram showing an example of error retransmission in this embodiment,
(A) shows the case where the first frame is included, and (b) shows the first frame.
The case where no frame is included is shown.

FIG. 4 is a diagram showing an example of error retransmission in an error retransmission method of a conventional facsimile apparatus.

[Explanation of symbols]

 1 Facsimile device 2 Public line 3 Switch 11 Control unit 12 Communication control unit 13 Modem 14 Network control unit 15 Retransmission frame management unit 16 Synchronization signal generation unit CTC Correction continuation signal CTR Correction continuation response signal DCN disconnection command signal MCF message confirmation signal PPR part Page request signal PPS-EOP Partial page signal-Procedure end signal

Claims (2)

[Claims] 1. In a facsimile apparatus capable of error correction mode type facsimile communication, a frame number identifying means for identifying a frame number of an error resending frame and a length of a synchronization signal added before facsimile encoded data are provided. And a synchronization signal length changing means for changing,
The synchronization signal length changing means adds the first to the error retransmission frame.
An error resending method in a facsimile apparatus, characterized in that, when a frame is included, the length of the synchronizing signal is made longer than a standard length and the error resending frame is resent. 2. The synchronization signal length changing means retransmits the error retransmission frame using the length of the synchronization signal as the standard length when the first frame is not included in the error retransmission frame. An error resending method in a facsimile apparatus according to claim 1.