JPH05328082A - System for switching modem - Google Patents

Abstract

PURPOSE:To eliminate the excess procedure by means of the only standard functions and signals by sending training signals again when the request of re-transmitting the entire frames at the transmission of information followed by the transmission of training signals and to provide the transmission control procedure requiring the shorter transmission time. CONSTITUTION:In the MODEM especially for facsimile, the transmission time can be shortened with the only standard function. In the case of the retransmission of the entire frame, a protocol control section 9 sets a M0DEM 10 to a low-speed transmission mode so as to perform the long training again. After sending a correcting continuing signal CTC, the mode is set to a low-speed reception, checking whether or not the correction continuing response CTR is received. After receiving the CTR, the modem 10 is set to the high-speed transmission mode. Then a long training signal is transmitted, and the picture information is read from a memory 7 at its transmission. Thus, the transmission of the end of procedure is performed in a low-speed mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem switching system, and more particularly to a modem switching system capable of reducing transmission time by using only standard functions in a facsimile modem.

[0002]

2. Description of the Related Art Conventionally, CCITT Recommendation V.3 has been used as a modem for facsimile machines. 33, V.I. A high speed modem such as 17 is used. These modems have built-in automatic equalizers. This automatic equalizer is a gain characteristic of telephone line,
The modem on the receiving side automatically recognizes the group delay characteristic and corrects the received signal according to the characteristic. The parameter of the line characteristic is called a tap coefficient.

This tap coefficient is created by the receiving modem using the training signal sent from the transmitting modem. V. The modem recommended by 17 includes two types of training signals, a long training signal and a short training signal. The long training signal is a signal used when initial training after line connection and retraining are necessary, and the number of symbol times is as follows. Segment1 = 256BAUD Segment2 = 2976BAUD Segment3 = 64BAUD Segment4 = 48BAUD The total is relatively long at 1.393 seconds (1BAUD = 1/2400 seconds). On the other hand, the short training signal is used for resynchronization after successful long training, and is as follows. Segment1 = 256BAUD Segment2 = 38BAUD Segment3 = 0BAUD Segment4 = 48BAUD The total is 142 milliseconds.

Among them, Segment 2 is an equalizer adjustment pattern and is used for forming a tap coefficient. However, in the case of a short training signal, since the time is short, the tap coefficient is sufficiently formed. I can't afford
Short training is performed using the tap coefficient formed in the previous long training. Therefore, if the tap coefficient cannot be formed in the long training due to noise or the like, or if the tap coefficient is incorrect, the tap coefficient cannot be adjusted even in the short training thereafter, so that the image information cannot be received. On the other hand, Recommendation V. The 33 modems have only long training signals.

FIG. 8 shows a conventional V.V. It is a caller side schematic flow chart when 17 modems are used. This procedure is standardized in CCITT as a transmission control procedure (Recommendation T30) for a G3 facsimile having an error correction function (ECM). The meaning of the signal names in the figure is shown in FIG. In FIG. 8, when the facsimile machine first makes a call in step S70, negotiation (confirmation of the function of each person) with the facsimile machine on the receiving side is performed in step S71, and then the communication speed of image information, etc. Mode setting (step S72) is performed. In this figure, V. It shows the case where the 17 mode is set.

Long training is performed in step S73, and it is checked in step S74 whether preparations for receiving image information have been completed. If it is unsuccessful, the mode setting (step S72) is performed again, and if it is successful, the process proceeds to step S75.

At steps S75 and S76, a short training signal and an image information signal are transmitted, and then step S77.
At the end of the partial page (PP
S), the procedure end (EOP) is transmitted. Here, when the message confirmation (MCF) is received (step S86) and the reception of the image information is confirmed, the disconnection process (step S8).
Move on to 8).

If the receiving side has an error in the image information, the receiving side sends out a partial page request (PPR). PP on the sending side
When R is received (step S78), the process proceeds to step S79. Otherwise, P in step S87
It is checked whether or not the transmission of PS and EOP has been tried three times. If it is two times or less, the process proceeds to step S77, and if it is the third time, the process proceeds to step S88. In step S79, it is checked whether or not the request is the fourth retransmission request, and if it is three times or less, the process returns to step S75 to retransmit only the erroneous image information.

In the case of the fourth retransmission request, step S
In step S81, continue correction (CTC) is transmitted,
At 82, it is checked if a continue correction response (CTR) is received. If the CTR is not received even after the CTC is transmitted three times, the process jumps to the ending process of step S88. When the CTR is received, in steps S83, 84 and 85, the long training signal, the image information signal and the end of the partial page (PP
S) and the end of procedure (EOP) are sent in order, and the process returns to step S78 again.

[0010]

FIG. 9 shows an example of a conventional communication procedure according to the flow of FIG. In FIG. 9, after calling and negotiation, the tap coefficient is fixed by long training and image information is transmitted. However, when image information has an error and retransmission is repeated four times, long training starts. Here, if fixing of the tap coefficient fails due to noise, short training and image information transmission will be repeated four times until transfer to long training again. However, since the tap coefficient is not fixed, any transmission will fail, and there is a problem that an unnecessary procedure is repeated.

As an improved technique focusing on this point, there is a technique disclosed in Japanese Patent Laid-Open No. 4-966. In this technique, when image information fails to be received after long training, the partial page request signal (PPR) is added with information indicating whether to make the training long or short and the result is returned to the transmission side. is there.

According to this method, there is no waste of repeating short training and transmission of image information. However, the standard PPR signal format has only a field in which bits indicating which image information frame is incorrect are included, and a non-standard format must be used to indicate the training type. For this reason, there is a problem that the training instruction cannot be issued unless the terminals have non-standard functions (for example, own machines). SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate useless procedures by using only standard functions and signals, and to obtain a transmission control procedure with a shorter transmission time.

[0013]

According to the present invention, in a modem for training an equalizer, when a request for retransmission of all frames comes after sending information after sending a training signal, the training signal is sent again. Is transmitted.

Alternatively, in a modem for training the equalizer, when a request for retransmission of all frames comes when information is sent after sending a training signal,
Correction continuation signal (CTC) for retraining instruction
In addition, before sending the information, the information for designating the mode for performing the equalizer training is always added and sent, the mode is switched, and the training signal is sent again.

[0015]

With this procedure, even if the training of the equalizer fails, the training of the equalizer can be performed again using only the standard functions and signals.

[0016]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a flowchart of a transmission control procedure on the transmission side, which represents the outline of the present invention. First, a first embodiment will be described with reference to FIG. Normally, it is assumed that the modem is set to a mode in which the equalizer is not trained each time information is transmitted. Therefore, step S2 is not passed, and the process proceeds from step S1 to step S3. Information is transmitted in step S3, and it is checked in step S4 whether a resend request has been transmitted. If the resend request is not received, the transmission ends, but if the resend request is received, it is checked in step S5 whether or not it is the predetermined number of times.

If it is not the predetermined number of times, step S1
Returning to step 1, only the frame in error is retransmitted, but if it is the predetermined number of times, a signal for training the equalizer is transmitted in step S6, and information is transmitted in step S7. In step S8, it is checked whether or not a resend request has been sent, and if so, it is further checked in step S9 whether or not all frames have been resent. Here, in the case of retransmission of all frames, it is considered that the training is poor, and in step S10, a standard signal is used to
Perform the steps to train the equalizer. (The mode is not changed.) Information is sent in step S11, and the process returns to step S4. In the first embodiment, by taking such a procedure, even if the training of the equalizer fails, it is possible to carry out the training again without repeating unnecessary information transmission.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, step S10 of FIG.
In, the mode of the modem is changed to a mode in which the equalizer is trained every time information is transmitted, and then the equalizer is trained. Therefore, when returning to the original information transmission processing loop, the process goes from step S1 through step S2 to the information transmission of step S3, and the equalizer training must be performed before the information transmission. become. In the second embodiment, by changing to such a mode, the transmission efficiency can be improved when the line quality is poor.

Next, an example in which the above procedure is applied to a facsimile machine will be described. FIG. 2 is a block diagram of a facsimile apparatus to which the present invention is applied. The panel 1, the scanner 2, and the printer 3 are connected to the internal bus 14 via the respective control units 4, 5, and 6. A memory 7 for accumulating image information, a system controller 8 for controlling the entire apparatus, a protocol controller 9, and a network controller 11 are connected to the internal bus 14, and a modem 10 connected to the protocol controller 9 is connected.
Is connected to a telephone line 13 via an NCU (network control unit) 12.

FIG. 3 is an internal block diagram of the protocol control unit 9. Command creation unit 21, command analysis unit 25, TC
The F / image information creation unit 22, the TCF / image information analysis unit 24, and the modem training selection unit 23 are connected to the protocol module control unit 20, and the protocol module control unit 20 executes the transmission control procedure. Further, the command creating unit 21 and the command analyzing unit 25 are respectively through the low speed transmitting unit 26 and the low speed receiving unit 29, and the TCF / image information creating unit 22 and the TCF / image information analyzing unit 24 are the high speed transmitting unit 27 and the high speed respectively. The modem 10 is connected via the receiving unit 28, and the modem mode setting unit 23 is connected to the modem 10.

The command creating unit 21 assembles a command to be sent to the partner device according to an instruction from the protocol module control unit 20, and the modem 10 via the low speed transmission unit 26.
It is sent to the control low-speed channel. The TCF / image information creating unit 22 compresses the image information read from the memory 7, processes such as frame assembling, or a TCF for checking whether a channel can be used at this transmission speed.
A signal is created and sent to the high speed channel of the modem via the high speed transmission unit 27. The command analysis unit 25 receives a command from the control low-speed channel of the modem 10 via the low-speed reception unit 29, and the protocol module control unit 2
Notify 0. The TCF / image information analysis unit 24 sends the image information or the TCF signal to the modem 1 via the high-speed receiving unit 28.
Received from the high speed channel of 0 and checked for errors.

In accordance with an instruction from the protocol module control unit 20, the modem mode setting unit 23 sends to the modem 10 an operation mode of the modem 10 such as the speed of a high-speed channel or a control signal such as transmission / reception, channel type, training instruction, or the like. Information about giving and training failures,
It receives from the modem 10 and notifies it to the protocol module control unit 20. The modem 10 performs operations such as modulation / demodulation of signals of each channel, creation, transmission, and reception of training signals according to an instruction from the protocol control unit 9.

Next, the operation will be described with reference to the flowchart. 4, 5 and 6 are caller side flowcharts of the transmission control procedure of the present invention. First, in step S10,
When there is a transmission instruction from the panel control unit 4, the system control unit 8 issues a transmission document reading request to the scanner control unit 5. The scanner control unit 5 reads the transmission original by the scanner 2, stores it in the memory 7, and notifies the system control unit 8 that the reading is completed.

The system control unit 8 makes a call request to the network control unit 11, and the network control unit 11 dials the dial number notified by the system control unit 8 from the NCU 12.
Connect to the receiving facsimile. The protocol control unit 9 sets the modem 10 in the low speed reception mode. Step S1
In Nos. 1 and 12, it is checked whether a non-standard function setting (NSF) or a digital identification signal (DIS: CCITT standard function identification signal) indicating the function of the receiving side facsimile is received. S3
Jump to the line disconnection process of 3.

In step S13, the protocol control unit 9
Receives the digital identification signal (DIS), analyzes the parameter and notifies the system control unit 8 of the content thereof.

In step S14, the system controller 8 sets a communication mode based on the notified capability of the facsimile on the receiving side and the capability of its own station, and notifies the protocol controller 9 of the communication mode. In this flowchart, V. It shows the case where the 17 mode is set.

In step S15, the protocol control unit 9
Sets the modem 10 in the low-speed transmission mode and transmits a digital command signal (DCS: standard function setting). In step S16, the protocol control unit 9 sets the modem 10 in the high-speed transmission mode and sends a long training signal, and in step S17, continuously sends a training check signal (TCF).

In step S18, the protocol control unit 9
Sets the modem 10 to the low-speed reception mode and proceeds to step S21 if a reception preparation confirmation (CFR) is received, and proceeds to step S19 if not received. Step S19
If you receive a training failure (FTT),
Returning to step S14, if the FTT is not received, the process proceeds to step S20.

In step S20, if the number of trials in steps S14 to S17 is two or less, step S1
Return to 4, but in the case of the third time, jump to step S32,
Performs line disconnection processing. In step S21, the modem 10
Is set to the high-speed transmission mode, and V. Whether the mode is 17 mode or not is checked, and V. If it is 17 mode, step S
Short training for synchronization is performed at 23, and if not, long training is performed at step S22.

In step S24, the image information is read from the memory 7 and sent out. After sending out the image information, the protocol control unit 9 sets the modem 10 in the low-speed transmission mode. In step S25, the end of partial page (PPS) and the end of procedure (EO) indicating the end of transmission of image information
P) is transmitted and the modem 10 is set to the low speed reception mode. In step S26, it is checked whether or not a partial page request (PPR) is received. If it is received, step S26 is performed.
In 27, it is checked whether or not it is the fourth time, and if it is three times or less, jump to step S21. However, in the case of the fourth time, the process proceeds to step S34.

If the PPR is not received in step S26, it is checked in step S28 whether or not the reception disabled (RNR) is received. If it is received, the reception enabled (RR) is transmitted in step S29, It returns to step S28 again.
When the RNR is not received in step S28, the protocol control unit 9 checks in step S30 whether the message confirmation (MCF) is received, and if received, jumps to step S32. When the message confirmation (MCF) is not received in step S30, if the PPS and EOP are transmitted within two times in step S31, the process jumps to step S25, and if it is the third time, the process proceeds to step S32.

In step S32, the protocol control unit 9
Sets the modem 10 to the low-speed transmission mode and disconnects the line (D
CN) is transmitted, and the system control unit 8 is notified that the transmission has been completed. In step S33, the system controller 8
Issues a termination request to the network control unit 11, and the network control unit 11 opens the line 13.

When the PPR has been received four times, the continuation of correction (CTC) is transmitted in step S34, and it is checked in step S35 whether the continuation of correction response (CTR) has been received. If no CTR is received, step S
At 36, it is checked whether or not it has been tried three times, and if it is two times or less, the process returns to step S34, and if it is the third time, the process jumps to step S32 to perform the line disconnection process. When the CTR is received, the process proceeds to step S37. In step S37, the modem 10
Is set to the high-speed transmission mode, the long training signal is transmitted, and in step S38, the image information is read from the memory 7 and transmitted.

After transmitting the image information, the protocol control unit 9 sets the modem 10 to the low speed transmission mode, transmits the end of partial page (PPS) and the end of procedure (EOP), and receives the modem 10 at low speed. Set to mode. In step S39, it is checked whether or not a partial page request (PPR) is received. If not received, the process returns to step S28, but if received, the process proceeds to step S40.

In steps S40 and S41, the mode is V.50.
If it is 17, and whether all frames are retransmitted or not, is checked. If not, the process returns to the retransmission processing loop of step S27. However, if it is the case, it is considered that the training was unsuccessful, and the process proceeds to step S42 which is the procedure of the present invention.

The procedure of the first embodiment will be described below. In step S42, in order to perform the long training again, the protocol control unit 9 sets the modem 10 to the low speed transmission mode and sends the correction continuation signal (CTC) (the mode is not changed). In step S43, the protocol control unit 9 sets the modem 10 in the low-speed reception mode and checks whether or not the correction continuation response (CTR) is received. If no CTR is received, step S
At 44, it is checked whether or not it has been tried three times, and if it is two times or less, the process returns to step S42, and if it is the third time, the process jumps to step S32 to perform the line disconnection process. When the correction continuation response (CTR) is received in step S43, the modem 1 is received in step S45.
0 is set to the high speed transmission mode and the long training signal is transmitted. In step S46, the image information is read from the memory 7 and sent out. The protocol control unit 9
After transmitting the image information, the modem 10 is set to the low speed transmission mode, the end of partial page (PPS) and the end of procedure (EOP) are transmitted, the modem 10 is set to the low speed reception mode, and the process returns to step S26. ..

By taking such a procedure, even if the training of the equalizer at the time of retransmission fails, as in the conventional case,
The equalizer training can be performed again without repeating unnecessary information retransmission, and the transmission time can be shortened. The procedure on the receiving side is the same as the conventional one, and no change is required.

Next, a second embodiment will be described. In this embodiment, the correction continuation signal (CT
C) to V. The information set in 33 is added and transmitted. The standard continue correction signal (CTC) is
It has the same function setting information as the digital command signal (DCS), which allows the transmission terminal to change the mode.

This embodiment is intended to shorten the transmission time by using the above function and switching the mode of the terminal. The second embodiment will be described below.

First, the facsimile terminal is a V. It is assumed that the 17 mode is set. Step S41 in FIG.
Up to this is the same as the first embodiment. In step S42, the CTC is sent, but in the second embodiment, this CT is sent.
In C, the mode is V.V. 17 to V.I. Change to 33. Then, in the image information transmission processing loop of FIG. 5, the process goes from step S21 to step S22, and all training is long training.

When the line quality is poor, V. If the long training fails in 17 mode, useless short training and transmission of image information increase, and the transmission time may increase. On the other hand, the mode is V. When switched to 33, the training time becomes a little longer, but useless retransmissions are reduced, and the transmission time can be shortened.
Also in this embodiment, the procedure on the receiving side is the same as the conventional one, and no change is required.

FIG. 7 is a flowchart on the receiving side in the present invention. The operation on the receiving side is the same as the conventional one, and the V.
The case where the 17 mode is set is shown. Below, FIG.
According to the operation, first, the incoming call is detected in step S50, and the negotiation is performed in step S51.
In step S52, mode setting and long training are performed.

If the training is unsuccessful in step S53, the training fails (FT) in step S54.
T) is sent, and the process returns to step S52. In step S55, short training and image information reception are performed (when the mode is changed to V.33, long training is performed). In step S56, the PPS and EOP are received,
In step S57, it is checked whether there is an error in reception.
If there is no error, MCF is transmitted in step S63, line disconnection processing is performed in step S64, and image information is output to the printer 3.

If there is an error in the reception in step S57, the partial page request (PP
R) is transmitted. Continue correction in step S59 (CT
It is checked whether or not C) is received, and if not received, the process returns to step S55, but if received, step S60.
Move to. When there is a mode change instruction in the CTC, the mode is changed according to the instruction.
In step S60, a correction continuation response (CTR) is transmitted,
In step S61, the long training signal is received,
Do training. In step S62, the image information is received, and the process returns to step S56.

[0045]

According to the procedure of the present invention, there is an effect that a wasteful procedure can be omitted and the transmission time can be shortened by only slightly changing the procedure of the transmitting side facsimile. Also, the facsimile on the receiving side remains the same standard function as before.
Since no change is required, there is an effect that the facsimile can be carried out regardless of the facsimile of the other party.

[Brief description of drawings]

FIG. 1 is a schematic flowchart of a transmission side of a transmission control procedure of the present invention.

FIG. 2 is a block diagram of a facsimile apparatus to which the present invention is applied.

FIG. 3 is a detailed block diagram of a protocol control unit in FIG.

FIG. 4 is a transmitting side flowchart (part 1) of the procedure according to the present invention.

FIG. 5 is a transmitting side flowchart (part 2) of the procedure according to the present invention.

FIG. 6 is a transmitting side flowchart (part 3) of the procedure according to the present invention.

FIG. 7 is a receiving side flow chart of a procedure according to the present invention.

FIG. 8 is a transmission side flowchart of a conventional transmission control procedure.

FIG. 9 is a sequence chart showing an example of a conventional procedure.

FIG. 10 is an explanatory diagram showing signal names and their meanings.

[Explanation of symbols]

1 ... Panel, 2 ... Scanner, 3 ... Printer, 4 ... Panel control unit, 5 ... Scanner control unit, 6 ... Printer control unit, 7
... memory, 8 ... system control section, 9 ... protocol control section, 10 ... modem, 11 ... network control section, 12 ... network control unit (NCU), 13 ... telephone line, 14 ... internal bus 20 ... protocol module control section, 21 ... Command creation unit, 22 ... TCF / image information creation unit, 23 ... Modem mode setting unit, 24 ... TCF / image information analysis unit, 25 ... Command analysis unit, 26 ... Low speed transmission unit, 27 ... High speed transmission unit, 28
... High-speed receiver, 29 ... Low-speed receiver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ken Umezawa, 3-7-1, Fuchu, Iwatsuki-shi, Saitama Prefecture, Fujiwa Rocks Co., Ltd. Iwatsuki Plant (72) Takashi Sakayama 3-7-1, Fuchu, Iwatsuki, Saitama Prefecture No. Fuji Xerox Co., Ltd. Iwatsuki Office

Claims (2)

[Claims] 1. A modem switching system for training an equalizer, the training signal being transmitted,
Modem switching method characterized in that when a request for resending all frames is sent when information is sent, the training signal is sent again. 2. In a modem switching system for training an equalizer, following the training signal transmission,
If a request to retransmit all frames is received when the information is transmitted, a correction continuation signal (CT
A modem switching system characterized in that the information for designating the mode for training the equalizer is always added to C) before transmission, and the training signal is transmitted again.