JPH10304009A - Communication control method and communication terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for re-setting a communication protocol by executing a training of a control channel again so as to continue communication in the case that one device cannot normally detect a signal transmitted from other device. SOLUTION: When reception by the T.30 communication protocol is started, a prescribed flag is received at first, but in the case that a prescribed time elapses without receiving the flag, the processing is continued to step 45 and re-training processing for a control channel is conducted and then reception processing by the T.30 communication protocol, that is, processing of a flow chart is executed again. In the case that the re-training processing for the control channel is conducted in step 45, is roughly classified into (1); the case that a 'NO' flag cannot be received in step S31, (2); the case that the flag is detected in step S33 but a signal is not lost, and (3); that a frame cannot normally be received in the 'YES' of the step S34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control method and a communication terminal between communication terminals such as facsimile machines, and more particularly, to an ITU-T (International Telecommunication Union) The present invention relates to a communication control method and a communication terminal device which facilitate recovery when a frame error occurs during communication according to Recommendation V.34 of the Telecommunication Standardization Sector).

[0002]

2. Description of the Related Art Generally, a communication terminal device for performing data communication such as a facsimile device converts a digital signal into a voice signal at the time of transmission and transmits the signal to a general public telephone line, and receives a voice signal from a general public telephone line at the time of reception. A modem is provided for receiving signals and converting them to digital signals.

[0003] In the case of performing data communication with a conventional communication terminal device, a modulation / demodulation device based on a half-duplex system such as the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) recommendation V.17 communication procedure is used. It is used in accordance with the procedure specified in Recommendation T.30, which is also a currently common facsimile communication procedure of the G3 standard.

[0004]

In the case of facsimile communication as described above, when a signal is transmitted from one device and a frame error occurs in one device when a response signal from the other device is detected. However, since it is necessary to send a procedure signal again from one device and wait for a response to the procedure signal, there is a problem that it takes time for error recovery. The control channel is a channel for exchanging information between the transmitting and receiving apparatuses, and is a predetermined timing before transmission of original data (for example, image data of facsimile communication) and a predetermined timing between transmissions (for example, a break of each page of facsimile communication). ) Is sent and received after training.

[0005] In recent years, an ultra-high-speed full-duplex communication procedure (hereinafter, referred to as a V.34 communication procedure) having a maximum transmission speed of 33.6 Kbps in accordance with the recommendation V.34 has been put to practical use. In such full-duplex communication, it is possible to transmit a signal from the other device and receive the signal while the signal is being transmitted from one device to the other device. Therefore, it is possible to resynchronize the control channel by transmitting a signal for performing error recovery from one device.

[0006] The present invention has been made in view of such circumstances, for example, while performing a T.30 communication procedure of facsimile communication between devices capable of full-duplex communication such as a V.34 communication procedure. A communication control method that enables resynchronization of the control channel using full-duplex communication without interrupting the T.30 communication procedure when it becomes necessary to resynchronize the control channel in A communication terminal device is provided.

[0007]

According to the communication control method of the present invention, a control channel for exchanging information between transmitting and receiving apparatuses is transmitted and received while training before and after transmission of data to be transmitted and received. In a communication control method for performing duplex communication, when one device cannot normally detect a signal transmitted from the other device, training of a control channel is re-executed and communication is continued.

In such a communication control method of the present invention, when one device cannot normally detect a signal transmitted from the other device, control channel training is executed again and communication is continued. This eliminates the need for resetting the communication procedure, which was conventionally required.

The communication control method according to the present invention is characterized in that the case where the signal cannot be detected normally includes the case where the received frame cannot be normally received.

According to the communication control method of the present invention, the training of the control channel is executed again in accordance with the state of the line, so that the communication can be reliably continued.

Further, the communication terminal apparatus according to the present invention performs full-duplex communication while transmitting and receiving a control channel for exchanging information between transmitting and receiving sides before and after transmission of data to be transmitted and received. In a communication terminal device, when a signal transmitted from another device cannot be normally detected, the communication terminal device requests another device to re-execute control channel training.

In such a communication terminal device of the present invention, when a signal transmitted from another device cannot be normally detected, a request is made to another device for re-executing control channel training, and another When the device accepts the request, the control channel training is executed again and the communication is continued, so that it is not necessary to reset the communication procedure which has been required conventionally.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a specific configuration example when a communication terminal device according to the present invention is applied to a facsimile device.

In FIG. 1, reference numeral 1 denotes a CPU (central processing unit) which functions as a control unit of the facsimile apparatus, and a ROM (Read) in which a program for controlling the operation of the entire facsimile apparatus is stored in advance. Only Memor
y) 2 and a RAM (Random Access Memory) 3 functioning as a storage unit for storing data necessary for control by the CPU 1 or data that needs to be temporarily stored during operation.

The CPU 1 has an NCU (Network Control Unit).
nit) 4 and modem 5 are connected. NCU 4 is CPU 1
, And controls the connection between the line L and the facsimile machine, and has a function of transmitting a dial pulse corresponding to the telephone number of the communication partner and a function of detecting an incoming call. The line L is connected to a general public telephone line (not shown).

The modem 5 modulates and demodulates the transmission / reception data, specifically, modulates the transmission data into a voice signal and sends it to the line L via the NCU 4, and conversely, the voice received from the line L via the NCU 4 Demodulate the signal into a digital signal. Although there are products with various capabilities as the modem 5, in this example, it is assumed that the modem 5 is capable of a V.34 communication procedure compatible with full-duplex communication.

The CPU 1 is further connected to a reading unit 6, an image memory 7, a codec 8, a recording unit 9, an operation unit 10, a display unit 11, and the like. The reading unit 6 reads a document image using, for example, a CCD image sensor. The image memory 7 stores image data read by the reading unit 6 and image data received from outside via the line L and the modem 5. The codec 8 encodes the image data to be transmitted and decodes the received image data. Recorder 9
Records the received image data or the image data read by the reading unit 6 on recording paper (paper). The operation unit 10 includes ten keys for inputting numbers such as telephone numbers, one-touch keys, abbreviated keys, operation keys for instructing various operations, and the like. The display unit 11 includes a CRT display or an LCD (Liquid Crystal Display) that displays various information such as a telephone number input by operating the operation unit 10.

Next, the operation of the facsimile apparatus which is the communication terminal apparatus of the present invention having the above-described configuration, that is, the execution procedure of the communication control method of the present invention will be described with reference to the CPU 1 of the receiving side (called side) apparatus. The control procedure will be described below with reference to the flowcharts of FIGS. In the following description, it is assumed that the transmitting side (calling side) device also has the same function.

First, when communication starts after receiving a call,
The actual communication speed is determined by performing the pre-procedure based on the V.8 communication procedure (step S11).

Next, probing and equalizer training are performed according to the V.34 communication procedure (step
S12). In this method, information such as modem capabilities, line probing results, data mode modulation parameters, and the like are exchanged between both devices on the transmission side and the reception side, and the communication speed is determined by transmitting and receiving a training signal.

Thereafter, facsimile communication based on ITU-T Recommendation T.30 is started (step S13). At this time, the receiving device transmits a DIS (digital identification signal) indicating its own standard CCITT capability, and the T.30 communication procedure including the DCS (digital setting command signal), which is a signal responding to the DIS, from the transmitting device. It will be in a state of waiting for signal reception (step S1
Four). When the DIS is normally received from the transmitting device within a predetermined time (“YES” in step S14, “N” in step S20)
O ”), the receiving device performs transmission according to the T.30 communication procedure.
(Step S15). The transmitting device that has received this transmits the image data of the facsimile communication (step S16).

After receiving the image data of the facsimile communication, the receiving device receives a signal of the T.30 communication procedure.
("YES" in step S17), the transmission of the T.30 communication procedure is performed correspondingly, and if the reception is performed again in the T.30 communication procedure (step S19), it is determined that the facsimile communication is completed. The whole process ends.

It should be noted that the CPU 1 of the receiving side apparatus executes step S1.
If the reception by the T.30 communication procedure is not performed within the predetermined time in step 7 ("YES" in step S20), the process is interrupted as a communication error.

Now, a case where the receiving-side apparatus cannot receive the DCS signal from the transmitting-side apparatus in step S14 will be described with reference to the flowchart of FIG. 3 showing details of the processing in step S14.

When reception by the T.30 communication procedure is started, a predetermined flag is first received. If the flag cannot be received ("NO" in step S31) and a predetermined time elapses, If “YES” in step S32), the process proceeds to step S45 characterizing the present invention.

If the predetermined flag has been normally received ("YES" in step S31), then a communication frame is received (step S33). If a frame has been received ("YES" in step S33), there is no FCF (facsimile control field) error ("NO" in step S34).
If the content of the received frame is not CRP (command retransmission) (“NO” in step S35) and is not DCN (line disconnection) (“NO” in step S36), the frame is considered to have been received normally. Then, the process proceeds to step S15 in FIG.

If the content of the received frame is CRP (command retransmission) in step S35, the process proceeds to step S40, which will be described later. In step S36, the content of the received frame is DCN (line disconnection). If so, the process proceeds to step S43, and the line is disconnected.

When the frame is not received (step S33)
If the signal does not disappear within 200 milliseconds ("YES" in steps S37 and S38), the process proceeds to step S42 to be described later and the line is disconnected. If it does not disappear within 3 seconds ("YES" in step S39)
Then, the process proceeds to step S45 described above.

On the other hand, FCF (facsimile control field)
If there is an error ("YES" in step S34), if the signal does not disappear within 3 seconds (step S40
"NO" in S41, and "YES" in S41), and the receiving-side device transmits a DCN (line disconnection) signal by itself (step S42) and disconnects the line (step S43).

When the signal disappears but is delayed for 200 milliseconds
("YES" in step S40, "YES" in S44), the retraining process of the control channel characterizing the present invention is performed (step S45), and thereafter, the receiving process by the last T.30 communication procedure, that is, as shown in FIG. The processing of the flowchart that has been performed is executed again.

From the above, when the control channel retrain process of step S45 is performed, (1) step S31
If the "NO" flag could not be received in (2), the flag in step S33 could be detected but the signal did not disappear within a predetermined time, (3) the "YES" frame was normal in step S34 If it cannot be received, it can be roughly classified into the following three cases. The control channel retraining process itself is defined in ITU-T Recommendation V.34, section 12.8.

In the above embodiment, the case where the V.34 communication procedure is applied to facsimile communication has been described, but it goes without saying that the present invention is applicable to general full-duplex communication. The case where the data transmitted by the V.34 communication procedure is image data of facsimile communication has been described, but it goes without saying that other digital data may be used.

[0033]

As described in detail above, according to the communication control method of the present invention, when one device cannot normally detect a signal transmitted from the other device, the control channel training is executed again. Since the communication is continued after that, there is no need to reset the communication procedure which has been required conventionally.

Further, according to the communication control method of the present invention, the training of the control channel is executed again according to the state of the line, so that the communication can be reliably continued.

Further, according to the communication terminal device of the present invention, when a signal transmitted from another device cannot be normally detected,
The request for re-execution of the control channel training is issued to another device, and when the other device accepts the request, the control channel training is executed again and the communication is continued. There is no need to reset the procedure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a specific configuration example when a communication terminal device according to the present invention is applied to a facsimile device.

FIG. 2 is a flowchart showing an execution procedure of a communication control method according to the present invention.

FIG. 3 is a flowchart showing an execution procedure of a communication control method according to the present invention.

[Explanation of symbols]

 1 CPU, 5 modem, L communication line.

Claims (3)

[Claims] 1. A communication control method for performing full-duplex communication while transmitting and receiving a control channel for exchanging information between transmitting and receiving apparatuses before and after transmission of data to be transmitted and received. A communication control method for re-executing control channel training and continuing communication when a signal transmitted from the other device cannot be normally detected. 2. The communication control method according to claim 1, wherein the case where the signal cannot be normally detected includes a case where a received frame cannot be normally received. 3. A communication terminal device for performing full-duplex communication while transmitting and receiving a control channel for exchanging information between transmission and reception sides before and after transmission of data to be transmitted and received. A communication terminal device for requesting the other device to re-execute control channel training when a signal transmitted from the device cannot be normally detected.