JP3247560B2 - Data communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication apparatus which needs to change a modulation mode according to a data type.

[0002]

2. Description of the Related Art In data communication, when it is necessary to change the modulation mode during communication, the receiving side often loses the judgment as to which modulation mode should receive the next arriving signal at the time of mode switching. Occurs.

For example, in a facsimile communication apparatus defined in the G3 standard of the ITU-T recommendation, the transmission of a procedure signal for confirming mutual functions of transmission and reception and setting operation specifications of transmission and reception is performed by 3
A 00 bps FSK modulation method (hereinafter referred to as a low-speed mode) is used.
Standard specifications using a 0 bps PSK modulation method (hereinafter, referred to as a high-speed mode) are defined.

[0004]

The above-mentioned high-speed and low-speed mode switching does not cause any problem if transmission and reception are repeated without abnormality according to a predetermined procedure. If it cannot be received, inconvenience occurs.

[0005] The process of generating the problem will be described below.

FIG. 7 is an explanatory diagram showing a standard signal exchange between the transmission and reception of the above-mentioned G3 facsimile communication apparatus.

[0007] The right side of the center line shows the signal transmitted by the image signal receiving side (RX: reception), and the left side shows the signal transmitted by the image signal transmitting side (TX: transmission). Also, the direction from the top to the bottom of the figure represents the passage of time. The signals transmitted at each time are given the names shown in the figure, and the meaning and role of each signal are defined in the ITU-T recommendation, but the contents are well known. Detailed description of each is omitted.

In FIG. 1, a training signal (TR)
N), the image signal (PIX), and the control signal (RTC) indicating the end of the image signal are transmitted in the high-speed mode. Therefore, after transmitting the TRN in the high-speed transmission mode, the transmitting side switches the modem to the low-speed reception mode, receives the CFR, and
In order to transmit the RN / PIX / RTC signals, it is necessary to set the high-speed transmission mode.

On the receiving side, after receiving DCS, TR
Set the modem to the high-speed reception mode to receive the N signal, then set the modem to the low-speed transmission mode to transmit the CFR signal, and then to the high-speed reception mode again to receive the TRN / PIX / RTC signals. Must be set.

[0010] As described above, in the G3 facsimile communication apparatus, the type and transmission order of signals in half-duplex communication are predetermined, and the mode of the modem may be set to the predetermined mode.

FIG. 7 shows a standard communication procedure. In addition, there is a case where another procedure signal such as polling transmission / reception by DTC or transition to voice communication by PRE-Q is used. In this case, the mode setting of the modem is also predetermined.

As described above, there is no problem when communication is performed normally, but a problem occurs when a signal cannot be normally received due to deterioration of communication quality or the like.

In FIG. 7, for example, when the CFR sent from the receiving side cannot be normally received by the transmitting side, the transmitting side determines that each DCS / TRN signal transmitted by itself cannot be normally received by the receiving side. And the DCS / TRN signal is transmitted again after a predetermined time has elapsed.

On the other hand, after transmitting the CFR on the receiving side, the transmitting side normally receives the CFR, and then the TRN / PIX / R
The modem is switched to the high-speed reception mode on the premise of transmitting TC, and waits for a signal to arrive. However, since the actually arriving signal is the DCS in the low-speed mode, it cannot be received and continues to wait for a significant signal.

On the other hand, on the transmitting side, since there is no response to the retransmission of the DCS / TRN signal, retransmission of the same signal is repeated, transmission and reception of different modes are repeated for both, and finally the time-out is reached, leading to line opening. .

In order not to cause the above troubles,
After transmitting the CFR on the receiving side, it is necessary to set two receiving modes, low speed and high speed. However, since the modem can usually be set to only one mode, the mode is switched and received according to the transmitting side. There is a need. In that case,
The mode is switched to match signals of different modes, but normal reception is not performed unless processing is performed quickly.

For example, when the DCS which is the low-speed mode arrives while the high-speed reception mode is being set, the modem is switched to the low-speed reception mode based on the determination that the demodulation result is not a significant signal, but the processing is not terminated early. As a result, the leading part of the DSC is lost, and the result is that the complete DCS cannot be received. This is the same as that in the case of waiting for the arrival of a signal in the low-speed reception mode after the CFR transmission, in that quick determination and switching for the arrival of the TRN signal are required, which has been one of the difficulties in designing software.

An object of the present invention is to enable mode switching on the receiving side to be performed appropriately and in a short time, and to reduce the complexity of designing a program and wasting time during communication.

[0019]

According to the present invention, the transmitting side notifies the receiving side that the mode of the signal to be transmitted next is to be switched, and the receiving side switches the mode according to the content of the notification. is there.

Therefore, the receiving side only needs to switch the mode according to the notification, and a complicated program for determining the receiving mode is not required.

[0021]

FIG. 1 is a block diagram showing an embodiment of the present invention.

The facsimile communication apparatus of this embodiment includes a CPU 1 for controlling the entire apparatus, a ROM 2 storing a control program for the CPU 1, a RAM 3 used as a work area of the CPU 1, a document which is read and converted into an electric signal. A scanner 4 for converting, a printer 5 for outputting an image on a recording paper, an operation unit 6 for inputting various keys by an operator, a display unit 7 for displaying various information, a modem 8 for modulating and demodulating transmission / reception data, a line, An NCU 9 for connecting the terminal to a telephone or a modem 8 and an image memory 10 for storing image data. It is to be noted that such a configuration itself is general, and is assumed to be common in each of the following embodiments.

FIG. 2 shows G3 in the first embodiment of the present invention.
FIG. 7 is an explanatory diagram showing a facsimile communication procedure.

On the transmitting side, first, after receiving the CFR normally,
An SMH (set mode to high) signal is transmitted, and an image signal is transmitted at intervals of a margin period (about 75 msec) for switching modes. After transmitting the CFR, the receiving side waits in the low-speed reception mode. When the above-described SMH is received, the modem is switched to the high-speed reception mode within 75 msec, and the next incoming TRN / PIX / RTC signal is transmitted. Execute reception. Therefore, the reception mode determination program only needs to decode the SMH, and does not require a complicated program such as whether or not the signal is a significant signal and whether or not mode switching is necessary.

In the first embodiment shown in FIG. 2, if SMH cannot be received on the receiving side due to poor line quality or the like, the result is that the receiving side continues to wait for a signal in the low-speed receiving mode. The same problem as in the prior art example occurs.

FIG. 3 is an explanatory view showing a communication procedure in a second embodiment in which this is improved.

In this example, when the receiving side receives the SMH normally, the receiving side sends an ACK (acknowledgement) indicating the reception.
Is returned, and the transmission side starts transmitting the image signal in response to the ACK.

Here, the interval of 75 ms is a waiting time for mode switching on the receiving side as described above (the role of the interval of 75 ms is the same hereinafter).

FIG. 4 is an explanatory diagram showing a communication procedure of the third embodiment using SMH even after DCS transmission.

Here, the notification of the modem mode (modulation method and modulation speed) to be transmitted next is sent by the SMH FIF (facsimi
le information field). FIF stands for HDLC (high level data link co.) Of G3 facsimile communication device.
This is one of the fields of the communication format of the "ntrol" structure, and information accompanying the command is defined by the ITU-T recommendation to be put in the FIF.

According to the procedure defined in ITU-T, the setting information of the modem mode on the transmitting side is entered in the DCS FIF. In this embodiment, the information is entered in the SMH FIF. Information on the transmission mode is collected in the SMH FIF, which facilitates understanding and program creation.

When receiving the SMH following the DCS, the receiving side sets the modem to the mode specified by the SMH FIF, and receives the next incoming TRN signal.

Also, SM before TRN / PIX / RTC
The role of H is the same as that of the second embodiment shown in FIG. 3. When the same signal is received, the receiving side transmits ACK, sets the modem to the high-speed reception mode, and sets the TRN / PIX / RTC.
Is received.

FIG. 5 is an explanatory diagram showing a fourth embodiment in which the communication procedure of the improved ITU-T recommended G3 facsimile communication apparatus is applied to full-duplex communication.

The advantage of full-duplex communication over half-duplex communication is
In the case of a facsimile signal, the point is to reduce the communication time of the procedure for a signal reception error.

For example, a case where a reception error occurs in the conventional G3 facsimile communication procedure shown in FIG. 8 will be described. Note that the number of transmissions of each signal is denoted by # (hereinafter, # indicates the number of transmissions of the same signal). In addition, the marks ○ and × shown in the figure indicate whether or not the transmitted signal has been normally received.

If DIS (# 1) cannot be received by the transmitting side, there is no response from the transmitting side, so the receiving side transmits DIS (# 2) again after a 3-second no-signal period. . Next, the transmitting side normally receives DIS (# 2), and returns DCS / TRN (# 1) in response thereto. However, the receiving side cannot receive the same signal, and the receiving side returns again after 3 seconds. DI
Send S (# 3).

On the transmitting side, although the DCS / TRN (# 1) has been transmitted, the DIS (# 3) is returned.
Send CS / TRN (# 2). On the receiving side, DCS
/ TRN (# 2) can normally receive, and in response, returns CFR (# 1). Hereinafter, although the exchange of the procedural signal is continued, the description here is about the time loss at the time of abnormal reception, and the following procedure is omitted.

As described above, when a signal cannot be received, a signal-free period of 3 seconds is set after the signal is transmitted, and a signal having the same content is retransmitted. This is a marginal period for providing the transmission and reception signals, and is nothing less than a measure for preventing collision between transmitted and received signals. Therefore, when a reception error occurs, the time corresponding to the extra period is wasted.

In the full-duplex communication for improving this point, as shown in FIG. 4, signals having the same contents are continuously and repeatedly transmitted until a significant signal is returned from the other party. Absent. Further, when a significant signal is received from the other party, the transmission of the continuous repetitive signal is stopped at that time. However, since the stop is usually not at the time of completion of signal transmission but in the middle of signal transmission, AB for canceling the signal is normally used.
Sends a T (abort) signal and stops.

In full-duplex data communication, it is necessary to keep transmitting a signal at all times in order to ensure synchronization of the communication partner. At this time, it is known that the communication partner can surely receive the signal. When there was a significant signal from Therefore, it is common to repeatedly transmit a signal of the same content until a significant signal is received.

In the fourth embodiment shown in FIG.
On the transmitting side, a series of signals DCS to TR
Respond with N. On the other hand, when the receiving side has finished receiving the TRN (# 1), it can know that the transmitting side has normally received the DIS.

When the receiving side completes the reception of the TRN (# 1), the DIS (# 4) is in the process of being transmitted, so that a notification signal ABT to terminate the DIS (# 4) is transmitted, and then the CFR is repeatedly transmitted. On the transmitting side, when CFR (# 1) is received, transmission of the repeatedly transmitted signal is stopped, and SMH (# 1) is transmitted following ABT. The SMH here can receive the CFR, and indicates that the next signal to be transmitted is in the high-speed mode.

Therefore, when receiving the SMH (# 1), the receiving side stops the transmission of the CFR (# 3) in the middle, and
Following transmission of T, an ACK repetition signal is returned to notify that SMH has been received.

The transmitting side stops transmitting the SMH (# 3) at the time of receiving the ACK (# 1), and after transmitting the ABT, sets a high-speed mode after a margin of 75 ms for switching the mode on the receiving side. Signal TRN / PIX / RTC at
Starts sending.

Since the receiving side knows that the transmitting side has stopped sending the SMH, it can know that the transmitted ACK has been normally notified to the transmitting side.

Therefore, after receiving the ABT, or SMH
If (# 3) is completely stopped on the transmitting side when transmission is completed (in this case, ABT is not transmitted), S
After the stop of the MH (# 3), the modem is switched to the high-speed reception mode to receive the TRN / PIX / RTC.

During reception of TRN / PIX / RTC, a flag (FLG: flat) is used to secure reception synchronization on the transmission side.
g) is desirably sent continuously. Here, the flag is
In data transmission, a signal indicating synchronization or securing or a signal indicating an idle state is used, and a unique bit pattern different from the bit pattern of normally transmitted data is used.

However, in the case of high-speed transmission, a full-duplex communication in the high-speed mode is technically difficult in many cases because the transmission spectrum is used in the entire pass band of the line, depending on the modulation mode. During image signal transmission, N
Except for an error retransmission method that requires transmission of an ACK (non acknowlegement) signal, full-duplex communication is not necessarily required.

In the error retransmission system, the ITU-
ECM (error correct) already standardized in T Recommendation
If the error frame is retransmitted in page units as in (ion mode), the feedback channel of the NACK signal is not necessary during the transmission of the image signal, so that the full-duplex communication method is not necessarily required.

Therefore, in the present embodiment, the communication mode in the high-speed mode is not limited to full-duplex communication or half-duplex communication.

Upon transmitting the RTC indicating the end of the transmission of the image signal, the transmitting side transmits the EOP. EOP means that all communication is terminated, and transmission of EOP is repeated until the MCF can be correctly received from the other party.

On the other hand, the receiving side returns an MCF to EOP (# 1), and a signal D for disconnecting the line of the other side is output.
When the CN is received, the line is released.

The method of using the signal and SMH for switching the modulation mode, which is the gist of the present invention, in the full-duplex and half-duplex or partial full-duplex data communication has been described above. Here, SMH is assumed to be a signal coded in the HDLC format, like other procedure signals such as DIS and DCS.

In order to notify the other party of the information of the transmission mode to be changed in detail, data for that purpose is required, and for that purpose, it is necessary to perform data transmission in a coded format.

That is, when there are a plurality of transmission modes and one is selected from them, it is necessary to notify which mode is to be selected, and coding is indispensable. A simpler signal would suffice if only the mode was switched from one to the other.

FIG. 6 shows a fifth embodiment in which the above-mentioned SMH is replaced by a simple signal. Here, the above-mentioned flag (FLG) is used as a signal for that purpose.

The flag is usually added to the beginning of data, between data or between data frames. In this case, even after data transmission is completed, a flag sequence is transmitted, and the flag has the meaning of switching the transmission mode. Things.

In FIG. 6, a signal TRN from the transmission side is shown.
The signal transmission / reception sequence up to the point of receiving (# 1) and returning the CFR, and after transmitting the TRN / PIX / TRC on the transmission side, are the same as in the fourth embodiment of FIG.

Accordingly, only the parts different from the fourth embodiment of FIG. 5 will be described here.

Upon receiving the CFR (# 1), the transmitting side stops the transmission of the TRN (# 2), and continues the ABT followed by the FBT.
Send LG continuously. On the receiving side, when recognizing the continuous transmission of the FLG, it is possible to confirm that the CFR has been correctly received by the transmitting side.
After the ABT, an ACK repetition signal is transmitted.

The transmitting side determines that the system for switching to the high-speed mode has been prepared by returning the ACK from the receiving side, stops the continuous transmission of FLG, and sets a time 75 for switching.
The transmission of the image signal is started after a non-signal time of ms.

On the other hand, the receiving side can know that the returned ACK has been correctly received due to the FLG transmission stop on the transmitting side.
After transmitting the BT, the modem is switched to the high-speed reception mode to receive the image signal.

The following operation is the same as that of the fourth embodiment shown in FIG.

The embodiment in which the flag has the meaning of mode switching has been described above by taking full-duplex communication or partial full-duplex communication as an example. In half-duplex communication, the flag is used in a similar manner. It is possible. Further, as a similar use of the flag in the half-duplex communication, in each of the embodiments of FIGS. 2 to 4, the SMH part may be replaced with the flag continuous transmission for a certain time.

[0066]

As described above, according to the present invention,
By notifying the receiving side of switching the transmission mode to the receiving side, the receiving side can uniquely switch the mode without being confused in determining the mode selection of the modem. Can definitely be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a communication procedure according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a communication procedure according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a communication procedure according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a communication procedure according to a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a communication procedure according to a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a communication procedure in a conventional example.

FIG. 8 is an explanatory diagram showing a problem in half-duplex communication in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... ROM, 3 ... RAM, 4 ... Scanner, 5 ... Printer, 6 ... Operation part, 7 ... Display part, 8 ... Modem, 9 ... NCU, 10 ... Image memory.

──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshio Yoshiura, Inventor 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazutaka Matsueda 3- 30-2, Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Fumiyuki Takiguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toru Maeda 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideki Shimizu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Sadasuke Kurabayashi 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Motoaki Yoshino 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kazuto Yanagisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Naoji Hayakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-5-114982 (JP, A) JP-A-63-171042 ( JP, A) JP-A-63-288543 (JP, A) JP-A-8-6099 (JP, A) JP-A-8-70336 (JP, A) JP-A-5-284322 (JP, A) Hei 4-320155 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 29/00 H04N 1/32 H04L 1/00

Claims (2)

(57) [Claims] 1. A Oite to one data communication apparatus for performing transmission data Den using a plurality of modulation mode during a communication period, prior to the switching of the modulation mode on the transmission side,
Notifying means for notifying the receiving side of the switching of the modulation mode
A signal for a notification of switching of the modulation mode,
Signal indicating idle state or signal for synchronization
Data communication device which is a degree. 2. The data communication apparatus according to claim 1, wherein the modulation mode is a transmission rate and / or a modulation method.