JPH06125372A - Preamble time control system - Google Patents

Abstract

PURPOSE:To prevent interruption of a circuit because of failed synchronization by providing a preamble controller extending a preamble time when a procedure control signal is sent again to the system. CONSTITUTION:A preamble and procedure control signal transmitter 21 sends a preamble based on a preamble time outputted from a preamble time revision device and sends a procedure control signal succeedingly. A reply reception confirmation equipment 22 monitors whether or not a reply signal from an opposite terminal equipment is received or a preceding procedure control signal is sent again. A preamble time revision device 23 is started by expiration signal from the device 22 or a detection output of the procedure control signal sent again and outputs a prescribed preamble time or a sum of a prescribed to the preamble time, or obtains a preamble time from a preamble table based on number of times of re-transmission and outputs the obtained time. Thus, the preamble time is extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preamble time control system in a communication device such as a facsimile, and particularly controls a preamble time added before a procedure control signal to achieve both reduction of transmission time and reliability of communication itself. The present invention relates to a preamble time control method that can be performed.

[0002]

2. Description of the Related Art Conventionally, the transmission control procedure of G3 facsimile has been standardized by CCITT recommendation, and the procedure control signal for controlling this procedure is transmitted using a modem with a transmission speed of 300 bps or an optional modem of 2400 bps. Its format is also defined.

FIG. 2 is an explanatory diagram showing the format of the procedure control signal. The signal is divided into a preamble part and a binary control signal part. The preamble portion ensures that, for example, the echo suppressor is adjusted to the proper state so that the data that follows can be received correctly. This preamble is a continuous transmission of HDLC flag F of 1 second ± 15% when a 300 bps modem is used.
In case of 0 bps, recommendation T. 4 is a training sequence defined in 4.

The binary control signal portion follows the format of the HDLC frame, and has a flag F and an address A.
(Normally all 1), Control C ("1100X00
0 "pattern, where X is 1 only in the final frame), a facsimile control field FCF (the first 8 bits of the I field of HDLC, which represents the type of procedure control signal), a facsimile information field FIF (addition of functions etc.) Information etc.) and a frame check sequence FCS.

As described above, the preamble time is defined by the standard, and a considerable amount of transmission time is spent only with this preamble. However, in reality, some terminals can even synchronize with a shorter preamble. In JP-A-1-200780, attention is paid to this point, and a mode using a short preamble is provided as a non-standard function, and if the result of negotiation is that the other party also has the same mode, the procedure control signal is transmitted with a short preamble. It is suggested to do so.

[0006]

In the method using the short preamble as the non-standard function as described above, the communication cannot be performed unless the other party has the same function, and when communication is performed through a noisy line or the like. In addition, since the preamble is short, there is a problem that even if the procedure control signal is repeatedly retransmitted, the synchronization cannot be established and the communication is interrupted.

An object of the present invention is to solve the problems of the prior art as described above, and to obtain a preamble time control system which achieves both reduction of transmission time and improvement of communication reliability in a communication device such as a facsimile. It is in.

[0008]

SUMMARY OF THE INVENTION The present invention provides a communication device for adding a preamble to a procedure control signal for transmission,
When the procedure control signal is retransmitted, preamble time control means for lengthening the preamble time is provided.

[0009]

By such means, by using a preamble shorter than before, the transmission time is shortened, and when the transmission of the procedure control signal fails, the preamble is lengthened and retransmitted. Will be transmitted more reliably.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an example of a facsimile apparatus to which the present invention is applied. The CPU 1 controls the entire facsimile apparatus and processes a facsimile transmission control procedure. RAM2 is a work area used by the control program. The operation display device 3 includes a switch for inputting various operation instructions or a telephone number, including a reception switch, and a display device such as an LCD or LED.

The reading device 4 is a device for reading a set document by an image sensor or the like and generating image information. The printing device 5 is a device that prints the received image information on paper. The image processing device 6 is a device that performs encoding and decoding for compressing the image information generated by the reading device 4 or expanding the received information into printable information.

The image storage device 7 is for storing image information. The ROM 8 stores a program for controlling the entire facsimile. The communication control device 9 has a built-in CPU for internal processing and a ROM storing a program for communication control, and is, for example, a device that executes a link level transmission control procedure and transmits a command or image data. .

The modem 10 has a low speed mode (for example, V21) for commands and a high speed mode (V21) for image data.
27ter, V29, V33, V17, etc.) and modulates commands and image data from the communication control device 9 according to the modulation methods defined by the respective standards, or demodulates the received signal. Network control device 11
Under the control of the communication control device 9, the automatic call originating / receiving operation such as calling to the public network such as a telephone line, dialing, disconnection and the like is executed. The system bus 12 connects each device in the facsimile device.

Next, the outline of the operation will be described. FIG. 3 is a functional block diagram showing the relationship of each functional element in the embodiment. The preamble time setting means 20, when a procedure control signal transmission request is issued, sets a predetermined preamble time,
Alternatively, the preamble time registered by the preamble time registration means 24 is output.

The preamble and procedure control signal sending means 21 sends a preamble based on the preamble time output from the preamble time setting means 20 or the preamble time changing means, and then sends the procedure control signal. The response reception confirmation means 22 monitors whether a response signal from the partner terminal has been received or whether the previous procedure control signal has been retransmitted.

The preamble time changing means 23 is activated by a timeout from the response reception confirming means 22 or detection output of the retransmitted procedure control signal, and outputs a predetermined preamble time (for example, standard time according to the standard), or A predetermined value is added to the previous preamble time and output, or the preamble time is obtained from the preamble table based on the number of retransmissions and output.

The preamble time registration means 24 registers the preamble time at that time in, for example, a preamble memory according to the response reception output from the response reception confirmation means 22. Even if the preamble time registration means 24 is not provided, the effect of the present invention can be obtained. Further, each of these means is realized by a program in the communication control device 9.

Next, details of the operation of the embodiment will be described. FIG. 4 is a flowchart on the transmitting side when the present invention is applied to the facsimile transmission procedure phase B (transmission preparation procedure). First, in step S10, a facsimile makes a call. In step S11, DI from the other terminal
Wait until the S signal is received. If the DIS signal does not come here, it times out in 35 seconds and disconnects the line.
When the DIS signal is received, the DIS signal is analyzed and a DCS command is created based on the analysis.

In step S12, the preamble time is set to 300 ms, for example. In step S13, the preamble signal is transmitted for the preamble time set in step S12, followed by DCS.
Send a signal frame. In step S14,
Switch the modem to high speed mode and use the DCS signal for 75
training sequence with ms intervals, and T
Send a CF signal.

In step S15, a timer (for example, 3 seconds) is started. In step S16, it is checked whether or not the response signal is received, and if not received, the process proceeds to step S17. In step S17, it is checked whether or not the timer started in step S15 has timed out. If not, the process returns to step S16. However, if it times out, the process proceeds to step S18. If the response signal is not returned within the predetermined time, it means that there is a high possibility that the DCS signal transmitted in step S13 is not correctly received by the partner terminal. In step S18, the preamble time is changed, the process returns to step S13, and the procedure control signal is retransmitted. The way to change is, for example, change to the standard time of 1 second.
It is possible to employ a method of adding ms, obtaining a preamble time from the preamble table based on the number of retransmissions, and changing to the value.

When any response signal is received in step S16, the process proceeds to step S19, and if it is the CFR signal indicating that the preparation for reception is completed, the phase B is ended and the facsimile message of the phase C is transmitted. Transition. When a signal other than the CFR signal, such as the training failure signal FTT, is received, the process returns to step S13 as shown in the figure and the training is performed again.

FIG. 5 shows a facsimile transmission procedure phase D.
6 is a flowchart on the transmitting side when the present invention is applied to (procedure after message transmission). First, in step S20, image information is transmitted. (The procedure before that is not shown.) In step S21, the preamble time is set to 300 ms, for example. Step S
In 22, the preamble signal is transmitted for the preamble time set in step S21, and then the EOP signal frame indicating the last page is transmitted.

In step S23, a timer (for example, 3 seconds) is started. In step S24, it is checked whether or not the response signal is received, and if not received, the process proceeds to step S25. In step S25, it is checked whether or not the timer started in step S23 has timed out. If not, the process returns to step S24. However, if it times out, the process proceeds to step S26. If the response signal does not come back within the predetermined time, it means that there is a high possibility that the EOP signal sent in step S22 is not correctly received by the partner terminal. In step S26, the preamble time is changed, the process returns to step S22, and the procedure control signal is retransmitted. The way to change is, for example, change to the standard time of 1 second.
It is possible to employ a method of adding ms, obtaining a preamble time from the preamble table based on the number of retransmissions, and changing to the value.

When any response signal is received in step S24, the process proceeds to step S27, and if it is the MCF signal indicating that the reception is completed, the phase D is ended and the disconnection process of the phase E is performed. Also, MC
In the case of signals other than the F signal, error processing corresponding to the respective signals is performed, but since this part is the same as the conventionally known procedure, detailed description will be omitted.

FIG. 6 shows a facsimile transmission procedure phase D.
6 is a flowchart on the receiving side when the present invention is applied to (procedure after message transmission). First, in step S30, after receiving the image information, the EOP signal indicating the last page is received. (The procedure before that is not shown.) In step S31, the preamble time is set to 300 ms, for example. In step S32, the preamble signal is transmitted for the preamble time set in step S31, and then the MCF signal frame indicating that the reception is completed is transmitted.

In step S33, a timer (for example, 6 seconds) is started. In step S34, it is checked whether or not the command signal is received, and if not received, the process proceeds to step S35. In step S35, it is checked whether or not the timer started in step S33 has timed out. If not, the process returns to step S34. However, if a time-out occurs, the process moves to error processing (completion of communication). This means that if the transmitting side does not receive the MCF for the EOP, it will retransmit the EOP within a predetermined period.
DC that indicates disconnection within a predetermined period even when F is received
This is because a signal such as N should be transmitted.

If any signal is received in step S34, the process proceeds to step S36. In step S36, it is checked whether or not the EOP signal is received, and if it is received, the process proceeds to step S37. Here, the EOP has already been received once in step S30, which means that the EOP has been retransmitted. This indicates that there is a high possibility that the MCF sent in step S32 is not correctly received by the partner terminal.

Therefore, in step S37, the preamble time is changed, and the process returns to step S32 to retransmit the procedure control signal. For example, the standard time is changed to 1 second, 400 ms is added to the previous value, the preamble time is calculated from the preamble table based on the number of retransmissions, and the value is changed to that value. It is possible to

In step S36, the received signal is EOP.
If the signal is any other signal, the process proceeds to step S38. If the signal is a DCN signal indicating disconnection, the process proceeds to the disconnecting process in step S39, and in the case of other signals, error processing corresponding to that signal is performed. However, since this step is the same as the conventionally well-known procedure, detailed description thereof will be omitted.

Next, details of the operation of another embodiment will be described. FIG. 7 is a flowchart on the transmission side when the present invention is applied to the facsimile transmission procedure phases C and D (procedures after message transmission). This embodiment shows an example of changing the preamble time using the preamble table when transmitting a plurality of pages.

First, in step S40, the RAM 2
The values of the confirmation flag and the retransmission counter stored in the predetermined area of are reset to 0. In step S41, the image information is transmitted. In step S42, it is checked whether or not the image information transmitted in step S41 is the final page. If the image information is the final page, the process proceeds to step S21 in FIG. 5, for example. However, if it is not the final page, the process proceeds to step S43, and it is checked whether or not the confirmation flag is 1. If the confirmation flag is 0 here, the process proceeds to step S45, but if it is 1, the process proceeds to step S44.

In step S45, first, the value of the retransmission counter is read, the preamble table is looked up using this value as an address, and the preamble time is obtained. For example, since the value of the retransmission counter is 0 at the beginning, 300 ms is set as the preamble time. On the other hand, step S
At 44, the value stored in the preamble memory is read and set as the preamble time.

In step S46, step S4
4 or the preamble signal is transmitted for the preamble time set in step S45, and then the MPS signal frame indicating the end of the midway page is transmitted.

In step S47, a timer (for example, 3 seconds) is started. In step S48, it is checked whether or not the response signal is received, and if not received, the process proceeds to step S49. In step S49, it is checked whether or not the timer started in step S47 has timed out. If not, the process returns to step S48. However, if it times out, the process proceeds to step S49. If the response signal does not come back within the predetermined time, it means that the MPS signal transmitted in step S46 is highly likely not correctly received by the partner terminal. In step S50, 1 is added to the value of the retransmission counter, and step S4
The preamble time is changed by returning to 5 and redrawing the preamble time from the preamble table,
The procedure control signal is retransmitted.

When any response signal is received in step S48, the process proceeds to step S51, and the preamble time set at this time is written in the preamble memory in step S51. Further, in step S52, the confirmation flag is set to 1. After this, the detailed procedure is omitted, but the process returns to step S41 of phase C and the message of the next page is transmitted.

By such processing, the preamble time at the time of successful transmission of the procedure control signal is registered, and the preamble time is determined by using the value at the time of transmission of the next page. Sometimes the shortest preamble time needed from the beginning can be used.
In the above embodiment, the table is used as the preamble time changing means, but after the second time, a method of changing to a predetermined value or adding a predetermined value to the previous value can be adopted. Is.

Although the four embodiments have been described above, the following modifications are also possible. Although the embodiments of FIGS. 4 and 5 have been described as independent processes, the present invention can be applied to all process control signal transmission processes of a facsimile, in which case the preamble time setting process, for example, FIG. Step S12, step S2 in FIG.
It is also possible to perform 1 and the like only at the time of transmitting the first procedure control signal in communication, omitting the second and subsequent times, and providing only the process for changing the preamble time. By doing so, it is possible to use the preamble time when the message succeeded last time in the transmission of the message of one page, and when it fails, the preamble time is further changed.

ROM for the preamble table
May be stored in, but R with backup function
It may be stored in the AM so that the user can arbitrarily set it. Regarding the set time, for example, the first preamble time is set to 850 ms which is the lower limit of the standard value,
At the time of retransmission, the standard value may be 1 second, or the standard value upper limit may be 1.15 seconds.

Regarding the registration of the preamble time, for the partner terminal registered in the speed dial, for example, the preamble time registered in the embodiment of FIG. 7 is stored correspondingly to the terminal, and the preamble time of the next communication is stored. It may be used as an initial value. In this case, if the increase amount of the preamble time at the time of retransmission is reduced, the preamble time closer to the shortest necessary time is required, which is more effective.

Although the facsimile has been described as the embodiment of the present invention, the present invention can be applied to a general communication apparatus for transmitting a signal with a preamble added.

[0041]

According to the preamble time control method of the present invention, there is an effect that both reduction of the preamble transmission time and improvement of communication reliability in a communication device such as a facsimile can be achieved at the same time.

Even if the other party is a model requiring a long preamble time, such as a standard, the situation of communication interruption can be avoided, so that the present invention can be applied to communication with any model. There is also an effect.

[Brief description of drawings]

FIG. 1 is a block diagram of a facsimile apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram showing a format of a procedure control signal.

FIG. 3 is a functional block diagram showing a relationship between respective functional elements.

FIG. 4 is a flowchart of a transmitting side of phase B.

FIG. 5 is a flowchart on the transmitting side of phases C and D.

FIG. 6 is a flowchart on the receiving side of Phase D.

FIG. 7 is another example of a flowchart on the transmission side of phases C and D.

[Explanation of symbols]

1 ... CPU, 2 ... RAM, 3 ... Operation display device, 4 ... Read device, 5 ... Printing device, 6 ... Image processing device, 7 ... Image storage device, 8 ... ROM, 9 ... Communication control device, 10 ... Modem,
11 ... Network control device, 12 ... System bus

Claims (4)

[Claims] 1. A preamble in a communication device for adding a preamble to a procedure control signal and transmitting the procedure control signal, wherein when the procedure control signal is retransmitted, preamble time control means is provided for lengthening the preamble time. Time control method. 2. The preamble time control method according to claim 1, wherein the preamble time control means sets a preamble time shorter than a standard time at the first transmission of the procedure control signal. 3. The preamble time control method according to claim 1, wherein the preamble time control means sets the preamble time longer than the previous time each time the procedure signal is retransmitted. 4. When the transmission of the procedure control signal is successful, a registration means for registering a preamble time at that time is provided, and is registered in the registration means as a preamble time at the next transmission of the procedure control signal. The preamble time control method according to claim 1, wherein the preamble time is used.