JPS62256569A - Facsimile transmission system - Google Patents

Abstract

PURPOSE:To increase the signal transmission speed of a picture signal of facsimile transmission and make this speed high-precision by monitoring both of the number of correctly received patterns and an equalizing error to discriminate whether training is successful or not. CONSTITUTION:Functions of MODEMs in the transmission side and the reception side are set up to the highest, and training of MODEMs is immediately started when a station to be called is discriminated. The function provided in the transmission side is converted to a frame and is repeatedly transmitted as training data. When the reception side correctly receives this data converted to the frame prescribed number of times or more, the reception side judges training successful to inform the transmission side of the completion of reception preparation. In this case, the function provided in the reception side is reported simultaneously. Thus, information is efficiently exchanged between the transmission side and the reception side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a facsimile transmission system, and more particularly to a method for determining the success or failure of training in a facsimile transmission system.

In general, in a system that performs facsimile transmission using a line such as a telephone exchange network, a modem, a modem, which has multiple signal transmission speeds is used to transmit a facsimile between a facsimile transmitter and a receiver. The image signal is transmitted by selecting at the start of communication the transmission speed that allows the image signal to be transmitted at the highest speed and with the least distortion.

Figure 6 shows the transmission procedure of the conventional facsimile transmission method. The numbers indicate the signal transmission speed.

The transmission procedure of the conventional example shown in FIG. 1 will be explained below.

77 ,,"j' IJ equipment ffi! FAX 1 is L as shown
Ugly telephone.

Therefore, the family receiving device FAX can be sent via the telephone exchange network.
Call 2.

(2) The facsimile receiving device FAX2 generates a single tone signal of 2.1 ohtz via the modem MOD2, and returns a called station identification signal indicating that the called terminal is the facsimile receiving device FAX2.

■Next, the facsimile receiving device F A The function identification signal such as
Transmit to the side.

(2) The facsimile transmitting device FAX1 confirms that the connected party is a facsimile machine based on the received called station identification signal, and waits for reception of the function identification signal. Based on the function identification signal received next, the facsimile transmitter [FA
Xl extracts functions that match those of its own device, and selects the function that can be transferred in the shortest time. For example, both the sending and receiving sides.

The signal transmission speed of the modem is 9 + 600 bps
, 7.200 bps, 4+ 800 bps, 2+40
If the type of image encoding method includes a two-dimensional encoding method and a -dimensional encoding method, the facsimile transmitting device FAX1 has a speed of 9.60Q bps.
The two-dimensional encoding method is selected at the signal transmission rate. Regarding each selected function, the facsimile transmitting device FAXI notifies the facsimile receiving device FAX2 that it is a function that will ultimately be used for transmission (shown as command information).

■ After notifying the command information, the facsimile transmitting device FAX1 sends a training signal from the modem MODl at the signal transmission speed indicated in the command information in order to set up the modem MOD2 on the receiving side to a state in which it can receive data. let The facsimile receiving device FAX2 selects the receiving function of its own device specified in the receiving command signal and puts it into operation. Modem MOD2 sets up its own device based on the training signal from modem MODI. or,
The modem M OD I subsequently signals to check the training status. The modem MOD2 reproduces and outputs the signal to the facsimile receiving device FAX2. The facsimile receiver fiFAX2 uses this reproduced output signal to
It is determined whether the image signal can be received with fewer errors at that speed.

■ If it is determined that reception is not possible, the facsimile receiving device F
AX2 sends a signal to the facsimile transmitter FAXI indicating that the training has failed. Facsimile transmitter FA
When the XI receives this signal, it notifies the receiving side of command information to perform a so-called fallback to lower the signal transmission speed by one step.

After that, perform the above steps at the fallback signal transmission speed■
Repeat steps and ■.

(2) If it is determined that the image signal can be received with fewer errors at that speed, the facsimile receiving device 1FAX2 transmits a reception preparation completion signal to the facsimile transmitting device [FAX1].

■ Sends reception ready signal to facsimile transmitter FAX1
When the facsimile transmitter receives the image signal, the facsimile transmitter [FAXI] transmits the image signal at the corresponding signal transmission speed. After that, an image transmission end signal is sent from the transmitting device FAXI to the receiving device FAX2.
, the receiving device FAX2 returns a reception confirmation signal to the transmitting device FAX1.

The method described above complies with CCITT Recommendation T.30, and in addition to transmitting image signals, various information exchanges are performed using a low-speed (300 bps) modem. Therefore, it has the disadvantage that it takes time to determine the signal transmission rate.

Purpose The present invention has been made in view of one or more points, and it is possible to eliminate the drawbacks of the prior art as described above and to determine the signal transmission speed of an image signal in facsimile transmission in a short time and with high accuracy. The purpose is to provide a possible facsimile transmission method.

Configuration In order to achieve the above-mentioned object, the present invention repeatedly transmits the same pattern as modem training data from a transmitting device, while the receiving device calculates the number of correctly received patterns and the convergence state of the equalizer. We provide a facsimile transmission system that monitors both to determine the success or failure of training.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one embodiment of a facsimile transmission system based on the present invention. According to this method, modem functions on both the sending and receiving sides are set up to the highest level, and when the called station is identified (step a), modem training is suddenly started (step b). When the receiving side receives this framed data correctly a predetermined number of times, it considers the training to have been successful and is ready to receive it. The sending side is notified of the completion (step C), and at the same time, the functions of the receiving side are also notified. In this way, information exchange between the sending side and the receiving side is performed efficiently.

In this case, if there is distortion in the line, the above frame reception may fail at the beginning of training. Even if the automatic equalizer works well and the image signal is sufficiently delayed at the transmission speed at the end of training, due to an initial reception error, it is judged that the number of received patterns is insufficient, and it is considered as training, resulting in a so-called fall pack. becomes. The convergence state of the automatic equalizer can be determined by looking at the equalization error. The equalization error, which became large at the beginning of training, becomes smaller as the equalizer converges, as shown in FIG. The way this convergence occurs depends on the degree of distortion in the line; when the distortion is small, it converges quickly, as shown by the solid line in Figure 2, but when the distortion is large, the
As shown by the dotted line in the figure, the convergence is slow. Furthermore, in extreme cases, it may not converge.

When a framed data pattern such as that described above is used as check data for modem training, the probability of correctly receiving a frame varies depending on the convergence state of the equalizer. At the beginning, when equalization is not sufficiently performed, there is a high probability that frame reception will fail, but thereafter, as equalization progresses, this probability becomes significantly smaller. When the number of received frames does not reach a predetermined number, the equalization error is checked and if it is below a certain level, it is possible to sufficiently transmit the image signal even at that transmission speed.

At this time, it is determined that the training was successful.In this way, according to the method of the present invention, by monitoring both the number of received frames and the equalization error, it is possible to accurately judge the transmission ability of the image signal. This makes it possible to prevent excessive fallbacks from occurring.

FIG. 3 shows an embodiment of a facsimile transmission system constructed according to the present invention.According to this system, an operator operates a telephone set 1 to connect a facsimile receiving device to a called side. The telephone number is supplied to the network control device 2. The network controller M2 supplies a dialing signal to the exchange 3 to call the other party's terminal at the receiving facsimile machine.

Line circuit 4 is activated by a call signal from exchange 3.

Make the line available for calls. Further, the connection detection circuit 5 monitors the signal line of the line circuit 4, and when one line is connected, detects this and notifies the main control unit 6.

When the main control section 6 receives this signal, it controls the line control section 7 to transmit the above-mentioned called station identification signal. The called station identification signal generated from the modulation circuit 8 is supplied to the telephone set 1 via the line circuit 4, the exchange 3, and the network control device 2.

The operator of the facsimile machine [FAXl] on the transmitting side confirms the called station identification signal and operates the key 8 to start transmitting the facsimile image signal. The operation of key 8 is
Activate the transmission function of the main control section 9. Although not shown in the figure, upon operation of this key 8, the network control device 2 switches the line from the telephone 1 to the facsimile transmitting device FAX1.

The main controller 9 supplies the line controller 11 with information indicating the functions of its own facsimile transmitter 1FAX1 and modem MODI. This information is framed as shown in Figure 4, and details of the frame can be found in CCITT Recommendation T.3.
0.

The line control unit 11 uses the received information to
It knows the maximum transmission speed of OD1 and instructs it to the modulation device 14 through the signal line a. The modulator [14 begins modem training at the indicated signal rate. The main control unit 6 on the receiving side also provides the functions of its own facsimile receiving device FAX2 and modem MOD2 to the line control unit 7, and the modem M
Set the OD2 to receive at its highest speed so that training can begin at any time.

Here, both the sending and receiving speeds are 9.6QQbp
s, training is performed at 9*600 bps. After training is completed, TCP (Training Check Field) data is sent to check whether the receiving side can receive sufficient data. In Recommendation T, 30, a "0" is sent for 1.5 seconds, but instead, the present invention sends the framed capability information described above. T
Just as rOJ is repeated in the case of CP, in the present invention, the success or failure of training is determined by repeatedly transmitting functional information and determining how many errors there are in all transmitted frames. This is done by the quality extraction circuit 15. The quality extraction circuit 15 further includes an equalization monitor circuit as shown in FIG. This calculates the power of the equalization error, compares the result with a certain reference value, slices it, and integrates it to monitor the progress of equalization.

That is, as shown in FIG.
3a, an automatic equalization section 13b, a determination section 13c, a coding section 13d, and two subtraction sections 13e and 13f. Further, an equalization error monitor circuit 30 connected to this demodulator 13 and provided within the quality extraction circuit is
A power calculation section 30a to which signals from the subtraction sections 13e and 13f of the demodulator 13 are input, and an amplification coefficient creation section 30b.

Multiplying section 30c, integrating circuit section 30d, and slicing section 30
e, and its monitor output is taken out from the connection point between the amplification coefficient creation section 30b and the integration circuit section 30d.

Effects As described in detail above, according to the present invention, the line can be used effectively by accurately determining the signal transmission speed of an image signal from the distortion state of the line and the equalization ability of the automatic equalizer for it. That is, it is possible to reduce the amount of time a conventional low-speed modem is used and improve line usage efficiency.

Although specific embodiments of the present invention have been described in detail above, the present invention should not be limited only to these specific examples, and various modifications may be made without departing from the technical scope of the present invention. Of course, it is possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one example of a specific implementation of the facsimile transmission system based on the present invention, FIG. 2 is a graph diagram showing the convergence state of equalization error, and FIG. 3 is an embodiment of the present invention. FIG. 4 is an explanatory diagram showing framed data, FIG. 5 is a detailed diagram of a part of the system in FIG. 3, and FIG. 6 is a conventional facsimile transmission system. FIG. 2 is an explanatory diagram showing a facsimile transmission method. (Explanation of symbols) 13: Demodulator 15: Quality extraction circuit 30: Equalization error monitor circuit Figure 1 Transmission S Receiving side Figure 2 Time Figure 6 Transmitting side Receiving side

Claims (1)

[Claims] 1. In a facsimile transmission method in which facsimile transmission is performed between a transmitting device and a receiving device, the transmitting device repeatedly transmits a preset pattern as modem training data, while the receiving device transmits a pattern that has been correctly received. A facsimile transmission method characterized in that the success or failure of training is determined by monitoring both the number and the convergence state of an equalizer.