JPH0562855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal demodulation method, and particularly to a signal demodulation method suitable for facsimile transmission control using a modem.

Conventional technology Conventional facsimile communication is based on CCITT recommendation T30.
This was carried out as follows, in accordance with the transmission control procedure determined by .

That is, as shown in Figure 3, first the transmitting side makes a call to the receiving side, and when the line is closed, the receiving side sends a CED (Called Station Identification) signal and
Sends a DIS (digital identification) signal. In response, the transmitting side sends out a DCS (digital command) signal and, in order to train the modem, sends out a TCF (training check) signal, that is, fast training data '0'. The receiving side is
Training is performed based on the TCS, and if the training is successfully completed, a CFR (reception readiness confirmation) signal is sent out. After that, the transmitting side sends out image information (PIX) after a short retraining process. After sending one page of image information, if the next page exists, the sending side sends an MPS (multipage) signal, receives an MCF (message confirmation) signal from the receiving side, and performs retraining again. Then, the next page's image information is sent out.

The above is an overview of facsimile communication in accordance with CCITT recommendation T30, and conventional facsimile equipment is
Image information was transmitted by repeating this operation. In FIG. 3, the shaded portions are signals that use a high-speed modem, and the other portions are signals that use a low-speed modem.

Further, the various signals mentioned above are modulated or demodulated by a modulation/demodulation device as shown in FIG. In the figure, 50
is a modulator, 51 is a demodulator, 52 is an amplifier, and 53 is a hybrid transformer. This modulator/demodulator uses TCF in the above training sequence.
The AGC gain set, equalizer parameter set, carrier wave recovery, and timing recovery parameters required for demodulation are set.

Now, with the conventional facsimile machine mentioned above,
Even after the above training sequence is completed, approximately
The problem is that idling data of about 500 ms is sent out, and it is considered as part of a training sequence and waits for the reliability of the received data to increase, resulting in wasted transmission time. It was hot.

On the other hand, in conventional facsimile communication, the CFR sent from the receiving side between the TCF and image information is routed to the demodulator by the hybrid transformer 53, and the demodulator for the high-speed modem is activated by the looped CFR. Therefore, the parameters once set in the above-mentioned training sequence are reset, and the parameters are reset during retraining before transmitting the image information. A similar thing can happen during MPS reception and MCF transmission when operations such as image information reception - MPS reception - MCF transmission - image information reception are performed, but the parameters once set in the training sequence are reset. Therefore, the parameters set in the training sequence will be used in subsequent communications.
There was also the problem that it could not be fully utilized, especially during retraining.

Purpose An object of the present invention is to provide a signal demodulation method that can eliminate such conventional problems, improve transmission characteristics, and shorten transmission time in facsimile communications.

Configuration The present invention attempts to remember these parameters memorized when receiving a high-speed modem signal until the next high-speed modem signal is received. In other words, the parameters are not reset even if another signal (in the case of a G facsimile machine, a low speed modem signal) is received before the second high speed modem signal is received.

Therefore, if some carrier component is detected on the line, first it is determined whether the high-speed modem signal is a low-speed modem signal, and if it is determined that it is a low-speed modem signal, it is activated until it is determined that it is a low-speed modem signal. Replace the above parameters on the high-speed modem side (at this point, the previously memorized values are disturbed) with the above parameters that you remembered before, as if the high-speed modem side was not operating at all. This is what it means.

In order to achieve the above object, the present invention has a first modulation/demodulation method and a second modulation/demodulation method that have reception parameters that change depending on the transmission characteristics of a transmission path, In a signal demodulation method in which signal demodulation is performed by switching the reception parameters according to a predetermined transmission control procedure, the reception parameters according to the first modulation and demodulation method are held;
When the next signal arrives, it is detected whether it is a received signal of the first modulation/demodulation method or a reception signal of the second modulation/demodulation method, and when it is determined that the signal arrives by the second modulation/demodulation method, the first modulation/demodulation method held The method is characterized in that signal demodulation is performed by replacing the received parameters with the received parameters.

Hereinafter, the configuration of the present invention will be explained using examples.

FIG. 1 is a processing flowchart of a signal demodulation method showing one embodiment of the present invention.

The signal demodulation method of the present invention will be explained below with reference to the processing flowchart shown in FIG.

First, when a carrier (transport path) component is detected (step 101), the FAST AGC circuit performs gain adjustment (step 102). Next, it is determined whether the signal is a high-speed modem signal or a low-speed modem signal (step 104,
105), when the signal is a low-speed modem, the high-speed modem parameters are held. If it is a high speed modem signal, a receiving operation is performed (step 106). The process of step 106 is repeated until reception is completed (step 107). When the reception is completed (step 107''), the high-speed parameters are held and used for the next high-speed modem reception.The determination at processing step 104 is made by internally determining whether a flag is set. Further, the above-mentioned held parameters are stored in a memory or the like.

By doing this, during the training sequence period of the modem that comes when the next PIX reception occurs, training reception can be performed from the values experienced in the past, rather than from a state where nothing is known (reset state). The training converges faster in time than in the former case. As a result, the reliability of the received data is increased and there is no need to send out idle data. An example of this is shown in FIG.

FIG. 2a is an example of conventional training reception, and FIG. 2b is an example of training reception according to the present invention. The slope of convergence differs depending on line characteristics. In FIG. 2a, training is performed after resetting, so the training starts from 0, but in FIG. 2b, the training starts from the previously memorized value, so it does not reach 0. Here, 2, 3, 4, 5
is training data, then idling data, and finally user data.

Effects As explained above, according to the present invention, the parameters set during training are retained and the retained parameters are used in subsequent communications, especially during retraining, so transmission characteristics can be improved in facsimile communications, etc. , the transmission time can be shortened and the reliability of demodulation can be improved.

[Brief explanation of the drawing]

Fig. 1 is a processing flowchart of a signal demodulation method showing an embodiment of the present invention, Fig. 2 is a diagram showing an example of convergence of transmission data according to the invention, and Fig. 3 shows a conventional basic transmission control procedure. The sequence chart in FIG. 4 is a block diagram of a conventional modulation/demodulation device. 50: Modulator, 51: Demodulator, 52: Amplifier,
53: Hybrid transformer.

Claims (1)

[Claims] 1 In a signal demodulation method that uses a first modulation/demodulation means and a second modulation/demodulation means that have reception parameters that vary depending on the transmission characteristics of the transmission path, the signal is sent from the communication partner according to a predetermined transmission procedure. Receive a training signal, train the first modulation/demodulation means based on the training signal, hold reception parameters during the training, and return the results of the training to the communication partner by the second modulation/demodulation means. A signal demodulation system characterized in that, when the first modulation/demodulation means is used again after the above-described first modulation/demodulation means is used, the received reception parameters held are used.