JPH0422390B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high speed modem automatic equalizer control system for facsimile equipment. In particular, it relates to a control system that is not disturbed even by lines with large distortion or instantaneous noise.

〔overview〕

The present invention provides a control system that receives signals in accordance with a high-speed facsimile communication procedure and performs adaptive automatic equalization, in which a training check signal transmitted during the communication procedure is stored and a message signal is transmitted. When the equalization state becomes defective during reception of the signal, automatic equalization is interrupted and the equalizer is controlled using the stored equalization information. Even if a temporary control failure occurs, reception can continue.

[Conventional technology]

High-speed modems used in facsimile machines are
The configuration is such that the tap information of the automatic equalizer inside the modem is sequentially set according to the training sequence specified in V.29, V.27, and other regulations of the CCITT. Upon reception of this training signal, the automatic equalizer operates to automatically perform optimal equalization for the line in use. Conventional equipment uses training check signals (TCF) for facsimile communication procedures.
Automatic modem equalization was performed independently for reception and message signal (MSG) reception.

[Problem that the invention seeks to solve]

The conventional high-speed modem automatic equalizer described above determines the tap information of the automatic equalizer based on the training signal received through the communication line. In a line where unsteady noise (for example, impulse nozzle or instantaneous interruption) occurs, the automatic equalizer may not be able to operate normally. Therefore, in such a line, automatic equalization becomes unstable, and even if it is determined that communication is possible upon reception of a training check signal (TSF), communication may become impossible upon reception of a message signal (MSG).

The present invention solves the above problems,
It is an object of the present invention to provide an automatic equalizer control system which makes it possible to reliably receive a message signal on a line determined to be receivable based on a training check signal.

[Means for solving problems]

The control method of the high-speed modem automatic equalizer of the present invention is as follows:
Using a high-speed modem that can read and write automatic equalizer tap information and check the modem's equalization status, store tap information in memory when receiving a training check signal (TCF) for facsimile communication procedures. Then, when the training check signal (TCF) is received when the message signal (MSG) is received, the tap information stored in the memory is forcibly written to the automatic equalizer to correct abnormal operation of the automatic equalizer. The invention is characterized in that it has a control means for controlling.

[Effect]

If an equalization failure is detected while adaptive automatic equalization is being performed on the received signal, the adaptive automatic equalization is temporarily interrupted and, in principle, the latest training check signal that has been memorized is restored. Forcibly set the equivalent information at the time of reception to the equalizer. In many cases, the line condition quickly returns to a steady state, so the equalization information at the time of receiving the training check signal allows the subsequent message signal to be received normally.

〔Example〕

Next, an apparatus according to an embodiment of the present invention will be explained with reference to the accompanying drawings.

FIG. 1 is a block configuration circuit diagram of a high-speed modem receiving section of an apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a facsimile communication procedure according to an embodiment of the present invention.
The high-speed modem receiving section shown in FIG. 1 includes an analog signal processing section 1 (ASP) and a digital signal processing section 2.
(DSP) and a lock control circuit 3 (CLOCK) coupled to both.

The signal received from the line enters the analog signal processing unit 1 (ASP) from the signal input terminal (PXS), and is passed through the reception equalizer 1a and reception band limit filter 1b.
(REQL and BPF) automatic amplitude control circuit 1c
(AGC), analog/digital conversion circuit 1
d (A/D), thereby converting it into a digital signal, and inputting it to the digital signal processing unit 2 (DSP). In addition, the receiving band limiting filter 1b
The output signal of the (BPF) is input to the carrier detection circuit 1e, and the output thereof is used to transmit control information to the tandem connection circuit between the reception sequencer 2f (RSEQ) and the descrambler circuit 2g (DSCR) of the digital signal processing section 2. connected to.

In the digital signal processing unit 2 (DSP), the output of the analog/digital conversion circuit 1d is inputted from a demodulation circuit 2a (DMOD), passes through a roll-off filter 2b (ROF), and is passed through an automatic equalizer circuit 2c.
(AEQL), reception phase tracking circuit 2d
(TRC) in tandem. These two circuits 2c and 2d are feedback-controlled by a judgment circuit 2e (CAL), and then a descrambler circuit 2g (DSCR) and an interface circuit 2h.
Data output terminal (R×D) through (I/F)
The received data can be obtained. Here, the automatic equalizer circuit 2c (AEQL) and the judgment circuit 2e (CAL) are connected to the control processor 4 external to the high-speed modem receiving section (Fig. 1).
It is possible to read and write tap information and monitor the equalization status (error degree). The following control is performed using such a high-speed modem receiving section.

FIG. 2 is a diagram showing a facsimile communication procedure according to an embodiment of the present invention. In Figure 2, high-speed data signals include a training check signal (TCF) and a message signal (MSG), and a normal training check signal (TCF) consists of a high-speed training signal (Train) and a high-speed data signal (Data). A data check is only performed between points where the data signal (Data) is stable, but after the point, while the signal is still being generated, the tap information of the automatic equalizer circuit 2c of the modem is read out. Store it in memory (not shown). Next, when receiving the message signal (MSG) in Figure 2, after receiving the high-speed training signal (Train), check the modem's equalization state (error degree) at a point close to the boundary with the high-speed data signal (Data). In the case of , the reception continues as it is, and in the case of a defect, the tap information read out when receiving the training check signal (TCF) is forcibly written to the automatic equalizer circuit 2c to correct the equalizer.

Generally, line characteristics during one communication are constant, and training check signal (TCF) reception and message signal (MSG) reception can be equalized using the same tap information. Therefore, by performing the above control, the training check signal (TCF)
If it is determined that communication is possible, message signals (MSG) can be reliably received even if noise or line distortion suddenly occurs.

〔Effect of the invention〕

As explained above, according to the present invention, even if the equalization state temporarily becomes defective while receiving a message signal, the equalization defect does not continue for a long time, and the message signal is There is no chance that you will be unable to receive data. When the present invention is applied to a line with large distortion or a line with a lot of instantaneous noise, the rate of poor reception can be extremely reduced.

[Brief explanation of drawings]

FIG. 1 is a block configuration circuit diagram of a high-speed modem receiving section according to an embodiment of the present invention. FIG. 2 is a diagram showing a facsimile communication procedure according to an embodiment of the present invention. 1...Analog signal processing unit (ASP), 2...Digital signal processing unit (DSP), 1a...Reception equalizer (fixed) (REQL), 1b...Reception band limit filter (BPF), 1c... automatic amplitude control circuit (AGC),
1d...Analog/digital conversion circuit (A/D),
1e...Carrier detection circuit (CD), 2a...Demodulation circuit (DMOD), 2b...Roll-off filter (ROF), 2c...Automatic equalizer circuit (AEQL), 2
d...Reception phase tracking circuit (TRC), 2e
...Judgment circuit (CAL), 2f...Reception sequencer circuit (RSEQ), 2g...Descrambler circuit (DSCR), 2h...Interface circuit (I/
F), 3...Clock control circuit (CLOCK), 4...
...control processor, RxD...received data output terminal, RxS...received signal input terminal, CED...identification signal of called station, DIS...initial identification signal, DCS...incoming command signal, TCF... ...Training check signal, CFR...Receipt confirmation signal,
MSG...message signal, EOM...end of message signal, MCF...message confirmation signal, DCN...disconnection signal, Train...high-speed training signal, Data...high-speed data signal.

Claims (1)

[Claims] 1. Receiving a training check signal and a message signal according to a high-speed facsimile communication procedure, adaptively automatically equalizing the received signal using a high-speed modem, and equalizing the received signal. In the automatic equalizer control method that monitors the status, the equalization information obtained when the training check signal is received is stored, and when the equalization status becomes defective while receiving the message signal, the stored equalization information is A control method for a high-speed modem automatic equalizer, characterized in that equalization information is forcibly set in the automatic equalizer, adaptive automatic equalization is temporarily stopped, and reception is continued.