JP2740365B2 - Modem - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem for a facsimile communication apparatus, and more particularly to a modem for switching a transmission rate according to a line condition.

[0002]

2. Description of the Related Art In recent years, with the spread of facsimile machines,
Although its use is spreading not only to corporations but also to ordinary households, the amount of information to be transmitted is steadily increasing. Under such circumstances, the facsimile machine is required to have higher speed than before. As a measure for responding to this demand, it is pointed out that the so-called data compression technique is dramatically improved, and improvements are being made every day.

On the other hand, as another measure, there is a method of increasing the data transmission rate itself. In this case, a so-called noise margin is reduced by the increase in the data transmission rate. It will occur frequently. For this reason, in a conventional facsimile apparatus, the transmission speed is changed according to the degree of the line quality.

FIG. 3 shows a transmission procedure in a conventional G3 (group 3) facsimile apparatus. Here, CCITT (International Telegraph and Telephone Consultative Committee) recommendation V. 21 and Recommendation V.21. It is assumed that the transmission is performed according to the procedure of FIG.

First, an original is set on the facsimile apparatus on the transmitting side (step S101), and the telephone number of the partner station (receiving side) is dialed (step S102). Recommendation V. A DIS (Digital Identification) signal specified as a signal for notifying the standard function of the receiving side by 21 is transmitted (step S104). Upon receiving this, the transmitting side requests a function setting to the receiving side by a DCS (digital command) signal (step S105).

[0006] After transmitting the DCS signal, the transmitting side transmits the CCITT recommendation V.10. A training signal having a speed of 9600 bps (bits / second) is transmitted (step S106), and after establishing synchronization with the receiving side, a TCF (training check) signal is transmitted (step S107). This TC
The F signal is a signal in which “0” continues for a predetermined time.

On the receiving side, the presence or absence of a bit error in the received TCF signal is checked. If the line quality of the transmission path is poor and a bit error has occurred (step S10
8), the receiving side is CCITT Recommendation V. 21 is transmitted (step S109).
Notifies that a bit error has occurred.

[0008] The transmitting side receiving the FTT signal again transmits the CCITT recommendation V.1. A training signal at a speed of 9600 bps is transmitted (step S110), and after establishing synchronization with the receiving side, a TCF signal is transmitted (step S111). On the receiving side, the presence or absence of a bit error in the received TCF signal is checked, and if a bit error is detected (step S112), the CCITT recommendation V.100 is again performed. 21 (step S11).
3) Notify the occurrence of a bit error.

As described above, when a bit error occurs twice consecutively, the transmitting side determines that transmission at this transmission rate is no longer possible, and switches the transmission rate to 7200 bps. And CCITT Recommendation V. 7200b by 29
A training signal of ps is transmitted (step S11).
4) As in the case of 9600 bps, TC
An F signal is transmitted (step S115).

On the receiving side, the same operation as in the case of 9600 bps is performed. That is, a bit error of the TCF signal is checked, and when an error is detected (step S11).
6), CCITT Recommendation V. Then, the FTT signal is transmitted (step S117).

In this case, if a bit error occurs twice in succession, the transmitting side determines that transmission at this transmission rate is no longer possible, and further switches the transmission rate to 4800 bps.

[0012] Similarly, when the line quality is severely degraded and a bit error occurs, the speed is switched stepwise up to 2400 bps.

[0013]

As described above, in the conventional modulation / demodulation device, the transmission speed is switched stepwise from high speed to low speed, and the transmission speed at the stage at which no bit error occurs is adopted. . For this reason, when the line quality is severely degraded, for example, from 9600 bps to 2400 bp
A complicated sequence must be repeated for four steps up to s, which has the disadvantage of taking an enormous amount of time.

An object of the present invention is to provide a modem capable of rapidly setting a transmission rate suitable for high-speed and stable data transmission.

[0015]

According to the first aspect of the present invention, (a) a signal modulated by a single modulation method corresponding to the highest transmission rate transmitted first of the training signal is modulated. Points and line products that should be received by the system
Error power indicating the distance between coordinate points received due to quality distortion, etc.
That is, error power measuring means for measuring the root mean square error ,
(B) storage means for storing, for each transmission rate, error power corresponding to an allowable data bit error rate for a signal modulated by a single modulation scheme corresponding to the highest transmission rate; Comparing means for comparing the measurement result of the error power measuring means with the allowable error power stored in the storage means;
Determining means for determining the optimum transmission rate in accordance with the comparison result of the comparing means; (e) setting means for setting the data transmission rate to the optimum transmission rate determined by the determining means;
A modulating / demodulating device is provided with a notifying unit for notifying a game of a judgment result of the judging unit.

That is, according to the first aspect of the present invention, the tray
Corresponding to the highest transmission rate transmitted at the beginning of the
Modulation method for signals modulated by a single modulation method
The error power in the equation is measured by the error power measuring means, and this measurement
Based on the result, the allowable error power for each transmission rate is
And determine the optimal transmission rate. And
Set the data transmission rate to its optimal transmission rate and
The optimum transmission speed is also notified to the game. This allows
In the game, the training signal is transmitted in order from the highest transmission speed.
Optimal transmission speed immediately without having to reduce the transmission speed
Then, the transmission of data can be started.

[0017]

[0018]

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows a modem according to an embodiment of the present invention. This apparatus is provided with a network control unit (hereinafter, referred to as NCU) 11 for controlling switching between connection to a line 12 between a telephone set 13 and a modem unit 14. NCU 11 and modem 1
4 is connected by an output line 15 and an input line 16. Of these, the output line 15 is branched into two and connected to the respective output sides of the image signal modulator 17 and the control signal modulator 18 of the modem 14.

The input side of the image signal modulator 17 is connected to the encoder 1
9 is connected to the reading unit 21. The image signal modulating section 17 converts the coded signal read from the document by the reading section 21 and coded by the coding section 19 into a CCITT recommendation V.10.
29 or V.I. The modulation is performed by 27ter. The modulation speed can be appropriately switched under the control of the control unit 28.

The control signal modulating section 18 includes a control section 28
The transmission control signal of G3 is controlled by CCITT Recommendation V.
The modulation is performed by the control unit 21 and the optimum transmission speed information instructed by the control unit 28 is modulated.

On the other hand, the input line 16 is branched into two and connected to the respective input sides of the image signal demodulation unit 23 and the control signal demodulation unit 24. The output side of the image signal demodulation unit 23 is connected to the recording unit 26 via the decoding unit 25, and is also connected to the reception signal quality measurement unit 27.

The image signal demodulation section 23 converts a received signal from the NCU 11 into a CCITT recommendation V.11. 29 or V.I. 27ter
To demodulate. The demodulation speed can be appropriately switched under the control of the control unit 28.

The control signal demodulation unit 24 demodulates the G3 transmission control signal under the control of the control unit 28, and transmits the transmission speed information to the CCITT Recommendation V.3. 21 demodulates.

The received signal quality measuring section 27 measures the received signal error power indicating the quality of the received signal based on the judgment error signal input from the image signal demodulating section 23.

A ROM (Read Only Memory) 29 is connected to the control unit 28. This ROM 29
Stores a table as shown below, which associates a threshold level of the received signal quality that can be permitted for each transmission rate.

9600 bps: A0h 7200 bps: B0h 4800 bps: C0h 2400 bps: D0h

Here, as the transmission rate, CCITT Recommendation V. 29 9600bps and 7200bps, and C
CITT Recommendation V. 4800bps and 240 of 27ter
0 bp can be selected, and the bit error rate is 1
If it satisfies × 10 ⁻⁵ , image information can be transmitted sufficiently stably. Therefore, the values “A0h” to “D0h” shown in hexadecimal in the right column of the table have a bit error rate of 1 × 10 ^−5.
Shows the received signal error power for each transmission rate corresponding to.

The operation of the modulation / demodulation device having the above configuration will be described with reference to FIG. Here, description of the same signals and the like as in the conventional example (FIG. 3) will be appropriately omitted. Also, the sender,
It is assumed that both the modulation and demodulation devices on the receiving side have the above-described configuration.

First, when a document is set on the facsimile machine on the transmitting side (step S101), transmission information is read from the document under the control of the control unit 28. Next, the telephone 13 dials (step S102), and when there is a response (step S103), a line is connected to the other party. Then, the control unit 28
11 is switched to the modem unit 14 by controlling the line.

Next, when the DIS signal is received from the receiving side (step S104), this is transmitted to the control signal demodulation unit 24.
Is demodulated. The control unit 28 detects the extension bit added to the DIS signal and determines whether or not the other party has a function equivalent to that of the own station. As a result, when an extension bit is detected, the extension bit of a predetermined pattern is added to the DCS signal, and the DCS signal is modulated by the control signal modulator 18 and transmitted (step S105). As a result, a request for setting the function is made to the receiving side.

Next, the image signal modulating unit 17 receives the CCITT recommendation V. 29 training signals of 9600 bps are transmitted (step S106).

After the training sequence, on the receiving side, the received signal quality measuring section 27 measures the error power of the received signal (step S107), and the control section 28
Will be notified. The control unit 28 compares the measured error power value with the error power data stored in the table of the ROM 29. If this value is, for example, “D8h” , since this value satisfies the following equation (1), the control unit 28 sets the optimum transmission rate to the CCITT Recommendation V.3. 27te
It is determined to be 2400 bps of r.

C0h>D8h> D0h (1)

Then, the control section 28 adds the information indicating the optimum transmission rate to the DIS signal as extension bits, modulates the control signal with the control signal modulating section 18, and sends it to the transmitting side (step S108).

[0037] Upon receiving this, the control unit 28 on the transmitting side sets the DI
It decodes the extension bits of the S signal and sets the transmission speed to CCITT Recommendation V. It recognizes that 27 should be 2400 bps.
Then, information indicating that fact is added as an extension bit to the DCS signal, modulated by the control signal modulator 18 and transmitted to the receiving side (step S109).

After transmitting the DCS signal, the transmitting side transmits the CCITT recommendation A training signal is transmitted at 2400 bps of 27 ter (step S110). After completion of the training sequence, the control unit 28 encodes the image signal read by the reading unit 21 by the encoding unit 19, modulates the image signal by the image signal modulation unit 17, and transmits the modulated signal (step S111).

When the transmission of a series of image information is completed, the transmitting side transmits an RTC signal (step S112), and further transmits an EOP (procedure end) signal indicating the end of the procedure (step S113). On the other hand, when an MCF (message confirmation) signal indicating that the message has been received is transmitted from the receiving side (step S114), the control unit 2 on the transmitting side receives the message.
8 judges that all transmission procedures have been completed, and sends out a DCN (line disconnection) signal (step S115). As a result, the line is disconnected (step S116).

[0040]

As described above, the invention according to claim 1 is described above.
According to the best transmitted at the beginning of the training signal
For signals modulated by a single modulation method corresponding to the transmission rate
The acceptable data bit error rate for the modulation scheme
Is stored for each transmission rate,
The best transmission during the early training stage of communication
A signal modulated by a single modulation method corresponding to the transmission speed is transmitted.
Error power in this modulation method
By measuring the data and comparing it with the stored contents.
We decided to set the lowest transmission speed. Because of this, transmission
There is no need to switch speeds from high to low
The training signal was sent at the highest transmission rate
Can immediately set the optimal transmission speed
There are advantages. Thus, for example, even when the fluctuation of the quality of the line is severe, rapidly can set the transmission speed of the optimum, child reduce the time to start the actual communication
Can be.

[Brief description of the drawings]

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

FIG. 2 is a sequence diagram showing an operation between facsimile apparatuses using the modem.

FIG. 3 is a sequence diagram showing an operation between facsimile apparatuses using a conventional modem.

[Explanation of symbols]

 11 NCU 13 Telephone 14 Modulation / demodulation unit 27 Received signal quality measurement unit 28 Control unit 29 ROM

Claims (1)

(57) [Claims] 1. A signal modulated by a single modulation method corresponding to the highest transmission rate of a training signal transmitted first, and a coordinate point and a time to be originally received by the modulation method.
Error power measuring means for measuring an error power indicating a distance between coordinate points received due to line quality distortion, etc., and data allowable for a signal modulated by a single modulation method corresponding to the highest transmission rate. Storage means for storing error power corresponding to a bit error rate for each transmission rate; comparison means for comparing the measurement result of the error power measurement means with the allowable error power stored in the storage means; Determining means for determining an optimal transmission rate in accordance with the comparison result, setting means for setting a data transmission rate to the optimum transmission rate determined by the determining means, and notifying means for notifying a game of the determination result of the determining means. And a modem.