JPH04292070A - Modem - Google Patents

Abstract

PURPOSE:To quickly set transfer speed capable of keeping high-speed and stable transfer quality at the time of starting data transfer. CONSTITUTION:A reception signal quality measuring part 27 measures the error power of a training signal transmitted from the transmission side and demodulated by a picture signal demodulation part 23 and reports it to a control part 28. A ROM 29 stores the threshold value of allowable reception signal error power for each transfer speed. A control part 28 decides the optimum transfer speed by comparing error power reported from the reception signal quality measuring part 27 and the threshold value in the ROM, adds this to a DIS signal to be transmitted to the transmission side after modulated by a control signal modulation part 18. On the transmission, the optimum transfer speed information added to the received DIS signal is recognized, the information is added to the DIS signal and transmitted to the reception after modulated by the control signal modulation part 18. Thus, the data is transferred at the optimum transfer speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation/demodulation device for facsimile communication equipment, and more particularly to a modulation/demodulation device that switches transmission speeds in accordance with line conditions.

0002

[Background Art] In recent years, with the spread of facsimile machines,
Its use is expanding not only in companies but also in ordinary households, and the amount of information that must be transmitted continues to increase. Under these circumstances, facsimile machines are required to be faster than conventional facsimile machines. As a measure to meet this demand, it has been proposed to dramatically improve so-called data compression technology, and improvements are being made every day.

On the other hand, another method is to increase the data transmission speed itself, but in this case, the so-called noise margin decreases due to the increase in speed, so if the line quality is degraded, data errors may occur. This will occur frequently. For this reason, in conventional facsimile machines, the transmission speed is changed depending on the level of line quality.

FIG. 3 shows a transmission procedure in a conventional G3 (group 3) facsimile machine. Here, CCITT (International Telegraph and Telephone Consultative Committee) Recommendation V
．． 21 and the same Recommendation V. It is assumed that the transmission is performed according to the procedure according to No. 29.

First, a document is placed on the facsimile machine on the sending side (step S101), and the telephone number of the other party (receiving side) is dialed (step S102).The receiving side responds to this (step S103), and the CCITT Recommendation V. 21, a DIS (digital identification) signal defined as a signal for notifying the standard function of the receiving side is transmitted (step S104). Upon receiving this, the transmitting side requests the receiving side to set a function using a DCS (digital command) signal (step S105).

[0006] After transmitting the DCS signal, the transmitting side complies with CCITT Recommendation V. After transmitting a training signal at a speed of 9,600 bps (bits per second) of 29 (step S106) and 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 period of time.

[0007] On the receiving side, the presence or absence of bit errors in the received TCF signal is checked. If the line quality of the transmission path is poor and a bit error occurs (step S108)
, the receiving side complies with CCITT Recommendation V. A No. 21 FTT (training failure) signal is sent out (step S109) to notify the occurrence of a bit error.

[0008] The transmitting side that received this FTT signal once again complies with CCITT Recommendation V. After transmitting a training signal at a speed of 9600 bps of 29 (step S110) and 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. 21 FTT signals are sent (step S113).
, notifies the occurrence of a bit error.

[0009] In this way, when a bit error occurs twice in a row, the transmitting side determines that it is no longer possible to transmit at this transmission speed, and switches the speed to 7200 bps. And CCITT Recommendation V. 7200bp by 29
s training signals are transmitted (step S114).
), as in the case of 9600 bps, TCF after synchronization is established.
A signal is sent out (step S115).

[0010] On the receiving side, the same operation as in the case of 9600 bps is performed. That is, check for bit errors in the TCF signal, and when an error is detected (step S116)
, CCITT Recommendation V. 21 is sent out (step S117).

[0011] In this case as well, if bit errors occur twice in a row, the transmitting side determines that it is no longer possible to transmit at this transmission rate, and further switches the rate to 4800 bps.

[0012] Similarly, if the line quality deteriorates significantly and bit errors occur, the speed will be changed stepwise up to 2400 bps.

[0013]

[Problems to be Solved by the Invention] In this way, conventional modem devices switch the transmission speed from high to low in stages, and adopt the transmission speed at which bit errors no longer occur. . For this reason, if the line quality is severely degraded, for example from 9600bps to 2400bps
The disadvantage is that a complicated sequence must be repeated over four stages up to s, which takes an enormous amount of time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a modulation/demodulation device that can quickly set a transmission rate suitable for high-speed and stable data transmission.

[0015]

[Means for Solving the Problem] The invention according to claim 1 provides: (i) a received signal quality measuring means for measuring the quality of a received signal; and (ii) a received signal quality corresponding to an acceptable data bit error rate. The modulation/demodulation device is provided with a storage means for storing the data for each transmission rate, and (iii) a determining means for determining the optimum transmission rate by referring to the storage means based on the measurement result of the received signal quality measurement means.

[0016] In the invention described in claim 1, a permissible value of received signal quality is set in advance for each transmission speed,
The optimum transmission rate is determined according to the measured received signal quality value.

[0017] In the invention as claimed in claim 2, (i) error power measuring means for measuring error power indicating the quality of the received signal; and (ii) error power corresponding to an allowable data bit error rate for each transmission. A storage means for storing each speed, and (
iii) comparison means for comparing the measurement result of the error power measuring means and the allowable error power stored in the storage means;
) determining means for determining the optimum transmission rate according to the comparison result of the comparing means; (v) setting means for setting the data transmission rate to the optimum transmission rate determined by the determining means;
vi) The modulation/demodulation device is provided with a notification means for notifying the game player of the determination result of the determination means.

[0018] According to the second aspect of the invention, permissible values of received signal error power are set in advance for each transmission speed, and the optimum transmission is determined by comparing the measured error power with these permissible values. The speed is determined and set, and the other party's speed is notified of this.

[0019]

EXAMPLES The present invention will be explained in detail with reference to Examples below.

FIG. 1 shows a modulation/demodulation device according to an embodiment of the present invention. This device is equipped with a network control unit (hereinafter referred to as NCU) 11, which controls switching of the connection to the line 12 between a telephone 13 and a modulation/demodulation section 14. NCU 11 and modem unit 1
4 are connected by an output line 15 and an input line 16. Of these, the output line 15 is branched into two, an image signal modulation section 17 of the modulation/demodulation section 14 and a control signal modulation section 1 of the modulation/demodulation section 14.
It is connected to each output side of 8.

The input side of the image signal modulation section 17 is connected to the encoding section 1.
It is connected to the reading section 21 via 9. The image signal modulation section 17 converts the encoded signal read from the original by the reading section 21 and encoded by the encoding section 19 into CCITT Recommendation V.
29 or V. It is designed to be modulated by .27ter. The speed of this modulation can be changed as appropriate under the control of the control section 28.

[0022] The control signal modulation section 18 also includes a control section 28.
The G3 transmission control signal is controlled by CCITT Recommendation V.
21 and also modulates optimal transmission rate information instructed by a control unit 28.

On the other hand, the input line 16 is branched into two, and is connected to each input side of an image signal demodulating section 23 and a control signal demodulating section 24. The output side of the image signal demodulating section 23 is connected to the recording section 26 via the decoding section 25 and also connected to the received signal quality measuring section 27 .

The image signal demodulation unit 23 converts the received signal from the NCU 11 into CCITT Recommendation V. 29 or V. 27ter
It is designed to be demodulated by This demodulation speed can be changed as appropriate under the control of the control section 28.

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

The received signal quality measuring section 27 measures the received signal error power, which indicates the quality of the received signal, based on the determination error signal inputted from the image signal demodulating section 23.

A ROM (read only memory) 29 is also connected to the control section 28 . This ROM29
A table as shown below is stored in which the threshold level of acceptable received signal quality is associated with each transmission speed.

9600bps: A0h7200
bps: B0h 4800bps: C0h 2400bps: D0h

Here, the transmission speed is based on CCITT Recommendation V. 29 9600bps and 7200bps, and C
CITT Recommendation V. 27ter's 4800bps and 240
0bp can be selected, and the bit error rate is 1
It is assumed that image information can be transmitted in a sufficiently stable manner if ×10-5 is satisfied. Therefore, the values “A0h” to “D0h” shown in hexadecimal numbers in the right column of the table have a bit error rate of 1×10
The received signal error power for each transmission rate corresponding to −5 is shown.

The operation of the modulation/demodulation apparatus having the above configuration will be explained with reference to FIG. Here, descriptions of the same signals as in the conventional example (FIG. 3) will be omitted as appropriate. Also, on the sending side,
It is assumed that both the modulation and demodulation devices on the receiving side have the configuration described above.

First, when a document is set on the sending facsimile machine (step S101), transmission information is read from the document under the control of the control section 28. Next, a call is made from the telephone 13 (step S102), and when there is a response (step S103), a line is connected to the other party. The control unit 28 is an NCU
11 to switch the line to the modulation/demodulation section 14.

Next, when the DIS signal from the receiving side is received (step S104), this signal is sent to the control signal demodulator 24.
It is demodulated by The control unit 28 detects the extension bit added to this DIS signal and determines whether the other party has the same functions as the local station. As a result, when an extension bit is detected, the extension bit of a predetermined pattern is added to the DCS signal, modulated by the control signal modulation section 18, and sent out (
Step S105). This requests the receiving side to set the function.

Next, the image signal modulation section 17 operates according to the CCITT Recommendation V. 29 training signals of 9600 bps are transmitted (step S106).

After this training sequence is completed, on the receiving side, the received signal quality measurement 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 error power data stored in a table in the ROM 29 . If this value is, for example, "A8h", this value satisfies the following equation (1), so the control unit 28 determines the optimum transmission speed according to CCITT Recommendation V. 27te
It is determined that r is 2400 bps.

[0035] B0h>A8h>A0h...(1)

Then, the control section 28 adds information indicating this optimum transmission speed to the DIS signal as an extension bit, modulates it with the control signal modulation section 18, and sends it to the transmitting side (step S108).

[0037] Upon receiving this, the control unit 28 on the transmitting side transmits the DI
The extension bits of the S signal are decoded and the transmission speed is determined according to CCITT Recommendation V. Recognize that it should be 2400 bps of 27. Then, information indicating this is added to the DCS signal as an extension bit, modulated by the control signal modulation section 18, and then sent to the receiving side (step S109).

After sending the DCS signal, the transmitting side complies with CCITT Recommendation V. A training signal of 27ter at 2400 bps is transmitted (step S110). After the training sequence ends, the control unit 28 encodes the image signal read by the reading unit 21 in the encoding unit 19, modulates it in the image signal modulation unit 17, and sends it out (step S111).

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

[0040]

As explained above, according to the present invention, a permissible value of received signal quality is set in advance for each transmission speed, and the optimum transmission speed is determined according to the measured value of received signal quality. Since this is determined, there is no need to step-by-step switch the transmission speed from high to low as in the conventional case. Therefore, even if, for example, the line quality is severely degraded, the optimum transmission speed can be quickly set.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a modulation/demodulation device in an embodiment of the present invention.

FIG. 2 is a sequence diagram showing operations between facsimile machines using this modulation/demodulation device.

FIG. 3 is a sequence diagram showing operations between facsimile machines using conventional modulation and demodulation devices.

[Explanation of symbols]

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

Claims (2)

[Claims] 1. Received signal quality measuring means for measuring the quality of a received signal, storage means for storing received signal quality corresponding to an allowable data bit error rate for each transmission speed, and said received signal quality measuring means. 2. A modulation/demodulation device comprising: determination means for determining an optimum transmission rate by referring to the storage means based on the measurement results. 2. Error power measuring means for measuring error power indicating the quality of a received signal; storage means for storing error power corresponding to an allowable data bit error rate for each transmission rate; a comparison means for comparing the measurement result of the measurement means and the allowable error power stored in the storage means; a determination means for determining the optimum transmission rate according to the comparison result of the comparison means; and a determination means for determining the data transmission rate. 1. A modulation/demodulation device comprising: a setting means for setting the optimum transmission rate determined by the determination means; and a notification means for notifying a game player of the determination result of the determination means.