JPH03285455A - Data transmitter - Google Patents

Abstract

PURPOSE:To enable high-quality data transmission by calculating error between a received signal vector and an original vector when training a MODEM, deciding transmission quality and shifting-down data transmission speed when the transmission does not satisfy the constant quality. CONSTITUTION:After receiving a DCS signal, the training operation of a high- speed MODEM 41 is executed. An error detection circuit 412h outputs an error vector Er showing deviation between the signal vector of the received signal and the original signal vector. An equalizer control circuit 412i controls an equalizer 412d so that the error vector Er can be made minimum. A multiplier circuit 412l outputs the degree of margin to noise on a transmission line at that time, namely, outputs the evaluation value of the transmission quality. When evaluation value data Ed is less than a certain fixed value, the data transmission speed of the high-speed MODEM 41 is shifted down and turned to a signal reception state at the data speed lower for one stage.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a data transmission device.

[Prior art] G3 facsimile machines commonly used are C
Image information is transmitted by a modem that complies with CITT Recommendation V.27ter or V.29.

This modem is equipped with an equalizer that automatically corrects distortion in the transmission path, and also has the function of transmitting image information at various data transmission speeds.

In the transmission control procedure of the facsimile apparatus described above, modem training is executed to determine the data transmission speed at the start of communication. This modem training involves transmitting a modem training signal and certain data signals. On the receiving side, the equalizer is adjusted according to the line characteristics, while the error rate of the received data is determined, and if the error rate exceeds a certain value, it instructs the transmitting side to transmit the data. The speed is shifted down sequentially.

Then, when the error rate of received data becomes less than a certain value, transmission of image information is started at the data transmission speed.

Incidentally, the transmitting side transmits the code of transmission data, which is image information, as various vector signals having different phases and amplitudes. Transmission distortion occurs in this vector signal during transmission.

On the receiving side, the received vector signal is corrected to some extent by the equalizer, and then reproduced by the encoder into a code corresponding to the vector signal.

[Problem to be solved by the invention] However, since the transmission distortion correction described above is not perfect,
When a constant code is reproduced by the encoder, an error occurs between the original vector signal corresponding to the constant code and the received vector signal.

If this error is large, if the transmitted vector signal receives noise on the transmission path, it will be regenerated into another code on the receiving side, resulting in a data error.

In other words, the smaller the error, the greater the margin against noise in the transmission path.

On the other hand, in the case of facsimile communication, the noise on the telephone line, which is the transmission path, constantly fluctuates. Therefore, for example, suppose that the modem training is executed at a time when there is little noise, and the transmission of image information is started when the error in the received data becomes zero.

However, after this, if the line condition deteriorates and noise increases, data errors will occur if the margin against the noise is small.

As mentioned above, conventionally, in modem training,
The propriety of communication at one data transmission rate was determined based on the error rate of temporarily transmitted data, and the margin against noise was not determined. For this reason, if the line condition subsequently deteriorates, data errors occur and high-quality data transmission is not possible.

An object of the present invention is to provide a data transmission device that can improve the above problems and transmit data with high quality.

[Means for Solving the Problems] To this end, the present invention provides the following features when receiving a training signal:
The error between the received signal vector and the original vector when there is no signal distortion on the transmission path is determined, and based on that error, the transmission quality, which is the margin against noise on the transmission path at the data transmission speed at that time, is determined. However, the data transmission rate is downshifted when the transmission quality is less than a certain quality, and the data signal is received when the transmission quality is equal to or higher than the certain quality.

[Operation] This allows data transmission to be performed while always ensuring a certain degree of margin against noise on the transmission path. Therefore, even if the line condition deteriorates to some extent after modem training, data errors are prevented from occurring, and high-quality data transmission is possible.

Pretext Side] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of a facsimile apparatus according to an embodiment of the present invention. In the figure, a scanner 1 reads an original image and extracts image information, and a plotter 2 records the image on recording paper. The encoding/decoding unit 3 is.

While image information to be transmitted is compressed by encoding, received image information is decoded and reproduced into the original image information.

The modem 4 transmits image information and procedure signals for transmission control. The high speed modem 41.

Transmits and receives image information using various modulation methods in accordance with CCI TT Recommendations V, 27ter and V, 29, and uses low-speed modem 4.
2 transmits and receives the above procedure signal in accordance with Recommendation V.21. The network control device 5 is connected to a telephone line and controls the line when making and receiving calls.

The operation display section 6 includes a display and operation keys, and displays the operating status of the device, and is used by the operator to perform various operations.

The CPU 7 controls each part mentioned above, and the ROM 8
It stores the control program and various fixed data. Further, the RAM 9 temporarily stores various data, and the system bus 10 is a signal line through which the above-mentioned units exchange various data and control signals between each other.

FIG. 2 shows a block configuration of the receiving side circuit of the high-speed modem 41. In the figure, an analog processing section 41
1 processes the received analog data signal and converts it into PCM
When receiving the modem training signal, the digital processing unit 412 performs the above-mentioned two types of adjustment, and outputs the ninth transmission quality evaluation value data.
When receiving data, the received data is reproduced and output.

In the analog processing unit 411, the received signal input from the network control device 5 is processed through a filter 41 that removes unnecessary signals.
1a, and its output is input to a variable gain amplifier 411b whose amplification degree can be adjusted.

The variable gain amplifier 411b output is an A/D (analog/digital) that converts the output signal into a PCM signal.
The signal is input to the conversion circuit 411c, and its output is input to the AGC control circuit 412a of the digital processing section 412.

The AGC control circuit 412a is a variable gain amplifier 411b.
is used to control the level of the output signal from the analog processing section 411 to a constant value, and its output is input to a demodulation circuit 412b that returns the PCM signal to a baseband signal. The output of the demodulation circuit 412b is inputted via a baseband filter 412c to a filter 412d that corrects distortion of the received signal according to the characteristics of the transmission path.

The output of the equilateral type 412d is input to an encoder 412e that converts the received signal into code data corresponding to the signal vector. Its output is input to a decoder 412f that forms a bit string of received data.

Its output is a descrambler 41 that restores the data scrambled on the transmitting side and reproduces the received data.
2g is input.

On the other hand, each output of the 1 equalizer 412d and the encoder 412e is
Error detection circuit 4 that calculates the error between the vector of the modulated received signal and the original vector when transmitted on the transmitting side
It is input in 12h. The error vector Er obtained by this error detection circuit 412h is
1 and is input to the absolute value conversion circuit 412j.

The equivalence base adjustment circuit 4121 adjusts the equivalence base type 412d so that the above-mentioned error is minimized. The absolute value conversion circuit 412j converts the error vector Er into an absolute value.

Each output from the absolute value conversion circuit 412j and the scale value output circuit 412 is input to an arithmetic circuit 4121. The multiplication circuit 4121 calculates the product of these two signal values, and the calculated value is input to the integration circuit 412m.

The scale value output circuit 412 is configured so that the output value of the multiplier 4121 indicates the above-mentioned margin against noise in the transmission path, that is, the evaluation value of the transmission quality.

It outputs each part according to the data transmission speed.

The integration circuit 412m consists of an adder circuit a1, a multiplication circuit S, a delay circuit C, and an integral constant circuit d, and integrates the input signal to smooth temporal fluctuations and outputs it as an evaluation value EO. is the evaluation value data generation circuit 4
12n.

This evaluation value data generation circuit 412n generates various bit pattern data according to the input evaluation value EO and outputs it as evaluation value data Ed.

The data selection circuit 4120 selects evaluation value data Ed from the evaluation value data generation circuit 412n during modem training.
When receiving image information, use descrambler 4.
To extract the image information data received from 12g,
This is for selecting the current location data.

With the above configuration, next, the image information receiving operation of the facsimile apparatus of this embodiment will be explained.

When this facsimile machine receives an incoming call, it transmits a CHD signal and a DI signal according to a known transmission control procedure, as shown in FIG.
S signal is sent.

In contrast, the transmitting side, which is the other party, transmits a DO5 signal, a modem training signal, and a TCP signal.

After receiving the DC5 signal, this facsimile machine executes a training operation of the high-speed modem 41.

FIG. 4 shows this operation. When the low-speed modem 42 finishes receiving the DC5 signal (processing 1001),
The data selection circuit 41 extracts the evaluation value data Ed.
2o (process 1002). Next, a scale value that is preset according to the data transmission speed is set in the scale value output circuit 412k (process 1003).

A modem training signal and a TCP signal are then received (processed 1004).

These received signals are converted into PCM signals by an analog processing section 411. Then, it is converted back into an analog signal by a demodulation circuit 412b in the digital processing section 412.

Unnecessary band signals are removed by the baseband filter 412c, and transmission distortion is corrected by the baseband filter 412d. next,
The analog signal is converted into a digital signal code by an encoder 412e, a received data bit string is formed by a decoder 412f, and is reproduced into the original data by a descrambler 412g.

On the other hand, the error detection circuit 412h detects an error vector E indicating the difference between the signal vector of the received signal and the original signal vector.
Output r. The number of books adjustment circuit 4121 adjusts the number of books 412d so that the error vector Er becomes the minimum (process 1004).

Also, at this time, the error vector Er is converted to an absolute value by the absolute value conversion circuit 412j, and is also converted to an absolute value by the arithmetic circuit 4121.
The scale value is multiplied by the above scale value, and the integration circuit 412m
smoothed by .

By the way, when the encoder 412e reproduces a code from the received signal, when the data transmission rate is, for example, 9600 bpS, the signal is modulated by 16-value orthogonal amplitude modulation, so one signal vector of the received signal is reproduced.

It must be identified as one of 16 vectors based on the difference in amplitude and phase. On the other hand, for example, 24
When the signal is 00 bps, it is a signal modulated by four-phase phase modulation, so it can be identified as one of four types of vectors.

- In this way, the higher the data transmission rate, the greater the number of identified vectors, and the closer the distance between each vector becomes. Therefore, if noise enters the transmission path without sufficient distortion correction by the encoder 412e, the higher the data transmission rate, the more likely errors will occur in the received data.

Therefore, in order to reproduce received data without errors,
The higher the data transmission rate, the smaller the error vector Er must be.

The scale value output circuit 412 outputs, as a scale value, a value that is larger as the data transmission speed is higher and smaller as the data transmission speed is lower, contrary to the distance between the vectors.

As a result, the 1 multiplier circuit 4121 outputs the degree of margin against noise on the transmission path at that time, that is, the evaluation value of the transmission quality, regardless of the data transmission speed.

This transmission quality evaluation value is smoothed over time by an integrating circuit 412m to become a transmission quality evaluation value EO.

As shown in FIG. 5(a), the evaluation value data generation circuit 412n inputs the evaluation value Eo of the transmission quality and generates 1-byte data D in eight types of patterns according to the level.

~D8 is repeatedly output as evaluation value data Ed.

As shown in the figure (b), this evaluation value data Ed outputs data Do with all 8 bits of VT when the transmission quality is the best.Then, as the transmission quality deteriorates, data Do is output in sequence. D1 to D8 are output.

These data D1 to D8 are set so that the number of bits that become rr 114 increases sequentially as the transmission quality deteriorates.

In this way, the output evaluation value data Ed is compared with a preset constant value (process 1005).
. If the evaluation value data Ed is less than a certain value (N in process 1005), an FTT signal is sent out (process 1006). Then, the data transmission rate of the high-speed modem 41 is shifted down to a signal receiving state at a -step lower data rate (process 1007).

As a result, the transmitting side shifts down the data transmission rate and, as shown in FIG. 3, transmits the DC5 signal, modem training signal, and TCP signal again.

The receiving side repeats the above operation in accordance with the set data transmission rate (proceeds to process 1003). As a result, the data transmission rate is shifted down from 9600 bps to 7200 bps, and modem training is performed again.

Then, if the evaluation value data Ed exceeds a certain value (
Y in process 1005), send out a CFR signal (process 10
08). Thereafter, the data selection circuit 4120 is switched to receive the received data (process 1009), and a predetermined image reception operation is executed.

As described above, in this embodiment, during modem training, the error in encoding the received signal is determined, and the transmission quality, which is the margin against noise on the transmission path, is determined based on the error. When the transmission quality is less than a certain quality, the data transmission speed is shifted down, and when the transmission quality exceeds the certain quality, image information is received.

As a result, image information can always be received with a certain degree of margin against noise on the transmission path, so even if the condition of one line deteriorates to some extent afterwards, data errors are prevented from occurring. Therefore, image information can be transmitted with high quality.

In addition, the modem 4 has a function of selecting and outputting transmission quality evaluation value data indicating transmission quality and received data, while the transmission quality is determined only by the transmission quality evaluation value data.
The state is the highest when it is 0'', and as the number of bits that are 1 increases, the condition becomes worse.

Conventionally, whether or not to shift down was determined based on the number of bits in which the all ``0'' data transmitted in the TCP signal changed to II 171, but in the above embodiment, the number of bits in II 1 II The more the transmission quality increases, the worse the transmission quality is. Therefore, the above-mentioned conventional shift down determination means can be used. This makes it possible to reduce the increase in hardware and software costs of the facsimile machine of this embodiment.

In the above embodiment, the modem of a facsimile machine was explained as an example, but modem training is performed at the start of communication, and if the results are poor, the data transmission speed is shifted down, and when certain conditions are met, the modem training is performed. For various data transmission devices that perform data transmission at data transmission speeds,
Naturally, the present invention can be similarly applied.

[Effects of the Invention] As described above, according to the present invention, when modem training is executed, the error between the received signal vector and the original vector is determined, and the data transmission rate at that time is determined based on the error. The transmission quality, which is the margin against noise on the transmission path, is determined.

If the transmission quality does not meet a certain level, the data transmission speed is shifted down, so data transmission can always be carried out while maintaining a certain margin against noise on the transmission path. 5 Even if the line condition worsens to some extent, data errors are prevented from occurring.
High quality data transmission becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a facsimile apparatus according to an embodiment of the present invention, FIG. 2 is a block configuration diagram of a receiving side circuit of a high-speed modem, and FIG. 3 is an explanatory diagram showing an example of a transmission control procedure. The figure is a flowchart of modem training operation,
FIG. 5(a) is an explanatory diagram showing the function of the evaluation value data generation circuit, and FIG. 5(b) is an explanatory diagram of the data pattern of transmission quality evaluation value data. DESCRIPTION OF SYMBOLS 1... Scanner, 2... Plotter, 3... Encoder/decoder, 4... Modem, 5... Network control device, 6...
...Operation display section. 7-CPU, 8.=-ROM, 9-RAM, 10-system path, 41... High-speed modem, 42... Low-speed modem, 411... Analog processing section, 411a... Filter, 411b...・Variable gain amplifier, 411c
...A/D conversion circuit, 412...digital processing section,
412a... AGC control circuit, 412b... demodulation circuit, 412c... baseband filter, 412d...
...Equivalent type, 412e...Encoder, 412f...
・Decoder, 412g...Discrambler, 412
h...error detection circuit, 412j...equal adjustment circuit,
412j... Absolute value conversion circuit, 412k... Scale value output circuit, 4121... Multiplication circuit, 412m...
Integration circuit, 412n...Evaluation value data generation circuit, 4
12o...Data selection circuit.

Claims (2)

[Claims] (1) A modem that receives data signals modulated at various data transmission speeds and regenerates the received data by converting various vectors of the data signal into corresponding codes, and a training signal that is transmitted at the start of communication. In a data transmission device, the signal vector received when receiving the training signal and the transmission path are a coding error detection means for determining the error from the original vector when there is no signal distortion; and based on the detected error, the transmission quality, which is the margin against noise on the transmission path at the data transmission speed at that time, is determined. transmission quality determination means; shift-down procedure execution means for shifting down the data transmission speed when the determined transmission quality is less than a certain quality; A data transmission device comprising: data receiving means for receiving data. (2) The modem includes the encoding error determining means, the transmission quality determining means, and the transmission quality determining means, and the determined transmission quality is determined by determining the number of "1" bits within the fixed number of bits. transmission quality evaluation value generation means for converting the transmission quality evaluation value data into transmission quality evaluation value data indicating deterioration of the transmission quality as the number increases; 2. The data transmission device according to claim 1, further comprising output data selection means for outputting data.