JPH0746216A - Data transmission method - Google Patents

Abstract

(57) [Abstract] [Object] The present invention eliminates the influence of echo and group delay distortion generated in a line used for data transmission, thereby eliminating the need for an echo canceller and an equalizer and reducing the level fluctuation of the line. An object of the present invention is to provide a narrowband full-duplex data transmission method and device having a correcting function. A frequency band of a communication line for transmitting data information is divided into a data transmission frequency band for transmitting data information and a data receiving frequency band for receiving data information, Data information is transmitted by a plurality of carriers having different frequencies. [Effects] According to the present invention, the device using the narrow band full-duplex data transmission system of the present invention is not affected by the echo and group delay distortion generated in the line used for data transmission. Full-duplex data transmission is easily possible by connecting to. Further, the pilot tone enables signal level correction, and enables full-duplex data transmission with a low data error rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method in which a voice communication has a narrow frequency band.

[0002]

2. Description of the Related Art In recent years, data transmission using a digital transmission system
The spread of communication services is remarkable.

For this data communication service, it is desirable to use an ISDN (Integrated Service Digital Network) line, which is a digital network, but the ISDN line is not well maintained and the existing analog line must be used. The reality is that we cannot get it.

When performing a data communication service using this analog line, that is, a general telephone line, ISDN is used.
It is necessary to take into consideration various data errors caused by the fact that the usable frequency band is narrowly limited as compared with the line and that the communication system is constructed by the line switching of 2 lines / 4 lines.

The cause of the data error is, for example, the group delay distortion caused by the limitation of the frequency band of the line or the 2-line /
There is an echo that occurs when switching between four lines, and each is generally corrected by an equalizer or an echo canceller.

As is well known, the echo canceller creates a pseudo echo signal identical to a signal to be an echo, and subtracts the pseudo echo signal from a signal containing an echo to cancel the echo. The normal size is about one chip.

As a document related to this, Japanese Unexamined Patent Publication No.
There is a Japanese Patent No. 60235, but this is adapted to the degree of the generated echo by providing the echo canceller of the terminal body with a learning function, and no reference is made to the echo generated in the transmission path used. Absent.

Further, as well known, the equalizer removes group delay distortion by absorbing a difference in transmission time in the frequency domain caused by the frequency band limitation of the line.

[0009]

However, in order to completely remove these echoes and group delay distortions, it is necessary to install a dedicated device adapted to the transmission path used, and furthermore, to eliminate the echoes and group delay distortions. The degree depends on the line path and line distance used for data communication, and in order to electrically remove these, it is necessary to install a dedicated echo canceller or equalizer in all the line switches or the terminal body.

In the communication system in which the echo canceller and the equalizer described above are installed, there is a big economical problem, and it is said that these devices become large in size by being dedicated for each line to be used and lose their versatility. There is also a problem.

Therefore, an object of the present invention is to provide a new data transmission method which is not affected by echo and group delay distortion.

It is another object of the present invention to realize a new data transmission method which is not affected by echo and group delay distortion with a simple device configuration.

A further object of the present invention is to provide a data transmission method which also has a function of correcting the level fluctuation of a telephone line.

[0014]

Therefore, the present invention provides a data transmission method for transmitting data information in order to provide a new data transmission method which is not affected by echo and group delay distortion. In the frequency band and the data receiving frequency band for receiving the data information, the data information is transmitted by a plurality of carrier waves.

Further, according to the present invention, in order to realize a new data transmission method which is not affected by echo and group delay distortion with a simple device configuration, the arrangement of the carrier waves is determined by the demodulation time of data. .

Further, according to the present invention, data transmitting means for transmitting data information by a plurality of carrier waves, integrating means for extracting the phase vector of the carrier wave, demodulating means for demodulating the phase vector, and phase of the carrier wave. This is a configuration including a synchronization processing unit that extracts a modulation point.

Further, according to the present invention, in order to provide a data transmission method having a function of compensating for level fluctuation of a telephone line, data information is sent by arranging pilot tones on at least one of a plurality of carriers. The data information sent by the carrier wave is demodulated by comparing the signal level of the phase vector of the power carrier wave with the phase vector of the carrier wave that is the pilot tone.

[0018]

That is, in the data transmission frequency band for transmitting data information and the data reception frequency band for receiving data information, the data information is transmitted by a plurality of carrier waves. , Data communication that is not affected by echoes and group delay distortion that occur depending on the line distance used and the line route.

Furthermore, since the arrangement of the carrier waves is determined according to the data demodulation time, data transmission can be realized with a simple data transmission device. Moreover, since a plurality of carrier waves are used, the time required for data demodulation is increased, thereby realizing data transmission with a low data error rate.

Further, by arranging pilot tones on at least one of the plurality of carriers, the carrier of the carrier is transmitted by comparing the signal levels of the phase vector of the carrier to be transmitted with the data information and the phase vector of the carrier which is the pilot tone. Since the data information is demodulated, even if a level fluctuation occurs in the communication line, it is not affected, that is, data transmission with a low data error rate due to the level fluctuation is realized.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a plurality of 16-value quadrature amplitude modulated carriers (16QA) in a predetermined frequency band.
It is the carrier wave distribution diagram when M) is transmitted. The vertical axis in the figure is the signal level of the carrier wave, and the horizontal axis is the frequency band.

When transmitting a plurality of carrier waves: Cn [pieces] in such a constant frequency band, the frequency bands occupied by the individual carrier waves are arranged without overlapping each other.

That is, the modulation rate of each carrier: Vbaud
[Baud] is the frequency band used for data transmission: B
The following relationship is required for e [Hz] and the frequency interval Fd [Hz] for arranging individual carrier waves in the non-modulated state.

[0025]

[Formula 1] Vbaud ≦ Be / Cn

[0026]

## EQU00002 ## Fd.gtoreq.Vbaud To receive a plurality of carriers under the above conditions, for example, a circuit shown in FIG. 4 described later separates the carriers into individual carriers and demodulates them.

However, in order to perform the separation / demodulation by the circuit shown in FIG. 4, the following three conditions are the minimum requirements.

(A) Frequency interval between individual carriers: Fd
Make [Hz] even intervals.

(B) The frequency of each carrier is Fd / 2.
Set it to an integral multiple of [Hz] or Fd [Hz].

(C) The integration time at the time of demodulation is 1 / Fd [s]
To

Thus, a plurality of carrier waves can be received by a simple receiving circuit including an integrating section and a demodulating section.

The above conditions (a) and (b) are conditions for integrating any one of a plurality of carrier waves in each of the integrators shown in FIG. 4, that is, (a) and (b). )
When the carrier to be transmitted satisfies the condition of, each integrator multiplies the transmitted composite wave by the sine wave and the cosine wave of the frequency of the arbitrary carrier to be integrated, and thereby the phase of the arbitrary carrier Extract the vector.

FIG. 2 shows a demodulation method considering group delay distortion.

FIG. 2 shows demodulation (integration) time of a plurality of carriers including group delay distortion, and FIG.
2 shows the respective delay times, and FIG. 2B shows the group delay distortion caused by the delay. In the figure, f is the frequency of the carrier wave, t is the time delay of the carrier wave, and 1 / Vbaud
Is one modulation of the phase-modulated carrier.

In the present invention, the group delay distortion is not corrected by the equalizer, and the time for demodulating the received signal, that is, the time for demodulating the data is set to a period in which the group delay distortion is not affected, and the group delay distortion is set. It enables data transmission that is not affected by distortion.

In order to remove the influence of the group delay distortion, the carrier modulation time at the time of reception: 1 / Vbaud [s], the integration time for demodulating the data: 1 / Fd [s], and the group delay distortion Occurs, that is, the waveform deformation time due to group delay distortion: T [s]
The following relations are required.

[0037]

## EQU00003 ## 1 / Vbaud-1 / Fd.gtoreq.T In other words, according to the equation (3), data demodulation is performed only on the waveform component for one modulation of the transmission waveform shown in FIG. It is a thing.

Based on the above conditions for data transmission and data demodulation, a method of arranging a plurality of carriers will be described with reference to FIG.

FIG. 1 shows data communication using 48 kinds of quadrature amplitude modulated carriers (16QAM). The modulation speed: Vbaud [baud] is Vbaud ≦ 1 according to the equation (1).
It becomes 460/48. Here, it is assumed that the modulation speed is Vbaud = 25 [baud] so as to satisfy Expression (1).

Next, in consideration of the equations (2) and (3) and the conditions at the time of demodulation, the interval of each carrier: Fd = 27.5 [H
z]. Further, according to the condition (b) at the time of demodulation, 48 types of carrier waves are arranged from 440 (= 27.5 × 16) [Hz] at 27.5 [Hz] intervals.

This time, data communication is performed using 48 kinds of 16-valued quadrature amplitude modulation waves (16QAM) that are phase-modulated at a modulation speed of 25 [baud].
It enables data communication of 4800 (= 25 × 4 [bit] × 48) [BPS].

However, this is in consideration of the circuit shown in FIG. 4, and by changing the numbers of the modulation section, the integration section and the demodulation section shown in FIG. 4, it is possible to combine carrier waves of various patterns according to the above conditions. Exists. Of course, in the circuit shown in FIG. 4 as well, there are combinations of carrier waves having various patterns.

FIG. 4 shows an embodiment of the data transmission terminal.

FIG. 4 shows a data interface section 100 for converting a serial transmission signal into a parallel signal for each modulation section at regular time intervals, and a pilot tone generation section 200 for generating a pilot tone signal which is a signal level comparison with a carrier wave. A modulator 300 to 347 for converting the parallel signal into a carrier for data transmission, a combiner 400 for combining the carriers from the modulator, a modulation rate of the carrier and the constant in the data interface. A timing generation unit 500 that determines time, a data transmission unit including an analog interface unit 600 that transmits the combined carrier wave, an analog interface unit 601 that distributes the received signal to an integration unit and a synchronization processing unit, and a received signal. Integrator 700 that extracts the phase vector of any carrier included 48, demodulators 800 to 847 that demodulate the phase vector from the integration unit, a synchronization processing unit 900 that determines the integration start and end times of the integration unit by extracting the phase modulation point of the carrier wave that is the received signal, the demodulation The data transmission terminal includes a data receiving unit including a data interface unit 101 that converts a transmission signal from the unit into a serial signal. The analog interface unit and the data interface unit in the data transmitting unit and the data receiving unit may be the same in structure.

The above data transmission terminal transmits a plurality of carrier waves shown in FIG.

FIG. 3 shows an embodiment in which a carrier modulated by a four-phase phase shift system, which is a pilot tone, is superimposed on the plural carriers shown in FIG.

First, the transmission data is input to the data interface section 100. The input serial signal is converted into a 4-bit parallel signal according to a constant clock sent from the timing generator 500, and the modulators 300 to 3
Send to 47. Here, 4 bits means the number of bits that can be transmitted by one-time modulation of a carrier that has been subjected to 16-value quadrature amplitude modulation (16QAM).

Further, assuming that the phase modulation speed in the modulator is 25 [baud], in order to perform data communication of 4800 [BPS], the data is taken in from the data interface unit 100 to the modulator by 1/25. It is implemented with a clock in [s] unit.

Similarly, the pilot tone generator 200 also generates a carrier (QPSK wave) modulated by the four-phase phase shift method with a phase modulation speed of 25 [baud] as a pilot tone.

The modulators 300 to 347 are, for example, the modulator 3
00 is a unique reference frequency 440 [Hz], modulator 301
Is 467.5 [Hz], and the modulator 302 is 495 [Hz]
As described above, each of them is arranged so as to output a carrier having a unique reference frequency at an interval of 27.5 [Hz].

The 48 types of carrier waves and the pilot tones, which are phase-modulated by the modulators 300 to 347, are sent to the synthesizer 400 momentarily and are synthesized. The combined carrier wave is transmitted through the analog interface unit 600 to ch1 (for example, 300 to 1) which is a frequency band for data transmission.
760 [Hz]).

In data reception, the carrier wave to be received is the analog interface unit 601 and the integration unit 70.
0 to 748 and the synchronization processing unit 900, and input in parallel.

The integrator extracts each carrier wave to be received from the received signals input in parallel. The integrator starts integration of the carrier wave by the clock sent from the synchronization processing unit 900 so as to remove the waveform component affected by the group delay distortion. Further, by setting the integration time in the integration unit to 1 / 27.5 [s], accurate data (phase vector) without the influence of group delay distortion is transmitted to the demodulation units 800 to 847. In the demodulation section, the demodulation data is determined by comparing the phase vector of each carrier wave sent from the integration section with the phase vector of the pilot tone sent from the pilot tone integration section (for example, integration section 700). The data demodulated in this way is sent to the data interface unit 101,
After converted into serial data, it becomes the received data.

The above is a series of operation principles. Here, the demodulation method of the phase vector of the demodulator is shown in FIG.

FIG. 5 shows a signal point distribution of a carrier wave (16QAM) which is quadrature amplitude modulated and a signal point distribution of a pilot tone which is a carrier wave (QPSK) modulated by the 4-phase phase shift method.

The signal level of the carrier wave modulated by 16-valued quadrature amplitude appears at the position of 1 or 3 from the origin, whereas the signal level of the carrier wave modulated by the four-phase phase shift method. The size of the level is displayed at the position of distance from the origin: 2. That is, the amplitude of the carrier wave which is 16-valued quadrature amplitude modulation for data transmission,
The amplitude ratio of the carrier wave modulated by the 4-phase phase shift method, which is a pilot tone, is set to about 1: 2: 3, and the phase vector of the carrier wave modulated by 16-value quadrature amplitude modulation is changed to the 4-phase phase shift method. It is to determine whether the signal level of the phase vector itself is 1 or 3 by comparing it with the phase vector of the carrier wave modulated by. Demodulate.

That is, even when the signal level changes in the line, the magnitude relationship of the signal level to the pilot tone is preserved, and the cause of the data error caused by the line level change is removed.

Up to now, the data transmission method in the case where the echo canceller and the equalizer are unnecessary has been described. However, the present data transmission method for obtaining a data transmission rate of 4800 BPS by 48 carriers, When comparing the data transmission method of 4800 BPS with a single carrier,
For example, assuming that the modulation of the carrier is performed by 16-value quadrature amplitude modulation, the modulation rate of each carrier in this data transmission method is 25 [baud], and the modulation of a single carrier in the latter data transmission method. The speed is 1200 [baud]. In other words, the modulation speed of each carrier wave in this data transmission method is 1/48 of the latter.

Therefore, in this data transmission method, the time that can be applied to the data demodulation is 48 times that in the latter case, which is 33 [dB] (= 20log4) though it is a simple calculation.
The S / N of 8) can be improved, and data transmission that is resistant to noise, that is, has a low data error rate, becomes possible.

[0060]

As described above, according to the present invention, data transmission that is not affected by echo and group delay distortion is possible, and full duplex is easily achieved by connecting a simple device to the telephone line. Achieve data transmission.

Furthermore, by adding a pilot tone, the signal level can be corrected, and data transmission having a function of correcting the level fluctuation of the communication line is also possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of data transmission using a plurality of carriers.

FIG. 2A is a diagram showing a plurality of carriers including group delay distortion and a data demodulation time unaffected by the carriers. FIG. 6B is a diagram showing a composite wave of carrier waves including a plurality of group delay distortions and a data demodulation time that is not affected by the composite wave.

FIG. 3 is a diagram showing an embodiment of data transmission in which pilot tones are superimposed on a plurality of carriers.

FIG. 4 is a configuration diagram of a data transmission device.

FIG. 5 is a signal point arrangement diagram in which a carrier modulated by the 4-phase phase shift method is added to a carrier modulated by 16-value quadrature amplitude.

[Explanation of symbols]

 100, 101 ...... Data interface section 200 ...... Pilot tone generation section 300 to 347 ...... Modulation section 400 ...... Synthesis section 500 ...... Timing generation section 600,601 ...... Analog interface section 700 to 748 ...... Integration section 800 〜 847 ... Demodulation unit 900 ... Synchronization processing unit

Claims (10)

[Claims] 1. A frequency band of a communication line for transmitting data information is divided into a frequency band for data transmission for transmitting data information and a frequency band for data reception for receiving data information. Then, the data transmission method is characterized in that the data information is transmitted by a plurality of carrier waves having different frequencies. 2. A data transmission method, wherein when transmitting data information by a plurality of carriers, an arbitrary frequency interval for arranging the plurality of carriers is determined according to a demodulation time of the carriers. 3. A frequency band of a communication line for transmitting data information is divided into a frequency band for data transmission for transmitting data information and a frequency band for data reception for receiving data information. In the data transmission method, the data information is transmitted by a plurality of carriers, and the frequency intervals at which the plurality of carriers are arranged are determined by the demodulation time of the carriers. 4. The data transmission method according to claim 2, wherein the frequency interval is equal to the reciprocal of the demodulation time. 5. At least one of a plurality of carriers is a pilot tone, and by comparing the signal level of the pilot tone with the signal level of the carrier,
4. The data transmission method according to claim 1, 2, or 3, wherein the phase-modulated carrier wave is demodulated. 6. A data transmission section including data transmission means for transmitting data information by a plurality of carrier waves having different frequencies,
Synchronization processing means for extracting a phase modulation point of the carrier wave; integration means for starting integration of the carrier wave from the phase modulation point extracted by the synchronization processing means to extract a phase vector of the carrier wave; A data transmission system comprising a data receiving section including a demodulating means for demodulating a vector. 7. A pilot tone generating means for generating a pilot tone signal for comparing the signal level of the carrier, further comprising a phase vector of the carrier by comparing a phase vector of the carrier with a phase vector of the pilot tone. 7. The data transmission system according to claim 6, further comprising means for demodulating a vector. 8. A data transmission section including data transmission means for transmitting data information by a plurality of carrier waves having different frequencies,
Synchronization processing means for extracting a phase modulation point of the carrier wave; integration means for starting integration of the carrier wave from the phase modulation point extracted by the synchronization processing means to extract a phase vector of the carrier wave; A data demodulation system comprising a data receiving unit including demodulation means for demodulating the carrier by comparing the signal level of the carrier phase vector with that of a carrier which is a pilot tone. 9. A carrier wave for transmitting the data information is a carrier wave which is 16-valued quadrature amplitude modulation, and a carrier wave which is a pilot tone is a carrier wave which is modulated by a 4-phase phase modulation method. 9. The 16-value quadrature amplitude modulated carrier is demodulated by comparing the phase vector of the modulated carrier with the phase vector of the carrier modulated by the 4-phase phase shift method. Data demodulation method. 10. A frequency band of a communication line for transmitting data information is divided into a data transmission frequency band for transmitting data information and a data receiving frequency band for receiving data information. Data transmission by transmitting data information by a plurality of carriers including at least one pilot tone, the plurality of carriers are arranged at frequency intervals equal to the reciprocal of the demodulation time of the carrier, and the carriers are the pilot tones. And a signal level of the carrier wave is demodulated by comparing the signal level of the carrier wave with the signal level of the carrier wave.