JP2002319878A - Data transmission equipment - Google Patents

Abstract

(57) [PROBLEMS] In a data transmission device using a power line as a transmission line, noise near the power line voltage level of 0 V causes the demodulation capability of the demodulation unit to deteriorate, and the power line voltage level is periodically reduced to 0 V. Data errors occur. A detection circuit of a transmission device detects a timing at which a power line voltage becomes 0 V, and sets a modulation method of a modulation unit to a modulation method having high noise resistance for a predetermined time before and after the detected timing. Make changes and submit the data. The receiving device 2 detects the timing at which the power line voltage becomes 0 V by the detection circuit 24, and changes the demodulation method of the demodulation unit 21 to the modulation method changed by the modulation unit 11 for a predetermined time before and after the detected timing. Change to the corresponding demodulation method and output the received data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device in power line communication, and more particularly to a data transmission device with few data errors.

[0002]

2. Description of the Related Art Conventionally, power line communication is a system in which a 100 V power line of a commercial frequency is used for an information transmission line.
Since the power lines drawn into all ordinary homes are used as transmission lines, there is an advantage that it is not necessary to newly install information transmission lines. FIG. 3A is a schematic configuration diagram illustrating an example of a conventional data transmission device in power line communication. As shown in the figure, the present device includes a transmitting device 5 including a modulating unit 51, a D / A converter 12, and an analog front end unit 13, a demodulating unit 61, an A / D converter 22, and an analog front end unit. Receiving device 6 comprising
It is composed of The analog front end unit 13 couples the output of the D / A converter 12 to a power line, and the analog front end unit 23 takes in a transmission signal on the power line to the receiving device 6.

In FIG. 1, digital data input to a transmitting device 5 is modulated by a modulation unit 51 by a predetermined modulation method and output to a D / A converter 12. The signal input in the D / A converter 12 is converted into an analog signal, and the analog signal is coupled to a power line in the analog front end unit 13 and transmitted. The transmission data on the power line is received by the analog front-end unit 23 of the receiving device 6, an analog data signal is extracted, and output to the A / D converter 22. This analog signal is supplied to the A / D converter 2
The digital signal is converted into a digital signal at 2 and demodulated into digital data by a demodulation unit 61 in a demodulation method corresponding to the modulation method of the modulation unit 51 and extracted.

[0004]

Normally, in the above data transmission, the modulation scheme in the transmitting apparatus is determined to be the optimum modulation scheme by initial training prior to data transmission. However, the above-mentioned 100 V line of the power line is operated by connecting various electric devices to a connector or an outlet laid on the 100 V line. Road quality. FIG. 3B is a diagram illustrating an example of noise in the output of the analog front end unit 23 of the receiving device 6 when the power line power supply frequency is 50 Hz. The point where the voltage waveform of the AC 100 V crosses the 0 V level (zero cross point) ) Shows periodically generated noise. As shown in the figure, this noise is generated at a period of 10 ms because the power supply frequency is 50 Hz. Accordingly, as described above, in the conventional power line communication, the noise on the power line causes the output of the analog front end unit to be periodic (1 at the power frequency of 50 Hz).
There is a disadvantage that the demodulation performance is degraded due to noise generated at a period of 0 ms and a data error occurs. The present invention has been made to solve the above problems,
It is an object of the present invention to provide a data transmission device that reduces data errors that occur periodically in power line communication.

[0005]

According to a first aspect of the present invention, there is provided a transmitting apparatus for modulating transmission data in a predetermined manner by a modulating means and transmitting the modulated data via a power line. And a receiving device that demodulates and outputs the data received by the demodulation unit and outputs the demodulated data. The modulation method can be changed based on the predetermined time based on the timing information from the second detection means for detecting the timing at which the voltage level of the power line becomes 0 V. The demodulation method can be changed to a demodulation method corresponding to the modulation method changed by the modulation means.

According to a second aspect of the present invention, there is provided a transmitting apparatus for transmitting, via a power line, transmission data which has been error-correction-coded by an error-correction coding means, and an error correction apparatus for correcting data received via the power line. In a data transmission device including a reception device including a decoding unit, the error correction coding unit determines a predetermined time based on timing information from a detection unit that detects a timing at which a voltage level of a power line becomes 0 V. The error correction coding method can be changed, and the error correction decoding means performs error correction for a predetermined time based on timing information from the second detection means for detecting the timing at which the voltage level of the power line becomes 0V. The decoding method can be changed to a method corresponding to the error correction coding method changed by the error correction coding means.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a data transmission device according to the present invention. As shown in FIG. 1, the data transmission apparatus according to the present invention is a transmission apparatus including a modulation unit 11, a D / A converter 12, an analog front end unit 13, and a detection circuit 14 for detecting the 0 V level of the power line voltage. 1, a receiving device 2 including an analog front end unit 21, an A / D converter 22, a demodulation unit 23, and a detection circuit 24 for detecting the 0 V level of the power line voltage. And the modulation unit 1
Reference numeral 1 denotes a modulation unit that can change digital data from a predetermined modulation method to another modulation method and modulate the digital data for a predetermined time during data transmission. The demodulation unit 21 changes the demodulation of digital data from a predetermined demodulation method to a demodulation method corresponding to the modulation method changed by the modulation unit 11 for a predetermined time during the data transmission, and converts the data. It is a demodulation unit that can demodulate.
The functions and operations of the D / A converter 12, the analog front end units 13, 21 and the A / D converter 22 are the same as those of the components denoted by the same reference numerals in FIG.

In FIG. 1, digital data input to a transmitting apparatus 1 is modulated by a modulation section 11 according to a predetermined scheme, for example, a 16PSK modulation scheme having a high transmission efficiency, and is subjected to D-modulation.
/ A converter 12. The digital signal input to the D / A converter 12 is converted into an analog signal, and is further coupled to a power line in an analog front end unit 13 and transmitted. On the other hand, the detection circuit 14 detects the timing at which the voltage level of the power line crosses 0 V, and transmits the detected timing information to the modulation unit 11. Having obtained this information, the modulation unit 11 modulates the transmission data for a predetermined time before and after the timing detected by the detection circuit 14 by changing the modulation method to a high noise-resistant one, for example, the BPSK modulation method. Then, the signal is output to the D / A converter 12 and transmitted to the receiving side via the analog front end unit 13.

The data signal transmitted via the power line is
The signal is received and taken out by the analog front end unit 23 of the receiving device 2 and output to the A / D converter 22.
The analog signal input to the A / D converter 22 is converted into a digital signal, and further demodulated by a demodulation unit 23 using a demodulation method corresponding to the 16PSK modulation method in the transmission-side modulation unit 11 to obtain digital reception data. Is output as On the other hand, the detection circuit 24 detects that the power line voltage level is 0 V
And transmits the detected timing information to the modulation unit 11. During a predetermined time before and after this timing, a signal modulated by the changed BPSK modulation method is transmitted from the transmission side.
The demodulation unit 21 performs demodulation by changing to a demodulation method corresponding to the demodulation method. Note that the predetermined modulation method and the modulation method to be changed are:
The optimal scheme is determined from the relationship between the error rate and the transmission rate by initial training prior to data transmission. If the modulation method is changed to a method with high noise immunity in the middle of data transmission as described above, periodic data errors caused by power line noise can be reduced and high quality data transmission can be performed. it can.

FIG. 2 is a schematic configuration diagram showing a modified embodiment of the data transmission apparatus according to the present invention. As shown in the drawing, the data transmission apparatus according to the present embodiment includes an error correction code unit 15, a modulation unit 16, a D / A converter 12, an analog front end unit 13, and a detection unit that detects the 0 V level of the power line voltage. A transmission device 3 comprising a circuit 14; a reception device comprising an error correction decoding unit 25, a demodulation unit 26, an A / D converter 22, an analog front end unit 23, and a detection circuit 24 for detecting the 0 V level of the power line voltage. And 4. The error correction coding unit 15 is an error correction coding unit that can change the error correction coding method from a predetermined method to another method and perform coding for a predetermined time during data transmission. The error correction decoding unit 25 includes:
An error correction decoding unit capable of changing a predetermined error correction decoding method to an error correction decoding method corresponding to the error correction coding method changed by the correction coding unit 15 for a predetermined time. Further, the modulator 16 and the demodulator 26 modulate transmission data by a modulation method determined by the system and demodulate the modulated wave. Note that the D / A converter 12, the analog front end units 13, 23, and the detection units 14, 2
The functions and operations of the A / D converter 4 and the A / D converter 22 are the same as those in FIG.

In FIG. 1, a digital transmission data input to a transmission device 3 is converted into an error correction code by a predetermined method determined by the system in an error correction code unit 15, for example, a convolutional code having a coding rate of 3/4. Is added to the data and output to the modulation unit 16, modulated in the modulation unit 16, and output to the D / A converter 12. The modulated signal input to the D / A converter 12 is converted into an analog signal, and is coupled from the analog front end unit 13 to a power line and transmitted. On the other hand, the detection circuit 14 detects the timing at which the voltage level of the power line crosses 0 V, and transmits this timing information to the error correction coding unit 15. The error correction coding unit 15 having obtained this information sets the error correction coding method to a convolution with a high noise resistance, for example, a coding rate of 1/2, for a predetermined time before and after the timing detected by the detection circuit 14. The code is changed to the error correction coding method and transmitted.

In the receiving device 4, an analog front end section 23 receives and extracts a transmission signal transmitted from the transmitting device 3 via a power line, converts the signal into a digital signal in an A / D converter 22, and demodulates the signal. Output to the unit 26. The demodulation unit 26 demodulates the data according to the system defined by the system and outputs the demodulated data to the error correction decoding unit 25. The error correction decoding unit 25 corrects the error by a Viterbi decoding method using a convolutional code having a coding rate of 3/4 and outputs the data. On the other hand, the detection circuit 24 detects the timing at which the voltage level of the power line crosses 0 V, and transmits this timing information to the error correction decoding unit 25. The error correction decoding unit 25 having obtained this information performs a decoding method corresponding to the error correction coding method changed on the transmission side for a predetermined time before and after the timing detected by the detection circuit 14, that is, the coding method. The data is changed to a Viterbi decoding method using a rate 1/2 convolutional code to correct data errors and output as received data. In addition, the predetermined error correction coding method, the error correction coding method to be changed, and the corresponding error correction decoding method are determined by the initial training prior to the data transmission from the relationship between the error rate and the transmission rate. Is done.

According to the above-described method, a data error caused by noise that periodically occurs near the power line voltage level of 0 V is corrected by a method having a high correction capability although the data transmission efficiency is temporarily reduced. Since data can be extracted, high-quality data transmission can be performed. In addition,
In the above description, as a means for reducing data errors caused by periodically occurring noise, a method of separately changing the modulation method or the error correction coding method to a method having high noise resistance has been described. It is a matter of course that even higher quality data transmission can be performed by the combination.

[0014]

As described above, according to the present invention,
For a data transmission device in power line communication in which demodulation performance is periodically deteriorated due to noise at a voltage 0 level on a power line and a data error occurs, a timing at which the periodic data error occurs is detected. The modulation system or the error correction coding system can be changed to a system that can reduce the occurrence of data errors only for a predetermined time before and after the timing. As a result, the present invention can greatly contribute to providing a high-quality data transmission device with high noise immunity to a data transmission system using a power line widely spread throughout the country as a transmission path.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a data transmission device in power line communication according to the present invention.

FIG. 2 is a schematic configuration diagram showing a modified example of a data transmission device in power line communication according to the present invention.

FIG. 3A is a schematic configuration diagram illustrating an example of a data transmission device in a conventional power line communication, and FIG. 3B is a diagram illustrating noise in an output of an analog front end unit of a reception device when a power frequency of a power line is 50 Hz. It is a figure showing the example of.

[Explanation of symbols]

1, 3, 5,... Transmitting device, 2, 4, 6,.
Receiving device, 11, 16, 51... Modulation section, 12.
.D / A converter, 13, 23 .. Analog front end part, 21, 26, 61 .. Demodulation part, 22..A
/ D converter, 14, 24 · · · detection circuit, 1
5 ··· Error correction code section, 25 ··· Error correction decoding section

Claims (2)

[Claims] 1. A transmitting apparatus for modulating transmission data in a predetermined manner by a modulating means and transmitting the data via a power line, and a receiving apparatus for demodulating data received via the power line by a demodulating means and outputting the data. In the power line data transmission device, the modulation means can change the modulation method for a predetermined time based on timing information from the detection means for detecting the timing at which the voltage level of the power line becomes 0 V; Can change the demodulation method to a demodulation method corresponding to the modulation method changed by the modulation means for a predetermined time based on timing information from the second detection means for detecting the timing at which the voltage level of the power line becomes 0 V A data transmission device, characterized in that: 2. A transmitting apparatus for transmitting, via a power line, transmission data that has been error-corrected and encoded by an error-correcting encoding means, and a receiving apparatus having an error-correcting decoding means for performing error correction on data received via the power line. Wherein the error correction coding means can change the error correction coding scheme for a predetermined time based on timing information from the detection means for detecting the timing at which the voltage level of the power line becomes 0 V. Wherein the error correction decoding means comprises:
For a predetermined time based on timing information from the second detection means for detecting the timing at which the voltage level of the power line becomes 0 V, the error correction decoding method corresponding to the error correction encoding method in which the error correction encoding means has changed. A data transmission device characterized by being changeable to a system.