JPH06291700A - Line quality measuring instrument - Google Patents

Abstract

PURPOSE:To secure transmission quality by measuring the line quality of a lamp line when the lamp line is used as a transmission line for data transmission. CONSTITUTION:A test data transmission part 20 inputs test data from a test data generator 2 to a multiplier 5, performs spread spectrum processing by spread codes from a spread code series generator 3, and sends the data out to the lamp line 40. A reception part 30 inversely spreads the received data by a multiplier 12, makes a symbol comparison with transmission-side data by a comparing and calculating circuit 15, and calculates error symbols to measure the transmission quality of the line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line quality measuring device for measuring the line quality of a data transmission system using a power line as a transmission line.

[0002]

2. Description of the Related Art Electric power lines (low-voltage distribution lines) are used in homes, offices,
It is an electric circuit that is spread over all facilities such as factories and stores. Needless to say, it is for distribution of commercial power, but since the secondary side of the distribution transformer is spread over a wide area, this It is partly performed to superimpose signals for communication. However, the power line is 50-60Hz
Since it is expanded for the purpose of transmitting commercial power between the lines, the transmission characteristics with respect to high frequencies are unclear in both the lines and the earth return path, and it is difficult to continue stable transmission of high frequency signals. Communication equipment using power lines is used in a limited field, but it is generally not widely used because the fluctuation or deterioration of the line quality due to the instability of the high frequency transmission characteristics for communication is large. is there. As one method for solving this, a spread spectrum communication means has been proposed, and for this purpose, the spectrum of the transmission signal is spread and spread in the frequency band of 10 to 450 kHz permitted by the law for the power line. A method for improving quality has been announced. The following is an example of a document relating to this spread spectrum system. (A) Shinichi Tachikawa, Gen Marubayashi; “DS / SS method for simultaneously transmitting reference PN sequences suitable for power line data transmission”, IEICE Transactions (B-II) J74-B-
II No.5 (b) Endo Kaoru, Nakamura Tadashi, Tsumura Soichi, Tsuruta Shichiro: "Spread spectrum power line communication method", IEICE Transactions (B-II) J74-B-II No.5

[0003]

When performing data communication using a power line as a transmission line, it is possible to improve the transmission quality by adopting a spread spectrum method, but the power line has various types unrelated to high frequency transmission. Since the electric appliances are connected in parallel and are affected by the line quality that fluctuates with time, there is a problem that it is not possible to always transmit with a constant quality. In addition, the spread spectrum method is
If the spreading factor is large, the processing gain is large, but if the transmission bandwidth is constant, if the spreading factor is large, the data transmission rate decreases in inverse proportion to it. Therefore, the transmission efficiency is improved by changing the spreading factor according to the fluctuation of the line quality and decreasing the spreading factor when the line quality is good and increasing the transmission speed, and increasing the spreading factor when the line quality is low and transmitting at the low speed. be able to. However, in order to change the spreading factor according to the state of the line, it is necessary to constantly monitor the transmission quality of the line, but in order to evaluate the transmission quality for all available bands using conventional analog elements. Has a problem that the circuit configuration is complicated and expensive.

An object of the present invention is to solve the above-mentioned problems and to maintain the transmission quality in a good state at all times and improve the transmission efficiency when communicating by a spread spectrum method using a power line as a transmission line. It is to provide a line quality measuring device capable of detecting the line quality of the transmission line. Further, the present invention provides a means for easily collecting basic data for using a power line as a communication medium, which has been difficult to perform stable communication in the related art.

[0005]

The line quality measuring device of the present invention is spread spectrum in order to measure the line quality of the transmission line when performing data communication by the spread spectrum system using a low voltage distribution line as the transmission line. It is composed of a transmitting unit that sends a digital test signal to the low-voltage distribution line and a receiving unit that receives the test signal from the transmitting unit via the low-voltage distribution line, and the transmitting unit generates a test data sequence. A test data generator that outputs the number of symbols, and a spreading sequence that generates a code sequence of a plurality of bits for each symbol of the test data sequence and outputs a spreading code that can arbitrarily change the length of the code sequence. A generator, a first multiplier that spreads the test data sequence by the spread code, and a spectrum-spread data sequence from the first multiplier that is used as the test signal. A first line coupler for sending to the low-voltage distribution line, and a control circuit for giving a synchronization signal to the test data generator and the spreading sequence generator, and the receiving unit includes the low-voltage distribution line for the test. A second line coupler for taking in a signal; a despreading sequence generator that outputs a spreading code equal to the spreading code of the first spreading sequence generator in synchronization with a synchronization signal from the control circuit; A second multiplier for despreading the test signal output from the second line coupler by the spreading code from the despreading sequence generator to output received data in which symbols are restored; and the second multiplier And a comparison calculation circuit for comparing the symbol of the received data from the symbol with the symbol from the test data generator to calculate and output the error rate.

Further, a synchronization signal generator for generating a synchronization signal is provided in the transmission section, and a synchronization circuit is provided to the output from the first multiplier by a coupling circuit provided between the first multiplier and the line coupler. A synchronizing signal from a generator is added, a synchronizing signal detector and a comparison data generator are provided in the receiving section, and branched by a branch circuit provided between the second line coupler and the second multiplier. The signal is input to the sync signal detector, the sync signal is detected and given to the despreading sequence generator and the comparison data generator, and the comparison data generator gives the test data equal to the test data generator to the comparison calculation circuit. It is characterized by being configured.

Further, the error rate obtained from the comparison calculation circuit of the receiving section is given to the control circuit of the transmitting section as a spreading sequence length control signal for changing the length of the spreading sequence, and the error rate exceeds the standard value. At this time, the length of the code sequence generated by the spreading sequence generator is extended until the error rate becomes equal to or less than the standard value.

Further, the transmitting section is provided with a modulator for modulating the phase or frequency of the carrier wave by the output of the test data generator and then inputting it as test data to the first multiplier, and the receiving section is provided with the second modulator. A demodulator for demodulating an output of the multiplier to extract a symbol of received data and inputting the symbol to a comparison calculation circuit is provided. In other words, the most important feature is to evaluate the line quality for the entire allowable transmission band of the power line, obtain the maximum transmission rate according to the line quality, and measure the transmission line quality over the entire usable band. .

[0009]

1 is a block diagram showing a first embodiment of the present invention. In the figure, 20 is a transmitter, 40 is a power line as a transmission line, and 30 is a receiver. First, the transmitter 20
Will be described. In the figure, reference numeral 1 is a control circuit for setting an initial value of a spreading sequence and determining a data transmission rate.
2 is a test data generator, for example, 511 (= 2 ⁹ -
1) Generate a pseudo-random sequence such as a M sequence of bits (maximum period sequence). 3 is a spreading sequence generator, and the length of the generated sequence is variable, for example, 7 (= 2 ³ −
It is possible to set M sequences from 1) to 1023 (= 2 ¹⁰ -1). The clock frequency of the spread spectrum generator 3 is selected to be 450 kHz or less so that the spectrum of the spectrum spread signal falls within a predetermined frequency band, that is, within the range of 10 to 450 kHz. If the cosine roll-off with a roll-off rate of 0.5 is used, the clock frequency is 450k.
Hz × (2/3) = 300 kHz.

The number of data symbols generated by the test data generator 2 per unit time is inversely proportional to the length of the sequence generated by the spreading sequence generator 3, and the length of the sequence generated by the spreading sequence generator 3 is one cycle. One symbol of data is generated by the clock signal. Therefore, when an M sequence of length 7 is generated with a clock frequency of 300 kHz, the clock of the data symbol is 300 kHz / 7 = 42.8.
When the frequency is 571 kHz and an M sequence of length 1023 is generated, the data symbol clock is 300 kHz.
z / 1023 = 0.2933 kHz. When the clock of the feedback shift register is set to 300 kHz, the cycle is 7
The transmission rates corresponding to 1023 are as shown in Table 1 below.

[0011]

[Table 1]

The output of the test data generator 2 is multiplied by the output of the spreading sequence generator 3 by the multiplier 5 to spread the spectrum. The outputs of the test data generator 2 and the spreading sequence generator 3 are both binary, and the binary multiplication is performed by an exclusive OR circuit or a double balanced modulator (Doub).
le Balanced Mixer).
Since the spectrum-spread data signal has a frequency different from that of the commercial power source, the data signal is superimposed and transmitted to the electric power line 40 via the line coupler 7 having the characteristics of a high-pass filter, but the coupling involves a DC cutoff by a capacitor or a transformer. Therefore, the data signal is in a form that does not include a DC component. One of the characteristics of the pseudo-noise sequence such as the M sequence is balance, and when the binary value is represented by +1, -1, the total number of +1 is one more than the total number of -1, but the average value is zero. Close to. For complete equilibration, an extra -1 can be added to make the DC component zero.

Further, the test data series has a length of 5
An 11-bit M series is generally used, but if this series is used, this series has almost no DC component, so
It can be said that there is almost no DC component in the spread spectrum data series. Therefore, it is possible to send this series to the power line 40 via the line coupler 7 that does not pass the direct current component. Further, the phase or frequency of the carrier wave is modulated by the output of the test data generator 2 as in the case where the output of the test data generator 2 is converted into a Manchester encoded code sequence, or as in the fourth embodiment of FIG. 4 described later. In the case of the above-mentioned PSK or FSK signal, there is no direct current component, so that the signal obtained by further spreading this modulated wave by the spreading sequence also has no direct current component.

Next, the receiving section 30 will be described. The receiving unit 30 receives the test data from the power line 40, performs the reverse processing of the transmitting unit 20 and compares the test data with the transmitted data, and detects an error. A high-frequency component is extracted by the line coupler 9 connected to the power line 40, and the spectrum-spread data series signal is despread by the multiplier 12 to restore the data series. For the despreading process, the spreading sequence from the despreading sequence generator 13 synchronized with the synchronization signal given from the control circuit 1 on the transmission side is used, and the received spread spectrum data sequence is multiplied to perform the correlation operation, and the correlator output To restore the original data signal. The multiplier 12 in this case is
Since the input is an analog signal, a double balanced modulator having a function of multiplying an analog signal and a binary signal is used.

The restored data signal should match the transmitted data, but if the line quality of the transmission line is poor, the transmitted signal is distorted by being transmitted through the power line 40, and as a result, it is restored. A symbol error occurs in which the symbols of the generated data do not match the symbols of the transmitted data. The comparison / calculation circuit 15 compares the transmission data with the reception data, determines an error when they do not match, and calculates an error rate. A delay circuit and a logical coincidence circuit are used for aligning the time relationship between transmission data and reception data. The received data is received by transmitting the transmitted data through the power line 40.
Moreover, since the data is restored by performing the despreading process, a transmission delay and a despreading process time delay occur. Therefore, in order to compare the transmission data and the reception data, it is necessary to delay the transmission data by a time corresponding to this delay time.
The data to be compared here is binary data, and a data mismatch, that is, an error can be detected by using a matching circuit or an exclusive OR circuit. The error decreases as the spreading factor increases and the signal-to-noise ratio is improved by the spreading gain, but if the transmission bandwidth is limited, the data rate increases inversely with the spreading factor. Decrease.

FIG. 2 is a block diagram of the second embodiment of the present invention. The difference from the first embodiment shown in FIG. 1 described above is that the synchronization signal generator 8 and the coupling circuit 6 of the transmission unit 21 and the branch circuit 10 of the reception unit 31 and the synchronization signal detector 11 and the comparison data generator are provided. 16 is added. In the first embodiment, in addition to the power line 40 as a signal transmission line, transmission data to be compared by the comparison calculation circuit 15 and a synchronization signal required for the despreading sequence generator 13 are supplied by dedicated lines. There is. This can be applied when the transmitter 20 and the receiver 30 are arranged close to each other, but if the transmitter 20 and the receiver 30 are far from each other, it becomes difficult to wire the dedicated line. The second embodiment is useful in such a case.

FIG. 3 is a block diagram showing a third embodiment of the present invention. In the above-described first and second embodiments, the transmission error rate is obtained by the comparison calculation circuit 15 and used as the measurement data. However, when the present invention is applied to an actual communication device, the measurement result is a spread sequence. In the third embodiment, the long control signal is fed back to the transmitting side.

In the third embodiment, when the line quality deteriorates and the data transmission quality is poor, the spreading factor is gradually increased to reduce the error due to the spreading gain so that the error rate becomes equal to or lower than the reference value. It controls the transmission speed. ^If an M sequence having a period of 2 ⁿ −1 is used as the spreading sequence, n = 3 to 10 can be changed in the above example. This series can be generated by switching the feedback points of the 10-stage feedback shift register. A signal from the control circuit 1 switches the spreading cycle from a short one to a long one in sequence, and if the error rate is below a reference value in a spreading sequence with a short cycle, communication is continued at that transmission rate, and the error rate becomes the reference value. When it exceeds the value, data communication is performed by sequentially expanding the cycle (sequence length) until the error rate becomes equal to or lower than the reference value.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention. In the fourth embodiment, the modulator 4 is inserted in the transmitter of the second embodiment shown in FIG. 2 and the demodulator 1 is installed in the receiver.
4 is inserted. The transmitter 23 of the fourth embodiment of FIG. 4 modulates the phase or frequency of the carrier wave with the output of the test data generator 2 by the modulator 4 to generate a PSK signal or an FSK signal, and then inputs it to the multiplier 5. It is configured to do. Further, the receiving unit 33 is configured to demodulate the output of the multiplier 12 by the demodulator 14 to extract the symbols of the received data and input them to the comparison calculation circuit 15.

[0020]

As described in detail above, by carrying out the present invention, it is possible to put the data communication of the spread spectrum communication system by the power line into practical use. Further, the spread spectrum rate is variable, and stable communication can be performed at the highest data transmission rate corresponding to the change in the line quality of the transmission line. In addition, the system can be configured with only simple digital elements without using analog elements. Since this measurement transmits signals in all the bands that can be transmitted, the line quality of all bands can be measured in a short time.
The practical effect is extremely large.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

FIG. 3 is a system diagram showing a third embodiment of the present invention.

FIG. 4 is a system diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Control Circuit 2 Test Data Generator 3 Spreading Sequence Generator 4 Modulator 5 Multiplier 6 Coupling Circuit 7,9 Line Combiner 8 Sync Signal Generator 10 Branch Circuit 11 Sync Signal Detector 12 Multiplier 13 Despreading Sequence Generator 14 Demodulator 15 Comparison calculation circuit 16 Comparison data generator 20, 21, 22, 23 Transmitter 30, 31, 32, 33 Receiver 40 Power line

Claims (4)

[Claims] 1. A transmitter for transmitting a spectrum-spread digital test signal to a low-voltage distribution line in order to measure the line quality of the transmission line when performing data communication by a spread-spectrum system using the low-voltage distribution line as a transmission line. A receiving unit that receives the test signal from the transmitting unit via the low-voltage distribution line, the transmitting unit generating a test data sequence and outputting the number of symbols, and a test data generator, A spreading sequence generator that generates a code sequence of a plurality of bits for each symbol of the test data sequence and outputs a spreading code that can arbitrarily change the length of the code sequence, and the test data sequence by the spreading code. A spread spectrum first multiplier, and a first line for sending the spread spectrum data sequence from the first multiplier to the low voltage distribution line as the test signal. A combiner, a control circuit that gives a synchronization signal to the test data generator and the spread sequence generator, and the receiving unit includes a second line combiner for taking in the test signal from the low-voltage distribution line. A despreading sequence generator that outputs a spreading code equal to the spreading code of the first spreading sequence generator in synchronization with a synchronization signal from the control circuit, and a test signal output from the second line combiner. A second multiplier for despreading the received data by despreading with a spreading code from the despreading sequence generator to output symbols, and symbols of the received data from the second multiplier and the test data generator. And a comparison calculation circuit for calculating and outputting an error rate by comparing with the symbol from. 2. A synchronization signal generator for generating the synchronization signal is provided in the transmission unit according to claim 1, and the first multiplier is provided by a coupling circuit provided between the first multiplier and the line coupler. The synchronization signal from the synchronization signal generator is added to the output from the multiplier, the synchronization signal detector and the comparison data generator are provided in the receiving unit according to claim 1, and the second line coupler and the second line coupler are provided. The signal branched by the branch circuit provided between the multiplier and the multiplier is input to the synchronizing signal detector to detect the synchronizing signal, which is given to the despreading sequence generator and the comparison data generator to generate the comparison data. 2. The line quality measuring instrument according to claim 1, wherein the line quality measuring instrument is configured to supply test data equal to the test data generator to the comparison calculation circuit. 3. The error rate obtained from the comparison calculation circuit according to claim 2 is given to the control circuit as a spreading sequence length control signal for changing the length of the spreading sequence, and the error rate exceeds a standard value. 3. The line quality measuring instrument according to claim 2, wherein the length of the code sequence generated by the spreading sequence generator is extended until the error rate becomes equal to or less than a standard value. 4. The transmitter according to claim 2, further comprising a modulator that modulates the phase or frequency of a carrier wave by the output of the test data generator and then inputs the modulated data as test data to the first multiplier. 3. The line quality according to claim 2, wherein the receiving unit according to claim 1 further comprises a demodulator for demodulating an output of the second multiplier to extract a symbol of received data and input to the comparison calculation circuit. Measuring instrument.