JP4389741B2 - Power line communication device - Google Patents

Description

  The present invention relates to a power line communication apparatus that transmits and receives a signal obtained by assigning data to each of a plurality of carrier waves having different frequencies and modulating the carrier wave via a power line.

  In recent years, optical fibers have been laid near urban distribution transformers in urban areas, and high-speed power line communication between this optical fiber and tens to hundreds of meters from the distribution transformer to each customer ( By realizing PLC (Power Line Communication), high-speed data communication can be expected without newly laying a communication line.

  For power line communication, modulation schemes such as Orthogonal Frequency Domain Multiplex (OFDM) and Spread Spectrum (SS) are adopted, and communication on power lines with inferior communication characteristics is realized.

  However, the power line is branched and installed at many locations to distribute power to each customer, and the types of power cables used are diverse. Therefore, the impedance characteristics and attenuation of the power line with respect to frequency depend on the installation situation. The characteristics are greatly different, and even when the output of the signal to be transmitted is kept constant, the input power of the signal to be received varies depending on the frequency. In addition, many power devices or electronic devices are connected to the power line, and various levels of noise are generated in the power line according to changes in the type, number of connections, load status, etc. of these devices. To change. Therefore, data communication may not be performed depending on the frequency or time.

Therefore, in order to prevent the occurrence of data transmission errors due to noise generated in the power line and the problem of communication quality degradation or communication inability to occur, the signal-to-noise ratio is estimated for each carrier, and the estimated signal-to-noise ratio There has been proposed a power line communication device that optimizes the amount of data allocated to modulation of a carrier according to the level, and improves the quality of communication and waste of transmission power by not using a carrier that cannot be used for communication. (See Patent Document 1).
JP 2002-319919 A

  However, in the example of Patent Document 1, the signal-to-noise ratio of a signal received for each carrier is estimated, and the carrier determined to be usable for communication has a small amount of data allocated to the carrier. However, data is allocated to the carrier according to the estimated signal-to-noise ratio. The use of the carrier wave may affect other carrier frequency bands due to intermodulation, etc., and the signal-to-noise ratio of the signal in the other carrier deteriorates, and the amount of data allocated to the other carrier is small. On the contrary, the communication speed as a whole may decrease.

  The present invention has been made in view of such circumstances, and compares the received power of a signal received on one carrier with a predetermined threshold value, and assigns data to the one carrier based on the comparison result. In this case, when data is allocated to the one carrier and when data allocation is stopped, the communication speed is controlled as a whole by controlling the data allocation to the one carrier by comparing the respective communication speeds. An object of the present invention is to provide a power line communication device that can be improved.

  Another object of the present invention is caused by the one carrier by providing threshold setting means for setting the threshold based on the received power of the signal received by each of the other carriers except the one carrier. Even when noise affects the signal-to-noise ratio in the other carrier wave, the power line communication apparatus can control the allocation of data to the one carrier wave and improve the communication speed as a whole Is to provide.

  Another object of the present invention is that each of the other carriers has a frequency close to the frequency of the one carrier, so that noise generated by the one carrier is a carrier having a frequency close to the frequency. Even when the signal-to-noise ratio is affected, it is desirable to provide a power line communication apparatus capable of controlling the allocation of data to the one carrier and improving the communication speed as a whole.

  Another object of the present invention is that each of the other carrier waves is all the carrier waves except the one carrier wave, so that the noise generated by the one carrier wave is any carrier wave in the communication frequency band. Even when the signal-to-noise ratio is affected, it is desirable to provide a power line communication apparatus capable of controlling the allocation of data to the one carrier and improving the communication speed as a whole.

  Another object of the present invention is to control the allocation of data to a carrier wave according to the level of noise generated by the carrier wave by using a signal-to-noise ratio instead of the received power in the above-described invention, An object of the present invention is to provide a power line communication device capable of improving the communication speed as a whole.

  The power line communication apparatus according to the first aspect of the present invention is configured to transmit and receive a signal obtained by allocating data consisting of a bit string for each of a plurality of carriers having different frequencies and modulating the carrier via the power line, and receiving power of the signal received for each carrier And a communication speed calculating means for calculating a data communication speed based on the number of bits allocated to each carrier, and a single carrier Receiving power comparing means for comparing the received power of the signal received in step 1 with a predetermined threshold, and control means for controlling stop of data allocation to the one carrier based on the result of comparison by the received power comparing means And the communication speed calculated by the communication speed calculation means for each of the case where the assignment of data to the one carrier is not stopped and the case where the assignment is stopped. Communication speed comparison means for comparing, and based on the result of comparison by the communication speed comparison means, the control means is configured to control the stop of data allocation to the one carrier wave. And

  A power line communication apparatus according to a second invention is characterized in that, in the first invention, the power line communication device further comprises threshold setting means for setting the threshold based on received power of a signal received on each of the other carriers other than the one carrier. To do.

  The power line communication apparatus according to a third aspect of the present invention is characterized in that, in the second aspect, each of the other carrier waves has a frequency close to the frequency of the one carrier wave.

  The power line communication apparatus according to a fourth aspect of the present invention is characterized in that, in the second aspect, each of the other carrier waves is all the carrier waves except the one carrier wave.

  A power line communication apparatus according to a fifth aspect of the present invention includes a signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio from the received power according to any one of the first to fourth aspects of the invention. The signal-to-noise ratio calculated by the signal-to-noise ratio calculating means is used.

  In the first invention, the communication speed calculation means calculates the data communication speed based on the number of bits assigned to each carrier wave. The received power comparing means compares the received power of the signal received with one carrier wave with a predetermined threshold value. As a result of comparison, if the received power is greater than a threshold value, the control means assigns data to the one carrier wave, and the communication speed calculation means assigns data communication speed when the data is assigned to the one carrier wave. Is calculated. The control means further stops data assignment to the one carrier wave, and the communication speed calculation means calculates a data communication speed when assignment of data to the one carrier wave is stopped. The communication speed comparison means compares the communication speed calculated by the communication speed calculation means when the data is allocated to the one carrier and the communication speed when the allocation is stopped, and sends the data to the one carrier. When the communication speed when assigned is lower, the signal to noise ratio of the other carrier is reduced by noise such as intermodulation caused by the one carrier, so that the control means is the one carrier. Stop assigning data to.

  The communication speed when data is allocated to the one carrier wave is compared with the communication speed when the allocation is stopped, and when the communication speed when data is allocated to the one carrier wave is larger, The control means allocates data to the one carrier wave. Further, as a result of comparing the received power of the signal received on the one carrier wave with a predetermined threshold value, if the received power is smaller than the threshold value, the control means stops assigning data to the one carrier wave. To do.

  In the second invention, the threshold setting means sets the threshold based on the received power of the signal received on each of the other carriers other than one carrier. When the noise generated by the one carrier wave lowers the signal-to-noise ratio of the other carrier wave, the threshold value setting means sets a smaller threshold value. When the influence of noise by the one carrier is small and the signal-to-noise ratio of the other carrier is not lowered, the threshold setting means sets a larger threshold.

  In the third invention, the threshold setting means sets the threshold based on the received power of the signal received by each carrier having a frequency close to the frequency of one carrier. When the signal-to-noise ratio of a carrier having a frequency close to the frequency of the one carrier is reduced by noise such as intermodulation caused by the one carrier, the threshold setting means sets a smaller threshold. To do. When the signal-to-noise ratio in a carrier having a frequency close to the frequency of the one carrier is reduced by comparing the received power of the signal received on the one carrier and the threshold, the one carrier Controls the allocation of data to

  In the fourth invention, the threshold value setting means sets the threshold value based on the received power of the signals received on all the carrier waves except for one carrier wave. When the noise generated by the one carrier reduces the signal-to-noise ratio in any of all the carriers except the one carrier, the threshold setting unit sets a smaller threshold. By comparing the received power of the signal received on the one carrier with the threshold value, if the signal-to-noise ratio is reduced in any one of the carriers other than the one carrier, the signal is transferred to the one carrier. Control the allocation of data.

  In the fifth invention, a signal-to-noise ratio is used instead of the received power in the first to fourth inventions. Thereby, the threshold setting means sets the threshold based on the ratio of the signal level to the level of noise generated in the frequency band of the carrier wave.

  In the first invention, when data is allocated to one carrier wave, the communication speed when the data is allocated to the one carrier wave is compared with the communication speed when the allocation is stopped, and the comparison result is obtained. Based on this, it is possible to improve the communication speed as a whole by controlling the allocation of data to the one carrier wave.

  In the second invention, a threshold can be set according to a decrease in the signal-to-noise ratio in other carriers other than the one carrier, and according to the influence on the signal-to-noise ratio of the other carrier By controlling the allocation of data to the one carrier wave, the overall communication speed can be improved.

  In the third aspect of the invention, when the noise generated by one carrier affects the decrease in the signal-to-noise ratio in a carrier having a frequency close to the frequency of the one carrier, By controlling the allocation of data to the carrier wave, the overall communication speed can be improved.

  According to the fourth aspect of the present invention, when noise generated by one carrier wave affects the decrease in the signal-to-noise ratio of the carrier wave in the communication frequency band, the data is assigned to the one carrier wave. By controlling, the communication speed can be improved as a whole.

  In the fifth aspect of the invention, by controlling the allocation of data to the one carrier based on the signal-to-noise ratio of the signal received on the one carrier, according to the noise level generated in the frequency band of the carrier The assignment of data to the one carrier can be controlled.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is an explanatory diagram showing an outline of power line conveyance. In the figure, reference numeral 1 denotes an intermediate voltage distribution line laid through a utility pole. The medium voltage distribution line 1 distributes a medium voltage (for example, 6 kV) of a three-phase alternating current. The intermediate voltage distribution line 1 is connected to a transformer 5 attached to a power pole, and the transformer 5 converts the medium voltage supplied by the medium voltage distribution line 1 into a low voltage (for example, 200 V). The power line 2 is connected to the transformer 5, and the power line 2 supplies a low voltage to each consumer.

  The optical fiber 6 is connected to a communication network 8 such as the Internet, and a photoelectric conversion device 7 attached to a utility pole is connected to the optical fiber 6. The photoelectric conversion device 7 converts an optical signal transmitted through the optical fiber 6 into a digital electric signal. A modem 3 is connected to the photoelectric conversion device 7, and the modem 3 performs a predetermined process on the digital signal input from the photoelectric conversion device 7, and the processed signal is sent to each demand via the power line 2. Send to home modems 4, 4,. The personal computers 9a, 9a,... Are connected to the modems 4, 4,..., Perform predetermined processing on the signals received via the power line 2, and the processed data are stored in the personal computers 9a, 9a. Output to ... Moreover, the electric equipment 9b, 9b, ... of each consumer is connected to the power line 2.

  On the other hand, the personal computers 9a, 9a,... Output data for transmission to a server (not shown) of the communication network 8 to the modems 4, 4,. The modems 4, 4,... Perform predetermined processing on the data input from the personal computers 9 a, 9 a,... And transmit the processed signals to the modem 3 via the power line 2. The modem 3 performs predetermined processing on the signals received from the modems 4, 4,..., And outputs the processed digital signal to the photoelectric conversion device 7. The photoelectric conversion device 7 converts the digital electrical signal input from the modem 3 into an optical signal, and transmits the converted optical signal to the communication network 8 via the optical fiber 6.

  FIG. 2 is a block diagram showing the configuration of the modem 3. In the figure, 10 is an error correction code part. The error correction encoding unit 10 encodes data by adding an error correction code to data bits composed of a bit string input from the transmission side (photoelectric conversion device 7), and outputs the encoded data to the buffer 11.

  The buffer 11 temporarily stores the data input from the error correction coding unit 10 and outputs the data to the serial / parallel conversion unit 12 for each fixed number of bits.

  The serial / parallel converter 12 converts the serial data read from the buffer 11 into a set of parallel data equal to the number of subcarriers having different frequencies (number of subcarriers) used in the quadrature amplitude modulator 13 described later. The parallel data is output to the quadrature amplitude modulation unit 13. In addition, the serial / parallel converter 12 stops or starts the conversion process in accordance with an allocation stop signal or an allocation signal from the control unit 33 described later.

  FIG. 3 is an explanatory diagram showing a spectrum of a carrier wave. As shown in the figure, among the respective carriers (for example, the frequency interval of each carrier is 4.8 kHz) in the communication bandwidth (for example, 10 MHz) of the modem 3, adjacent carriers are orthogonal to each other.

  The quadrature amplitude modulation unit 13 distributes a plurality of sets of parallel data input from the serial / parallel conversion unit 12 to a plurality of orthogonal carrier waves, assigns the distributed data to each carrier wave, and assigns assigned data ( Based on the symbol), quadrature amplitude modulation (QAM) for modulating the amplitude and phase of the carrier wave is performed, and the modulated signal is output to the inverse Fourier transform unit 14.

  Further, the quadrature amplitude modulation unit 13 stops or starts the modulation process in accordance with an allocation stop signal or an allocation signal from the control unit 33 described later. Further, the quadrature amplitude modulation unit 13 performs a modulation process according to the number of bits allocated for each carrier according to the number of allocated bits input from the control unit 33.

  The inverse Fourier transform unit 14 converts the modulation signal for each carrier wave input from the quadrature amplitude modulation unit 13 into a modulation signal in the time domain, and outputs the converted modulation signal to the parallel / serial conversion unit 15.

  The parallel / serial conversion unit 15 converts the modulation signal input from the inverse Fourier transform unit 14 into serial data and outputs the serial data to the guard interval unit 16.

  The guard interval unit 16 takes into account the delay time of each carrier in order to prevent intersymbol interference due to multipath transmission using a plurality of carriers with respect to the serial data input from the parallel-serial converter 15. A process of inserting a guard interval for increasing the symbol length by the guard interval is performed, and the processed signal is output to the D / A converter 17.

  The D / A conversion unit 17 converts the digital modulation signal input from the guard interval unit 16 into an analog modulation signal and outputs the analog modulation signal to the filter 18.

  The filter 18 removes the harmonic component of the modulation signal input from the D / A converter 17 and sends the processed modulation signal to the power line 2.

  On the other hand, the filter 20 removes harmonic components from the modulated signal received via the power line 2 and outputs the processed signal to the A / D converter 21.

  The A / D conversion unit 21 converts the analog modulation signal input from the filter 20 into a digital signal, and outputs the converted signal to the guard interval unit 22.

  The guard interval unit 22 performs a process of removing the guard interval from the signal input from the A / D conversion unit 21, and outputs the processed signal to the serial / parallel conversion unit 23.

  The serial / parallel converter 23 converts the signal input from the guard interval unit 22 into a set of parallel data equal to the number of subcarriers, and outputs the converted parallel data to the Fourier transform unit 24.

  The Fourier transform unit 24 converts the signal input from the serial / parallel conversion unit 23 into a frequency domain signal for each carrier wave, and outputs the converted signal to the quadrature amplitude demodulation unit 25.

  The quadrature amplitude demodulation unit 25 performs demodulation processing for reproducing the transmitted data based on the signal input from the Fourier transform unit 24, and outputs the processed data to the parallel / serial conversion unit 26.

  The parallel / serial conversion unit 26 converts the demodulated data for each carrier wave into serial data, and outputs the converted data to the buffer 27.

  The buffer 27 temporarily stores the data input from the parallel / serial conversion unit 26 until the error correction decoding unit 28 reads the data.

  The error correction decoding unit 28 reads the data stored in the buffer 27, performs error correction when the read data has an error, outputs the corrected data to the reception side (photoelectric conversion device 7), and reads the data. If there is no error in the received data, the data is output to the receiving side.

  The signal-to-noise ratio calculation unit 30 samples the signal of one carrier wave input from the Fourier transform unit 24, and calculates the signal-to-noise ratio SNR based on the average value of all the sampled signal vectors. The same processing is performed on all other carrier signals, and the signal-to-noise ratio SNR for each carrier is calculated.

  FIG. 4 is an explanatory diagram showing the calculation principle of the signal-to-noise ratio SNR. The signal-to-noise ratio calculation unit 30 samples a plurality of signals from the signal input from the Fourier transform unit 24. The sampled signal is decomposed into an I (In phase) component and a Q (Quadrature) component to obtain signal vectors r1, r2,. An average value of each of the I component and Q component of the signal vectors of all the sampled signals is calculated, and this is defined as an average signal vector S. Further, let the difference between the average signal vector S and each signal vector r1, r2,... Be a noise vector n1, n2,. The standard deviation σ of the noise component is as shown by a broken-line circle in the figure. It is known that the square of the noise component standard deviation σ is the noise power N, and the signal-to-noise ratio SNR is calculated from the ratio of the average signal vector S and the noise power N.

  The signal-to-noise ratio calculation unit 30 outputs the signal-to-noise ratio SNR calculated for each carrier wave to the threshold setting unit 31 and the signal-to-noise ratio comparison unit 32.

Based on the signal-to-noise ratio SNR for all carriers input from the signal-to-noise ratio calculating unit 30, the threshold setting unit 31 has a frequency close to the frequency f _k of one carrier (for example, centering on the frequency f _k , Five frequencies f _k-5 , f _k-4 , f _k-3 , f _k-2 , f _k−1 , f _{k + 1} , f _{k + 2} , f _{k + 3} on the high frequency side and the low frequency side, respectively. , F _{k + 4} , f _{k + 5} ), the average value of the signal-to-noise ratio SNR in each carrier wave is calculated, and the calculated average value is compared with the signal-to-noise ratio SNR _k of the carrier wave of frequency f _k . Set as threshold TH _k . Similarly, the threshold setting unit 31 sets a threshold TH for comparison with each of the signal-to-noise ratios SNR in the carrier waves of all other frequencies. When the frequency of the carrier wave for calculating the signal-to-noise ratio SNR is the minimum or maximum frequency of the band frequency, the average is calculated from the signal-to-noise ratio SNR in the carrier of five adjacent frequencies on the high frequency side or the low frequency side. What is necessary is just to calculate a value.

The signal-to-noise ratio comparison unit 32 compares the signal-to-noise ratio SNR _k of the carrier wave having the frequency f _k input from the signal-to-noise ratio calculation unit 30 with the threshold value TH _k and outputs the comparison result to the control unit 33. . When the signal-to-noise ratio SNR _k is larger than the threshold value TH _k , the signal-to-noise ratio comparison unit 32 outputs an allocation confirmation signal to the control unit 33. When the signal-to-noise ratio SNR _k is smaller than the threshold value TH _k , the signal-to-noise ratio comparison unit 32 outputs an allocation stop signal to the control unit 33. The signal-to-noise ratio comparison unit 32 performs the same processing for a carrier wave having a frequency other than the frequency f _k .

  The signal-to-noise ratio comparison unit 32 outputs the signal-to-noise ratio SNR for each carrier wave input from the signal-to-noise ratio calculation unit 30 to the control unit 33.

  When the allocation confirmation signal is input from the signal-to-noise ratio comparison unit 32, the control unit 33 outputs an allocation stop signal to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13, and outputs a communication speed calculation request signal. The data is output to the communication speed calculation unit 34. Further, after outputting the allocation stop signal, the control unit 33 outputs the allocation signal to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13 after a time required for the communication rate calculation unit 34 described later to calculate the communication rate. In addition, a communication speed calculation request is output to the communication speed calculation unit 34.

  In addition, when an allocation stop signal is input from the signal-to-noise ratio comparison unit 32 or the communication speed comparison unit 35, the control unit 33 sends the allocation stop signal to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13. Output.

  In addition, when an allocation signal is input from the communication speed comparison unit 35, the control unit 33 outputs the allocation signal to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13.

  In addition, the control unit 33 outputs a preset number of assigned bits to the quadrature amplitude modulation unit 13 based on the signal-to-noise ratio SNR for each carrier wave input from the signal-to-noise ratio comparison unit 32.

  When the allocation stop signal and the allocation signal are input from the control unit 33, the communication speed calculation unit 34 counts the number of bits of data output from the parallel / serial conversion unit 15 during a predetermined time. The communication speed is calculated when data is allocated to the carrier wave and when it is not allocated, and the calculated communication speed result is output to the communication speed comparison unit 35.

  The communication speed comparison unit 35 compares the communication speeds input from the communication speed calculation unit 34, and the communication speed when data is assigned to one carrier wave is the communication speed when data is not assigned to the one carrier wave. If it is larger, the assignment signal is output to the control unit 33. Further, the communication speed comparison unit 35 sends an allocation stop signal to the control unit 33 when the communication speed when data is allocated to one carrier wave is lower than the communication speed when data is not allocated to the one carrier wave. Output.

  Since the modem 4 has the same configuration as the modem 3, the description thereof is omitted.

  Next, the operation of the modem 3 will be described. A signal received via the power line 2 is subjected to processing in the filter 20, the A / D conversion unit 21, the guard interval unit 22, the serial / parallel conversion unit 23, and the Fourier transform unit 24, and then a signal-to-noise ratio calculation unit. 30.

The signal-to-noise ratio calculation unit 30 calculates the signal-to-noise ratio SNR for the carrier waves of all frequencies including the frequency f _k within the communication band, and uses the calculated signal-to-noise ratio SNR as the threshold setting unit 31 and the signal pair. Output to the noise ratio comparator 32.

The threshold value setting unit 31 selects a frequency close to the frequency f _k from the signal-to-noise ratio SNR of each carrier wave input from the signal-to-noise ratio calculation unit 30 (for example, with the frequency f _k as the center, Each of the five frequencies f _k-5 , f _k-4 , f _k-3 , f _k-2 , f _k-1 , f _{k + 1} , f _{k + 2} , f _{k + 3} , f _{k + 4} and f _{k + 5} ), the average value of the signal-to-noise ratio SNR in each carrier wave is calculated, and the calculated average value is used as the threshold value TH _k when compared with the signal-to-noise ratio SNR _k of the carrier wave of frequency f _k. Set.

Accordingly, reflecting the influence of by the noise of the intermodulation like caused by the carrier frequency f _k to the signal-to-noise ratio SNR of the carrier signal of the other adjacent frequency to the threshold TH _k. That is, when the influence of noise is large and the signal-to-noise ratio SNR is small, the threshold TH _k is small, and when the influence of noise is small and the signal-to-noise ratio SNR is large, the threshold TH _k is large. Become.

  FIG. 5 is an explanatory diagram showing an example of intermodulation. For example, when a signal having two different frequencies f1 and f2 is input in the frequency band of one carrier wave, between the input signals and harmonics generated by non-linearity such as a high-frequency amplifier in the modem 3 Intermodulation occurs, and an unnecessary frequency component (broken line portion in the figure) determined by fs = (m + 1) f1-mf2 or fs = (m + 1) f2-mf1 is generated, which affects the carrier signal of other frequencies. May give. Here, m is a natural number.

As a result, when noise is generated in a frequency band adjacent to the carrier wave having the frequency f _k , noise is generated in the same frequency as the signal of each carrier wave having a frequency close to the frequency f _k . When the signal-to-noise ratio SNR decreases, the threshold value TH _k becomes smaller, and the signal-to-noise ratio SNR _k of the carrier wave having the frequency f _k is more likely to be larger than the threshold value TH _k , and the frequency f _k is increased. The possibility of confirming whether or not to allocate data to a certain carrier wave is increased.

The signal-to-noise ratio comparison unit 32 compares the signal-to-noise ratio SNR _k of the carrier wave signal having the frequency f _k input from the signal-to-noise ratio calculation unit 30 with the threshold value TH _k read from the threshold setting unit 31. If the signal-to-noise ratio SNR _k is larger than the threshold value TH _k as a result of the comparison, the signal-to-noise ratio comparison unit 32 outputs an allocation confirmation signal to the control unit 33.

  The signal-to-noise ratio comparison unit 32 outputs the signal-to-noise ratio SNR for each carrier wave input from the signal-to-noise ratio calculation unit 30 to the control unit 33.

  The control unit 33 outputs a preset number of assigned bits to the quadrature amplitude modulation unit 13 based on the signal-to-noise ratio SNR for each carrier wave input from the signal-to-noise ratio comparison unit 32.

  FIG. 6 is an explanatory diagram showing the relationship of the number of allocated bits to the signal-to-noise ratio SNR. As shown in the figure, as the signal-to-noise ratio SNR of the received signal in each carrier increases, the number of bits allocated to the carrier is increased. Further, when the signal-to-noise ratio SNR is reduced due to the influence of noise, the number of bits allocated to the carrier is reduced. This reduces data transmission errors and improves communication quality.

When the allocation confirmation signal is input from the signal-to-noise ratio comparison unit 32, the control unit 33 outputs an allocation stop signal for the carrier wave having the frequency f _k to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13. A communication speed calculation request signal is output to the communication speed calculation unit 34. Further, the control unit 33 outputs the allocation stop signal, and after the time required for the communication speed calculation unit 34 to calculate the communication speed has elapsed, the control unit 33 converts the allocation signal for the carrier wave having the frequency f _k to the serial / parallel conversion unit 12 and the quadrature amplitude modulation. In addition to outputting to the unit 13, a communication speed calculation request is output to the communication speed calculation unit 34.

The communication speed calculation unit 34 is a bit of data output from the parallel / serial conversion unit 15 during a predetermined time when the allocation stop signal and the allocation signal for the carrier wave having the frequency f _k are input from the control unit 33. The communication speed is calculated when the number is counted and data is assigned to the carrier wave of frequency f _k and when the data is not assigned, and the calculated communication speed result is output to the communication speed comparison unit 35.

Communication speed comparison unit 35 compares the people communication speed respectively input from the communication speed calculating unit 34, if the communication speed in the case of assigning the data to the carrier frequency f _k does not allocate data to the carrier frequency f _k If the communication speed is greater than the transmission speed, an allocation signal for the carrier wave having the frequency f _k is output to the control unit 33. Further, the communication speed comparison unit 35, if the communication speed in the case of assigning the data to the carrier frequency f _k is smaller than the communication speed in the case of the data non-allocation to the carrier of the frequency f _k is the carrier frequency f _k An allocation stop signal is output to the control unit 33.

FIG. 7 is an explanatory diagram showing an example of communication speed comparison. As shown, when the allocated data to the carrier frequency f _k, the communication speed of the carrier wave of the frequency f _k is "4", the frequency _{f k-5, f k-} 4, f k-3, f The communication speeds of the carriers _k-2 , _fk-1 , _{fk + 1} , _{fk + 2} , _{fk + 3, fk + 4} , _{fk + 5} are "10", "10", “10”, “10”, “7”, “6”, “9”, “10”, “10”, “10”, and the total communication speed is “96”.

On the other hand, if the data non-allocation to the carrier of the frequency f _k, the communication speed is "0" in carrier frequency f _k, the frequency _{f k-5, f k-} 4, f k-3, f k-2, f _k−1 , f _{k + 1} , f _{k + 2} , f _{k + 3} , f _{k + 4} , f _{k + 5} , the communication speed on each carrier, “10”, “10”, “10”, “ 10 ”,“ 10 ”,“ 10 ”,“ 10 ”,“ 10 ”,“ 10 ”,“ 10 ”, and the total communication speed is“ 100 ”.

If allocated data to the carrier frequency f _k, the noise of the intermodulation etc. caused by the carrier frequency f _k is reduces the carrier signal-to-noise ratio of the other frequencies, the number of allocated bits is decreased. Further, when data is not assigned to the carrier wave of frequency f _k, the carrier wave is not used, so noise generated by the carrier wave of frequency f _k is eliminated, and the signal-to-noise ratio SNR of the signal in the carrier wave of other frequency is increased. As a result, the number of allocated bits increases, and the overall communication speed is improved.

On the other hand, the signal-to-noise ratio comparison unit 32 compares the signal-to-noise ratio SNR _k of the carrier wave signal having the frequency f _k input from the signal-to-noise ratio calculation unit 30 with the threshold value TH _k read from the threshold setting unit 31. As a result, when the signal-to-noise ratio SNR _k is smaller than the threshold value TH _k , the signal-to-noise ratio comparison unit 32 outputs the assigned signal to the control unit 33.

  When the allocation signal is input from the communication speed comparison unit 35, the control unit 33 outputs the allocation signal to the serial / parallel conversion unit 12 and the quadrature amplitude modulation unit 13.

When the above-described processing is completed for the carrier wave of frequency f _k , the modem 3 performs the same processing for the carrier waves of other frequencies. As a result, the best communication speed can be obtained for all the carriers in the communication band of the modem 3.

  As described above, in the present embodiment, the signal-to-noise ratio SNR of the signal received on one carrier is compared with the threshold value TH that reflects the influence of noise generated on the one carrier. When the noise-to-noise ratio SNR is larger than the threshold value TH, the communication speed is calculated for the case where data is assigned to the one carrier and the case where the data is not assigned, and the calculated communication speed is compared. It is possible to improve communication speed as a whole by controlling whether or not data is allocated.

In the above-described embodiment, the threshold setting unit 31 calculates an average value of the signal-to-noise ratio SNR of a signal in a carrier having a frequency close to one frequency f _k, and uses the calculated average value of the frequency f _k . The threshold value TH _k is set for comparison with the signal-to-noise ratio SNR _{k of the} carrier wave. However, the present invention is not limited to this. For example, instead of a carrier having a close frequency, a threshold TH _k may be set by calculating an average value of the signal-to-noise ratio SNR of signals in all carriers in the communication band. Thereby, it is possible to reflect the influence of noise generated in the communication band.

In the above-described embodiment, the threshold setting unit 31 is configured to calculate the average value of the signal-to-noise ratio SNR of the signals in the ten carriers at the frequency close to the one frequency f _k. The number of carrier waves to be calculated is not limited to this.

  In the above-described embodiment, the average value of the signal-to-noise ratio SNR of the signal in the carrier wave is calculated. However, the present invention is not limited to this. For example, a configuration may be used in which ½ of the sum of the maximum value and the minimum value of the signal-to-noise ratio SNR is calculated.

  In the above-described embodiment, the signal-to-noise ratio SNR of the signal in the carrier wave is used. However, the present invention is not limited to this, and the signal level may be used instead of the signal-to-noise ratio SNR.

  In the above-described embodiment, the configuration uses quadrature amplitude modulation, but the present invention is not limited to this. For example, a configuration using phase modulation (PSK: Phase Shift Keying), amplitude modulation (ASK: Amplitude Shift Keying), or the like may be used.

  In the above-described embodiment, when the signal-to-noise ratio SNR of the carrier wave signal of one frequency is larger than the threshold value TH, the signal-to-noise ratio comparison unit 32 outputs the allocation confirmation signal to the control unit 33. However, the present invention is not limited to this, and when the signal-to-noise ratio SNR of the carrier signal of one frequency is smaller than the threshold value TH, the signal-to-noise ratio comparison unit 32 sends the allocation confirmation signal to the control unit 33. It may be configured to output to.

  In the above-described embodiment, the communication speed is calculated and the calculated communication speed is compared. However, the present invention is not limited to this, and communication quality such as a bit transmission error rate is calculated instead of the communication speed. May be configured to compare.

It is explanatory drawing which shows the outline | summary of electric power line conveyance. It is a block diagram which shows the structure of a modem. It is explanatory drawing which shows the spectrum of a carrier wave. It is explanatory drawing which shows the calculation principle of a signal to noise ratio. It is explanatory drawing which shows the example of intermodulation. It is explanatory drawing which shows the relationship of the number of allocation bits with respect to a signal-to-noise ratio. It is explanatory drawing which shows the example of communication speed comparison.

Explanation of symbols

2 Power line 3, 4 Modem
DESCRIPTION OF SYMBOLS 12 Serial / parallel conversion part 13 Quadrature amplitude modulation part 15 Parallel / serial conversion part 24 Fourier transform part 30 Signal to noise ratio calculation part 31 Threshold setting part 32 Signal to noise ratio comparison part 33 Control part 34 Communication speed calculation part 35 Communication speed Comparison part

Claims (5)

Data consisting of bit strings is assigned to each of a plurality of carriers having different frequencies, and a signal obtained by modulating the carrier is transmitted / received via a power line, and assigned to the modulation of the carrier according to the received power of the signal received for each carrier. In the power line communication device that sets the number of bits of data,
A communication speed calculating means for calculating a data communication speed based on the number of bits allocated to each carrier;
Received power comparison means for comparing the received power of a signal received on one carrier with a predetermined threshold;
Control means for controlling stop of allocation of data to the one carrier wave based on the result of comparison by the received power comparing means;
A communication speed comparison means for comparing the communication speed calculated by the communication speed calculation means in each of the cases where the assignment of data to the one carrier is not stopped and the assignment is stopped,
The power line communication apparatus according to claim 1, wherein the control unit is configured to control stop of data allocation to the one carrier wave based on a result of comparison by the communication speed comparison unit.   The power line communication apparatus according to claim 1, further comprising a threshold setting unit configured to set the threshold based on reception power of a signal received by each of the other carriers other than the one carrier.   The power line communication device according to claim 2, wherein each of the other carrier waves has a frequency close to a frequency of the one carrier wave.   The power line communication apparatus according to claim 2, wherein each of the other carrier waves is all the carrier waves except the one carrier wave.   A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio from the received power is provided, and the signal-to-noise ratio calculated by the signal-to-noise ratio calculating unit is used instead of the received power. The power line communication apparatus according to any one of claims 1 to 4.

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