JP5156920B2 - Power line carrier communication equipment - Google Patents

Description

  The present invention relates to a power line carrier communication apparatus, and more particularly to a power line carrier communication apparatus that performs communication using a low frequency band.

  In recent years, attention has been paid to power line communication (PLC) that performs communication by superimposing a high-frequency current of 10 kHz or more on a power line. Previously, only the frequency band of 10 kHz to 450 kHz was recognized as the frequency band for power line carrier communications. However, due to the amendment of radio wave law in October 2006, a higher band of 2 MHz to 30 MHz may be used although it is limited to indoors. Admitted. Accompanying this, high speed communication of several tens to several hundreds Mbps has become possible, and thus attention is particularly focused on use in homes and offices.

  In reality, however, there are many outdoor applications for using power line carrier communications. For example, there are an example used for meter reading (data collection) of an electric meter and an example used for control from a remote place. In such applications, a band of 10 kHz to 450 kHz (hereinafter referred to as a low frequency band) is used as usual.

  Here, the legal system in the power line carrier communication apparatus using the low frequency band will be briefly described.

  In the Radio Law, power line carrier communication devices that use a low frequency band are classified as high-frequency equipment, and the Radio Law Enforcement Regulations stipulate a type system that allows high-frequency equipment to be used without a license. Among them, the category that can be used for general purposes is “special carrier type digital transmission device”, and specific conditions for specifying the type are specified as shown in Table 1 for each modulation method (see Article 46 of the Regulations). (2) No. 4. (Excerpt from some conditions.)

  As a modulation method used in this low frequency band, in the following description, an OFDM (Orthogonal Frequency Division Multiplexing) modulation method as a “modulation method other than the spread spectrum method” using 10 k to 450 kHz, , 115 kHz or 132 kHz phase modulation system (including phase amplitude modulation system). Hereinafter, unless otherwise specified, the OFDM modulation scheme refers to the former, and the phase modulation scheme refers to the latter. Note that Patent Documents 1 to 3 disclose examples of power line carrier communication apparatuses using the OFDM modulation method.

  The OFDM modulation method has the advantage that relatively high-speed and highly reliable communication can be realized because the band of 10 k to 450 kHz is fully used and adaptive modulation for each subcarrier can be performed. On the other hand, the current radio wave law enforcement regulations limit the total output value of all subcarriers to 100 mW or less, which is disadvantageous for communication in a noisy environment or communication with a distant place.

  The phase modulation method can perform only low-speed communication as compared with the OFDM modulation method, but can output 350 mW, and thus is effective for communication in a noisy environment and communication with a distant place.

In this specification, the OFDM modulation method and the phase modulation method are collectively referred to as modulation methods. The modulation scheme here refers to the entire series of secondary modulation including primary modulation and inverse Fourier transform for each subcarrier in the OFDM modulation scheme, and refers to phase modulation of a carrier signal having a specific frequency in the phase modulation scheme.
JP 2002-280939 A JP 2002-344417 A JP 2008-98812 A

  By the way, in applications such as those described above that require the use of a low frequency band even after the revision of radio wave laws and regulations, it is important to be able to reliably deliver data far away, while general high-speed and large-capacity data communication is also required. .

  However, in the conventional power line carrier communication using the low frequency band, it is not possible to realize both the reliable delivery of data to a long distance and the high-speed and large-capacity data communication. That is, as described above, the OFDM modulation method is suitable for high-speed and large-capacity data communication, but is not suitable for reliably delivering data to a distant place. In addition, the phase modulation method is suitable for the purpose of reliably delivering data to a long distance, but cannot cope with high-speed and large-capacity data communication.

  Accordingly, one of the objects of the present invention is to provide a power line carrier communication device that can achieve both high-speed and large-capacity data communication while reliably delivering data to a long distance using a low frequency band.

  In order to achieve the above object, a power line carrier communication apparatus according to the present invention transmits broadcast transmission data multiple times while selectively changing a modulation method used for modulating a carrier signal from a plurality of modulation methods. Based on the reception result of the response signal transmitted from another power line carrier communication device for the plurality of times of transmission, one of the plurality of modulation methods is changed to the optimum modulation method of the other power line carrier communication device. When transmitting transmission data to the other power line carrier communication apparatus, the carrier signal is modulated using the optimum modulation method.

  According to the present invention, since it becomes possible to communicate with another power line carrier communication device using an optimal modulation method, in a power line carrier communication device using a low frequency band, data can be reliably delivered to a distant place. High-speed and large-capacity data communication can be achieved.

  In the power line carrier communication apparatus, the plurality of modulation schemes include an OFDM modulation scheme and a phase modulation scheme, and when a response signal is received when the OFDM modulation scheme is used for modulating the carrier signal. The OFDM modulation scheme is selected as the optimum modulation scheme of the other power line carrier communication apparatus, and when the OFDM modulation scheme is used for modulating the carrier signal, a response signal is not received, and the carrier signal is modulated by the modulation When a response signal is received when the phase modulation method is used, the phase modulation method may be selected as the optimum modulation method of the other power line carrier communication device. According to this, when the OFDM modulation method can be used, the high-speed and large-capacity data communication is realized using the OFDM modulation method, and the OFDM modulation method cannot be used because it is noisy or too far away from the communication partner. However, when the phase modulation method can be used, it is possible to reliably deliver the data far away using the phase modulation method.

  In the power line carrier communication apparatus, the plurality of modulation schemes include an OFDM modulation scheme, a first phase modulation scheme that uses the first frequency, and a second frequency that uses a second frequency different from the first frequency. And when the response signal is received when the OFDM modulation method is used for modulating the carrier signal, the OFDM modulation method is used as the optimum modulation method for the other power line carrier communication apparatus. When a response signal is not received when the OFDM modulation method is used to modulate the carrier signal, and a response signal is received when the first phase modulation method is used to modulate the carrier signal The first phase modulation method is selected as the optimum modulation method for the other power line carrier communication device, and a response signal is received when the OFDM modulation method is used for modulating the carrier signal. And a response signal is not received when the first phase modulation method is used for modulating the carrier signal, and a response signal is received when the second phase modulation method is used for modulating the carrier signal. When received, the second phase modulation method may be selected as the optimum modulation method of the other power line carrier communication device. According to this, when the OFDM modulation method can be used, high-speed and large-capacity data communication is realized using the OFDM modulation method, and when the first phase modulation method can be used even when the OFDM modulation method cannot be used. Using the first phase modulation method, it is possible to reliably deliver data far away. Further, when there is an interference wave having the first frequency, the second phase modulation method can be used.

  In the power line carrier communication apparatus, the broadcast transmission data may be transmitted a plurality of times while selecting the same modulation method a plurality of times. According to this, since it is possible to confirm over a predetermined number of times that communication is not possible depending on a certain modulation method, the modulation method can actually be used because communication was not possible due to temporary factors such as pulse noise. Nevertheless, it can be prevented that it is determined that it cannot be used.

  ADVANTAGE OF THE INVENTION According to this invention, in the power line carrier communication apparatus using a low frequency band, it can be compatible with high-speed and large-capacity data communication while delivering data reliably far away.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a system configuration and functional blocks of a power line carrier communication apparatus 1 according to the present embodiment. As shown in the figure, the power line carrier communication device 1 includes an interface unit 5, a communication unit 10, a selection unit 11, a modulation unit 12, a transmission unit 13, a multiplexer 14, a reception unit 15, a synchronization detection unit 16, a control unit 17, Each functional unit of the demodulator 18 and the selector 19 is configured.

  This power line carrier communication apparatus 1 communicates with other power line carrier communication apparatuses 1 having the same configuration. To give a specific example, for example, when used for meter reading of a home electric meter, the power line carrier communication device 1 is installed in a utility pole and each home meter, and a power line installed between them is used for mutual communication. To communicate.

  The interface unit 5 is an interface with a host device such as a CPU (not shown), and receives upper layer data from the host device and outputs it to the communication unit 10. Also, the upper layer data is received from the communication unit 10 and is output to the upper device. The communication unit 10 is a functional unit that processes transmission / reception signals including a header, and is configured by, for example, a DSP (Digital Signal Processor). As specific processing, supply of higher layer data to be transmitted is received from the interface unit 5, a header including pilot data, a destination MAC address, and the like is added, and the data is transmitted to the selection unit 11 as transmission data. In addition, receiving data input including a header and higher layer data is received from the selection unit 19, processing corresponding to the header therein is performed, and output of higher layer data to the interface unit 5 is performed.

  The process according to the header includes a process of transmitting predetermined response data (Acknowledge) to the received data as one of the transmission data. That is, the communication unit 10 is configured to return response data each time a signal is received from another power line carrier communication device 1. A signal including response data is referred to as a response signal. Therefore, if the communication unit 10 does not receive the response data within a predetermined time after transmitting the transmission data other than the response data, the communication unit 10 retransmits the transmission data as not being received normally. I do.

  The power line carrier communication device 1 is configured to perform communication by a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method. That is, the communication unit 10 attempts to receive once (carrier sense) before starting transmission, and transmits transmission data if a transmission signal of another device is not detected. When the transmission signal of another device is detected, the transmission end of the transmission signal is monitored, and when the transmission end is detected, the transmission data is transmitted after waiting for a predetermined time. The predetermined time is determined to be shorter as the number of waiting times increases.

  The selection unit 11 selects one modulation method from a plurality of modulation methods supported by the modulation unit 12 in accordance with an instruction (described later) of the control unit 17. In the present embodiment, the modulation unit 12 corresponds to the three systems of the OFDM modulation system, the 115 kHz phase modulation system, and the 132 kHz phase modulation system, and is selected from these. As will be described later, the modulation unit 12 has an input end for each of these modulation schemes, and the selection unit 11 sends the transmission data input from the communication unit 10 to the input end corresponding to the selected modulation scheme. Output.

  The modulation unit 12 modulates a carrier signal based on transmission data using one modulation method selected from a plurality of modulation methods. Specifically, it has an OFDM modulation unit 120 that performs modulation by the OFDM modulation method, a phase modulation unit 125 that performs modulation by the 115 kHz phase modulation method, and a phase modulation unit 126 that performs modulation by the 132 kHz phase modulation method. The carrier wave signal is modulated using either of them. Each will be described in detail below.

  The OFDM modulation unit 120 includes an S / P (serial / parallel conversion) unit 121, a subcarrier modulation unit 122, and an IFFT unit 123 (inverse Fourier transform). Among these, the S / P unit 121 has an input terminal for receiving serial input of transmission data, and the transmission data input from the communication unit 10 via this input terminal is converted into parallel data having a stream for each subcarrier. Convert to

  The subcarrier modulation unit 122 assigns the data from the S / P unit 121 to each subcarrier, and includes a given phase modulation scheme (phase modulation scheme as primary modulation, phase amplitude modulation scheme) for each subcarrier. ) To map to the complex plane. For example, when 64QAM is used, it is mapped to any of 64 points on the complex plane.

  The IFFT unit 123 performs OFDM modulation as secondary modulation. That is, the modulation data for each subcarrier determined by the subcarrier modulation unit 122 is collectively subjected to inverse Fourier transform by the IFFT unit 123. The modulation processing in the OFDM modulation unit 120 has been described above.

  The phase modulators 125 and 126 have input terminals that receive serial input of transmission data, respectively, and phase modulate a 115 kHz carrier signal and a 132 kHz carrier signal based on the input transmission data.

  The modulation unit 12 adds a predetermined pilot signal to the modulation signal obtained by the OFDM modulation unit 120 or the phase modulation units 125 and 126 as described above, and outputs the result to the transmission unit 13. The processing so far is performed by digital processing, and the signal output from the modulation unit 12 is a digital signal having an amplitude indicated by a digital value.

  The modulation unit 12 controls the amplitude of the output signal according to the modulation method used for the modulation process. That is, the amplitude of the signal modulated by the OFDM modulation unit 120 is controlled so that the total value of the amplitudes of the subcarriers when being sent to the transmission path is 100 mW or 100 mW or less. Here, “when sent to the transmission line” means after being amplified by the AMP unit 132 described later. On the other hand, the amplitude of the signals modulated by the phase modulation units 125 and 126 is controlled so that the amplitude when sent to the transmission line is 350 mW or 350 mW or less. These numerical values are in accordance with the regulations (carrier wave output) of the Radio Law Enforcement Rules shown in Table 1 above.

  The transmission unit 13 has a configuration for converting the signal input from the modulation unit 12 into a signal that can be transmitted to the transmission path. Specifically, a D / A (digital / analog conversion) unit 130 that converts to an analog signal, an LPF (low-pass filter) unit 131 that removes unnecessary high-frequency components from the output signal of the D / A unit 130, and an LPF unit 131 And an AMP (amplification) unit 132 that amplifies the signal that has passed through the signal at a predetermined amplification factor. The signal output from the AMP unit 132 is sent to the transmission line via the multiplexer 14.

  Here, the signal formats of the signals sent to the transmission line as described above are summarized.

  FIG. 2 is a diagram illustrating a signal format of a signal sent to the transmission path. As shown in the figure, a signal to be transmitted includes a carrier signal modulated based on a header and higher layer data (hereinafter, transmission data) generated by the communication unit 10 and a pilot added by the modulation unit 12. Signal. The header includes predetermined pilot data, a destination MAC address (a MAC address of the power line carrier communication device 1 that is a destination), a local station MAC address, and the like. It is also possible to include a predetermined broadcast address as the destination MAC address. In this case, all the power line carrier communication apparatuses 1 that can be received receive the signal shown in FIG. 2 and return a response signal.

  Further, as described above, the subcarrier modulation unit 122 and the phase modulation units 125 and 126 perform phase modulation, but there are various modulation schemes having different transmission speeds even if referred to as phase modulation. For example, BPSK, π / 4 shift QPSK, 16QAM, 64QAM, etc. Which of these is used may be determined in advance, or may be determined adaptively according to the transmission path state by performing so-called adaptive control. In this case, the upper layer data portion is modulated by an adaptively determined modulation scheme, while the header portion is modulated using a predetermined modulation scheme (for example, BPSK) that allows communication even when the transmission path condition is relatively poor. It is preferable to include information (modulation method information) indicating the modulation method of the upper layer data portion in the header. Thereby, the power line carrier communication apparatus 1 on the reception side can first acquire the modulation scheme of the higher layer data portion by demodulating the header portion and referring to the modulation scheme information therein.

  The receiving unit 15 has a configuration for receiving a signal that has arrived on the transmission path and converting it into a digital signal for use in the processing of the demodulating unit 18. Specifically, an LPF (low-pass filter) unit 150 that removes unnecessary high-frequency components from the signal received via the multiplexer 14, an AMP (amplification) unit 151 that amplifies the signal that has passed through the LPF unit 150, and after amplification And an A / D (analog / digital conversion) unit 152 that samples and converts the signal into a digital signal and outputs the digital signal to the demodulation unit 18.

  The synchronization detection unit 16 monitors whether or not the above-described pilot signal is included in the digital signal output from the reception unit 15. When it is detected that it is included, the control unit 17 is notified of the detection result and the detected modulation method. Upon receiving this notification, the control unit 17 causes the demodulation unit 18 to start demodulation processing. In addition to this, the control unit 17 also performs processing for determining a modulation method to be used at the time of transmission, details of which will be described later.

  The demodulator 18 demodulates the digital signal input from the receiver 15 using a plurality of modulation schemes. Specifically, an OFDM demodulator 180 that demodulates the received signal using the OFDM modulation method, a phase demodulator 185 that demodulates the received signal using the 115 kHz phase modulation method, and a demodulation of the received signal using the 132 kHz phase modulation method. And a phase demodulator 186 for performing demodulation of received signals in parallel. Alternatively, a demodulation designation based on the modulation method detected by the synchronization detection unit 16 is received from the control unit 17, and only the demodulation unit corresponding to the modulation method is operated to perform demodulation. Hereinafter, the former demodulation operation will be described in detail.

  The OFDM demodulator 180 includes an FFT (Fourier transform) unit 181, a subcarrier demodulator 182 and a P / S (parallel / serial conversion) unit 183, and performs OFDM demodulation assuming that the received signal is OFDM modulated. . That is, FFT section 181 obtains a signal for each subcarrier by Fourier transforming the received signal and outputs the signal to subcarrier demodulation section 182. The subcarrier demodulation unit 182 performs signal demapping for each subcarrier according to the phase modulation method determined as described above, acquires parallel data including a stream for each subcarrier, and outputs the parallel data to the P / S unit 183. To do. The P / S unit 183 converts the parallel data input from the subcarrier demodulation unit 182 into serial data, and outputs the serial data to the selection unit 19.

  The phase demodulation units 185 and 186 perform phase demodulation assuming that the input digital signals are modulation signals of a 115 kHz carrier signal and a 132 kHz carrier signal, respectively, and output the result to the selection unit 19.

  The selection unit 19 determines whether or not the pilot data is included in each demodulated data input from the demodulating unit 18 (data obtained by demodulation by the OFDM demodulating unit 180 and the phase demodulating units 185 and 186, respectively). . Then, the demodulated data including the pilot data is selected and output to the communication unit 10 and simultaneously the determination result is notified to the control unit 17. By performing this selection, it is possible to suitably receive a carrier wave signal modulated by any of the three modulation methods.

  When the demodulation designation based on the modulation scheme detected by the synchronization detection unit 16 is received from the control unit 17 and only the demodulation unit corresponding to the modulation scheme is operated to perform demodulation, the selection unit 19 performs the demodulation. The output from the unit may be selected.

  When adaptive control is performed on the modulation scheme of the upper layer data portion, the selection unit 19 acquires information indicating the modulation scheme included in the header and outputs the information to the subcarrier demodulation unit 182 or the phase demodulation units 185 and 186. Thereby, the subcarrier demodulation unit 182 and the phase demodulation units 185 and 186 can suitably demodulate the carrier wave signal.

  Now, a process for determining a modulation method used at the time of transmission will be described. This process is led by the control unit 17.

  First, an outline of the control unit 17 will be described. As shown in FIG. 1, the control unit 17 includes an optimal modulation scheme selection unit 170 and a storage unit 171. The optimum modulation method selection unit 170 changes the modulation method used by the modulation unit 12 (changes the modulation method selected by the selection unit 11), and transmits to the communication unit 10 broadcast transmission data (the destination MAC address of the header is By transmitting the transmission data (broadcast address) a plurality of times, the modulation scheme used for modulating the carrier signal is changed to a plurality of modulation schemes (here, OFDM modulation scheme, 115 kHz phase modulation scheme, 132 kHz phase modulation scheme). The transmission data for broadcast is transmitted a plurality of times while selectively changing from the above three).

  Then, the optimum modulation scheme selecting unit 170 selects one of the plurality of modulation schemes based on the reception result of the response signal transmitted from the other power line carrier communication apparatus 1 for the plurality of transmissions. It selects as an optimal modulation system of the other power line carrier communication apparatus 1. Since the transmission data is for broadcasting, the response signal is received from a plurality of other power line carrier communication apparatuses 1. The optimum modulation method selection unit 170 selects an optimum modulation method for each of the plurality of other power line carrier communication devices 1. The selected result is stored in the storage unit 171 as an optimum modulation method storage table.

  FIG. 3 is a diagram illustrating an example of the optimum modulation method storage table stored in the storage unit 171. As shown in the figure, in this table, the MAC address of the power line carrier communication apparatus 1 and the optimum modulation scheme for communication with each are stored in association with each other.

  Note that the optimal modulation scheme selection unit 170 preferably assigns priorities to a plurality of modulation schemes. As an example, when a plurality of modulation schemes include an OFDM modulation scheme and a phase modulation scheme, the optimal modulation scheme selection unit 170 gives a higher priority in the order of the OFDM modulation scheme and the phase modulation scheme. Then, for the power line carrier communication apparatus 1 for which the response signal is received for both the OFDM modulation method and the phase modulation method, the power line carrier for which the OFDM modulation method having a high priority is selected and the response signal is received only for the phase modulation method. For the communication apparatus 1, the phase modulation method is selected.

  When transmitting transmission data to another power line carrier communication device 1, the control unit 17 refers to the optimum modulation method storage table and acquires the optimum modulation method of the other power line carrier communication device 1. Then, the modulation unit 12 performs modulation using the acquired modulation method.

  More preferably, the optimum modulation scheme selection unit 170 causes the modulation unit 12 to modulate the transmission data for broadcast a plurality of times (for example, seven times) using the same modulation scheme. This is realized by causing the communication unit 10 to output transmission data for broadcast a plurality of times in a state where the modulation scheme selected by the selection unit 11 is fixed. The number of times of 7 is in accordance with the regulations of the Radio Law Enforcement Rules shown in Table 1 above (up to 7 times of automatic retransmission). In practice, the number of times less than this may be set appropriately. it can.

  Hereinafter, the processing will be described in more detail with reference to the processing flow of the optimum modulation scheme selection unit 170 and the processing sequence between the power line carrier communication apparatuses 1.

  4 and 5 are diagrams illustrating a processing flow of the optimum modulation scheme selection unit 170. FIG. The processing shown in the figure is performed periodically. The carrier signals transmitted in this processing flow are all modulated based on broadcast transmission data.

  First, the optimum modulation scheme selection unit 170 controls the selection unit 11 and the communication unit 10 to transmit a carrier wave signal modulated using the OFDM modulation scheme seven times (steps S1 and S2). Next, the optimum modulation method selection unit 170 controls the selection unit 11 and the communication unit 10 to transmit the carrier wave signal modulated using the 115 kHz phase modulation method seven times (steps S3 and S4). Next, the optimum modulation method selection unit 170 controls the selection unit 11 and the communication unit 10 to transmit the carrier wave signal modulated using the 132 kHz phase modulation method seven times (steps S5 and S6).

  Note that the selection order and the number of selections of the modulation scheme in the processing of steps S1 to S5 are not particularly limited to those described above, and it is sufficient that the carrier signal can be transmitted a plurality of times with the same modulation scheme. As an example of a modification, the OFDM modulation method, the 115 kHz phase modulation method, and the 132 kHz phase modulation method may be selected once in any order and repeated seven times.

  The optimum modulation method selection unit 170 monitors the reception of the response signal while performing the processing up to S6. And the process of step S8-step S13 is performed by making all the power line carrier communication apparatuses 1 in which the response signal was received at least once with respect to 21 times of transmission into a process target sequentially (step S7, S14). Hereinafter, these processes will be described.

  First, the optimum modulation scheme selection unit 170 determines whether or not a response signal has been received from the power line carrier communication apparatus 1 to be processed even once out of seven times for a carrier signal modulated using the OFDM modulation scheme ( Step S8). That is, it is determined whether or not the power line carrier communication apparatus 1 to be processed has transmitted response data to the transmission data output to the communication unit 10 with the selection unit 11 selecting the OFDM modulation scheme. As a result, when it is determined that it has been received (affirmative determination in step S8), the MAC address of the power line carrier communication apparatus 1 to be processed and the OFDM modulation scheme are stored in the optimum modulation scheme storage table in association with each other (step S8). S9), the process for the power line carrier communication apparatus 1 is terminated, and the process is transferred to the next power line carrier communication apparatus 1. On the other hand, if it is determined that it has not been received (No determination in step S8), the process proceeds to step S10.

  In step S10, the optimum modulation method selection unit 170 determines whether or not a response signal has been received from the power line carrier communication apparatus 1 to be processed even once out of seven times for the carrier signal modulated using the 115 kHz phase modulation method. Is determined (step S10). That is, it is determined whether or not the power line carrier communication device 1 to be processed has transmitted response data to the transmission data output to the communication unit 10 in a state where the selection unit 11 selects the 115 kHz phase modulation method. As a result, when it is determined that it has been received (Yes determination in step S10), the MAC address of the power line carrier communication device 1 to be processed and the 115 kHz phase modulation method are stored in the optimum modulation method storage table in association with each other. (Step S11), the process for the power line carrier communication apparatus 1 is finished, and the process is transferred to the next power line carrier communication apparatus 1. On the other hand, when it determines with not having received (No determination of step S10), a process is moved to step S12.

  In step S12, the optimum modulation method selection unit 170 determines whether or not a response signal has been received from the power line carrier communication apparatus 1 to be processed at least once out of seven times for the carrier signal modulated using the 132 kHz phase modulation method. Is determined (step S12). That is, it is determined whether or not the power line carrier communication device 1 to be processed has transmitted response data to the transmission data output to the communication unit 10 in a state where the selection unit 11 selects the 132 kHz phase modulation method. As a result, if it is determined that it has been received (Yes determination in step S12), the optimum modulation method storage table stores the MAC address of the power line carrier communication device 1 to be processed and the 132 kHz phase modulation method in association with each other. (Step S13), the process for the power line carrier communication apparatus 1 is terminated, and the process proceeds to the next power line carrier communication apparatus 1. On the other hand, when it determines with not having received (No determination of step S12), the process about the said power line carrier communication apparatus 1 is complete | finished, and a process is moved to the next power line carrier communication apparatus 1. FIG.

  Note that the negative determination in step S12 should not occur. That is, the loop processing of steps S7 to S14 is performed for the power line carrier communication apparatus 1 that has received a response signal at least once for the transmission of 21 carrier signals. In either case, a response signal should have been received. Therefore, the process of step S12 may be omitted, and if a negative determination is made in step S10, the process of step S13 may be performed immediately.

  As described above, the optimum modulation method selection unit 170 determines an optimum modulation method for each power line carrier communication device 1 of the communication partner and stores it in the optimum modulation method storage table. As a result, the loop processing in steps S7 to S14 gives high priority in the order of the OFDM modulation scheme, the 115 kHz phase modulation scheme, and the 132 kHz phase modulation scheme.

  Next, FIG. 6 is a diagram showing a processing sequence between the power line carrier communication apparatuses 1. Devices 1A to 1C shown in the figure are each a power line carrier communication device 1. Here, a case will be described as an example where apparatus 1A determines a modulation scheme used when transmitting data to apparatuses 1B and 1C.

  First, the device 1A transmits a total of 21 broadcast transmission data while changing the modulation method (step S21). This is the process of steps S1 to S6 (FIG. 4) described above. When the transmission data transmitted from the device A can be received, the devices B and C return a response signal for each transmission data (step S22). The device A receives these response signals, determines the optimum modulation method for each device, and stores it in the optimum modulation method storage table (step S23). This process is the process of steps S7 to S14 (FIG. 5) described above.

  Thereafter, for example, when data to be transmitted to the device 1B is generated (step S24), the device 1A transmits transmission data using the modulation method stored in the optimum modulation method storage table for the device 1B ( Step S25). Upon receiving this transmission data, apparatus 1B transmits a response signal (step S26).

  When a predetermined time has elapsed since the start of the process of step S21, apparatus 1A repeats the same process as the process of steps S21 to S23 again (steps S27 to S29). This makes it possible to always keep the optimum modulation system storage table up to date. It should be noted that the timing for performing the repetitive processing may be after a predetermined time has passed in this way, for example, when a jamming wave is detected or when communication fails.

  As described above, the power line carrier communication apparatus 1 can communicate using the optimum modulation method for each power line carrier communication apparatus 1 of the communication partner. Therefore, in the power line carrier communication apparatus 1 using the low frequency band, the data is surely delivered to a distant place (when using the phase modulation method of 115 kHz or 132 kHz), and the high-speed and large-capacity data communication (when using the OFDM modulation method). Can be compatible.

  In addition, when the OFDM modulation method can be used, high-speed and large-capacity data communication is realized using the OFDM modulation method, and the OFDM modulation method cannot be used because it is noisy or too far away from the communication partner. However, when the phase modulation method can be used, it is possible to reliably deliver the data far away using the phase modulation method. In addition, when there is a 115 kHz interference wave, it is possible to further switch to the 132 kHz phase modulation method.

  In addition, since the optimum modulation method selection unit 170 can confirm over a predetermined number of times that communication cannot be performed depending on a certain modulation method, communication cannot be performed due to a temporary factor such as pulse noise. Although the modulation method can be used, it can be prevented that it is determined that the modulation method cannot be used.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to such embodiment at all, and this invention can be implemented in various aspects in the range which does not deviate from the summary. Of course.

  For example, in the above-described embodiment, an example using each modulation method of the OFDM modulation method, the 115 kHz phase modulation method, and the 132 kHz phase modulation method has been described. However, the modulation method to which the present invention is limited is limited to these. Instead, the present invention is widely applicable when using a plurality of modulation schemes.

It is a figure which shows the system configuration | structure and functional block of the power line carrier communication apparatus by embodiment of this invention. It is a figure which shows the signal format of the signal sent out to the transmission line by embodiment of this invention. It is a figure which shows the example of the optimal modulation system memory | storage table by embodiment of this invention. It is a figure which shows the processing flow of the control part by embodiment of this invention. It is a figure which shows the processing flow of the control part by embodiment of this invention. It is a figure which shows the process sequence between the power line carrier communication apparatuses by embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power line carrier communication apparatus 5 Interface part 10 Communication part 11 Selection part 12 Modulation part 13 Transmission part 14 Multiplexer 15 Reception part 16 Synchronization detection part 17 Control part 18 Demodulation part 19 Selection part 120 OFDM modulation part 121 S / P part 122 Subcarrier Modulation unit 123 IFFT unit 125, 126 Phase modulation unit 130 D / A unit 131 LPF unit 132 AMP unit 150 LPF unit 151 AMP unit 152 A / D unit 170 Optimal modulation method selection unit 171 Storage unit 180 OFDM demodulation unit 181 FFT unit 182 Subcarrier demodulation unit 183 P / S unit 185, 186 Phase demodulation unit

Claims (4)

While selectively changing the modulation method used for modulating the carrier signal from a plurality of modulation methods, the transmission data for broadcast is transmitted a plurality of times,
Based on the reception result of the response signal transmitted from another power line carrier communication device for the plurality of transmissions, one of the plurality of modulation methods is set as the optimum modulation method of the other power line carrier communication device. Selected,
A power line carrier communication apparatus, wherein when transmitting transmission data to the other power line carrier communication apparatus, a carrier wave signal is modulated using the optimum modulation method. The plurality of modulation schemes include an OFDM modulation scheme and a phase modulation scheme,
When a response signal is received when the OFDM modulation method is used to modulate the carrier signal, the OFDM modulation method is selected as the optimum modulation method of the other power line carrier communication device,
When the response signal is not received when the OFDM modulation method is used for modulating the carrier signal and the response signal is received when the phase modulation method is used for modulating the carrier signal, the phase modulation method is used. The power line carrier communication apparatus according to claim 1, wherein the power line carrier communication apparatus is selected as an optimum modulation method for the other power line carrier communication apparatus. The plurality of modulation schemes include an OFDM modulation scheme, a first phase modulation scheme using a first frequency, and a second phase modulation scheme using a second frequency different from the first frequency,
When a response signal is received when the OFDM modulation method is used to modulate the carrier signal, the OFDM modulation method is selected as the optimum modulation method of the other power line carrier communication device,
When a response signal is not received when the OFDM modulation scheme is used for modulating the carrier signal, and a response signal is received when the first phase modulation scheme is used for modulating the carrier signal, Selecting the first phase modulation scheme as the optimal modulation scheme of the other power line carrier communication device;
No response signal is received when the OFDM modulation scheme is used for modulating the carrier signal, and no response signal is received when the first phase modulation scheme is used for modulating the carrier signal, and When a response signal is received when the second phase modulation method is used for modulating the carrier signal, the second phase modulation method is selected as the optimum modulation method of the other power line carrier communication device. The power line carrier communication apparatus according to claim 1, wherein   4. The power line carrier communication device according to claim 1, wherein transmission of the transmission data for broadcast is performed a plurality of times while selecting the same modulation method a plurality of times. 5.

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