JP5296581B2 - Power line carrier communication apparatus and power line carrier communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform both of OFDM communication with another slave unit using a signal of either one of first and second frequency bands and OFDM communication with a master unit using a signal of the other frequency band. <P>SOLUTION: A power-line carrier communication apparatus functioning as one of slave units bus-connected to a power line connected with the master unit includes a receiving part 37, a demodulation part and a control part. The receiving part 37 includes: a signal passage 41 for interrupting signals of frequencies other than the first frequency band; a signal passage 42 for interrupting signals of frequencies other than the second frequency band; a first switch means 44 arranged in the signal passage 41; and a second switch means 46 arranged in the signal passage 42. When a repeater slave unit is operated, the control part, in a waiting state and in communication with the other slave set, turns on the first switch means 44 and turns off the second switch 46, and in communication with the master unit, turns off the first switch means 41 and turns on the second switch means 46. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a power line carrier communication device and a power line carrier communication system, and more particularly to a power line carrier communication system that performs power line carrier communication between a master unit and a plurality of slave units, and a power line carrier communication device used as a repeater in the power line carrier communication system. About.

  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 (hereinafter referred to as the low frequency band) was accepted as the frequency band for power line carrier communications. However, due to the amendment of radio wave law in October 2006, the frequency band is limited to 2 MHz. It has been observed that a higher bandwidth of 30 MHz is used. 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.

  However, the conventional power line carrier communication system using a low frequency band is still frequently used. Specifically, examples are used for meter reading (data collection) of electric meters at each house in an apartment house and device control from a remote location.

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

The Radio Law categorizes power line carrier communication devices that use a low frequency band 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 kHz to 450 kHz, and , 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.

  The OFDM modulation system has the advantage that relatively high-speed and highly reliable communication can be realized because the band of 10 kHz to 450 kHz is fully used and adaptive modulation for each subcarrier can be performed. Therefore, in the power line carrier communication system in the low frequency band, communication using the OFDM modulation method (hereinafter referred to as OFDM communication) is usually used. On the other hand, the current radio wave law enforcement regulations restrict the total output value of all subcarriers to 100 mW or less, so that OFDM communication 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.

  A specific example of a power line carrier communication system using a low frequency band will be given. FIG. 15 (a) shows a power line carrier communication system for meter reading of each house in an apartment house A having three floors and seven rooms on each floor. As shown in the figure, this system includes a master unit D0 installed on the first floor (for example, near the distribution board) and power lines B1 to B3 for each floor connected to the master unit D0, and each power line B1. The slave units D11 to D37 for each door are connected by bus to .about.B3.

  FIG. 15B shows a network topology of the power line carrier communication system shown in FIG. As shown in the figure, in this power line carrier communication system, logically, the parent device D0 and each of the child devices D11 to D37 are directly connected, and perform direct communication by OFDM communication with each other.

  FIG. 16 is a schematic diagram showing communication steps between the parent device D0 and each of the child devices D11 to D37. As shown in the figure, the master unit D0 directly receives meter reading data from each of the slave units D11 to D37, and the total number of communication steps is 42 steps.

  Patent Document 1 discloses a technique for extending the communication distance of a power line carrier communication system by inserting a repeater (Note: referred to as “repeater” in Patent Document 1) between power line carrier communication devices. ing.

JP 2003-229793 A

  15 (b) and 16 show an example in which the master unit and each slave unit perform direct communication by OFDM communication in the power line carrier communication system shown in FIG. 15 (a). There are cases where such direct communication is not possible. For example, when the distance between the parent device and the child device is too large, it is difficult for the parent device and the child device to communicate directly by OFDM communication.

  Therefore, as shown in FIG. 17 (a), repeaters R1 to R3 are installed on the power lines B1 to B3, and repeaters R1 to R3 are connected to the slave units that cannot communicate directly with the master unit D0 by OFDM communication. It is conceivable to perform OFDM communication with the parent device via the network. However, if repeaters R1 to R3 are used in this way, there arises a problem that the total number of communication steps increases. This will be described in detail below.

  FIG. 17B shows an example of the network topology of the power line carrier communication system shown in FIG. As shown in the figure, in this power line carrier communication system, only the slave units D11 to D14, D21 to D23, D31 to D32 and repeaters R1 to R3 are logically directly connected to the master unit D0. Other slave units D15 to D17, D24 to D27, and D33 to D37 are connected to the master unit D0 through repeaters R1 to R3.

  FIG. 18 is a schematic diagram showing communication steps between the parent device D0 and each of the child devices D11 to D37. As shown in the figure, the master unit D0 receives meter reading data directly from the slave units D11 to D14, D21 to D23, and D31 to D32, while the repeater from the slave units D15 to D17, D24 to D27, and D33 to D37. Meter reading data is received via R1 to R3.

  In direct communication, the number of communication steps required to receive meter reading data from one slave unit is two. On the other hand, in the case of using a repeater, communication between the master unit D0 and the repeater and communication between the repeater and the slave unit are sequentially performed, so the number of communication steps required for receiving meter-reading data from one slave unit is four steps. . Therefore, the total number of communication steps in this case is 66 steps as shown in FIG. 18, and more than 1.5 times of communication steps are required when no repeater is used (42 steps).

  Therefore, recently, the low frequency band is divided into first and second frequency bands, the first frequency band is used for direct communication between the parent device, the child device, and the repeater, and the second frequency band is used for communication between the repeater and the child device. There has been proposed a technique for reducing the total number of communication steps by using the frequency band. In this technique, while the repeater is performing OFDM communication with the child device, the parent device can perform OFDM communication with other child devices, so that the total number of communication steps is reduced.

  However, as described above, the repeater needs to be equipped with two OFDM modems, ie, the first OFDM modem for the first frequency band and the second OFDM modem for the second frequency band. This is not preferable from an economic point of view.

  In addition, a call signal transmitted when the parent device or the child device tries to start communication is also transmitted separately in the first and second frequency bands. Therefore, it is necessary for the repeater to be able to receive both the first and second frequency bands, but when the repeater demodulates the call signal, the repeater uses a frequency band that is not the frequency band to which the call signal belongs. There is a problem that the received signal becomes interference noise and affects the demodulation accuracy.

  Therefore, one of the objects of the present invention is to perform OFDM communication with other slave units using one signal in the first and second frequency bands by one OFDM modem, and in the first and second frequency bands. An object of the present invention is to provide a power line carrier communication apparatus capable of performing both OFDM communication with a parent device using the other signal.

  Another object of the present invention is to provide a power line carrier communication apparatus and a power line carrier communication system capable of improving the demodulation accuracy of a repeater call signal.

  In order to achieve the above object, a power line carrier communication apparatus according to the present invention is a power line carrier communication apparatus functioning as one of slave units connected by bus to a power line connected to a master unit, and receives a signal flowing through the power line. A receiving unit; a demodulating unit that demodulates a received signal of the receiving unit; and a control unit, wherein the receiving unit is installed between the power line and the demodulating unit, and has a frequency other than the first frequency band. A first signal path for blocking a signal, and a second signal path that is installed between the power line and the demodulator and blocks a signal of a frequency other than the second frequency band that does not overlap the first frequency band. A signal path; a first switch means provided in the first signal path; and a second switch means provided in the second signal path. When communicating with other slave units, The switch means is turned on, the second switch means is turned off, and when performing communication with the master unit, the first switch means is turned off and the second switch means is turned on. To do.

  According to the present invention, even if there is only one OFDM modem constituted by the receiving unit and the demodulating unit, communication with the subordinate slaves using the signal of the first frequency band, and the second frequency band It is possible to perform both the OFDM communication with the base unit using the above signal. In addition, since only the signal in the first frequency band is input to the demodulation unit during standby, interference noise is reduced and the demodulation accuracy of the calling signal is improved.

  In the power line carrier communication apparatus, the demodulator includes a first OFDM signal demodulation processor that demodulates the OFDM signal in the first frequency band, and a second OFDM signal demodulation processor that demodulates the OFDM signal in the second frequency band. And a phase modulation signal demodulation processing unit that demodulates a phase modulation signal of a frequency belonging to the first frequency band, and using the phase modulation signal demodulation processing unit or the first OFDM signal demodulation processing unit, It is good also as demodulating.

  According to this, it is possible to generate the calling signal by using either the OFDM signal of the first frequency band or the phase modulation signal of the frequency belonging to the first frequency band. Therefore, it is possible to unify the calling signal for the slave unit operating as a repeater from the master unit and subordinate slave units (hereinafter referred to as repeater slave unit) into a signal of the first frequency band. In other words, the master unit can transmit a call signal using a phase-modulated signal having a frequency belonging to the first frequency band, and the subordinate slave units can transmit the call signal using an OFDM signal in the first frequency band. The demodulation accuracy of the call signal of the repeater slave unit is improved.

  Further, in each of the power line carrier communication devices, the demodulation unit is provided between the first OFDM signal demodulation processing unit and the reception unit, and performs a first OFDM signal synchronization detection of the OFDM signal of the first frequency band Synchronization detection means, second OFDM signal synchronization detection means provided between the second OFDM signal demodulation processing section and the reception section, for detecting synchronization of the OFDM signal in the second frequency band, and the phase modulation signal demodulation Phase modulation signal synchronization detection means provided between the processing unit and the reception unit for detecting the synchronization of the phase modulation signal of the frequency belonging to the first frequency band, and further comprising the first OFDM signal demodulation processing unit Starts demodulating in response to the detection of synchronization by the first OFDM signal synchronization detecting means, and the second OFDM signal demodulation processing unit performs the second OFDM signal synchronization detection. The phase modulation signal demodulation processing unit may start demodulation in response to the detection of synchronization by the phase modulation signal synchronization detection unit. . According to this, it becomes possible to appropriately perform demodulation in each modulation method.

  The power line carrier communication system according to the present invention includes a master unit and a power line connected to the master unit, and a plurality of slave units each including a repeater function are bus-connected to the power line, and the repeater slave unit and the repeater unit are connected to the power line. Communication between the slave units under the repeater slave unit is performed by the first OFDM communication using the first frequency band, and the direct communication between the master unit, the direct communication slave unit, and the repeater slave unit is performed using the first frequency band. A power line carrier communication system that performs a second OFDM communication using a second frequency band that does not overlap with a frequency band, and a call signal when the master calls a repeater slave belongs to the first frequency band It is transmitted by phase modulation communication using a frequency, and a call signal when the repeater slave calls a slave under its control is transmitted by the first OFDM communication

  According to this, since the master unit transmits the call signal by phase modulation communication, it is possible to transmit the call signal with a high output of 350 mW as shown in Table 1. Further, since the slave unit functioning as a repeater only has to wait for a call signal in the first frequency band, it is not necessary to wait for a signal in the second frequency band that causes interference noise. As a result, the demodulation accuracy of the repeater call signal is improved.

  According to the present invention, the power line carrier communication apparatus can perform communication between the repeater slave unit and its subordinate slave units and the second frequency band by using one OFDM modem during standby and using the signal of the first frequency band. It is possible to perform both OFDM communication between the parent device using the signal and the direct communication child device and the repeater child device.

(A) is a figure which shows the system configuration | structure of the power line carrier communication system by embodiment of this invention. (B) is a figure which shows the network topology of the power line carrier communication system shown to (a). It is explanatory drawing of the 1st and 2nd frequency band by embodiment of this invention. (A)-(d) is a figure which shows the frequency spectrum image of the OFDM signal by embodiment of this invention. It is a figure which shows the communication state of each subunit | mobile_unit in a power line carrier communication system by embodiment of this invention, and a main | base station. (A) is a figure which shows the functional block of the main | base station by embodiment of this invention. (B) is a figure which shows the functional block of the subunit | mobile_unit by embodiment of this invention. It is a figure which shows the functional block of the modem with which the subunit | mobile_unit by embodiment of this invention is provided. (A)-(f) is a figure which shows the format of the signal transmitted / received between the main | base station and each subunit | mobile_unit by the embodiment of this invention, or between sub-units. It is a schematic diagram which shows the communication step between the main | base station and each subunit | mobile_unit by the embodiment of this invention, and between sub-units. It is a figure which shows the internal structure of the demodulation part provided in the modem of the subunit | mobile_unit by embodiment of this invention. It is a figure which shows the internal structure of the receiver provided in the modem of the subunit | mobile_unit by embodiment of this invention. (A) is a figure which shows the sequence of the communication performed between the main | base station and the subunit | mobile_unit by the embodiment of this invention, and between sub-units. (B) has shown the frequency band of each signal shown to (a), and the communication mode setting of the receiving part of a repeater subunit | mobile_unit. It is a figure which shows the process sequence of the main | base station by embodiment of this invention. It is a figure which shows the format of the signal for communication quality confirmation by embodiment of this invention. It is a figure which shows the time change of the frequency of the signal for communication quality confirmation by embodiment of this invention. (A) is a figure which shows the system configuration | structure of the power line carrier communication system by the background art of this invention. (B) is a figure which shows the network topology of the power line carrier communication system shown to (a). It is a schematic diagram which shows the communication step of the main | base station and each subunit | mobile_unit in the power line carrier communication system shown to Fig.15 (a). (A) is a figure which shows the system configuration | structure of the power line carrier communication system by the background art of this invention. (B) is a figure which shows the network topology of the power line carrier communication system shown to (a). It is a schematic diagram which shows the communication step of the main | base station and each subunit | mobile_unit in the power line carrier communication system shown to Fig.17 (a).

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

  Fig.1 (a) is a figure which shows the system configuration | structure of the power line carrier communication system 1 by this Embodiment. As shown in the figure, the power line carrier communication system 1 includes a master unit C0 and power lines B1 to B3 connected to the master unit C0, and each of the power lines B1 to B3 includes a repeater function. C11 to C37 are bus-connected. The master unit C0 and the slave units C11 to C37 are all power line carrier communication devices, and perform power line carrier communication based on the above-described OFDM communication or phase modulation communication. And it connects with terminal devices (a personal computer, an electric meter, etc.) which are not illustrated, and realizes communication between terminal devices.

  The power lines B1 to B3 are connected to each other at a connection point N (for example, a distribution board) provided in the vicinity of the parent device C0, and a signal flowing through one power line also flows to another power line. Therefore, in principle, signals of the same frequency cannot be sent to power lines B1 to B3 independently of each other at the same time. However, a signal transmitted by a slave whose distance from connection point N is more than a certain distance is transmitted to connection point N. Since it attenuates before reaching, it does not flow into other power lines. Therefore, if it is limited to such a signal, it is possible to simultaneously flow signals of the same frequency to power lines B1 to B3 independently of each other.

  Specifically, the power line carrier communication system 1 is installed in an apartment house A having three floors and seven rooms on each floor, for example, as in the example of the background art shown in FIG. Used to do In the following description, it is assumed that the terminal device connected to the parent device C0 is a personal computer, the terminal device connected to each child device is an electric meter, and meter reading data of each electric meter is acquired from the personal computer. . Of course, the present invention is not limited to a power line carrier communication system that acquires meter reading data of an electric meter.

  Here, before describing the details of the parent device C0 and each of the child devices C11 to C37, the first and second frequency bands obtained by dividing the low frequency band will be described.

In the power line carrier communication system 1, when performing OFDM communication, the low frequency band (10 kHz to 450 kHz) is divided into a _first frequency band F ₁ and a second frequency band F ₂ . That is, base unit C0 and each of sub units C11 to C37 generate OFDM signals (carrier signals modulated by the OFDM modulation scheme) using only subcarriers belonging to any one of the frequency bands.

FIG. 2 is an explanatory diagram of the first and second frequency bands. As shown in the figure, the first frequency band _{F 1} is the frequency band of 10KHz～220kHz, frequency band _{F 2} of the second is the frequency band of 240KHz～450kHz. Since the low frequency band is 10 kHz to 450 kHz, the first frequency band F ₁ generally occupies the lower half of the low frequency band, and the second frequency band F ₂ generally occupies the upper half.

Each figure in FIG. 3 shows a frequency spectrum image of the OFDM signal. FIG. 3A is a frequency spectrum image of an OFDM signal when OFDM communication is performed using the entire low frequency band. As shown in FIG. 3, the subcarrier of the OFDM signal in this case is a low frequency of 10 kHz to 450 kHz. Exists across the entire band. FIG. 3B is a frequency spectrum image of an OFDM signal when performing OFDM communication using only the first frequency band F ₁ (hereinafter referred to as first OFDM communication). As shown in FIG. In this case, the subcarrier of the OFDM signal exists only in the range of 10 kHz to 220 kHz. FIG. 3 (c) OFDM communication using only the second frequency band _{F 2} (hereinafter, second OFDM communication called.) Is the frequency spectrum image of the OFDM signal in the case of performing, as shown in the figure, the In this case, the subcarrier of the OFDM signal exists only in the range of 240 kHz to 450 kHz. FIG. 3D shows a state where OFDM signals by the first OFDM communication and OFDM signals by the second OFDM communication are mixed, and the subcarrier of the OFDM signal in this case is in the range of 220 kHz to 240 kHz. Except for the entire low frequency band.

  Here, the premise of the following description is demonstrated. In the following, it is assumed that the communication state between each child device in the power line carrier communication system 1 and the parent device C0 is as shown in FIG. That is, as shown in FIG. 4, base unit C0 transmits OFDM signals and phase modulation signals (carrier signals modulated by the phase modulation method) between slave units C11 to C14, C21 to C23, and C31 to C32. Both can be sent and received. Further, although the OFDM signal cannot be transmitted / received between the slave units C15 to C17, C24 to C26, and C33 to C35, the phase modulated signal can be transmitted / received. It is assumed that neither OFDM signals nor phase modulation signals can be transmitted / received between the other slave units C27 and C36 to C37.

  FIG. 1B is a diagram showing a network topology of the power line carrier communication system 1. As shown in the figure, in the present embodiment, as shown in the figure, in the present embodiment, the logical units directly connected to the parent device C0 are the child devices C11 to C14, C21 to C23, Only C31 to C32 (hereinafter collectively referred to as direct communication slaves). Among these, the child devices C14, C23, and C32 are used as repeaters (hereinafter collectively referred to as repeater child devices), and the distance from the parent device C0 on each power line is greater than that of the repeater child devices C15 to C17. , C24 to C27, C33 to C37 (hereinafter collectively referred to as repeater-connected communication slave units) are connected to the master unit C0 via slave units C14, C23, and C32 as repeaters.

  The reason why such a network topology is adopted is that, as shown in FIG. 4, the repeater-directed communication slave unit is too far away to perform direct communication with the master unit C0 by OFDM communication. Specifically, whether each slave unit is a direct communication slave unit or a communication slave unit via a repeater, and which slave unit is used as a repeater slave unit is automatically determined at the time of system startup by the process of the master unit C0. The Details of this process will be described later.

  FIG. 5A is a diagram showing functional blocks of the parent device C0. As shown in the figure, the base unit C0 has a modem 11 and a synchronization signal generator 12 connected to the power line, a control unit 13, a buffer 14, and an interface 15 connected to a personal computer as a terminal device. ing.

The modem 11 performs the second OFDM communications (specifically 115kHz or 132 kHz) the first frequency belonging to the frequency band _{F 1} is a modem for performing phase modulation communication using. OFDM communication is used for transmission / reception of instruction data and meter-reading data, and phase modulation communication is used for transmission of a calling signal to the repeater slave unit. Specifically, in accordance with an instruction from the control unit 13, phase modulation is performed at the carrier frequency of the _first frequency band F ₁ based on data stored in the buffer 14 or data input from the personal computer via the interface 15 and modulated. A predetermined preamble including a known synchronization signal corresponding to the method is added and transmitted to the power line. In addition, the synchronization signal added by the modem 11 is a wideband signal composed only of subcarriers belonging to the same frequency band as the carrier signal when the OFDM modulation method is used for modulating the carrier signal. On the other hand, when the phase modulation method is used for modulating the carrier signal, it is a single frequency signal having the same frequency as the carrier signal. The phase-modulated carrier wave signal in the first frequency band F ₁ flowing through the power line is received and demodulated, and the obtained data is output to the buffer 14 or the interface 15 in accordance with an instruction from the control unit 13.

  It should be noted that the OFDM signal is transmitted with its output adjusted so that the total output of each subcarrier is 100 mW. On the other hand, the phase modulation signal is transmitted with an output of 350 mW. The reason for this output is to comply with the laws and regulations shown in Table 1 above.

  In addition, the modem 11 is configured to use a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method when transmitting a signal. That is, the modem 11 attempts to receive the signal once before starting transmission (carrier sense), and transmits transmission data if a transmission signal from 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. Negotiation at the start of communication is not performed.

  The synchronization signal generator 12 monitors whether a known synchronization signal is included in the signal flowing through the power line. When it is detected that it is included, the synchronization is established using the synchronization signal, and information indicating that the synchronization is established is notified to the control unit 13. Upon receiving this notification, the control unit 13 causes the modem 11 to start demodulation processing.

  In addition to the processing described so far, the control unit 13 performs processing for controlling each unit of the parent device C0. In addition, the control unit 13 generates instruction data for instructing transmission of meter reading data according to an instruction from the personal computer, transmits the instruction data to each child device using the modem 11, and each child device according to the instruction data. The meter reading data returned from is received via the modem 11.

  The order in which the parent device C0 transmits the instruction data is programmed in advance. Details of this programming will be described later. The control unit 13 functionally includes a determination unit 16 (determination unit), a selection unit 17 (selection unit), and a switching unit 18 (switching unit). These processes will also be described later.

  The buffer 14 is a storage unit that stores data input from the modem 11 in accordance with instructions from the control unit 13. The interface 15 inputs and outputs data with a personal computer.

  FIG. 5B is a diagram showing functional blocks of the slave units C11 to C37. In this embodiment, all the slave units have the same functional block. As shown in FIG.5 (b), the subunit | mobile_unit C11-C37 is connected to the modem 21, the synchronous signal generator 23, the control part 24, the buffer 25, and the electric meter as a terminal device connected to a power line, respectively. Interface 26.

The modem 21 is a modem having a function of performing phase modulation communication using the frequency (specifically 115 kHz or 132 kHz) belonging to the first frequency band F ₁ while performing the first and second OFDM communications. is there. In the case of a repeater slave unit, phase modulation communication is used when receiving a calling signal from the master unit C0, and first OFDM communication is used when receiving a signal from a slave unit under the repeater slave unit. In addition, when transmitting instruction data and meter-reading data between the parent device C0 and the repeater child device or the direct communication child device, the second OFDM communication is used, and the instruction data is transmitted between the repeater child device and the subordinate child devices. The first OFDM communication is used when transmitting / receiving meter reading data.

The basic function of the modem 21, the first frequency band F ₁ also except using is similar to the function of the modem 11 described above. That is, the modem 21 performs the first frequency band F ₁ or the second frequency based on data stored in the buffer 25 or data input from a terminal device (not shown) via the interface 26 in accordance with an instruction from the control unit 24. The carrier signal of band F ₂ is modulated, and a predetermined preamble including a known synchronization signal corresponding to the modulation method is added, and then transmitted to the power line. Further, the modulated carrier wave signal of the first frequency band F ₁ or the second frequency band F ₂ flowing through the power line is received and demodulated, and the obtained data is output to the buffer 25 or the interface 26 according to the instruction of the control unit 24. To do. Note that the CSMA / CA method is used for signal transmission.

  The synchronization signal added by the modem 21 is a wideband signal composed only of subcarriers belonging to the same frequency band as the carrier signal when the OFDM modulation method is used for modulating the carrier signal. On the other hand, when the phase modulation method is used for modulating the carrier signal, it is a single frequency signal having the same frequency as the carrier signal.

  The modem 21 will be described in more detail. FIG. 6 is a diagram showing functional blocks of the modem 21. As shown in the figure, the modem 21 includes functional units such as a control unit 31, an interface (I / F) 32, a communication unit 33, a modulation unit 34, a transmission unit 35, a multiplexer 36, a reception unit 37, and a demodulation unit 38. Have.

  The control unit 31 acquires various types of information including signal transmission destination information from the control unit 24, and controls each unit of the modem 21 based on the acquired information.

  The interface 32 is an interface with higher-level devices such as the control unit 24 and the buffer 25, receives higher-layer data from the higher-level device, and outputs it to the communication unit 33. Also, the upper layer data is received from the communication unit 33 and is output to the upper device. The communication unit 33 is a functional unit that processes transmission / reception signals including a header, and is configured by, for example, a DSP (Digital Signal Processor). Specifically, the upper layer data to be transmitted is received from the interface 32, a header including pilot data and a destination MAC address, and redundant data for error correction are added, and the modulation unit 34 is transmitted as transmission data. To send. In addition, receiving data including a header and higher layer data is input from the demodulator 38, and processing and error correction processing corresponding to the header therein are performed, and output of higher layer data to the interface 32 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 33 is configured to return response data each time a signal is received from another power line carrier communication device. A signal including response data is referred to as a response signal. Therefore, when the communication unit 33 does not receive the response data within a predetermined time after transmitting the transmission data other than the response data, the communication unit 33 retransmits the transmission data as not being received normally. I do.

  The modulation unit 34 selects one modulation method from the OFDM modulation method and the phase modulation method in accordance with an instruction from the control unit 31. Then, using the selected modulation method, the carrier signal is modulated based on the transmission data, a predetermined preamble including a known synchronization signal corresponding to the modulation method is added, and the Radio Law Enforcement Rules shown in Table 1 Then, the signal amplitude is controlled in accordance with the communication method used for the modulation process in accordance with the regulation (carrier wave output), and then output to the transmitter 35.

Here, the control unit 31 controls the modulation scheme and frequency (subcarrier) used by the modulation unit 34 according to the transmission destination and content of the transmission signal. That is, in the repeater slave unit, when the transmission destination of the transmission signal is the base unit C0 and the transmission signal is a call signal or a response signal thereof, phase modulation is performed using a single subcarrier of 115 kHz or 132 kHz. The modulation unit 34 is controlled. Also, a destination base unit C0 of the transmission signal, and when the transmission signal is a signal including an instruction data and meter reading data, the OFDM modulation using only subcarriers belonging to the second frequency band F ₂ The modulation unit 34 is controlled to perform. Further, between the repeater slave unit and subordinate slave units, the modulation unit 34 is controlled to perform OFDM modulation using only the subcarriers belonging to the first frequency band F ₁ regardless of the content of the transmission signal.

  The transmission unit 35 has a function of converting the signal input from the modulation unit 34 into a signal that can be transmitted to the power line, and then transmitting the signal to the power line. Specifically, the digital signal input from the modulation unit 34 is converted into an analog signal, an unnecessary frequency band component is removed by using a band pass filter, and further amplified by a predetermined amplification factor. And send it to the power line.

  The receiving unit 37 has a function of receiving a signal arriving on the power line, converting it to a digital signal, and outputting the digital signal to the demodulating unit 38. Specifically, the signal received via the multiplexer 36 is amplified with a predetermined amplification factor, then sampled, converted into a digital signal, and output to the demodulator 38.

In addition, the reception unit 37 has a function of outputting a signal to the demodulation unit 38 while switching between the two communication modes. The two communication modes are an F ₁ mode that blocks signals of frequencies other than the _first frequency band F ₁ among the received signals, and an F ₂ mode that blocks signals other than the _second frequency band F ₂ of the received signals. There are two. Further details of each communication mode will be described later.

  The demodulator 38 has a function of demodulating the digital signal input from the receiver 37 using an OFDM modulation scheme and a phase modulation scheme. The demodulator 38 outputs a signal obtained by demodulation to the communication unit 33. Details of the demodulator 38 will also be described later.

  Returning to FIG. The function of the synchronization signal generator 23 is the same as the function of the synchronization signal generator 12 described above. The control unit 24 that has received notification of information indicating that synchronization has been established from the synchronization signal generator 23 causes the modem 21 to start demodulation processing.

  The control part 24 performs the process which controls each part of a subunit | mobile_unit besides the process mentioned so far. Further, when the instruction data (instruction data for instructing to transmit meter-reading data) addressed to the own device is received from the parent device C0 or the repeater child device, the control unit 24 sends an electric meter to the electric meter via the interface 26. Access to acquire meter reading data, and return the acquired meter reading data using the modem that has received the instruction data.

  Further, the control unit 24 stores whether or not the own device functions as a repeater that relays communication between the parent device C0 and other child devices. In the case of functioning as a repeater, information indicating the subordinate slave unit is also stored, and when the above instruction data addressed to the subordinate slave unit is received from the master unit C0, the instruction data is sent to the destination slave unit. Forward. And the meter-reading data returned from the subordinate subordinate in response to this transfer is transferred to the main unit C0.

  The buffer 25 is a storage unit that stores data input from the modem 21 in accordance with an instruction from the control unit 24. The interface 26 inputs and outputs data with the electric meter.

  Next, transmission / reception of instruction data and meter reading data performed between the parent device C0 and the child devices C11 to C37 will be described in detail.

As shown in FIG. 1 (a) (b), to communicate with the base unit C0 and the direct communication slave unit, a second using frequency band F _2. That is, each direct communication handset transmits / receives instruction data and meter reading data to / from the base unit C0 by the second OFDM communication. On the other hand, for communication with the repeater handset and the repeater via a communication slave unit, first using a frequency band F _1. That is, these slaves mutually transmit and receive instruction data and meter reading data by the first OFDM communication.

  Each diagram in FIG. 7 is a diagram illustrating a format of a signal transmitted / received between the parent device C0 and each child device or between the child devices. Note that these drawings only show portions related to layers higher than the network layer, and do not show portions related to layers lower than the network layer, such as synchronization signals. Hereinafter, transmission and reception of signals between the parent device C0 and each child device and between child devices will be described with reference to these drawings.

  First, FIG. 7A shows a signal format used when the parent device C0 transmits instruction data directly to a communication child device (excluding a repeater child device). Receiving the meter reading data acquisition instruction from the personal computer, the base unit C0 generates a signal including the instruction data, the address of the direct communication slave unit as the destination address, and the address of the own unit as the transmission source. It transmits on power line B1-B3 by OFDM communication. Each slave unit monitors the header of a signal flowing on the power line, and receives a signal when a signal to which the address of the slave unit is added flows.

  FIG. 7B shows a signal format used when a direct communication slave unit (excluding a repeater slave unit) transmits meter-reading data to the master unit C0. Each direct communication slave that has received the signal of FIG. 7A first acquires meter reading data from an electric meter. And the signal containing meter-reading data, the address of the main | base station C0 as a destination address, and the address of the own machine as a transmission source is produced | generated, and it sends out on a power line by 2nd OFDM communication. The base unit C0 monitors the header of the signal flowing on the power lines B1 to B3, and receives the signal when the signal with its own address added flows. With the above processing, the acquisition of meter reading data from the direct communication slave unit (excluding the repeater slave unit) is completed.

  Next, FIG. 7C shows a signal format used when the parent device C0 transmits instruction data to the repeater child device and the repeater child communication device. Base unit C0 generates a signal including the instruction data, the address of the repeater slave unit as the destination address, and the address of its own unit as the transmission source, and transmits the signal onto power lines B1 to B3 by the second OFDM communication. .

  FIG. 7D shows a signal format used when the repeater slave unit transfers instruction data to the subordinate repeater slave unit. The repeater slave unit rewrites the destination address and the transmission source address of the signal received from the master unit C0 with the address of the slave unit via the repeater and the address of the own unit, respectively, and sends it over the power line by the first OFDM communication.

  FIG. 7E shows a signal format used when the communication slave unit via repeater transmits meter reading data to the repeater slave unit. Each of the communication slave devices via repeaters that has received the signal of FIG. 7D first acquires meter reading data from an electric meter. Further, the destination address of meter reading data (that is, the address of the repeater slave unit) is acquired from the source address of the received signal. Then, a signal including the meter reading data, the address of the repeater slave as the destination address, and the address of the own device as the transmission source is generated, and is transmitted onto the power line by the first OFDM communication.

  FIG. 7F shows a signal format used when the repeater slave unit transmits meter reading data to the master unit C0. The repeater slave unit that has received the signal of FIG. 7C acquires meter reading data from the electric meter connected to the repeater unit and stores it in the buffer 25 (FIG. 5B). Also, meter reading data is acquired from the subordinate repeater communication slave unit by the signal shown in FIG. 7E, and stored in the buffer 25 (FIG. 5B). Then, when the repeater slave unit completes the acquisition of all the meter reading data, it generates a signal including the accumulated meter reading data, the address of the parent device C0 as the destination address, and the address of the own device as the transmission source. Then, it is transmitted on the power line by the second OFDM communication. By receiving this signal, the master unit C0 completes the acquisition of meter reading data from the repeater slave unit and the repeater slave unit.

  The transmission / reception of signals performed between the parent device C0 and each child device and between the child devices has been described above. Next, a specific procedure of this signal transmission / reception will be described.

  FIG. 8 is a schematic diagram showing communication steps between the parent device C0 and each child device and between child devices. Arrows in the figure indicate transmission and reception of signals a to f. Signals a to f correspond to FIGS. 7 (a) to 7 (f). In the following description, the order in which the base unit C0 transmits signals is programmed in advance so that the total number of communication steps is minimized in consideration of the number of slave units.

  First, simultaneous transmission / reception of signals will be described. Since the second OFDM communication is used for transmitting and receiving the signals a to c and f, and the first OFDM communication is used for transmitting and receiving the signals d and e, the signals a to c and f and the signals d and e Can simultaneously transmit and receive on the power lines B1 to B3. In addition, the signals transmitted and received between each repeater slave unit and its subordinate repeater slave units are sufficiently separated from each other, so that other repeater slave units and its subordinate repeater slave units are also separated. Does not interfere with signals transmitted and received between the two. Therefore, transmission / reception of signals between each repeater slave unit and a repeater-directed communication slave unit under the repeater slave unit can be performed simultaneously and independently on each power line. The above programming in the parent device C0 is performed in consideration of these.

  As shown in FIG. 8, base unit C0 first transmits signal c (signal including instruction data) with three repeater slave units C32, C23, and C14 as destinations in sequence (steps 1 to 3). This transmission is performed by the second OFDM communication.

  As soon as each of the repeater slaves C32, C23, C14 receives the signal c from the master device C0, each repeater slave C32, C23, C14 receives a signal d (a signal including instruction data) as a first address with one of the subordinate repeater communication slaves as the destination Transmission is performed by OFDM communication (steps 2 to 4). Upon receiving the signal d, the repeater communication slave unit immediately acquires meter reading data, and returns a signal e (a signal including meter reading data) to the repeater slave unit by the first OFDM communication (steps 3 to 5). Each repeater slave C32, C23, C14 stores the meter reading data included in the signal e thus received in the buffer 25. Each of the repeater slave units C32, C23, C14 repeats the above processing for all of the subordinate repeater communication slave units (steps 2 to 11 for the repeater slave unit C32, and steps 3 to 10 for the repeater slave unit C23. Step 4-9 for machine C14). When the meter reading data of all of the subordinate repeater communicating slaves is accumulated, a signal f including the meter reading data of the own device is generated and transmitted to the parent device C0 by the second OFDM communication (steps 10 to 10). 12).

  In the present embodiment, since there are five, four, and three repeater-connected communication slave units under each of the repeater slave units C32, C23, and C14, the master unit C0 transmits the signal c to the repeater slave unit C14. In step 10, which is 7 steps after step 3, the repeater child device C14 first transmits the signal f to the parent device C0 by the second OFDM communication. Next, in steps 11 and 12, the repeater slave units C23 and C32 sequentially transmit the signal f to the master unit C0 by the second OFDM communication.

  While the repeater slave unit performs the above processing in steps 4 to 9, the master unit C0 transmits / receives signals a and b to / from the direct communication slave units C11 to C13 by the second OFDM communication. Acquire meter reading data from the machine. In step 13 and subsequent steps, base unit C0 transmits and receives signals a and b to and from the remaining direct communication slave units C21, C22, and C31 by second OFDM communication, and reads meter reading data from these slave units. get. Finally, when step 18 is completed, the acquisition of meter reading data from all the slave units is completed.

  As described above, since the power line carrier communication system 1 uses two non-overlapping frequency bands, the first and second frequency bands, the repeater slave unit performs OFDM communication with the repeater-directed communication slave unit. The master unit can perform OFDM communication with other slave units. Therefore, the total number of communication steps is reduced as compared with the background art shown in FIG.

  From here, a specific configuration for allowing the repeater slave unit to perform both the first and second OFDM communications by one OFDM modem and improving the demodulation accuracy of the call signal of the repeater slave unit will be described. .

  First, the internal configuration of the demodulator 38 in the modem 21 will be described.

FIG. 9 is a diagram illustrating an internal configuration of the demodulation unit 38. As shown in the figure, the function of the demodulation unit 38 is divided into a synchronization detection unit 39 and a demodulation processing unit 40, and the synchronization detection unit 39 detects F ₁ synchronization detection corresponding to the OFDM signal in the _first frequency band F _1. Unit 70, F ₂ synchronization detection unit 71 corresponding to the OFDM signal of the second frequency band F ₂ , 115 kHz synchronization detection unit 72 corresponding to the phase modulation signal of 115 kHz, and 132 kHz synchronization detection unit corresponding to the phase modulation signal of 132 kHz 73.

The demodulation processing unit 40 includes a switch 80 and an F ₁ demodulation processing unit 81 (first OFDM signal demodulation unit) connected in series to the F ₁ synchronization detection unit 70, and a switch 82 connected in series to the F ₂ synchronization detection unit 71. And F ₂ demodulation processor 83 (second OFDM signal demodulator), switch 84 and 115 kHz demodulation processor 85 (phase modulation signal demodulator) connected in series to 115 kHz synchronization detector 72, and 132 kHz synchronization detector 73 in series. The switch 86 and the 132 kHz demodulation processor 87 (phase modulation signal demodulator) are connected to each other. Note that the F ₁ demodulation processing unit 81 has a function of demodulating the OFDM signal of the first frequency band F ₁ , and the F ₂ demodulation processing unit 83 has a function of demodulating the OFDM signal of the second frequency band F _2. The 115 kHz demodulation processing unit 85 has a function of demodulating the 115 kHz phase modulation signal, and the 132 kHz demodulation processing unit 87 has a function of demodulating the 132 kHz phase modulation signal.

  Each synchronization detection unit in the synchronization detection unit 39 holds a synchronization pattern for the corresponding signal. Each synchronization detection unit constantly calculates a correlation value between the received signal input from the reception unit 37 and the held synchronization pattern, and responds when the calculated correlation value exceeds a predetermined value. Detects synchronization with the signal and performs synchronization establishment processing.

When synchronization is detected by any of the synchronization detection units, the control unit 31 turns on the switch connected to the synchronization detection unit that detected the synchronization and starts demodulation to the corresponding demodulation unit. Let That is, when the F ₁ synchronization detection unit 70 detects synchronization, the switch 80 is turned on, and the F ₁ demodulation processing unit 81 starts demodulation using the OFDM modulation scheme. When the F ₂ synchronization detection unit 71 detects synchronization, the switch 82 is turned on, and the F ₂ demodulation processing unit 83 starts demodulation by the OFDM modulation method. When the 115 kHz synchronization detection unit 72 detects synchronization, the switch 84 is turned on, and the 115 kHz demodulation processing unit 85 starts demodulation by the phase modulation method. When the 132 kHz synchronization detection unit 73 detects synchronization, the switch 86 is turned on, and the 132 kHz demodulation processing unit 87 starts demodulation by the phase modulation method.

  Each demodulation processing unit in the demodulation processing unit 40 outputs a signal obtained by the demodulation to the communication unit 33.

Next, the receiving unit 37 will be described. As described above, the receiving unit 37 has two communication modes, the F ₁ mode and the F ₂ mode. When each of the slave units in the power line carrier communication system 1 performs communication using one of the first and second frequency bands F ₁ and F ₂ by switching these communication modes, interference occurs. The other frequency band that causes noise is cut off. Below, the internal structure of the receiving part 37 is demonstrated first, and the control for communication mode implementation | achievement by the control part 31 is demonstrated after that.

  FIG. 10 is a diagram illustrating an internal configuration of the receiving unit 37. As shown in the figure, the receiving unit 37 includes first and second signal paths 41 and 42, a low noise amplifier (LNA) 49, and an automatic gain control unit (AGC) 50. In the figure, a conversion unit for converting an analog signal into a digital signal is omitted.

The first signal path 41 is a functional unit that is installed between the power line and the demodulator 38 and blocks signals of frequencies other than the _first frequency band F ₁ . Specifically, it has a band-pass filter 45 that extracts and passes only frequency components belonging to the first frequency band F ₁ from the signal input from the multiplexer 36. The first signal path 41 is provided with first switch means 44. The first switch means 44 is opened and closed under the control of the control unit 31.

The second signal path 42 is a functional unit that is installed between the power line and the demodulator 38 and blocks signals of frequencies other than the _second frequency band F2. Specifically, it has a band pass filter 47 that extracts and passes only frequency components belonging to the second frequency band F ₂ from the signal input from the multiplexer 36. The second signal path 42 is provided with second switch means 46. The second switch means 46 is also opened and closed under the control of the control unit 31.

  The low noise amplifier 49 amplifies the signals output from the first and second signal paths 41 and 42 with a predetermined amplification factor, and outputs the amplified signal to the automatic gain control unit 50. The automatic gain control unit 50 has a built-in amplification circuit, and controls the amplification factor of the amplification circuit based on the feedback signal from the demodulation unit 38 so that the amplitude of the signal input to the demodulation unit 38 becomes a constant value. .

Now, communication mode control of the receiving unit 37 by the control unit 31 will be described. Control unit 31, according to Table 2 below, by controlling the first and second switching means 44,46, _{F 1} mode, to realize the two communication modes _{F 2} mode.

If the repeater slave unit waits for the call signal, the control unit 31 turns on the first switching means 44, by the second switching means 46 are turned off, is referred to as F ₁ mode communication mode of the receiver 37. In the F ₁ mode, only frequency components belonging to the first frequency band F ₁ are input to the demodulator 38, so that not only the calling signal of the first frequency band F ₁ but also a phase modulated signal of 115 kHz or 132 kHz. A certain call signal can also be suitably received.

When the repeater slave unit or the direct communication slave unit transmits / receives instruction data or meter-reading data to / from the master unit C0, the control unit 31 turns off the first switch unit 44 and turns off the second switch unit 46. by turning on, the communication mode of the reception unit 37 and the F ₂ mode. Since the F ₂ mode so that only the frequency components belonging to the second frequency band F ₂ is input to the demodulation unit 38, so that can communicate with the master unit C0 according to the second OFDM communication suitably.

When transmitting / receiving instruction data and meter reading data between the repeater slave unit and the repeater subordinate slave unit, the control unit 31 turns on the first switch unit 44 and turns off the second switch unit 46. in, the communication mode of the reception unit 37 and the _{F 1} mode. In the F ₁ mode, only frequency components belonging to the first frequency band F ₁ are input to the demodulator 38, so that communication with other slave units by the first OFDM communication can be performed suitably.

  Next, referring to the sequence of communication performed between the parent device C0, the child device C21 (direct communication child device), the child device C32 (repeater child device), and the child device C37 (communication child device via repeater) as an example. The processing of the control unit 31 will be described in further detail.

  FIG. 11A shows the above sequence. The figure shows a sequence in which the parent device C0 acquires meter-reading data from the child devices C21 and C37. In the figure, sequences of layers below the network layer are displayed. Therefore, unlike FIG. 8, the above-described response signal (indicated as “ACK” in FIG. 11) also appears in the figure.

  FIG. 11B shows the frequency band of each signal shown in FIG. 11A and the communication mode setting of the receiving unit 37 of the repeater slave C32 (denoted as “repeater setting” in the figure). The horizontal axis in FIG. 11B is a time axis.

  First, the sequence shown in FIG. 11A will be described. As shown in the figure, base unit C0 transmits a calling signal to the repeater (step S1). The child device C32 that has received the call signal transmits ACK to the parent device C0 (step S2).

  When receiving the ACK, the parent device C0 transmits a signal c (FIG. 7) for requesting the data of the child device C37 to the child device C32 (step S3). The slave unit C32 also transmits an ACK to the master unit C0 for this signal c (step S4). The subunit | mobile_unit C32 produces | generates the signal d based on the received signal c, and transmits to the subunit | mobile_unit C37 (step S5). The slave unit C37 returns a signal e including meter reading data (step S6), and the slave unit C32 generates a signal f based on the received signal e and transmits it to the master unit C0 (step S7). When receiving the signal f, the parent device C0 transmits ACK to the child device C32 (step S8).

Next, with reference to FIG.11 (b), the communication mode setting of the receiving part 37 of the repeater subunit | mobile_unit C32 is demonstrated. As shown in the figure, until transmits the ACK at Step S2, the control unit 31 of repeater handset C32 sets the receiver 37 to the F ₁ mode. This is to wait for calls from both the parent device C0 and other child devices. On the other hand, after the transmission of the ACK in step S2, the control unit 31 sets the reception unit 37 to the _{F 2} mode, the communication step S3~S4 by a second OFDM communications using the second frequency band _{F 2} I do. When performing the transmission of the signal d in the step S5, the control unit 31 sets the reception unit 37 in _{F 1} mode, the first OFDM communications using the first frequency band _{F 1} communication steps S5~S6 Do. When performing the transmission of the signal f in step S7, the control unit 31 returns the receiver 37 to the _{F 2} mode, the communication step S7~S8 by a second OFDM communications using the second frequency band _{F 2} I do. When receiving the ACK in step S8 is completed, the control unit 31 returns the receiver 37 to the F ₁ mode, resumes waiting for call signals.

Incidentally, as shown in FIG. 11 (a) (b), while the the handset C32 and the slave device C37 are communicating, the master unit C0 is the use of the second frequency band _{F 2} 1 The meter reading data is acquired from the handset C21 by the OFDM communication (steps S9 to S10). As described above, the reason why the master unit C0 communicates directly with the communication slave unit while the repeater slave unit communicates with the communication slave unit via the repeater is to reduce the total number of communication steps as described above.

As described above, according to the power line carrier communication system 1, even if the repeater slave has only one OFDM modem including the receiving unit 37 and the demodulating unit 38, the first frequency band F ₁ It is possible to perform both of the OFDM communication with the slave unit at the standby time and the subordinate subordinate unit using the signal of 1 and the OFDM communication with the base unit using the signal of the _second frequency band F2.

Further, since base unit C0 transmits a call signal by phase modulation communication, it is possible to transmit the call signal with a high output of 350 mW as shown in Table 1. Further, since the repeater slave unit only has to wait for a call signal in the _first frequency band F1, it is not necessary to wait for a signal in the _second frequency band F2 that causes interference noise. As a result, the demodulation accuracy of the call signal of the repeater slave unit is improved.

Further, according to the power line communication system 1, it is possible to generate either a call signal of a first frequency band F ₁ OFDM signal and the first frequency of the phase modulation signal belonging to the frequency band F _1. Therefore, it is possible to unify the calling signal from the parent device C0 and the subordinate child devices to the repeater child device into a signal of the first frequency band. That is, base unit C0 transmits a call signal using a phase-modulated signal having a frequency belonging to _first frequency band F1, and the other handset transmits a call signal using an OFDM signal in _first frequency band F1. enabling, since only the first signal frequency band F ₁ is input to the demodulator, the interference noise will be reduced, thereby improving the demodulation accuracy of the paging signal.

Finally, the processing of the master unit for determining whether each slave unit is a direct communication slave unit or a repeater slave unit and which slave unit is used as a repeater slave unit will be described. To do. Below, it demonstrates on the assumption of the power line carrier communication system 1 shown in FIG. This process is preferably performed when the power line carrier communication system 1 is started up. In the initial state, address information of the slave units C11 to C37 is set in advance in the master unit C0. Further, both the first and second switch means 44 and 46 in the receiving unit 37 of each slave unit are on. That is, each handset can receive both the first and second frequency bands F ₁ and F ₂ .

  As shown in FIG. 5A, the parent device C0 includes a determination unit 16, a selection unit 17, and a switching unit 18. Among these, the determination unit 16 first determines for each slave unit whether or not direct communication is possible by OFDM communication. Next, the selection unit 17 selects a slave unit that functions as a repeater from the slave units that the determination unit 16 determines to be able to communicate directly by OFDM communication, and stores the selected slave unit as a repeater slave unit. And the switching part 18 switches communication with the subunit | mobile_unit which the determination part 16 determined to be unable to communicate directly by OFDM communication to communication via a repeater subunit | mobile_unit. That is, these slave units are stored as communication slave units via repeaters, and the repeater slave units are instructed to function as repeaters. Upon receiving this command, the repeater slave unit switches the communication with the subordinate repeater slave unit to the first OFDM communication.

  Hereinafter, a specific processing procedure of base unit C0 will be described in detail.

  FIG. 12 shows a processing procedure regarding each of the slave units C21 to C27 connected to the power line B2. Hereinafter, the processing of the parent device C0 will be described in detail with reference to FIG. 12, but the processing is performed in the same procedure for each of the child devices connected to the power lines B1 and B3.

  As shown in FIG. 12, first, the determination unit 16 unicasts a communication quality confirmation signal g to the child device C21 (step 1).

  FIG. 13 shows the format of the signal g. As shown in the figure, the signal g for communication quality confirmation includes three parts: a part transmitted by the second OFDM communication, a part transmitted by the 115 kHz phase modulation communication, and a part transmitted by the 132 kHz phase modulation communication. It consists of two partial signals. Each partial signal includes a preamble and unicast data, and is used to modulate a carrier signal by a corresponding modulation scheme. The preamble includes the address of the destination slave unit, and the unicast data includes predetermined data indicating that the signal is a communication quality confirmation signal.

Base unit C0 sequentially sends the partial signals of signal g to power lines B1 to B3. FIG. 14 is a diagram showing the time change of the frequency of the signal g transmitted in this way. As shown in the figure, when the transmission of the signal g is seen by the time change of the frequency, a wideband signal extending over the entire _second frequency band F2 is transmitted first, followed by a single frequency signal using only 115 kHz. Finally, a single frequency signal using only 132 kHz will be transmitted.

  Returning to FIG. The subunit | mobile_unit C21 will measure the reception quality for every partial signal, if at least one part of the signal g is received. The reception quality includes a reception level, a signal-to-noise ratio (SNR), the number of bit errors, the number of frame errors, and the like.

  The subunit | mobile_unit C21 can transmit / receive both an OFDM signal and a phase modulation signal between the main | base stations C0, as shown in FIG. Accordingly, the slave unit C21 receives all three partial signals of the signal g, generates a signal h including information indicating that all the partial signals have been received and information indicating the reception quality of each partial signal. Transmit to the machine C0 by the second OFDM communication (step 2).

  Next, the determination part 16 transmits the signal g for communication quality confirmation toward the subunit | mobile_unit C22 (step 3). The child device C22 also generates the signal h in the same manner as the child device C21 and transmits the signal h to the parent device C0 by the second OFDM communication (step 4). The same applies to the child device C23 (steps 5 to 6).

  Next, the determination part 16 transmits the signal g for communication quality confirmation toward the subunit | mobile_unit C24 (step 7). As shown in FIG. 4, slave C21 can only transmit and receive phase-modulated signals to and from master C0 and cannot transmit and receive OFDM signals. Accordingly, the slave unit C24 receives only the partial signal transmitted by the phase modulation communication among the three partial signals of the signal g, and information indicating that only the partial signal transmitted by the phase modulation communication is received; A signal h ′ including information indicating the reception quality of these partial signals is generated and transmitted to the parent device C0 by phase modulation communication (step 8). The same applies to the slave units C25 to C26 (steps 9 to 12).

  Next, the determination part 16 transmits the signal g for communication quality confirmation toward the subunit | mobile_unit C27 (step 13). As shown in FIG. 4, handset C27 cannot transmit / receive either an OFDM signal or a phase modulation signal to / from base unit C0. Accordingly, the slave unit C27 cannot receive the signal g and does not transmit anything to the master unit C0 (step 14). The determination unit 16 determines that direct communication with the child device C27 cannot be performed by OFDM communication because the signal from the child device C27 is not received at a predetermined timing.

  Through the above processing, the determination unit 16 determines that the slave units C21 to C23 are slave units that can directly communicate by OFDM communication, and determines that the slave units C24 to C27 are slave units that cannot directly communicate by OFDM communication.

  When the processing of the determination unit 16 described above is completed and there is even one slave unit that cannot communicate directly by OFDM communication, the selection unit 17 first selects a repeater slave unit candidate. Specifically, a predetermined number of slave units are selected as repeater slave unit candidates in descending order of communication quality from among the slave units C21 to C23 determined by the determination unit 16 to be able to communicate directly by OFDM communication. The reason why the communication quality is low is that the lower the communication quality with the base unit C0, the closer to the handset that cannot communicate directly. Here, assuming that the predetermined number is two, slave units C22 and C23 are selected as repeater slave unit candidates.

  The selection unit 17 transmits an instruction signal i for instructing the child device C22, which is one of the selected repeater child device candidates, to confirm the existence of the child devices C24 to C27 (step 15). When receiving the command signal i, the control unit 24 (FIG. 5B) of the child device C22 receives a signal g for communication quality confirmation toward the child devices C24 to C27, similarly to the processing of the determination unit 16 described above. Are sequentially transmitted by the first OFDM communication, and a response signal (signal h or signal h ′) from each slave unit is stored in the buffer 25 (steps 16 to 23). When the processing for all the slave units is completed, a signal j including each response signal stored in the buffer 25 is generated and transmitted to the master unit C0 by the second OFDM communication (step 24).

  The selection unit 17 also causes the child device C23, which is another one of the selected repeater child device candidates, to check the presence of the child devices C24 to C27 in the same manner as the child device C22 (steps 25 to 34). ).

  Based on signal j received from each repeater child device candidate C22, C23, selection unit 17 determines which of the child devices has a better communication state with child devices C24 to C27. And the subunit | mobile_unit determined to be more favorable is selected as a repeater subunit | mobile_unit. In the example of FIG. 1, since the child device C23 is closer to the child devices C24 to C27, the child device C23 is selected as the repeater child device.

  When the selection unit 17 selects the repeater slave unit, the switching unit 18 transmits a command signal k for instructing the repeater slave unit C23 to function as a repeater by the second OFDM communication (step 35). ). This command signal k includes information indicating the slave units C24 to C27 that are subordinate communication slave units.

When receiving the command signal k, the control unit 24 (FIG. 5B) of the repeater child device C23 stores that the own device becomes a repeater child device, starts an operation as a repeater, and operates a subordinate repeater. Next, a command signal l for instructing to perform communication by the first OFDM communication is transmitted to the relay communication slave devices C24 to C27. Controller 24 of the repeater via the communication handset C24~C27 receives this command signal l, the receiving unit 37 starts the standby signal from the slave unit C23 as F ₁ mode, a predetermined response signal m It returns with repeater cordless handset C23 by 1st OFDM communication (steps 36-43).

When the repeater slave C23 completes the reception of the response signal m for all of the slaves C24 to C27, the repeater slave C23 transmits a signal n for network construction completion notification to the master C0 by the second OFDM communication (step 44). ). Receiving this signal n, the parent device C0 recognizes that the child device C23 has started to function as a repeater, and starts an operation mode in which the child device C23 is used as a repeater. Specifically, when acquiring meter reading data, instruction data is not sent to the slave units C24 to C27, and the meter reading data of the slave units C24 to C27 is received from the repeater slave unit C23. Incidentally, the slave unit C23, after transmitting the signal n, enters a standby state of receiver 37 as F ₁ mode.

  As described above, according to the power line carrier communication system 1, direct communication slaves that communicate directly with repeater slaves that communicate via repeater slaves are classified without human intervention after system construction. It becomes possible. Further, base unit C0 can appropriately select a repeater slave unit.

  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.

DESCRIPTION OF SYMBOLS 1 Power line carrier communication system 11, 21 Modem 12, 23 Synchronization signal generator 13, 24, 31 Control part 14, 25 Buffer 15, 26, 32 Interface 16 Determination part 17 Selection part 18 Switching part 33 Communication part 34 Modulation part 35 Transmission Unit 36 multiplexer 37 reception unit 38 demodulation unit 39 synchronization detection unit 40 demodulation processing unit 41 first signal path 42 second signal path 44 first switch means 45, 47 bandpass filter 46 second switch means 49 low noise amplifier 50 automatic gain control unit 70 F ₁ synchronization detection unit 71 F ₂ synchronization detection unit 72 115 kHz synchronization detection unit 73 132 kHz synchronization detection unit 80, 82, 84, 86 switch 81 F ₁ demodulation processing unit 83 F ₂ demodulation processing unit 85 115 kHz demodulation Processing unit 87 132 kHz demodulation processing unit B1-B3 Power line C0 Base unit C 1~C17, C21~C27, C31~C37 child machine

Claims (3)

A power line carrier communication device functioning as one of the slave units connected by bus to the power line connected to the master unit,
A receiver for receiving a signal flowing in the power line;
A demodulator that demodulates the received signal of the receiver;
A control unit,
The receiver is
A first signal path that is installed between the power line and the demodulator and blocks a signal having a frequency other than the first frequency band;
A second signal path that is installed between the power line and the demodulator and blocks a signal of a frequency other than the second frequency band that does not overlap with the first frequency band;
First switch means provided in the first signal path;
Second switch means provided in the second signal path,
The control unit turns on the first switch means and turns off the second switch means when waiting for the repeater slave unit to operate and when communicating with other slave units, and communicating with the master unit. When performing, the first switch means is turned off, the second switch means is turned on ,
The demodulator
A first OFDM signal demodulation processing unit for demodulating the OFDM signal of the first frequency band;
A second OFDM signal demodulation processing unit for demodulating the OFDM signal of the second frequency band;
A phase modulation signal demodulation processing unit for demodulating a phase modulation signal of a frequency belonging to the first frequency band;
The power line carrier communication apparatus , wherein the call signal is demodulated using the phase modulation signal demodulation processing unit . The demodulator
A first OFDM signal synchronization detecting means provided between the first OFDM signal demodulation processing unit and the receiving unit for detecting the synchronization of the OFDM signal of the first frequency band;
A second OFDM signal synchronization detecting means provided between the second OFDM signal demodulation processing unit and the receiving unit for detecting the synchronization of the OFDM signal of the second frequency band;
Phase modulation signal synchronization detection means provided between the phase modulation signal demodulation processing unit and the reception unit, for detecting synchronization of a phase modulation signal of a frequency belonging to the first frequency band;
The first OFDM signal demodulation processing unit starts demodulation in response to synchronization detected by the first OFDM signal synchronization detection means,
The second OFDM signal demodulation processing unit starts demodulation in response to synchronization detected by the second OFDM signal synchronization detection means,
The power line carrier communication apparatus according to claim 1, wherein the phase modulation signal demodulation processing unit starts demodulation in response to synchronization detected by the phase modulation signal synchronization detection means. A main unit and a power line connected to the main unit, each of the power line is bus-connected with a plurality of slave units each having a repeater function,
Communication between the child devices of the repeater child device and the child devices under the repeater child device is performed by first OFDM communication using the first frequency band, and direct communication between the parent device and the direct communication child device and the repeater child device. Is a power line carrier communication system performed by second OFDM communication using a second frequency band that does not overlap with the first frequency band,
A power line carrier communication system, wherein a calling signal when the parent device calls a repeater child device is transmitted by phase modulation communication using a frequency belonging to the first frequency band.

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