JP2007174456A - Communication jamming method and apparatus thereof, and propagation direction determining method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To jam communication of an unidentified PLC modem. <P>SOLUTION: A communication jamming device 30 is connected to two power source outlets 14a, 14b nearest to a connector of a branch power line 14 to a high-order power line 10. Power source plugs 32, 36 are connected to the outlets 14a, 14b, respectively. A PLC communication detector 34 detects the PLC communication signal of the outlet 14a, and a PLC communication detector 38 detects the PLC communication signal of the outlet 14b. A differential amplifier 40 output a signal indicating a difference in output between the apparatuses 34 and 38. A direction determining apparatus 42 determines whether the PLC communication signal on the power line 14 is in an upward direction from the output of the differential amplifier 40. If it is in the upward direction, the apparatus 42 applies an activation signal for generating a jamming signal to a jamming signal generating apparatus 44. The apparatus 44 generates a jamming signal of a predetermined period in accordance with the activation signal, and applies it to the power line 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication disturbance method and apparatus for blocking communication of an unapproved power line communication (PLC) modem, and a propagation direction determination method and apparatus therefor.

  In the PLC network, the communication signal propagates in two directions while being attenuated on the power line, and it is difficult to regulate the propagation direction.

  Since a power line communication (PLC) modem can communicate by connecting to a power line, it is often not noticed even if a PLC modem is connected to an outsider. There is a possibility that confidential information in the house will be transmitted to the outside by power line communication.

  In addition, even when the PLC-LAN is built in a home, communication data may be intercepted and transmitted to the outside. To prevent this, a certain authentication process is incorporated in the PLC modem in the PLC-LAN, and each PLC modem is managed so as to communicate only with the authenticated PLC modem.

  It is necessary to prevent data leakage by a power line communication modem connected without knowing in the house. If a PLC modem is detected when the PLC modem is connected to a power line to which a regular PLC modem is not connected, data leakage can be easily prevented and communication can be interrupted.

  An object of the present invention is to provide a communication disturbing method and apparatus for disturbing communication of an unapproved power line communication (PLC) modem, and a propagation direction determining method and apparatus therefor.

  The communication interference method according to the present invention includes a first power line communication detection step of detecting a power line communication signal at a first point on the power line, and a second point away from the first point on the power line. A second power line communication detecting step for detecting the power line communication signal, and a direction determining step for determining whether or not the propagation direction of the power line communication signal is a predetermined direction from the detection outputs of the first and second power line communication detecting steps. And an interference signal generating step of applying an interference signal for a certain period to the power line when the propagation direction of the power line communication signal is the predetermined direction.

  The communication jamming apparatus according to the present invention includes a first power line communication detection device that detects a power line communication signal at a first point on the power line, and a second point that is separated from the first point on the power line. According to the output of the second power line communication detection device that detects the power line communication signal, the delay determination device that determines the delay direction of the detection output of the first and second power line communication detection devices, and the output of the delay determination device, According to the output of the direction discriminating device that discriminates whether or not the propagation direction of the power line communication signal is a predetermined direction, and the output of the direction discriminating device when the propagation direction of the power line communication signal is the predetermined direction, And an interference signal generating device applied to the device.

  The propagation direction discriminating method according to the present invention is a method for discriminating the propagation direction of a power line communication signal propagating on a power line, and first power line communication for detecting the power line communication signal at a first point on the power line. A detection step, a second power line communication detection step for detecting the power line communication signal at a second point distant from the first point on the power line, and the first and second power line communication detection steps. And a direction determining step for determining whether or not the propagation direction of the power line communication signal is a predetermined direction from the detected output.

  A propagation direction discriminating apparatus according to the present invention is an apparatus that discriminates a propagation direction of a power line communication signal propagating on a power line, and detects a power line communication signal at a first point on the power line. A second power line communication detection device that detects the power line communication signal at a second point that is distant from the first point on the power line, and detection outputs of the first and second power line communication detection devices And a direction discriminating device for discriminating the propagation direction of the power line communication signal according to the output of the delay discriminating device.

  ADVANTAGE OF THE INVENTION According to this invention, the power line communication by the power line communication modem connected to the power line which should not be connected to a power line communication modem can be disturbed, and information leakage can be prevented.

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

  FIG. 1 shows a schematic block diagram of a communication jamming apparatus according to an embodiment of the present invention.

  A plurality of branch power lines 12, 14, and 16 are connected to the power line 10 serving as a trunk line. It is assumed that the authorized PLC modems 18 and 20 are connected to the branch power lines 12 and 16, but the connection of the PLC modem is not authorized to the power line 14. That is, the PLC modem 22 connected to the power outlet 14c of the power line 14 is an unauthorized unauthorized connection.

  In this embodiment, the communication jamming device 30 is connected to the two power outlets 14a and 14b closest to the connection portion of the branch power line 14 that is not authorized to connect the PLC modem to the higher power line (here, the main power line 10). To do.

  The power plug 32 of the communication jamming device 30 is connected to the outlet 14a, and the power plug 36 is connected to the outlet 14b. The PLC communication detection device 34 detects a PLC communication signal at the outlet 14 a via the power plug 32, and the PLC communication detection device 38 detects a PLC communication signal at the outlet 14 b via the power plug 36. The PLC communication detection devices 34 and 36 output a low (L) PLC communication signal in a state where no PLC communication signal is detected, and output a high (H) PLC communication detection signal while detecting the PLC communication signal. The PLC communication detection devices 34 and 38 having such functions can be realized by using, for example, a spectrum measurement device or the like that monitors power in a wavelength band used in the PLC.

  The output of the PLC communication detection device 34 is input to the positive input terminal of the differential amplifier 40, and the output of the PLC communication detection device 38 is input to the negative input terminal of the differential amplifier 40. As a result, the differential amplifier 40 outputs a signal indicating the difference between the outputs of the PLC communication detection devices 34 and 38.

  When a PLC communication signal is present on the power line 14, a delay corresponding to the transmission distance between the power outlets 14a and 14b occurs between the outputs of the PLC communication detection devices 34 and 38. Which is delayed depends on which direction the PLC communication signal propagates on the power line 14. The differential amplifier 40 functions as a delay determination device that determines the delay direction between the detection outputs of the PLC communication detection devices 34 and 38.

  FIG. 2 shows a timing chart when the PLC communication signal propagates on the power line 14 in the direction from the outlet 14b to the outlet 14a. This is a state in which the PLC modem 22 is outputting a PLC communication signal. Hereinafter, this direction is a direction toward a distribution board (not shown), and is hereinafter referred to as an upward direction.

  2A shows the output waveform 50 of the PLC communication detection device 34, and FIG. 2B shows the output waveform 52 of the PLC communication detection device 38. FIG. 2C shows output waveforms 54 and 56 of the differential amplifier 40. In the case of the PLC communication signal in the upward direction, the output of the PLC communication detection device 34 becomes H after the output of the PLC communication detection device 38 becomes H, so that the differential amplifier 40 firstly sets the negative pulse 54 And a positive pulse 56 is output at the end of PLC communication. Even in the PLC, since a signal is output as a packet of a certain volume, the positive pulse 56 is delayed from the negative pulse 54 by a time corresponding to the packet length.

  On the other hand, FIG. 3 shows a timing chart when the PLC communication signal propagates on the power line 14 in the direction from the outlet 14a to the outlet 14b. This is a state in which the PLC modem 18 or 20 connected to the other branch power lines 12 and 16 outputs a PLC communication signal. Hereinafter, this direction is referred to as a downward direction.

  FIG. 3A shows an output waveform 60 of the PLC communication detection device 34, and FIG. 3B shows an output waveform 62 of the PLC communication detection device 38. FIG. 3C shows output waveforms 64 and 66 of the differential amplifier 40. In the case of a PLC communication signal in the downstream direction, the output of the PLC communication detection device 38 becomes H after the output of the PLC communication detection device 34 becomes H, so that the differential amplifier 40 firstly sets the positive pulse 64 And a negative pulse 66 is output at the end of PLC communication.

  When the positive pulse 56 is input within a predetermined period following the negative pulse 54 from the output of the differential amplifier 40, the direction determination circuit 42 determines that the propagation direction of the PLC communication signal is the upward direction, and the positive pulse When a negative pulse 66 is input within a predetermined period following 64, it can be determined that the propagation direction of the PLC communication signal is the downlink direction.

  The final purpose of this embodiment is to connect the PLC modem 22 downstream of the branch power line 14 and to prevent the PLC modem 22 from outputting a PLC communication signal. Good. When the direction discriminating device 42 determines that the propagation direction of the PLC communication signal is the upward direction, the direction discriminating device 42 applies an activation signal for generating the interference signal to the interference signal generating device 44. The interference signal generator 44 generates an interference signal 58 (FIG. 2 (d)) for a certain period of time in accordance with the activation signal from the direction determination device 42. The disturbance signal 58 is applied from the power plug 36 to the branch power line 14 via the power outlet 14b.

  The PLC modem 22 normally transmits the original data after negotiating the communication conditions with the communication partner. The communication jamming device 30 can detect a packet for negotiation, but cannot block itself, but can block transmission of data following the packet. The disturbing signal generation period is set to a time sufficient to disturb such data transmission, for example, a time to disturb the header portion for data transmission.

  As shown in FIG. 3, in the case of a downlink PLC communication signal, the direction discriminating device 42 does not apply the activation signal to the interference signal generating device 44, and the interference signal generating device 44 does not generate the interference signal.

  The distance between the power outlets 14a and 14b may be extended to such a length that can determine whether the PLC communication signal is going up or down.

  The output of the PLC detection device 34 may be transmitted to the plus input terminal of the differential amplifier 40 wirelessly. In this case, the outlet 14a is connected to the PLC communication detecting device 34 and a first unit including a wireless transmitter for wirelessly transmitting the detection result, and the outlet 14b is connected to the PLC communication detecting device 38 and the differential amplifier 40. And a wireless receiver that receives the wireless output of the wireless transmitter and applies it to the plus terminal of the differential amplifier 40, a direction discriminating device 42, and a second unit comprising an interference signal generating device 44. .

  It is preferable that the frequency band of the interference signal generated by the interference signal generation device 44 is removed in advance from the frequency band used by the PLC modems 18 and 20. By doing so, the interference signal generated by the interference signal generator 44 does not interfere with the PLC communication between the PLC modems 18 and 20.

  Although the embodiment has been described in which the power plugs 32 and 36 are both connected to the outlets 14 a and 14 b on the branch power line 14, the power plug 32 may be connected to an outlet on the main power line 10. However, in that case, the outlet on the main power line 10 needs to have a distance from the joint between the main power line 10 and the branch power line 14 that is less than or equal to the distance from the joint to the power outlet 14b. Otherwise, the PLC communication signal output from the PLC modem 20 may be mistaken for the PLC communication signal from the PLC modem 22.

  Although an embodiment using an analog circuit has been described, it is obvious that a similar function can be realized by a digital circuit. For example, the propagation direction of the PLC communication signal can be determined by measuring the time of the start point and the end point of the PLC communication signal at the outlets 14a and 14b and comparing the time of the start point and the time of the end point.

  Although the invention has been described with reference to specific illustrative embodiments, various changes / modifications may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to those skilled in the field to which the present invention belongs, and such changes / modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. It is an example of an upstream timing chart. It is an example of a timing chart of a down direction.

Explanation of symbols

10: trunk power lines 12, 14, 16: branch power lines 14a, 14b, 14c: power outlets 18, 20, 22: PLC modem 30: communication jamming device 32: power plug 34: PLC communication detection device 36: power plug 38: PLC communication detector 40: differential amplifier 42: direction discriminator 44: interference signal generator

Claims (10)

A first power line communication detection step of detecting a power line communication signal at a first point on the power line;
A second power line communication detection step of detecting the power line communication signal at a second point away from the first point on the power line;
A direction determination step of determining whether or not the propagation direction of the power line communication signal is a predetermined direction from the detection outputs of the first and second power line communication detection steps;
And a jamming signal generating step of applying a jamming signal for a certain period to the power line when the propagation direction of the power line communication signal is the predetermined direction. The direction determination step is
Determining a direction of time delay between detection outputs of the first and second power line communication detection steps;
The method according to claim 1, further comprising a step of determining whether the propagation direction of the power line communication signal is the predetermined direction from the time delay direction. A first power line communication detection device (34) for detecting a power line communication signal at a first point on the power line;
A second power line communication detection device (38) for detecting the power line communication signal at a second point away from the first point on the power line;
A delay discriminating device (40) for discriminating the delay direction of the detection output of the first and second power line communication detecting devices;
A direction discriminating device (42) for discriminating whether or not the propagation direction of the power line communication signal is a predetermined direction according to the output of the delay discriminating device (40);
A jamming signal generator (44) for applying a jamming signal for a certain period to the power line according to the output of the direction discriminating device (42) when the propagation direction of the power line communication signal is the predetermined direction.
A communication jamming device.   The communication jamming device according to claim 3, wherein the delay direction discriminating device is a differential device (40) that generates a difference signal between detection outputs of the first and second power line communication detecting devices.   The direction discriminating apparatus discriminates whether or not the propagation direction of the power line communication signal is a predetermined direction based on the order of the positive pulse and the negative pulse and the time interval of the output of the differential device. 4. The communication jamming device according to 4. A method of determining a propagation direction of a power line communication signal propagating on a power line,
A first power line communication detection step of detecting the power line communication signal at a first point on the power line;
A second power line communication detection step of detecting the power line communication signal at a second point away from the first point on the power line;
And a direction determining step of determining whether or not the propagation direction of the power line communication signal is a predetermined direction from the detection outputs of the first and second power line communication detecting steps. The direction determination step is
Determining a direction of time delay between detection outputs of the first and second power line communication detection steps;
The propagation direction discriminating method according to claim 6, further comprising: discriminating a propagation direction of the power line communication signal from the time delay direction. An apparatus for determining a propagation direction of a power line communication signal propagating on a power line,
A first power line communication detection device (34) for detecting a power line communication signal at a first point on the power line;
A second power line communication detection device (38) for detecting the power line communication signal at a second point away from the first point on the power line;
A delay discriminating device (40) for discriminating the delay direction of the detection output of the first and second power line communication detecting devices;
Direction discriminating device (42) for discriminating the propagation direction of the power line communication signal according to the output of the delay discriminating device (40).
A propagation direction discriminating apparatus.   The propagation direction discriminating device according to claim 8, wherein the delay direction discriminating device is a differential device (40) that generates a difference signal between detection outputs of the first and second power line communication detecting devices. .   The direction discriminating apparatus discriminates whether or not the propagation direction of the power line communication signal is a predetermined direction based on the order of the positive pulse and the negative pulse and the time interval of the output of the differential device. 10. A propagation direction discriminating device according to 9.

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