JP4462216B2 - Power line communication device, power line communication network system, and power line communication method - Google Patents

Description

  The present invention relates to a power line communication device, a power line communication network system, and a power line communication method.

  Power line communication (PLC) is a technique for performing communication using a power line as a signal transmission path, and is described in Patent Document 1, for example.

FIG. 1 shows an example of a power line communication network system. The optical fiber 7 connected to the external Internet is connected to the photoelectric conversion device 6. A signal line S1 is connected to the photoelectric conversion device 6, and for example, broadband routers 50, 50 provided in each of the homes A, B, C of the apartment house as an ADSL line on the WAN side. , ... are connected.
The broadband router 50 is connected to parent modems (power line communication devices serving as parent devices) a1, b1, and c1 through a signal line S2 on the LAN side.

The transformer 5 is configured to connect a medium voltage distribution line that distributes a medium voltage of a three-layer AC (for example, 6 kV) to the primary side, and connect a power line 9 to the secondary side to reduce the medium voltage. It converts into voltage (for example, 200V). The power line 9 is connected to in-home power lines 9a, 9b, 9c in the homes A, B, C via a distribution board (not shown).
In each home, power outlets 10, 10,... Are appropriately provided on the home power lines 9 a, 9 b, 9 c, and the power outlet 10 is connected to a child modem (children connected to the parent modems a 1, b 1, c 1, and the personal computer 4. Power line communication device) a2, a3, b2, b3, c2, c3 are connected.

The power line communication networks (LANs) in the homes A, B, and C are operated as separate network groups. However, the in-home power lines 9a, 9b, 9c used as signal transmission paths in the power line communication network groups in the homes A, B, C are connected to the common power line 9.
Japanese Patent Laid-Open No. 10-145265

When multiple residential power lines 9a, 9b, and 9c are connected to the secondary power line 9 of the transformer, such as in each dwelling unit of a housing complex or a detached house, an attempt is made to perform power line communication independently in the house. However, the signals may interfere with each other through the common power line (distribution line) 9.
That is, when two or more power line communication network groups are constructed via the common power line 9, the communication signal in the power line communication network group (LAN) in one home is sent to the other via the common power line 9. It reaches the power line network group (LAN) in the customer's home and becomes noise. Conversely, a communication signal in the power line communication network group (LAN) in the other house also becomes noise for the power line network group (LAN) in one house.

  Therefore, when two or more power line communication network groups are constructed through a common power line, the signal-to-noise ratio of signals used for the original power line communication in each network group is lowered, and the communication quality is deteriorated. .

Therefore, as a measure for preventing quality deterioration due to signals from adjacent power line communication network groups, it is conceivable to reduce the output level (output power) of the signals.
That is, by reducing the output level of the signal of the modem (power line communication device) to such an extent that it does not reach the adjacent network group after attenuation, the output signal from the modem (power line communication device) of one network group It is possible to prevent the S / N ratio of the original received signal level of the modems (power line communication apparatuses) of the network groups from being affected.

However, when the output of the modem is lowered, the signal level received by the original communication partner (the modem in the own network group) is also lowered, the SN ratio is lowered, and the communication quality is lowered.
Therefore, from the viewpoint of improving communication quality, it is desirable to keep the output signal level large by reducing the degree of decrease in the output signal level of the modem as much as possible. However, if the output signal level is increased, it will be transferred to other network groups. As described above, this noise is generated.

  Thus, if it is intended to avoid interference with other network groups, it is necessary to reduce the output signal. If the signal-to-noise ratio of the signal received by the original communication partner is kept high, the output signal is increased. There were conflicting issues that had to be made.

  Therefore, an object of the present invention is to ensure good communication quality in the own network group while avoiding interference with other network groups.

[Power line communication equipment]
The present invention is a power line communication apparatus that uses a power line as a signal transmission path, and each frequency band in a signal transmission path between the power line communication apparatus of another power line communication network group connected to the power line communication network group of the power line communication apparatus. The transmission signal is controlled so that the transmission signal level in the frequency band in which the signal attenuation amount is smaller than a predetermined threshold is lower than the transmission signal level in other frequency bands based on the attenuation characteristic indicating the signal attenuation amount of The attenuation characteristic indicating the signal attenuation amount for each frequency band in the signal transmission path is determined by one of the own device and the power line communication device of the other power line communication network group. The test signal transmitted to detect the characteristic is obtained by receiving the test signal .

  According to the present invention, interference can be avoided by lowering the signal level of a transmission signal in a frequency band that may cause interference to other network groups. In addition, since the signal level can be relatively high for other frequency bands compared to the frequency band that can cause interference, the signal level as a whole can be relatively high, and communication within the own network group can be achieved. The deterioration of quality can be suppressed.

From another viewpoint, the present invention is a power line communication device that uses a power line as a signal transmission line, and from another power line communication network group connected to a common power line, the other power line in the frequency band of a transmission signal. an acquisition unit configured to acquire information indicating the interference frequency bands causing interference to the communication network group, the transmission signal level of the interfering frequency bands obtained by the previous SL acquisition means, lower than the signal level of the other frequency band in the transmission signal and control means, that features.

  In this case, since an interference frequency band that causes interference to another network group can be acquired from the other network group, the transmission signal level can be easily adjusted.

  From another viewpoint, the present invention is a power line communication device that uses a power line as a signal transmission path, and the received signal level for each frequency band of an interference signal from another power line communication network group connected to a common power line. Interference signal detection means for detecting, and notification means for notifying the other power line communication network group of a detection result by the interference signal detection means.

  According to the present invention, since the interference signal detection result can be notified to the network group that sends the interference signal, the network group that has received the notification can cope with the interference signal.

  The interference signal detecting means detects a frequency band in which an interference signal level from another power line communication network group exceeds a predetermined threshold, and the notification means is a frequency band exceeding the threshold. Is preferably communicated to the other power line communication network group.

Moreover, the said interference signal detecting means is adapted to detect the amount of interference signal level exceeds the frequency band and the threshold value exceeds a predetermined threshold value from other power line communication network group, the notification Preferably, the means notifies the other power line communication network group of the frequency band exceeding the threshold and the amount exceeding the threshold.
By notifying the other network group of the amount exceeding the threshold, the other network group can adjust the transmission signal level according to the amount.

[Power line communication network system]
From another viewpoint, the present invention relates to a power line communication network system in which a plurality of power line communication network groups are connected to a common power line, between a power line communication device of the own network group and a power line communication device of another power line communication network group. Based on the attenuation characteristics indicating the signal attenuation amount for each frequency band in the signal transmission path, the transmission signal level in the frequency band in which the signal attenuation amount is smaller than a predetermined threshold is lowered from the transmission signal level in other frequency bands. The attenuation characteristic indicating signal attenuation for each frequency band in the signal transmission path is configured to perform communication in the own network group, and the power line communication device and the other power line communication network in the own network group One of the power line communication devices of the group detects the attenuation characteristic. The test signal transmitted to, in which the other is obtained by receiving

  According to the present invention, even when a plurality of power line communication network groups are connected to a common power line, it is possible to suppress communication quality degradation within the own network group while avoiding interference between network groups.

  According to another aspect of the present invention, in a power line communication network system in which at least a first power line communication network group and a second power line communication network group are connected to a common power line, the frequency of an interference signal from the first power line communication network group An interference signal detection means for detecting a received signal level for each band on the second power line communication network group side, and a detection result by the interference signal detection means is notified from the second power line communication network group to the first power line communication network group. Based on the notification from the notification means and the notification means, the transmission signal level in the frequency band causing the interference to the second power line communication network group is lower than the transmission signal level in other frequency bands. 1 power line communication network group And a control means for controlling a transmission signal in the inner communication.

[Power line communication method]
A power line communication method in a case where there are a plurality of power line communication network groups connected to a common power line, and a signal transmission path between a power line communication device of its own network group and a power line communication device of another power line communication network group In order for one of the power line communication device of the own network group and the power line communication device of the other power line communication network group to detect the attenuation characteristic, the attenuation characteristic indicating the signal attenuation amount for each frequency band in FIG. The test signal transmitted to the other is received by the other , and based on the attenuation characteristic, the signal level of the frequency band in which the signal attenuation is smaller than a predetermined threshold is set to be higher than the signal level of the other frequency band. And communicate with your network group.

  According to the present invention, even when a plurality of power line communication network groups are connected to a common power line, the interference between the network groups can be avoided by reducing the signal level of the frequency band that interferes with other network groups. Therefore, it is possible to suppress a decrease in communication quality within the own network group.

[Power line communication equipment]
Another aspect of the present invention is a power line communication device that uses a power line as a signal transmission path, and is a power line communication of another power line communication network group connected to a common power line in a frequency band used in the power line communication. Control means for controlling to perform communication within the own network group without using at least a part of the frequency band in which interference from the apparatus is received is provided.

  According to the present invention, even when a plurality of power line communication network groups are connected to a common power line, a frequency band that receives interference from other network groups is not used for communication within the own network group. It is possible to suppress a decrease in communication quality within the own network group while avoiding interference between the networks.

  The power line communication device includes interference signal detection means for detecting a received signal level for each frequency band of interference signals from other power line communication network groups connected to a common power line, and the control means detects the interference signal detection Based on the detection result of the means, control is performed so that communication within the own network group is performed without using at least a part of the frequency band in the frequency band that receives interference from the power line communication device of another power line communication network group Is preferred.

  The interference signal detection means preferably detects a frequency band in which the interference signal level from another power line communication network group exceeds a predetermined threshold.

[Power line communication network system]
From another viewpoint, the present invention relates to a power line communication network system in which a plurality of power line communication network groups are connected to a common power line, from power line communication devices of other power line communication network groups in a frequency band used for power line communication. It is configured to perform communication in its own network group without using at least a part of the frequency band in which the interference occurs.

  According to the present invention, even when a plurality of power line communication network groups are connected to a common power line, a frequency band that receives interference from other network groups is not used for communication within the own network group. It is possible to suppress a decrease in communication quality within the own network group while avoiding interference between the networks.

  From another viewpoint, the present invention provides a power line communication network system in which at least a first power line communication network group and a second power line communication network group are connected to a common power line, and a frequency band of an interference signal from the first power line communication network group. Interference signal detection means for detecting the received signal level for each second power line communication network group, and at least one frequency band in the frequency band that receives interference from the first power line communication network group based on the detection result of the interference signal detection means. Control means for controlling to perform communication within the second power line communication network group without using the frequency band of the unit.

[Power line communication method]
From another viewpoint, the present invention is a power line communication method in the case where there are a plurality of power line communication network groups connected to a common power line, and the other power line communication network group in a frequency band used for power line communication. Communication is performed in the own network group without using at least a part of the frequency band in the frequency band that receives interference from the power line communication device.

  According to the present invention, even when a plurality of power line communication network groups are connected to a common power line, a frequency band that receives interference from other network groups is not used for communication within the own network group. It is possible to suppress a decrease in communication quality within the own network group while avoiding interference between the networks.

  ADVANTAGE OF THE INVENTION According to this invention, communication quality degradation within a self network group can be suppressed, avoiding the interference between network groups.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
As described above, FIG. 1 shows a power line communication network system in which a plurality of power line communication network groups are connected to a common power line 9. Note that the above description regarding FIG. 1 also applies to this embodiment.

  Hereinafter, the power line communication network group (PLC-LAN) constructed in the home A in FIG. 1 is referred to as a network group A, and the power line communication network group (PLC-LAN) constructed in the home B in FIG. The power line communication network group (PLC-LAN) constructed in the home C in FIG.

Each of the network groups A, B, and C is configured to perform power line communication using the power lines 9a, 9b, and 9c in the house as signal transmission paths. Each of the residential power lines 9a, 9b, 9c is branched from the common power line 9.
The original power line communication is performed separately in each of the network groups A, B, and C. However, communication signals in a certain network group may reach other network groups via the common power line 9. it can.

Each network group A, B, C is provided with one or a plurality of modems (power line communication devices) a1, a2, a3, b1, b2, b3, c1, c2, c3.
Within each network group, any one of the modems a1, b1, and c1 functions as a parent modem (master) that performs overall control of communication within the own network, and the other modems a2, a3, b2, b3, c2, and c3. Functions as a child modem (slave).

  In addition, in order to realize communication between different network groups A, B, and C, one modem among the parent modems (masters) of the plurality of network groups A, B, and C is connected to the plurality of network groups A, B, and C. It functions as an inter-group parent modem (master master; management modem) that controls the overall communication.

  Normally, the parent modem of the network group that tends to improve the communication quality with respect to other network groups is selected as the inter-group parent modem. For example, in the case of FIG. 1, since the network group B is close to the network group A and the network group C, it is preferable to cause the parent modem b1 of the network group B to function as an inter-group parent modem.

  In order to distinguish each of the network groups A, B, and C, an SSID (Service Set Identifier) is assigned to each group as a group name for identifying the group. Further, the MAC address assigned to each modem is used to identify each modem.

The SSID and the MAC address are added to the communication data (packet) between the modems for transmission / reception. Therefore, when the modem receives the signal, it recognizes the SSID included in the received data, and determines whether the signal is from the modem of its own network group or from another network group. be able to.
Further, when receiving a signal, the modem can identify the transmission source by recognizing the transmission source MAC address included in the received data.

  The parent and child modems perform communication by a frequency multiplexing method using a plurality of carriers (carrier waves) in a predetermined frequency band for power line communication (for example, 2M to 35 MHz). Specifically, the modem performs modulation using a modulation method called orthogonal frequency domain multiplexing (OFDM).

  In addition, since all the modems in each network group communicate using the same frequency band (for example, 2M to 35 MHz) or overlapping frequency bands, when a communication signal in the own group reaches another group, the other The modems in this group receive the signal, resulting in noise that interferes with the original communication signal of the other group.

  FIG. 2 shows functional blocks of a parent and a child modem (power line communication device). The modem includes a transmission unit 20 for transmitting a signal to a power line, a reception unit 30 for receiving a signal from the power line, and a control unit 40 for controlling transmission / reception of the modem.

  The error correction code unit 21 of the transmission unit 20 receives an input of a bit string as a transmission content from a terminal device such as the personal computer 4 connected to the modem or the photoelectric conversion device 6, and adds an error correction code to the bit string. The data is encoded, and the encoded data is output to the buffer 22.

The buffer 22 temporarily stores the data input from the error correction encoder 21 and outputs the stored data to the serial / parallel converter 23.
The serial / parallel converter 23 converts the serial data input from the buffer 11 into parallel data, and outputs the converted parallel data to the quadrature amplitude modulator 24.

  The quadrature amplitude modulation unit 24 distributes the data input from the serial / parallel conversion unit 23 to each of a plurality of orthogonal (for example, several hundred) carriers, and assigns the distributed data to each carrier. Further, the quadrature amplitude modulation unit 24 performs quadrature amplitude modulation (QAM) for modulating the amplitude and phase of the carrier wave based on the assigned data (symbol), and outputs the modulated signal to the inverse Fourier transform unit 25. To do.

  The quadrature amplitude modulation unit 24 increases or decreases the amplitude of the carrier wave based on the control signal from the control unit 40. Thereby, the signal level of the transmission signal output from the transmission unit can be increased or decreased for each carrier wave. That is, among the frequency bands used in power line communication, signal levels in some frequency bands can be made different from signal levels in other frequency bands.

The inverse Fourier transform unit 25 converts the modulation signal for each carrier wave input from the quadrature amplitude modulation unit 24 into a time domain modulation signal, and outputs the converted modulation signal to the parallel / serial conversion unit 26.
The parallel / serial conversion unit 26 converts the modulation signal input from the inverse Fourier transform unit into serial data and outputs the serial data to the guard interval unit 27.

  The guard interval unit 27 considers the delay time of each carrier in order to prevent inter-code interference due to multipath transmission using a plurality of carriers with respect to the serial data input from the parallel / serial converter 26. A process is performed to insert a guard interval that increases the symbol length of the transmission signal block by the guard interval, and the processed signal is output to the D / A converter 28.

The D / A conversion unit 28 converts the digital modulation signal input from the guard interval unit 27 into an analog modulation signal and outputs the analog modulation signal to the filter 29.
The filter 29 removes the harmonic component of the modulation signal input from the D / A conversion unit 28 and sends the processed modulation signal to the power line.

  The filter 31 of the receiving unit 30 removes harmonic components from the modulated signal received via the power line. Subsequently, the A / D conversion unit 32 converts the analog modulation signal into a digital signal, and the guard interval unit 33 performs processing for removing the guard interval.

Further, the serial / parallel converter 34 converts the signal into a set of parallel data equal to the number of subcarriers, and the Fourier transformer 35 converts the signal into a frequency domain signal for each carrier wave.
The output of the Fourier transform unit 35 is also output to the control unit 40 in addition to being output to the subsequent quadrature amplitude demodulation unit 36 for normal reception processing.

The quadrature amplitude demodulation unit 36 performs a demodulation process for reproducing the transmitted data based on the data input from the Fourier transform unit 35, and outputs the processed data to the parallel / serial conversion unit 37.
The parallel / serial conversion unit 37 converts the demodulated data for each carrier wave into serial data, and outputs the converted data to the buffer 38. The buffer 38 temporarily stores the data input from the parallel / serial conversion unit 37 until the error correction decoding unit 39 reads the data.

  The error correction decoding unit 39 reads the data stored in the buffer 38, performs error correction when the read data has an error, and outputs the corrected data to the terminal device or the photoelectric conversion device 6.

  In the power line communication network system as shown in FIG. 1, the power lines (distribution line paths) 9, 9a, 9b, 9c, which are signal transmission paths, have complicated attenuation characteristics. For example, the attenuation amount of the power lines 9a, 9, 9b from the modem a1 of the network group A to the modem b1 of the other network group B is greatly different for each frequency as shown in FIG.

  When the lines 9a, 9 and 9b have such attenuation, the signal Ds shown in FIG. 4 (frequency band 5 to 25 MHz, signal level of each carrier is equal) is transmitted from one group A to the own group A. Then, the modem b1 of the other group B receives the attenuated interference signal Dr as shown in FIG. This interference signal Dr becomes noise for the modem b1, and reduces the SN ratio of the original received signal (signals from other modems b2 and b3 in the same group B).

  However, the interference signal Dr from group A does not reduce the SN ratio of the original received signal of the modem b1 in the entire frequency band. That is, the interference signal Dr has a frequency band fi that has a signal level higher than a predetermined level (threshold value) L without degrading the SN ratio of the original received signal of the modem b1 in a frequency band where the signal level is sufficiently low. Only, the SN ratio of the original received signal of the modem b1 is lowered. In the frequency band fi of FIG. 4, the maximum value of the amount L1 that exceeds the threshold value L is about 10 dB.

  In the first embodiment, in order to prevent interference from group A to group B (decrease in S / N ratio), the signal Ds1 transmitted from the modem a1 of group A may cause interference in group B. In fi, the signal level is lowered in accordance with the amount L1 exceeding the threshold value L. On the other hand, among the frequency bands used for communication, the signal level is maintained relatively high in frequency bands other than the frequency band fi.

  By setting the transmission signal Ds1 of the modem a1 as described above, the level of the signal received by the modem b1 of the group B becomes equal to or less than the threshold value L even in the frequency band fi and is used for communication within the group B. In all the frequency bands that are generated, it is possible to prevent a decrease in SNR (interference) due to a signal from group A.

  Moreover, in order to avoid interference from the group A to the group B, the signal level of the signal Ds1 is generally higher than that of the signal Ds2 in which the level of the output signal Ds1 of the modem a1 is simply lowered by 10 dB as a whole. . Therefore, the modem a1 of the group A can effectively use the level difference between the two signals Ds1 and Ds2 for the original communication in the group A, and the communication quality is improved as compared with the case where the signal level is lowered as a whole. The degree of performance degradation from the communication quality (communication quality of group A alone) is also minimized.

Hereinafter, the above process will be described in more detail.
Here, a case will be described as an example where the network groups B and C of FIG. 1 are already operating and the output signal levels of the modems a1, a2, and a3 are determined so that the network group A starts communication.

  As described above, the communication beyond the network group is controlled by the parent modem selected as the inter-group parent modem (for example, the parent modem b1 of group B). In the following processing, for example, the intra-group communication and the inter-group communication are performed in a time division manner so that the intra-group communication and the inter-group communication do not interfere with each other.

  First, the control unit 40 of the group A modem a1 performs a negotiation process for establishing communication with other group B and C modems. If only a part of the frequency bands used for power line communication can be used, communication is established using the frequency band (carrier) (inter-group communication establishment function of the control unit).

  When communication between both modems is established, the modem a1 is notified of the SSID as data specifying the transmission source group A and the MAC address as data specifying the transmission source modem a1. With these data, the modem b1 can recognize the transmission source group A and the transmission source modem a1 of the test signal.

  When communication between both modems a1 and b1 is established, the control unit 40 of the modem b1 checks the SSID notified from the modem a1 and recognizes that the signal is transmitted from another network group A instead of the own group. (Other group signal recognition function of the control unit).

  When communication between the modem a1 of the group A and the modem b1 of the other group B is established, the control unit 40 of the modem a1 transmits the signal Ds (all frequency bands f1, f1 used for communication) as shown in FIGS. .. are transmitted from the transmission unit 20 to the power line 9a as a test signal (test signal transmission function of the control unit).

  The test signal Ds reaches the modem b1 of the group B via the power lines 9a, 9, 9b. However, the test signal Ds reaches the modem b1 as an attenuated signal Dr as shown in FIGS. The signal Dr has a frequency band fi having a level that exceeds a threshold L that is a level receivable by the modem b1. In addition, the carrier of this frequency band fi is used for communication establishment between both modems a1 and b1.

  Here, when the level of the signal Dr reaching the modem b1 is lower than the threshold value, the communication between the two modems a1 and b1 cannot be established. Since no interference occurs, the following processing is not necessary.

Subsequently, the control unit 40 of the modem b1 detects whether or not the interference signal Dr has a frequency band fi having a level exceeding the threshold L (interference signal detection function of the control unit).
Specifically, the control unit 40 of the modem b1 examines the signal level for each of a plurality of carriers (carriers) given from the Fourier transform unit 35 of the modem receiving unit 30, and degrades the SN ratio of the received signal inherent to the modem b1. An interference frequency band fi (carrier) that is larger than the threshold value L that is a level to be detected is detected (interference frequency band detection function of the control unit).
Further, the control unit 40 of the modem b1 detects an amount L1 exceeding the threshold L in a frequency band larger than the threshold L (interference amount detection function of the control unit).

  The control unit 40 of the modem b1 detects the interference frequency band fi and the amount L1 exceeding the threshold value L in the frequency band fi as a result of detecting the interference signal, so that the modem a1 of the group A1 is notified. The detection unit transmits the detection result to the modem a1 (detection result notification function of the control unit). L1 is reported for each frequency band (for each carrier).

  The above processing is performed not only between the modem a1 and the modem b1, but also between the modem a1 and the other modems b2 and b3 of the group B and the modems c1, c2 and c3 of the group C.

  The modem a1 receives detection results from the modem b1 and other modems in the other groups B and C (detection result (information indicating interference frequency band) acquisition function of the control unit). The modem a1 stores the detection result. When the modem a1 performs the original communication in its own network group A, the signal level of the frequency band fi that causes interference to the modems of other groups is set like the transmission signal Ds1 shown in FIG. Decrease according to L1 (transmission signal control function of the control unit).

  Such adjustment of the output signal level can be performed for each carrier. That is, the control unit 40 of the modem a1 gives a control signal for signal level adjustment to the quadrature amplitude modulation unit of the transmission unit 20, and causes the carrier amplitude exceeding the threshold to interfere with the carrier (frequency band). Decrease according to the amount L1.

  The degree of the decrease in the level of the transmission signal may be the same as the amount of interference L1, or the degree of decrease may be greater than the amount of interference L1. Further, the output level of a carrier that causes interference may be 0, that is, a carrier that causes interference may not be used.

  With the above processing, the adjustment processing of the output signal level of the modem a1 is completed. Subsequently, in parallel with the processing of the modem a1, the adjustment processing of the output signal level is similarly performed for the other modems a2 and a3 of the group A. When the adjustment of the output signal level is completed for all the modems a1, a2, and a3 in the group A, even if communication is performed in the group A, it does not interfere with communication in the other groups B and C.

  Further, the output signal level of each of the modems b1, b2, b3, c1, c2, and c3 of the groups B and C is set by the same process as described above so as not to interfere with the modems a1, a2, and a3 of the group A. Adjusted.

  As described above, even when a plurality of independent power line communication network groups A, B, and C exist on the common power line 9, interference with other groups is suppressed while minimizing communication quality degradation within the own group. Can be prevented.

[Second Embodiment]
FIG. 9 shows a second embodiment of the present invention. The points not particularly described in the second embodiment are the same as those in the first embodiment.
When the process according to the second embodiment shown in FIG. 9 is compared with the process of FIG. 6 which is the first embodiment, the process until the interference signal detection is the same. In the first embodiment, when the modem b1 detects the interference signal, the modem a1 on the group A side takes measures against the interference (signal level reduction processing) based on the detection result. In the second embodiment, The modem b1 on the group B side handles the interference.

  That is, when the control unit 40 of the modem b1 detects the frequency band fi exceeding the threshold L, in the communication within the own network group B, the control unit 40 does not use the frequency band fi (carrier) for communication. The same applies to the other modems b2 and b3 in the group B. That is, in each of the modems b1, b2, and b3 of the group B, the frequency band fi (carrier) that receives interference from the other groups A and C is not used in the communication within the group B.

  However, even in the interference frequency band, the frequency band that originally has a lot of noise is less influenced by other groups, and may be used for intra-group B communication. That is, only a part of the interference frequency band may not be used for intra-group communication.

Specifically, at the time of signal transmission, the quadrature amplitude modulation unit 24 of the modem transmission unit 20 does not use the carrier of the interference frequency band fi in the frequency band used in power line communication for modulation, and performs communication in the remaining frequency band. Do. Further, at the time of signal reception, the quadrature amplitude demodulator 37 of the modem receiver 30 demodulates the signal with the interference frequency fi ignored.
As a result, in group B, communication is originally performed in a frequency band other than the frequency band that receives interference from other groups A and C among the communication frequency bands used in group B. Therefore, it is possible to suppress a decrease in communication quality within the own group while avoiding interference from other groups.

  The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention. For example, the threshold value L need not be the same for all frequency bands, and may be different for each frequency band. Specifically, in a frequency band with a lot of noise and a low S / N ratio in communication within its own network group, the bit allocation for data transmission is reduced, so that there is little problem even if it receives some interference from other network groups. Therefore, the threshold value can be relatively increased for the frequency band that is originally affected by noise.

1 is an overall configuration diagram of a power line communication network system. It is a functional block diagram of a modem. It is a figure which shows the frequency-attenuation amount characteristic of a power line. It is a figure which shows the transmission signal Ds and the attenuated reception signal Dr. It is a figure which shows the output signal Ds1 which adjusted the level partially, and the output signal Ds2 which lowered the level entirely. It is a procedure figure of the interference coping process in 1st Embodiment. It is explanatory drawing which shows the spectrum of the one part carrier wave of signal Ds. It is explanatory drawing which shows the spectrum of the one part carrier wave of the signal Dr. It is a procedure figure of the interference coping process in 2nd Embodiment.

Explanation of symbols

A Power line communication network group B Power line communication network group C Power line communication network group a1, a2, a3 Modem (power line communication device)
b1, b2, b3 modem (power line communication device)
c1, c2, c3 modem (power line communication device)
9 Power Line 20 Transmitter 30 Receiver 40 Control Unit fi Interference Frequency Band L Threshold L1 Amount Exceeding Threshold

Claims (9)

A power line communication device using a power line as a signal transmission path,
The signal attenuation amount is predetermined based on an attenuation characteristic indicating a signal attenuation amount for each frequency band in a signal transmission path between the own device and a power line communication device of another power line communication network group connected to a common power line. Control means for controlling the transmission signal so that the transmission signal level of the frequency band smaller than the threshold is lower than the transmission signal level of the other frequency band;
The attenuation characteristic indicating the signal attenuation amount for each frequency band in the signal transmission path is for one of the own apparatus and the power line communication apparatus of the other power line communication network group to detect the attenuation characteristic. A power line communication apparatus, wherein the transmitted test signal is obtained by receiving the other test signal . A power line communication device using a power line as a signal transmission path,
An acquisition unit that acquires information indicating an interference frequency band that causes interference to the other power line communication network group among the frequency bands of the transmission signal from another power line communication network group connected to the common power line;
Control means for lowering the transmission signal level of the interference frequency band acquired by the acquisition means to be lower than the signal level of other frequency bands in the transmission signal;
A power line communication device comprising: A power line communication device using a power line as a signal transmission path,
Interference signal detection means for detecting a received signal level for each frequency band of interference signals from other power line communication network groups connected to a common power line;
Notification means for notifying the other power line communication network group of the detection result by the interference signal detection means;
A power line communication device comprising: The interference signal detection means detects a frequency band in which an interference signal level from another power line communication network group exceeds a predetermined threshold,
The notifying means communicates the frequency band exceeding the threshold to the other power line communication network group;
The power line communication apparatus according to claim 3. Wherein the interference signal detecting means is adapted to detect the amount of interference signal level exceeds the frequency band and the threshold value exceeds a predetermined threshold value from other power line communication network group,
The notifying means notifies the other power line communication network group of a frequency band exceeding the threshold and an amount exceeding the threshold;
The power line communication apparatus according to claim 3 or 4, characterized by the above. In a power line communication network system in which a plurality of power line communication network groups are connected to a common power line,
Based on the attenuation characteristic indicating the signal attenuation amount for each frequency band in the signal transmission path between the power line communication device of the own network group and the power line communication device of another power line communication network group, the signal attenuation amount is a predetermined threshold value. The transmission signal level of the smaller frequency band is configured to be lower than the transmission signal level of the other frequency band to perform communication in the own network group,
The attenuation characteristic indicating the signal attenuation amount for each frequency band in the signal transmission path is determined by one of the power line communication device of the own network group and the power line communication device of the other power line communication network group being the attenuation. A power line communication network system, characterized in that a test signal transmitted to detect a characteristic is obtained by receiving the other test signal . In a power line communication network system in which at least a first power line communication network group and a second power line communication network group are connected to a common power line,
Interference signal detection means for detecting a received signal level for each frequency band of an interference signal from the first power line communication network group on the second power line communication network group side;
Notification means for notifying the detection result by the interference signal detection means from the second power line communication network group to the first power line communication network group;
Based on the notification from the notification means, the first power line communication network is configured such that the transmission signal level of the frequency band that causes interference with the second power line communication network group is lower than the transmission signal level of other frequency bands. A power line communication network system comprising control means for controlling a transmission signal in intra-group communication. A power line communication method when there are a plurality of power line communication network groups connected to a common power line.
Attenuation characteristics indicating a signal attenuation amount for each frequency band in a signal transmission path between a power line communication device of the own network group and a power line communication device of another power line communication network group, and the power line communication device of the own network group and the power line communication device One of the power line communication devices of the other power line communication network group is obtained by receiving the test signal transmitted to detect the attenuation characteristic by the other,
Based on the damping characteristics, the signal attenuation is lower than the signal level of the predetermined other frequency band a signal level of a small frequency band than the threshold, and performs communication in its own network group Power line communication method.   4. The power line communication apparatus according to claim 3, wherein the interference signal detection means detects a frequency band in which an interference signal level from another power line communication network group exceeds a predetermined threshold value.

Images