JP2007300355A - Power-line carrier communication equipment and power-line carrier communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a communication speed by using a communication time more effectively. <P>SOLUTION: One or a plurality of large groups are determined on the whole by deciding one network group or that a plurality of network groups wherein signals do not interfere with one another belong to one large group. Simultaneously communication is permitted for the respective network groups in the same large group and communication times are allocated on a time-division basis to all large groups. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power line communication device and a power line communication method for configuring a network using power lines such as distribution lines.

  Power Line Communication (PLC) is a communication system that superimposes data communication signals on commercial AC voltage (current) using a distribution line drawn into each home or office as a signal transmission line. There is an advantage that it is not necessary to perform wiring for communication (for example, refer to Patent Document 1). A modem (power line communication device) is connected to an outlet provided on the distribution line, and a terminal device such as a personal computer is connected thereto. A plurality of modems can be installed in the house, and these constitute a local area network in the house.

  In addition, for example, the secondary side electric circuit of a common transformer is usually branched and drawn into a plurality of houses that are geographically close to each other. That is, the indoor distribution lines (electric power lines) of these houses are connected to each other.

JP-A-10-145265 (pages 2 and 3)

  In the conventional power line communication as described above, when power line communication is simultaneously performed in local area networks of a plurality of adjacent houses, signals may interfere through indoor distribution lines connected to each other. In that case, the signal-to-noise ratio of the signal used for power line communication is lowered and the communication quality is deteriorated. Therefore, in order to avoid simultaneous communication in multiple local area networks that interfere with signals, one modem becomes the overall master that manages the whole, and communication time is allocated to each local area network by time division. Do. For example, if the number of local area networks is n, the communication time allocation to each local area network is 1 / n.

  However, the number of local area networks includes not only the number directly detected by the general master, but also the number indirectly detected by sharing information acquired by any modem with each modem. Therefore, in actuality, 1 / n is assigned including a network that does not cause interference even if simultaneous communication is performed. In this case, it cannot be said that communication time is fully utilized effectively.

  In view of the above-described conventional problems, an object of the present invention is to improve communication speed by more effectively using communication time.

  The power line communication device according to the present invention is one of the power line communication devices provided in each of a plurality of network groups each having a distribution line branched from a common power line as a signal transmission path, and is connected to one network group or to each other. By defining a plurality of network groups that do not cause signal interference as belonging to one large group, a large group setting function for defining one or a plurality of large groups as a whole, and for each network group within the same large group And a management function for permitting simultaneous communication and allocating communication time by time division to all large groups.

  In the power line communication apparatus configured as described above, communication time is allocated to all large groups in a time division manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. Accordingly, when the number of large groups is m and the total number of network groups is n (> m), compared with the allocation 1 / n of communication time per group when performing communication in a time division manner for each network group, The communication time allocation is 1 / m, and the communication speed is improved.

  The power line communication device of the present invention is one of the power line communication devices provided in each of a plurality of network groups having a distribution line branched from a common power circuit as a signal transmission path, By defining a plurality of network groups that do not cause signal interference with each other as belonging to one large group, a large group setting function that defines one or a plurality of large groups as a whole and signals in any combination between network groups Information acquisition function that acquires whether or not simultaneous communication is possible without causing interference, and simultaneous communication is permitted to each network group in the same large group, and all communication that has already been performed The above-mentioned availability information is possible for a network group belonging to a large group different from the network group. Sometimes allow simultaneous communication, when the permission information is negative is that a management function of allocating the communication time by time division for all the large group.

  In the power line communication apparatus configured as described above, if the availability information is negative, communication time is allocated to all large groups in a time-sharing manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. Accordingly, when the number of large groups is m and the total number of network groups is n (> m), compared with the allocation 1 / n of communication time per group when performing communication in a time division manner for each network group, The communication time allocation is 1 / m, and the communication speed is improved. On the other hand, even if the network group belongs to a large group different from all network groups that are already communicating, simultaneous communication is permitted when the availability information is available. Accordingly, there may be a case where simultaneous communication is permitted individually as a network group, thereby further ensuring communication time and improving the communication speed.

  On the other hand, the present invention is a power line communication method using a power line communication device provided in each of a plurality of network groups using a distribution line branched from a common power line as a signal transmission line, and one of the power line communication devices. By defining the network as a management device and defining one network group or a plurality of network groups that do not cause signal interference with each other as belonging to one large group, one or a plurality of large groups are defined as a whole, The management apparatus permits simultaneous communication to each network group in the same large group, and assigns communication time to all large groups by time division.

  In the power line communication method as described above, communication time is allocated to all large groups in a time-sharing manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. Accordingly, when the number of large groups is m and the total number of network groups is n (> m), compared with the allocation 1 / n of communication time per group when performing communication in a time division manner for each network group, The communication time allocation is 1 / m, and the communication speed is improved.

  The present invention is also a power line communication method using a power line communication device provided in each of a plurality of network groups in which a distribution line branched from a common power line is used as a signal transmission line, one of the power line communication devices. By defining one network group or a plurality of network groups that do not cause signal interference with each other as belonging to one large group, one or a plurality of large groups are defined as a whole, and the management A device acquires whether or not simultaneous communication is possible without causing signal interference in any combination between network groups, and the management device simultaneously transmits to each network group in the same large group. A network that is allowed to communicate and belongs to a large group different from all network groups that are already communicating. For a group permits simultaneous communication when the availability information is allowed, when the permission information is negative is characterized by assigning a communication time by time division for all the large group.

  In the power line communication method as described above, if the availability information is negative, communication time is allocated to all large groups in a time-sharing manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. Accordingly, when the number of large groups is m and the total number of network groups is n (> m), compared with the allocation 1 / n of communication time per group when performing communication in a time division manner for each network group, The communication time allocation is 1 / m, and the communication speed is improved. On the other hand, even if the network group belongs to a large group different from all network groups that are already communicating, simultaneous communication is permitted when the availability information is available. Accordingly, there may be a case where simultaneous communication is permitted individually as a network group, thereby further ensuring communication time and improving the communication speed.

  According to the power line communication apparatus / power line communication method of the present invention, communication time is allocated to all large groups in a time division manner, and signal interference is prevented. Simultaneous communication is permitted for network groups belonging to the same large group. Therefore, the allocation of communication time is increased and the communication speed is improved.

  In addition, according to another power line communication apparatus / power line communication method of the present invention, if availability information is negative, communication time is allocated to all large groups in a time-sharing manner, thereby preventing signal interference. The Simultaneous communication is permitted for network groups belonging to the same large group. Therefore, the allocation of communication time is increased and the communication speed is improved. On the other hand, even if the network group belongs to a large group different from all network groups that are already communicating, simultaneous communication is permitted when availability information is available, so simultaneous communication is permitted individually as a network group. When the case occurs, the communication time is further secured and the communication speed is improved.

  1 and 2 are connection diagrams showing a plurality of local area network (LAN) groups (hereinafter referred to as network groups) constructed by power line communication. Although it is divided into two sheets for convenience of illustration, the two sheets are one connection diagram. In the figure, a plurality of houses (here, six houses) H1 to H6 are actually arranged in the order shown in the figure while being geographically close to each other. In each house H1 to H6, independent network groups 1 to 6 are configured, respectively.

  The voltage (for example, 6 kV) of the high voltage distribution line 7 is stepped down by the transformer 8, and a predetermined voltage (100/200 V) is supplied to the low voltage distribution line 9. The low-voltage distribution line 9 branches and is drawn into the houses H1 to H6 to form indoor distribution lines 91 to 96. That is, all the indoor distribution lines 91 to 96 are branched from the low-voltage distribution line 9 which is a common electric circuit. House H1 is closest to transformer 8, followed by houses H2, H3, H4, and H5, and house H6 is furthest from transformer 8.

  In the house H <b> 1, power line communication devices (hereinafter referred to as modems) A, B, and C are connected to the indoor distribution line 91. This connection is made by inserting the power plugs of the modems A, B, and C into outlets. Of these, one modem A is connected to an O / E converter 12 that performs optical / electrical signal conversion, and an optical fiber 11 is connected to the O / E converter 12 from the outside. Also, terminal devices (such as personal computers and home appliances having a communication function) 13 and 14 are connected to the modems B and C, respectively.

  The modems A, B, and C and the terminal devices 13 and 14 connected thereto constitute a local area network of “network group 1” through power line communication via the indoor distribution line 91. The terminal device 13 is connected to the modems B and A via the O / E converter 12 and the optical fiber 11, and the terminal device 14 is connected to the Internet and the like via the modems C and A via the O / E converter 12 and the optical fiber 11. It is possible to communicate with a higher level network. Note that the number of modems (three) and the number of terminal devices (two) are merely examples, and a modem B or C may be connected to the O / E converter 12 instead of the modem A ( The same applies hereinafter.)

  Similarly, in the house H <b> 2, modems D, E, and F are connected to the indoor distribution line 92, and the modem D is connected to the optical fiber 21 via the O / E converter 22. Terminal devices 23 and 24 are connected to the modems D and E, respectively. The modems D, E, and F and the terminal devices 23 and 24 connected thereto constitute a local area network of “network group 2” by power line communication via the indoor distribution line 92.

Similarly, in the house H3, the indoor distribution line 93, the modems G, H and I, the O / E converter 32, the optical fiber 31, and the terminal devices 33 and 34 exist, and the local area network of the “network group 3” exists. Composed.
In the house H4, an indoor distribution line 94, modems J, K, and L, an O / E converter 42, an optical fiber 41, and terminal devices 43 and 44 exist, and a local area network of “network group 4” is configured.

In the house H5, there are an indoor distribution line 95, modems M, N and O, an O / E converter 52, an optical fiber 51, and terminal devices 53 and 54, and a local area network of “network group 5” is configured.
In the house H6, there are an indoor distribution line 96, modems P, Q and R, an O / E converter 62, an optical fiber 61, and terminal devices 63 and 64, and a local area network of “network group 6” is configured.

  FIG. 3 is a block diagram showing an example of an internal circuit configuration related to power line communication in the modems A to R. In the figure, modems A to R include a PLC transmission / reception unit 101 that performs modulation / demodulation processing to perform signal transmission / reception to / from a power line, a control unit 102 that performs communication control, and a signal / noise ratio (S / N ratio) of a power line communication carrier wave. ) Is detected. By inserting the plug 105 of the power cord 104 that serves as both power supply and communication into an outlet 106 provided on the indoor distribution lines 91 to 96, the modems A to R can perform power line communication.

  Each of the modems A to R in a state in which power line communication is possible can communicate with all the modems in the vicinity of the modem A to R, and can recognize the topology from the modem to the modems. In such communication between modems, information obtained from one modem capable of direct communication is given to other modems capable of direct communication so that information is linked in a chain and all information is shared by each modem. For example, all modems belonging to the same network group use the same SSID (Service Set Identity), so there are several network groups around the modem to which network group the modem belongs by communication between modems. Each modem A to R can acquire information such as whether or not. Further, the distance can be grasped from the S / N ratio and the received power.

  On the other hand, each modem A to R acquires and holds information on whether or not direct communication is possible with modems belonging to different network groups. If direct communication is possible, signal interference occurs when the network group to which it belongs and the network group to which the other modem belongs simultaneously communicate with each other. If direct communication is impossible, even if the network group to which the own modem belongs and the network group to which the other modem belongs simultaneously communicate with each other, no signal interference occurs. If no signal interference occurs, there is no risk of communication quality deterioration even if power line communication is performed simultaneously.

  In the configuration of FIGS. 1 and 2, signal interference usually occurs between geographically adjacent houses. For example, when paying attention to the network groups 1 to 3, signal interference occurs between the network groups 1-2 and 2-3, but signal transmission occurs between the network groups 1-3 even if simultaneous communication is performed. In some cases, no interference occurs. Therefore, when communication is performed in both network groups 1 and 2, a communication time is assigned to each group by time division so that communication is not performed simultaneously. The same applies when communication is performed in both network groups 2 and 3. Such communication control is performed by a single modem serving as a management apparatus described below.

  In each of the network groups 1 to 6, any one modem serves as a master (hereinafter referred to as an individual master) for each network group, and manages and controls communication within the network group. Basically, the first modem turned on in the network group becomes the individual master. In addition, the modem having the best function may be the individual master.

  FIG. 4 is a diagram illustrating an example of a topology configured by the modems A to I in FIG. Note that the existence of the network groups 4 to 6 is omitted here for simplification of description. In network groups 1 to 3, it is assumed that network group 1 is first set up. Here, “start up” includes a case where a network group is originally configured by installing a modem, and a case where a network group is configured by turning on power from a power-off state. Further, it is assumed that the modem A in the network group 1 is powered on first and becomes an individual master.

  Subsequently, assuming that the network group 2 is started up and the modem D is an individual master in the network group 2, the modem A that is the individual master of the network group 1 that has been started up earlier is managed in the own network group 1. Along with the control, it becomes a master of master as a management device that manages the entire network groups 1 and 2. Management of the network group 2 by the modem A is performed for the modem D which is an individual master in the network group.

  Similarly, assuming that the network group 3 is up and the modem G is an individual master in the network group 3, the modem A, which is the individual master of the network group 1 that has been up first, manages in the own network group 1. Along with control, it becomes an overall master that manages the entire network group 3. Management of the network group 3 by the modem A is performed for the modem G which is an individual master via the modem D.

  In this way, the modem A that becomes the general master of the network groups 1 to 3 performs management to share the communication time by time division. As described above, when communication is performed in both network groups 1 and 2, communication time is assigned to each group by time division so that communication is not performed simultaneously. The same applies when communication is performed in both network groups 2 and 3.

  Next, a function (large group setting function) for setting a larger “large group” with each of the network groups 1 to 6 as a “small group” will be described. FIG. 5 is a diagram showing only the existence of network groups 1 to 6 for the low-voltage distribution line 9 by simplifying the configuration shown in FIGS. 1 and 2. In the figure, signal interference occurs between adjacent network groups, but signal interference does not occur between a certain network group and its two adjacent network groups. As a result, the network groups 1, 3, and 5 do not cause signal interference even if they simultaneously communicate with each other. Similarly, even if the network groups 2, 4 and 6 communicate with each other simultaneously, no signal interference occurs.

  Therefore, if network groups 1, 3 and 5 are defined as belonging to “large group X” and network groups 2, 4 and 6 are defined as belonging to “large group Y”, network groups belonging to the same large group are assigned. On the other hand, simultaneous communication may be permitted, and simultaneous communication of network groups belonging to different large groups should not be permitted.

  On the other hand, as shown in FIG. 6, when signal interference can occur between two adjacent network groups, for example, simultaneous communication between the network groups 1 and 2 or 3 causes signal interference. However, the network groups 1 and 4 do not cause signal interference even if they are simultaneously communicated. Similarly, no signal interference occurs even if simultaneous communication is performed in any combination of network groups 2 and 5 and network groups 3 and 6. Therefore, if it is determined that the network groups 1 and 4 belong to the “large group X”, the network groups 2 and 5 belong to the “large group Y”, and the network groups 3 and 6 belong to the “large group Z”, respectively. This means that simultaneous communication may be permitted for network groups belonging to the group, and simultaneous communication of network groups belonging to different large groups should not be permitted.

  A procedure for controlling communication based on the above-mentioned concept of the large group will be described with reference to the flowcharts of FIGS. The processes in these flowcharts are executed by a modem that becomes an overall master from an individual master.

<< Pattern 1 >>
First, in an initial state in which only one network group as a small group (hereinafter simply referred to as a small group) has been established, the individual master of the small group is a single group by the small group in step S1 of FIG. And the small group is determined to belong to the large group X (large group setting function). Next, the individual master determines whether or not another small group exists (step S2). If it does not exist, steps S1 and S2 are repeated. On the other hand, when the presence is detected, there is a possibility of signal interference with the small group. Therefore, in step S3, the general master promoted from the individual master designates the small group as the large group X in which the self exists. It is determined that it belongs to the large group Y different from the above and is registered (large group setting function).

  Then, the general master assigns communication time to the large group X and the large group Y. As a result, communication is performed in a time-sharing manner (step S4), and simultaneous communication is permitted to small groups within the same large group. Subsequently, the general master determines whether or not there is another small group (step S5). If there are no other small groups, the processes of steps S4 and S5 are repeated. On the other hand, when the presence of another small group is detected, it is determined whether or not the new small group has signal interference with the large group X (step S6). Here, if there is no interference, the general master determines that the new small group belongs to the large group X and registers it (step S7).

  On the other hand, if there is interference, it is further determined whether or not the new small group has signal interference with the large group Y (step S8). Here, if there is no interference, the general master determines that the new small group belongs to the large group Y (step S11), and returns to step S4. On the other hand, if there is interference, the general master determines in step S9 that the new small group belongs to the large group Z different from the large groups X and Y, and registers (large group setting function). Then, the general master assigns communication time to the large groups X, Y, and Z, and thereafter, communication is performed in a time division manner by the three large groups X, Y, and Z (step S10). At the same time, simultaneous communication is permitted to small groups within the same large group.

  Next, general processing when a plurality of large groups already exist will be described with reference to the flowchart of FIG. First, the general master performs time-division communication in a plurality of large groups (step S21). Next, the general master determines whether another new small group exists (step S22). If there is no other small group, the processes of steps S21 and S22 are repeated. On the other hand, when the presence of another small group is detected, it is determined whether or not the new small group has signal interference with all the large groups (step S23). Here, if there is a large group without interference, the general master determines that the new small group belongs to the large group without interference and registers it (step S25). On the other hand, if there is interference, the general master determines that the new small group belongs to a large group different from the existing large group, and registers it (step S24).

  With the above processing, for example, if the network groups 1 to 6 are up and the signal interference is in the state shown in FIG. 5, the general master can control the large group X (network groups 1, 3, 5) and large group Y ( Communication is permitted to the network groups 2, 4, 6) in a time division manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. These permissions are provided as a management function by the overall master. Accordingly, the allocation of communication time given to each network group (that is, corresponding to the communication speed) is ½ of that of a single large group, but is の of the case of time division for each small group. In comparison, the communication speed is improved three times.

  Similarly, if the signal interference is in the state of FIG. 6, the general master has the large group X (network group 1, 4), large group Y (network group 2, 5), and large group Z (network group 3, 6). ) In a time-sharing manner, thereby preventing signal interference. Simultaneous communication is permitted for network groups belonging to the same large group. These permissions are provided as a management function by the overall master. Therefore, the communication time allocation (communication speed) given to each network group is 1/3 of that of a single large group, but compared with 1/6 of the time division for each small group, the communication speed. Is doubled.

<< Pattern 2 >>
Next, other processes different from those in FIGS. 7 and 8 will be described with reference to the flowchart in FIG. For example, when the network groups 1 to 6 are standing up and the signal interference is in the state of FIG. Not. However, when viewed individually, even if the network groups 1 and 4 perform simultaneous communication, signal interference does not occur because the distances are far from each other. Table 1 shows whether or not simultaneous communication is possible without causing signal interference between the two network groups in the interference state shown in FIG. In the table, ◎ indicates a case where simultaneous communication is possible due to belonging to the same large group, and ○ indicates a case where simultaneous communication is possible individually. The general master acquires this availability information (information acquisition function).

  In addition, when the network groups 1 to 6 are up and the signal interference is in the state shown in FIG. 6, according to the processing of the above-described pattern 1, for example, the network groups 1 and 5 or 6 belong to different large groups. Communication is not allowed. However, when viewed individually, even if the network groups 1 and 5 or 1 and 6 perform simultaneous communication, signal interference does not occur because the distances are far from each other. Table 2 shows whether or not simultaneous communication is possible without causing signal interference between the two network groups in the interference state shown in FIG. In the table, ◎ indicates a case where simultaneous communication is possible due to belonging to the same large group, and ○ indicates a case where simultaneous communication is possible when viewed individually. The general master acquires this availability information (information acquisition function).

  Next, processing different from those in FIGS. 7 and 8 based on the availability information in Tables 1 and 2 will be described with reference to the flowchart in FIG. This process includes a large group setting function, the information acquisition function described above, and a management function.

  First, it is assumed that one small group is communicating (step S30). The individual master of this small group determines whether another new small group starts communication (step S31), and if the determination result is no, executes steps S30 and S31. On the other hand, when another new small group starts communication, the individual master promoted to the general master determines whether or not the small group belongs to the large group performing communication (step S32). . Here, when belonging to the large group, the general master permits simultaneous communication to the small group belonging to the large group (step S33). Thereafter, the process returns to step S31.

  Further, when it does not belong to the large group in step S32, it is determined whether there is no interference with all of the small groups performing communication based on the availability information in Table 1 or Table 2 above (Step S34). ). Here, when there is no interference, simultaneous communication is permitted to a small group belonging to a large group different from the small group that is already communicating (step S33). On the other hand, when it interferes with at least one small group that is already communicating, time division communication is performed for each large group (step S35).

  Subsequently, the general master determines whether or not there is a small group that has stopped communication (step S36), and if there is no small group, repeats steps S35 and S36. On the other hand, if there is a small group that has stopped communication, the general master determines whether a plurality of large groups are communicating at that time (step S37). Here, when the plurality of large groups are no longer communicating, the simultaneous communication of the small groups performing communication is permitted (step S33). On the other hand, if a plurality of large groups are still in communication, the general master determines whether there is signal interference in the small groups between different large groups (step S38). Here, the general master continues the time division communication for each large group when there is interference (step S35), and permits simultaneous communication when there is no interference (step S33).

  According to the process of pattern 2 described above, the case where simultaneous communication is permitted individually as a small group while the process of performing communication in a time division manner for each large group by the large group setting function is provided. Communication time is further secured, and the communication speed is improved.

It is a connection diagram (1/2) which shows the some network group constructed | assembled by power line communication. It is a connection diagram (2/2) which shows the some network group constructed | assembled by power line communication. It is a block diagram which shows an example of the internal circuit structure regarding power line communication in a modem. It is a figure which shows an example of the topology comprised by the modems A-I of FIG. It is the figure which simplified the structure shown in FIG. 1, FIG. 2, and showed only the presence of the network group with respect to a low voltage distribution line (when a signal interferes between adjacent groups). It is the figure which simplified the structure shown in FIG. 1, FIG. 2, and was only the figure which showed existence of the network group with respect to a low voltage distribution line (when signal interference arises to two adjacent groups). It is a flowchart which shows the setting of a large group, and a time division process. It is a flowchart which shows a process when several large groups already exist. 9 is a flowchart showing processing different from those in FIGS.

Explanation of symbols

1-6 Network Group 9 Low Voltage Distribution Line 91-96 Indoor Distribution Line A-R Modem (Power Line Communication Device)
X, Y, Z large group

Claims (4)

One of the power line communication devices provided in each of a plurality of network groups having a distribution line branched from a common electrical path as a signal transmission path,
A large group setting function for defining one or more large groups as a whole by defining one network group or a plurality of network groups that do not cause signal interference with each other as belonging to one large group;
A power line communication apparatus comprising: a management function that permits simultaneous communication to each network group in the same large group and allocates communication time to all large groups by time division. One of the power line communication devices provided in each of a plurality of network groups having a distribution line branched from a common electrical path as a signal transmission path,
A large group setting function for defining one or more large groups as a whole by defining one network group or a plurality of network groups that do not cause signal interference with each other as belonging to one large group;
An information acquisition function for acquiring whether or not simultaneous communication is possible without causing signal interference in any combination between network groups; and
Simultaneous communication is permitted for network groups that belong to a large group that is different from all network groups that are already communicating, allowing simultaneous communication to each network group in the same large group. And a management function for allocating communication time by time division to all large groups when the availability information is NO. A power line communication method using a power line communication device provided in each of a plurality of network groups having a distribution line branched from a common electric circuit as a signal transmission line,
One of the power line communication devices serves as a management device, and a network group or a plurality of network groups that do not cause signal interference with each other are determined to belong to one large group. A large group of
The power line communication method, wherein the management device permits simultaneous communication to each network group in the same large group, and allocates communication time to all large groups by time division. A power line communication method using a power line communication device provided in each of a plurality of network groups having a distribution line branched from a common electric line as a signal transmission line,
By defining one of the power line communication devices as a management device and defining one network group or a plurality of network groups that do not cause signal interference with each other as belonging to one large group, one or more as a whole A large group of
The management device acquires whether or not simultaneous communication is possible without causing signal interference in any combination between network groups,
The management device permits simultaneous communication to each network group in the same large group, and the availability information is possible for a network group belonging to a large group different from all network groups that are already communicating. A power line communication method characterized in that simultaneous communication is permitted when it is, and communication time is allocated to all large groups by time division when the availability information is negative.

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