JP4889971B2 - Power line carrier communication system, communication method, communication apparatus - Google Patents

Description

  The present invention relates to a power line carrier communication technique in which a communication device in a home uses a power line in the home to communicate with another communication device in the home or a communication device outside the home.

There are two types of power line carrier communications that use power lines (generally referred to as power lines) that use 150 kHz to 450 kHz, and those that use 2 MHz to 30 MHz. In Japan, only devices that use the former frequency band are approved. Has been. In recent years, devices using the latter frequency band have been approved in the United States, and in Japan, the use conditions are currently being studied for approval. Since the communication device using the latter frequency band is capable of high-speed transmission, various uses have been proposed, and it is expected that it will spread in the future.
In addition, the following can be mentioned as patent documents currently disclosed about power line carrier communication, for example.

JP 2001-197146 A JP 2001-268045 A JP 2002-077099 A JP 2002-368831 A

By the way, there are various methods for communication devices using a power line. For example, there are ASK (Amplitude Shift Keying), FSK (Frequency Shift Keying), PSK (Phase Shift Keying), etc. as modulation schemes, and there are single carrier scheme and OFDM (Orthogonal Frequency Division Multiplexing) scheme as transmission schemes, A method such as a spread spectrum method is also used. If these specifications are different, they cannot communicate with each other. Communicate with each other if any one of the specifications, such as occupied bandwidth, subcarrier spacing, subcarrier modulation scheme, synchronization signal, coding scheme, access control scheme, data format, etc., is different even in the same OFDM scheme I can't.
In this way, in power line carrier communication, when devices of different systems that cannot communicate with each other exist in the same home, the transmission signals of both cause a collision and a communication failure occurs. In the worst case, a situation occurs in which both cannot communicate at all. When power line communication systems become widespread in the future, coexistence problems between communication devices are expected to become prominent.

Here, the reason why it is difficult to apply the following (1) to (3) as the conventional wireless communication technology for coexisting communication apparatuses having different communication methods in the same network to the power line carrier communication as it is. These will be described in order.
(1) Coexistence using carrier sense (2) Coexistence by frequency division (3) Coexistence by time division

(1) Coexistence using carrier sense In communication using carrier sense, each communication device observes the transmission path before transmission and confirms that no other communication device is transmitting from the received power level. Send.
However, in a power line carrier communication system, each communication device is designed to communicate by avoiding noise generated by home appliances, amateur radio and shortwave broadcast signals in terms of frequency or time, and an environment with a very small SN ratio. We are communicating with. Furthermore, the power line is a transmission line that has many branches and impedance cannot be matched, and the frequency characteristics at the reception point are complicated.
Therefore, it is difficult to determine the presence / absence of a communication apparatus of a different method by simple carrier sense such as the received signal level. The wireless LAN (IEEE 802.11) employs a method of detecting each other's preamble in order to improve the accuracy of carrier sense, but it cannot be used between devices of different systems.

(2) Coexistence by frequency division Coexistence by frequency division is a method in which collision of transmission signals of each communication device is avoided by making the frequency band used by each communication device different and coexist without interfering with each other.

FIG. 1 shows an in-house system configuration in power line carrier communication.
In FIG. 1, a plurality of lamp lines are wired from the distribution board 10, and various household appliances such as an outlet and a lighting device are connected to each lamp line. In FIG. 1, lamp lines 11 and 12 are taken out from the distribution board 10. Communication devices 13, 14, and 17 are connected to the power line 11. In addition, communication devices 15, 16, and 18 are connected to the power line 12. In the system shown in FIG. 1, the communication devices 13 and 14 are devices of the same communication method, and the communication devices 15 and 16 and the communication devices 17 and 18 are devices that adopt different communication methods. In such a case, communication is possible between the communication device 13 and the communication device 14, between the communication device 15 and the communication device 16, and between the communication device 17 and the communication device 18, but different combinations of communication methods, for example, the communication device 13 Communication between the communication device 15 and the communication device 15 is not possible. In a situation where there are a plurality of communication apparatuses having different communication methods, there is a possibility that transmission signals on the power line collide.

When the coexistence method by frequency division is applied to the power line carrier communication system in the house shown in FIG. 1, for example, as shown in FIG. 2, the frequency used by the communication device 13 and the communication device 14, and the communication device 15 The communication band is allocated so that the frequency used by the communication device 16 and the frequency used by the communication device 17 and the communication device 18 do not overlap each other.
The transmission power is reduced by about 40 to 50 dB at a frequency that is sufficiently away from each communication band, but leakage between signals transmitted from each communication device cannot be sufficiently reduced between adjacent frequency bands. As illustrated in FIG. 3, it is common to reduce mutual interference by providing a band gap.

However, since signal attenuation in power line carrier communication is often 50 dB or more, it cannot be distinguished whether it is an out-of-band leakage signal or an attenuation signal. Cannot prevent signal interference.
This point will be specifically described with reference to the in-home power line carrier communication system shown in FIG.

In the power line carrier communication system shown in FIG. 4, the communication device 13 and the communication device 15 are installed in the same outlet or a very close place.
In FIG. 4, the lamp wires 11 and 12 are drawn from the distribution board 10. Communication devices 13, 14, 15 are connected to the power line 11. The communication devices 13 and 15 are connected to the same outlet 19. On the other hand, a communication device 16 is connected to the power line 12. Since the communication device 15 and the communication device 16 communicate via the distribution board, the transmission distance is long and the signal passes through many branches, so that the signal attenuation is large. Further, since the communication device 13 exists near the communication device 15, the transmission signal from the communication device 13 is received very strongly by the communication device 15.
At this time, the received power level of the signal from the communication device 13 and the signal from the communication device 16 received by the communication device 15 is shown in FIG. As shown in FIG. 5, since the attenuation of the signal from the communication device 16 is large, the reception level of the signal in the communication device 15 is almost the same as the out-of-band leakage power level of the transmission signal of the communication device 13, and the communication It becomes difficult for the device 15 to correctly receive the signal from the communication device 16.
As a countermeasure, it may be possible to provide a filter that further reduces out-of-band leakage power, but the communication frequency may be changed depending on the combination of communication devices, and the communication bandwidth may be changed depending on the transmission speed. A bandpass filter with variable frequency and bandwidth is required for each communication, which is not practical.

(3) Coexistence by time division Coexistence by time division is a method of allowing each communication apparatus to coexist by changing the timing at which signals are transmitted. In the power line carrier communication system shown in FIG. 1, in the coexistence method using time division, for example, as shown in FIG. 6, the transmission signals from the communication devices 13 to 18 are prevented from overlapping in time.
In the method of coexistence by time division, each communication device can stop the output almost completely when it does not transmit itself, and there is almost no interference due to each other's signal. An access control device for arbitration is required, and there is a problem that it is difficult to implement this in all homes in a short period of time.
This point will be described with reference to the power line carrier communication system shown in FIG.

The power line carrier communication system shown in FIG. 7 is different from the system shown in FIG. 1 only in that an access control device 20 is added. That is, as in the system of FIG. 1, communication is possible between the communication device 13 and the communication device 14, between the communication device 15 and the communication device 16, and between the communication device 17 and the communication device 18, but different combinations of communication methods. For example, communication cannot be performed between the communication device 13 and the communication device 15 and between the communication device 15 and the communication device 17.
In FIG. 7, an access control apparatus 20 is an apparatus that instructs at what timing each communication apparatus transmits, and has an arbitration function for allowing each communication apparatus to coexist in a time division manner. If all the communication devices 13 to 18 adopt the same communication method, this access control function can be incorporated in one of the communication devices 13 to 18 (master unit). In order to allow communication devices of different systems to coexist in a time-sharing manner, as shown in FIG. 7, the access control device 20 is provided on the network independently from each communication device. The access control device 20 needs to arbitrate the transmission request from each communication device and instruct the transmission timing to each communication device after supporting a plurality of communication methods. I must.
That is, the coexistence method based on time division is not impossible in principle as compared with the coexistence method based on frequency division, but the above-described access control device must be installed in each home and takes a long time to realize. .

  As described above, in the conventional power line carrier communication system, it is difficult to allow a plurality of communication apparatuses having different communication methods to coexist in the same network.

  In addition, although the said patent documents 1-3 are disclosing the power line carrier communication system which makes a low-speed communication apparatus and a high-speed communication apparatus coexist by frequency division in the same communication system, this technique solves the said subject. I can't. In addition, Patent Document 4 discloses a method for performing time-sharing control of a plurality of communication devices having different communication methods by a management processor corresponding to the access control device. A method for generating a reference timing for performing the division is not disclosed.

The above-described problem becomes even more prominent when communication apparatuses that cannot coexist each perform bandwidth guaranteed communication. Bandwidth-guaranteed communication is communication that needs to maintain a constant transmission rate.
FIG. 8 schematically shows an example of communication by a communication apparatus installed in a house, which is built in a TV (Television), a PC (Personal Computer), or the like and performs communication via a power line. In FIG. 8, for example, real-time transmission such as transmission of image data from a video server (Video Server) to a TV (COM1), transmission of audio data from an audio server (Audio Server) to an audio device (Audio) (COM2), etc. Corresponds to guaranteed communication.
Unlike best-effort communication that does not need to maintain a constant transmission speed, such as downloading content, in bandwidth-guaranteed communication, when signals sent by multiple communication devices that perform bandwidth-guaranteed communication collide on the power line, Recovery methods such as data retransmission cannot be taken. In FIG. 8, this signal collision is visually recognized by the user as, for example, image disturbance on the TV.

  In the above description, the coexistence within the same network in the home has been mentioned, but the coexistence of communication devices may be a problem for communications performed in adjacent houses.

FIG. 9 is a diagram illustrating a system configuration of a power line carrier communication system performed in each of two adjacent houses.
In FIG. 9, distribution boards 102 and 104 are attached to houses 107 and 108, respectively. The distribution boards 102 and 104 are connected to a common outdoor transformer 100 via low-voltage distribution lines 101 and 103, respectively. The outside transformer 100 is supplied with power from a power plant (not shown) through the intermediate voltage distribution line 106 together with other outside transformers 105. In the house 107, power line carrier communication is performed between the communication devices 21_1 and 21_2, and in the house 108, power line carrier communication is performed between the communication devices 22_1 and 22_2.
Actually, unlike the diagram illustrated in FIG. 9, not only two houses from one out-of-home transformer 100 but also a few to ten or so houses are usually supplied with commercial power using low-voltage distribution lines. Supplied.

  In FIG. 9, since the transmission signal by the power line carrier communication performed in each house of the houses 107 and 108 is attenuated by the low voltage distribution lines 101 and 103, the distribution boards 102 and 104, a power meter (not shown), etc., For example, it is considered that the signal transmitted from the communication device 21_1 in the house 107 has little effect on the power line carrier communication system in the house 108, but communication between one house is close between adjacent houses such as an apartment house. There is a possibility that a signal from the device leaks into another house and collides with a signal transmitted by a communication device in another house.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a power line carrier communication system, a communication method, and a communication device therefor in which communication by a plurality of communication devices coexists. There is.

In order to overcome the above-described problems, the power line carrier communication system according to the first aspect of the present invention includes a plurality of sets of first communication devices that can be commonly connected to a power line. A power line carrier communication system having a plurality of sets of first communication devices that communicate data within a set and cannot communicate with each other , wherein the plurality of sets of first communication devices include: the reference timing synchronized with the period of the commercial power supply voltage supplied to the power line includes a first communication apparatus that changes in signal power due to data communication Te said power line smell has a first timing generator for determining when not detected , out of said plurality of communication sections dividing the interval of the reference timing synchronized with the period of the commercial power supply voltage, by using the communication section immediately after the reference timing data Communicating, first communication device of the first set, the data immediately following the in the detection process of the reference timing, the commercial power source each candidate timing for a plurality of candidate timings corresponding to a plurality of phase angle of the voltage input A change in signal power due to transmission is detected, and among the plurality of candidate timings, a candidate timing at which the change in signal power due to data transmission is detected most frequently after a predetermined number of times is determined as the first communication device of the first set Including a first communication device having a second timing generation unit that is set to a common reference timing used for its own communication control as a reference timing determined by one of the plurality of communication sections , immediately after the reference timing. data communication using a communication path other than the communication section, a first communication device of the second set, wherein the first communication of the first set of devices and Serial second set of the first communication apparatus using respective communication section executes the time-division data communication each set.

In order to overcome the above-described problems, the communication method according to the second aspect of the present invention includes a plurality of sets of first communication devices that can be connected in common to a power line, and each set is connected to the power line. in a communication method in the power line carrier communication system having a plurality of sets of the first communication device can not communicate data with each other between and other set communicate data, among the plurality of sets of the first communication device the first set of the first communication device, of the first communication apparatus of the first set, the first timing generator provided in either the first communication device, is supplied to the power line that a reference timing synchronized with the cycle of the commercial power supply voltage, the determined when the change in signal power due to the data communication is not detected in the power line, before Symbol of the reference timing synchronized with the period of the commercial power supply voltage Of the plurality of communication sections dividing the interval, and the data communication using the communication section immediately after the reference timing, among the plurality of sets of the first communication device, the first communication device of the second set, Among the second communication devices of the second set, a plurality of the commercial power supply voltages input in the reference timing detection process by the second timing generator provided in any of the first communication devices. For a plurality of candidate timings corresponding to the phase angle, a change in signal power due to data transmission immediately after each candidate timing is detected, and among the plurality of candidate timings, the change in signal power due to data transmission is the highest at a predetermined number of times or more. Many detected candidate timings are set to a common reference timing used for own communication control as a reference timing determined by the first communication device of the first set. Of the plurality of communication sections, and the data communication using the communication section other than immediately after the communication section of the reference timing, the first set of the first communication apparatus and the first communication device of the second set The data communication for each set is executed in a time-sharing manner using each communication section .

In order to overcome the above problems, a communication device according to the third aspect of the present invention is a time-division data communication with another set of communication devices when connected to the same power line together with another set of communication devices. To detect data communication reference timing synchronized with the cycle of the commercial power supply voltage supplied to the power line. A timing generation unit that performs the data communication, and the timing generation unit corresponds to a plurality of phase angles of the input commercial power supply voltage in the reference timing detection process. A change in signal power due to data transmission of the other set of communication devices immediately after each candidate timing is detected, and among the plurality of candidate timings, data If the change in signal power due to transmission is the most often detected candidate timing a predetermined number of times or more, the candidate timing, as a reference timing determined by the other set of communication devices, used in its own communication control When the common reference timing is set and no change in signal power due to data transmission of the other set of communication devices is detected , the reference timing is determined so as to be synchronized with the cycle of the commercial power supply voltage, and the communication unit When the reference timing is determined by the timing generation unit, the ones in the same set using the communication section immediately after the reference timing among the plurality of communication sections dividing the reference timing interval a data communication, when the reference timing by the other set of communication devices by the timing generation unit is detected, the plurality of To determine the period being used of the signal interval, the same set in using the communication section than the communication section immediately after the reference timing at which the reference timing other set of communication devices determines to use Communicate data with things.

In order to overcome the above-described problems, a communication device according to a fourth aspect of the present invention is a time-division data communication with another set of communication devices when connected to the same power line together with another set of communication devices. Is a communication device that performs data communication with a device in the same group and does not perform data communication with another group, and is synchronized with a cycle of a commercial power supply voltage supplied to the power line. the commercial and timing generator for detecting a reference timing of communication that has been determined, has a communication unit that performs the data communication, the timing generation unit, in the detecting process of the reference timing, which is input by For a plurality of candidate timings corresponding to a plurality of phase angles of the power supply voltage, a change in signal power due to data transmission of the other set of communication devices immediately after each candidate timing is detected. Among the plurality of candidate timings, when there is a candidate timing at which the change in signal power due to data transmission is detected most frequently at a predetermined number of times, the candidate timing is determined based on the reference determined by the other set of communication devices The timing is set to a common reference timing used for own communication control, and the communication unit detects the reference timing interval when the timing generation unit detects a reference timing by the other set of communication devices. to determine the period being used among a plurality of communication sections dividing the, using communication section other than immediately after the communication section of the reference timing at which the reference timing other set of communication devices determines to use and those data communication in the same set in Te, among reference timing is detected by the other set of communication devices by the timing generator When the can, using all of the plurality of communication sections, ones the data communication in the same group within.

  ADVANTAGE OF THE INVENTION According to this invention, when a some communication apparatus performs power line carrier communication, the communication by each communication apparatus can coexist.

  Several embodiments of the present invention will be described below with reference to the accompanying drawings.

<< First Embodiment >>
In the power line carrier communication system according to the present embodiment, a plurality of modems as one embodiment of the communication apparatus of the present invention are connected to a home power line. In order to prevent the transmission signal from the modem from colliding on the power line, the transmission section of the modem is set by time division.
Because of the setting of the transmission section by time division, each modem generates a reference timing for performing the time division processing based on the commercial power supply voltage in the power line, or the reference timing is notified, or The reference timing is acquired by detecting the reference timing.
In the following description, “section” is used synonymously with “period”.

[System configuration]
First, the structure which concerns on one Embodiment of the power line carrier communication system of this invention is demonstrated.
FIG. 10 shows a system configuration of the power line carrier communication system 1 installed in a home.
In FIG. 10, a plurality of electric wires are wired from the distribution board 10, and various electric home appliances such as an outlet and a lighting device are connected to each electric wire. In FIG. 10, the electric lamp wires 11 and 12 are taken out from the distribution board 10. The power lines 11 are connected to modems 30_1 to 30_3. Further, modems 30_4 to 30_6 are connected to the power line 12.

In general, in power line carrier communication in a home, two types of communication, “bandwidth guaranteed communication” and “best effort communication”, are performed as communication types.
“Band-guaranteed communication” is communication that needs to maintain a constant transmission speed, that is, communication that should guarantee the transmission speed. For example, transmission of image data to a TV set, real-time transmission of music transmission speed, etc. Corresponds to this.
“Best-effort communication” refers to communication that does not require a constant transmission rate, that is, communication that does not require a guaranteed transmission rate. For example, real-time download such as e-mail and web information, content download, etc. Communication that does not require security is included. Best-effort communication is a method that communicates by sharing a limited bandwidth, so if there are many modems that perform best-effort communication, the effective speed of communication decreases, but for communication collisions, In many cases, it is acceptable by retransmitting data.

  Note that there are various types of modems that perform only one of bandwidth-guaranteed communication or best-effort communication, and modems that perform both of them, so in the following description, they are referred to as "bandwidth-guaranteed modem" and "best-effort modem". . Therefore, even a single modem may function as a “bandwidth guarantee type modem” or may function as a “best effort type modem”.

In FIG. 10, the modems 30_1 to 30_4 are band-guaranteed modems, which perform communication between the modems 30_1 to 30_2 and perform communication between the modems 30_3 to 30_4. In addition, the modems 30_5 and 30_6 are best-effort modems and perform communication.
As described above, the power line carrier communication system 1 shown in FIG. 10 is an example of a system in which band-guaranteed communication is performed between a plurality of sets of modems.

In general, a bandwidth guarantee type modem is roughly classified into a “control modem (control device)” or a “controlled modem (control device)”. The control modem is a so-called parent device, and mainly operates in bandwidth guaranteed communication with the child device. The controlled modem is a so-called slave unit, and operates passively in band-guaranteed communication with the master unit. In some cases, a bandwidth-guaranteed modem can be either a controlled modem or a controlled modem depending on the communication status.
In this embodiment, the control modem generates the reference timing based on the commercial power supply voltage on the power line, and the controlled modem is notified of the reference timing from the control modem or the reference timing generated by the control modem is used. To detect.

  In the power line carrier communication system 1, in order to allow communication by the plurality of band-guaranteed modems 30_1 to 30_4 and the best-effort modems 30_5 and 30_6 to coexist, the previous section is the best-effort type with reference timing based on the commercial power supply voltage as a boundary. A fixed reference interval is set in each modem, with the communication and the subsequent interval being band-guaranteed communication. The subsequent section is time-divided according to the number of modems that perform band-guaranteed communication, and different band-guaranteed communication is performed for each divided communication section. As a result, in the power line carrier communication system in the home, a plurality of bandwidth-guaranteed communications and best effort communications are allowed to coexist.

[Modem configuration]
Next, the configuration of each modem 30_1 to 30_6 of the power line carrier communication system 1 shown in FIG. 10 will be described.
FIG. 11 is a block diagram showing a configuration of the modem 30 according to the embodiment of the present invention. The modems 30_1 to 30_6 have the same configuration as the modem 30 shown in FIG.

In FIG. 11, transmission data received from an upper layer is input to a MAC (Media Access Control) layer processing unit 31 and transmitted / received via a PHY layer transmission processing unit 32, a D / A converter 33, an amplifier 34, and a filter 35. Input to the switching unit 36. The transmission / reception switching unit 36 passes the transmission signal in accordance with the transmission instruction signal Cs supplied from the MAC layer processing unit 31 and outputs the transmission signal to the power line via the coupler 37. At that time, the transmission signal is framed (frame signal) by the PHY layer transmission processing unit 32.
On the other hand, the signal received via the coupler 37 passes through the transmission / reception switching unit 36 when the transmission instruction signal Cs is not transmitted from the MAC layer processing unit 31, and the filter 38, the amplifier 39, the A / D converter 40, Data input to the MAC layer processing unit 31 via the PHY (Physical sublayer) layer reception processing unit 41 and correctly received are output to the upper layer.

  The coupler 42 includes a filter that extracts a commercial power supply voltage from a signal on the power line. Since the power line communication system 1 performs communication by superimposing a signal on the commercial power supply voltage, the coupler 42 removes the signal and extracts the commercial power supply voltage signal S42.

  The timing generation unit 43 takes the reference timing by taking the timing of the zero crossing point of the AC signal S42 extracted by the coupler 42, or notifies the reference timing or detects the reference timing. The reference timing is acquired and the reference timing signal TGref is generated. A method for acquiring the reference timing will be described later.

The timing generation unit 43 sets a reference interval with a constant interval based on the reference timing, and sets its own transmission interval within the reference interval. Then, according to the set transmission interval, a transmission timing signal TGsd is generated and supplied to the MAC layer processing unit 31.
Details of the configuration of the timing generation unit 43, a reference section setting method, and a transmission section setting method will be described later.
In the MAC layer processing unit 31, the transmission / reception switching unit 36 is controlled by the transmission instruction signal Cs based on the transmission timing signal TGsd from the timing generation unit 43. As a result, the transmission signal is transmitted in the transmission section set by the timing generation unit 43.

  Note that the configuration of the modem 30 shown in FIG. 11 may be different. For example, the coupler 42 and the timing generation unit 43 can be externally attached. In general, a transmission / reception circuit in a modem is often mounted on a single chip. However, with this external configuration, a conventional modem can be easily modified to the configuration of the modem 30.

[Reference timing acquisition method]
Next, a reference timing acquisition method performed by the timing generation unit 43 of the modem 30 will be described with reference to FIGS.
As described above, the reference timing signal TGref is a signal for appropriately setting time division of transmission timing so that data transmitted by a plurality of modems do not collide with each other on the power line. In order to perform this time division setting, it is assumed that a common reference timing is set for all modems.
In the power line carrier communication system 1 according to the embodiment, each modem (1) generates a reference timing itself, (2) is notified of the reference timing, or (3) is detected by detecting the reference timing. Timing is acquired and a reference timing signal TGref is generated.
Hereinafter, the reference timing acquisition methods (1) to (3) will be described in order.

(1) Generation of Reference Timing Among the band-guaranteed modems in the power line carrier communication system 1 according to the present embodiment, the control modem generates the reference timing signal TGref using the AC cycle of the commercial power supply voltage.

In commercial power supplies in Japan and the United States, a single-phase three-wire AC voltage having a frequency of 50 Hz to 60 Hz is usually used. In many other areas, the three-phase AC type is used.
In this embodiment, the reference timing signal TGref is generated in synchronization with the zero cross timing (zero cross point) of the commercial power supply voltage. Various variations can be considered as to whether to divide and take the reference timing, or to take the reference timing by making a time offset with respect to the zero-cross timing.

As a variation including dividing the timing of the zero cross, when the commercial power source is a single-phase three-wire AC voltage, the reference timing is n / m times (m, n: integer) of the phase angle of 180 degrees. In the case of a three-phase AC type AC voltage, the reference timing can be set to n / m times (m, n: integer) of a phase angle of 60 degrees.
That is, in the single-phase three-wire system, a zero cross point is generated every 180 degrees, and therefore, the timing of the zero cross point is first detected, and the timing is divided or selected to obtain a reference timing of n / m times 180 degrees. Take. In the three-phase AC type, since the three phases zero cross every 60 degrees, first, the timing of this zero crossing point is detected and the timing is divided or selected to obtain a reference timing of n / m times 60 degrees. .

Several examples of how to take the reference timing described above will be described based on specific waveforms.
FIG. 12 shows the position of the reference timing for various commercial power supply voltages. 12A shows a case where m = 1 and n = 2 in a single-phase three-wire system (360 degree intervals), and FIG. 12B shows a case where m = 2 and n = 3 in a single-phase three-wire system (270). (Degree interval), (c) when m = 1, n = 3 in the three-phase AC type (180 degree interval), and (d) when m = 2, n = 8 in the three-phase AC type (240 Degree intervals), and the reference timing is indicated by arrows.

In FIG. 12 (a), the reference timing is taken in synchronism with the zero-cross timing of the single-phase three-wire commercial power supply voltage at intervals of 360 degrees. In FIG. 12B, the zero-cross timing of the single-phase three-wire commercial power supply voltage at intervals of 540 degrees is taken, and the timing is divided to take the reference timing of 270 degrees.
In FIG. 12 (c), the reference timing is taken in synchronization with the zero crossing timing of 180 ° intervals of any one phase (A phase in the figure) of the three-phase AC commercial power supply voltage. In FIG. 12D, the reference timing is taken at 60 degrees × 4 (= 240 degrees) in the three-phase AC type.

In this way, the reference timing is taken, and a clock signal corresponding to the reference timing is generated as the reference timing signal TGref.
Note that m and n can be set so that an appropriate reference timing interval that can accommodate communication packets can be taken in consideration of the transmission speed of communication used in the power line carrier communication system 1, for example.

(2) Notification of reference timing The controlled modem in the band-guaranteed modem in the power line carrier communication system 1 according to the present embodiment obtains the reference timing by periodically receiving the reference timing from the control modem. You can also

(3) Detection of reference timing Among the band-guaranteed modems in the power line carrier communication system 1 according to the present embodiment, the controlled modem and the best effort modem detect the reference timing signal TGref by detecting the reference timing. Is generated. Therefore, in order for these modems to detect the reference timing, it is assumed that a bandwidth guarantee type modem as a control modem is already communicating at the time when communication is started.

As described above, if the bandwidth guarantee type modem as the control modem takes the reference timing at any timing when the zero cross occurs, or if the timing when the zero cross occurs is divided into the reference timing, When the modem is newly connected to the power line carrier communication system 1 (communication is started), the modem may not be able to take the reference timing only by observing the commercial power supply voltage. If the reference timing is an interval of 180 degrees in the case of a single-phase three-wire system and an interval of 60 degrees in the case of a three-phase AC, the reference timing is uniquely determined from the commercial power supply voltage. This is because, when the reference timing is set to the commercial power supply at an interval of 180 degrees, the modem newly connected to the power line cannot specify which zero-crossing timing generated at every phase angle of 60 degrees is the reference timing.
Therefore, the controlled modem and the best-effort modem specify the reference timing by observing signals transmitted by the control modem in communication sections before and after the reference timing.

Hereinafter, a reference timing detection method will be described based on a specific example.
FIG. 13 is a diagram for explaining a reference timing detection method, in which (a) is a waveform of a commercial power supply in a single-phase three-wire system, (b) is a power level (reception level) of a signal received by a modem, Indicates.
In FIG. 13A, as reference timing candidates, for example, reference timing candidates RC1 to RC4 corresponding to phase angles of 0 degrees, 180 degrees, 360 degrees, and 540 degrees are assumed, and the reference timing is identified (detected) from these. The

In the power line carrier communication system 1 according to the present embodiment, since the control modem performs transmission after the reference timing, a large change in signal power accompanying the start of data transmission is observed on the power line immediately after the reference timing. Therefore, the reference timing can be detected by detecting the change in the signal power.
However, since there is no guarantee that data transmission is always performed immediately after the reference timing, detection is performed for a certain time or a plurality of times, and the most likely timing among the four reference timing candidates RC1 to RC4 is specified as the reference timing. Therefore, it is necessary to improve the detection accuracy.

FIG. 14 is a flowchart for detecting the reference timing.
The flowchart shown in FIG. 14 assumes that the timing generation unit 43 includes a plurality of counters C (i) (i: 1 to N, N = 3 in the example shown in FIG. 13) corresponding to each reference timing candidate. Yes.

  Steps ST3 to ST6 indicate that transmission of data at the reference timing candidate is started based on a change in power of the signal received before and after each reference timing candidate (detection that the signal power exceeds a predetermined threshold). This is a process of incrementing the corresponding counter C (i) (i = 1 to N) when it is determined.

Each time the processes of steps ST3 to ST6 are completed once, it is determined whether or not a predetermined time has elapsed (step ST2). When the predetermined time has elapsed, the processes of steps ST3 to ST6 are not performed. Then, the counter C (i) (i = 1 to N) having the maximum count value (max {C (i)}) is specified, and the maximum count value is larger than a predetermined threshold value _CTH. As a condition (step ST8), a corresponding reference timing candidate is determined as a reference timing (step ST9). Thereby, the timing at which the most data transmission is detected is detected as the reference timing.
For example, in the example shown in FIG. 13B, it is determined that the data transmission is performed immediately after the times t1 to t4, and the reference timing candidate RC2 is determined as the reference timing by detecting the number of times of the data transmission. The
In step ST8, the calculated maximum count value is compared with the threshold value C _TH , although the count value is expected to be a large value of about 100 at the maximum according to the time specified in step ST2. This is because, when the calculated maximum count value is a small value of about 1 to 10, for example, it is not appropriate to specify the reference timing with the maximum count value.

Instead of detecting a change in signal power, conversely, the plurality of counters C (i) detect and count that there is no change in signal power, and finally correspond to the counter with the smallest count value. The reference timing candidate can also be determined as the reference timing.
In addition, it is impossible to specify the reference timing when data transmission is not performed at all. However, in the case of a band guarantee type modem, a beacon signal may be periodically transmitted. Even when this is not performed, the reference timing can be determined by using the timing of the beacon signal.

In the case of a three-phase AC type commercial power supply, since the three-phase signal zero-crosses every 60 degrees, for example, 12 reference timing candidates with phase angles of 0 degrees, 60 degrees, 120 degrees,. can do. In this case, 12 counters are required.
In addition, when the reference timing is generated by dividing the timing of the zero cross point of the commercial power supply (in the case of a single-phase three-wire system, it is n / m times 180 degrees and n <m), the reference timing is used. Since the timing does not coincide with the zero cross point, a reference timing candidate is assumed by observing a periodic change in the received signal power, and the reference timing is specified by performing statistical processing.

[Configuration of Timing Generation Unit 43]
Next, the configuration of the timing generation unit 43 for executing the above-mentioned [reference timing acquisition method] will be described with reference to the block diagram of the modem 30 shown in FIG.

The reference timing generation unit 433 is an embodiment of the timing acquisition unit of the present invention.
The transmission timing generation unit 434 is an embodiment of the section setting unit, the first power detection unit, the first communication setting unit, and the second communication setting unit of the present invention.

As illustrated in FIG. 11, the timing generation unit 43 includes a reference timing candidate generation unit 431, a received power measurement unit 432, a reference timing generation unit 433, and a transmission timing generation unit 434.
Based on the output S42 of the coupler 42, the reference timing candidate generation unit 431 generates a reference timing candidate (timing signal TGrc) synchronized with the zero cross point of the commercial power supply and sends it to the received power measurement unit 432.

  The reception power measuring unit 432 includes a plurality of counters C (i) (i = 1 to N) corresponding to timing signals TGrc indicating reference timing candidates (N). The reception power measurement unit 432 measures the signal power of the reception signal S41 supplied from the PHY layer reception processing unit 41 for a predetermined period, and detects that the signal power exceeds a predetermined threshold with the reference timing candidate as a boundary. Each time the counter is incremented, the value of each counter (count signal S_C (i) (i = 1 to N)) is sent to the reference timing generator 433 after the predetermined period has elapsed. That is, in the received power measuring unit 432, processing corresponding to steps ST1 to ST6 is performed in the flowchart shown in FIG.

In the reference timing generation unit 433, the maximum value among a plurality of counter values corresponding to each reference timing candidate transmitted from the reception power measurement unit 432 is specified, and the maximum count value is a predetermined threshold value C _TH. If the reference timing candidate is exceeded, the corresponding reference timing candidate is specified as the reference timing, and the reference timing signal TGref is output. That is, in the reference timing generation unit 433, processing corresponding to steps ST7 to ST9 is performed in the flowchart shown in FIG.
For example, when the reference timing cannot be specified such as when the count values of all the counters are small, a predetermined signal indicating that the reference timing could not be specified is sent to the transmission timing generation unit 434.

Note that the processing of the reference timing generation unit 433 described above is processing in the case where itself is a controlled modem or a best effort type modem.
When itself operates as a control modem, processing based on the counter value is not performed, and the timing signal TGrc is obtained from the reference timing candidate generation unit 431 by bypassing the reception power measurement unit 432 as shown in FIG. And generate a reference timing by itself.

When the modem 30 is a bandwidth-guaranteed modem, the transmission timing generation unit 434 determines whether it operates as a control modem or a controlled modem, and notifies the reference timing generation unit 433 with the control signal Cop. As a result, the reference timing generation unit 433 performs an operation corresponding to either the control modem or the controlled modem.
For example, the transmission timing generation unit 434 acquires the reception signal S41 from the PHY layer reception processing unit 41, and whether there is a change in the signal power of the reception signal S41 immediately after the reference timing specified (detected) by the reference timing generation unit 433. If there is no change, the control signal Cop can be switched so that it operates as a control modem. As a result, it can operate as a controlled modem halfway, and when it is no longer in control modem, it can switch itself to the control modem and operate.

  When the modem itself is a controlled modem and receives a reference timing notification from the control modem, the transmission timing generation unit 434 receives the notification from the PHY layer reception processing unit 41.

  Further, the transmission timing generation unit 434 sets a reference interval TGref based on the reference timing signal TGref supplied from the reference timing generation unit 433, sets a transmission interval from the reference interval TGref, and transmits the transmission timing signal TGsd. Is sent to the MAC layer processing unit 31. The section length of the reference section TGref is defined in advance by the system.

When the modem itself is a best effort type modem, the previous section (fixed period) with the reference timing as a boundary is set as its own transmission section in the reference section TGref.
If the modem itself is a band-guaranteed modem, the section (fixed period) after the reference timing is set as its own transmission section in the reference section TGref. In the power line carrier communication system 1 (FIG. 10), Since there are two sets of band-guaranteed modems, this subsequent section is set in half. For example, the modems 30_1 and 30_2 set the first half of the rear section as their own transmission section, and the modems 30_3 and 30_4 set the second half of the rear section as their own transmission section.
Details of the method of setting the transmission section will be described later.

[Reference timing setting operation]
Next, the operation in which the modem 30 specifies and sets the reference timing will be described for each modem type with reference to the flowcharts of FIGS. 11 and 15 to 18.

(1) Control modem (bandwidth guaranteed modem)
FIG. 15 is a flowchart showing the reference timing setting operation in the control modem.
The control modem itself generates a reference timing after startup (step ST10). That is, in the timing generation unit 43, the reference timing generation unit 433 determines the reference timing based on the timing signal TGrc indicating the reference timing candidate generated from the reference timing candidate generation unit 431.
Further, the control modem notifies the controlled modem of the reference timing generated by itself (step ST11) at regular intervals (step ST12).

(2) Controlled modem (bandwidth-guaranteed modem)
The controlled modem is notified of the reference timing from the control modem or performs an operation of detecting the reference timing.

(2-1) Reference Timing Notification FIG. 16 is a flowchart showing the reference timing notification / setting operation in the controlled modem.
In this case, if the controlled modem receives the reference timing from the control modem after activation (step ST13), the reference timing generation unit 433 of the controlled modem sets the received reference timing (step ST14). ) To generate a reference timing signal TGref.

(2-2) Reference Timing Detection FIG. 17 is a flowchart showing the reference timing detection / setting operation in the controlled modem.
In this case, the controlled modem detects the reference timing after activation (step ST15). That is, in the timing generation unit 43, the received power measurement unit 432 measures the number of rising times of the received power before and after the reference timing candidate, and the reference timing generation unit 433 detects the reference timing candidate having the maximum number of rising times as the reference timing. ·Identify. If the reference timing cannot be detected (step ST16), the process of step ST15 is repeated. Then, the detected reference timing is set (step ST17), and a reference timing signal TGref is generated.

(3) Switching from Control Modem to Controlled Modem FIG. 18 is a flowchart showing the reference timing setting operation when switching from the control modem to the controlled modem.
In a modem that is a bandwidth-guaranteed modem and can be either a control modem or a controlled modem, the reference timing setting method is changed as appropriate according to whether or not the reference timing can be detected.
When such a modem starts operating as a controlled modem, first, a reference timing is detected (step ST18). That is, in the timing generation unit 43, the received power measurement unit 432 measures the number of rising times of the received power before and after the reference timing candidate, and the reference timing generation unit 433 detects the reference timing candidate having the maximum number of rising times as the reference timing. ·Identify. If the reference timing can be detected (step ST19), the detected reference timing is set (step ST20), and the reference timing signal TGref is generated.
When the reference timing cannot be detected (step ST19), the transmission timing generation unit 434 (see FIG. 11) determines whether or not to switch to the control modem (step ST21). In the case of switching to the control modem, the control signal Cop is switched so that it operates as a control modem, and the reference timing generation unit 433 accordingly responds based on the reference timing candidate acquired from the reference timing candidate generation unit 431. A reference timing is generated (step ST22).

(4) Best effort type modem The best effort type modem performs the same reference timing setting operation as (2-2) detection of the reference timing of the controlled modem.

[Transmission section setting method]
Next, the setting of the transmission section according to the reference timing will be described.
As described above, in the transmission timing generation unit 434 (see FIG. 11), a reference section having a fixed section before and after the reference timing is set in advance, and each modem in the power line carrier communication system 1 is included in the reference section. Set own transmission interval.

FIG. 19 is a timing chart showing an example of setting a transmission section based on the reference timing, where (a) is a commercial power supply and reference timing, (b) and (c) are section division timing examples, and (d) is a transmission section. An example of setting is shown.
When the reference timing is set as shown in FIG. 19A, there are two possible division methods between the reference timings for assigning transmission intervals. One is a method of dividing a reference timing by a zero cross point as shown in FIG. The other is a method of dividing the reference timing by a fixed number (8 divisions in FIG. 19C) as shown in FIG. 19C.
FIG. 19 (d) shows an example of setting the transmission interval when the reference timing is divided into eight as shown in FIG. 19 (c). In FIG. 19, a reference section Tref having an adjacent reference timing interval as a section length is set. This reference section Tref is a section A having a period length of (1/8) Tref, for example, as a preceding section of the reference timing. As a subsequent section, for example, a section B having a period length of (7/8) Tref is configured.

In the following description, in the reference section, a previous section (transmission section) with the reference timing as a boundary is referred to as section A, and a rear section (transmission section) with the reference timing as a boundary is referred to as section B as appropriate.
In the power line carrier communication system 1 according to the present embodiment, the best effort type communication is assigned to the section A, and the bandwidth guarantee type communication is assigned to the section B. Although the ratio (section length) between the sections A and B is constant, the section A to which the best effort type communication is assigned is set to be as small as about 1/8 to 1/10 of the reference section. This is because in best-effort communication, there is a method of reducing collision by randomly varying the transmission timing with a data length shorter than the transmission interval to be used, or a method of recovering by ACK communication even if a collision occurs. This is because collision of transmission signals can be tolerated to some extent. On the other hand, in band-guaranteed communication, transmission signal collisions are often fatal, so a transmission section that is as long as possible is secured.

  Next, a setting example of transmission sections of two band-guaranteed communications performed in the power line carrier communication system 1 (FIG. 10) will be described with reference to FIG. 20 and FIG.

  FIG. 20 is a timing chart showing an example of setting a transmission section, where (a) shows commercial power, (b) shows transmission section settings, and (c) shows frame transmission. FIG. 20 shows an example in which a reference section Tref having the same section length as the reference timing interval is set.

In FIG. 20, the reference timing is divided by a fixed number, section A is set according to the division unit, and the remaining section is set as section B. 20B, when the first half of the section B is the section B1 and the second half is the section B2, the communication between the modems 30_1 to 30_2, which is the band-guaranteed communication in the power line carrier communication system 1, Communication between the modems 30_3 to 30_4 is set in either the section B1 or B2. Then, as shown in FIG. 20C, frame transmission is performed from each modem within the set transmission interval.
At that time, as will be described later, among the two sets of band-guaranteed communication, the one that first starts communication uses the section B1, and the one that starts communication after that uses the section B2.

  FIG. 21 is a timing chart showing another setting example of the transmission section, where (a) shows the commercial power supply, (b) shows the setting of the transmission section, and (c) shows the frame transmission. FIG. 21 shows an example in which a reference section Tref having a section length longer than the reference timing interval is set. As described above, the section length of the reference reference section Tref does not need to match the adjacent reference timing interval.

  In FIG. 21, the reference section is divided for each zero cross point, section A is set according to the division unit, and the remaining section is set as section B. Then, as shown in FIG. 21 (b), if the first half of the section B (one cycle of commercial power) is the section B1, and the second half (one cycle of commercial power) is the section B2, the band in the power line carrier communication system 1 Communication between the modems 30_1 to 30_2 and communication between the modems 30_3 to 30_4, which are guaranteed communication, are set in either the section B1 or B2. Then, as shown in FIG. 21C, frame transmission is performed from each modem within the set transmission interval.

  As described above, in the power line carrier communication system 1, in the reference section specified by the reference timing, two band-guaranteed communications are allocated in time division to the section B that is the subsequent section with the reference timing as a boundary. Therefore, it is possible to avoid collision of transmission signals by different band-guaranteed communication on the power line, and two band-guaranteed communication can coexist.

[Specific transmission section setting for each modem]
Next, a method for setting its own transmission section performed by each modem in the power line carrier communication system 1 will be described. The following transmission interval setting method is executed by the transmission timing generation unit 434 (see FIG. 11).

(1) Band Guaranteed Type Modem Starting Communication Using First Half of Section B (Section B1) In the power line carrier communication system 1 according to the embodiment, there is a modem that detects a reference timing such as a best effort type modem. In order for this detection to be performed appropriately, it is desirable that the band-guaranteed modem in the system preferentially uses the first half of the section B (section B1). Therefore, in a situation where the bandwidth guarantee communication is not performed, the bandwidth guarantee modem that starts communication sets its own transmission section to the section B1. As a result, a best-effort modem that starts communication thereafter can specify the reference timing.
From this point of view, the band-guaranteed modem attempting to start communication first confirms whether or not the section B1 can be used. Specifically, when the transmission timing generation unit 434 (see FIG. 11) of this band-guaranteed modem determines that there is no modem communicating on the power line based on the received signal S41, The control signal Cop is switched so as to be a control modem. Thereby, the timing generation unit 43 determines the reference timing by itself.

FIG. 22 is a flowchart showing a preferable operation of the bandwidth guarantee type modem after determining the reference timing in this way.
The bandwidth-guaranteed modem starts communication using the section B based on the reference timing determined by itself (step ST30). That is, at this time, since no other bandwidth-guaranteed communication is performed, communication can be performed using all the sections of section B in which the ratio is defined in advance in the reference section.
The bandwidth-guaranteed modem that has started communication sequentially checks whether or not there is a bandwidth-guaranteed modem that enters (communication starts) using section B2 (step ST31). Since the start timing of the section B2 can be specified after setting the reference section, the transmission timing generation unit 434 checks the presence of another modem by detecting whether or not the reception signal S41 rises at that timing.
If it is determined that another modem using the section B2 has started communication, the communication is limited to the section B1 (step ST32).
As described above, the own communication period (transmission section) is sequentially adjusted, and the transmission timing signal TGsd corresponding thereto is output from the timing generation unit 43.

(2) Band-guaranteed modem that starts communication using the latter half of section B (section B2) As a result of checking whether or not the band-guaranteed modem that starts communication can use section B1, etc. If it is determined that there is a modem, the control signal Cop is switched so that the modem is the controlled modem. Thereby, the timing generation unit 43 determines the reference timing by detecting the reference timing.

FIG. 23 is a flowchart showing a preferable operation of the bandwidth guaranteed modem after the reference timing is determined in this way.
The bandwidth-guaranteed modem starts communication using the section B2 based on the determined reference timing (step ST40). That is, the second half start timing of the section B in which the ratio is defined in advance in the reference section is specified, and communication is performed between the sections B2.
Here, after the band-guaranteed modem starts communication using the section B2, the modem that performs communication using the section B1 may end the communication. As described above, in the power line carrier communication system 1 according to the embodiment, it is desirable that there is always a modem that performs communication using the section B1 immediately after the reference timing for the modem that detects the reference timing.
Accordingly, the bandwidth-guaranteed modem that performs communication using the section B2 sequentially checks whether or not there is a modem that uses the section B1 (step ST41). Use all sections to communicate. That is, the communication start timing is synchronized with the reference timing (step ST42).
The presence of the modem using the section B1 is checked by detecting whether or not the reception signal S41 rises at the reference timing by the transmission timing generation unit 434.
As described above, the own communication period (transmission section) is sequentially adjusted, and the transmission timing signal TGsd corresponding thereto is output from the timing generation unit 43.

FIG. 24 is a timing chart for explaining a method of setting a transmission section of a bandwidth-guaranteed modem that starts communication in the middle of section B, where (a) is a commercial power supply, (b) is a signal on the power line, (C) and (d) show the division of the reference section.
The bandwidth-guaranteed modem trying to start communication gives priority to starting communication from the beginning of the section B set by the reference timing after generating the reference timing, as shown in FIG. When a signal of another band guarantee type modem is detected by receiving a signal on the power line (arrow in FIG. 24C), it operates as a controlled modem. Then, as shown in FIG. 24 (d), the section B is divided into two equal parts, and it is confirmed whether signals of other band-guaranteed modems are detected at the first timing of the section B2 (FIG. 24 (d). ) Arrow). As a result, if no other band guaranteed modem signal is detected, its own transmission interval is set to interval B2, and communication is started.

  Note that, as shown in the flowchart of FIG. 22, the bandwidth-guaranteed modem that communicates using the section B1 also checks the presence of the modem that uses the section B2 sequentially (step ST31 of FIG. 22). The bandwidth guarantee type modem in the power line carrier communication system 1 according to the above results in appropriately assigning different transmission sections within the section B according to the order of entry into the system. That is, the band-guaranteed modem that first entered the system performs communication using the section B1, and the band-guaranteed modem that subsequently enters the system performs communication using the section B2.

(3) Best Effort Modem The best effort modem exclusively acquires the reference timing by detecting the reference timing, and starts communication using the section A in the reference section.

FIG. 25 is a flowchart showing a setting operation of a preferable communication section of the best effort type modem.
First, the reference timing is detected (step ST50). When the reference timing is detected (step ST51), the reference timing is set (step ST52).
Based on the reference timing, a reference section TGref is set, and communication is performed using a previous section (section A) having a predetermined ratio with the reference timing as a boundary in the reference section TGref (step ST53). Therefore, the communication of the bandwidth guarantee type modem using the section B is not disturbed.
If the reference timing cannot be detected in step ST51, the detection operation is repeated a predetermined number of times (step ST54). As this predetermined number of times, the number of times that high detection accuracy can be obtained is set. As a result, if it is determined that the reference timing cannot be detected, it can be determined that the communication of the bandwidth guarantee type modem is not performed in the system, so that the best effort type modem includes not only the section A but also the section B. Communication can be performed using all the reference intervals TGref (step ST55). As a result, the best effort modem can efficiently use the transmission path.

  In addition, after the best-effort modem starts communication using the entire reference interval, the bandwidth-guaranteed modem may start communication. Therefore, the best-effort modem detects the reference timing every predetermined time. (Step ST56). When it is recognized by detecting the reference timing that the band-guaranteed modem has started communication (step ST51), the transmission section is limited to section A (step ST53).

As described above, in the power line carrier communication system 1 according to the first embodiment, among the reference sections set by the reference timing, the best effort communication is performed in the previous section (section A) with the reference timing as a boundary. Since two bandwidth guaranteed communications are performed in two sections set by time division after the reference timing (section B), two bandwidth guaranteed communications and best effort are performed in in-home power line carrier communications. Type communication can coexist.
In the power line carrier communication system 1 according to the present embodiment, the reference timing for the time division setting of the communication section can be easily obtained based on the AC cycle of the commercial power source. Therefore, the present system can be installed in the home without a significant configuration change and cost increase.

In the embodiment described above, the method of coexisting mainly two band guaranteed communications has been described, but it is also possible to coexist three or more band guaranteed communications.
In such a case, the section B may be divided according to the number of band-guaranteed communications, and the divided communication sections may be assigned to the respective band-guaranteed communications. At that time, when each band-guaranteed modem sets its own transmission interval, as shown in FIG. 24, the division is made in order of 2 divisions, 4 divisions,... According to the reception level of the signal on the transmission path. Dividing and identifying a section (any section among a plurality of sections) in which other band-guaranteed modems are not communicating, and setting the section as its own transmission section.

In the above-described embodiment, a plurality of bandwidth-guaranteed communications are assigned to the section B, but may be assigned to the section A. That is, a plurality of bandwidth-guaranteed communication may be assigned to the section A, and best effort type communication may be assigned to the section B. In that case, the ratio of the section A is made larger than the section B (for example, the section B is about 1/8 to 1/10 of the reference section length).
In general, bandwidth guaranteed communication is performed at a constant transmission rate and the data transmission interval length is constant. Therefore, when bandwidth guaranteed communication is assigned to interval A, each bandwidth guaranteed modem is The communication start timing is determined in consideration of the transmission interval length. For example, a bandwidth-guaranteed modem as a control modem determines its own transmission interval in interval A so that its transmission ends at the reference timing. As a result, for example, the best effort modem can detect the reference timing based on the falling edge of the received signal at the reference timing candidate and set its own transmission section in section B.

<< Second Embodiment >>
Next, a second embodiment of the power line carrier communication system of the present invention will be described.
In the first embodiment, the power line carrier communication system that coexists with a plurality of band-guaranteed communications in the home has been described, but in this embodiment, power line carrier that coexists with a plurality of band-guaranteed communications performed in neighboring houses. A communication system will be described.

FIG. 26 is a diagram illustrating a system configuration of the power line carrier communication system according to the present embodiment, which is performed in each of two adjacent houses.
In FIG. 26, distribution boards 102 and 104 are attached to two houses 107 and 108, respectively. The distribution boards 102 and 104 are connected to a common outdoor transformer 100 via low-voltage distribution lines 101 and 103, respectively. The outside transformer 100 is supplied with power from a power plant (not shown) through the intermediate voltage distribution line 106 together with other outside transformers 105.

As shown in FIG. 26, the power line carrier communication system according to the present embodiment includes the power line carrier communication system 1a performed between the modems 50_1 to 50_6 in the house 107 and the power line carrier communication performed between the modems 51_1 to 51_6 in the house 108. It includes two in-home systems of system 1b.
The modems in the power line carrier communication systems 1a and 1b include the band guarantee type modem and the best effort type modem described in the first embodiment. In the present embodiment, band-guaranteed communication is performed between the modems 50_4 to 50_5 in the power line carrier communication system 1a, and band-guaranteed communication is performed between the modems 51_2 to 51_3 in the power line carrier communication system 1b.

Each modem has the same configuration as the modem 30 shown in FIG.
In particular, in the band-guaranteed modem, the transmission timing generation unit 434 in FIG. 11 is an embodiment of the third power detection unit and the third communication setting unit of the present invention.

  In FIG. 26, the transmission signal by the power line carrier communication performed in the houses 107 and 108 is attenuated by the low voltage distribution lines 101 and 103, the distribution boards 102 and 104, a power meter (not shown), and the like. However, in the houses 107 and 108 sharing the transformer outside the house, for example, the signal transmitted from the modem 50_4 in the house 107 is transmitted to the power line in the house 108 and collides with the signal transmitted from the modem 51_2, for example. It is conceivable that communication failure occurs in both houses.

  Therefore, in the power line carrier communication system according to the present embodiment, the band-guaranteed communication performed between a plurality of different houses sharing the outdoor transformer is similar to the power line carrier communication system 1 according to the first embodiment. Allocation is made to the section B (the section after the reference timing) in the reference section set by the reference timing based on the commercial power supply, and in this section B, a plurality of band-guaranteed communications coexist in a time division manner.

  At that time, since the same commercial power is supplied to the houses 107 and 108, the configuration of the modem in the system, the reference timing acquisition method, the transmission interval setting method, and the like have been described in the first embodiment. Things can be applied as they are.

For example, the operation of the power line carrier communication system according to the present embodiment is as follows.
First, it is assumed that bandwidth guarantee communication between the modem 50_4 and the modem 50_5 is started in the house 107 (power line carrier communication system 1a). The transmission signal by the band guarantee type communication is transmitted to the power line in the house 108 (power line carrier communication system 1b) through the path of the distribution board 102 → the low voltage distribution line 101 → the low voltage distribution line 103 → the distribution board 104. .
In the power line carrier communication systems 1a and 1b, since the reference timings coincide with each other, the signal transmitted from the power line carrier communication system 1a rises immediately after the reference timing in the power line carrier communication system 1b.
The modem 51_2 in the power line carrier communication system 1b detects the reference timing by observing that a signal transmitted from the power line carrier communication system 1a rises at a specific reference timing candidate. Then, in the reference section set by the detected reference timing, the own transmission section is set in the second half of the section B (section B2), and communication is started.
In this way, band-guaranteed communication (communication between modem 50_4 to modem 50_5, communication between modem 51_2 to modem 51_3) in different houses can coexist.

  Note that, for example, a signal from the band-guaranteed communication performed between the modem 50_4 to the modem 50_5 in the house 107 is observed on a power line in the house 108 due to attenuation by a low-voltage distribution line, a distribution board, a power meter, etc. Otherwise, signal collision between different houses does not matter, and band-guaranteed communication is performed independently in each house. That is, the reference timings are separately generated in the houses 107 and 108, and communication failure does not occur even if the band guaranteed communication is performed immediately after the reference timing (start of the section B).

As described above, in the power line carrier communication system according to the present embodiment, a plurality of bandwidth-guaranteed communications performed between a plurality of different houses sharing an outside transformer can coexist in a time division manner.
Actually, several to ten or so out-of-home transformers are usually shared. However, the coexistence method described in this embodiment uses three or more band-guaranteed communications as in the first embodiment. Can be easily applied to the coexistence of Further, similarly to the first embodiment, band guaranteed communication may be assigned to the section A.

<< Third Embodiment >>
Next, a third embodiment of the power line carrier communication system of the present invention will be described.

The power line carrier communication system according to the first and second embodiments is a communication system performed in a house, but separately, power line carrier communication using a power line as an access line to the Internet may be performed.
FIG. 27 shows in-home communication (in-home system) in which power line carrier communication is performed in the home, and access communication (access system) in which power line carrier communication is performed in order to access an external network from the home modem. This is shown schematically.
In FIG. 27, in the home system, modems 60_1 and 60_2 perform power line carrier communication via the power line 11, and in the access system, the home modem 60_1 passes through the power line 11, the power meter 120, and the low-voltage distribution line 110. Thus, power line carrier communication is performed with the modem 70 set outside the house. The modem 70 accesses the Internet via the optical cable 111.
As described above, when the modem 70 outside the home is used, it becomes possible to provide Internet access without pulling in a cable or the like in the home, and the system installation flexibility is excellent.

  In the present embodiment, as shown in FIG. 27, a power line carrier communication system will be described in which, when a home system and an access system exist in the same home, these two systems can coexist appropriately.

First, the configuration of the power line carrier communication system 2 according to the present embodiment will be described with reference to FIG. FIG. 28 is a diagram clarifying the configuration of the system schematically shown in FIG.
As shown in FIG. 28, the power line carrier communication system 2 includes an in-home system 3 (corresponding to the first system of the present invention) and an access system 4 (corresponding to the second system of the present invention).
The in-home system 3 includes modems 60_1 to 60_4 connected to the power line 11. In the access system 4, the in-home modem 60 </ b> _ <b> 1 and the out-of-home modem 70 are connected by the power line 11 and the low voltage distribution line 110. The modem 70 includes an optical cable 111 for accessing the Internet, and operates as a parent device in the access system 4.

In the power line carrier communication system 2 according to the embodiment, the communication in the in-home system 3 coexists by the time division described in the first embodiment, and the communication by the in-home system 3 and the communication by the access system 4 are performed. Coexist by frequency division multiplexing (FDM).
FIG. 29 shows a channel configuration example in frequency division multiplexing for coexistence of a home system and an access system signal.
In the example shown in FIG. 29, the frequency band of 4 to 30 MHz is divided into 13 subchannels f1 to f13, and the subchannels f1 to f6 (corresponding to the second frequency band of the present invention) are allocated to the access system. Subchannels f7 to f13 (corresponding to the first frequency band of the present invention) are allocated to the in-home system. The modem in each system includes a band-pass filter for passing and outputting only the frequency region of the corresponding subchannel on the transmission line. Thereby, the communication by the in-home system 3 and the communication by the access system 4 can coexist.

Here, since communication is not always performed in the access system, it is necessary to make it possible for the in-home system to use all subchannels when communication is not performed in the access system. From the viewpoint of.
Therefore, each modem of the in-home system 3 in the present embodiment, when the modem in the in-home system detects a signal from the access system, the subchannel assigned in advance (in the example shown in FIG. 29, If communication is performed on the subchannels f7 to f12) and no signal is detected by the access system, communication is performed so that communication is performed on all the subchannels (subchannels f1 to f12 in the example illustrated in FIG. 29). Control the bandwidth.

Hereinafter, a method for controlling the communication band in the home system will be described.
FIG. 30 is a timing chart for explaining a communication band control method, where (a) is a commercial power supply, (b) is a transmission section setting, (c) is a frame transmission, and (d) is an access signal. Show. The access signal is a signal observed on the power line 11 by communication of the access system. 30A to 30C are the same as FIGS. 21A to 21C.
In FIG. 30, in the home system, as shown in (b) and (c), among the reference section TGref set by the reference timing, the best effort type communication is performed in the section A, and the plurality of band guaranteed types are provided in the section B. Communication is assigned. Then, as shown in FIG. 30 (d), the access signal is sent to the power line 11 at a timing unrelated to the assigned transmission section as shown in (b).
In the present embodiment, in the home system, the communication band for the home system is controlled according to whether or not the access signal is detected.

  Next, a specific method for controlling the communication band in the home system will be described with reference to the flowcharts of FIGS. The flowchart in FIG. 31 is periodically executed in the home system.

At the regular timing, first, each modem in the home system stops all transmissions in its own transmission section (step ST60). This is because communication (access signal) is detected by the access system based on the signal power received by each modem in the home system, so that the access signal is correctly detected when each modem in the home system transmits data. This is because it cannot be done.
Then, communication (access signal) is detected by the access system (step ST61). This detection operation will be described later with reference to the flowchart of FIG.
If an access signal is detected as a result of step ST61 (step ST62), it is decided to use only the frequency region (subchannel) allocated in advance for the home system (step ST63), and the home system All transmission operations are resumed (step ST65).
If the access signal is not detected as a result of step ST61 (step ST62), in addition to the frequency region (subchannel) assigned in advance for the in-home system, the frequency region assigned in advance for the access system. (Subchannel), that is, decides to use the entire frequency region (step ST64), and each modem in the home system restarts transmission in its own transmission section (step ST65).

  FIG. 32 is a flowchart showing communication (access signal) detection operation by the access system, which is executed in step ST61 of FIG. This detection operation is executed for each modem assigned in a time division manner in the home system.

Therefore, each modem in the home system has a counter for detecting an access signal. This counter (count value Ca) is first initialized, that is, Ca = 0 is set (step ST70). Then, within a predetermined time (step ST71), the number of times that the signal power received in its own transmission interval exceeds (rises) a predetermined threshold is detected. That is, when it is the own transmission section (step ST72), the reception level in the transmission section is sequentially sampled to detect whether the reception level rises (step ST73). As shown in FIG. 30 (d), since the access signal is transmitted without synchronizing with the reference timing or the like, it is necessary to sequentially check the signal level within its own transmission interval. When this access signal is detected, since the transmission operation of the home system is stopped, the transmission signal from the modem in the home system is not erroneously detected as an access signal.
Further, every time the rising of the reception level is detected within a predetermined time (step ST74), the counter is counted up (step ST75).

  When the predetermined time has elapsed (step ST71), the count value obtained within the predetermined time is evaluated. That is, the count value Ca is compared with a predetermined threshold value CTHa (step ST76). If the count value Ca exceeds the threshold value CTHa, it is determined that communication by the access system is being performed (step ST78). If Ca is less than or equal to threshold value CTHa, it is determined that communication by the access system is not being performed (step ST79).

In this embodiment, each modem in the home system 3 includes a communication detection unit that includes a counter and detects an access signal, as well as a communication detector according to the detection result, as compared with the modem 30 shown in FIG. The difference is that it further comprises a band setting unit for setting the frequency domain. For example, the communication detection unit and the band setting unit are mounted in the MAC layer processing unit 31 shown in FIG.
Moreover, the transmission timing generation part 434 in FIG. 11 is one Embodiment of the 4th communication setting part of this invention.

As described above, according to the power line carrier communication system 2 according to the present embodiment, the in-home system 3 in which communication is performed in the home and the access system in which communication is performed in order to access an external network from the home modem. System 4 and allocating different frequency regions that do not overlap each other to in-home system 3 and access system 4 to coexist by frequency division multiplexing, and in-home system 3 periodically accesses Whether or not communication by the system 4 is performed is detected, and on the condition that the communication is not performed, the communication by the home system 3 is added to the frequency domain assigned to the access system 4. Communication was also performed using the allocated frequency domain.
Therefore, the home system and the access system can coexist while efficiently using the transmission path according to the communication status.

  The embodiment of the present invention has been described in detail above, but the specific configuration and system are not limited to the present embodiment, and design modifications and other systems can be made without departing from the scope of the present invention. This includes adaptations.

It is a figure which shows the system configuration | structure in a house in the conventional power line carrier communication system. It is a figure which shows the coexistence state by frequency division in the conventional power line carrier communication system. It is a figure which shows the band gap between the adjacent frequency bands in the conventional power line carrier communication system. It is a figure which shows the system configuration | structure of the conventional power line carrier communication system. It is a figure which shows the signal level from the other modem which one modem receives in the conventional power line carrier communication system. It is a figure which shows the coexistence state by a time division in the conventional power line carrier communication system. It is a figure which shows the system configuration | structure by which the access control apparatus was added with respect to the conventional power line carrier communication system. In a conventional power line carrier communication system, a communication device installed in a house is a diagram schematically illustrating an example of communication by a communication device that is built in a household electrical appliance and performs communication via a power line. It is a figure which shows the system configuration | structure of the conventional power line carrier communication system performed by two adjacent houses, respectively. It is a figure which shows the system configuration | structure of the power line carrier communication system which concerns on the embodiment mounted in the house. It is a block diagram which shows the structure of the modem which concerns on 1st Embodiment. It is a figure which shows the position of the reference timing with respect to various commercial power supply voltages. It is a figure for demonstrating the detection method of a reference | standard timing. 6 is a flowchart for detecting a reference timing. It is a flowchart which shows the setting operation | movement of a reference timing in a control modem. It is a flowchart which shows the notified / setting operation | movement of a reference timing in a controlled modem. It is a flowchart which shows the detection / setting operation | movement of a reference timing in a controlled modem. It is a flowchart which shows the setting operation | movement of a reference timing in the case of switching from a control modem to a controlled modem. It is a timing chart which shows the example of a setting of the transmission area based on reference | standard timing. It is a timing chart which shows the example of a setting of a transmission area. It is a timing chart which shows the example of a setting of a transmission area. It is a flowchart which shows the preferable operation | movement of a band guarantee type | mold modem after determining a reference | standard timing. It is a flowchart which shows the preferable operation | movement of a band guarantee type | mold modem after determining a reference | standard timing. 10 is a timing chart for explaining a method of setting a transmission section of a bandwidth-guaranteed modem that starts communication in the middle of section B. It is a flowchart which shows the setting operation | movement of the preferable communication area of a best effort type | mold modem. It is a figure which shows the system configuration | structure of the power line carrier communication system which concerns on 2nd Embodiment, and is respectively performed by two adjacent houses. It is a figure which represents typically the structure of the power line carrier communication system which concerns on 3rd Embodiment. It is a figure which shows the structure of the power line carrier communication system which concerns on 3rd Embodiment. This is a channel configuration example in frequency division multiplexing for coexistence of a home system and an access system signal. It is a timing chart for demonstrating the control method of a communication band. It is a flowchart which shows the concrete control method of the communication band in a premises system. It is a flowchart for detecting communication by an access system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Power line carrier communication system 10 ... Distribution board 11, 12 ... Electric light line 30, 30_1-30_6, 50_1-50_6, 51_1-51_6 ... Modem
31 ... MAC layer processing unit, 32 ... PHY layer transmission processing unit, 33 ... D / A converter,
34 ... Amplifier, 35 ... Filter, 36 ... Transmission / reception switching unit, 37 ... Coupler,
38 ... Filter, 39 ... Amplifier, 40 ... A / D converter,
DESCRIPTION OF SYMBOLS 41 ... PHY layer reception processing part, 42 ... Coupler, 43 ... Timing generation part 2 ... Power line carrier communication system 3 ... In-home system, 4 ... Access system 60_1 to 60_4, 70 ... Modem

Claims (15)

As a plurality of sets of first communication devices that can be connected to a power line in common, data cannot be communicated with each other in the group while being connected to the power line. A power line carrier communication system having a plurality of first communication devices,
The plurality of sets of first communication devices include:
The reference timing synchronized with the period of the commercial power supply voltage supplied to the power line, the first communication device a change in signal power due to data communication Te said power line smell has a first timing generator for determining when not detected Including
Data communication is performed using a communication section immediately after the reference timing among a plurality of communication sections that divide the interval of the reference timing synchronized with the cycle of the commercial power supply voltage .
A first set of first communication devices;
In the reference timing detection process, for a plurality of candidate timings corresponding to a plurality of phase angles of the input commercial power supply voltage, a change in signal power due to data transmission immediately after each candidate timing is detected, and the plurality of candidates Among the timings, the candidate timing at which the most change in signal power due to data transmission is detected more than a predetermined number of times is used for its own communication control as the reference timing determined by the first communication device of the first set. Including a first communication device having a second timing generation unit for setting a common reference timing;
Data communication is performed using a communication section other than the communication section immediately after the reference timing among the plurality of communication sections .
A second set of first communication devices;
Including
The first communication device of the first set and the first communication device of the second set execute data communication for each set in a time division manner using each communication section . The power line is installed in a plurality of homes from the same external transformer,
The plurality of sets of first communication devices are installed separately in the plurality of homes in units of groups, and execute data communication for each set in each home,
The first communication device that determines the reference timing when data communication based on the reference timing is not detected is installed in the plurality of homes,
When data of the first communication device installed in any home is propagated to another home via the power line, and a change in signal power due to data communication in the home is observed in the other home The reference timing of the first communication device installed in any one of the homes is shared by the plurality of sets of first communication devices installed in any one of the homes and the other homes,
When a change in signal power due to data communication of the first communication device installed in any home is not observed in another home, the reference timing by the first communication device installed in each home is shared in each home The power line carrier communication system according to claim 1. The plurality of candidate timings are:
The power line carrier communication system according to claim 1 or 2 , corresponding to a plurality of phase angles which are a plurality of zero cross points of the commercial power supply voltage . The first communication device of the first set that has determined the reference timing is:
4. The bandwidth guarantee type communication in which a transmission rate is guaranteed is executed by a communication section immediately after the reference timing by using the reference timing determined by itself for its own communication control. The power line carrier communication system described. The second set of first communication devices that have detected data communication based on the reference timing are:
Data communication using the own communication control said reference timing detected by the communication section than the communication section immediately after the reference timing, claim 4 to perform communication bandwidth guaranteed transmission rate is guaranteed serial mounting power line carrier communication system. The second set of first communication devices that have detected data communication based on the reference timing are:
The reference timing at which data communication is detected is used for own communication control, and best-effort type communication that does not require a transmission rate to be guaranteed is performed in a communication section other than the communication section immediately after the reference timing. Item 5. A power line carrier communication system according to Item 4 . The plurality of sets of first communication devices include:
As the first communication device of the first set that determines the reference timing,
Including a first band-guaranteed set of first communication devices for performing band-guaranteed communication in which a transmission rate is guaranteed using the reference timing determined by itself,
As a plurality of sets of the first communication devices of the second set for detecting data communication based on the reference timing,
A first band-guaranteed set of first communication devices that perform band-guaranteed communication with a guaranteed transmission speed using the detected reference timing;
The first communication device of best-effort set of executing communication with best effort is not necessary to ensure the heat transmission speed by using the reference timing detected,
Including
The first communication device of the best effort type set is
Of the division of the reference timing interval into three or more communication sections, the communication section selected by the first communication device of the first band guaranteed type set and the first communication of the second band guaranteed type set The power line carrier communication system according to any one of claims 1 to 3 , wherein best-effort communication is performed using a communication section other than the communication section selected by the apparatus . The plurality of sets of first communication devices perform data communication for each set in a home where each set is installed,
The power line carrier communication system is:
A second communication device that performs data communication with a communication device outside the home using a predetermined frequency band for the power line;
The first communication device is
A communication detection unit that detects communication of the second communication device by detecting that the signal power of the power line in the communication section of the self changes due to data communication of the second communication device;
When communication by the second communication device is detected, data communication is performed using a band other than the predetermined frequency band,
The power line carrier communication system according to any one of claims 1 to 7 , wherein when communication by the second communication device is not detected, data communication is performed using a band including the predetermined frequency band . When connected to the same power line together with another set of communication devices, perform time-sharing data communication with the other set of communication devices to perform data communication with those in the same set and with other sets. A communication device that does not communicate data ,
A timing generator for detecting a reference timing of data communication synchronized with a cycle of a commercial power supply voltage supplied to the power line;
A communication unit for executing the data communication;
Have
The timing generator
In the reference timing detection process, the signal power of the other set of communication devices is transmitted immediately after each candidate timing for a plurality of candidate timings corresponding to a plurality of phase angles of the commercial power supply voltage input. When a change is detected and there is a candidate timing at which a change in signal power due to data transmission is detected most frequently after a predetermined number of times among the plurality of candidate timings, the candidate timing is set as the other set of communication. As a reference timing determined by the device, set to a common reference timing used for own communication control,
If the change in signal power due to data transmission of the other set of communication devices is not detected, the reference timing is determined so as to be synchronized with the cycle of the commercial power supply voltage,
The communication unit is
When the reference timing is determined by the timing generation unit, data and data in the same set using a communication section immediately after the reference timing among a plurality of communication sections dividing the interval of the reference timing Communicate
When the reference timing by the other set of communication devices is detected by the timing generation unit, another set in which the reference timing is determined by determining a used section of the plurality of communication sections. Data communication is performed with a communication section other than the communication section immediately after the reference timing used by the communication apparatus using the communication device.
Communication device. The communication unit executes a bandwidth-guaranteed communication in which a transmission rate is guaranteed using a communication section immediately after the reference timing or a communication section other than the communication section immediately after the reference timing.
The communication device according to claim 9. When connected to the same power line together with another set of communication devices, perform time-sharing data communication with the other set of communication devices to perform data communication with those in the same set and with other sets. A communication device that does not communicate data,
A timing generator for detecting a reference timing of data communication determined by the other set of communication devices synchronized with a cycle of a commercial power supply voltage supplied to the power line;
A communication unit for executing the data communication;
Have
The timing generator
In the reference timing detection process, the signal power of the other set of communication devices is transmitted immediately after each candidate timing for a plurality of candidate timings corresponding to a plurality of phase angles of the commercial power supply voltage input. When a change is detected and there is a candidate timing at which a change in signal power due to data transmission is detected most frequently after a predetermined number of times among the plurality of candidate timings, the candidate timing is set as the other set of communication. As a reference timing determined by the device, set to a common reference timing used for own communication control,
The communication unit is
When a reference timing by the other set of communication devices is detected by the timing generation unit, the reference generation unit determines a used section among a plurality of communication sections that divide the reference timing interval. Data communication is performed with the one in the same set using a communication section other than the communication section immediately after the reference timing used by another set of communication devices that have determined the timing,
When the reference timing by the other communication device is not detected by the timing generation unit, data communication is performed with one in the same set using all of the plurality of communication sections.
Communication device. The communication unit is
When a reference timing by the other set of communication devices is detected by the timing generation unit, a transmission rate is transmitted using a part of the plurality of communication sections that divide the reference timing interval. Perform best-effort communication without the need to guarantee
If the timing generation unit does not detect the reference timing by the other set of communication devices , it performs best effort type communication that does not need to guarantee the transmission rate using all the intervals of the reference timing.
The communication apparatus according to claim 11 . The signal power of the power line in its own communication section changes due to data communication of another communication device connected to the power line and performing data communication with a communication device outside the house using a predetermined frequency band of the power line. Having a communication detection unit for detecting communication of the other communication device by detecting,
The communication unit is
It is possible to divide the frequency band in data communication,
When communication by the other communication device is detected, data communication is executed using a band other than the predetermined frequency band,
The communication apparatus according to any one of claims 9 to 12 , wherein when communication by the other communication apparatus is not detected, data communication is performed using a band including the predetermined frequency band . As a first communication device of the plurality of sets that can be commonly connected to the power line, to each other data communication between and other set communicate data within each set in a state of being connected in common to the power line A communication method in a power line carrier communication system having a plurality of sets of first communication devices that cannot be performed,
Of the plurality of sets of first communication devices, a first set of first communication devices is:
The reference timing synchronized with the period of the commercial power supply voltage supplied to the power line by the first timing generator provided in any of the first communication devices of the first set, Determined when no change in signal power due to data communication is detected on the power line,
Among a plurality of communication sections that divide the interval of the reference timing synchronized with the cycle of the commercial power supply voltage, data communication is performed using a communication section immediately after the reference timing,
Of the plurality of sets of first communication devices, a second set of first communication devices is:
Among the second communication devices of the second set, a plurality of the commercial power supply voltages input in the reference timing detection process by the second timing generator provided in any of the first communication devices. For a plurality of candidate timings corresponding to the phase angle, a change in signal power due to data transmission immediately after each candidate timing is detected, and among the plurality of candidate timings, the change in signal power due to data transmission is the highest at a predetermined number of times or more. A number of detected candidate timings are set as common reference timings used for own communication control as reference timings determined by the first communication device of the first set,
Data communication is performed using a communication section other than the communication section immediately after the reference timing among the plurality of communication sections,
The first set of first communication devices and the second set of first communication devices use each communication section to perform data communication for each set in a time-sharing manner. The plurality of sets of first communication devices perform data communication in the home where each is installed,
The power line carrier communication system is:
A second communication device that performs data communication with a communication device outside the home using a predetermined frequency band for the power line;
The first communication device is
Detecting the communication of the second communication device by detecting that the signal power of the power line in its communication section changes due to the data communication of the second communication device;
When communication by the second communication device is detected, data communication is performed using a band other than the predetermined frequency band,
The communication method according to claim 14 , wherein when communication by the second communication device is not detected, data communication is performed using a band including the predetermined frequency band .

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