Communication device, communication method, and communication system

Abstract

This communication device is provided with: a communication unit that performs power line communication with each of a first communication device and a second communication device; an estimation unit that, at a timing at which a signal is transmitted from one device of the first communication device and the second communication device, and no signal is transmitted from the other device of the first communication device and the second communication device, estimates a transmission path with one device; and a detection unit that detects partial discharge in the transmission path, on the basis of the result of the estimation.

Description

Communication device, communication method, and communication system

[0001] The present disclosure relates to a communication device, a communication method, and a communication system.

[0002] Multi-hop communication using power line communication (PLC) has been known in the past. In such multi-hop communication, in a communication network (hereinafter sometimes simply referred to as a network (NW)) consisting of multiple communication terminals, communication signals are relayed between communication terminals to communicate with terminals that cannot directly communicate with the communication terminal.

[0003] Furthermore, Patent Document 1 discloses a technique for detecting deterioration of a power line (for example, partial discharge, which will be described later) based on the transmission and reception of a PLC signal (for example, the state of the PLC).

[0004] Japanese Patent Application Laid-Open No. 2019-075770

[0005] However, in the above-mentioned technology, partial discharge detection in a power line (also called a power cable, for example) is performed in direct communication between communication terminals, and partial discharge detection that takes into account interference between communication terminals that relay signals, such as in a network consisting of multiple communication terminals (for example, multi-hop communication), has not been considered. For example, in multi-hop communication using PLC, there is room for consideration of controlling the timing of detecting partial discharge (or the timing of transmitting and receiving signals) while taking into account interference between multiple communication terminals.

[0006] Non-limiting examples of the present disclosure contribute to providing a communication device, a communication method, and a communication system that can reduce the influence of interference between communication terminals in a network consisting of multiple communication terminals that perform power line communication, and improve the accuracy of detecting partial discharge in a power cable.

[0007] A communication device according to one embodiment of the present disclosure includes a communication unit that performs power line communication with each of a first communication device and a second communication device, an estimation unit that estimates a transmission path between one of the first communication device and the second communication device at a time when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, and a detection unit that detects partial discharge in the transmission path based on the result of the estimation.

[0008] In a communication method according to one embodiment of the present disclosure, a communication device performs power line communication with each of a first communication device and a second communication device, and when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, estimates a transmission path between the one of the first communication device and the second communication device, and detects partial discharge in the transmission path based on the result of the estimation.

[0009] A communication system according to one embodiment of the present disclosure includes a first communication device, a second communication device, and a third communication device that performs power line communication with each of the first communication device and the second communication device, estimates a transmission path between one of the first communication device and the second communication device at a time when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, and detects partial discharge in the transmission path based on the result of the estimation.

[0010] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0011] According to an embodiment of the present disclosure, in a network configured with a plurality of communication terminals that perform power line communication, the influence of interference between the communication terminals can be reduced, and the accuracy of detecting partial discharge in a power cable can be improved.

[0012] Further advantages and benefits of one embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features.

[0013] FIG. 1 shows an example of a hardware configuration of a terminal according to an embodiment of the present disclosure. FIG. 2 shows an example of a functional configuration of a CPU of a terminal according to an embodiment of the present disclosure. FIG. 3 shows an example of partial discharge detection. FIG. 4 shows an example of transmission path estimation. FIG. 5 shows an example of transmission path estimation. FIG. 6 shows an example of transmission path estimation. FIG. 7 shows an example of transmission path estimation. FIG. 8 shows an example of transmission path estimation. FIG. 9 shows an example of transmission path estimation. FIG. 10 shows an example of an operation procedure of a terminal. FIG. 11 shows an example of an operation procedure of a terminal. FIG. 12 shows an example of a slot configuration. FIG. 13 shows an example of a channel configuration. FIG. 14 shows an example of an operation procedure of a terminal. FIG. 15 shows an example of partial discharge detection using spectrum analyzer mode. FIG. 16 shows an example of an operation procedure of a terminal.

[0014] In PLC, for example, communication is performed using a power cable as a transmission path. Specifically, a PLC signal is superimposed on the electric power flowing through a conductor included in the power cable and transmitted. PLC is applied to communication using, for example, an underground tunnel or a cable buried in the ground (e.g., a buried cable), or an overhead power transmission cable.

[0015] In power equipment such as a power cable, partial discharges can occur due to, for example, aging deterioration of a metal shielding layer (hereinafter also referred to as a shielding layer) included in the power cable. For example, partial discharges can occur in a power cable due to a phenomenon in which a small amount of moisture or debris that has penetrated into the shielding layer of the power cable penetrates into the insulator, causing insulation breakdown due to aging (e.g., water treeing). Partial discharges can also occur in synchronization with an AC power source. Partial discharges due to aging deterioration can also occur in power cables that are composed of bare wires or the like rather than insulated wires insulated with insulators.

[0016] Such noise due to partial discharge can increase with the aging of the power cable, and may degrade the communication quality in the PLC, resulting in a decrease in communication speed (e.g., physical layer (PHY) speed).

[0017] For example, Patent Document 1 discloses a method for detecting partial discharge. However, there is room for further study on a method for improving the accuracy of detecting partial discharge in a power cable (e.g., a transmission path in a PLC) in a network (e.g., multi-hop communication) configured with a plurality of communication terminals. Therefore, in one embodiment of the present disclosure, a method for accurately detecting partial discharge in a power cable in a network (e.g., multi-hop communication) configured with a plurality of communication terminals is described. According to one embodiment of the present disclosure, it is possible to improve the accuracy of detecting partial discharge in a power cable and improve communication quality in a PLC.

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or redundant explanation of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0019] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0020] (Embodiment) <Configuration of communication system> A communication system according to an embodiment of the present disclosure may be, for example, a PLC system.

[0021] The communication system may include, for example, a plurality of terminals 100. The plurality of terminals 100 may include, for example, a master terminal, a slave terminal, and at least one relay terminal. For example, the terminals 100 may transmit and receive signals via a ground line connected to a shielding layer in a power cable of a power supply facility.

[0022] The communication system may use, for example, underground power supply equipment (including power cables). In this case, for example, a control device (not shown) may be connected to the parent device, and each of the child devices (and relay terminals) may be connected to a sensor controlled by the control device. The sensor may be implemented as part of a function of an electronic device (not shown), such as a camera, lighting fixture, or air conditioner. Note that some of the terminals may not be connected to an electronic device, and a terminal to which no electronic device is connected may function as a repeater.

[0023] The parent device may be connectable to, for example, a server device (information processing device). The server device may be connected to the parent device via a wired or wireless connection, or may be a device (for example, a cloud server) connected to the parent device via the Internet.

[0024] It should be noted that the communication system is not limited to the use of power supply equipment buried underground, but may also use ground equipment or overhead power transmission line equipment, or may use a system located underwater (e.g., underwater).

[0025] Furthermore, these parent devices, child devices, and relay terminals may be collectively referred to as communication terminals or simply terminals, communication nodes or simply nodes, communication equipment or simply equipment, communication devices or simply devices, communication terminals or simply terminals, etc. Furthermore, the parent devices may be referred to as master terminals, parent terminals, masters, roots, root terminals, etc., and the child devices may be referred to as end terminals, child terminals, terminals, etc.

[0026] In addition, in the communication system, each terminal performs multi-hop communication using a PLC that uses a power line as a communication line and superimposes a signal on the power line.

[0027] In multi-hop communication, for example, multiple terminals are connected within a system, and a relay transmission network is constructed up to a specified number (also called the number of hops), with a parent terminal at the top. Within the system, a relay terminal is automatically selected depending on the state of the transmission path between the terminals, and communication data is relayed between the parent terminal and the child terminal. In this way, in a multi-hop communication system, multi-hops (or a topology) are formed, and multi-hop communication is performed.

[0028] The system may be interpreted as a communication system, a network, a communication network, etc.

[0029] In a multi-hop communication system, each terminal evaluates the communication quality with its neighboring terminal (or nearby terminal), and after evaluating the communication quality, the parent terminal sets an appropriate relay route. Unicast (UC) frames are then relayed along the relay route set by the parent terminal. Regarding broadcast frames, the target frame is delivered to all terminals. Therefore, after a broadcast frame transmitted from a certain terminal is received by the parent terminal and all relay terminals, these terminals forward the target frame to other terminals by broadcasting it again.

[0030] In the following description, the term "frame" may be appropriately replaced with terms such as "packet," "message," and "signal."

[0031] <Configuration of Terminal> FIG. 1 is a diagram showing an example of the hardware configuration of a terminal 100 according to this embodiment.

[0032] For example, a master device in a communication system may have the configuration of the terminal 100 shown in FIG. 1, and a slave device or a backbone terminal may have the configuration of the terminal 100 shown in FIG.

[0033] 1 , the terminal 100 includes a central processing unit (CPU) 201, a storage device 202, a communication device 203 (e.g., corresponding to a communication unit), and a device interface device 204. The terminal 100 may include other components in addition to those described above.

[0034] The CPU 201 controls the overall operation of the terminal 100. The CPU 201 realizes various functions of the terminal 100 (including the processes described below) by loading predetermined programs stored in, for example, a hard disk drive (HDD), a solid state drive (SSD), or the like included in the storage device 202 into a random access memory (RAM) or the like included in the storage device 202 and executing the programs. The programs executed by the CPU 201 may be pre-stored in the storage device 202, or may be provided via a telecommunications line such as the Internet or stored in a non-transitory storage medium such as a memory card.

[0035] The storage device 202 is a non-transitory storage medium and includes non-volatile memory such as an HDD, SSD, or ROM (Read Only Memory), electrically rewritable non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory), and volatile memory such as RAM. The storage device 202 stores information (e.g., information in a table format) regarding communication paths, topology information, and terminals with which communication is possible (e.g., other terminals with which direct communication is possible). The storage device 202 also stores programs such as control programs for operating the terminal 100, data required to execute these programs, identification information of the terminal 100, and other information / data processed (processed) by the terminal 100 (e.g., the CPU 201).

[0036] When terminal 100 is a parent device, the storage device 202 stores, for example, a communication path data table for registering all communication paths between terminals established within the network, and a topology table for recording information (link information) about adjacent terminals with which each terminal can directly communicate.

[0037] In addition, when the terminal 100 is a slave terminal or a relay terminal, the memory device 202 stores, for example, information indicating terminals with which the terminal 100 can communicate (e.g., adjacent terminals) and the communication quality between the terminal 100 and the adjacent terminals.

[0038] The communication device 203 is a communication interface device for communicating with other terminals 100. The communication device 203 may be a communication interface device for a PLC.

[0039] The device interface device 204 is an interface device for transmitting and receiving (input / output) data between a control device or an electronic device connected to the terminal 100. The device interface device 204 may be, for example, a communication interface device that complies with the Ethernet (registered trademark) standard.

[0040] FIG. 2 is a diagram showing an example of the functional configuration of the CPU 201 according to this embodiment.

[0041] The CPU 201 includes a packet analysis unit 301, an authentication processing unit 302, a transmission path estimation unit 303, a topology management unit 304, a partial discharge detection unit 305, and a packet generation unit 306. Note that the server device may include part of the functional configuration of the CPU 201 shown in FIG.

[0042] The CPU 201 may receive at least one of a hello packet (H packet) (which may also be referred to as a hello message or a hello signal), an authentication packet, a synchronization packet, a transmission path estimation packet, and a normal packet. The H packet is simultaneously broadcast from one terminal to all connected terminals prior to an authentication process performed in a communication system (communication network). In addition, H packets are periodically transmitted or broadcast by each terminal to adjacent terminals to update route information (such H packets may also be referred to as periodic signals). The H packet may refer to a packet that notifies the presence of the terminal. For example, the H packet may include identification information of a parent device in the network, information about the sender of the H packet, information about adjacent terminals of the terminal, information about the communication quality of the link, etc. The authentication packet is a packet transmitted and received during the authentication process. The synchronization packet is a packet used for time synchronization, such as a Sync packet or a Follow Up packet. The normal packet may be, for example, sensor data acquired by a sensor. Furthermore, the packet for transmission path estimation is a packet used when estimating a transmission path, and may include a signal (for example, a reference signal or a pilot signal) known to both the transmitting and receiving terminals.

[0043] The packet analysis unit 301 analyzes the data structures of various input packets (H packets, authentication packets, synchronization packets, transmission path estimation packets, and normal packets) to determine the packet type, and allocates the packet to a destination based on the determination result. For example, if the packet analysis unit 301 determines that the input packet is a transmission path estimation packet, it outputs the transmission path estimation packet to the transmission path estimation unit 303. Also, for example, if the packet analysis unit 301 determines that the input packet is an authentication packet, it outputs the authentication packet to the authentication processing unit 302. For example, if the packet analysis unit 301 determines that the input packet is a normal packet, it outputs the normal packet to the topology management unit 304.

[0044] The authentication processing unit 302 executes authentication processing with the terminal that is the sender of the authentication packet, using the authentication packet input from the packet analysis unit 301. The authentication processing unit 302 outputs to the topology management unit 304 an authentication packet that is a packet generated during the authentication processing, or a response to an authentication packet sent from another terminal.

[0045] The transmission channel estimation unit 303 performs channel estimation (CE) between the terminal that is the source of the packet and the own terminal, using the packet for transmission channel estimation input from the packet analysis unit 301. The transmission channel estimation unit 303 outputs the transmission channel estimation result to the partial discharge detection unit 305.

[0046] The topology management unit 304 manages (obtains) topology information indicating the topology generated by the parent device (i.e., the terminals constituting the communication system and their connection configuration), and distributes and outputs various packets to destinations (e.g., packet generation unit 306) based on the topology information. The topology information is stored in the topology management unit 304 of each terminal or in the storage device 202. The topology management unit 304 also stores in the topology management unit 304 or the storage device 202 not only the topology information but also information regarding the above-mentioned communication paths, terminals with which communication is possible (e.g., other terminals with which direct communication is possible), its own terminal, etc. The topology management unit 304 of the parent device generates (forms) a topology based on H packets transmitted from each of one or more terminals that are the subject of authentication processing, and provides topology information indicating the topology to other terminals.

[0047] The partial discharge detection unit 305 detects partial discharge in the transmission path based on the transmission path estimation result input from the transmission path estimation unit 303. An example of the partial discharge detection process in the partial discharge detection unit 305 will be described later. For example, the partial discharge detection unit 305 outputs information indicating the partial discharge detection result to the packet generation unit 306.

[0048] The packet generation unit 306 generates and outputs packets for data communication, H packets, etc. to other terminals as destinations, based on the authentication packets or normal packets input from the topology management unit 304, or information input from the partial discharge detection unit 305.

[0049] The functional configuration of the CPU 201 is not limited to the example shown in FIG. 2, and may include other processes (for example, synchronization control related to time synchronization in a communication system).

[0050] <Operation of Communication System> An example of operation relating to partial discharge detection in a communication system will be described below.

[0051] [Method for detecting partial discharge] FIG. 3 shows an example of a method for detecting partial discharge by the terminal 100. In FIG.

[0052] As shown in FIGS. 3A and 3B, a plurality of terminals 100 performing PLC may perform multi-hop communication synchronized with an AC power supply (for example, 50 Hz or 60 Hz).

[0053] Hereinafter, each terminal 100 in multi-hop communication may be referred to as an “MHP.” The MHP may be assigned a number corresponding to the number of hops from the parent device (hereinafter also referred to as a “hop number”).

[0054] As described above, when a partial discharge occurs in a power cable used as a transmission path for a PLC, noise due to the partial discharge synchronized with the AC power supply may occur, as shown in FIG. 3( a). The noise due to the partial discharge reduces the communication quality in the PLC, for example, the communication speed (e.g., PHY speed). For example, as shown in FIG. 3( c), as the power cable deteriorates over time, the noise due to the partial discharge increases and the PHY speed decreases (or deteriorates). Thus, there is a correlation between the partial discharge and the estimated transmission path characteristics (e.g., PHY speed).

[0055] Therefore, the terminal 100 performs transmission channel estimation using a received signal from another terminal and detects partial discharge based on the transmission channel estimation result. The transmission channel estimation value may be, for example, a signal-to-noise ratio (SNR), a carrier-to-interference-and-noise ratio (CINR), or a PHY speed. The terminal 100 may determine a change in the transmission channel estimation value (or the CINR or PHY speed) by periodic observation or statistical processing of the transmission channel estimation. For example, the terminal 100 can reduce the influence of normal noise (e.g., background noise) or instantaneous noise different from noise due to partial discharge by performing a moving average of the transmission channel estimation value over a sufficient period.

[0056] For example, the terminal 100 may determine that a partial discharge has occurred when a transmission path estimated value (e.g., PHY speed) is less than a threshold value (e.g., a desired value). When the terminal 100 detects a partial discharge, it may transmit (e.g., report or notify) information regarding the detection of the partial discharge to a higher-level terminal, a parent device, or a server device. Note that the information regarding the detection of the partial discharge may include, for example, information indicating the occurrence of a partial discharge, information regarding the terminal 100 that detected the partial discharge or the corresponding power cable (transmission path), and information urging inspection or replacement of the power cable.

[0057] In the example of Fig. 3(a), when the AC power supply is 50 Hz, one interval (e.g., slot), which is the communication resource unit in the PLC, is 5 ms. In the example of Fig. 3(a), the cycle of the AC power supply (AC cycle) is divided into four slots in the PLC.

[0058] For example, as shown in Figure 3(a), the slots obtained by dividing the AC period include slots in which broadcast frames (hereinafter also referred to as BC frames) are transmitted and received, slots in which unicast frames (hereinafter also referred to as UC frames) are transmitted and received, and slots in which transmission path estimation is performed.

[0059] In each slot where transmission channel estimation is performed, a frame (hereinafter also referred to as a CE frame) may be transmitted in either a direction from higher to lower (rightward arrow in FIG. 3A) or a direction from lower to higher (leftward arrow in FIG. 3A). The CE frame includes, for example, a signal known to both the transmitting side and the receiving side (for example, a reference signal or a pilot signal).

[0060] The slot configuration (setting) synchronized with the AC cycle may be determined, for example, by a parent device, and the slot setting information may be notified to other terminals 100 (for example, a relay terminal or a child device). In this case, for example, the parent device may notify other terminals 100 (for example, a relay terminal or a child device) of the determined slot configuration using a control signal such as an H packet. However, the method of notification from the parent device to the relay terminal or the child device is not particularly limited. Furthermore, the slot configuration (setting) may be determined by each terminal 100 based on information from other terminals (for example, a parent device or a higher-level terminal) and notified to the other terminals.

[0061] 3(a) and 3(b) show an example in which a partial discharge occurs due to deterioration of a portion of the power cable between MHP1 and MHP2 that is close to MHP1. For example, MHP2 does not detect a partial discharge from transmission path estimation using a CE frame from MHP1 at timing (1). On the other hand, MHP1 detects a partial discharge from transmission path estimation using a CE frame from MHP2 at timing (2). MHP1 may, for example, report the occurrence of a partial discharge in the power cable close to MHP1 to a parent device or a server device.

[0062] 3B, when MHP1 and MHP2 perform transmission channel estimation, a signal from another MHP (not shown) may interfere with a CE frame that one of MHP1 and MHP2 receives from the other MHP1 and MHP2. If interference occurs during transmission channel estimation, the accuracy of transmission channel estimation may decrease, and the accuracy of partial discharge detection may deteriorate.

[0063] Therefore, when estimating a transmission channel in each terminal 100, it is desirable to perform control to suppress interference due to signals from other terminals 100. Examples of interference suppression control include control of the interval between terminals 100 that perform transmission channel estimation, control of the direction in which transmission channel estimation is performed, or power control in transmission channel estimation in PLC (or multi-hop communication) synchronized with AC.

[0064] An example of a transmission channel estimation method according to this embodiment will be described below.

[0065] As an example, the following describes an operation example for eight terminals 100 (e.g., MHP1 to MHP8) among multiple terminals 100 performing multi-hop communication. Note that the number of terminals 100 performing multi-hop communication is not limited to eight, and may be seven or less, or nine or more.

[0066] [Method 1] In method 1, a transmission channel is estimated for one of a plurality of transmission channels in multi-hop communication (for example, a transmission channel between a pair of terminals 100) at a certain timing.

[0067] 4(a) and 4(b) show examples of transmission channel estimation in Method 1. As shown in FIG. 4(b), PLC uses a slot configuration in which an AC period is divided into four parts.

[0068] As shown in FIG. 4(a), at certain times (for example, timings (1) and (2) in a period of two AC cycles shown in FIG. 4(b)), transmission channel estimation is performed for the transmission channel (for example, a power cable) between MHP1 and MHP2. On the other hand, at these times, transmission channel estimation is not performed between other MHPs. Therefore, MHP1 and MHP2 can perform transmission channel estimation without being affected by interference from signals from other MHPs (for example, adjacent MHP3).

[0069] Also, as shown in FIG. 4(a), at other timings (for example, timings (3) and (4) in a period of two AC cycles shown in FIG. 4(b)), transmission channel estimation is performed for the transmission channel between MHP2 and MHP3. On the other hand, at these timings, transmission channel estimation is not performed between other MHPs. Therefore, MHP2 and MHP3 can perform transmission channel estimation without being affected by interference from signals from other MHPs (for example, adjacent MHP1 or MHP4).

[0070] For example, let us focus on MHP2 in FIG. 4( a). At timing (1), MHP2 performs transmission channel estimation between MHP1 and MHP2. In this case, of MHP1 and MHP3 connected to MHP2 in multi-hop communication, MHP1 transmits a signal (including, for example, a CE frame), and MHP3 does not transmit a signal. Similarly, at timing (4), MHP2 performs transmission channel estimation between MHP2 and MHP3. In this case, of MHP1 and MHP3 connected to MHP2 in multi-hop communication, MHP3 transmits a signal (including, for example, a CE frame), and MHP1 does not transmit a signal. The same applies to other terminals 100 that perform transmission channel estimation.

[0071] Thus, in method 1, the terminal 100 performs transmission channel estimation between the terminal 100 and one of the upper terminal (e.g., corresponding to the first communication device) and the lower terminal (e.g., corresponding to the second communication device) connected to the terminal 100, at a timing when a signal is transmitted from the one terminal and no signal is transmitted from the other terminal. Therefore, according to method 1, each terminal 100 can perform transmission channel estimation without being interfered with by the other terminals 100, thereby improving the accuracy of transmission channel estimation and the accuracy of partial discharge detection.

[0072] Furthermore, in slots different from the slots for performing transmission channel estimation, for example, broadcasting or unicasting may be performed. For example, as shown in FIG. 4(b), the multiple slots include a slot for performing transmission channel estimation and a slot for communicating data (e.g., a BC frame or an UC frame). Thus, the terminal 100 can perform both transmission channel estimation and data communication in the multiple slots. For example, information regarding the transmission channel estimation result or the partial discharge detection result may be transmitted in a slot for communicating data.

[0073] In addition, in a slot in which transmission channel estimation is performed, the terminal 100 may transmit or receive a frame for transmission channel estimation (hereinafter also referred to as a CE frame) during at least a portion of the period. For example, a CE frame may be transmitted during a portion (e.g., 4 ms or less) of the slot (5 ms) in which transmission channel estimation is performed shown in FIG. 4(a). Also, in the slot (5 ms) in which transmission channel estimation is performed shown in FIG. 4(a), one or more CE frames having a length shorter than the slot length (e.g., 1 ms) may be transmitted. The transmission timing of the CE frame within the slot may be periodic or may be set randomly. Also, at least one of the length and number of CE frames may be a fixed value or a variable value.

[0074] In this way, by setting the period in which the CE frame is transmitted shorter than the slot length in the slot in which transmission channel estimation is performed, it is possible to control the CE frame so that it does not extend beyond the slot section, thereby suppressing interference with other slots. Furthermore, the shorter the CE frame, the more locally the terminal 100 can detect partial discharge in the AC cycle.

[0075] Furthermore, in FIG. 4(b), a case has been described in which the interval in which transmission channel estimation is performed is set periodically, but this is not limiting. The interval in which transmission channel estimation is performed may be set periodically or aperiodically. For example, a part of the interval in which transmission channel estimation is performed shown in FIG. 4(b) may be thinned out. For example, the interval in which transmission channel estimation is performed may be thinned out when the time required for transmission channel estimation is not within a predetermined period (for example, slot length). The thinned out interval may be set as an interval in which broadcast or unicast is performed. Furthermore, the interval in which transmission channel estimation is performed may be set either fixedly or variably.

[0076] The setting of the CE frame in the slot or the setting of the section for performing the transmission channel estimation is not limited to Method 1, but can also be applied to other methods and modified examples described later.

[0077] Although FIG. 4( a ) illustrates an example in which transmission channel estimation is performed for the transmission channel between MHP1 and MHP2 and the transmission channel between MHP2 and MHP3, transmission channel estimation may be performed similarly for other transmission channels. For example, transmission channel estimation may be performed for multiple transmission channels in order of hop number. For example, as shown in FIGS. 5( a ) and 5 ( b ), transmission channel estimation may be performed between MHP1 and MHP2 at timings (1) and (2), transmission channel estimation may be performed between MHP2 and MHP3 at timings (3) and (4), and transmission channel estimation may be performed between MHP3 and MHP4 at timings (5) and (6). Transmission channel estimation may also be performed similarly at timings after timing (6).

[0078] By the channel estimation shown in FIG. 5( a ), each terminal 100 can suppress interference between signals from each other.

[0079] 5A has described a case where transmission channel estimation is performed in order from the top to the bottom of multi-hop communication, but the present invention is not limited to this, and transmission channel estimation may be performed in order from the bottom to the top of multi-hop communication, or transmission channel estimation for each transmission channel may be performed in an irregular order (for example, random order). Also, in FIG. 5A, a case where transmission channel estimation is performed hop by hop has been described, but the present invention is not limited to this, and transmission channel estimation may be performed every specified number of hops, and transmission channel estimation may not be performed for some transmission channels.

[0080] [Method 2] In method 2, at a certain timing, transmission channel estimation is performed for a plurality of transmission channels (for example, transmission channels between a plurality of sets of terminals 100) that are separated by a predetermined distance from each other among the transmission channels in multi-hop communication.

[0081] 6(a) and 6(b) show examples of transmission channel estimation in Method 2. As shown in FIG. 6(b), PLC uses a slot configuration in which an AC period is divided into four parts.

[0082] As shown in FIG. 6(a), at a certain timing (for example, timings (1) and (2) in a period of two AC cycles shown in FIG. 6(b)), transmission channel estimation is performed for the transmission channel between MHP1 and MHP2, the transmission channel between MHP3 and MHP4, the transmission channel between MHP5 and MHP6, and the transmission channel between MHP7 and MHP8.

[0083] Also, as shown in FIG. 6(a), at other timings (for example, timings (3) and (4) in a period of two AC cycles shown in FIG. 6(b)), transmission channel estimation is performed for the transmission channel between MHP2 and MHP3, the transmission channel between MHP4 and MHP5, and the transmission channel between MHP6 and MHP7.

[0084] In this way, in Fig. 6(a), each terminal 100 can simultaneously estimate a plurality of transmission paths at the same timing, thereby reducing the time required for transmission path estimation. For example, at the timings (1) to (4) shown in Fig. 4(a), it is possible to perform transmission path estimation for all of the transmission paths of MHP1 to MHP8.

[0085] 6(a), adjacent terminals 100 are placed at a predetermined distance apart. For example, in FIG. 6(a), it is assumed that adjacent terminals 100 can communicate directly with each other, whereas non-adjacent terminals 100 (e.g., terminals 100 two hops away) cannot communicate directly with each other. Therefore, signals from non-adjacent terminals 100 do not reach each terminal 100.

[0086] In this case, when each terminal 100 performs transmission channel estimation for the transmission channel with either one of the other terminals 100 at the upper or lower level in the multi-hop communication, it does not perform transmission channel estimation for the transmission channel with the other other terminal 100 at the upper or lower level in the multi-hop communication. As an example, as shown in FIG. 6( a), MHP2 does not perform transmission channel estimation with the lower MHP3 at timing (1) when it performs transmission channel estimation with the upper MHP1. Similarly, as shown in FIG. 6( a), MHP2 does not perform transmission channel estimation with the upper MHP1 at timing (4) when it performs transmission channel estimation with the lower MHP3. The same applies to the other MHPs.

[0087] For example, as shown in FIG. 6A, at a certain timing, transmission channel estimation is performed for a plurality of transmission channels between terminals 100 separated by a distance equivalent to one hop.

[0088] Furthermore, each terminal 100 may adjust (for example, change) the direction of transmission channel estimation in a section (for example, a slot) in which transmission channel estimation is performed.

[0089] As an example, let us focus on MHP2 and MHP3 in Figure 6(a). As shown in Figure 6(b), the direction of transmission channel estimation at timing (1) is set from higher to lower. As shown in Figure 6(a), in transmission channel estimation at timing (1) between MHP1 and MHP2, MHP2 performs transmission channel estimation based on a CE frame transmitted from MHP1 (higher-level terminal) to MHP2 (lower-level terminal) based on the setting in Figure 6(b). On the other hand, as shown in Figure 6(a), in transmission channel estimation at timing (1) between MHP3 and MHP4, MHP3 performs transmission channel estimation based on a CE frame transmitted from MHP4 (lower-level terminal) to MHP3 (higher-level terminal), unlike the setting in Figure 6(b).

[0090] 6(a), if MHP3 transmits a CE frame to MHP4 at timing (1), the CE frame transmitted from MHP3 to MHP4 may be unintentionally received by neighboring MHP2, which may cause interference and affect the transmission channel estimation at MHP2. In contrast, at timing (1) shown in FIG. 6(a), MHP4, not MHP3, transmits the CE frame, which makes it possible to prevent the CE frame transmitted from MHP4 from affecting the transmission channel estimation at MHP2.

[0091] That is, in method 2, as in method 1, terminal 100 (e.g., MHP2 or MHP3) estimates the transmission path between one of the upper terminal (e.g., corresponding to the first communication device) and the lower terminal (e.g., corresponding to the second communication device) connected to terminal 100 at a time when a signal is transmitted from one of the upper terminal and the lower terminal connected to terminal 100, and no signal is transmitted from the other terminal.

[0092] In this way, by adjusting the transmission path to be estimated and the direction of the transmission path estimation, it is possible to suppress interference caused by CE frames transmitted at the same timing.

[0093] In addition, for a transmission path where transmission path estimation is not performed, for example, broadcast or unicast may be performed. For example, as shown in Fig. 6(b), the multiple slots include a slot for performing transmission path estimation and a slot for communicating data (for example, a BC frame or an UC frame).

[0094] Thus, according to Method 2, even when transmission path estimation is performed simultaneously for multiple transmission paths, when each terminal 100 performs transmission path estimation, signals (e.g., CE frames) from other terminals 100 that are simultaneously performing transmission path estimation do not reach the terminal 100, thereby suppressing the impact on transmission path estimation.

[0095] Below, as examples of Method 2, operation examples when the distances between the terminals 100 are uniform and when the distances between the terminals 100 are non-uniform will be described.

[0096] In the following description, as an example, a signal level is assumed in which the signal reaches sufficiently at 500 m and does not reach at 1000 m. Note that the distance between the terminals 100, the distance at which the signal reaches sufficiently, and the distance at which the signal does not reach are only examples, and other values ​​may be used.

[0097] 7 shows an example of transmission channel estimation when the distance between terminals 100 is uniform. In FIG. 7, the distance between each terminal 100 is 500 m. In this case, a signal transmitted from each terminal 100 reaches adjacent terminals but does not reach other terminals. Therefore, as shown in FIG. 7, the transmission of CE frames (e.g., the transmitting terminal and transmission direction) may be controlled so that a CE frame is transmitted from either the upper terminal or the lower terminal to the terminal 100 that performs transmission channel estimation (e.g., the terminal 100 that receives a CE frame) and the CE frame is not transmitted from the other terminal.

[0098] For example, in FIG. 7 , the transmission paths estimated at each of timings (1) to (4) (or the distance between terminals 100 simultaneously performing transmission path estimation) are 500 m (one hop) apart. Also, for example, in FIG. 7 , the distance between the upper terminal 100 transmitting a CE frame and the lower terminal 100 may be set to be 1500 m (three hops) or more from the perspective of the terminal 100 performing transmission path estimation at each of timings (1) to (4). For example, at timing (1) in FIG. 7 , MHP1 and MHP4, which are 1500 m apart, transmit CE frames in the direction of MHP2 and MHP3, which are performing transmission path estimation. As a result, the CE frame from MHP1 reaches MHP2 but does not reach MHP3. Similarly, the CE frame from MHP4 reaches MHP3 but does not reach MHP2. Therefore, even if MHP1 and MHP4 transmit CE frames at the same time, MHP2 and MHP3 can perform transmission channel estimation without interference. The same applies to other timings and other MHPs.

[0099] Fig. 8 shows an example of transmission channel estimation when the distances between terminals 100 are non-uniform. In Fig. 8, the distance between each terminal 100 is 30 m or 500 m. In this case, a signal transmitted from each terminal 100 may reach not only the adjacent terminal but also the terminal two hops away (e.g., the terminal at the second hop). For example, a signal transmitted from MHP1 shown in Fig. 8 may reach MHP3 in addition to MHP2.

[0100] Therefore, in Fig. 8, the transmission paths estimated at each of the timings (1) to (6) (or the distance between terminals 100 simultaneously performing transmission path estimation) are at least 500 m apart. Also, for example, in Fig. 8, from the perspective of the terminal 100 performing transmission path estimation, the distance between the upper terminal 100 transmitting a CE frame and the lower terminal 100 may be set to be 1500 m (three or four hops) or more apart at each of the timings (1) to (4). For example, at timing (1) in Fig. 8, MHP1 and MHP5, which are 1500 m or more apart, transmit a CE frame in the direction of MHP2 and MHP4 performing transmission path estimation.

[0101] As a result, the CE frame of MHP1 reaches MHP2 but not MHP4. The CE frame of MHP1 also reaches MHP3, but MHP3 does not perform transmission channel estimation. Similarly, the CE frame of MHP5 reaches MHP4. Therefore, even if MHP1 and MHP5 transmit CE frames simultaneously, MHP2 and MHP4 can perform transmission channel estimation without interference. The same applies to other timings and other MHPs.

[0102] [Method 3] In Method 3, similar to Method 2, transmission channel estimation is performed at a certain timing for transmission channels between a plurality of sets of terminals 100. Furthermore, in Method 2, a case where transmission channel estimation is controlled based on the distance between terminals 100 has been described, but in Method 3, a case where transmission channel estimation is controlled based on an AGC (Automatic Gain Control) value adjusted by an AGC circuit (not shown) during transmission channel estimation, regardless of the distance, will be described.

[0103] Here, the AGC circuit sets an appropriate amplification level depending on the power of the received signal. For example, the larger the AGC value, the greater the amplification level. Therefore, when the AGC value is small (for example, when there is no need for large amplification), it indicates that the power of the received signal is high.

[0104] For example, when the AGC value is small, the received power of the CE frame during transmission channel estimation tends to be large. In this case, the noise component due to partial discharge becomes relatively small compared to the received power of the signal, so for example, the CINR (or SNR) becomes high, making it difficult to perceive (or visualize) fluctuations in transmission channel estimation as fluctuations in noise components. Therefore, when the AGC value during transmission channel estimation is smaller than a specified value (hereinafter referred to as X), the terminal 100 reduces the transmission power of the source terminal 100 so that the AGC value becomes X.

[0105] This makes it possible to maintain a uniform estimation accuracy of the transmission path regardless of the distance of the transmission path between the two terminals 100, thereby improving the detection accuracy of partial discharge.

[0106] Like Fig. 8, Fig. 9 shows an example of transmission path estimation when the distances between terminals 100 are non-uniform. In Fig. 8, the distance between each terminal 100 is 30 m or 500 m. In the following explanation, as an example, a signal level is assumed in which the signal reaches sufficiently at 500 m but does not reach at 1000 m.

[0107] In Figure 9, the distance between MHP2 and MHP3 is 30 m, which is shorter than, for example, the distance (500 m) between MHP1 and MHP2. In this case, signals are less likely to attenuate in the transmission path between MHP2 and MHP3 than in the transmission path between MHP1 and MHP2. For this reason, if the transmission power in the transmission path estimation between MHP2 and MHP3 and the transmission power in the transmission path estimation between MHP1 and MHP2 are set equal, the AGC in the transmission path estimation between MHP2 and MHP3 is likely to be smaller. Therefore, if power control is performed so that the AGC value is X, the transmission power in the transmission path estimation between MHP2 and MHP3 is set smaller than the transmission power in the transmission path estimation between MHP1 and MHP2.

[0108] Although the example of FIG. 9 illustrates a case where the topology does not have any branches (for example, a serial topology), the topology is not limited to this.

[0109] FIG. 10 shows an example where the topology has branches.

[0110] 10, for example, MHP2 and MHP3 are connected in parallel to MHP1, and MHP6 and MHP7 are connected in parallel to MHP5. In this case, each terminal 100 (each MHP) may control the transmission power of each terminal 100 so that the AGC value at the time of transmission path estimation becomes X.

[0111] Alternatively, multiple terminals 100 (e.g., MHP1 to MHP8 in FIG. 10 ) may determine the connection state (e.g., topology) between the terminals 100 so that the AGC value at the time of transmission channel estimation is X. For example, in FIG. 10 , MHP2 and MHP3 are located at approximately the same distance from MHP1. In this case, the AGC value at the time of transmission channel estimation can be set to X for each of MHP2 and MHP3 under approximately the same conditions. Therefore, for example, MHP2 and MHP3 may be connected in parallel to MHP1. Similarly, in FIG. 10 , MHP6 and MHP7 may be connected in parallel to MHP5. Similarly, the other MHPs in FIG. 10 may be connected to each other so that the AGC value is X.

[0112] In this way, in multi-hop communication (or multi-hop protocol), not only adjacent terminals are connected to each other, but also terminals at a distance based on the AGC value (a distance at which the AGC value is X) may be connected to each other. In other words, each of the other terminals (for example, upper terminals or lower terminals) connected to each terminal 100 is a terminal at which the AGC value between the terminal 100 and the other terminal is X.

[0113] 10, for example, transmission channel estimation is performed between MHP1 and MHP2 at timings (1) and (2), and transmission channel estimation is performed between MHP1 and MHP3 at timings (3) and (4). This allows MHP2 and MHP3 to perform transmission channel estimation without mutual signal interference.

[0114] An example of a transmission path estimation method has been described above.

[0115] Next, an example of the operation of the terminal 100 will be described.

[0116] [Processing up to Transmission Channel Estimation] FIG. 11 is a flowchart showing an example of the operation of the terminal 100 up to the processing up to transmission channel estimation.

[0117] 11, the terminal 100 performs authentication processing (S101). The terminal 100 performs authentication processing with another terminal 100, for example, by using an authentication packet transmitted from the other terminal 100.

[0118] The terminal 100 creates a topology (S102). For example, the parent device determines the topology of the communication system (e.g., the multiple terminals constituting the communication system and the connection form of the multiple terminals) and transmits information about the topology to the other terminals 100. The other terminals 100 different from the parent device identify the communication path of the terminal 100 and terminals with which it can communicate (e.g., terminals with which it can directly communicate) based on the information about the topology.

[0119] The terminal 100 estimates the transmission path between the terminal 100 and another terminal 100 connected in the topology (S103). The transmission path estimation method may be based on, for example, any of the above-mentioned methods 1 to 3 or a method described later.

[0120] The terminal 100 determines whether or not the AGC value adjusted by an AGC circuit (not shown) is smaller than a threshold value (for example, a desired value) (S104).

[0121] If the AGC value is equal to or greater than the desired value (S104: NO), the terminal 100 ends the processing shown in FIG.

[0122] On the other hand, if the AGC value is smaller than the desired value (S104: YES), the terminal 100 controls (adjusts) the transmission power on the transmitting side (S105) and returns to the process of S103. For example, the terminal 100 may transmit a signal to the transmitting terminal instructing (or requesting) it to reduce its transmission power. By reducing the transmission power on the transmitting side when the AGC value is smaller than the desired value, for example, the ratio of noise components due to partial discharge in the transmission channel estimation result (e.g., CINR) increases, making it easier to capture noise fluctuations in the fluctuations of the transmission channel estimation, and improving the accuracy of the transmission channel estimation.

[0123] The transmission power control on the transmitting side (the processes of S104 and S105) may be performed periodically or irregularly.

[0124] FIG. 12 is a flowchart showing another example of the operation of the terminal 100 in the process up to the transmission channel estimation.

[0125] 12, the terminal 100 performs authentication processing (S201). The terminal 100 performs authentication processing with another terminal 100, for example, by using an authentication packet transmitted from the other terminal 100.

[0126] The terminal 100 creates a topology (S202). For example, the parent device determines the topology of the communication system (e.g., the multiple terminals constituting the communication system and the connection form of the multiple terminals) and transmits information about the topology to the other terminals 100. The other terminals 100, which are different from the parent device, identify the communication path of the terminal 100 and terminals with which it can communicate (e.g., terminals with which it can communicate directly) based on the information about the topology.

[0127] For example, the terminal 100 determines whether each terminal 100 performing multi-hop communication is hopping according to the topology (S203). For example, when the transmission power of a certain source terminal (e.g., terminal A) is high, the source terminal 100 may be connected to a terminal (e.g., terminal C) that is different from a terminal close to the source (e.g., terminal B). In other words, there may be a case where terminal A hops beyond terminal B to terminal C (e.g., a connection different from the topology connection form). In the process of S203, each terminal 100 determines whether the hopping is performed in the order of terminal A, terminal B, and terminal C according to the topology.

[0128] Furthermore, the terminal 100 determines whether or not the AGC value adjusted by an AGC circuit (not shown) is smaller than a threshold value (for example, a desired value) (S204).

[0129] If hopping occurs in each terminal 100 (S203: YES) and the AGC value is equal to or greater than the desired value (S204: NO), the terminal 100 performs transmission channel estimation (S206).

[0130] On the other hand, if hopping has not occurred in each terminal 100 (S203: NO), or if the AGC value is smaller than the desired value (S204: YES), the terminal 100 controls (adjusts) the transmission power on the transmitting side (S205). For example, the terminal 100 may transmit a signal to the transmitting terminal instructing (or requesting) it to reduce its transmission power. After controlling the transmission power, the terminal 100 returns to the process of S202 and creates a topology.

[0131] When hopping is not performed at each terminal 100, reducing the transmission power of the source terminal 100 narrows the range in which the signal transmitted from the source terminal 100 arrives, making it difficult to connect with terminals that are far from the source terminal 100. This makes it easier for each terminal 100 to hop according to the topology.

[0132] Furthermore, by reducing the transmission power on the transmitting side when the AGC value is smaller than the desired value, the ratio of noise components due to partial discharge in the transmission path estimation result (e.g., CINR) increases, making it easier to capture noise fluctuations in the fluctuations of the transmission path estimation, and improving the accuracy of the transmission path estimation.

[0133] Fig. 13 is a flow diagram showing another example of the operation of the processing up to transmission channel estimation in the terminal 100. In Fig. 13, the same processes as those in Fig. 12 are denoted by the same reference numerals, and the description thereof will be omitted.

[0134] In FIG. 13, after creating the topology, the terminal 100 determines whether the PHY speed between the terminals 100 is lower than a threshold value (for example, a desired value) (S303).

[0135] If the PHY speed between the terminals 100 is lower than the desired value (S303: YES) and the AGC value is equal to or greater than the desired value (S204: NO), the terminal 100 performs transmission channel estimation (S206).

[0136] On the other hand, if the PHY speed between the terminals 100 is equal to or greater than the desired value (S303: NO), or if the AGC value is smaller than the desired value (S204: YES), the terminal 100 changes the terminal to which it is connected (S306). After changing the terminal to which it is connected, the terminal 100 returns to the process of S202 and creates a topology.

[0137] Here, the closer the distance between the terminals 100, the faster the PHY rate is likely to be. In other words, if the PHY rate is equal to or greater than a threshold, it is highly likely that the distance between the terminals 100 is short. The closer the distance between the terminals 100, the greater the received power of the signal at the time of transmission path estimation, and the more likely it is that noise due to partial discharge will be small relative to the power of the received signal, making it more difficult to capture fluctuations in the noise component due to partial discharge.

[0138] Furthermore, if the AGC value is smaller than the desired value, the received power of the signal during transmission path estimation becomes large, and the noise components due to partial discharge tend to be small relative to the power of the received signal, making it difficult to capture fluctuations in the noise components due to partial discharge.

[0139] Therefore, if the PHY speed between the terminals 100 is equal to or higher than the desired value, or if the AGC value is lower than the desired value, the destination terminal can be changed to configure a topology that increases the distance between the terminals 100. This makes it easier to capture noise fluctuations in fluctuations in transmission channel estimation, and improves the accuracy of transmission channel estimation.

[0140] An example of the process up to transmission channel estimation has been described above.

[0141] At least two of the processing examples of FIGS. 11, 12, and 13 may be applied in combination.

[0142] [Partial Discharge Detection Processing] Next, an example of partial discharge detection processing (also called partial discharge symptom search, for example) in the terminal 100 will be described.

[0143] FIG. 14 is a flowchart showing an example of the operation of the partial discharge detection process of the terminal 100.

[0144] In FIG. 14, the terminal 100 starts transmission channel estimation (S401).

[0145] The terminal 100 acquires the CINR for each section in, for example, the transmission channel estimation (S402). For example, the terminal 100 may acquire (e.g., measure) the CINR for each of a plurality of subcarriers in the communication band. Note that the parameter acquired by the terminal 100 is not limited to the CINR, and may be the SNR, the PHY rate, or another parameter.

[0146] The terminal 100 performs statistical processing using the CINR (or PHY speed, etc.) of each section (S403). In the statistical processing, multiple statistical processing operations may be performed, such as the change in CINR for each frequency resource (e.g., subcarrier) and the change in CINR for all subcarriers. Through the statistical processing, the terminal 100 can identify the frequency of occurrence of noise due to continuous partial discharge, the time period in which it occurs, the frequency band in which it occurs, or the degree of increase in noise.

[0147] The terminal 100 determines whether there is a sign of partial discharge based on the result of the statistical processing (S404). For example, the terminal 100 may determine that there is a sign of partial discharge when the CINR or the PHY rate is less than a threshold value.

[0148] When the terminal 100 determines that there is a sign of partial discharge (S404: YES), it notifies the server that there is a sign of partial discharge (S405).

[0149] Furthermore, even if the terminal 100 determines that there are no signs of partial discharge (S404: NO), the terminal 100 may report information about partial discharge to the server (for example, a regular report) (S406) and return to the processing of S402. Note that the terminal 100 does not have to perform the processing of S406.

[0150] 14 may be performed by each terminal 100 in the multi-hop communication, by some of the terminals 100 (e.g., the parent device), or by a server device. These terminals 100 or server devices may correspond to, for example, the third communication device.

[0151] An example of the operation of the terminal 100 has been described above.

[0152] As described above, in this embodiment, the terminal 100 performs power line communication with a first terminal (e.g., a higher-level terminal) and a second terminal (e.g., a lower-level terminal) connected in multi-hop communication, and estimates the transmission path between the terminal and one of the first and second terminals at a timing when a signal is transmitted from the first or second terminal and no signal is transmitted from the other of the first and second terminals. Then, the terminal 100 detects partial discharge in the transmission path based on the transmission path estimation result.

[0153] As a result, in a network (e.g., multi-hop communication) made up of a plurality of terminals 100, the terminal 100 can estimate each transmission path while reducing the influence of interference due to signals transmitted from other terminals, thereby improving the accuracy of detecting partial discharge in the power cable. Therefore, according to this embodiment, in a network made up of a plurality of communication terminals performing power line communication, the influence of interference between the communication terminals can be reduced and partial discharge in the power cable can be properly detected, thereby improving the accuracy of detecting partial discharge in the power cable and improving the communication quality in power line communication.

[0154] (Modification 1) The configuration of slots synchronized with the AC in the PLC is not limited to the example described above, and other configurations may be used.

[0155] For example, in a slot configuration synchronized with AC, the number of divisions into which an AC cycle is divided into multiple sections (e.g., slots) is not limited to 4, and other division numbers may also be used. For example, Figures 15(a) and 15(b) show examples of slot configurations in which an AC cycle is divided into 8.

[0156] The greater the number of divisions of the AC cycle, the shorter the slot length. The shorter the slot length, the finer the unit (or granularity) at which the terminal 100 can detect the position (e.g., phase) at which noise due to partial discharge occurs.

[0157] Also, for example, as an AC-synchronized slot configuration, the timing of synchronization with the AC cycle may be different. For example, time 15(b) shows an example of a slot configuration in which an offset equivalent to half the slot period is added to the synchronization timing of the slot configuration shown in Fig. 15(a).

[0158] By varying the timing of synchronization with the AC cycle, for example, the terminal 100 can shift and allocate slots to positions where noise due to partial discharge occurs, which makes it easier for the terminal 100 to detect noise due to partial discharge.

[0159] The terminal 100 may perform transmission path estimation and partial discharge detection based on a slot configuration that specifies, for example, at least one of the number of divisions of the AC cycle (e.g., 4 divisions or 8 divisions) and the synchronization timing between the AC cycle and the slot (e.g., offset).

[0160] Alternatively, the terminal 100 may perform transmission path estimation and partial discharge detection based on one of a plurality of patterns (e.g., by switching between a plurality of patterns) that differ in at least one of the above-mentioned number of divisions of the AC cycle and the synchronization timing (e.g., offset) between the AC cycle and the slots.

[0161] The number of divisions of the AC period and the offset shown in FIG. 15 are merely examples, and other values ​​may be used.

[0162] (Modification 2) In this modification, setting of a frequency band for detecting partial discharge (or estimating a transmission path) will be described.

[0163] For example, noise caused by deterioration of a power cable (e.g., noise due to partial discharge) may have frequency selectivity. In this case, the terminal 100 can more significantly detect the effect of the noise on the state of the transmission path (e.g., CINR or PHY rate) by performing communication or transmission path estimation in the frequency band where the noise exists.

[0164] Therefore, in this modification, a method of detecting partial discharge based on PHY speed (for example, statistical value) obtained by transmission path estimation using a plurality of frequency bands (for example, channels or modes) will be described.

[0165] Figure 16(a) shows an example of a frequency domain channel configuration defined in IEEE 1901a. As shown in Figure 16(a), 15 channels from x-1 to x-15 may be set. The channels shown in Figure 16(a) include channels with bandwidths 1 / 2, 1 / 4, 2 times, and 4 times that of x-1.

[0166] In the example of Fig. 16(a), the standard mode using channel x-1, the 1 / 2 mode using channel x-2 or x-3, and the 1 / 4 mode using any of channels x-4 to x-7 are set. Fig. 16(b) shows examples of signals in the standard mode, the 1 / 2 mode, and the 1 / 4 mode.

[0167] In the second modification, the terminal 100 performs transmission channel estimation by, for example, switching between multiple frequency bands that differ in at least one of bandwidth and frequency position in the frequency domain. For example, the terminal 100 may perform transmission channel estimation by changing (or switching) at least one of the channels or modes shown in FIG. 16( a). The channel or mode may be changed periodically (or periodically) or irregularly (or non-periodically), for example.

[0168] FIG. 17 is a flowchart showing an example of an operation of the partial discharge detection process of the terminal 100 according to this modification.

[0169] The terminal 100 may perform at least one of the following partial discharge detection processes (S401-1 to S406-1) in channel x-1 as shown in Figure 17(a), partial discharge detection processes (S401-2 to S406-2) in channel x-2 as shown in Figure 17(b), and partial discharge detection processes (S401-3 to S406-3) in channel x-4 as shown in Figure 17(c).

[0170] The processes of S401 to S406 shown in FIGS. 17(a) to 17(c) are the same as those shown in FIG. 14, and therefore description of the processes will be omitted here.

[0171] In this way, by switching the frequency band (e.g., channel) for transmission path estimation and partial discharge detection, the terminal 100 can improve the accuracy of transmission path estimation and partial discharge detection according to the frequency selectivity of noise caused by partial discharge.

[0172] The channel configuration in the frequency domain (for example, bandwidth and frequency position) is not limited to the example shown in FIG. 16( a ) and may be other configurations.

[0173] (Modification 3) In this modification, a case where partial discharge is detected by transmission path estimation and other methods will be described.

[0174] PLC has a spectrum analyzer mode because it uses OFDM (Orthogonal Frequency Division Multiplexing) signals.

[0175] Therefore, in this modification, the terminal 100 detects partial discharge by acquiring characteristics in the frequency domain using the spectrum analyzer mode.

[0176] For example, the terminal 100 may set the spectrum analyzer mode to ON at the timing (for example, slot) when the above-described channel estimation is performed, and acquire characteristics in the frequency domain.

[0177] For example, as shown in Fig. 18(a), the terminal 100 sets the spectrum analyzer mode to ON and acquires frequency domain characteristics at at least one of timings (1), (2), and (3). Note that one interval (e.g., one slot) shown in Fig. 18(a) is 5 ms for AC 50 Hz.

[0178] The terminal 100 also performs statistical processing on the acquired frequency domain characteristics to determine whether or not there is noise due to partial discharge within the communication band (see, for example, FIG. 18(b)). Note that, for example, the statistical processing may be performed in each terminal (for example, an edge terminal) performing multi-hop communication, or information on the frequency domain characteristics may be transmitted to a server device, and the statistical processing may be performed in the server device.

[0179] For example, the terminal 100 may determine the presence or absence of noise due to partial discharge based on the difference in characteristics between different periods of the same slot. Alternatively, the terminal 100 may determine the presence or absence of noise due to partial discharge based on the difference in characteristics between different slots. Furthermore, the determination of the presence or absence of noise due to partial discharge may be based on the difference in characteristics at AC zero crossings, or based on the difference in characteristics at positions (or phases) different from the AC zero crossings.

[0180] In the spectrum analyzer mode, the terminal 100 only needs to perform the same operation as the receiving operation, and does not need to perform signal transmission (packet transmission) such as transmission path estimation. Therefore, interference between adjacent terminals 100 does not occur in the spectrum analyzer mode. Therefore, for example, it becomes possible for each terminal 100 to simultaneously perform processing synchronized with the AC zero crossings of multiple terminals (e.g., all terminals). Note that the synchronization processing may be, for example, processing synchronized with the AC zero crossings of the parent device, or processing compliant with IEEE 1588.

[0181] In the spectrum analyzer mode, for example, when searching over one interval (e.g., 5 ms) to acquire frequency domain characteristics, if the duration of partial discharge due to deterioration of the power cable is shorter than the length of one interval, noise due to partial discharge may not appear in the acquired information. Therefore, the terminal 100 may search over intervals shorter than one interval, such as 1.25 ms and 2.5 ms. This makes it easier for the terminal 100 to detect noise due to partial discharge that occurs locally over a shorter period.

[0182] For example, the terminal 100 may acquire data on frequency domain characteristics by changing (or switching) the search time (e.g., 5 ms, 2.5 ms, and 1.25 ms). The search time may be changed periodically or aperiodically. As an example, a 2.5 ms search may be performed twice consecutively within a 5 ms slot, or may be performed multiple times using multiple slots. Note that the search time is not limited to 5 ms, 2.5 ms, and 1.25 ms, and other search time periods may be used.

[0183] FIG. 19 is a flowchart showing an example of operation of partial discharge detection processing in the terminal 100 according to this modification.

[0184] The terminal 100 may perform at least one of the following processing modes: a 5 ms spectrum analyzer mode (also referred to as SPM) as shown in FIG. 19(a), a 2.5 ms spectrum analyzer mode as shown in FIG. 19(b), and a 1.25 ms spectrum analyzer mode as shown in FIG. 19(c).

[0185] In FIG. 19, the terminal 100 starts the spectrum analyzer mode (S501).

[0186] The terminal 100 acquires information (frequency domain characteristics) of each section in, for example, a spectrum analyzer mode (S502).

[0187] The terminal 100 performs statistical processing using information about each section (S503). The statistical processing may include, for example, statistical processing such as changes in signal level at each measurement point in spectrum analyzer mode, changes in characteristics of all measurement points, changes in characteristics (e.g., signal level) for each frequency resource (e.g., subcarrier), and changes in characteristics of all subcarriers. One or more of these statistical processing may be performed, or all of them may be performed.

[0188] The terminal 100 determines whether or not there is a sign of partial discharge based on the result of the statistical processing (S504).

[0189] When the terminal 100 determines that there is a symptom of partial discharge (S504: YES), it notifies the server device that there is a symptom of partial discharge (S505).

[0190] Furthermore, even if the terminal 100 determines that there are no signs of partial discharge (S504: NO), the terminal 100 may report information about partial discharge to the server device (for example, a regular report) (S506). Note that the terminal 100 does not have to perform the process of S506.

[0191] 19 may be performed by each terminal 100 in the multi-hop communication, by some of the terminals 100 (e.g., the parent device), or by a server device. These terminals 100 or server devices may correspond to, for example, the third communication device.

[0192] In the above-mentioned variant example 3, the channel used for normal communication (e.g., any one of x-1 to x-15) and the channel for acquiring frequency domain characteristics using the spectrum analyzer mode (e.g., any one of x-1 to x-15) may be the same or different.

[0193] The embodiments of the present disclosure have been described above.

[0194] In the above-described embodiment, the case where the PHY rate is acquired in the transmission channel estimation has been described, but the method of acquiring the PHY rate is not limited to this. For example, the PHY rate may be acquired using a hello packet (H packet) (which may also be called a hello message or a hello signal), which is a signal used for topology control in multi-hop technology.

[0195] Furthermore, in the above-described embodiment, the functional units of the CPU 201 may be integrated with other functional units as appropriate, or may be divided into two or more sub-functional units.

[0196] In the above-described embodiment, the order of steps shown in the flowcharts and the like is not limited to that shown in the drawings.

[0197] Furthermore, the parameters such as the interval length (for example, slot length), the frequency of the AC power supply, and the distance between the terminals 100 in the above-described embodiment are merely examples, and other values ​​may be used.

[0198] Furthermore, the interval, which is the communication unit of the PLC in the above-described embodiment, may be a time resource unit different from the slot.

[0199] Furthermore, the communication system of the above-described embodiment is not limited to a multi-hop communication system, but may be another communication system including a plurality of terminals 100.

[0200] Summary of the embodiment A communication device according to an embodiment of the present disclosure includes a communication unit that performs power line communication with each of a first communication device and a second communication device, an estimation unit that estimates a transmission path between one of the first communication device and the second communication device at a timing when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, and a detection unit that detects partial discharge in the transmission path based on a result of the estimation.

[0201] In this communication device, multiple communication devices including the communication device, the first communication device, and the second communication device perform multi-hop communication, and at a certain timing, the estimation is performed for one of multiple transmission paths in the multi-hop communication.

[0202] In this communication device, multiple communication devices including the communication device, the first communication device, and the second communication device perform multi-hop communication, and at a certain timing, the estimation is performed for multiple transmission paths in the multi-hop communication that are separated by a predetermined distance.

[0203] In this communication device, the signal from the one device is controlled to a transmission power at which an AGC (Automatic Gain Control) value becomes a specified value.

[0204] In this communication device, each of the first communication device and the second communication device is a communication device in which an AGC (Automatic Gain Control) value between the communication device and the second communication device is a specified value.

[0205] In this communication device, in the power line communication, the cycle of the AC power supply is divided into a plurality of intervals, and the plurality of intervals include a first interval in which the estimation is performed and a second interval in which data is communicated.

[0206] In this communication device, there are multiple patterns in which at least one of the number of divisions into which the AC power cycle is divided into the multiple sections and the synchronization timing between the AC power cycle and the multiple sections is different, and the estimation unit performs the estimation based on one of the multiple patterns.

[0207] In this communication device, the estimation unit performs the estimation by switching between a plurality of frequency bands that differ in at least one of bandwidth and frequency position.

[0208] In a communication method according to one embodiment of the present disclosure, a communication device performs power line communication with each of a first communication device and a second communication device, and when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, estimates a transmission path between the one of the first communication device and the second communication device, and detects partial discharge in the transmission path based on the result of the estimation.

[0209] A communication system according to one embodiment of the present disclosure includes a first communication device, a second communication device, and a third communication device that performs power line communication with each of the first communication device and the second communication device, estimates a transmission path between one of the first communication device and the second communication device at a time when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, and detects partial discharge in the transmission path based on the result of the estimation.

[0210] In the above-described embodiments, the notation "... part" used for each component may be replaced with other notations such as "... circuit," "... assembly," "... device," "... unit," or "... module."

[0211] Although the embodiments have been described above with reference to the drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims. It is understood that such modifications or alterations also fall within the technical scope of the present disclosure. Furthermore, the components in the embodiments may be combined in any manner without departing from the spirit of the present disclosure.

[0212] The present disclosure can be realized by software, hardware, or software in conjunction with hardware. Each functional block used in the description of the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit, and each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of a single chip that includes some or all of the functional blocks. The LSI may have data input and output. Depending on the degree of integration, the LSI may also be called an IC, system LSI, super LSI, or ultra LSI.

[0213] The integrated circuit method is not limited to LSI, and may be realized by a dedicated circuit, a general-purpose processor, or a dedicated processor. Also, a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells within the LSI, may be used. The present disclosure may be realized as digital processing or analog processing.

[0214] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility.

[0215] The present disclosure may be implemented in any type of apparatus, device, or system (collectively referred to as a communications apparatus) that has a communications function. The communications apparatus may include a radio transceiver and processing / control circuitry. The radio transceiver may include a receiver and a transmitter, or both functions. The radio transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, communication-enabled vehicles or mobile transportation (e.g., cars, airplanes, ships), and combinations of the above devices.

[0216] The communication devices are not limited to portable or mobile devices, but also include any kind of non-portable or fixed equipment, devices, and systems, such as smart home devices (such as home appliances, lighting equipment, smart meters or measuring devices, control panels, etc.), vending machines, and any other "things" that may exist on an IoT (Internet of Things) network.

[0217] Communications include data communications via cellular systems, wireless LAN systems, communication satellite systems, and the like, as well as data communications via combinations of these.

[0218] A communications apparatus also includes devices such as controllers and sensors connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0219] The communication apparatus also includes infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the various apparatuses listed above, but are not limited to these.

[0220] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2023-119095, filed on July 21, 2023, are incorporated herein by reference in their entirety.

[0221] An embodiment of the present disclosure is useful in a communication system including multiple terminals.

[0222] REFERENCE SIGNS LIST 100 Terminal 201 CPU 202 Storage device 203 Communication device 204 Device interface device 301 Packet analysis unit 302 Authentication processing unit 303 Transmission path estimation unit 304 Topology management unit 305 Partial discharge detection unit 306 Packet generation unit

Claims

1. A communication device comprising: a communication unit that performs power line communication with each of a first communication device and a second communication device; an estimation unit that estimates a transmission path between one of the first communication device and the second communication device at a time when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device; and a detection unit that detects partial discharge in the transmission path based on the result of the estimation.

2. The communication device according to claim 1, wherein a plurality of communication devices including the communication device, the first communication device, and the second communication device perform multi-hop communication, and at a certain timing, the estimation is performed for one of a plurality of transmission paths in the multi-hop communication.

3. The communication device according to claim 1, wherein a plurality of communication devices including the communication device, the first communication device, and the second communication device perform multi-hop communication, and at a certain timing, the estimation is performed for a plurality of transmission paths in the multi-hop communication that are separated by a predetermined distance.

4. The communication device according to claim 1, wherein the signal from the one device is controlled to a transmission power such that an AGC (Automatic Gain Control) value is a specified value.

5. The communication device according to claim 1, wherein each of the first communication device and the second communication device is a communication device in which an AGC (Automatic Gain Control) value between the communication device and the second communication device is a specified value.

6. The communication device according to claim 1, wherein in the power line communication, a cycle of an AC power supply is divided into a plurality of intervals, and the plurality of intervals include a first interval in which the estimation is performed and a second interval in which data is communicated.

7. The communication device according to claim 6, further comprising a plurality of patterns differing in at least one of the number of divisions into which the AC power cycle is divided into the plurality of sections and the synchronization timing between the AC power cycle and the plurality of sections, and the estimation unit performs the estimation based on one of the plurality of patterns.

8. The communication device according to claim 1, wherein the estimation unit performs the estimation by switching between a plurality of frequency bands that differ in at least one of bandwidth and frequency position.

9. A communication method, comprising: a communication device performing power line communication with each of a first communication device and a second communication device; estimating a transmission path between one of the first communication device and the second communication device at a time when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device; and detecting partial discharge in the transmission path based on the result of the estimation.

10. A communication system comprising: a first communication device; a second communication device; and a third communication device that performs power line communication with each of the first communication device and the second communication device, estimates a transmission path between one of the first communication device and the second communication device at a timing when a signal is transmitted from one of the first communication device and the second communication device and a signal is not transmitted from the other of the first communication device and the second communication device, and detects partial discharge in the transmission path based on a result of the estimation.

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