Relay communication device, communication method, and communication system

Abstract

A relay communication device according to one embodiment of the present disclosure comprises: a reception unit that receives a first signal broadcasted and transmitted from a first communication device; a transmission unit that broadcasts and transmits the first signal; and a synchronization control unit that synchronizes the timing at which a second communication device that receives a first signal broadcasted and transmitted from the first communication device broadcasts and transmits the first signal with the timing at which the transmission unit broadcasts and transmits the first signal.

Description

Technical Field

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

[0002] In the past, multi-hop communication using power line communication (PLC) is known (for example, refer to Patent Document 1). For such multi-hop communication, in a communication network (hereinafter, sometimes simply referred to as "network (NW)") composed of multiple communication terminals, communication signals are relayed between communication terminals to communicate with terminals that cannot communicate directly with their own terminals. Patent Document 1 discloses a technology in which, in order to avoid signal conflicts caused by simultaneous broadcast transmissions, a terminal unicasts to a master station, and the master station broadcasts.

[0003] Prior art literature

[0004] Non-patent literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-036316 Summary of the invention

[0006] However, in the above technology, since the terminal unicasts to the main station, the signal is concentrated in the main station, which may cause delay. In addition, the signal may not reach the terminal far away from the main station. It should be noted that these situations may occur in both wired communication and wireless communication.

[0007] The non-limiting embodiments of the present disclosure contribute to providing a relay communication device, a communication method, and a communication system capable of appropriately performing broadcast transmission in a communication network.

[0008] A relay communication device according to an embodiment of the present disclosure includes: a receiving unit for receiving a first signal broadcasted from a first communication device; a sending unit for broadcasting the first signal; and a synchronization control unit for synchronizing a timing of broadcasting the first signal by a second communication device that receives the first signal broadcasted from the first communication device with a timing of broadcasting the first signal by the sending unit.

[0009] In a communication method of an embodiment of the present disclosure, a relay communication device receives a first signal broadcasted from a first communication device, and broadcasts the first signal synchronously with a timing at which a second communication device that receives the first signal broadcasted from the first communication device broadcasts the first signal.

[0010] A communication system of an embodiment of the present disclosure includes: a first communication device; a second communication device and a third communication device, which receive a signal broadcasted from the first communication device and broadcast the signal synchronously; and a fourth communication device, which receives the signal broadcasted synchronously by the second communication device and the third communication device.

[0011] It should be noted that these general or specific aspects may be implemented by a system, an apparatus, a method, an integrated circuit, a computer program or a recording medium, or may be implemented by any combination of systems, apparatuses, methods, integrated circuits, computer programs and recording media.

[0012] According to one embodiment of the present disclosure, broadcast transmission can be appropriately performed in a communication network.

[0013] More advantages and effects of an embodiment of the present disclosure will be explained through the description and drawings. These advantages and / or effects are provided by several embodiments, and the features described in the description and drawings, but not necessarily all of them need to be provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A It is a diagram showing the communication quality between a multi-hop communication system and terminals.

[0015] Figure 1B It is a diagram showing the communication quality between terminals.

[0016] Figure 2 It is a diagram showing a configuration example of a communication system according to an embodiment of the present disclosure.

[0017] Figure 3 It is a diagram showing a hardware configuration example of a terminal according to an embodiment of the present disclosure.

[0018] Figure 4 This is a diagram showing a functional configuration example of a CPU (Central Processing Unit) of a terminal according to an embodiment of the present disclosure.

[0019] Figure 5 It is a diagram showing an example of time stamp acquisition according to an embodiment of the present disclosure.

[0020] Figure 6 This is a flowchart showing an example of acquiring a time stamp when receiving a frame according to an embodiment of the present disclosure.

[0021] Figure 7 This is a diagram showing an example of time synchronization based on communication quality between terminals according to an embodiment of the present disclosure.

[0022] Figure 8 It is an embodiment of the present disclosure. Figure 7 A diagram of a virtual TC (Transparent Clock) master port and a virtual TC slave port for a path in the example shown.

[0023] Fig. 9 This is a diagram showing an example of a communication frame format according to an embodiment of the present disclosure.

[0024] Fig.10 This is a flowchart showing a general operation example of broadcast frame synchronous transmission according to an embodiment of the present disclosure.

[0025] Fig.11 It is a diagram showing an example of the operation process of broadcast synchronous transmission according to an embodiment of the present disclosure.

[0026] Fig.12 It is a diagram showing an example of the operation process of broadcast synchronous transmission according to an embodiment of the present disclosure.

[0027] Fig.13 This is a diagram showing an example of broadcast frame transmission during a broadcast-only period according to an embodiment of the present disclosure.

[0028] Fig.14A It is a diagram showing a topological configuration example of a terminal and an ID (Identifier) ​​allocation example according to an embodiment of the present disclosure.

[0029] Fig. 14B This is a diagram showing an example of broadcast frame transmission during a broadcast-only period according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] (The process of completing this disclosure)

[0031] In a multi-hop communication system, for example, a maximum of 1024 terminals are connected in the system, and a relay transmission network with a maximum of 10 hops is constructed with the main terminal as the top. In the system, a relay terminal is automatically selected according to the state of the transmission path between the terminals, and the communication data is relayed between the main terminal and the terminal terminal. In this way, in a multi-hop communication system, multiple hops are formed and multi-hop communication is performed. As a high-speed PLC capable of constructing such a multi-hop communication system, HD-PLC (High Definition PowerLine Communication) is known. It should be noted that the system may be a communication system, a network, a communication network, etc.

[0032] In a multi-hop communication system, each terminal evaluates the communication quality with its neighboring terminals, and after evaluating the communication quality, the master terminal sets an appropriate relay path. In addition, unicast frames are relayed along the relay path set by the master terminal.

[0033] Reference Figure 1A and Figure 1B, an example of setting up a relay path in a multi-hop communication system is described.

[0034] Figure 1A 1 is a diagram showing a multi-hop communication system including a main terminal M10 and terminals A to F 20A to 20F (terminals A to E 20A to 20E: relay terminals, terminal F to 20F: end terminals). Figure 1A The link cost (LC) indicating the communication quality between the terminals is also shown.

[0035] Figure 1B Yes means including Figure 1A FIG. 20 is a diagram showing media costs for various link costs from the perspective of terminal F 20F.

[0036] The link cost between the terminal F 20F and the terminal A 20A is 8 on the receiving side and 23 on the sending side. The routing cost of the terminal A 20A (referred to as "upper routing cost"), that is, the media (medium) cost indicating the reception quality between the terminal A 20A and the main terminal M10 is 11, so the temporary routing cost of the terminal F 20F via the terminal A only considers the link cost on the receiving side, which is 19 (=8+11). In addition, the routing cost of the terminal F 20F via the terminal A also considers the link cost on the sending side (because the link cost on the sending side is greater than the link cost on the receiving side), which is 34 (=23+11).

[0037] The link cost between the terminal F 20F and the terminal C 20C on the receiving side is 28. The routing cost of the terminal C 20C is 20, so the terminal F 20F passes through the temporary routing cost of the terminal C and the routing cost is 48.

[0038] The link cost between the terminal F 20F and the terminal D 20D on the receiving side is 6. The routing cost of the terminal D 20D is 30, so the terminal F 20F passes through the temporary routing cost of the terminal D and the routing cost is 36.

[0039] The link cost between terminal F 20F and terminal E 20E is 7 on the receiving side and 5 on the sending side. The routing cost of terminal E 20E is 16, so the temporary routing cost of terminal F 20F via terminal E only considers the link cost on the receiving side, which is 23. In addition, the routing cost of terminal F 20F via terminal E also considers the link cost on the sending side (because the link cost on the receiving side is greater than the link cost on the sending side), which is 23.

[0040] Based on the above media cost, the main terminal M10 sets a path from the terminal E 20E to the terminal F 20F, that is, a relay path of the terminal A 20A - the terminal E 20E - the terminal F 20F. Therefore, between the main terminal M10 and the terminal F 20F, the unicast frame is relayed (forwarded) via the above relay path that is set. In this way, in the above multi-hop communication system, regarding the relay (forwarding) of the unicast frame, the relay path is optimized based on the number of relays and the forwarding path of the relay path so that the media cost is minimized and the media occupation time required for the relay (forwarding) is minimized.

[0041] On the other hand, regarding broadcast frames, the target frame needs to be transmitted to all terminals. Therefore, after a broadcast frame transmitted from a certain terminal is received by the master terminal and all relay terminals, these terminals forward the target frame by broadcasting it again to other terminals.

[0042] For example, as the number of relay terminals increases, the media resources required to send a broadcast frame also increase. In addition, for broadcast frames, the communication rate is the lowest due to the implementation of modulation that maximizes robustness. Therefore, in a multi-hop communication system, sending multicast frames consumes huge media resources.

[0043] It should be noted that broadcast communication and multicast communication are not strictly the same, but in this specification, they are used with substantially the same meaning.

[0044] In the case where a communication frame has the characteristic that "when a frame in which the same data is sent from multiple terminals, degradation in the CINR (Carrier to Interference and Noise Ratio) of the received signal due to interference between the transmission signals of the multiple terminals is equivalent to inter-symbol interference due to group delay" (for example, a frame of HD-PLC), if it is a frame with high robustness such as broadcasting, it can be sent to multiple terminals at the same time, compared with a case in which transmission is performed from one terminal by synchronizing the timing between the transmitting terminals and sending. This can shorten the media occupancy time.

[0045] In addition, for example, Figure 1A In the illustrated example, if the broadcast frames are transmitted synchronously from the terminal A 20A and the terminal B 20B, even if a collision occurs, the received frame will have a CINR that does not cause an error, and the terminal C 20C can receive the broadcast frame.

[0046] Furthermore, if all terminals in the system are scheduled to synchronize their time so as to be terminals that transmit appropriately and / or at transmission timings, the number of transmissions and media occupation costs can be reduced.

[0047] Based on the above, a technology that can appropriately perform broadcast transmission via a wired or wireless communication network is described.

[0048] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings as appropriate. However, unnecessary detailed descriptions may be omitted sometimes. For example, a detailed description of a well-known matter or a substantially identical structure may be omitted for repeated description. This is to avoid the following description from being unnecessarily lengthy and to make it easy for those skilled in the art to understand.

[0049] It should be noted that the 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.

[0050] (Implementation Method)

[0051] <Communication system structure>

[0052] Figure 2 1 is a diagram showing a configuration example of a communication system 1 according to an embodiment of the present disclosure. The communication system 1 may be, for example, an HD-PLC system.

[0053] like Figure 2 As shown, the communication system 1 includes a main terminal M10 and terminals A to F 20A to 20F (terminals A to E 20A to 20E: relay terminals, terminals F to 20F: end terminals). The number and connection form of the terminals constituting the communication system 1 (communication network) are not limited to those shown in the figure.

[0054] The communication system 1 can be configured, for example, in water (for example, in the sea). When the communication system 1 is configured in this manner, for example, a control device (not shown) can be connected to the main terminal M10, and electronic devices such as sensors controlled by the control device (not shown) can be connected to the terminals A to F 20A to 20F respectively. Alternatively, the communication system 1 can also be used in facilities such as factories or office buildings. When the communication system 1 is configured in this manner, a control device (not shown) can be connected to the main terminal M10, and electronic devices such as sensors, lighting equipment, and air conditioners controlled by the control device can be connected to the terminals A to F 20A to 20F respectively. It should be noted that electronic devices may not be connected to a part of the terminals A to F 20A to 20F, and the terminals A to F 20A to 20F that are not connected to electronic devices can function as repeaters (transponders).

[0055] It should be noted that these main terminal M10 and terminals A~F 20A~20F may be collectively referred to as "communication terminal" or simply "terminal 100", collectively referred to as "communication node" or simply "node 100", collectively referred to as "communication equipment" or simply "equipment 100", collectively referred to as "communication device" or simply "device 100", collectively referred to as "communication terminal" or simply "terminal 100", etc. In addition, the main terminal may be referred to as "mother machine", "mother terminal", "master station", "router", "router terminal", etc., and the terminals A~F 20A~20F may be referred to as "slave machine", "slave terminal", "terminal", etc.

[0056] In the communication system 1 , each terminal 100 (the master terminal M10 and each of the terminals AF 20A to 20F) performs multi-hop communication using PLC that uses a power line as a communication path and superimposes a signal on the power line.

[0057] For example, in Figure 1A , the jump number (counted from the main terminal M10) of the terminal A 20A and the terminal B 20B is 1, the jump number (counted from the main terminal M10) of the terminal C 20C, the terminal D 20D, and the terminal E 20E is 2, and the jump number (counted from the main terminal M10) of the terminal F 20F is 3. It should be noted that, although the upper limit of the jump number is set to 10 in the embodiment and the maximum number of terminals that can be connected to the communication system 1 is 1024, the upper limit of the jump number and the maximum number of terminals are not limited to these values.

[0058] In the communication system 1, the main terminal M10 collects predetermined information from the terminals A to F 20A to 20F, and remotely monitors or remotely controls the terminals A to F 20A to 20F. Here, the main terminal M10 and each terminal A to F 20A to 20F communicate directly or indirectly, and the terminals A to F 20A to 20F that cannot communicate directly with the main terminal M10 communicate indirectly with the main terminal M10 by sequentially relaying communication signals to other terminals A to F 20A to 20F that can communicate directly.

[0059] As described below, each terminal 100 (the main terminal M10 and the terminals A to F 20A to 20F) calculates a link cost indicating the communication quality (also referred to as "link quality") with other terminals, and communicates with other terminals based on the link cost. For example, between the main terminal M10 and the terminals A to F 20A to 20F, a unicast frame may be relayed (transmitted) on a path (route) with the best (lowest) media cost between these terminals. In addition, a synchronization frame may also be relayed between terminals based on the media cost between the terminals.

[0060] It should be noted that the communication method in the communication system 1 is not limited to PLC which is a wired communication method, and may be a wired communication method other than PLC or a wireless communication method as long as multi-hop communication is possible.

[0061] <Terminal structure>

[0062] Figure 3 It is a diagram showing a hardware configuration example of the terminal 100 according to the present embodiment.

[0063] like Figure 3 As shown, the terminal 100 includes a central processing unit (CPU) 201, a storage device 202, a communication device 203, and a device interface device 204. The terminal 100 may include components other than those described above.

[0064] CPU 201 controls the overall operation of terminal 100 (for example, communication performed by communication device 203 and processing performed by various structural elements). CPU 201 implements various functions of terminal 100 (including processing described later) by, for example, loading a prescribed program stored in a HDD (Hard Disk Drive), SSD (Solid State Drive), etc. contained in storage device 202 into a RAM (Random Access Memory) contained in storage device 202 and executing the program. The program executed by CPU 201 may be pre-stored in storage device 202, or may be provided through an electrical communication line such as the Internet, or may be provided by being stored in a non-temporary storage medium such as a memory card.

[0065] The storage device 202 is a non-temporary storage medium, including non-volatile memories such as HDD, SSD, ROM (Read Only Memory), electrically erasable non-volatile memories such as EEPROM (Electrically Erasable Programmable Read Only Memory), and volatile memories such as RAM. The storage device 202 stores information related to communication paths, topology information, and communicable terminals (e.g., other terminals that can communicate directly), etc. (e.g., in a table form). The storage device 202 also stores programs such as a control program for operating the terminal 100, data required to execute the program, identification information of the terminal 100, and other information / data that has been processed (processed) by the terminal 100 (e.g., CPU 201).

[0066] When the terminal 100 is the main terminal M10, the storage device 202 stores, for example, a communication path data table for registering all communication paths between terminals constructed in the network, a topology structure table for recording information (link information) of adjacent terminals that can directly communicate with each terminal, and the like.

[0067] In addition, when the terminal 100 is a terminal A~F 20A~20F, the storage device 202 stores, for example, a communicative terminal data table indicating adjacent terminals with which the terminal 100 can communicate, a communication cost value (link cost) indicating the communication quality between the terminal 100 and the adjacent terminals, and a communication cost value (routing cost) indicating the communication quality between the terminal 100 and the main terminal M10 via the adjacent terminals.

[0068] 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 PLC. It should be noted that when a wired communication method or a wireless communication method other than PLC is used as a communication method, the communication device 203 may be a communication interface device corresponding to the wired communication method or the wireless communication method. The communication device 203 is an example of a receiving unit and a transmitting unit of the present disclosure.

[0069] The device interface device 204 is an interface device for exchanging (inputting and outputting) data with a control device or an electronic device connected to the terminal 100. The device interface device 204 may be a communication interface device conforming to the Ethernet (registered trademark) standard, for example.

[0070] Figure 4 It is a diagram showing a functional configuration example of the CPU 201 according to the present embodiment.

[0071] The CPU 201 includes a packet analysis unit 301 , an authentication processing unit 302 , a link cost calculation unit 303 , a topology management unit 304 , a packet generation unit 305 , and a synchronization control unit 306 .

[0072] CPU201 is input with call packets (H packets: Hello packets) (also called "call messages" or "call signals"), authentication packets, synchronization packets and normal packets. The H packets are sent from one terminal to the connected terminals at the same time before the authentication process is performed in the communication system 1 (communication network). In addition, H packets are also sent or sent to adjacent terminals periodically by each terminal to update path information (such H packets can also be called "periodic signals"). H packets can refer to packets that notify the existence of the terminal itself. For example, the H packet contains identification information of the main terminal in the network, information on the source of the H packet, information on the adjacent terminals of the terminal itself, information on the communication quality of the link, etc. The authentication packet is a packet sent and received during the authentication process, the synchronization packet is a packet used for time synchronization of synchronization (Sync) packets, tracking (Follow Up) packets, etc., and the normal packet can be, for example, sensor data obtained by a sensor.

[0073] The packet analysis unit 301 analyzes the data structure of various input packets (H packets, authentication packets, synchronization packets, and normal packets) to determine the type of the packets, and assigns the forwarding destination of the packets based on the determination result. For example, when the packet analysis unit 301 determines that the input packet is an H packet, it outputs the H packet to the link cost calculation unit 303. For example, when 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, when 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. For example, when the packet analysis unit 301 determines that the input packet is a synchronization packet, it outputs the synchronization packet to the synchronization control unit 306.

[0074] The authentication processing unit 302 performs authentication processing with the terminal that sent the authentication packet using the authentication packet input from the packet analysis unit 301. The authentication processing unit 302 outputs the authentication packet generated during the authentication processing or the response to the authentication packet sent from another terminal to the topology management unit 304.

[0075] The link cost calculation unit 303 calculates the link cost indicating the reception quality of the H packet received by the terminal from the terminal of the transmission source using the H packet input from the packet analysis unit 301. The link cost calculation unit 303 writes (stores) the calculation result of the link cost into the data structure of the H packet. In addition, the value of each link cost when the H packet is transmitted from the master terminal M10 is also stored in the H packet. The link cost calculation unit 303 outputs the H packet storing the calculation result of the link cost to the topology management unit 304.

[0076] The topology management unit 304 manages (acquires) topology information representing the topology generated by the main terminal M10 (i.e., the terminals constituting the communication system 1 and their connection method), and assigns the output destinations of various packets (e.g., the packet generation unit 305) and outputs them based on the topology information. The topology information is stored in the topology management unit 304 or the storage device 202 of each terminal. In addition, the topology management unit 304 causes the topology management unit 304 or the storage device 202 to store the above-mentioned information related to the communication path, the terminals that can communicate (e.g., other terminals that can communicate directly), the terminal itself, etc. in addition to the topology information. It should be noted that the topology management unit 304 of the main terminal M10 generates (forms) a topology based on the link costs calculated by the link cost calculation unit 303 of the main terminal M10 based on the H packets respectively sent from one or more terminals that become the object of authentication processing, and provides the topology information representing the topology to other terminals.

[0077] The packet generation unit 305 generates and outputs a packet for data communication, an H packet, etc., to another terminal as a transmission destination, based on the authentication packet or the normal packet input from the topology management unit 304 .

[0078] The synchronization control unit 306 performs control related to time synchronization in the communication system 1. The synchronization control unit 306 performs such control in accordance with, for example, IEEE1588 (PTP Ver2), which is a standard for achieving time synchronization with nanosecond accuracy in a tree-structured network.

[0079] IEEE1588 is a standard that specifies how to accurately transfer high-precision time information from a master clock to a client clock via an asynchronous packet network. It should be noted that in IEEE1588, the OC clock can be synchronized with the OC master clock by connecting the Ordinary Clock Master (OC Master) serving as the system's clock source and the Ordinary Clock Slave (OC Slave) that maintains a clock synchronized with the OC Master via a network such as Ethernet to an End to End Transparent Clock (E2E TC) node or a Peer to Peer Transparent Clock (P2P TC) node serving as a relay node. For example, in this embodiment, if Figure 7 As shown, a communication system 1 can be connected between an OC master station and an OC slave station.

[0080] In this embodiment, a P2P TC is used. The P2P TC uses P delay_Req Frame, P delay_Resp Frame and Pdelay_Resp_Follow_Up The transmission path delay (also called "transmission delay") between terminals is measured in advance, and the delay information is added when the synchronization frame is forwarded to correct the clock error. The reason is that if the transmission delay of the adjacent link has been measured once, there is no need to measure it again if the transmission delay has not changed. The clock correction can be performed by forwarding the synchronization packet and the tracking packet in one direction, which is beneficial to the PLC with shared communication medium. Of course, E2E TC can also be used.

[0081] It should be noted that, hereinafter, the term "frame" may be replaced by terms such as "packet", "message", and "signal" as appropriate.

[0082] The synchronization control unit 306 generates these P delay_Req Frame, P delay_Resp Alternatively, the synchronization control unit 306 may cause the packet generation unit 305 to generate such a frame and transmit it to the communication partner terminal.

[0083] The synchronization control unit 306 performs transmission path delay measurement and time stamp acquisition as described below to achieve time synchronization.

[0084] The synchronization control unit 306 adjusts the clock of its own terminal based on information on the measured transmission path delay and the like.

[0085] The synchronization control unit 306 of the relay terminal synchronizes the timing of broadcasting frames of other relay terminals in the communication system 1 (for example, other relay terminals in the same hop as the relay terminal in the communication system 1) with the timing of broadcasting frames of the relay terminal.

[0086] The synchronization control unit 306 is an example of a synchronization control unit or a (broadcast) transmission control unit in the present disclosure.

[0087] <Communication system operation>

[0088] Next, operations related to broadcast synchronous transmission of the communication system 1 will be described.

[0089] [Synchronization based on IEEE1588]

[0090] - About the relay of synchronization frames

[0091] TC includes one-step TC and two-step TC. One-step TC can hard embed the timestamp of the synchronization point of the transmission frame when transmitting the synchronization frame, but two-step TC cannot. In this embodiment, two-step TC is used, but one-step TC can also be used.

[0092] The synchronization message generated by the upstream ordinary clock master station arrives at the TC slave port. The synchronization message includes a single-step synchronization message with the sending time embedded in the synchronization message, and a double-step synchronization message with no sending time embedded in the synchronization message but a tracking message containing the sending time information is sent after the synchronization message.

[0093] When the one-step synchronization message arrives at the terminal corresponding to the two-step TC, the synchronization control unit 306 of the terminal first changes only the twoStepFlag in the synchronization message to True, and sends the synchronization message to the downstream terminal as soon as possible. At this time, the synchronization control unit 306 records the arrival time (dt1) of the synchronization message and the synchronization sending time (dt2) (for example, recorded in the synchronization information storage area of ​​the storage device 202). Next, the synchronization control unit 306 generates a tracking message based on the information of the synchronization message as described in 11.5.2.2 of IEEE 1588-2008, adds the residence time (=dt2-dt1) to the transmission path delay (peerMeanPathDelay) between the terminal that sent the synchronization message and its own terminal, saves the obtained value in the collection field (CF), and sends the tracking message to the downstream terminal. It should be noted that the measurement of the transmission path delay (peerMeanPathDelay) will be described later.

[0094] On the other hand, when the two-step synchronization message arrives at the terminal corresponding to the two-step TC, the synchronization control unit 306 of the terminal directly sends the synchronization message to the downstream terminal as soon as possible. At this time, the synchronization control unit 306 records the arrival time (dt1) of the synchronization message and the synchronization sending time (dt2) (for example, recorded in the synchronization information storage area of ​​the storage device 202). Next, when the tracking message arrives at the terminal, the synchronization control unit 306 of the terminal adds the residence time (=dt2-dt1) to the transmission path delay (peerMeanPathDelay) between the terminal that sent the synchronization message and its own terminal, saves the obtained value in the collection field (CF), and sends the tracking message to the downstream terminal.

[0095] - Measurement of transmission path delay (peerMeanPathDelay)

[0096] As described above, when relaying a synchronization message, the P2P TC relay device (terminal) needs to store the value of the transmission path delay (peerMeanPathDelay) used by the source terminal of the synchronization message in the CF and send it. Therefore, the transmission path delay is measured at the time when the synchronization message sending terminal is identified. delay_Req Frame, P delay_Resp Frame and P delay_Resp_Follow_UpThe terminal that wants to know the transmission path delay is called a "requester", and the terminal that becomes the target is called a "responder".

[0097] The requester (synchronous control unit 306) sends P delay_Req The frame is transmitted to the responder, and the transmission time is recorded as t1 (for example, recorded in the synchronization information storage area of ​​the storage device 202).

[0098] The responder (synchronous control unit 306) receives the P delay_Req The time of the frame is recorded as t2 (for example, recorded in the synchronization information storage area of ​​the storage device 202). Then, the responder (the synchronization control unit 306) generates P delay_Resp The requester (synchronous control unit 306) sends the received P frame to the requester, and records the sending time as t3 (for example, recorded in the synchronization information storage area of ​​the storage device 202). delay_Resp The time of the frame is recorded as t4 (for example, recorded in the synchronization information storage area of ​​the storage device 202).

[0099] Then, the responder (synchronous control unit 306) stores D2=t3-t2 in P delay_Resp_Follow_Up The requester (the synchronization control unit 306) can thereby obtain the transmission path delay in the form of peerMeanPathDelay={(t4-t1)-(t3-t2)} / 2.

[0100] The number of times the transmission path delay is measured may be basically once when the synchronization message transmission starts and once when the synchronization message transmission source is changed.

[0101] - Timestamp acquisition

[0102] In an Ethernet device that implements IEEE1588, when the head of the MAC header of a packet exceeds the boundary between the device and the line, the time is taken (acquired) as a timestamp. Figure 5 When the head of the "Tail" after the "Tone Map Index (TMI)" shown by the arrow exceeds the boundary between its own terminal and the line, a trigger signal is notified to the timer of its own terminal, and this moment is taken (acquired) as a timestamp.

[0103] Figure 6 This is a flowchart showing an example of acquiring a time stamp when receiving a frame.

[0104] In step S601, a terminal (eg, a responder) starts receiving frames.

[0105] In step S602, the synchronization control unit 306 of the terminal determines whether the reception of the TMI symbol in the frame has been completed.

[0106] When the reception of the TMI symbol is not completed within the frame (step S602; NO), the flow returns to step S602.

[0107] On the other hand, when the reception of the TMI symbol has been completed in the frame (step S602; YES), in step S603, the synchronization control unit 306 of the terminal acquires a time stamp.

[0108] It should be noted that regarding acquisition of a timestamp when a frame is transmitted (for example, when a frame is transmitted by a requester), the above-mentioned "receive" may be replaced with "transmit".

[0109] The time stamps acquired in the above manner are recorded in the form of the above-mentioned time (for example, t1 to t4).

[0110] In this embodiment, synchronization packets (i.e., broadcast packets) are based on the relay path information of unicast packets (information called "routing information" collected to create a multi-hop topology, such as Figure 1A and Figure 1B The same information as shown in the figure is relayed. Figure 7 In the example shown, Figure 1A and Figure 1B As shown, the broadcast routing information shown in bold is formed based on the communication cost evaluation result between the terminals. As a result, the number of forwarding times can be reduced to four for all path relays. In addition, no loop occurs. It should be noted that after all terminals are synchronized, the number of forwarding times is reduced to three.

[0111] In this way, in a communication system where multiple relay paths may exist from a master terminal to an end terminal, it is possible to suppress or prevent synchronization packets from being relayed in all directions and looping infinitely, or from causing unnecessary synchronization packet relays.

[0112] In this embodiment, each terminal stores the following information in the topology management unit 304 or the storage device 202 .

[0113] Whether the terminal is a relay terminal

[0114] One upper relay terminal that receives the packet from the master terminal (it should be noted that there must be only one upper relay terminal) (part of the routing information)

[0115] ·Lower terminals (0 to n) that relay packets from the master terminal (part of routing information)

[0116] By using the above information, the relay source of each path is set as the virtual TC master port, and the relay destination is set as the virtual TC slave port, so that the synchronous packet relay route can be constructed.

[0117] Figure 8 Yes means Figure 7 A diagram showing a virtual TC master port and a virtual TC slave port of a path in the example shown. It should be noted that in the diagram, M represents a virtual TC master port and S represents a virtual TC slave port.

[0118] In this way, by using the multi-hop system information, the IEEE1588 topology can be efficiently constructed on the system. In the example shown in the figure, the synchronization packet sent from the TC master port is a multicast packet, so the number of synchronization packets during one synchronization is four (from the master terminal M10 to the terminal A 20A and the terminal B 20B, from the terminal A 20A to the terminal C 20C and the terminal E 20E, from the terminal B 20B to the terminal D 20D, and from the terminal E 20E to the terminal F 20F).

[0119] In the present embodiment, frames from terminals other than one upper terminal of the own terminal may also arrive, so the TC slave (port) performs the following processing.

[0120] Obtain the upper terminal information and discard the synchronization frame and tracking frame whose transmission source is other than an upper terminal.

[0121] ·Use unicast frames to delay_Req The frame is sent to the upper terminal.

[0122] When the terminal is a relay terminal or a master terminal and receives P delay_Req In the case of unicast frames, only unicast P delay_Req Frame, replace the source address and destination address and send unicast delay_Resp Frame and P delay_Resp_Follow_Up frame.

[0123] ·On ​​receiving P delay_Resp Frame and P delay_Resp_Follow_Up In the case of unicast frames, only unicast P delay_Resp Frame and P delay_Resp_Follow_Up Frames, discarding multicast P delay_Resp Frame and P delay_Resp_Follow_Up frame.

[0124] In addition, in the present embodiment, in order to prevent synchronization packets from being relayed via a path unrelated to its own terminal, the TC master (port) performs the following processing.

[0125] In the initial state, synchronization packets and identical packets are not sent.

[0126] Announces are bridged according to the normal PLC frame rules.

[0127] The terminal that recognizes the notification confirms whether the upper terminal exists. If the upper terminal exists, it sends P delay_Req frame.

[0128] · In the acceptable P delay_Resp Frame, P delay_Resp_Follow_Up In the case of frames, the terminal confirms the number of lower terminals, and when there is more than one lower terminal, the synchronization frame and tracking frame are bridged (unless the network is reconfigured, bridging continues).

[0129] When the network is reconfigured (when the topology changes), it becomes the initial state.

[0130] Therefore, even in PLC (such as HD-PLC) using one communication medium, multiple virtual communication paths can be constructed.

[0131] - Global clock function

[0132] Terminals that support IEEE1588 do not need to match the timer of their own terminals (also called "self-terminal timer" or "self-timer") with the global time, but can also use the relayed synchronization packet or the transmission delay information obtained as a TC function to match the self-timer with the global time.

[0133] Therefore, each terminal sniffs the two-step synchronization message and the tracking message to adjust the time of the timer of its own terminal and correct the clock cycle. In addition, optionally, the master terminal can generate the two-step synchronization message and the tracking message so that synchronization can be achieved even if the ordinary clock master station does not exist.

[0134] - Timer time adjustment

[0135] As described above, the IEEE1588-supporting terminal with TC function has transmission path delay information (peerMeanPathDelay) (pt1), two-step synchronization message reception time (dt1), collection field (CF1) in the two-step synchronization message, two-step synchronization message sending time in the tracking message (t1), and collection field (CF2) in the tracking message.

[0136] If the time of receiving the two-step synchronization message in the ordinary master clock is set to tx, then since tx=t1+CF1+CF2+pt1, the correction value g of the own terminal clock (self-clock) relative to the ordinary master clock can be calculated as follows.

[0137] g=t1+CF1+CF2+pt1-dt1

[0138] Based on the delay information and time information, the clock of the terminal is adjusted (corrected) to the common master clock. It should be noted that in this embodiment (eg, HD-PLC), since the medium is shared across the entire system, it is desirable to minimize the number of packets required for correction.

[0139] Corrections include time correction and clock cycle correction.

[0140] Regarding the time correction, after receiving the synchronization packet and the corresponding tracking packet and performing the forwarding process of the packets, the synchronization control unit 306 performs control so as to use the time offset correction value g.

[0141] Regarding the clock cycle correction, the synchronization control unit 306 calculates the corrected value g0 of the time and the corrected evaluation time A. t The corrected value after g t , find the error change d t =g t -g 0 And control is performed in such a way that the clock period T is corrected to T·(1+α·dt / At).

[0142] For example, when the performance of the clock transmitter is 50ppm, the synchronization period is set to 15 seconds, At (error change measurement time) is set to 15 seconds, and α (clock synchronization correction coefficient) is set to 2.1600499167 (1000000000×4.638671875×2 / 4294967296). After a correction period of 30 seconds, the ordinary master clock can be synchronized with the self-clock with an accuracy of 100 nanoseconds.

[0143] [General operation example of broadcast synchronization]

[0144] Assuming that the clock synchronization of all terminals in the communication system 1 has been established by applying IEEE1588 as described above, an example of the action process for improving efficiency when multiple terminals simultaneously (synchronously) send broadcast frames in a clock-synchronized state is described. In the following description, the frame format of IEEE1901-2020 that HD-PLC complies with is described as an example of a communication frame. It should be noted that the communication frame format of IEEE1901-2020 is in the TTC (Telecommunication Technology Committee) standard JJ-300.20v2. Figure 7 The same communication frame format is also defined in .38 (FCW MPDU frame format). Fig. 9It indicates TTC standard JJ-300.20v2 Figure 7 .38(IEEE1901-2020 Figure 6 -17) is a diagram of a communication frame format example of an embodiment of the present disclosure.

[0145] As a restriction of using simultaneous broadcast frame transmission, the transmission data of the frames transmitted simultaneously must be the same. Therefore, the transmission (communication) frame format can adopt the following structure.

[0146] ·Destination address in the frame ( Fig. 9 The DA (Destination Address) shown is fixed to the broadcast address (FF-FF-FF-FF-FF-FF) or a specific multicast address (01-00-5E-XX-XX-XX) (XX-XX-XX is an arbitrary value specified by the system).

[0147] · The source address in the frame ( Fig. 9 The SA (Source Address) shown is the address (initial transmission source address) of the terminal that initially transmits the broadcast frame (hereinafter referred to as the "initial transmission terminal") (not the address of the relay terminal).

[0148] Initialization vector in frame ( Fig. 9 The IV (Initialization Vector) shown is generated by the initial sending terminal and is the same (copied) in all relay frames.

[0149] It should be noted that IV can be used as a seed for encrypting frames. For example, in the case of broadcast communication from a master terminal, by notifying the relay terminal of the IV generated by the master terminal, the broadcast frames generated by each relay terminal become the same. As a result, the frames sent simultaneously from each relay terminal are the same, so even if a conflict occurs, other terminals can receive the frames.

[0150] Fig.10 This is a flowchart showing a general operation example of broadcast frame synchronous transmission. It should be noted that appropriate values ​​are appropriately set (stored) for other fields in the frame other than the fields described below.

[0151] In step S1001, the synchronization control unit 306 of the terminal stores a broadcast address (FF-FF-FF-FF-FF-FF) or a specific multicast address (01-00-5E-XX-XX-XX) in the transmission destination address of the frame.

[0152] In step S1002, the synchronization control unit 306 of the terminal stores the address of the initial transmitting terminal in the transmission source address of the frame.

[0153] In step S1003, the synchronization control unit 306 of the terminal determines whether the terminal itself is an initial transmitting terminal.

[0154] When the terminal itself is the initial transmission terminal (step S1003; Yes), in step S1004, the synchronization control unit 306 of the terminal generates IV and stores it in the frame.

[0155] On the other hand, when the terminal itself is not the initial transmitting terminal (step S1003; No), in step S1005, the synchronization control unit 306 of the terminal copies IV from the received (broadcast) frame and stores it in the frame.

[0156] In step S1006, the synchronization control unit 306 of the terminal broadcasts the frame generated by storing the information as described above.

[0157] [Broadcast synchronization sending operation example 1]

[0158] In the first example of the operation process, the initial transmitting terminal obtains the transmission right by backing off, etc., and transmits the first broadcast frame. Figure 2 The main terminal M10 is shown.

[0159] Next, the relay terminal (eg, Figure 2 The terminal A 20A and the terminal B 20B shown in the figure add the interval time calculated according to the frame length to the reception start time, and relay the broadcast frame at the time of the addition result. It should be noted that even if the relay terminal receives a frame that has been relayed once from other terminals, it will not retransmit it.

[0160] The same operation is repeated thereafter. That is, the relay terminal that receives the broadcast frame transmitted by the relay terminal transmits the broadcast frame as described above.

[0161] According to the above operation process example 1, the media occupation time caused by broadcast transmission can be reduced by synchronously transmitting broadcast frames at locations (e.g., terminal A 20A and terminal B 20B) with the same number of hops from the initial transmission terminal (e.g., main terminal M10). Figure 2 In the example shown, Fig.11 As shown, three broadcast transmissions can be completed, which can reduce the media occupancy time. In addition, by sending broadcast frames synchronously, conflicts are not generated or suppressed. For example, Figure 2 The terminal C 20C shown has a higher probability of being able to receive the broadcast frame. In addition, by acquiring synchronization in accordance with IEEE1588 as described above, synchronization can be achieved with high accuracy.

[0162] [Broadcast synchronization sending operation example 2]

[0163] In this action process example 2, in addition to the above-mentioned action process example 1, the following contents are added.

[0164] The initial sending terminal is set as the master terminal. Therefore, when a terminal other than the master terminal desires to send a broadcast frame, the terminal (for example, terminal C 20C) converts the broadcast frame into a unicast frame addressed to the master terminal (master terminal M10) and sends the unicast frame to the master terminal (for example, via terminal A 20A). This situation is shown in Fig.12 It should be noted that the unicast frame sent by the terminal to the master terminal may include information (such as a flag) indicating that a broadcast frame is sent (from the master terminal).

[0165] Then, the master terminal that receives the unicast frame restores (reconverts) the unicast frame into a broadcast frame and sends it. Fig.12 The time interval is [t1, t3] (same as action process example 1).

[0166] Furthermore, the master terminal calculates the maximum number of relay times according to the topology information, and does not send the next frame before the time required to complete the relay ends.

[0167] According to the above-mentioned operation process example 2, the conflict between different broadcast frames can be completely avoided. For example, it can avoid the situation where multiple terminals in the hidden terminal state cannot grasp each other's communication status and start broadcast transmission at the timing of communication overlap, resulting in a conflict and causing the conflicting frames to be directly lost.

[0168] [Broadcast synchronization sending operation example 3]

[0169] In this operation procedure example 3, the broadcast-only transmission period is periodically set. It should be noted that when this operation procedure example 3 is applied, at least a part of the above-mentioned operation procedure example 1 or 2 is applied.

[0170] More specifically, under specific conditions at the current moment in the system (i.e., the time when specific conditions are met (broadcast-dedicated transmission period)), transmission is basically suppressed (at least unicast transmission is not performed), and the main terminal and relay terminal send broadcast frames under specific conditions at the current moment.

[0171] For an example of such transmission control, refer to Fig.13 Provide explanation.

[0172] In this example, a broadcast transmission period of 5 milliseconds is set in a cycle of 50 milliseconds.

[0173] The value representing the current time in milliseconds is defined as β, and transmission is basically suppressed during the period of 0≦βmod 50≦5.

[0174] ID: 0 is assigned to the main terminal, and ID: N is assigned to the relay terminal of the Nth hop (Nth segment), and the terminal assigned with this ID sends a broadcast frame during the period of floor(β / 50)mod(M+1)=ID (the maximum value of N is set to M). It should be noted that N represents the number of hops of the relay terminal (the number of hops does not include the main terminal and the end terminal).

[0175] Fig.13 It means that when M=2 (for example, Figure 1A 3. A diagram showing an example of a broadcast frame being sent during a broadcast-only period in a three-hop multi-hop system (as shown in FIG. 4 ).

[0176] like Fig.13 As shown, during the broadcast transmission period P0, the main terminal performs broadcast transmission, during the broadcast transmission period P1, the first-hop relay terminal performs broadcast transmission, and during the broadcast transmission period P2, the second-hop relay terminal performs broadcast transmission.

[0177] In the above, an example of assigning ID: 0 to the main terminal is shown, but the present disclosure is not limited to this example. ID: 0 may be assigned to the initial transmission terminal, and ID: K may be assigned to the terminal located at the Kth hop from the initial transmission terminal.

[0178] According to the above operation process example 3, it is possible to avoid collision between broadcast frames and unicast frames. For example, it is possible to avoid a situation where a collision occurs when one terminal starts to send a broadcast frame and another terminal starts to send a unicast frame, and the conflicting broadcast frame is lost.

[0179] [Broadcast synchronization sending operation example 4]

[0180] In this operation process example 4, the broadcast dedicated transmission period is periodically set as in the above operation process example 3, but the conditions on the broadcast frame transmission terminal are changed. It should be noted that when this operation process example 4 is applied, at least part of the above operation process examples 1, 2 and 3 are applied.

[0181] For an example of such transmission control, refer to Fig.14A and Fig. 14B Provide explanation.

[0182] In this example, a broadcast transmission period of 5 milliseconds is set in a cycle of 50 milliseconds.

[0183] The value representing the current time in milliseconds is defined as β, and transmission is basically suppressed during the period of 0≦βmod 50≦5.

[0184] like Fig.14AAs shown, the main terminal is assigned ID: 0, and the relay terminal of the Nth hop (Nth segment) is assigned ID: N mod k. And, during the period floor(β / 50)mod(L+1)=ID (the maximum value of N mod k is set to L), the terminal assigned with the ID sends a broadcast frame. It should be noted that N represents the number of hops of the relay terminal (the number of hops does not include the main terminal).

[0185] Fig. 14B This is a diagram showing an example of broadcast frame transmission in a broadcast-only period when N=10 and k=4.

[0186] like Fig. 14B As shown, during the broadcast transmission period P0, the main terminal assigned with ID: 0 and the relay terminals of the fourth hop and the eighth hop perform broadcast transmission, during the broadcast transmission period P1, the relay terminals of the first hop, the fifth hop and the ninth hop assigned with ID: 1 perform broadcast transmission, during the broadcast transmission period P2, the relay terminals of the second hop, the sixth hop and the tenth hop assigned with ID: 2 perform broadcast transmission, and during the broadcast transmission period P3, the relay terminals of the third hop and the seventh hop assigned with ID: 3 perform broadcast transmission.

[0187] Here, we study terminal N 2 If broadcast frames are continuously sent from the master terminal M, then at a certain moment, the terminal N 1 With terminal N 9 、N 10 、N 11 Send different broadcast frames simultaneously (synchronously). However, terminal N 1 With terminal N 2 There is one hop between them. In contrast, the terminal N 2 With terminal N 9 、N 10 、N 11 Therefore, terminal N 1 The broadcast frame will not affect the terminal N that sends it at the same time. 9 、N 10 、N 11 broadcast frames, and vice versa.

[0188] Therefore, different broadcast frames may be sent simultaneously between terminals with different hop numbers assigned the same ID, but this will not cause reception errors. This is because, due to the nature of the multi-hop topology, if the relay hop number distance is greater than a certain distance, the transmission wave will inevitably attenuate. As a result, the relay time can be made L / M, and the throughput can be made M / L times.

[0189] It should be noted that k can be set to a sufficiently large value based on empirical rules, or it can be calculated and set by the main terminal based on the current attenuation state between terminals (CINR value between terminals, PHY (Physical layer) speed, etc.), or it can be set by other methods.

[0190] As described above, according to operation procedure example 4, it is possible to avoid collision between broadcast frames and unicast frames, suppress an increase in the time required for relaying broadcast frames when the number of relay hops increases, and suppress a decrease in throughput.

[0191] The above-mentioned operation process examples 1 to 4 can be switched according to the application program. In addition, the above-mentioned operation process examples 1 to 4 do not need to be installed in the terminal.

[0192] For example, as a protocol for an application, when the communication medium occupancy time is extremely small and the terminal does not generate a communication packet at the same time, action process example 1 can be used or only action process example 1 can be installed. In addition, in an application in which only the main terminal sends broadcast frames, action process example 1 can be used or only action process example 1 can be installed.

[0193] <Effects of implementation>

[0194] The relay terminal (e.g., terminal A 20A) of the present embodiment is a relay communication device in the communication system 1 that performs multi-hop communication. The communication device 203 of the relay terminal receives a frame broadcasted from the first terminal (e.g., main terminal M10) in the communication system 1, and broadcasts the frame. The synchronization control unit 306 of the relay terminal synchronizes the timing of broadcasting the frame of the third terminal (e.g., terminal B 20B) in the communication system 1 that receives the frame broadcasted from the first terminal with the timing of broadcasting the frame of the communication device 203 of the relay terminal. According to the present embodiment, by broadcasting the frame with synchronization of timing between the relay terminal (e.g., terminal A 20A) and the second terminal (e.g., terminal B 20B), the media occupancy time can be shortened. In addition, according to the present embodiment, since the broadcast frame is synchronously transmitted from the relay terminal and the second terminal, a conflict does not occur or is suppressed, and the possibility that the third terminal (e.g., terminal C 20C) in the communication system 1 can receive the broadcast frame increases. Therefore, broadcast transmission can be appropriately performed in the communication network.

[0195] <Modification>

[0196] The synchronization among a plurality of terminals can be performed using a synchronization signal from a GPS (Global Position System) / GNSS (Global Navigation Satellite System) receiver that uses a satellite as a synchronization control unit.

[0197] In addition, in the above-mentioned embodiment, the functional unit of the CPU 201 may be appropriately integrated with other functional units, or may be divided into two or more sub-functional units.

[0198] In addition, in the above-mentioned embodiment, the process of the steps shown in the flowchart and the like is not limited to the process shown in the figure.

[0199] <Summary of implementation methods>

[0200] A relay communication device according to an embodiment of the present disclosure includes: a receiving unit for receiving a first signal broadcasted from a first communication device; a sending unit for broadcasting the first signal; and a synchronization control unit for synchronizing a timing of broadcasting the first signal by a second communication device that receives the first signal broadcasted from the first communication device with a timing of broadcasting the first signal by the sending unit.

[0201] In the present relay communication device, the sending unit unicasts a second signal to a main communication device of a communication system including the relay communication device, the first communication device, and the second communication device, wherein the second signal is a signal including information indicating broadcast transmission of the first signal, and the receiving unit receives the first signal converted from the second signal by the main communication device as a signal for broadcast transmission.

[0202] In the relay communication device, the synchronization control unit synchronizes the timing at which the second communication device broadcasts the first signal with the timing at which the transmission unit broadcasts the first signal within a period dedicated to broadcast transmission.

[0203] In the relay communication device, the number of hops from the first communication device to the relay communication device is the same as the number of hops from the first communication device to the second communication device.

[0204] In the relay communication device, the synchronization control unit synchronizes the timing at which the second communication device broadcasts and transmits the first signal with the timing at which the transmission unit broadcasts and transmits the first signal in accordance with IEEE1588.

[0205] In a communication method of one embodiment of the present disclosure, a relay communication device performs the following processing: receiving a first signal broadcasted from a first communication device; and broadcasting the first signal in a manner synchronized with the timing of broadcasting the first signal by a second communication device that receives the first signal broadcasted from the first communication device.

[0206] A communication system according to an embodiment of the present disclosure includes: a first communication device; a second communication device and a third communication device, which receive a signal broadcasted from the first communication device and broadcast the signal synchronously; and a fourth communication device, which receives the signal broadcasted synchronously by the second communication device and the third communication device.

[0207] In the above-mentioned embodiments, the expression “…part” used in each structural element may also be replaced by other expressions such as “…circuitry”, “…component”, “…device”, “…unit” or “…module”.

[0208] Although the embodiments are described above with reference to the accompanying drawings, the present disclosure is not limited to this example. As long as one is skilled in the art, it is obvious that various variations or modifications can be thought of within the scope of the claims. It should be understood that these variations or modifications also belong to the technical scope of the present disclosure. In addition, the various structural elements in the embodiments can be arbitrarily combined within the scope of the present disclosure.

[0209] The present disclosure can be implemented by software, hardware or software in cooperation with hardware. Each functional block used in the description of the above-mentioned embodiments is partially or entirely implemented as an LSI (Large Scale Integration) as an integrated circuit, and each process described in the above-mentioned embodiments may also be partially or entirely controlled by an LSI or a combination of LSIs. LSI may be composed of individual chips, or may be composed of one chip in a manner that includes part or all of the functional blocks. LSI may also include input and output of data. LSI may also be referred to as "IC (Integrated Circuit)", "System LSI", "Super LSI", "Ultra LSI" depending on the degree of integration.

[0210] The method of integrated circuitization is not limited to LSI, and can also be implemented by a dedicated circuit, a general-purpose processor or a dedicated processor. In addition, an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor (Reconfigurable Processor) that can reconfigure the connection or setting of the circuit block inside the LSI can also be used. The present disclosure can also be implemented as digital processing or analog processing.

[0211] Furthermore, if integrated circuit technology that replaces LSI emerges as semiconductor technology advances or other technologies are derived, it is of course possible to use this technology to achieve integration of functional blocks. There is also the possibility of applying biotechnology, etc.

[0212] The present disclosure can be implemented in all kinds of devices, equipment, and systems (collectively referred to as "communication devices") with communication functions. The communication device may also include a wireless transceiver and a processing / control circuit. The wireless transceiver may also include a receiving unit and a transmitting unit, or perform the functions of these parts. The wireless transceiver (transmitting unit, receiving unit) may also include an RF (Radio Frequency) module and one or more antennas. The RF module may also include an amplifier, an RF modulator / demodulator, or a device similar to these. Non-limiting examples of communication devices include: phones (mobile phones, smart phones, etc.), tablets, personal computers (PCs) (laptops, desktops, notebook computers, etc.), cameras (digital cameras, digital video cameras, etc.), digital players (digital audio / video players, etc.), wearable devices (wearable cameras, smart watches, tracking devices, etc.), game consoles, e-book readers, telehealth / telemedicine (telehealth / medical prescription) equipment, vehicles or transportation vehicles with communication functions (cars, airplanes, ships, etc.), and combinations of the above-mentioned various devices.

[0213] Communication devices are not limited to portable or mobile devices, but also include all kinds of devices, equipment, and systems that cannot be carried or fixed. For example, they include: smart home devices (home appliances, lighting equipment, smart meters or meters, control panels, etc.), vending machines, and all other "things" that can exist on the IoT (Internet of Things) network.

[0214] The communication includes data communication performed by a cellular system, a wireless LAN (Local Area Network) system, a communication satellite system, etc., and also includes data communication performed by a combination of these systems.

[0215] In addition, the communication device also includes devices such as controllers or sensors connected or linked to the communication device that performs the communication function described in the present invention. For example, it includes a controller or sensor that generates a control signal or data signal used by the communication device that performs the communication function of the communication device.

[0216] In addition, the communication device includes infrastructure equipment that communicates with the above-mentioned non-limiting various devices or controls the above-mentioned various devices, such as base stations, access points, and all other devices, equipment, and systems.

[0217] The disclosed contents of the specification, drawings, and abstract contained in the Japanese patent application No. 2022-158677 filed on September 30, 2022 are incorporated herein by reference in their entirety.

[0218] Industrial Applicability

[0219] One embodiment of the present disclosure is useful for a multi-hop communication system.

[0220] Description of Reference Numerals

[0221] 1. Communication System

[0222] 10 Main Terminal M

[0223] 20A~20E Relay terminals A~E

[0224] 20F terminal

[0225] 100 Terminal

[0226] 201CPU

[0227] 202 Storage device

[0228] 203 Communication devices

[0229] 204 Equipment interface device

[0230] 301 Group Analysis Department

[0231] 302 Authentication Processing Department

[0232] 303 Link Cost Calculation Department

[0233] 304 Topology Management Department

[0234] 305 Grouping Generation Unit

[0235] 306 Synchronous Control Unit

Claims

1. A relay communication device, characterized in that: include: A receiving unit, receiving a first signal broadcasted from a first communication device; A sending unit, configured to broadcast and send the first signal; as well as The synchronization control unit synchronizes a timing at which a second communication device that has received the first signal broadcast-transmitted from the first communication device broadcasts the first signal with a timing at which the transmission unit broadcasts the first signal.

2. The relay communication device according to claim 1, wherein: The transmitting unit unicasts a second signal to a main communication device in a communication system including the relay communication device, the first communication device, and the second communication device, the second signal being a signal including information indicating broadcast transmission of the first signal, The receiving unit receives the first signal converted from the second signal by the master communication device as a signal for broadcast transmission.

3. The relay communication device according to claim 1, wherein: The synchronization control unit synchronizes a timing at which the second communication device broadcasts and transmits the first signal with a timing at which the transmission unit broadcasts and transmits the first signal within a period dedicated to broadcast transmission.

4. The relay communication device according to claim 3, wherein: The number of hops from the first communication device to the relay communication device is the same as the number of hops from the first communication device to the second communication device.

5. The relay communication device according to claim 1, wherein: The synchronization control unit synchronizes a timing at which the second communication device broadcasts and transmits the first signal with a timing at which the transmission unit broadcasts and transmits the first signal in accordance with IEEE1588.

6. A communication method, characterized in that: The relay communication device performs the following processing: receiving a first signal broadcasted from a first communication device; and The first signal is broadcast-transmitted in synchronization with a timing at which the first signal is broadcast-transmitted by a second communication device that has received the first signal broadcast-transmitted from the first communication device.

7. A communication system, characterized in that: include: a first communication device; A second communication device and a third communication device receive the signal broadcasted from the first communication device and broadcast the signal synchronously; as well as The fourth communication device receives the signal broadcasted synchronously by the second communication device and the third communication device.

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