Wireless communication system, wireless communication device, wireless communication method, and wireless communication program

Abstract

To suppress unnecessary transfer.SOLUTION: A wireless communication system 1 includes a first node 10A that constitutes part of a wireless multi-hop mesh network 2 and performs flooding communication, and a GW node 10B that constitutes part of the wireless multi-hop mesh network 2 and is capable of communicating with an external network NW. The first node 10A includes a registration management unit and a communication management unit. The registration management unit registers, with management information, a setting TTL corresponding to the difference between a TTL initial value and a TTL included in an investigation packet in association with a GWID based on the investigation packet containing the GWID, TTL initial value, and TTL of the GW node 10B received from the GW node 10B. The communication management unit sets and transmits the setting TTL corresponding to the GWID in the management information as the TTL of a packet destined for the GW node 10B identified by the GWID.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system, a wireless communication device, a wireless communication method, and a wireless communication program. [Background technology]

[0002] Flooding communication is known as one of the technologies for realizing wireless multi-hop mesh networks. In flooding communication, each of the multiple nodes constituting a wireless multi-hop mesh network transmits packets to all other nodes within its communication range as forwarding destinations. Flooding communication enables robust communication. However, because flooding communication transmits packets to all surrounding nodes, including nodes that are significantly longer than the destination, excessive duplication of packets can cause network congestion.

[0003] One proposed congestion avoidance technique is to determine the number of packet forwardings per node based on the end-to-end communication success rate. However, this technique aims to ensure redundancy according to the packet loss rate, and is less effective in addressing the problem of packet forwarding via unnecessary routes. Another proposed method involves all nodes in the network periodically transmitting monitoring packets. This technique discloses that each node that receives a monitoring packet sets a TTL (Time To Live) for the source node in response to the monitoring packet. However, this technique involves all nodes in the network periodically transmitting monitoring packets, which can result in excessive forwarding of monitoring packets. In other words, conventional techniques can result in unnecessary packet forwarding when flooding communication is used in wireless multi-hop mesh networks. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7045451 [Patent Document 2] International Publication No. 2018 / 207411 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the embodiments of the present invention is to provide a wireless communication system, a wireless communication device, a wireless communication method, and a wireless communication program that can suppress unnecessary transfers. [Means for solving the problem]

[0006] According to an embodiment, a wireless communication system includes a first wireless communication device that configures a wireless multi-hop mesh network and performs flooding communication, and a second wireless communication device that configures the wireless multi-hop mesh network and is capable of communicating with an external network. The first wireless communication device includes a registration management unit and a communication management unit. Based on an investigation packet received from the second wireless communication device, the investigation packet includes second identification information of the second wireless communication device, an initial TTL value, and a TTL, the registration management unit registers a setting TTL corresponding to the difference between the initial TTL value and the TTL included in the investigation packet in management information, in association with the second identification information. The communication management unit sets the setting TTL corresponding to the second identification information in the management information as the TTL of a packet addressed to the second wireless communication device identified by the second identification information, and transmits the packet. When the destination information included in the inquiry packet is information indicating a broadcast, the registration management unit registers the setting TTL corresponding to the difference between the TTL initial value and the TTL included in the inquiry packet in the management information. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a wireless communication system. [Figure 2] Schematic diagram of the functional configuration of a GW node. [Figure 3] FIG. 10 is a schematic diagram showing the format of a probe packet. [Figure 4] FIG. 2 is a schematic diagram showing a packet format. [Figure 5] FIG. 10 is a schematic diagram showing the format of a probe packet. [Figure 6] Schematic diagram of the functional configuration of the first node. [Figure 7] FIG. 3 is a schematic diagram of the data structure of management information. [Figure 8] 10 is a flowchart showing the flow of information processing executed by the first node. [Figure 9] 10 is a flowchart showing the flow of information processing executed by the first node. [Figure 10] 10 is a flowchart showing the flow of information processing executed by a GW node. [Figure 11] 1 is a schematic diagram of a wireless communication system. [Figure 12] Schematic diagram of the functional configuration of a GW node. [Figure 13] FIG. 4 is a schematic diagram showing the data structure of an investigation packet. [Figure 14] Schematic diagram of the functional configuration of the first node. [Figure 15] FIG. 3 is a schematic diagram of the data structure of management information. [Figure 16] FIG. 3 is a schematic diagram of the data structure of schedule information. [Figure 17] Hardware configuration diagram. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a wireless communication system, a wireless communication device, a wireless communication method, and a wireless communication program according to the present embodiment will be described in detail with reference to the accompanying drawings.

[0009] In the following description of each embodiment, parts denoted by the same reference numerals have substantially the same functions, and descriptions of overlapping parts will be omitted where appropriate.

[0010] (First embodiment) FIG. 1 is a schematic diagram showing an example of a wireless communication system 1 according to the present embodiment.

[0011] The wireless communication system 1 includes a plurality of nodes 10 that communicate wirelessly, an external network NW, and a server device 20 connected to the external network NW. The server device 20 is an information processing device connected to the external network NW. The wireless communication system 1 may not include the server device 20.

[0012] The node 10 is an example of a wireless communication device. A plurality of nodes 10 constitute a wireless multi-hop mesh network 2. FIG. 1 shows 12 nodes 10 as an example of the nodes 10 constituting the wireless multi-hop mesh network 2. Note that the number of the plurality of nodes 10 constituting the wireless multi-hop mesh network 2 is not limited to 12.

[0013] Each of the multiple nodes 10 constituting the wireless multi-hop mesh network 2 has a function of performing flooding communication. The function of performing flooding communication is a function in which each of the multiple nodes 10 selects all other nodes 10 within its communication range as destinations or forwarding destinations when performing multi-hop communication, and transmits to those nodes.

[0014] In this embodiment, the explanation will be given assuming that all transmissions and forwardings by the node 10 are flooding communications. That is, transmissions and forwardings in the following explanation respectively represent transmissions by flooding communications and forwardings by flooding communications.

[0015] The wireless communication system 1 includes a first node 10A and a gateway (GW) node 10B as nodes 10. The first node 10A is an example of a first wireless communication device. The GW node 10B is an example of a second wireless communication device.

[0016] The first node 10A is a node 10 that configures the wireless multi-hop mesh network 2 and performs flooding communication. The first node 10A is also a node 10 that does not have a function of communicating with an external network NW.

[0017] In this embodiment, an example will be described in which the wireless multi-hop mesh network 2 includes nine first nodes 10A (first nodes 10A1 to 10A9). Note that the number of first nodes 10A constituting the wireless multi-hop mesh network 2 is not limited to nine as long as it is plural.

[0018] The GW node 10B is a node 10 that configures the wireless multi-hop mesh network 2 and performs flooding communication, similar to the first node 10A. The GW node 10B can further communicate with an external network NW and functions as a router connecting to the external network NW. Specifically, the GW node 10B functions as a gateway, a concentrator, or the like.

[0019] In this embodiment, a configuration will be described as an example in which the wireless multi-hop mesh network 2 includes three GW nodes 10B (GW node 10B1 to node 10B3). Note that the number of GW nodes 10B included in the wireless multi-hop mesh network 2 may be one or more and is not limited to three. In addition, in this embodiment, it is assumed that each of the multiple GW nodes 10B does not move within the wireless multi-hop mesh network 2 and is fixed at each position.

[0020] In this embodiment, a configuration in which Bluetooth (registered trademark) Mesh described in Non-Patent Document 1 is used as the standard specification of the wireless multi-hop mesh network 2 will be described as an example.

[0021] Non-patent document 1: Bluetooth Mesh Profile 1.0.1 https: / / www.bluetooth.com / ja-jp / specifications / specs / mesh-profile-1-0-1 /

[0022] In Bluetooth Mesh, packets transmitted or forwarded within the wireless multi-hop mesh network 2 contain a TTL (Time To Live) that indicates the number of times the packet can be forwarded. When a node 10 receives a packet, if the TTL is "1" or greater, it decrements the packet by "1" and forwards it to another node 10, but if the TTL is "0", it discards the packet without forwarding it.

[0023] In this embodiment, each of the multiple first nodes 10A constituting the wireless multi-hop mesh network 2 transmits packets mainly addressed to the GW node 10B.

[0024] Each of the multiple first nodes 10A transmits a packet when data to be transmitted originating from the node itself occurs. Furthermore, each of the multiple first nodes 10A forwards a packet when it receives a packet from another first node 10A that is not addressed to the node itself. Packets transmitted or forwarded from each first node 10A are received by all other nodes 10 within the communication range of the first node 10A through flooding communication. When forwarding a packet, each node 10 checks the TTL included in the packet and executes the forwarding process described above.

[0025] Next, the functional configuration of the GW node 10B of this embodiment will be described.

[0026] FIG. 2 is a schematic diagram of an example of the functional configuration of the GW node 10B.

[0027] The GW node 10B includes a storage unit 40, a communication unit 42, a NW (network) communication unit 44, and a control unit 48. The storage unit 40, the communication unit 42, the NW communication unit 44, and the control unit 48 are connected to each other so as to be able to communicate with each other via a bus 46 or the like.

[0028] The storage unit 40 stores various types of data. The communication unit 42 is a functional unit for transmitting and receiving packets to and from other nodes 10 within the wireless multi-hop mesh network 2. The NW communication unit 44 is a functional unit for transmitting and receiving data to and from the server device 20 via the external network NW.

[0029] The control unit 48 includes a communication control unit 48A. The communication control unit 48A is realized, for example, by one or more processors. For example, each unit included in the control unit 48 may be realized by having a processor such as a CPU (Central Processing Unit) execute a program, that is, by software. Each of the above units may be realized by a processor such as a dedicated IC, that is, by hardware. Each of the above units may be realized by a combination of software and hardware. When multiple processors are used, each processor may realize one of the units, or may realize two or more of the units.

[0030] The communication control unit 48A controls transmission of the probe packet to the first node 10A included in the wireless multi-hop mesh network 2.

[0031] The probe packet is a packet transmitted from the GW node 10B to the first node 10A constituting the wireless multi-hop mesh network 2.

[0032] The communication control unit 48A broadcasts an investigation packet containing information indicating a broadcast as destination information at predetermined time intervals.

[0033] 3 is a schematic diagram showing an example of the format of an investigation packet to be broadcast. The investigation packet includes origin information, destination information, TTL, and data. The origin information is information that indicates the origin of transmission of the investigation packet. The investigation packet is a packet transmitted from the GW node 10B. Therefore, the origin information of the investigation packet is set with a GWID, which is identification information of the GW node 10B that transmits the investigation packet. The GWID is an example of second identification information.

[0034] The destination information is information that indicates the destination of the investigation packet. Specifically, the destination information is set with information that indicates a broadcast, or information that indicates a unicast that indicates a specific node 10 and identification information of the specific node 10. The destination information included in the investigation packet that the communication control unit 48A broadcasts at predetermined time intervals is set with information that indicates a broadcast.

[0035] As described above, the TTL is a value that indicates the number of times a message can be transferred. That is, the TTL is a value that is subject to change by subtracting "1" from the value each time the message is transferred by each of the first nodes 10A.

[0036] The data field included in the probe packet includes a TTL initial value. The TTL initial value is an initial value of the TTL. The TTL initial value may be any value that allows the probe packet to be forwarded to each of all first nodes 10A constituting the wireless multi-hop mesh network 2.

[0037] Returning to Fig. 2, the explanation will be continued. The communication control unit 48A broadcasts an investigation packet shown in Fig. 3 at predetermined time intervals. That is, the GW node 10B sets the GWID of its own node as the origin information, sets information indicating broadcast as the destination information, and broadcasts an investigation packet in which the TTL and TTL initial value are set at predetermined time intervals.

[0038] This predetermined time may be determined in advance depending on the configuration of the wireless multi-hop mesh network 2. Furthermore, this predetermined time may be changeable as needed by an operation instruction from the user.

[0039] The communication control unit 48A executes the following process when it receives a packet from the first node 10A included in the wireless multi-hop mesh network 2. In detail, the communication control unit 48A determines whether the TTL included in the packet received from the first node 10A is equal to or greater than a second threshold. If the TTL is equal to or greater than the second threshold, the communication control unit 48A unicasts to the first node 10A an investigation packet that includes the TTL as a TTL correction value and that includes, as destination information, information indicating the first node 10A as the sender of the packet and unicast.

[0040] FIG. 4 is a schematic diagram showing an example of a packet format. The packet includes origin information, destination information, TTL, and data. The origin information is information indicating the origin of packet transmission. The destination information is information indicating the destination of the packet. As described above, in this embodiment, each of the first nodes 10A included in the wireless multi-hop mesh network 2 transmits packets mainly addressed to the GW node 10B. For this reason, the origin information included in the packet is set to identification information of the first node 10A. Furthermore, the destination information included in the packet is set to the GWID of any of the GW nodes 10B included in the wireless multi-hop mesh network 2. The TTL is the same as above.

[0041] Continuing the explanation, returning to Fig. 2, the communication control unit 48A determines whether or not the TTL included in the packet received from the first node 10A is equal to or greater than the second threshold value.

[0042] The second threshold may be set as a threshold used to determine whether or not the value of the setting TTL for the GW node 10B needs to be changed. Details of the setting TTL will be described later. For example, the communication control unit 48A may set the second threshold in advance according to the network topology of the wireless multi-hop mesh network 2, the communication success rate of the wireless multi-hop mesh network 2, the ease of connection of the wireless multi-hop mesh network 2, and the like. In detail, the communication control unit 48A may set a larger second threshold in advance as the communication success rate is higher or the connection is easier. In other words, the communication control unit 48A can make it easier to change the value of the setting TTL on the first node 10A side by setting a smaller second threshold as the connection is more difficult or the communication success rate is lower.

[0043] If the TTL included in a packet received from the first node 10A is equal to or greater than the second threshold, the communication control unit 48A sets the TTL included in the packet as a TTL correction value and generates an investigation packet including the TTL correction value in its data field. The communication control unit 48A also sets, as destination information for the investigation packet, the identification information of the first node 10A indicated in the packet's origin information and information indicating unicast. The generated and set investigation packet is then unicast to the first node 10A.

[0044] 5 is a schematic diagram showing an example of the format of an investigation packet to be unicast. The investigation packet unicast by the communication control unit 48A of the GW node 10B to the first node 10A has a TTL correction value set in the data field of the investigation packet described in FIG.

[0045] In this way, the communication control unit 48A of the GW node 10B broadcasts an investigation packet that includes information indicating broadcast as destination information and includes a TTL initial value in the data field at predetermined time intervals. Also, the communication control unit 48A unicasts an investigation packet that further sets a TTL correction value in the data field to the first node 10A that is the sender of the packet including a TTL equal to or greater than the second threshold.

[0046] Next, an example of the functional configuration of the first node 10A of this embodiment will be described.

[0047] FIG. 6 is a schematic diagram of an example of the functional configuration of the first node 10A.

[0048] The first node 10A includes a storage unit 30, a communication unit 32, and a control unit 38. The storage unit 30, the communication unit 32, and the control unit 38 are communicatively connected via a bus 36 or the like.

[0049] The storage unit 30 stores various types of data. In this embodiment, the storage unit 30 stores management information 30A. The management information 30A is updated by a control unit 38, which will be described later. The data structure of the management information 30A will be described in detail later.

[0050] The communication unit 32 is a functional unit for transmitting and receiving packets to and from other nodes 10 in the wireless multi-hop mesh network 2.

[0051] The control unit 38 includes a registration management unit 38A and a communication management unit 38B. The registration management unit 38A and the communication management unit 38B are realized, for example, by one or more processors. For example, each of the above units may be realized by having a processor such as a CPU execute a program, i.e., by software. Each of the above units may be realized by a processor such as a dedicated IC, i.e., by hardware. Each of the above units may be realized by a combination of software and hardware. When multiple processors are used, each processor may realize one of the units, or may realize two or more of the units.

[0052] Based on the investigation packet received from the GW node 10B, the registration management unit 38A registers a setting TTL corresponding to the difference between the TTL and the initial TTL value included in the investigation packet in the management information 30A in association with the GWID, which is the second identification information of the GW node 10B.

[0053] In detail, when the destination information included in the investigation packet is information indicating a broadcast, the registration management unit 38A performs the following process. As described above, the GW node 10B broadcasts an investigation packet including origin information, destination information, TTL, and an initial TTL value included in the data field at predetermined time intervals (see FIG. 3). In this case, the registration management unit 38A registers a setting TTL corresponding to the difference between the initial TTL value included in the investigation packet and the TTL in the management information 30A.

[0054] 7 is a schematic diagram of an example of the data configuration of the management information 30A. The management information 30A is information in which a GWID, which is second identification information of the GW node 10B, a setting TTL, and a TTL initial value are associated with each other. Note that one setting TTL and one TTL initial value are registered in association with one GWID in the management information 30A.

[0055] In this embodiment, the registration management unit 38A calculates the difference between the initial TTL value included in the investigation packet and the TTL included in the investigation packet as the setting TTL. Specifically, the registration management unit 38A calculates the setting TTL by subtracting the TTL included in the investigation packet from the initial TTL value included in the investigation packet.

[0056] Then, the registration management unit 38A associates the calculated setting TTL with the GWID and TTL initial value included in the investigation packet used to calculate the setting TTL, and registers them in the management information 30A.

[0057] The registration management unit 38A calculates a setting TTL and registers it in the management information 30A every time an investigation packet is received from each of the plurality of GW nodes 10B included in the wireless multi-hop mesh network 2. For this reason, the registration management unit 38A registers the setting TTL and the TTL initial value for each of the plurality of GW nodes 10B included in the wireless multi-hop mesh network 2.

[0058] The first node 10A receives a plurality of probe packets from one GW node 10B via a plurality of routes that pass through one or a plurality of different first nodes 10A. That is, the probe packets broadcast from one GW node 10B reach the first node 10A via various routes in the wireless multi-hop mesh network 2.

[0059] Therefore, it is preferable that the registration management unit 38A calculates the difference between the maximum value of the TTLs contained in multiple investigation packets received from one GW node 10B and the initial TTL value contained in the investigation packet as the setting TTL.

[0060] Specifically, the registration management unit 38A calculates the setting TTL using the following formula (1).

[0061] TTLm=Ti-maxTm Equation (1)

[0062] In formula (1), TTLm is the TTL to be set for the GW node 10B having a GWID of "m". Ti is the TTL initial value included in the investigation packet received from the GW node 10B having a GWID of "m". Tm is a set of TTLs included in the investigation packet received from the GW node 10B having a GWID of "m". maxTm is the maximum TTL among the set of TTLs included in the investigation packet received from the GW node 10B having a GWID of "m".

[0063] The registration management unit 38A calculates the difference between the maximum value of the TTLs contained in multiple investigation packets received from the same GW node 10B and the initial TTL value contained in the investigation packet as the setting TTL, and thereby the setting TTL can be calculated using the maximum TTL, i.e., the TTL contained in the investigation packet received via the shortest route from the GW node 10B.

[0064] Furthermore, if the destination information included in the investigation packet is information that indicates a unicast and the first node 10A, the registration management unit 38A performs the following process: In this case, the registration management unit 38A registers a value obtained by subtracting the TTL correction value included in the investigation packet from the setting TTL corresponding to the GWID included in the investigation packet in the management information 30A as a new setting TTL in association with the GWID in the management information 30A.

[0065] As described above, if the TTL included in the packet received from the first node 10A is equal to or greater than the second threshold, the GW node 10B unicasts an investigation packet including the TTL as a TTL correction value to the first node 10A (see FIG. 5).

[0066] When the destination information included in the investigation packet received from the GW node 10B is unicast and information representing the first node 10A, the registration management unit 38A identifies the TTL correction value included in the data field of the investigation packet. The registration management unit 38A also identifies the GWID of the GW node 10B that is the sender of the investigation packet. The registration management unit 38A identifies the GWID of the GW node 10B that is the sender of the investigation packet by reading the origin information included in the investigation packet.

[0067] The registration management unit 38A then reads the setting TTL corresponding to the identified GWID in the management information 30A. The registration management unit 38A registers the value obtained by subtracting the identified TTL correction value from the read setting TTL as a new setting TTL in association with the GWID in the management information 30A.

[0068] Therefore, when the investigation packet includes a TTL correction value, the registration management unit 38A can update the setting TTL corresponding to the GWID of the GW node 10B that is the transmission source of the investigation packet.

[0069] Furthermore, if the destination information included in the investigation packet is information indicating a unicast and another first node 10A, the registration management unit 38A executes the following process. In this case, the registration management unit 38A determines whether the difference between the TTL initial value included in another investigation packet previously received from the GW node 10B and the TTL included in the investigation packet received this time is equal to or greater than a first threshold. If the difference is equal to or greater than the first threshold, the registration management unit 38A associates the difference with the GWID as a setting TTL and registers it in the management information 30A.

[0070] In detail, when the destination information included in the investigation packet received from the GW node 10B is information indicating a unicast and another first node 10A, the registration management unit 38A identifies the TTL included in the investigation packet. The registration management unit 38A also identifies the GWID of the GW node 10B that is the sender of the investigation packet. The registration management unit 38A identifies the GWID of the GW node 10B that is the sender of the investigation packet by reading the origin information included in the investigation packet.

[0071] Then, the registration management unit 38A reads the TTL initial value corresponding to the identified GWID in the management information 30 A. Through this process, the registration management unit 38A reads the TTL initial value included in the investigation packet previously received from the GW node 10B identified by the identified GWID.

[0072] Then, the registration management unit 38A determines whether the difference, which is the difference obtained by subtracting the TTL included in the currently received investigation packet from the previously received TTL initial value, is equal to or greater than the first threshold value.

[0073] The first threshold may be set as a threshold used in determining whether or not the value of the setting TTL for the GW node 10B needs to be changed in the first node 10A. For example, the registration management unit 38A may set the first threshold in advance according to the network topology of the wireless multi-hop mesh network 2, the communication success rate of the wireless multi-hop mesh network 2, the ease of connection to the wireless multi-hop mesh network 2, etc. In detail, the registration management unit 38A may set a larger first threshold in advance as the ease of connection increases or the communication success rate increases. In other words, the registration management unit 38A can make it easier to change the value of the setting TTL by setting a smaller first threshold as the difficulty of connection increases or the communication success rate decreases.

[0074] If the difference, which is the difference obtained by subtracting the TTL included in the currently received investigation packet from the previously received TTL initial value, is equal to or greater than a first threshold, the registration management unit 38A registers the difference as the setting TTL corresponding to the GWID in the management information 30A. Furthermore, if the difference is less than the first threshold, the registration management unit 38A does not update the setting TTL in the management information 30A.

[0075] Therefore, when the investigation packet includes a TTL correction value, the registration management unit 38A can update the setting TTL corresponding to the GWID of the GW node 10B that is the transmission source of the investigation packet.

[0076] Next, the communication management unit 38B will be described.

[0077] The communication management unit 38B sets the setting TTL corresponding to the GWID of the GW node 10B in the management information 30A as the TTL of a packet destined for the GW node 10B, and transmits the packet. In detail, when transmitting a packet originating from the first node 10A, i.e., the communication management unit 38B's own node, to the GW node 10B, the communication management unit 38B transmits a packet in which the setting TTL corresponding to the GWID of the GW node 10B in the management information 30A is set as the TTL.

[0078] In detail, the communication management unit 38B sets the setting TTL corresponding to the GWID of the GW node 10B to which the packet is to be sent in the management information 30A as the TTL of the packet. Furthermore, the communication management unit 38B sets the GWID of the GW node 10B as the destination information of the packet, and sets the identification information of the first node 10A as the origin information. Then, the communication management unit 38B transmits the packet with these settings.

[0079] In the management information 30A, the registration management unit 38A registers an optimal setting TTL for each GW node 10B. Therefore, the communication management unit 38B sets the setting TTL corresponding to the GWID of the GW node 10B to be transmitted in the management information 30A as the TTL of a packet addressed to the GW node 10B, and transmits the packet, thereby enabling flooding communication of a packet with a TTL set that can suppress unnecessary forwarding, addressed to the GW node 10B.

[0080] Furthermore, when the communication management unit 38B forwards a packet received from another first node 10A to the GW node 10B, if the TTL included in the packet is less than the setting TTL corresponding to the GWID representing the destination included in the packet or is "0", the communication management unit 38B discards the received packet as not to be forwarded.

[0081] That is, the communication management unit 38B discards packets that have a TTL of "0" when they reach the node itself, among packets that are flooded from another first node 10A with the GW node 10B as their destination, as packets that are not to be forwarded. That is, in the wireless communication system 1 of this embodiment, the TTL of packets that take a detour to reach the GW node 10B becomes "0" before they reach the GW node 10B. Therefore, the communication management unit 38B can suppress unnecessary forwarding.

[0082] Furthermore, the communication management unit 38B discards packets whose TTL satisfies the above conditions without forwarding them, thereby suppressing excessive duplication of packets due to forwarding and suppressing congestion.

[0083] In addition, the communication management unit 38B discards packets that are flooded from other first nodes 10A to the GW node 10B and whose TTL is less than the setting TTL corresponding to the GWID of the GW node 10B when they reach the node itself, as packets that are not to be forwarded.

[0084] For this reason, the communication management unit 38B can discard, without forwarding, packets whose TTL, which is the number of times a packet can be forwarded, is less than the setting TTL, among packets to be forwarded to the GW node 10B via its own node, thereby suppressing unnecessary forwarding. In other words, the communication management unit 38B can discard, without forwarding, packets that it determines cannot reach the GW node 10B. Furthermore, the communication management unit 38B can suppress forwarding of packets to routes heading in a direction different from the direction heading to the destination GW node 10B. For this reason, the communication management unit 38B can suppress unnecessary forwarding.

[0085] Furthermore, the communication management unit 38B discards packets whose TTL satisfies the above conditions without forwarding them, thereby suppressing excessive duplication of packets due to forwarding and suppressing congestion.

[0086] Next, an example of the flow of information processing executed by the first node 10A of this embodiment will be described.

[0087] FIG. 8 is a flowchart showing an example of the flow of information processing executed by the first node 10A when an investigation packet is received.

[0088] The registration management unit 38A of the first node 10A determines whether or not an investigation packet has been received (step S100). For example, the registration management unit 38A determines whether or not an investigation packet has been received by determining whether or not the starting point information of the received investigation packet is a GWID.

[0089] If the determination in step S100 is negative (step S100: No), this routine ends. If the determination in step S100 is positive (step S100: Yes), the process proceeds to step S102.

[0090] In step S102, the registration management unit 38A determines whether the destination information included in the investigation packet received in step S100 is information indicating a broadcast (step S102). If it is determined that the destination information is information indicating a broadcast (step S102: Yes), the process proceeds to step S104.

[0091] In step S104, the registration management unit 38A sets the difference between the TTL and the initial TTL value included in the investigation packet received in step S100 as the setting TTL, and registers it in the management information 30A in association with the GWID, which is the origin information included in the investigation packet (step S104).

[0092] Next, the registration management unit 38A determines whether the TTL included in the investigation packet received in step S100 is "0" (step S106). If it is determined that the TTL is "0" (step S106: Yes), the registration management unit 38A discards the investigation packet received in step S100 (step 108). Then, this routine ends.

[0093] If it is determined that the TTL is a value greater than 0 (step S106: No), the process proceeds to step S110. In step S110, the communication management unit 38B subtracts "1" from the TTL included in the investigation packet received in step S100 (step S110). Then, the communication management unit 38B transfers the investigation packet with the TTL subtracted by "1" in step S110 to another first node 10A (step S112). Then, this routine ends.

[0094] On the other hand, if it is determined in step S102 that the destination is a unicast (step S102: No), the process proceeds to step S114. In step S114, the registration management unit 38A determines whether or not the destination information included in the investigation packet received in step S100 is information that represents the node itself (step S114). The registration management unit 38A makes the determination in step S114 by determining whether or not the destination information included in the investigation packet received in step S100 is information that represents a unicast and the identification information of the first node 10A.

[0095] If it is determined in step S114 that the destination information is information representing the node itself (step S114: Yes), the process proceeds to step S116. In step S116, the registration management unit 38A registers a value obtained by subtracting the TTL correction value included in the investigation packet received in step S100 from the setting TTL corresponding to the GWID included in the investigation packet in the management information 30A as a new setting TTL in association with the GWID in the management information 30A (step S116). Then, this routine ends.

[0096] If it is determined in step S114 that the destination information is information representing another first node 10A (step S114: No), the process proceeds to step S118. In step S118, the registration management unit 38A reads, from the management information 30A, the TTL initial value included in the investigation packet previously received from the GW node 10B that is the source of the investigation packet received in step S100. Then, the registration management unit 38A calculates a difference by subtracting the TTL included in the investigation packet received in step S100 from the read TTL initial value (step S118).

[0097] Next, the registration management unit 38A determines whether the difference calculated in step S118 is equal to or greater than the first threshold (step S120). If the registration management unit 38A determines that the difference is equal to or greater than the first threshold (step S120: Yes), the process proceeds to step S122. Then, the registration management unit 38A registers the difference calculated in step S118 in the management information 30A as a setting TTL corresponding to the GWID of the GW node 10B that is the source of the investigation packet received in step S100 (step S122). Then, the process proceeds to step S106. On the other hand, if the determination in step S120 is negative (step S120: No), the routine ends.

[0098] Next, an example of the flow of information processing that the first node 10A executes when transmitting or transferring a packet will be described.

[0099] FIG. 9 is a flowchart showing an example of the flow of information processing executed by the first node 10A when transmitting or forwarding a packet.

[0100] The communication management unit 38B determines whether to transmit a packet originating from its own node (step S200). For example, the communication management unit 38B makes the determination in step S200 by determining whether a predetermined transmission condition for transmitting a detection result of a sensor or the like connected to the first node 10A is satisfied.

[0101] If it is determined that a packet originating from the own node is to be transmitted (step S200: Yes), the process proceeds to step S202. In step S202, the communication management unit 38B identifies the setting TTL corresponding to the GWID of the GW node 10B to which the packet is to be transmitted in the management information 30A (step S202). Then, the communication management unit 38B sets the setting TTL identified in step S202 as the TTL of the packet (step S204). Then, the communication management unit 38B further sets the GWID of the GW node 10B as the destination information of the packet, and transmits the packet in which the identification information of the first node 10A is set as the origin information (step S206). Then, this routine ends.

[0102] If the determination in step S200 is negative (step S200: No), the process proceeds to step S208. In step S208, the communication management unit 38B determines whether or not a packet has been received from another first node 10A (step S208). If the determination in step S208 is negative (step S208: No), this routine ends.

[0103] If the determination in step S208 is affirmative (step S208: Yes), the process proceeds to step S210. As described above, in this embodiment, an example will be described in which the first node 10A constituting the wireless multi-hop mesh network 2 transmits a packet addressed to the GW node 10B. Therefore, a case in which the determination in step S208 is affirmative means a situation in which the communication management unit 38B receives a packet addressed to the GW node 10B from another first node 10A.

[0104] In step S210, the communication management unit 38B determines whether the TTL included in the packet received in step S208 is "0" (step S210). If it is determined that the TTL is "0" (step S210: Yes), the process proceeds to step S212. The communication management unit 38B discards the packet received in step S208 (step S212) and ends this routine.

[0105] If it is determined that the TTL is a value greater than 0 (step S210: No), the process proceeds to step S213. In step S213, the communication management unit 38B identifies the setting TTL corresponding to the GWID indicating the destination included in the packet received in step S208 from the management information 30A (step S214). Then, the communication management unit 38B determines whether the TTL included in the packet received in step S208 is less than the setting TTL identified in step S214 (step S216). If the communication management unit 38B determines that the TTL is less than the setting TTL (step S216: Yes), the process proceeds to step S212.

[0106] If the communication management unit 38B determines that the TTL is less than the setting TTL (step S216: No), the process proceeds to step S218. The communication management unit 38B subtracts "1" from the TTL included in the packet received in step S208 (step S218). Then, the communication management unit 38B transfers the packet with the TTL subtracted by "1" in step S218 (step S220). Then, this routine ends.

[0107] Next, an example of the flow of information processing executed by the GW node 10B will be described.

[0108] FIG. 10 is a flowchart showing an example of the flow of information processing executed by the GW node 10B.

[0109] The communication control unit 48A of the GW node 10B determines whether a predetermined time has elapsed (step S300). The communication control unit 48A makes the determination in step S300 by determining whether the elapsed time from the timing of the previous transmission of an investigation packet including information indicating a broadcast as destination information is equal to or greater than a predetermined time.

[0110] If communication control unit 48A determines that the predetermined time has elapsed (step S300: Yes), the process proceeds to step S302. In step S302, communication control unit 48A sets the GWID of its own node as the source information, sets information indicating broadcast as the destination information, and broadcasts an investigation packet in which the TTL and TTL initial value are set (step S302). Then, this routine ends.

[0111] If the communication control unit 48A makes a negative determination in step S300 (step S300: No), the process proceeds to step S304. The communication control unit 48A determines whether or not a packet has been received from the first node 10A (step S304). If the communication control unit 48A makes a negative determination in step S304 (step S304: No), the process ends this routine. If the communication control unit 48A makes a positive determination in step S304 (step S304: Yes), the process proceeds to step S306.

[0112] In step S306, communication control unit 48A determines whether the TTL included in the packet received in step S304 is equal to or greater than the second threshold (step S306). If the determination in step S306 is negative (step S306: No), this routine ends. If the determination in step S306 is positive (step S306: Yes), the routine proceeds to step S308.

[0113] In step S308, the communication control unit 48A sets the TTL included in the packet received in step S304 as a TTL correction value, and generates an investigation packet including the TTL correction value in a data field (step S308). Then, the communication control unit 48A sets the identification information of the first node 10A indicated in the origin information of the packet received in step S304 and information indicating unicast as destination information of the investigation packet generated in step S308 (step S310).

[0114] Then, the communication control unit 48A unicasts the investigation packet generated and set in steps S308 and S310 to the first node 10A, which is the origin of the packet received in step S304 (step S312), and then ends this routine.

[0115] As described above, the wireless communication system 1 of this embodiment includes a first node 10A (first wireless communication device) that constitutes a wireless multi-hop mesh network 2 and performs flooding communication, and a GW node 10B (second wireless communication device) that constitutes the wireless multi-hop mesh network 2 and is capable of communicating with an external network NW.

[0116] The first node 10A includes a registration management unit 38A and a communication management unit 38B. Based on an investigation packet received from the GW node 10B, which includes the GWID (second identification information) of the GW node 10B, an initial TTL value, and a TTL, the registration management unit 38A registers a setting TTL corresponding to the difference between the initial TTL value included in the investigation packet and the TTL in the management information 30A in association with the GWID. The communication management unit 38B sets the setting TTL corresponding to the GWID in the management information 30A as the TTL of a packet addressed to the GW node 10B identified by the GWID, and transmits the packet.

[0117] Here, when flooding communication is performed in the wireless multi-hop mesh network 2, it has been difficult to suppress unnecessary forwarding with conventional techniques.

[0118] As described above, in flooding communication, when multiple nodes 10 perform multi-hop communication, each node 10 selects all other nodes 10 within its communication range as the transmission or forwarding destination and transmits to them. This makes it possible to perform multi-hop communication with high reliability. Furthermore, flooding communication performs packet communication using essentially all multi-hop communication paths simultaneously. Because flooding communication does not select a specific multi-hop communication path, it has the advantage of simpler network management than other mesh network technologies and can continue communication without major disruption even if communication is interrupted between some nodes 10.

[0119] In flooding communication, when each node 10 included in the wireless multi-hop mesh network 2 receives a packet addressed to a destination other than the node itself, the node 10 broadcasts the packet to other surrounding nodes 10. This allows for robust communication.

[0120] However, in flooding communication, each of the multiple nodes 10 constituting the wireless multi-hop mesh network 2 has all other nodes 10 within its communication range as its forwarding destinations. For this reason, in flooding communication, packets may be sent to nodes 10 that are clearly taking a long detour to reach the destination, and further forwarding by the destination nodes 10 may result in excessive duplication of packets, which may cause congestion in the network.

[0121] For example, consider the wireless multi-hop mesh network 2 shown in FIG. 1. Also, consider a situation in which the first node 10A1 transmits a packet addressed to the GW node 10B1. When the first node 10A1 floods the packet, the other first nodes 10A that receive the packet further forward the received packet to other surrounding first nodes 10A by flooding. In this case, the shortest route for the packet is the two-hop route from the first node 10A1 to the GW node 10B1 via the first node 10A3. However, in flooding, the packet is forwarded to all surrounding other nodes 10, so forwarding may also be performed via an excessively long route that passes through each of the first node 10A2, the first node 10A4 to the first node 10A9, etc.

[0122] Although a somewhat circuitous route may be worth maintaining from the perspective of redundancy, an excessively circuitous route increases the number of times packets are replicated, increasing the risk of congestion and transmission delays. Congestion risks and transmission delays may also have a negative impact on applications.

[0123] Patent Document 1 proposes a method for determining the number of times each relay node forwards a packet based on the end-to-end communication success rate. In a mesh network, flooding forwarding is performed over various routes. Therefore, a relay node may forward the same data transmission multiple times. Patent Document 1 discloses specifying the number of times for such forwarding. Specifically, Patent Document 1 calculates the ratio of data packets and acknowledgment packets forwarded by the node itself when forwarding a pair of transmitted and received packets that has multiple relay nodes. Patent Document 1 then determines that a high ratio indicates high reliability of the communication route and reduces the number of data forwardings. Patent Document 1 also determines that a low ratio indicates a high possibility of packet loss and increases the number of data forwardings. However, the method of Patent Document 1 aims to ensure redundancy according to the packet loss rate, and is not very effective in addressing the problem of packet forwarding over unnecessary routes.

[0124] Patent Document 2 proposes a method for suppressing multi-hop forwarding by setting an appropriate value as the TTL. In Patent Document 2, each node periodically transmits a monitoring packet storing an initial TTL value to surrounding nodes. A node that receives a monitoring packet sets the difference between the initial TTL value and the TTL at the time of reception as the TTL to be set in a packet to be transmitted to the node that sent the monitoring packet. However, in Patent Document 2, because each of all nodes that make up the network periodically transmits a monitoring packet, the more nodes in the network increase, the more monitoring packets there are likely to be inundated in the network, causing congestion.

[0125] As described above, in the prior art, when flooding communication is used in the wireless multi-hop mesh network 2, unnecessary packet transfers may occur.

[0126] On the other hand, in the wireless communication system 1 of this embodiment, the registration management unit 38A of the first node 10A performing flooding communication associates a setting TTL corresponding to the difference between the TTL and the TTL initial value included in the investigation packet received from the GW node 10B with the GWID and registers it in the management information 30A. Therefore, in the management information 30A, for each GW node 10B identified by the GWID, a setting TTL indicating the TTL when the first node 10A that stored the management information 30A reaches the GW node 10B via the shortest path or a path close to the shortest path is registered.

[0127] The communication management unit 38B sets the setting TTL corresponding to the GWID in the management information 30A as the TTL of the packet addressed to the GW node 10B identified by the GWID, and transmits the packet.

[0128] In this way, in the wireless communication system 1 of this embodiment, the GW node 10B sets the setting TTL corresponding to the difference between the TTL and the TTL initial value included in the investigation packet received from the GW node 10B as the TTL of the packet addressed to the GW node 10B, which is the sender of the investigation packet.

[0129] For this reason, the TTL included in packets that are flooded from the first node 10A to the GW node 10B as their destination is a value adjusted to an appropriate value for each destination GW node 10B. In other words, the TTL included in packets that are flooded from the first node 10A to the GW node 10B as their destination is the TTL when the packets arrive at the destination GW node 10B via the shortest path or a path close to the shortest path. For this reason, the TTL included in packets transmitted from each first node 10A is prevented from becoming too large, and it is possible to prevent unnecessary packet forwarding.

[0130] Therefore, the wireless communication system 1 of this embodiment can suppress unnecessary transfers.

[0131] Furthermore, in the wireless communication system 1 of this embodiment, the GW node 10B transmits an investigation packet. Therefore, the wireless communication system 1 of this embodiment can reduce the risk of congestion and interference in the wireless multi-hop mesh network 2 compared to when all the nodes 10 transmit investigation packets.

[0132] Furthermore, the wireless communication system 1 of this embodiment can suppress the occurrence of unnecessary packet transfers, thereby reducing the power consumption required for transmission and transfer.

[0133] (Second embodiment) In the above embodiment, it has been assumed that each of the plurality of GW nodes 10B included in the wireless multi-hop mesh network 2 does not move but is fixed at each position within the wireless multi-hop mesh network 2.

[0134] In this embodiment, a form in which the GW node 10B included in the wireless multi-hop mesh network 2 is configured to be able to move its position in the wireless multi-hop mesh network 2 will be described as an example.

[0135] FIG. 11 is a schematic diagram showing an example of a wireless communication system 1B of this embodiment.

[0136] The wireless communication system 1B includes a plurality of nodes 10 that communicate wirelessly, an external network NW, and a server device 20 connected to the external network NW. The nodes 10 and the server device 20 are the same as those in the above embodiment. That is, the nodes 10 configure a wireless multi-hop mesh network 2 and perform flooding communication. In this embodiment, as in the above embodiment, a form will be described as an example in which Bluetooth Mesh, which is described in Non-Patent Document 1, is used as the standard specification for the wireless multi-hop mesh network 2.

[0137] In this embodiment, a configuration will be described in which, as the node 10, a first node 10C is provided instead of the first node 10A, and a GW node 10D is provided instead of the GW node 10B.

[0138] The first node 10C, like the first node 10A, is a node 10 that configures the wireless multi-hop mesh network 2 and performs flooding communication. In this embodiment, the first node 10C transmits packets addressed to the GW node 10D instead of the GW node 10B.

[0139] The GW node 10D, like the GW node 10B, configures a wireless multi-hop mesh network 2 and performs flooding communication. The GW node 10D can also be connected to an external network NW.

[0140] In this embodiment, the GW node 10D is provided so as to be movable among positions in the wireless multi-hop mesh network 2. For example, as shown in Fig. 11 , the GW node 10D is provided so as to be movable among positions A, B, and C in the wireless multi-hop mesh network 2.

[0141] The position in the wireless multi-hop mesh network 2 is represented by, for example, information indicating which of the multiple first nodes 10C included in the wireless multi-hop mesh network 2 the node is connected to with a hop count of 1.

[0142] FIG. 12 is a schematic diagram of an example of the functional configuration of the GW node 10D.

[0143] The GW node 10D includes a storage unit 40, a communication unit 42, a NW communication unit 44, and a control unit 49. The GW node 10D is similar to the GW node 10B of the above embodiment except that it includes a control unit 49 instead of the control unit 48.

[0144] The control unit 49 includes a communication control unit 49A. The control unit 49 is similar to the control unit 48 of the above embodiment, except that the control unit 49 includes the communication control unit 49A instead of the communication control unit 48A.

[0145] Similar to the communication control unit 48A in the above embodiment, the communication control unit 49A controls the transmission of an investigation packet to the first node 10A included in the wireless multi-hop mesh network 2. However, the communication control unit 49A transmits an investigation packet that further includes transmission point information of the GW node 10D at the time of transmission of the investigation packet.

[0146] FIG. 13 is a schematic diagram showing an example of the data configuration of an investigation packet transmitted by the communication control unit 49A.

[0147] The investigation packet includes origin information, destination information, TTL, and data. The data field of the investigation packet includes a TTL initial value and transmission point information. The origin information, destination information, TTL, and TTL initial value are the same as those in the above embodiment. That is, in this embodiment, the investigation packet further includes transmission point information.

[0148] The transmission point information is information that indicates the transmission point of the investigation packet. The transmission point information includes at least one of the position of the GW node 10D at the time of transmission of the investigation packet and the transmission time. The position of the GW node 10D is the position of the GW node 10D in the wireless multi-hop mesh network 2 at the time of transmission of the investigation packet.

[0149] 10D, the explanation will be continued. The communication control unit 49A, like the communication control unit 48A, transmits an investigation packet at predetermined time intervals or when the TTL included in the packet received from the first node 10C is equal to or greater than the second threshold. At this time, the communication control unit 49A may further set transmission point information in the data field of the investigation packet and transmit it.

[0150] The communication control unit 49A executes the same processing as the communication control unit 48A of the above embodiment, except that it further sets transmission point information in the investigation packet.

[0151] As described above, in this embodiment, the communication control unit 49A transmits an investigation packet further including transmission point information to the first node 10C. Therefore, the communication control unit 49A of the GW node 10D can transmit information indicating the transmission point of the investigation packet to each of the first nodes 10C, and can notify each of the first nodes 10C of information used to calculate the setting TTL for each position of the GW node 10D.

[0152] Furthermore, similar to the communication control unit 48A in the above embodiment, when the TTL included in a packet received from the first node 10A is equal to or greater than the second threshold, the communication control unit 49A unicasts to the first node 10A an investigation packet that includes the TTL as a TTL correction value and also includes, as destination information, information indicating the first node 10A as the sender of the packet and unicast.

[0153] Here, it is assumed that neither the GW node 10D nor the first node 10C manages the position of the GW node 10D. In this case, when the GW node 10D moves within the wireless multi-hop mesh network 2, the position of the GW node 10D that is the destination of the packet transmitted by the first node 10A may differ from the position of the GW node 10D that the packet actually arrived at. In this case, the communication control unit 49A may make an erroneous determination as to whether the TTL included in the received packet is equal to or greater than the second threshold.

[0154] On the other hand, in the wireless communication system 1B of the present embodiment, the communication control unit 49A transmits an investigation packet including transmission point information to the first node 10A. Therefore, the communication control unit 49A of the GW node 10D can notify each of the first nodes 10C of information used to calculate the setting TTL for each position of the GW node 10D. Furthermore, the first node 10C manages the setting TTL, the TTL initial value, and the transmission point information for each position to which the GW node 10B moves, using the TTL initial value and transmission point information included in the investigation packet through processing described later (details will be described later). Therefore, the communication control unit 49A can prevent erroneous determination of whether the TTL included in the received packet is equal to or greater than the second threshold.

[0155] Next, an example of the functional configuration of the first node 10C of this embodiment will be described.

[0156] FIG. 14 is a schematic diagram of an example of the functional configuration of the first node 10C.

[0157] The first node 10C includes a storage unit 31, a communication unit 32, and a control unit 39. The first node 10C is similar to the first node 10A of the above embodiment, except that it includes a storage unit 31 instead of the storage unit 30 and a control unit 39 instead of the control unit 38.

[0158] The storage unit 31 stores management information 31A and schedule information 31B. Details of the management information 31A and schedule information 31B will be described later.

[0159] The control unit 39 includes a registration management unit 39A and a communication management unit 39B. The control unit 39 is similar to the control unit 38 of the above embodiment, except that the control unit 39 includes a registration management unit 39A instead of the registration management unit 38A, and a communication management unit 39B instead of the communication management unit 38B.

[0160] Similar to the registration management unit 38A in the above embodiment, the registration management unit 39A associates a setting TTL corresponding to the difference between the TTL and the initial TTL value included in the investigation packet based on the investigation packet received from the GW node 10D with a GWID, which is the second identification information of the GW node 10B, and registers the setting TTL in the management information 31A. In the present embodiment, the registration management unit 39A associates the setting TTL corresponding to the difference between the TTL and the initial TTL value included in the investigation packet and transmission point information included in the investigation packet with the GWID and registers them in the management information 31A.

[0161] 15 is a schematic diagram of an example of the data configuration of the management information 31A. The management information 31A is information in which a GWID, which is second identification information of the GW node 10B, a setting TTL, a TTL initial value, and transmission start point information are associated with each other. In other words, the management information 31A is information in which transmission point information is further registered in the management information 30A of the above embodiment.

[0162] Similar to the registration management unit 38A of the above embodiment, the registration management unit 39A calculates a setting TTL by subtracting the TTL included in the investigation packet from the initial TTL value included in the investigation packet.The registration management unit 39A then associates the calculated setting TTL, the GWID and initial TTL value included in the investigation packet used to calculate the setting TTL, and the transmission point information included in the investigation packet, and registers them in the management information 31A.That is, the registration management unit 39A further associates the transmission point information included in the investigation packet with the GWID and registers them in the management information 31A.

[0163] In this embodiment, the GW node 10D is capable of moving its position in the wireless multi-hop mesh network 2. For this reason, in the management information 31A, for one GWID, the setting TTL, the TTL initial value, and the transmission point information are registered for each position to which the GW node 10B identified by the GWID moves.

[0164] 14. Similar to the communication management unit 38B in the above embodiment, the communication management unit 39B sets the setting TTL corresponding to the GWID of the GW node 10B in the management information 31A as the TTL of a packet addressed to the GW node 10B, and transmits the packet.

[0165] In this embodiment, the GW node 10D included in the wireless multi-hop mesh network 2 is configured to be able to move its position in the wireless multi-hop mesh network 2.

[0166] Therefore, the communication management unit 39B uses the schedule information 31B and the transmission point information included in the investigation packet to identify the location of the GW node 10B at the time of transmission of the investigation packet.

[0167] The schedule information 31B is stored in the storage unit 31 in advance.

[0168] 16 is a schematic diagram showing an example of the data configuration of the schedule information 31 B. The schedule information 31 B is information in which GWIDs are associated with location information.

[0169] The point information is information that indicates the location of the GW node 10B at a certain time. The point information includes time information and position information.

[0170] The time information included in the location information is information that indicates the time when the GW node 10D is present at each position in the wireless multi-hop mesh network 2. The time information may be information that indicates a single timing, or may be information that indicates a predetermined period of time.

[0171] The position information included in the point information is information that indicates the position of the GW node 10D in the wireless multi-hop mesh network 2 where the GW node 10D is expected to be located at the time indicated by the corresponding time information.

[0172] In this embodiment, the GW node 10D is movable in position in the wireless multi-hop mesh network 2. For this reason, one or more pieces of location information are registered in advance in the schedule information 31B in association with one GWID.

[0173] Continuing the explanation by returning to Fig. 14, the communication management unit 39B identifies point information including time information of the scheduled transmission time corresponding to the GWID of the destination GW node 10D in the schedule information 31B.

[0174] In detail, the communication management unit 38B identifies the GWID of the destination GW node 10D and the scheduled transmission time of the packet. Then, the communication management unit 38B identifies point information that includes the scheduled transmission time as time information from the point information corresponding to the GWID of the destination GW node 10D in the schedule information 31B. Through these processes, the communication management unit 38B identifies the position of the destination GW node 10D in the wireless multi-hop mesh network 2 at the time of packet transmission.

[0175] Then, the communication management unit 39B identifies the setting TTL corresponding to the transmission point information representing the identified point information in the management information 31A.

[0176] In detail, the communication management unit 39B identifies transmission point information that matches the time information included in the identified point information or that includes information representing a transmission time included in the time information, or a location that matches the location information included in the identified point information, from among multiple pieces of transmission point information corresponding to the GWID of the destination GW node 10D in the management information 31A. Then, the communication management unit 39B identifies the setting TTL that corresponds to the identified transmission point information in the management information 31A.

[0177] Then, the communication management unit 39B sets the identified setting TTL as the TTL of the packet addressed to the GW node 10D, and transmits the packet.

[0178] As described above, in this embodiment, the investigation packet includes a GWID (second identification information), a TTL initial value, a TTL, and transmission point information including at least one of the location of the GW node 10D at the time of transmission of the investigation packet and the transmission time. The registration management unit 39A of the first node 10C associates a setting TTL corresponding to the difference between the TTL and the TTL initial value included in the investigation packet, and the transmission point information included in the investigation packet, with the GWID, and registers them in the management information 31A. The communication management unit 39B identifies point information in the schedule information 31B including time information of the scheduled transmission time corresponding to the GWID of the GW node 10D that is the destination, and sets the setting TTL corresponding to the transmission point information that represents the identified point information in the management information 31A as the TTL of the packet destined for the GW node 10D, and transmits the packet.

[0179] Therefore, in this embodiment, the wireless communication system 1 of the above embodiment can be applied to a wireless multi-hop mesh network 2 including a GW node 10D that is provided so that its position can be moved.

[0180] (Variation 1) In the above embodiment, an example has been described in which the Bluetooth Mesh described in Non-Patent Document 1 is used as the standard specification of the wireless multi-hop mesh network 2. However, the wireless multi-hop mesh network 2 may be any network that uses flooding communication, and the standard specification is not limited to Bluetooth Mesh. For example, the standard specification of the wireless multi-hop mesh network 2 may be RPL (IPv6 Routing Protocol for Low power and Lossy Network), ZigBee (registered trademark), etc.

[0181] (Variation 2) In the above embodiment, the registration management unit 38A of the first node 10A calculates the difference between the initial TTL value included in the investigation packet and the TTL included in the investigation packet as the setting TTL. In detail, the registration management unit 38A calculates the value obtained by subtracting the TTL included in the investigation packet from the initial TTL value included in the investigation packet as the setting TTL.

[0182] However, the registration management unit 38A may calculate a value corresponding to the difference between the TTL and the initial TTL value included in the inquiry packet as the setting TTL.

[0183] For example, the registration management unit 38A may register in the management information 30A a value obtained by subtracting the TTL included in the investigation packet from the initial TTL value included in the investigation packet and adding a predetermined buffer value to the result as a setting TTL, and associate it with the GWID.

[0184] The registration management unit 38A may also calculate the setting TTL using the following formula (2).

[0185] TTLm=Ti-maxTm+α Equation (2)

[0186] In equation (2), TTLm, Ti, Tm, and maxTm are the same as in equation (1), and α is a buffer value.

[0187] The buffer value may be previously determined according to the network topology of the wireless multi-hop mesh network 2. The buffer value may be changeable as needed by a user's operation instruction or the like.

[0188] When the link quality of the wireless multi-hop mesh network 2 is unstable or when packets are frequently transmitted within the wireless multi-hop mesh network 2, it may be difficult for a packet to arrive from the first node 10A to the GW node 10B via the shortest route. For this reason, the registration management unit 38A can provide some leeway to the setting TTL by using, as the setting TTL, a value obtained by subtracting the TTL included in the investigation packet from the TTL initial value included in the investigation packet and adding a predetermined buffer value to the value.

[0189] Therefore, by using a value including the buffer value as the setting TTL, it is possible to make the route redundant.

[0190] Next, an example of the hardware configuration of the node 10 of the above embodiment will be described.

[0191] FIG. 17 is a diagram illustrating an example of the hardware configuration of the node 10 according to the above embodiment.

[0192] The node 10 of the above embodiment is equipped with a control device such as a CPU (Central Processing Unit) 90B, a storage device such as a ROM (Read Only Memory) 90C and a RAM (Random Access Memory) 90D, an I / F unit 90A that interfaces with various devices, and a bus 90E that connects each unit, and has a hardware configuration that uses a normal computer.

[0193] In the node 10 of the above embodiment, the CPU 90B reads out a program from the ROM 90C onto the RAM 90D and executes it, thereby realizing the above-mentioned units on the computer.

[0194] The programs for executing the above-described processes executed by the node 10 in the above-described embodiment may be provided in the form of being pre-installed in the ROM 90C.

[0195] Furthermore, the program for executing the above-described processes executed by the node 10 of the above-described embodiment may be stored in an installable or executable file format on a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD (Digital Versatile Disc), or flexible disk (FD) and provided as a computer program product. Furthermore, the program for executing the above-described processes executed by the node 10 of the above-described embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Furthermore, the program for executing the above-described processes executed by the node 10 of the above-described embodiment may be provided or distributed via a network such as the Internet.

[0196] Although the embodiments of the present invention have been described above, the above embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0197] 1, 1B wireless communication system 10 nodes (wireless communication devices) 10A, 10C First node (first wireless communication device) 10B, 10D GW node (second wireless communication device) 38A, 39A Registration Management Department 38B, 39B Communication management department 48A, 49A Communication control section

Claims

1. a first wireless communication device that configures a wireless multi-hop mesh network and performs flooding communication; a second wireless communication device that configures the wireless multi-hop mesh network and is capable of communicating with an external network; A wireless communication system comprising: the first wireless communication device, based on an investigation packet received from the second wireless communication device, the investigation packet including second identification information of the second wireless communication device, a TTL (Time To Live) initial value, and a TTL, a registration management unit that registers a setting TTL corresponding to a difference between the TTL initial value and the TTL included in the investigation packet in management information in association with the second identification information; a communication management unit that sets the setting TTL corresponding to the second identification information in the management information as a TTL of a packet addressed to the second wireless communication device identified by the second identification information, and transmits the packet; Equipped with The registration management unit If the destination information included in the probe packet is information indicating a broadcast, registering the setting TTL in the management information according to the difference between the TTL initial value and the TTL included in the investigation packet; Wireless communication system.

2. The communication management unit When the packet received from the other first wireless communication device is forwarded to the second wireless communication device, If the TTL included in the packet is less than the setting TTL corresponding to the second identification information indicating the destination included in the packet or is 0, discard the received packet as a non-transfer target.

10. The wireless communication system of claim 1.

3. The registration management unit registering the setting TTL corresponding to the difference between the maximum value of the TTLs included in the plurality of investigation packets received from the second wireless communication device and the TTL initial value in the management information in association with the second identification information; 10. The wireless communication system of claim 1.

4. The registration management unit If the destination information included in the inquiry packet is information representing a unicast and the second wireless communication device, a value obtained by subtracting a TTL correction value included in the investigation packet from the setting TTL corresponding to the second identification information included in the investigation packet in the management information, and registering the result as a new setting TTL in the management information in association with the second identification information; 10. The wireless communication system of claim 1.

5. The registration management unit If the destination information included in the inquiry packet is information representing a unicast and another second wireless communication device, determining whether a difference between the TTL initial value included in another of the investigation packets previously received from the second wireless communication device and the TTL included in the investigation packet currently received is equal to or greater than a first threshold, and if the difference is equal to or greater than the first threshold, registering the difference as the setting TTL in the management information in association with the second identification information; 10. The wireless communication system of claim 1.

6. The registration management unit a value obtained by subtracting the TTL included in the investigation packet from the TTL initial value included in the investigation packet, or a value obtained by adding a predetermined buffer value to the subtracted value, is registered in the management information as the setting TTL in association with the second identification information.

10. The wireless communication system of claim 1.

7. The communication management unit When a packet originating from the first wireless communication device is transmitted to the second wireless communication device, transmit a packet in which the setting TTL corresponding to the second identification information of the second wireless communication device in the management information is set as a TTL; 10. The wireless communication system of claim 1.

8. the second wireless communication device, a communication control unit for transmitting the probe packet; 10. The wireless communication system of claim 1.

9. The communication control unit broadcasting the probe packet containing information indicating a broadcast as destination information at predetermined time intervals; 9. The wireless communication system according to claim 8.

10. The communication control unit If the TTL included in the packet received from the first wireless communication device is equal to or greater than a second threshold, the probe packet includes the TTL as a TTL correction value, and includes, as destination information, information indicating the first wireless communication device that is the sender of the packet and unicast.

9. The wireless communication system according to claim 8.

11. the second wireless communication device is provided so as to be movable in position in the wireless multi-hop mesh network; The probe packet includes: the second identification information, the TTL initial value, the TTL, and transmission point information including at least one of the location of the second wireless communication device at the time of transmitting the investigation packet and a transmission time, The registration management unit registering the setting TTL corresponding to the difference between the TTL initial value and the TTL included in the investigation packet and the transmission point information included in the investigation packet in the management information in association with the second identification information; The communication management unit identifying location information including time information of a scheduled transmission time corresponding to the second identification information of the second wireless communication device as a destination in schedule information that previously associates the second identification information of the second wireless communication device with time information and location information including location information of the location where the second wireless communication device is scheduled to be located at the time represented by the time information, and setting the setting TTL corresponding to the transmission location information representing the identified location information in the management information as a TTL of the packet addressed to the second wireless communication device, and transmitting the packet; 10. The wireless communication system of claim 1.

12. A wireless communication device that configures a wireless multi-hop mesh network and performs flooding communication, a registration management unit that, based on an investigation packet received from a second wireless communication device that configures the wireless multi-hop mesh network and is capable of communicating with an external network, includes second identification information of the second wireless communication device, a TTL initial value, and a TTL, registers a setting TTL corresponding to a difference between the TTL and the TTL initial value included in the investigation packet in management information in association with the second identification information; a communication management unit that sets the setting TTL corresponding to the second identification information in the management information as a TTL of a packet addressed to the second wireless communication device identified by the second identification information, and transmits the packet; Equipped with The registration management unit If the destination information included in the probe packet is information indicating a broadcast, registering the setting TTL in the management information according to the difference between the TTL initial value and the TTL included in the investigation packet; Wireless communication device.

13. A wireless communication method executed by a wireless communication device that configures a wireless multi-hop mesh network and performs flooding communication, comprising: a registration management step of registering a setting TTL corresponding to a difference between the TTL and the initial TTL value included in an investigation packet received from a second wireless communication device that configures the wireless multi-hop mesh network and is capable of communicating with an external network, in management information in association with the second identification information, based on the investigation packet including the second identification information of the second wireless communication device, an initial TTL value, and a TTL; a communication management step of setting the setting TTL corresponding to the second identification information in the management information as a TTL of a packet addressed to the second wireless communication device identified by the second identification information, and transmitting the packet; Including, The registration management step includes: If the destination information included in the probe packet is information indicating a broadcast, registering the setting TTL in the management information according to the difference between the TTL initial value and the TTL included in the investigation packet; Wireless communication method.

14. A wireless communication program executed on a computer that configures a wireless multi-hop mesh network and performs flooding communication, a registration management step of registering a setting TTL corresponding to a difference between the TTL and the initial TTL value included in an investigation packet received from a second wireless communication device that configures the wireless multi-hop mesh network and is capable of communicating with an external network, in management information in association with the second identification information, based on the investigation packet including the second identification information of the second wireless communication device, an initial TTL value, and a TTL; a communication management step of setting the setting TTL corresponding to the second identification information in the management information as a TTL of a packet addressed to the second wireless communication device identified by the second identification information, and transmitting the packet; Including, The registration management step includes: If the destination information included in the probe packet is information indicating a broadcast, registering the setting TTL in the management information according to the difference between the TTL initial value and the TTL included in the investigation packet; Wireless communication program.

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