COMMUNICATION SYSTEM, COMMUNICATION METHOD, AND COMMUNICATION PROGRAM

Abstract

A target node, which is a node (2) included in a communication system capable of constructing a multi-hop wireless communication network, includes a sink node and a plurality of nodes (2), and includes a communication control unit (22) and a transmitting / receiving unit (21). When the communication control unit (22) receives transfer data, which is data transmitted from a source node (2) addressed to the sink node and indicates an update value corresponding to the number of hops from the source node to the target node, the communication control unit (22) updates the first update value, which is the update value indicated in the received transfer data, to a post-update first update value. When the post-update first update value has not reached the transfer end value, the transmitting / receiving unit (21) transmits the transfer data with the updated first update value to the periphery of the target node. Here, the difference between the first update value and the post-update first update value corresponds to one hop, and the initial value of the update value indicated by the transfer data is a value corresponding to the number of hops from the source node to the sink node.

Description

[Technical Field]

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

[0002] Non-Patent Document 1 discloses a transfer method called flooding. In flooding, when each node receives data, it forwards the data to other nodes that are within its communication range. By repeating the data forwarding, the data finally reaches the destination node. At this time, parameters used in flooding forwarding control include the number of times data is transmitted from a node, the number of times data has been forwarded by a node, and the maximum number of hops over which data is forwarded. Since data is usually forwarded by multiple nodes, even if data is lost between certain nodes, the data will reach the destination node as long as another node has received the data. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] “Mesh Profile”,Bluetooth SIG,2019,v1.0.1,pp.18-19 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional flooding, the number of times data is transmitted from a node, the number of times data is forwarded by a node, the maximum number of hops over which data is forwarded, etc. are preset parameters, and parameter values ​​are set uniformly for all nodes according to the scale of the network. However, depending on the configuration or scale of the network, if appropriate parameter values ​​are not set for each node, data cannot be forwarded efficiently, which can lead to a problem of reduced transfer efficiency across the network. The present disclosure aims to improve the transfer efficiency of the entire network by allowing each node to transfer data efficiently in a multi-hop wireless communication network. [Means for solving the problem]

[0005] The communication system according to the present disclosure includes: A communication system that includes a sink node and a plurality of nodes and is capable of constructing a multi-hop wireless communication network, A target node, which is each node of the plurality of nodes, is a communication control unit that, when receiving forwarded data that is data transmitted from a source node included in the plurality of nodes to the sink node and indicates an update value corresponding to the number of hops from the source node to the target node, updates a first update value that is the update value indicated by the received forwarded data to a first update value after updating; a transmitting / receiving unit that transmits, when the post-update first update value has not reached a transfer end value, transfer data in which the first update value has been updated to the post-update first update value to a periphery of the target node; Equipped with a difference between the first update value and the updated first update value corresponds to one hop; The initial value of the update value indicated by the transfer data is a value corresponding to the number of hops from the source node to the sink node. [Effects of the Invention]

[0006] According to the present disclosure, a communication control unit of a target node included in a communication system capable of constructing a multi-hop wireless communication network updates a first update value, which is an update value indicated in the received forwarding data, to a post-update first update value. Thereafter, if the post-update first update value has not reached the forwarding end value, a transceiver unit of the target node transmits the forwarding data, in which the first update value has been updated to the post-update first update value, to the surrounding area of ​​the target node. Here, the difference between the first update value and the post-update first update value corresponds to one hop, and the initial value of the update value indicated by the forwarding data is a value corresponding to the number of hops from the source node to the sink node. Therefore, according to the present disclosure, the maximum number of times forwarding of forwarding data is a value corresponding to the number of hops from the source node to the sink node. Therefore, according to the present disclosure, in a multi-hop wireless communication network, the transfer efficiency of the entire network can be improved by each node transferring data efficiently. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a communication system 5 according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the structure of transfer data 150 according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing an example of the functional configuration of a sink node 1 according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing an example of the functional configuration of a node 2 according to the first embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the hardware configuration of a sink node 1 according to the first embodiment. [Figure 6] FIG. 1 is a diagram illustrating the operation of a communication system 5 according to the prior art. [Figure 7] 4 is a flowchart showing a procedure for setting an initial value I according to the first embodiment. [Figure 8] FIG. 4 is a sequence diagram showing a procedure for generating hop count information 160 according to the first embodiment. [Figure 9] FIG. 2 is a diagram for explaining transmission and reception of a forwarding hop number signal according to the first embodiment. [Figure 10] FIG. 1 is a diagram showing hop count information 160 according to the first embodiment. [Figure 11] 4 is a flowchart showing a procedure for setting an initial value I according to the first embodiment. [Figure 12] FIG. 10 is a diagram showing an example of a hardware configuration of a sink node 1 according to a modification of the first embodiment. [Figure 13] FIG. 10 is a sequence diagram showing a procedure for setting the number of transmissions according to the second embodiment. [Figure 14] 10 is a flowchart showing a procedure for setting the number of transmissions according to the second embodiment. [Figure 15] FIG. 11 is a sequence diagram showing a procedure for setting a forwarding function according to the third embodiment. [Figure 16] 11 is a flowchart showing a procedure for setting a forwarding function according to the third embodiment. [Figure 17] FIG. 10 is a diagram showing an example of the configuration of a communication system 6 according to a fourth embodiment. [Figure 18] FIG. 11 is a sequence diagram showing a procedure for setting a forwarding function according to the fourth embodiment. [Figure 19] FIG. 11 is a sequence diagram showing a procedure for setting a forwarding function according to the fourth embodiment. [Figure 20] FIG. 11 is a sequence diagram showing a procedure for setting a forwarding function according to the fourth embodiment. [Figure 21] FIG. 13 is a diagram showing the data structure of a message transmission instruction according to the fourth embodiment. [Figure 22] FIG. 13 is a diagram showing the data structure of a measurement result notification according to the fourth embodiment. [Figure 23] 10 is a flowchart showing a counting process according to the fourth embodiment. [Figure 24] FIG. 13 is a diagram for explaining an example of selecting a forwarding node according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the description of the embodiments and the drawings, the same elements and corresponding elements are given the same reference numerals. The description of elements given the same reference numerals will be omitted or simplified as appropriate. Arrows in the drawings mainly indicate the flow of data or the flow of processing. Furthermore, "unit" may be read as "circuit," "step," "procedure," "process," or "circuitry" as appropriate.

[0009] Embodiment 1 Hereinafter, this embodiment will be described in detail with reference to the drawings. The first embodiment aims to improve the transfer efficiency of data transmitted from each node 2 to the sink node 1.

[0010] ***Configuration Description*** Fig. 1 is a diagram illustrating an example of the configuration of a communication system 5 according to the first embodiment. The communication system 5 includes a sink node 1, which is an example of a sink node, and a plurality of nodes 2. In Fig. 1, the communication system 5 includes the sink node 1 and nodes 2-1 to 2-13, which are examples of the plurality of nodes 2. The communication system 5 is also capable of building a multi-hop wireless communication network. Note that, although Fig. 1 illustrates one sink node 1 and thirteen nodes 2, the number of sink nodes 1 and the number of nodes 2 are not limited to the example shown in Fig. 1. Hereinafter, when referring to multiple nodes 2 without distinguishing them individually, they will be referred to as "nodes 2." The sink node 1 and nodes 2 may also be collectively referred to as "nodes." The sink node 1 and each node 2 transmit and receive data (also referred to as signals or information in this specification) to and from each other. In particular, each node 2 transmits data addressed to the sink node 1 frequently.

[0011] 2 is a diagram showing the structure of transfer data 150 according to embodiment 1. The transfer data 150 is data transmitted from each node 2 to the sink node 1, data transmitted and received at each node 2, and data indicating a source node ID (Identification) 151, a destination node ID 152, and an update value U. The source node ID 151 is an ID indicating the source node that is the source of the transfer data 150. The ID is a code for identifying the sink node 1 and the node 2. The destination node ID 152 is an ID that indicates the destination node to which the transfer data 150 is sent. The update value U is an update value for the upper limit of the number of hops, and indicates the maximum number of remaining hops that the forwarding data 150 being forwarded is allowed to make. The value of U is the same as the value of the initial value I at the time the source node transmits the forwarding data 150, and is decremented by one each time the sink node 1 or node 2 (hereinafter simply referred to as the receiving node) that received the forwarding data 150 forwards the forwarding data 150. The initial value I indicates the initial value of the update value U, and indicates the upper limit of the number of hops. The forwarding data 150 is allowed to hop a maximum of I times from the source node.

[0012] 3 is a diagram showing an example of the functional configuration of the sink node 1. The sink node 1 includes a transmitting / receiving unit 11, a communication control unit 12, and a storage unit 13. The transmitter / receiver 11 communicates data with each node 2. When the transmitter / receiver 11 receives a signal from a node 2, it outputs the received signal to the communication control unit 12. In addition, the transmitter / receiver 11 transmits the signal to the node 2 based on an instruction from the communication control unit 12. When the communication control unit 12 receives a signal from the transmitting / receiving unit 11, it carries out a predetermined process based on the received signal. The storage unit 13 stores data necessary to realize the functions of the communication system 5 as appropriate.

[0013] 4 is a diagram illustrating an example of the functional configuration of the node 2. The node 2 includes a transmitting / receiving unit 21, a communication control unit 22, and a storage unit 23.

[0014] The transmitter / receiver 21 communicates data with another node in the multi-hop wireless communication network, such as a sink node 1 or a node 2. When the transmitter / receiver 21 receives a signal from another node, the transmitter / receiver 21 outputs the received signal to the communication control unit 22. The transmitter / receiver 21 also transmits the signal to the other node based on an instruction from the communication control unit 22. When each node 2 of the plurality of nodes 2 is a target node, if the post-update first update value described below has not reached the transfer end value, the transmitter / receiver 21 of the target node transmits transfer data 150 in which the post-update first update value described below has been updated to the post-update first update value to the surrounding area of ​​the target node. As a specific example, the transfer end value is 0. Here, the difference between the first update value and the post-update first update value corresponds to one hop. An initial value I, which is the initial value of the update value U indicated by the transfer data 150, corresponds to the number of hops from the source node to the sink node 1. In addition, if the second update value after update described below has not reached the transfer end value, the transmitter / receiver unit 21 of the target node transmits a transfer hop count signal in which the second update value described below has been updated to the second update value after update to the surrounding area of ​​the target node.

[0015] When the communication control unit 22 receives a signal from the transmitting / receiving unit 21, it performs a predetermined process based on the received signal. When the communication control unit 22 of the target node receives the transfer data 150, it updates the first update value, which is the update value U indicated in the received transfer data 150, to the updated first update value. The transfer data 150 is data transmitted from a source node included in the plurality of nodes 2 to the sink node 1, and is data indicating the update value U. The update value U is a value corresponding to the number of hops from the source node to the target node. Furthermore, when the target node receives a forwarding hop number signal, the communication control unit 22 of the target node calculates the number of hops from the target node to the sink node 1 based on the second update value and the initial value indicated by the received forwarding hop number signal, stores the calculated hop number as the minimum number of hops from the target node to the sink node 1, and updates the second update value indicated by the received forwarding hop number signal to the post-update second update value. The forwarding hop number signal is a signal transmitted from the sink node 1 and indicates the second update value, which is an update value corresponding to the number of hops from the sink node 1 to the target node, and the initial value of the second update value. The difference between the second update value and the post-update second update value corresponds to one hop. The minimum hop number is used as the initial value of the update value indicated by the first transmission data when the target node transmits first transmission data to the sink node 1. When the forwarding hop number signal reaches the target node via multiple routes, the communication control unit 22 of the target node may store, as the minimum hop number, the number of hops corresponding to the shortest route among the multiple routes whose corresponding reception strength is equal to or greater than a first reference reception strength. That is, the minimum hop count stored by the target node is not limited to the actual minimum hop count from the sink node 1 to the target node, but may be the number of hops corresponding to the shortest route among routes by which data can be transferred from the sink node 1 to the target node, or from the target node to the sink node 1. The first reference reception strength may be determined in any way. The communication control unit 22 of the target node may treat only the nodes 2 of which the corresponding reception strength is equal to or greater than the second reference reception strength as valid nodes 2. In other words, the communication control unit 22 of the target node may ignore the nodes 2 of which the corresponding reception strength is less than the second reference reception strength. The second reference reception strength may be determined in any way.

[0016] The storage unit 23 stores data necessary to realize the functions of the communication system 5 as appropriate.

[0017] 5 is a diagram showing an example of the hardware configuration of the sink node 1. The sink node 1 includes a control circuit 100, a transmitter 103, and a receiver 104. The control circuit 100 includes a processor 101 and a memory 102 . The processor 101 is a processing circuit that performs calculations such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The control circuit 100 may include multiple processors that replace the processor 101. The multiple processors share the role of the processor 101. The memory 102 is a storage device that includes a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The functions of each unit of the sink node 1 are realized by the processor 101 executing a communication program for realizing the operation of the sink node 1, which is stored in the memory 102. The functions of each unit of the sink node 1 are realized by software. The communication program may be recorded on a computer-readable non-volatile recording medium. Specific examples of the non-volatile recording medium are an optical disk or a flash memory. The communication program may be provided as a program product. The storage unit 13 is realized by the memory 102 . The transmitter 103 is a device that transmits data to the surrounding area. The receiver 104 is a device that receives data from the surroundings. The transmitter / receiver 11 is realized by the transmitter 103 and the receiver 104. The hardware configuration of node 2 is similar to that of sink node 1, so a description of the hardware configuration of node 2 will be omitted.

[0018] ***Explanation of Operation*** The operation procedure of the communication system 5 corresponds to a communication method, and the program that realizes the operation of the communication system 5 corresponds to a communication program.

[0019] 6 shows an example of a process for transmitting transfer data 150 to a sink node 1 in a communication system 5 according to the prior art. FIG. 6 illustrates a data transfer path when data is transmitted from node 2-1 to sink node 1. As described above, transfer data 150 indicates a source node ID 151, a destination node ID 152, an initial value I, and an update value U. In this example, source node ID 151 indicates the ID of node 2-1, and destination node ID 152 indicates the ID of sink node 1. Each receiving node determines whether to forward the received forwarding data 150 based on the destination node ID 152 indicated in the forwarding data 150 received from another node and the update value U. Specifically, if the destination node ID 152 indicates the receiving node itself, the receiving node does not forward the forwarding data 150 because forwarding is unnecessary. Also, if the result of subtracting 1 from the update value U reaches 0 or a standard value, the receiving node does not forward the forwarding data 150 because further forwarding is not permitted. In the example shown in FIG. 6, the destination node ID 152 of the transfer data 150 indicates that the sink node 1 is the destination, so when the sink node 1 receives the transfer data 150, it does not transfer the target data. In the example shown in FIG. 6, the initial value I is 5, and each arrow indicates the transfer of the transfer data 150, with each arrow indicating the update value U at the time corresponding to the arrow. As a specific example, the update value U of the transfer data 150 transferred to node 2-12 is 1. Therefore, node 2-12 determines that the result of subtracting 1 from the update value U reaches 0, and does not transfer the transfer data 150. In other words, in the example shown in FIG. 6, the maximum number of hops is limited to 5. Here, the update value U indicated in the transfer data 150 received by node 2-12 corresponds to the first update value, and the result of subtracting 1 from the update value U corresponds to the post-update first update value. Therefore, the difference between the first update value and the post-update first update value corresponds to one hop. Note that no forwarding path is set in the communication system 5. Therefore, even if the forwarding data 150 indicates the node 2-1 as the source node and the sink node 1 as the destination node, the forwarding path may accidentally change each time an attempt is made to transmit the forwarding data 150. As a specific example, the reception strength may change with each attempt, and there may be a node 2 that cannot receive the data (or conversely, can receive the data), so whether or not a forwarding path is formed may vary depending on whether or not the forwarding data 150 is received. Furthermore, since the latency of each forwarding path may change with each attempt, the node that can start forwarding first among adjacent nodes may change with each attempt, and as a result, the direction of forwarding may also change with each attempt.

[0020] In a conventional multi-hop wireless communication network using flooding, the initial value I is set uniformly for each node 2 according to the scale of the network. Therefore, when data transmission from node 2 to a destination node with a relatively small minimum number of hops from node 2 occurs, unnecessary transfers may occur, such as transfers via nodes 2-7, as shown in the example of FIG. On the other hand, in this embodiment, in order to improve the transfer efficiency to the destination node, each node 2 holds hop count information 160 corresponding to that node 2, and when transmitting transfer data 150 destined for sink node 1, the hop count information 160 is used to appropriately set the initial value I and transmit the transfer data 150. The hop count information 160 corresponding to each node 2 is information indicating the number of hops from each node 2 itself to each sink node 1. Therefore, according to this embodiment, the transfer efficiency of transfer data 150 destined for sink node 1 can be improved.

[0021] Fig. 7 is a flowchart showing an example of a procedure for setting the initial value I in each node 2. The procedure for setting the initial value I will be described using Fig. 7. In the following, it is assumed that there is one sink node 1 in the communication system 5. If there are multiple sink nodes 1 in the communication system 5, the following process is executed for each sink node 1.

[0022] (Step S50) The communication control unit 22 generates hop count information 160 and proceeds to step S51. The hop count information 160 is information that lists the minimum number of hops required to reach the sink node 1 from the node 2 for which the hop count information 160 was generated. Hereinafter, the minimum number of hops from the node 2 for which the hop count information 160 was generated to the sink node 1 will also be simply referred to as the number of hops to the sink node 1. Hereinafter, there may be multiple routes from a certain node 2 to a certain sink node 1. Specifically, there may be multiple routes for transmitting one piece of transfer data 150, and when an attempt is made to transmit new transfer data 150, the route may change as described above. Furthermore, the number of stages may not be the same between each route. Therefore, the hop count information 160 is basically information that lists and stores multiple hop counts. The procedure for generating the hop count information 160 will be described in detail later.

[0023] (Step S51) The communication control unit 22 selects one hop number corresponding to the sink node 1 from the hop numbers indicated in the hop number information 160 generated as the hop number of the sink node 1, and sets the selected hop number as the initial value I of the transfer data 150 when transmitting the transfer data 150 addressed to the sink node 1 in the future. The method of setting the initial value I will be described in detail later.

[0024] 8 is a sequence diagram showing an example of a procedure for generating the hop count information 160 in the communication system 5. The procedure for generating the hop count information 160 will be described with reference to FIG.

[0025] (Step S1) The sink node 1 transmits a forwarding hop count signal, which is a signal for generating the hop count information 160. Specifically, the communication control unit 12 generates a forwarding hop count signal and transmits the generated forwarding hop count signal to a group address or a unicast address via the transmitting / receiving unit 11. Here, the forwarding hop count signal stores the ID of the sink node 1 as the source node ID 151, an initial value I, and an updated value U. At the time when the sink node 1 transmits the forwarding hop count signal, the initial value I and the updated value U are the same value.

[0026] (Step S2) Upon receiving the number of forwarding hops signal, the node 2-1 subtracts 1 from the update value U indicated by the received number of forwarding hops signal and then forwards the received number of forwarding hops signal. Specifically, first, upon receiving the forwarding hop number signal, the transmitting / receiving unit 21 outputs the received forwarding hop number signal to the communication control unit 22. Next, the communication control unit 22 updates the update value U indicated by the forwarding hop number signal received from the transmitting / receiving unit 21 to a value obtained by subtracting one from the update value U. Next, the communication control unit 22 outputs the signal in which the update value U has been updated to the transmission / reception unit 21. Next, the transmitting / receiving unit 21 transfers the signal received from the communication control unit 22 as a transfer hop number signal.

[0027] (Step S3) When node 2-1 receives the forwarding hop count signal, it stores data indicating the number of hops to the sink node 1 and the average reception strength for each hop count in the storage unit 23. Note that the forwarding hop count signal may reach node 2-1 via multiple routes, and when the forwarding hop count signal reaches node 2-1 via multiple routes, node 2-1 stores data corresponding to each of the multiple routes in the storage unit 23. The average reception strength for a certain hop count at a target node is an average value calculated when the target node receives a target signal multiple times via a route corresponding to that certain hop count, and is the average value of the reception strength of the target signal at the target node. Specifically, first, the communication control unit 22 calculates the number of hops from node 2-1 to the sink node 1 using the initial value I and the updated value U indicated in the forwarding hop signal received from the transmitting / receiving unit 21. The number of hops from node 2-1 to the sink node 1 is a value calculated by I-U+1 [Formula 1]. Next, the communication control unit 22 stores data indicating the calculated number of hops and the average reception strength for each number of hops in the storage unit 23 as hop number information 160. Here, the hop number information 160 is information that associates the number of hops with the average reception strength corresponding to the number of hops.

[0028] Step S4 is similar to step S2, and therefore a description thereof will be omitted. Step S5 is similar to step S3, and therefore a description thereof will be omitted. After that, although not shown in the figure, each node 2 that receives the forwarding hop number signal forwarded from another node 2 executes the same processing as steps S4 and S5.

[0029] Fig. 9 is a diagram showing an example of transmission and reception of a forwarding hop number signal according to the first embodiment. Fig. 9 shows an example in which data transmitted from sink node 1 reaches node 2-1 via two routes. Specifically, the first route (called route 1) is a route that travels directly from sink node 1 to node 2-1. The second route (called route 2) is a route that passes through each node in the order of sink node 1, node 2-3, node 2-2, and node 2-1. Fig. 9 shows an example in which the initial value I is 5, and an updated value U at the time corresponding to each arrow is shown near each arrow. The forwarding hop count signal received by node 2-1 via route 1 indicates an updated value U of 5, so the number of hops from sink node 1 to node 2-1 is 5-5+1=1 according to [Formula 1]. Also, the forwarding hop count signal received by node 2-1 via route 2 indicates an updated value U of 3, so the number of hops from sink node 1 to node 2-1 is 5-3+1=3 according to [Formula 1].

[0030] 10 is a diagram illustrating an example of hop count information 160 according to the first embodiment. The hop count information 160 is information that associates the number of hops from node 2 to sink node 1 with the average reception strength corresponding to the number of hops. In the example illustrated in FIG. 10, it is shown that the number of hops corresponding to path 1 is 1 and the average reception strength corresponding to path 1 is 30. It is also shown that the number of hops corresponding to path 2 is 3 and the average reception strength corresponding to path 2 is 50.

[0031] 11 is a flowchart showing an example of a procedure for setting the initial value I in the node 2. The procedure for setting the initial value I will be described with reference to FIG.

[0032] (Step S21) The communication control unit 22 sets 1 as the initial value of the variable h.

[0033] (Step S22) The communication control unit 22 determines whether the value of h corresponds to any of the hop numbers indicated by the hop number information 160 stored in the storage unit 23. If h corresponds to any of the hop numbers indicated by the hop number information 160, the communication control unit 22 proceeds to step S24. Otherwise, the communication control unit 22 proceeds to step S23.

[0034] (Step S23) The communication control unit 22 increments the value of h by 1 and repeats the process from step S22.

[0035] (Step S24) The communication control unit 22 determines whether the average reception strength corresponding to the number of hops equal to the value of h is equal to or greater than the value of a predetermined variable p. If the average reception strength for the number of hops is less than the value of variable p (step S24 NO), communication control unit 22 increments the value of h by 1 (step S23) and repeats the process from step S22. If the average reception strength for the number of hops is equal to or greater than the value of variable p (step S24 YES), communication control unit 22 proceeds to step S25.

[0036] (Step S25) The communication control unit 22 sets the value of h to the initial value I. That is, each node 2 uses the h calculated by the above procedure as the initial value I when it becomes a data transmission source in the future.

[0037] 10, when the value of variable p is 40, route 1 is the route with the smallest number of hops, but the average received signal strength corresponding to route 1 is less than the value of variable p, so route 1 is not selected. On the other hand, the average received signal strength corresponding to route 2 is equal to or greater than the value of variable p, so the number of hops of route 2 (i.e., 3) is selected. Therefore, in node 2-1, 3 is set as the initial value I of transfer data 150 addressed to sink node 1. This initial value I corresponds to the number of hops from the source node to sink node 1 when node 2-1 is the source node.

[0038] Through the above processing, node 2 can select an appropriate hop count from the hop counts indicated by the multiple hop count signals it has received, and transmit transfer data 150 with the selected hop count set to initial value I.

[0039] ***Explanation of the effect of the first embodiment*** As described above, in this embodiment, each node 2 holds hop count information 160 indicating the number of hops from each node 2 itself to the sink node 1, and uses the held hop count information 160 to appropriately set the initial value I of the transfer data 150 addressed to the sink node 1, and transmits the transfer data 150. As a result, even if a transmission occurs from a node that is a relatively small number of hops from the destination node, it is possible to suppress the occurrence of unnecessary transfers by other nodes 2, thereby realizing communication with relatively high transfer efficiency. Furthermore, each node 2 sets an initial value I of the transfer data 150 destined for the sink node 1 using the number of hops from each node 2 to the sink node 1. This allows the initial value I for transmissions destined for the sink node 1, which accounts for most of the communications carried out in the communication system 5, to be appropriate, thereby effectively improving the transfer efficiency of the communication system 5 as a whole. In the first embodiment, the number of hops is calculated based on the sink node 1, and an initial value I for data destined for the sink node 1 is determined for each node 2. However, the present embodiment is not limited to this example, and the number of hops may be calculated and the initial value I may be set based on any of the nodes 2 constituting the communication system 5.

[0040] ***Other Configurations*** <Variation 1> FIG. 12 shows an example of the hardware configuration of the sink node 1 according to this modification. The sink node 1 includes a processing circuit 108 instead of the processor 101 or the processor 101 and the memory 102 . The processing circuit 108 is hardware that realizes at least a part of the components of the sink node 1 . The processing circuitry 108 may be dedicated hardware, or may be a processor that executes a program stored in the memory 102 .

[0041] When processing circuitry 108 is dedicated hardware, processing circuitry 108 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The sink node 1 may include a plurality of processing circuits that replace the processing circuit 108. The plurality of processing circuits share the role of the processing circuit 108.

[0042] In the sink node 1, some functions may be realized by dedicated hardware, and the remaining functions may be realized by software or firmware.

[0043] The processing circuitry 108 is illustratively implemented in hardware, software, firmware, or a combination thereof. The processor 101, memory 102, and processing circuit 108 are collectively referred to as “processing circuitry.” In other words, the functions of the functional components of the sink node 1 are realized by the processing circuitry. The sink node 1 according to other embodiments may also have the same configuration as this modified example.

[0044] Embodiment 2 The following mainly describes the differences from the above-described embodiment with reference to the drawings.

[0045] ***Configuration Description*** The configuration according to this embodiment is the same as the configuration according to the first embodiment. When the number of one or more nodes 2 that are present within the communication range of the target node and that can forward the second transmission data when transmitting the second transmission data from the target node to the sink node 1 is equal to or less than the reference number of adjacent nodes, the communication control unit 22 of the target node increases both the number of times the target node transmits the second transmission data and the number of times the target node transmits the forwarded data. The reference number of adjacent nodes may be determined in any way.

[0046] ***Explanation of Operation*** The following description will focus mainly on the differences from embodiment 1. Note that in embodiment 2, the procedure up to when each node 2 generates hop count information is the same as in embodiment 1.

[0047] 13 is a sequence diagram showing an example of a procedure for setting the number of transmissions in node 2. The procedure for setting the number of transmissions will be described with reference to FIG.

[0048] (Step S101) The node 2-1 stores in the storage unit 23 data indicating the number of hops calculated in the procedure for setting the initial value I according to the first embodiment. Step S102 is similar to step S101.

[0049] (Step S103) The node 2-1 transmits a minimum hop count signal including information indicating the minimum hop count from the sink node 1 to the node 2-1 to the adjacent node corresponding to the node 2-1. The adjacent node corresponding to the target node is each node 2 with which the target node can communicate. Step S104 is similar to step S103.

[0050] (Step S105) When node 2-1 receives the minimum hop count signal, it stores data indicating the source node ID indicated by the received minimum hop count signal, the number of receiving devices for each hop count, and the average reception strength for each hop count in storage unit 23. The source node ID is the same as source node ID 151. Step S106 is similar to step S105.

[0051] Although not shown, each node 2 that receives a minimum hop number signal transmitted from another node 2 subsequently executes the processes shown in steps S101, S103, and S105, similar to node 2-1.

[0052] 14 is a flowchart showing an example of a procedure for setting the number of transmissions in the target node, which is node 2. The procedure for setting the number of transmissions will be described with reference to FIG.

[0053] (Step S121) The communication control unit 22 counts the number of first adjacent nodes corresponding to the target node in terms of the minimum hop count and calculates the total number of first adjacent nodes. The first adjacent nodes corresponding to the target node consist of adjacent nodes having the same minimum hop count as the target node's minimum hop count and adjacent nodes having one minimum hop count less than the target node's minimum hop count. The first adjacent node corresponds to node 2, which serves as the forwarding node when transmitting forwarded data 150 from the target node to sink node 1. In other words, the first adjacent node corresponds to node 2, which exists within the communication range of the target node and can forward second transmission data when transmitting second transmission data from the target node to sink node 1. Note that the counting in step S121 may be limited to nodes 2 whose average reception strength exceeds a predetermined threshold value, thereby making it possible to calculate the number of first adjacent nodes that are capable of normal communication and are essentially valid.

[0054] (Step S122) The communication control unit 22 determines whether the total number calculated in step S121 is equal to or less than the value of a predetermined variable j. If the total number of devices exceeds the value of variable j, the communication control unit 22 ends the process. Otherwise, the communication control unit 22 proceeds to step S126.

[0055] (Step S123) The communication control unit 22 increases the number of transmissions at the time of initial transmission and the number of transmissions at the time of transfer to predetermined values.

[0056] By the above process, it is possible to appropriately increase the number of transmissions only to the node 2 that has a relatively small number of first adjacent nodes that will be forwarding nodes when transmitting the forwarded data 150 to the sink node 1.

[0057] ***Explanation of the effect of the second embodiment*** As described above, in this embodiment, node 2 appropriately increases the number of transmissions only to nodes 2 that have a relatively small number of first adjacent nodes. This makes it easier for data to reach between adjacent nodes even when there are a small number of first adjacent nodes, thereby achieving communication with a relatively high transfer efficiency.

[0058] Embodiment 3 The following mainly describes the differences from the above-described embodiment with reference to the drawings.

[0059] ***Configuration Description*** The configuration according to this embodiment is the same as the configuration according to the first embodiment. The communication control unit 22 of the target node controls the forwarding function of the target node in accordance with the number of nodes 2 present within the communication range of the target node among the plurality of nodes 2 and the number of nodes 2 present within the communication range of each node 2 present within the communication range of the target node among the plurality of nodes 2. As the control of the forwarding function of the target node, the communication control unit 22 of the target node may either disable the forwarding function of the target node or set the number of times the target node transmits the transfer data 150.

[0060] ***Explanation of Operation*** The following mainly describes the differences from the first embodiment. 15 is a sequence diagram showing an example of a procedure for setting the forwarding function in node 2. The procedure for setting the forwarding function will be described with reference to FIG.

[0061] (Step S201) The sink node 1 transmits a signal to confirm the number of adjacent nodes to the adjacent nodes.

[0062] (Step S202) The node 2-1 transmits a signal to confirm the number of adjacent nodes to the adjacent nodes. Step S203 is similar to step S202.

[0063] (Step S204) When node 2-1 receives the adjacent node number confirmation signal, it stores data indicating the source node ID indicated by the adjacent node number confirmation signal, the average reception strength of each node 2, and the number of adjacent nodes that are the source of the adjacent node number confirmation signal received by node 2-1 in storage unit 23. The source node ID is the same as source node ID 151. Step S205 is similar to step S204.

[0064] (Step S206) The node 2-1 transmits to the adjacent nodes an adjacent node number notifying signal including information indicating the number of adjacent nodes corresponding to the node 2-1. Step S207 is similar to step S206.

[0065] (Step S208) When node 2-1 receives the adjacent node number notification signal, it stores data in memory 23 indicating the source node ID indicated by the received adjacent node number notification signal, the average reception strength of each node 2, and the number of adjacent nodes from each node 2. Step S209 is similar to step S208.

[0066] Although not shown, the node 2 that receives the adjacent node number confirmation signal transmitted from another node 2 executes the processes shown in steps S204, S206, and S208 in the same manner as node 2-1.

[0067] 16 is a flowchart showing an example of a procedure for setting the forwarding function in the target node, which is node 2. The procedure for setting the forwarding function will be described with reference to FIG.

[0068] (Step S221) The communication control unit 22 determines whether or not the number of adjacent nodes corresponding to each node 2 is equal to or greater than the value of a predetermined variable f. If the number of adjacent nodes corresponding to any node 2 is less than the value of variable f, the communication control unit 22 ends the process. Otherwise, the communication control unit 22 proceeds to step S222.

[0069] (Step S222) The communication control unit 22 determines whether the average reception strength of all neighboring nodes with respect to the target node is equal to or greater than the value of a predetermined variable g. If the average reception strength of any of the adjacent nodes is less than the value of the variable g, the communication control unit 22 ends the process. Otherwise, the communication control unit 22 proceeds to step S223.

[0070] (Step S223) The communication control unit 22 determines whether the node 2 having the largest number of adjacent nodes among the adjacent nodes and the target node is the only node. If the target node is the only node 2 having the largest number of adjacent nodes, the communication control unit 22 proceeds to step S225, otherwise the communication control unit 22 proceeds to step S224.

[0071] (Step S224) The communication control unit 22 determines whether there is a node 2 whose forwarding function should be disabled based on a predetermined setting condition. Specific examples of the setting condition include selecting a certain number of nodes 2 in ascending order of node ID value and disabling the forwarding function of the selected nodes 2, randomly selecting a certain number of node IDs and disabling the forwarding function of the selected nodes 2, or disabling the forwarding function of each node 2 after a random time has elapsed. If the set condition is met, that is, if there is a node 2 whose forwarding function should be disabled, the communication control unit 22 proceeds to step S225. Otherwise, the communication control unit 22 ends the process. Note that the communication control unit 22 enables the forwarding function of each node 2 whose forwarding function should not be disabled.

[0072] (Step S225) The communication control unit 22 disables the forwarding function of the target node. Furthermore, if the communication control unit 22 determines in step S224 that there is a node 2 whose forwarding function should be disabled, it disables the forwarding function of each node 2 whose forwarding function should be disabled in accordance with the set conditions. The node whose forwarding function has been disabled transmits a forwarding function disabled notification signal to adjacent nodes to notify them that the forwarding function has been disabled. When node 2 receives the forwarding function disabled notification signal, it erases from memory unit 23 of node 2 the data indicating the source node ID corresponding to the received forwarding function disabled notification signal, the average reception strength of each node 2, and the number of adjacent nodes corresponding to each node 2. Except for node 2 whose forwarding function has been disabled, each node 2 repeats the process from sending and receiving the adjacent node number confirmation signal.

[0073] Through the above process, node 2 can set the forwarding function to be enabled or disabled after grasping the number of adjacent nodes corresponding to the adjacent nodes. When disabling the forwarding function, the target node may change the number of transmissions during forwarding of the target node to a predetermined value instead of disabling the forwarding function.

[0074] ***Explanation of the effect of the third embodiment*** As described above, in this embodiment, each node 2 determines the number of adjacent nodes corresponding to the adjacent nodes and then enables or disables the forwarding function of each node 2. This makes it possible to suppress the number of forwarding operations until the forwarded data 150 reaches the destination node, even when adjacent nodes are densely located around each node 2, thereby achieving communication with relatively high forwarding efficiency.

[0075] Embodiment 4 The following mainly describes the differences from the above-described embodiment with reference to the drawings.

[0076] ***Configuration Description*** Fig. 17 is a diagram showing an example of the configuration of a communication system 6 according to the fourth embodiment. The communication system 6 includes a sink node 3, which is an example of a sink node, and a plurality of nodes 4. In Fig. 17, the communication system 6 includes the sink node 3 and nodes 4-1 to 4-6, which are examples of a plurality of neighboring nodes 4. The communication system 6 is also capable of building a multi-hop wireless communication network. 17 illustrates one sink node and six nodes 4, but the number of sink nodes 3 and the number of nodes 4 are not limited to the example shown in FIG. 17. Hereinafter, when referring to multiple nodes 4 without distinguishing them individually, they will be referred to as "nodes 4." The sink nodes 3 and nodes 4 may also be collectively referred to as "nodes." The configuration of sink node 3 is similar to that of sink node 1. The configuration of node 4 is similar to that of node 2.

[0077] When a problem node exists among the nodes 4 that exist within the communication range of the sink node 3 among the multiple nodes 4, the communication control unit 12 of the sink node 3 selects a node 4 that exists within the communication range of the problem node as a selected node from among the nodes 4 that exist within the communication range of the sink node 3 according to the reception strength corresponding to communication between each node 4 that exists within the communication range of the problem node and the problem node. A problem node is a node 4 that cannot communicate normally with the sink node 3. The communication control unit 22 of the selector node controls the transfer function of the selector node so that the data transmitted by the problem node to the sink node 3 can be transferred.

[0078] ***Explanation of Operation*** 18 to 20 are sequence diagrams showing an example of a procedure for setting up a forwarding function in a node 4. The procedure for setting up a forwarding function will be described with reference to Fig. 18 to 20. Note that each node 4 according to this example is a node 4 that exists within the communication range of a sink node 3.

[0079] (Step S301) The sink node 3 transmits a message transmission instruction to each node 4 a certain number of times. 21 is a diagram showing the data structure of a message transmission instruction. The message transmission instruction is data including information indicating each of the source node ID, the destination node ID, and the number of times the measurement message is transmitted. The source node ID is the same as the source node ID 151 . The destination node ID is the same as the destination node ID 152 . The number of times a measurement message is transmitted is the number of times a measurement message is transmitted to an adjacent node. Steps S303 and S305 are similar to step S301.

[0080] (Step S302) Upon receiving the message transmission instruction, node 4-1 transmits to sink node 3 a message transmission confirmation indicating that the message transmission instruction has been received. Steps S304 and S306 are each similar to step S302.

[0081] (Step S307) The node 4-1 repeatedly transmits the measurement message to the adjacent node the number of times indicated in the received message transmission instruction. Steps S308 and S309 are each similar to step S307.

[0082] (Steps S310 to S312) When the sink node 3 and each node 4 receive a measurement message from another node 4, they store in memory unit 13 and memory unit 23 data indicating the source node ID indicated in the received measurement message, the number of times each node has received the message, the average reception strength for each node, and the minimum reception strength for each node. The measurement message may include data indicating the maximum reception strength.

[0083] (Steps S313 to S315) Each node 4 transmits data to the sink node 3 indicating that the transmission of the measurement message has been completed.

[0084] (Step S316) The sink node 3 sends a measurement result request to the node 4-1. Steps S319 and S322 are each similar to step S316.

[0085] (Step S317) When the node 4-1 receives the measurement result request, the communication control unit 22 of the node 4-1 tally up the reception results of the measurement messages from each node 4. Step S320 is similar to step S317.

[0086] (Step S318) After tallying up the reception results of the measurement messages, the node 4-1 transmits a measurement result notification indicating the tally up reception results to the sink node 3. Steps S321 and S323 are each similar to step S318.

[0087] FIG. 22 is a diagram showing the data structure of a measurement result notification. The measurement result notification is data indicating each of the source node ID, destination node ID, and reception strength measurement result for each node 4. The source node ID is the same as the source node ID 151. The destination node ID is the same as the destination node ID 152. The data indicating the reception strength measurement result is data indicating each of the measurement result node ID, the number of times of reception, the average reception strength, and the minimum reception strength. The data indicating the reception strength measurement result may include data indicating the maximum reception strength. The measurement result node ID is the source node ID indicated in the measurement message received from another node 4. The reception strength measurement result for each node 4 is data acquired by receiving a measurement message from another node 4.

[0088] (Step S324) When the sink node 3 receives the measurement result notification from each node 4, it performs a counting process. 23 is a flowchart showing the specific processing of this step. The processing of this step will be explained using FIG.

[0089] (Step S351) The communication control unit 12 aggregates the measurement result notifications from each node 4, and based on the aggregation result, calculates the total number of problem nodes (hereinafter also referred to as the number of problem nodes) included in all nodes 4. The problem nodes are at least any of the nodes 4 whose average reception strength or minimum reception strength is below a specified value, the nodes 4 that cannot communicate directly with the sink node 3, and the nodes 4 whose reception count is below a specified value.

[0090] (Step S352) The communication control unit 12 determines whether the number of problem nodes is equal to or greater than the value of a predetermined variable w. If the number of problem nodes is equal to or greater than the value of the variable w, the communication control unit 12 proceeds to step S353, otherwise the communication control unit 12 ends the process.

[0091] (Step S353) The communication control unit 12 selects the forwarding nodes. Specifically, the communication control unit 12 uses the measurement results collected from each node 4 to select, among the nodes 4 whose number of receptions from the sink node 3 is equal to or greater than a specified value, one or more nodes 4 having the highest average reception strength between them and the problem node, as nodes for which the forwarding function is to be enabled.

[0092] (Step S325, Step S328, Step S331) The sink node 3 transmits a forwarding function control to each node 4. The forwarding function control indicates an instruction to enable or disable the forwarding function.

[0093] (Step S326) When the node 4-1 receives the transfer function control, the communication control unit 22 of the node 4-1 enables or disables the transfer function according to the instruction indicated by the received transfer function control. Step S329 is similar to step S326.

[0094] (Step S327) After setting the transfer function, the node 4-1 transmits a transfer function setting completion to the sink node 3, which indicates that the setting of the transfer function according to the received transfer function control has been completed. Steps S330 and S332 are similar to step S327.

[0095] Although the explanation is omitted, each node 4 that receives the message transmission instruction transmitted from the sink node 3 performs the same processing as that of the node 4-1.

[0096] 24 is a diagram illustrating an example of selection of a forwarding node in the sink node 3. In this example, the nodes 4-1, 4-2, and 4-3 are present within the communication range of the sink node 3. In this example, the problem node is a node 4 that has received a measurement message from the sink node 3 and whose reception count is equal to or less than the reception count threshold value 7. In this example, the node 4-3 is the problem node. Furthermore, the sink node 3 selects, as a target for enabling the forwarding function, the node 4 corresponding to the source node ID for which the node ID of the problem node exists in the measurement result node ID in the measurement result notification, and for which the corresponding number of receptions is equal to or greater than a specified value and the average reception strength corresponding to communication with the problem node is the highest. In this example, the node ID of the problem node exists in the measurement result node ID of each of node 4-1 and node 4-2, the number of receptions corresponding to each of node 4-1 and node 4-2 is equal to or greater than a specified value, and the average reception strength corresponding to node 4-2 is the highest among the average reception strengths corresponding to communication with the problem node. That is, in this example, node 4-2 is selected as a target for enabling the forwarding function. Through the above process, the sink node 3 can appropriately set the forwarding function for each node 4 that exists within the communication range of the sink node 3. When transmitting the forwarding function control, the sink node 3 may issue a control instruction to set the number of transmissions during forwarding to a predetermined value, rather than issuing a control instruction to disable the forwarding function.

[0097] ***Explanation of the effect of the fourth embodiment*** As described above, in this embodiment, the sink node 3 enables the forwarding function of the node 4 that can forward data transmitted by the problem node for each node 4 present within the communication range of the sink node 3. Therefore, according to this embodiment, even in a configuration in which the nodes 4 are densely packed in an area adjacent to the sink node 3, the forwarding function can be set to an appropriate node 4. Furthermore, according to this embodiment, even in a configuration in which the nodes 4 are densely packed within the communication range of the sink node 3, the number of times forwarding occurs until the forwarded data 150 reaches the destination node can be suppressed, thereby realizing communication with relatively high forwarding efficiency.

[0098] Furthermore, even if there are no problem nodes around the sink node 3, if nodes 4 with enabled forwarding functions are concentrated around the sink node 3, the amount of data per unit time will increase depending on the number of nodes, the transmission period, etc. Therefore, in this case, the data arrival rate may decrease due to an increased probability of collisions between data. On the other hand, according to this embodiment, by appropriately setting the forwarding function for each node 4, it is possible to reduce the number of forwarding occurrences and further improve the data arrival rate to the sink node 3.

[0099] ***Other embodiments*** The above-described embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. Furthermore, the embodiments are not limited to those described in the first to fourth embodiments, and various modifications are possible as necessary. The procedures explained using flowcharts and the like may be modified as appropriate. [Explanation of symbols]

[0100] 1,3 sink node, 2,4 node, 5,6 communication system, 11,21 transmitter / receiver unit, 12,22 communication control unit, 13,23 storage unit, 100 control circuit, 101 processor, 102 memory, 103 transmitter, 104 receiver, 108 processing circuit, 150 forwarded data, 151 source node ID, 152 destination node ID, 160 hop count information.

Claims

1. A communication system capable of constructing a multi-hop wireless communication network, comprising a sink node and a plurality of nodes, A target node which is each of the plurality of nodes is a communication control unit that, when receiving forwarded data that is data transmitted from a source node included in the plurality of nodes to the sink node and indicates an update value corresponding to a hop count from the source node to the target node, updates a first update value, which is the update value indicated by the received forwarded data, to a first update value after updating; a transmitting / receiving unit that transmits, when the post-update first update value has not reached a transfer end value, transfer data in which the first update value has been updated to the post-update first update value to a periphery of the target node; Equipped with a difference between the first update value and the updated first update value corresponds to one hop; an initial value of the update value indicated by the forwarded data received by the target node is a value corresponding to the number of hops from the source node to the sink node; A communication system in which a route for forwarding data received by the target node is not determined.

2. a communication control unit of the target node, when the target node receives a forwarding hop count signal, which is a signal transmitted from the sink node and indicates a second update value, which is an update value corresponding to the number of hops from the sink node to the target node, and an initial value of the second update value, calculates the number of hops from the target node to the sink node based on the second update value and the initial value indicated by the received forwarding hop count signal, stores the calculated number of hops as the minimum number of hops from the target node to the sink node, and updates the second update value indicated by the received forwarding hop count signal to the updated second update value; a difference between the second update value and the updated second update value corresponds to one hop; The minimum hop count is used as an initial value of an update value indicated by the first transmission data when the target node transmits the first transmission data to the sink node; The communication system described in claim 1, wherein the transceiver unit of the target node transmits a forwarding hop count signal in which the second update value has been updated to the post-update second update value to a vicinity of the target node when the post-update second update value has not reached the forwarding end value.

3. The communication system of claim 2, wherein when the forwarding hop number signal reaches the target node via multiple routes, the communication control unit of the target node stores, as the minimum hop number, the number of hops corresponding to the shortest route among the multiple routes whose corresponding reception strength is equal to or greater than a first reference reception strength.

4. A communication system as described in any one of claims 1 to 3, wherein the communication control unit of the target node increases each of the number of times the target node transmits the second transmission data and the number of times the target node transmits the forwarding data when the number of one or more nodes among the multiple nodes that are within the communication range of the target node and that can forward the second transmission data when transmitting the second transmission data from the target node to the sink node is less than or equal to a reference number of adjacent nodes.

5. A communication system as described in any one of claims 1 to 3, wherein the communication control unit of the target node controls the forwarding function of the target node based on the number of nodes among the plurality of nodes that are present within the communication range of the target node and the number of nodes among the plurality of nodes that are present within the communication range of the target node.

6. The communication system according to claim 5 , wherein the communication control unit of the target node controls the forwarding function of the target node by either disabling the forwarding function of the target node or setting the number of times the target node transmits the forwarded data.

7. The sink node: a communication control unit that, when a problem node that cannot communicate normally with the sink node exists among the nodes present within the communication range of the sink node among the plurality of nodes, selects a node as a selected node from among the nodes present within the communication range of the sink node according to a reception strength corresponding to communication between each node present within the communication range of the problem node and the problem node. Equipped with A communication system according to any one of claims 1 to 3, wherein the communication control unit of the selected node controls a forwarding function of the selected node so that the selected node can forward data transmitted by the problem node to the sink node.

8. The communication system according to claim 1 , wherein the communication control unit of the target node treats only nodes of the plurality of nodes whose corresponding reception strength is equal to or greater than a second reference reception strength as valid nodes.

9. A communication method executed in a communication system capable of constructing a multi-hop wireless communication network, the communication system including a sink node and a plurality of nodes, the method comprising: a computer provided in a target node which is each node of the plurality of nodes, when receiving transfer data which is data transmitted from a source node included in the plurality of nodes to the sink node and which is data indicating an update value corresponding to a hop count from the source node to the target node, updates a first update value which is an update value indicated by the received transfer data to a first update value after updating; When the post-update first update value has not reached a transfer end value, the computer transmits transfer data in which the first update value has been updated to the post-update first update value to a periphery of the target node; a difference between the first update value and the updated first update value corresponds to one hop; an initial value of the update value indicated by the forwarded data received by the target node is a value corresponding to the number of hops from the source node to the sink node; A communication method in which a route for forwarding data received by the target node is not determined.

10. In a communication system capable of constructing a multi-hop wireless communication network, the communication system includes a sink node and a plurality of nodes, and the plurality of nodes are provided with a target node, each of the plurality of nodes being a target node. The target node is provided with a communication program executed by the target node, the communication program comprising: a communication control process for updating a first update value, which is an update value indicated by the received forwarding data, to a first update value after updating when the target node receives forwarding data, the first update value being an update value indicated by the received ... a transmission / reception process of transmitting, to a periphery of the target node, transfer data in which the first update value has been updated to the post-update first update value when the post-update first update value has not reached a transfer end value; A communication program for causing the computer to execute the a difference between the first update value and the updated first update value corresponds to one hop; an initial value of the update value indicated by the forwarded data received by the target node is a value corresponding to the number of hops from the source node to the sink node; A communications program in which a route for forwarding data received by the target node is not determined.

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