Communication system, communication procedure and communication program

Abstract

A destination node, which is a node (2) included in a communication system comprising a sink node and a plurality of nodes (2), and capable of establishing a multi-hop wireless communication network, comprises a communication control unit (22) and a transmission and reception unit (21). Upon receiving transfer data transmitted from a source node (2) to the sink node and indicating an update value corresponding to a hop number from the source node to the destination node, the communication control unit (22) updates a first update value, which is the update value indicated by the received transfer data, to an updated first update value.If the updated first update value has not reached a transfer end value, the transmitting and receiving unit (21) transmits the transfer data in which the first update value has been updated to the updated first update value to an environment of the destination node. A difference between the first update value and the updated first update value corresponds to a single hop, and an initial value of the update value indicated by the transfer data is a value corresponding to a hop count from the source node to the sink node.

Description

Technical area

[0001] The present disclosure relates to a communication system, a communication method and a communication program. Background to the state of the art

[0002] Non-Patent Literature 1 discloses a transfer method called flooding. In flooding, after receiving data, each node transfers the data to other nodes within a communication range of that node. As the data is repeatedly transferred, the data eventually reaches its destination node. In this case, the parameters used in transfer control of flooding include the number of times data is transmitted from a respective node, the number of times data is transferred from a respective node, and a maximum hop count when data is transferred. Typically, data is transferred from a plurality of nodes. Even if the data is lost among some nodes, the data will reach a destination node provided that another node has received the data. Reference listNon-patent literature

[0003] Non-patent literature 1: “Mesh Profile,” Bluetooth SIG, 2019, v1.0.1, pp. 18-19 Summary of the inventionTechnical problem

[0004] In traditional flooding, the number of times a node transmits data, the number of times a node transmits the data, the maximum hop count for data transfer, and so on are preset parameters, and these parameter values ​​are set uniformly for all nodes according to the network size. However, a problem is that, depending on the configuration or size of a network, data can only be transferred efficiently if appropriate parameter values ​​are set for each node, resulting in a reduction in transfer efficiency across the entire network.

[0005] An object of the present disclosure is to improve the transfer efficiency in the entire network in a multi-hop wireless communication network by efficiently transferring the data from each node. Solution to the problem

[0006] A communication system according to the present disclosure comprises a sink node and a plurality of nodes, and the communication system is capable of establishing a multi-hop wireless communication network, wherein a destination node, which is a respective node of the plurality of nodes, comprises: a communication control unit for updating a first update value to an updated first update value after receiving the transfer data from a source node included in the plurality of nodes to the sink node and indicating an update value corresponding to a hop number from the source node to the destination node, wherein the first update value is the update value indicated by the received transfer data; and a transmission and reception unit for transmitting transfer data in which the first update value has been updated to the updated first update value to an environment of the destination node when the updated first update value has not reached a transfer end value, where a difference between the first update value and the updated first update value corresponds to a single hop, and wherein an initial value of the update value indicated by the transfer data is a value corresponding to a hop count from the source node to the sink node. Advantageous effects of the invention

[0007] According to the present disclosure, a communication control unit of a destination node included in a communication system capable of establishing a multi-hop wireless communication network updates a first update value, which is an update value indicated by received transfer data, to an updated first update value. If the updated first update value has not reached a transfer end value, a transmission and reception unit of the destination node transmits the transfer data in which the first update value has been updated to the updated first update value to the vicinity of the destination node.A difference between the first update value and the updated first update value corresponds to one hop, and an initial value of the update value specified by the transfer data is a value corresponding to the hop count from a source node to a sink node. Thus, according to the present disclosure, the maximum number of times the transfer data is transferred is a value corresponding to the hop count from the source node to the sink node.

[0008] Therefore, according to the present disclosure, in a multi-hop wireless communication network, it is possible to improve the transfer efficiency of the entire network by efficiently transferring data from each node. Brief description of the drawings Fig. 1 is a diagram showing an example of the configuration of a communication system 5 according to Embodiment 1. Fig. 2 is a diagram illustrating a structure of transfer data 150 according to Embodiment 1. Fig. 3 is a diagram illustrating an example of the functional configuration of the sink node 1 according to Embodiment 1. Fig. 4 is a diagram illustrating an example of the functional configuration of a node 2 according to Embodiment 1. Fig. 5 is a diagram illustrating an example of the hardware configuration of the sink node 1 according to Embodiment 1. Fig. 6 is a diagram explaining the operation of the communication system 5 according to a conventional technology. Fig. 7 is a flowchart illustrating a procedure for setting an initial value I according to Embodiment 1. Fig. 8 is a sequence diagram illustrating a flow for generating hop count information 160 according to Embodiment 1. Fig. 9 is a diagram describing transmission and reception of a transfer hop count signal according to Embodiment 1. Fig. 10 is a diagram illustrating the hop count information 160 according to Embodiment 1. Fig. 11 is a flowchart illustrating a procedure for setting the initial value I according to Embodiment 1. Fig. 12 is a diagram illustrating an example of the hardware configuration of the sink node 1 according to a variant of Embodiment 1. Fig. 13 is a sequence diagram illustrating a flow for setting the number of times to transmit according to Embodiment 2. Fig. 14 is a flowchart illustrating a process for setting the number of times to transmit according to Embodiment 2. Fig. 15 is a sequence diagram illustrating a flow of setting a transfer function according to Embodiment 3. Fig. 16 is a flowchart illustrating the process for setting the transfer function according to Embodiment 3. Fig. 17 is a diagram showing an example of the configuration of a communication system 6 according to Embodiment 4. Fig. 18 is a sequence diagram illustrating a flow of setting a transfer function according to Embodiment 4. Fig. 19 is a sequence diagram illustrating the flow of setting the transfer function according to Embodiment 4. Fig. 20 is a sequence diagram illustrating the flow of setting the transfer function according to Embodiment 4. Fig. 21 is a diagram illustrating a data structure of a message transmission instruction according to Embodiment 4. Fig. 22 is a diagram illustrating a data structure of a measurement result notification according to Embodiment 4. Fig. 23 is a flowchart illustrating aggregation processing according to Embodiment 4. Fig. 24 is a diagram illustrating an example of selection of a transfer node according to Embodiment 4. Description of embodiments

[0009] In the description and drawings of the embodiments, the same elements and corresponding elements are denoted by the same reference numerals. The description of elements denoted by the same reference numerals will be omitted or simplified as appropriate. Arrows in diagrams primarily indicate data flows or processing flows. Furthermore, "unit" may also be appropriately interpreted as "circuit," "step," "procedure," "process," or "circuitry." Embodiment 1.

[0010] This embodiment will be described below with reference to the drawings.

[0011] An object of Embodiment 1 is to improve the transfer efficiency of data transmitted from a respective node 2 to a sink node 1. *** Description of the configuration ***

[0012] Fig. 1 is a diagram illustrating an example of the configuration of a communication system 5 according to Embodiment 1. The communication system 5 includes the 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 an example of the plurality of nodes 2. The communication system 5 can establish a multi-hop wireless communication network.

[0013] Although in Fig. 1 shows one sink node 1 and 13 nodes 2, the number of sink nodes 1 and the number of nodes 2 are not limited to the Fig. 1. In the following, when a respective one of the plurality of nodes 2 is specified without distinguishing them individually, it is referred to as "node 2." The sink node 1 and the nodes 2 may be collectively referred to as "nodes."

[0014] Sink node 1 and a respective node 2 transmit and receive data (also referred to as signals or information in this specification) to and from each other. In particular, a respective node 2 frequently transmits data to sink node 1.

[0015] Fig. 2 is a diagram illustrating a 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, transmitted and received in each node 2, and indicating a source node identifier (ID) 151, a destination node ID 152, and an update value U.

[0016] The source node ID 151 is an ID indicating a source node, which is a source from which the transfer data 150 is transmitted. IDs are symbols used to identify the sink node 1 and a respective node 2.

[0017] The destination node ID 152 is an ID indicating a destination node that is a destination of the transfer data 150.

[0018] The update value U is an update value of an upper limit of a hop count and is a value indicating the maximum number of remaining hops allowed for the transfer data 150 to be transferred. The value of U is equal to an initial value I at the time the source node transmits the transfer data 150, and is decremented by one each time the sink node 1 or node 2 that received the transfer data 150 (hereinafter also referred to simply as the receiving node) transfers the transfer data 150. The initial value I indicates the initial value of the update value U and indicates the upper limit of the hop count. For the transfer data 150, a maximum of I hops is allowed from the source node.

[0019] Fig. 3 is a diagram illustrating an example of a functional configuration of the sink node 1. The sink node 1 includes a transmission and reception unit 11, a communication control unit 12, and a storage unit 13.

[0020] The transmitting and receiving unit 11 communicates data with a respective node 2. After receiving a signal from node 2, the transmitting and receiving unit 11 outputs the received signal to the communication control unit 12. The transmitting and receiving unit 11 also transmits the signal to node 2 based on an instruction from the communication control unit 12.

[0021] After receiving a signal from the transmitting and receiving unit 11, the communication control unit 12 performs predetermined processing based on the received signal.

[0022] The storage unit 13 stores data in a suitable manner which is necessary for the realization of the functions of the communication system 5.

[0023] Fig. 4 is a diagram illustrating an example of a functional configuration of the node 2. The sink node 2 includes a transmission and reception unit 21, a communication control unit 22, and a storage unit 23.

[0024] The transmitting and receiving unit 21 communicates data with the sink node 1 or node 2, each of which is another node in the multi-hop wireless communication network. Upon receiving a signal from another node, the transmitting and receiving unit 21 outputs the received signal to the communication control unit 22. The transmitting and receiving unit 21 also transmits the signal to the node based on an instruction from the communication control unit 22.

[0025] If an updated first update value (to be described later) has not reached a transfer end value, the transmission and reception unit 21 of a destination node, where the destination node is each node 2 of the plurality of nodes 2, transmits the transfer data 150 in which a first update value (to be described later) has been updated to the updated first update value to the vicinity of the destination node. As a concrete example, the transfer end value is 0. A difference between the first update value and the updated first update value corresponds to one hop. The initial value I, which is the initial value of the update value U indicated by the transfer data 150, corresponds to the hop count from the source node to the sink node 1.

[0026] If an updated second update value to be described later has not reached the transfer end value, the transmission and reception unit 21 of the destination node transmits a transfer hop number signal in which a second update value to be described later has been updated to the updated second update value, to the environment of the destination node.

[0027] After receiving a signal from the transmitting and receiving unit 21, the communication control unit 22 performs predetermined processing based on the received signal.

[0028] After receiving the transfer data 150, the communication control unit 22 of the destination node updates the first update value, which is the update value U indicated by the received transfer data 150, to the updated first update value. The transfer data 150 is data transmitted from the source node included in the plurality of nodes 2 to the sink node 1 and indicates the update value U. The update value U is a value corresponding to the hop count from the source node to the destination node.

[0029] When the destination node receives the transfer hop count signal, the communication control unit 22 of the destination node calculates a hop count from the destination node to the sink node 1 based on the second update value and the initial value indicated by the received transfer hop count signal, stores the calculated hop count as the minimum hop count from the destination node to the sink node 1, and updates the second update value indicated by the received transfer hop count signal to the updated second update value. The transfer hop count signal is a signal transmitted from the sink node 1 and indicates the second update value, which is the update value corresponding to the hop count from the sink node 1 to the destination node, and the initial value of the 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 transfer data when the destination node transmits the first transfer data to the sink node 1. If the transfer hop count signal has reached the destination node via a plurality of routes, the communication control unit 22 of the destination node may store, as the minimum hop count, a hop count corresponding to the shortest route among all routes whose reception strength is equal to or greater than a first reference reception strength among the plurality of routes. That is, the minimum hop count that the destination node stores is not limited to the actual minimum hop count from the sink node 1 to the destination node, but may be a hop count corresponding to the shortest route among the routes that can transfer data from the sink node 1 to the destination node or from the destination node to the sink node 1.The first reference reception strength can be specified in any way.

[0030] The communication control unit 22 of the destination node may treat only a respective node 2 whose corresponding reception strength is equal to or greater than a second reference reception strength among the plurality of nodes 2 as a valid node 2. That is, the communication control unit 22 of the destination node may ignore the node 2 whose corresponding reception strength is lower than the second reference reception strength. The second reference reception strength may be specified in any manner.

[0031] The storage unit 23 stores data in a suitable manner which is necessary for the realization of the functions of the communication system 5.

[0032] Fig. 5 is a diagram illustrating 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.

[0033] The control circuit 100 comprises a processor 101 and a memory 102.

[0034] Processor 101 is a processing circuit, such as a central processing unit (CPU) or a digital signal processor (DSP), that performs arithmetic operations. Control circuit 100 may include a plurality of processors as an alternative to processor 101. The plurality of processors share the role of processor 101.

[0035] The memory 102 is a storage device consisting of a random access memory (RAM), a read-only memory (ROM), and so on.

[0036] The functions of the individual units of sink node 1 are implemented by executing a communication program stored in memory 102 to implement the operation of sink node 1 in processor 101. The functions of the individual units of sink node 1 are implemented by software. The communication program can be recorded on a computer-readable, non-volatile recording medium. The non-volatile recording medium is, as a concrete example, an optical disk or a flash memory. The communication program can be provided as a program product.

[0037] The memory unit 13 is realized by the main memory 102.

[0038] The transmitter 103 is a device for transmitting data to the environment.

[0039] The receiver 104 is a device for receiving data from the environment. The transmission and reception unit 11 is implemented by the transmitter 103 and the receiver 104.

[0040] The hardware configuration of node 2 is essentially the same as the hardware configuration of sink node 1, so the description of the hardware configuration of node 2 is omitted. *** Description of how it works ***

[0041] A sequence of operations of the communication system 5 is equivalent to a communication method. A program that implements the operation of the communication system 5 is equivalent to the communication program.

[0042] Fig. 6 illustrates an example of processing for transmitting the transfer data 150 to the sink node 1 in the communication system 5 according to a conventional technology. Fig. Figure 6 illustrates data transfer routes in a case where data is transferred from node 2-1 to sink node 1. The transfer data 150 indicates the source node ID 151, the destination node ID 152, the initial value I, and the update value U, as described above. In this example, the source node ID 151 denotes the ID of node 2-1, and the destination node ID 152 denotes the ID of sink node 1.

[0043] Based on the destination node ID 152 and the update value U indicated by the transfer data 150 received from another node, each receiving node determines whether or not to transfer the received transfer data 150. Specifically, if the destination node ID 152 indicates a respective receiving node itself, each receiving node does not transfer the transfer data 150 because transfer is not required. If the result of decrementing the update value U by one has reached 0 or a certain value, each receiving node does not transfer the transfer data 150 because any further transfer is not permitted.

[0044] In the Fig. 6, the sink node 1 does not transfer any transfer destination data when receiving the transfer data 150 because the destination node ID 152 of the transfer data 150 indicates that the sink node 1 is the destination.

[0045] In the Fig. In the example shown in Figure 6, the initial value I is 5, each arrow represents a transfer of the transfer data 150, and the update value U at the time corresponding to each arrow is indicated for each arrow. As a concrete example, the update value U of the transfer data 150 transferred to node 2-12 is 1. Therefore, node 2-12 determines that a result of decrementing the update value U by one reaches the value 0, and thus does not transfer the transfer data 150. That is, in the example shown in Fig. In the example shown in Figure 6, the maximum number of hops is limited to five. Note that the update value U indicated by the transfer data 150 received from node 2-12 corresponds to the first update value, and the result of decrementing the update value U by one corresponds to the updated first update value. A difference between the first update value and the updated first update value corresponds to one hop.

[0046] In communication system 5, no transfer routes are specified. Therefore, even if the transfer data 150 indicates node 2-1 as the source node and sink node 1 as the destination node, the transfer route may randomly vary with each attempt to transmit the transfer data 150. As a concrete example, since the reception strength may vary with each attempt, and there may be a node 2 that is not capable of receiving (or conversely, capable of receiving) with each attempt, the formation of a transfer route may vary depending on whether the transfer data 150 can be received or not. Since the latency of a particular transfer route may vary with each attempt, a node that can initiate the transfer between neighboring nodes first may vary with each attempt. Consequently, a transfer direction may also vary with each attempt.

[0047] In a conventional multi-hop wireless communication network that uses flooding, the initial value I is set uniformly for each node 2 according to the size of the network. For this reason, when transmitting data from node 2 to a destination node with a relatively small minimum hop count 2, an unnecessary transfer may occur, such as a transfer via a route via nodes 2-7, as in the case shown in Fig. Example shown in Figure 6.

[0048] On the other hand, in this embodiment, in order to improve the transfer efficiency to the destination node, each node 2 maintains the hop count information 160 corresponding to each node 2, uses the hop count information 160 to appropriately set the initial value I when the transfer data 150 whose destination is the sink node 1 is to be transmitted, and then transmits the transfer data 150. The hop count information 160 corresponding to each node 2 is information indicating a hop count from each node 2 itself to each sink node 1. Therefore, according to this embodiment, it is possible to improve the transfer efficiency of the transfer data 150 whose destination is the sink node 1.

[0049] Fig. Figure 7 is a flowchart showing an example of a process for setting the initial value I in a respective node 2. Fig. 7 describes the process of determining the initial value I. In the following, it is assumed that there is a single sink node 1 in the communication system 5. If there are a plurality of sink nodes 1 in the communication system 5, the following processing is performed for each sink node 1. (Step S50)

[0050] The communication control unit 22 generates the hop count information 160 and proceeds to step S51. The hop count information 160 is information listing the minimum number of hops to reach the sink node 1 from the node 2 where the hop count information 160 was generated. Hereinafter, the minimum number of hops to the sink node 1 from the node 2 where the hop count information 160 is generated is also simply referred to as the hop count to the sink node 1. There may be a plurality of routes from a particular node 2 to a particular sink node 1. Specifically, there may be a plurality of routes in the transmission of one piece of the transfer data 150, and the route may vary when an attempt is made to transmit a new piece of the transfer data 150, as described above. In addition, the number of nodes between routes may not be the same.The hop count information 160 is essentially information that lists and retains a plurality of hop counts. Details of a process for generating the hop count information 160 will be described later. (Step S51)

[0051] The communication control unit 22 selects a hop count corresponding to the sink node 1 from the hop counts indicated by the generated hop count information 160 as the hop counts 1 for the sink node, and sets the selected hop count as the initial value I for the transfer data 150 when subsequently transmitting the transfer data 150 to the sink node 1. Details on how to set the initial value I will be explained later.

[0052] Fig. Fig. 8 is a sequence diagram illustrating an example of the process for generating the hop count information 160 in the communication system 5. Fig. 8 explains the process for generating the hop count information 160. (Step S1)

[0053] The sink node 1 transmits a transfer hop count signal, which is a signal for generating the hop count information 160.

[0054] Specifically, the communication control unit 12 generates the transfer hop count signal and transmits the generated transfer hop count signal to a group address or a unicast address via the transmitting and receiving unit 11. The transfer hop count signal includes the ID of the sink node 1 as the source node ID 151, the initial value I, and the update value U. At the time the sink node 1 transmits the transfer hop count signal, the initial value I and the update value U are the same value. (Step S2)

[0055] After receiving the transfer hop count signal, node 2-1 decrements the update value U indicated by the received transfer hop count signal by one and then transfers the received transfer hop count signal.

[0056] Specifically, after receiving the transfer hop count signal, the transmitting and receiving unit 21 first outputs the received transfer hop count signal to the communication control unit 22.

[0057] Next, the communication control unit 22 updates the update value U indicated by the transfer hop number signal received from the transmitting and receiving unit 21 to a value obtained by decrementing the update value U by one.

[0058] Next, the communication control unit 22 outputs the signal in which the update value U has been updated to the transmitting and receiving unit 21.

[0059] Next, the transmitting and receiving unit 21 transfers the signal received from the communication control unit 22 as the transfer hop number signal. (Step S3)

[0060] After receiving the transfer hop count signal, node 2-1 stores, in the storage unit 23, data indicating a hop count to sink node 1 and the average reception strength for each hop count. The transfer hop count signal can reach node 2-1 via a plurality of routes. When the transfer hop count signal reaches node 2-1 via a plurality of routes, node 2-1 stores data corresponding to each route of the plurality of routes in the storage unit 23. The average reception strength at a certain hop count in the destination node is an average value calculated when the destination node has received a destination signal a plurality of times via routes corresponding to this certain hop count, and is the average value of the reception strengths of the destination signal in the destination node.

[0061] Specifically, the communication control unit 22 first calculates the hop count from node 2-1 to sink node 1 using the initial value I and the update value U indicated by the transfer hop count signal received from the transmitting and receiving unit 21. The hop count from node 2 to sink node 1 is a value calculated by I - U + 1 [Formula 1].

[0062] Next, the communication control unit 22 stores data indicating the calculated hop count and the average reception strength for each hop count as the hop count information 160 in the storage unit 23. The hop count information 160 is information associating the hop count and the average reception strength corresponding to the hop count.

[0063] Step S4 is essentially the same as step S2, so no description is given.

[0064] Step S5 is essentially the same as step S3, so no description is given.

[0065] Then, although not shown in the figure, in each node 2 that has received the transfer hop count signal transmitted from another node 2, processing substantially similar to that of step S4 and step S5 is performed.

[0066] Fig. 9 is a diagram illustrating an example of transmission and reception of the transfer hop count signal according to Embodiment 1. Fig. Figure 9 illustrates an example where data transmitted from sink node 1 reaches node 2-1 via two routes. Specifically, the first route (denoted as route 1) is a route that leads directly from sink node 1 to node 2-1. The second route (denoted as route 2) traverses 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 the update value U at the time corresponding to each arrow is displayed near each arrow.

[0067] The update value U of the transfer hop count signal received by node 2-1 via route 1 is 5, so the hop count from sink node 1 to node 2-1 is 5 - 5 + 1 = 1 according to [Formula 1]. The update value U indicated by the transfer hop count signal received by node 2-1 via route 2 is 3, so the hop count from sink node 1 to node 2-1 is 5 - 3 + 1 = 3 according to [Formula 1].

[0068] Fig. 10 is a diagram illustrating an example of the hop count information 160 according to Embodiment 1. The hop count information 160 is information that associates a hop count from node 2 to sink node 1 with an average reception strength corresponding to the hop count. In the Fig. In the example shown in Figure 10, it is indicated that the hop count corresponding to route 1 is 1, and the average reception strength corresponding to route 1 is 30. It is further indicated that the hop count corresponding to route 2 is 3, and the average reception strength corresponding to route 2 is 50.

[0069] Fig. 11 is a flowchart showing an example of a process for setting the initial value I in node 2. Fig. 11 explains the process for determining the initial value I. (Step S21)

[0070] The communication control unit 22 sets 1 as the initial value of a variable h. (Step S22)

[0071] The communication control unit 22 determines whether the value of h matches any of the hop counts specified in the hop count information 160 stored in the storage unit 23. If the value of h matches any of the hop counts specified by the hop count information 160, the communication control unit 22 proceeds to step S24. In other cases, the communication control unit 22 proceeds to step S23. (Step S23)

[0072] The communication control unit 22 increments the value of h by one and repeats the processing from step S22. (Step S24)

[0073] The communication control unit 22 determines whether the average reception strength corresponding to the hop number equal to the value of h is equal to or greater than a predetermined value of a variable p.

[0074] If the average reception strength of this hop count is less than the value of the variable p (NO in step S24), the communication control unit 22 increments the value of h by one (step S23) and repeats the processing from step S22. If the average reception strength of this hop count is equal to or greater than the value of the variable p (YES in step S24), the communication control unit 22 proceeds to step S25. (Step S25)

[0075] The communication control unit 22 sets the value of h as the initial value I. That is, when each node 2 later acts as a data transmission source, it uses the value h calculated by itself through the above process as the initial value I.

[0076] As a concrete example, the Fig. In the example shown in Figure 10, when the value of variable p is 40, route 1 is not selected because the average reception strength corresponding to route 1 is smaller than the value of variable p, even though route 1 is a route with the smallest hop count. On the other hand, the hop count of route 2 (i.e., 3) is selected because the average reception strength corresponding to route 2 is greater than the value of variable p. Therefore, in node 2-1, the initial value I for the transfer data 150 addressed to sink node 1 is set to 3. If node 2-1 is a source node, the initial value I corresponds to the hop count from the source node to sink node 1.

[0077] Through the above processing, it is possible to select an appropriate hop count from the hop counts indicated by the hop count signals received from the node 2, and transmit the transfer data 150 in which the selected hop count is set as the initial value I. *** Description of the effects of Embodiment 1 ***

[0078] As described above, in this embodiment, each node 2 retains the hop count information 160 indicating the hop count from each node 2 itself to the sink node 1, uses the retained hop count information 160 to appropriately set the initial value I for the transfer data 150 addressed to the sink node 1, and then transmits the transfer data 150. This can prevent unnecessary transfer by other nodes 2 from being performed even when a transmission is performed from a node with a relatively small hop count to the destination node. In this way, communication with relatively high efficiency can be realized.

[0079] Each node 2 sets the initial value I for the transfer data 150 addressed to the sink node 1 using the hop count from each node 2 to the sink node 1. In this way, the initial value I for the transmission to the sink node 1, which accounts for a large part of the communication 5 performed in the communication system 5, can be appropriately set. As a result, the transfer efficiency of the communication system 5 as a whole can be improved.

[0080] Embodiment 1 introduced the methods for calculating the hop count using the sink node 1 as a base and for determining, for each node 2, the initial value I for data addressed to the sink node 1. However, this embodiment is not limited to this example, and the calculation of the hop count and the determination of the initial value I can be performed using any of the nodes 2 included in the communication system 5 as a base. *** Other configurations ***<Variante 1>

[0081] Fig. 12 is a diagram showing an example of a functional configuration of the sink node 1 according to this variant.

[0082] The sink node 1 includes a processing circuit 108 instead of the processor 101 or instead of the processor 101 and the memory 102.

[0083] The processing circuit 108 is a hardware that implements at least some of the units contained in the sink node 1.

[0084] The processing circuit 108 may be dedicated hardware or may be a processor that executes programs stored in the memory 102.

[0085] When the processing circuit 108 is dedicated hardware, a specific example of the processing circuit 108 is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof.

[0086] Sink node 1 may include a plurality of processing circuits as an alternative to processing circuit 108. The plurality of processing circuits share the role of processing circuit 108.

[0087] In the sink node 1, some functions can be realized by dedicated hardware and the remaining functions can be realized by software or firmware.

[0088] As a concrete example, the processing circuit 108 is implemented by hardware, software, firmware, or a combination thereof.

[0089] The processor 101, the main memory 102, and the processing circuit 108 are collectively referred to as the "processing circuit." This means that the functions of a respective functional component of the sink node 1 are implemented by the processing circuit.

[0090] The sink node 1 according to other embodiments may have substantially the same configuration as that of this variant. Embodiment 2.

[0091] Differences from the embodiments described above will be described below mainly with reference to the drawings. *** Description of the configuration ***

[0092] The configurations according to this embodiment are substantially the same as the configurations according to Embodiment 1.

[0093] If the number of one or more nodes 2 among the plurality of nodes 2 that are within a communication range of the destination node and can transfer second transmission data when the second transmission data is transmitted from the destination node to the sink node 1 is equal to or less than a neighboring node reference number, the communication control unit 22 of the destination node increases the number of times the destination node transmits the second transmission data and the number of times the destination node transmits transfer data. The neighboring node reference number can be specified in any way. *** Description of how it works ***

[0094] The following mainly explains differences from Embodiment 1. In Embodiment 2, the process until the hop count information is generated by each node 2 is essentially the same as that in Embodiment 1.

[0095] Fig. Figure 13 is a sequence diagram showing an example of a process for determining the number of times to transmit in node 2. Fig. 13 explains the process for determining the number of times to transfer. (Step S101)

[0096] The node 2-1 stores data indicating the hop count calculated in the method for setting the initial value I according to Embodiment 1 in the storage unit 23.

[0097] Step S102 is essentially the same as step S101. (Step S103)

[0098] Node 2-1 transmits a minimum hop count signal containing information indicating the minimum hop count from sink node 1 to node 2-1 to a respective neighbor node corresponding to node 2-1. A respective neighbor node corresponding to the destination node is a respective node 2 with which the destination node can communicate.

[0099] Step S104 is essentially the same as step S103. (Step S105)

[0100] After receiving the minimum hop count signal, node 2-1 stores data indicating a source node ID, a receiving node count for each hop count, and an average reception strength for each hop count, which are indicated by the received minimum hop count signal, in storage unit 23. The source node ID is substantially equal to source node ID 151.

[0101] Step S106 is essentially the same as step S105.

[0102] Then, although not shown in the figure, each node 2 that has received the minimum hop count signal transferred from another node 2 performs the processing indicated in step S101, step S103, and step S105, like the node 2-1.

[0103] Fig. Figure 14 is a flowchart showing an example of the process for determining the number of times to transmit in the destination node, which is node 2. Fig. 14 explains the process for determining the number of times to transmit. (Step S121)

[0104] The communication control unit 22 counts first neighboring nodes corresponding to the destination node in terms of the minimum hop count and calculates the total number of first neighboring nodes. The first neighboring nodes corresponding to the destination node are composed of a respective neighboring node whose minimum hop count is equal to the minimum hop count of the destination node and a respective neighboring node whose minimum hop count is one less than the minimum hop count of the destination node. A first neighboring node is node 2, which acts as a transfer node when the transfer data 150 is transmitted from the destination node to the sink node 1. That is, a first neighboring node is node 2, which is within the communication range of the destination node and can transfer second transmission data when the second transmission data is transmitted from the destination node to the sink node 1.

[0105] Note that in step S121, only one node 2 can be counted whose average reception strength exceeds a predetermined threshold. This allows the number of first neighboring nodes that can communicate correctly and are essentially valid to be calculated. (Step S122)

[0106] The communication control unit 22 determines whether the total number of nodes calculated in step S121 is equal to or less than a predetermined value of a variable j.

[0107] If the total number of nodes exceeds the value of variable j, the communication control unit 22 terminates the processing. In other cases, the communication control unit 22 proceeds to step S126. (Step S123)

[0108] The communication control unit 22 increases the number of times of transmission in the initial transmission and the number of times of transmission in transfer to a predetermined value.

[0109] The processing described above makes it possible to appropriately increase the number of times of transmission only to each node 2 with a relatively small number of first neighbor nodes acting as transfer nodes when the transfer data 150 is transmitted to the sink node 1. *** Description of the effects of embodiment 2 ***

[0110] As explained above, in this embodiment, node 2 appropriately increases the number of transmissions to only each node 2 with a relatively small number of first neighbor nodes. Consequently, even with a small number of first neighbor nodes, data is more likely to be transmitted between neighboring nodes, so that communication with relatively high transfer efficiency can be realized. Embodiment 3.

[0111] Differences from the embodiments explained above are explained below mainly with reference to the drawings. *** Description of the configuration ***

[0112] The configurations according to this embodiment are substantially the same as the configurations according to Embodiment 1.

[0113] The communication control unit 22 of the destination node performs control of the transfer function of the destination node depending on the number of nodes 2 located within the communication range of the destination node among the plurality of nodes 2 and the number of nodes 2 located within the communication range of each node 2 located within the communication range of the destination node among the plurality of nodes 2. The communication control unit 22 of the destination node may, as the control of the transfer function of the destination node, perform one of disabling the transfer function of the destination node and determining the number of times the destination node transmits the transfer data 150. *** Description of how it works ***

[0114] The following mainly explains differences from embodiment 1.

[0115] Fig. Figure 15 is a sequence diagram showing an example of a process for determining the transfer function in node 2. Fig. 15 explains the process for determining the transfer function. (Step S201)

[0116] The sink node 1 transmits a neighbor node count check signal to a respective neighbor node. (Step S202)

[0117] The sink node 2-1 transmits a neighbor node count check signal to a respective neighbor node.

[0118] Step S203 is essentially the same as step S202. (Step S204)

[0119] After receiving each neighboring node number check signal, node 2-1 stores in storage unit 23 data indicating the source node ID and average reception strength of each node 2 indicated by each neighboring node number check signal, as well as the number of neighboring nodes that transmitted each neighboring node number check signal received by node 2-1. The source node ID is substantially equal to source node ID 151.

[0120] Step S205 is essentially the same as step S204. (Step S206)

[0121] Node 2-1 transmits a neighbor node count notification signal containing information indicating a neighbor node count corresponding to Node 2-1 to a respective neighbor node.

[0122] Step S207 is essentially the same as step S206. (Step S208)

[0123] After receiving the neighbor node notification signal, the node 2-1 stores data indicating the source node ID, the average reception strength of each node 2, and the neighbor node number of each node 2 indicated by the received neighbor node notification signal in the storage unit 23.

[0124] Step S209 is essentially the same as step S208.

[0125] Then, although not shown in the figure, each node 2 that has received the neighbor node notification signal from another node 2 performs the processing indicated in step S204, step S206, and step S208, like the node 2-1.

[0126] Fig. Figure 16 is a flowchart showing an example of the process for determining the transfer function in the destination node, which is node 2. Fig. 16 explains the process for determining the transfer function. (Step S221)

[0127] The communication control unit 22 determines whether or not a respective neighboring node number corresponding to a respective node 2 is equal to or greater than a predetermined value of a variable f.

[0128] If the number of neighboring nodes corresponding to any node 2 is less than the value of the variable f, the communication control unit 22 terminates the processing. In other cases, the communication control unit 22 proceeds to step S222. (Step S222)

[0129] The communication control unit 22 determines whether the average reception strength of each neighboring node of the destination node is equal to or greater than a predetermined value of a variable g.

[0130] If the average reception strength of a neighboring node is less than the value of the variable g, the communication control unit 22 terminates the processing. In other cases, the communication control unit 22 proceeds to step S223. (Step S223)

[0131] The communication control unit 22 determines whether the destination node is the only node 2 with the largest number of neighbor nodes among each neighbor node and the destination node.

[0132] If the destination node is the only node 2 with the largest number of neighboring nodes, the communication control unit 22 proceeds to step S225. In other cases, the information processing device 22 proceeds to step S224. (Step S224)

[0133] The communication control unit 22 determines whether or not there is any node 2 whose transfer function is to be deactivated based on a predetermined setting condition. As a concrete example, the setting condition specifies that a certain number of nodes 2 are selected in ascending order of the node ID values ​​and the transfer function of each selected node 2 is deactivated, that a certain number of node IDs are randomly selected and the transfer function of each selected node 2 is deactivated, or that the transfer function of each node 2 is deactivated after a random period of time has elapsed.

[0134] If the determination condition is met, that is, if there is any Node 2 whose transfer function is to be deactivated, the communication control unit 22 proceeds to step S225. In other cases, the communication control unit 22 terminates the processing. Note that the communication control unit 22 deactivates the transfer function of each Node 2 whose transfer function is not to be deactivated. (Step S225)

[0135] The communication control unit 22 deactivates the transfer function of the destination node. Furthermore, if the communication control unit 22 determines that there is any node 2 whose transfer function is to be deactivated in step S224, it deactivates the transfer function of each node 2 whose transfer function is to be deactivated according to the determination condition.

[0136] A node whose transfer function has been disabled transmits a disabled transfer function notification signal to each neighboring node to notify that its transfer function has been disabled. Upon receiving the disabled transfer function notification signal, Node 2 deletes data indicating the source node ID, the average reception strength of each Node 2, and the neighboring node count corresponding to each Node 2, which correspond to the received disabled transfer notification signal, from the storage unit 23 of Node 2. Each Node 2, except for Node 2 whose transfer function has been disabled, repeats processing from the transmission and reception of the neighboring node count check signal.

[0137] Through the above processing, node 2 can find out the neighbor node number corresponding to each neighbor node and then enable or disable the transfer function.

[0138] If the transfer function is to be disabled, the destination node can change the number of times of transmission by the destination node during transfer to a predetermined value instead of disabling the transfer function. *** Description of the effects of embodiment 3 ***

[0139] As described above, in this embodiment, each node 2 determines the neighboring node number corresponding to each neighboring node, and then enables or disables the transfer function of each node 2. Consequently, it is possible to reduce the number of transfers before the transfer data 150 reaches the destination node, even when neighboring nodes are densely arranged around each node 2. Thus, communication with relatively high transfer efficiency can be realized. Embodiment 4.

[0140] Differences from the embodiments explained above are explained below mainly with reference to the drawings. *** Description of the configuration ***

[0141] Fig. 17 is a diagram illustrating an example of the configuration of a communication system 6 according to Embodiment 4. The communication system 6 includes the 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 the nodes 4-1 to 4-6, which are an example of the plurality of nodes 4 in the vicinity. The communication system 6 can establish a multi-hop wireless communication network.

[0142] In Fig. 17 shows a single sink node and six nodes 4, but the number of sink nodes 3 and the number of nodes 4 are not limited to the Fig. 17. Hereinafter, when a respective one of the plurality of nodes 4 is referred to without distinguishing them individually, it will be referred to as "node 4." Furthermore, the sink node 3 and the node 4 may be collectively referred to as the "node."

[0143] The configuration of sink node 3 is essentially the same as the configuration of sink node 1.

[0144] The configuration of sink node 4 is essentially the same as the configuration of node 2.

[0145] If a problem node exists among the plurality of nodes 4, the communication control unit 12 of the sink node 3 selects a node 4 as a selected node from among the respective nodes 4 located within the communication range of the problem node, based on the reception strength corresponding to communication between the problem node and the respective node 4 located within the communication range of the problem node. The problem node is the node 4 that cannot communicate properly with the sink node 3.

[0146] The communication control unit 22 of the selected node controls the transfer function of the selected node so that data transmitted from the problem node to the sink node 3 can be transferred. *** Description of how it works ***

[0147] The Fig. 18 to 20 are sequence diagrams showing an example of a process for determining the transfer function in node 4. Based on the Fig. The process for determining the transfer function is explained in Figures 18 to 20. Note that in this example, each participating node 4 is the node 4 that is within the communication range of the sink node 3. (Step S301)

[0148] The sink node 3 transmits a message transmission instruction a certain number of times to a respective node 4.

[0149] Fig. Figure 21 is a diagram illustrating a data structure of a message transmission instruction. The message transmission instruction is data containing information about a source node ID, a destination node ID, and the number of times a measurement message is transmitted.

[0150] The source node ID is essentially the same as source node ID 151.

[0151] The destination node ID is essentially the same as destination node ID 152.

[0152] The number of times of transmission of the measurement message is the number of times of transmission of the measurement message to a respective neighbor node.

[0153] Step S303 and step S305 are essentially the same as step S301. (Step S302)

[0154] After receiving the message transmission instruction, node 4-1 transmits a message transmission acknowledgment indicating that the message transmission instruction has been received to sink node 3.

[0155] Step S304 and step S306 are essentially the same as step S302. (Step S307)

[0156] The node 4-1 repeatedly transmits the measurement message to each neighboring node, with the number of times as specified by the number of times of transmission of the measurement message specified in the received message transmission instruction.

[0157] Step S308 and step S309 are essentially the same as step S307. (Step S310 to Step S312)

[0158] After receiving the measurement message from another node 4, the sink node 3 and a respective node 4 store data indicating a source node ID, a reception count of a respective node, an average reception strength of a respective node, and a minimum reception strength of a respective node indicated by the received measurement message in the storage unit 13 and the storage unit 23, respectively.

[0159] It should be noted that the measurement message may also contain data indicating a maximum reception strength. (Step S313 to Step S315)

[0160] A respective node 4 transmits data indicating that the transmission of the measurement message to the sink node 3 has been completed. (Step S316)

[0161] Sink node 3 transmits a measurement result request to node 4-1.

[0162] Steps S319 and S322 are essentially the same as step S316. (Step S317)

[0163] When the node 4-1 receives the measurement result request, the communication control unit 22 of the node 4-1 aggregates the measurement message reception results from each node 4.

[0164] Step S320 is essentially the same as step S317. (Step S318)

[0165] After aggregating the measurement message reception results, the node 4-1 transmits a measurement result notification indicating the aggregated reception results to the sink node 3.

[0166] Steps S321 and S323 are essentially the same as step S318.

[0167] Fig. 22 is a diagram illustrating a data structure of the measurement result notification. The measurement result notification is data indicating a source node ID, a destination node ID, and a reception strength measurement result for each node 4. The source node ID is substantially equal to the source node ID 151. The destination node ID is substantially equal to the destination node ID 152. The data indicating the reception strength measurement result is data indicating a measurement result node ID, a reception count, an average reception strength, and a minimum reception strength. The data indicating the reception strength measurement result may include data indicating a maximum reception strength. The measurement result node ID is the source node ID specified in the measurement message received from another node 4.The reception strength measurement result for a respective node 4 is data obtained by receiving the measurement message from another node 4. (Step S324)

[0168] Upon receiving the measurement result notification from a respective node 4, the sink node 3 performs aggregation processing.

[0169] Fig. Figure 23 is a flowchart illustrating specific processing in this step. Fig. 23 explains the processing of this step. (Step S351)

[0170] The communication control unit 12 aggregates the measurement result notifications from each node 4 and, based on the aggregated results, calculates a total value for the number of problem nodes included in all nodes 4 (hereinafter also referred to as the problem node count). A problem node is at least one of the node 4 whose average reception strength or minimum reception strength is equal to or less than a specified value, the node 4 that cannot communicate directly with the sink node 3, and the node 4 whose reception count is equal to or less than a specified value. (Step S352)

[0171] The communication control unit 12 determines whether the problem node number is equal to or greater than a predetermined value of a variable w.

[0172] 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. In other cases, the communication control unit 12 terminates the processing. (Step S353)

[0173] The communication control unit 12 selects a transfer node. Specifically, using the measurement results collected from each node 4, the communication control unit 12 selects one or more nodes 4 with the highest average reception strength relative to the problem node among each node 4 whose reception count from the sink node 3 is equal to or greater than a specified value as a target or targets whose transfer function is to be activated. (Step S325, Step S328 and Step S331)

[0174] The sink node 3 transmits a transfer function to a respective node 4. The transfer function control gives an instruction to activate or deactivate the transfer function. (Step S326)

[0175] 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.

[0176] Step S329 is essentially the same as step S326. (Step S327)

[0177] After setting the transfer function, the node 4-1 transmits a transfer function setting completion indicating completion of setting the transfer function to the sink node 3 according to the received transfer function control.

[0178] Steps S330 and S332 are essentially the same as step S327.

[0179] Subsequently, in each node 4 which has received the message transmission instruction from the sink node 3, processing is performed which is substantially the same as the processing in the node 4-1, although a description is omitted.

[0180] Fig. 24 is a diagram illustrating an example of selecting a transfer node in sink node 3. In this example, nodes 4-1, 4-2, and 4-3 are within the communication range of sink node 3.

[0181] In this example, among the nodes 4 that received the measurement message from sink node 3, the node 4 whose reception count is equal to or less than a reception count threshold of 7 is treated as the problem node. In this example, node 4-3 is the problem node.

[0182] Sink node 3 selects node 4, which corresponds to a source node ID with a reception count greater than or equal to a specified value and the highest average reception strength corresponding to communication with the problem node, among the source node IDs whose measurement notification includes the node ID of the problem node as the measurement result node ID, as the target whose transfer function is to be activated. In this example, the node ID of the problem node is included in the measurement result node IDs of node 401 and node 402. The reception counts corresponding to node 4-1 and node 4-2 are equal to or greater than the specified value. Regarding the average reception strength corresponding to communication with the problem node, the average reception strength of node 4-2 is the highest.That is, node 4-2 is selected as the destination whose transfer function is to be activated in this example.

[0183] Through the above processing, the sink node 3 can appropriately set the transfer function for each node 4 located within the communication range of the sink node 3.

[0184] It should be noted that when transferring the transfer function control, the sink node 3 may instruct control to set the number of times of transmission upon transfer to a predetermined value, instead of instructing control to disable the transfer function. *** Description of the effects of embodiment 4 ***

[0185] As described above, in this embodiment, the sink node 3 activates the transfer function of the node 4 capable of transferring data transmitted from the problem node, with respect to each node 4 located within the communication range of the sink node 3. Therefore, according to this embodiment, even in a configuration where the nodes 4 are densely arranged in an area around the sink node 3, it is possible to set the transfer function for an appropriate node 4. Furthermore, according to this embodiment, even when the nodes 4 are densely arranged within the communication range of the sink node 3, it is possible to reduce the number of transfers until the transfer data 150 reaches the destination node. Thus, communication with relatively high transfer efficiency can be realized.

[0186] Furthermore, even in a case where there is no problem node in the vicinity of the sink node 3, if the nodes 4 with the transfer function enabled are densely arranged around the sink node 3, the amount of data per unit time may increase depending on the number of nodes, the transmission time, and so on. Therefore, in this case, the data arrival rate may be reduced due to an increased probability of data collisions. On the other hand, in this embodiment, by appropriately setting the transfer function for each node 4, the number of successful transfers can be reduced and, furthermore, the data arrival rate at the sink node 3 can be improved. *** Further embodiments ***

[0187] The above-described embodiments can be freely combined, or any components of a respective embodiment can be modified. Alternatively, any component can be omitted from a respective embodiment.

[0188] The embodiments are not limited to those illustrated in Embodiments 1 and 4, and various changes can be made as needed. The processes explained using flowcharts or the like can be appropriately changed. List of reference symbols

[0189] 1, 3: Sink node; 2, 4: Node; 5, 6: Communication system; 11, 21: Transmitting and receiving 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: Transfer data; 151: Source node ID; 152: Destination node ID; 160: Hop count information.

Claims

[1] A communication system comprising a sink node and a plurality of nodes, the communication system being capable of establishing a multi-hop wireless communication network, wherein a target node, which is a respective node of the plurality of nodes, comprises: a communication control unit for updating a first update value to an updated first update value upon receiving transfer data transmitted from a source node included in the plurality of nodes to the sink node and indicating an update value corresponding to a hop number from the source node to the destination node, wherein the first update value is the update value indicated by the received transfer data; and a transmission and reception unit for transmitting transfer data in which the first update value has been updated to the updated first update value to an environment of the destination node when the updated first update value has not reached a transfer end value, where a difference between the first update value and the updated first update value corresponds to a single hop, and wherein an initial value of the update value indicated by the transfer data is a value corresponding to a hop count from the source node to the sink node. [2] Communication system according to claim 1, wherein, when the destination node receives a transfer hop count signal transmitted from the sink node and indicating a second update value, which is an update value corresponding to a hop count from the sink node to the destination node, and an initial value of the second update value, the communication control unit of the destination node calculates a hop count from the destination node to the sink node based on the second update value and the initial value indicated by the received transfer hop count signal, stores the calculated hop count as a minimum hop count from the destination node to the sink node, and updates the second update value indicated by the received transfer hop count signal to an updated second update value, where a difference between the second update value and the updated second update value corresponds to a single hop, wherein the minimum hop count is used as an initial value of an update value indicated by first transmission data when the destination node transmits the first transmission data to the sink node, and wherein, when the updated second update value has not reached the transfer end value, the transmitting and receiving unit of the destination node transmits a transfer hop count signal in which the second update value has been updated to the updated second update value to an environment of the destination node. [3] The communication system according to claim 2, wherein, when the transfer hop count signal has reached the destination node via a plurality of routes, the communication control unit of the destination node stores, as the minimum hop count, a hop count corresponding to a shortest route among each route whose corresponding reception strength is equal to or greater than a first reference reception strength among the plurality of routes. [4] The communication system according to any one of claims 1 to 3, wherein, when a number of one or more nodes among the plurality of nodes that are within a communication range of the destination node and can transfer second transmission data when the second transmission data is transmitted from the destination node to the sink node is equal to or less than a neighboring node reference number, the communication control unit of the destination node increases the number of times of transmission of the second transmission data by the destination node and the number of times of transmission of the transfer data by the destination node. [5] The communication system according to any one of claims 1 to 4, wherein the communication control unit of the destination node performs control of a transfer function of the destination node depending on a number of nodes among the plurality of nodes that are within a communication range of the destination node and a number of nodes among the plurality of nodes that are within a communication range of each node that is within the communication range of the destination node. [6] The communication system according to claim 5, wherein the communication control unit of the destination node performs, as the control of the transfer function of the destination node, one of deactivating the transfer function of the destination node and setting the number of times of transmission of the transfer data by the destination node. [7] Communication system according to one of claims 1 to 6, wherein the sink node comprises: a communication control unit for selecting a node as a selected node when there is a problem node that cannot properly communicate with the sink node among a respective node that is within a communication range of the sink node among the plurality of nodes, wherein the selected node is selected from a respective node that is within a communication range of the problem node among a respective node that is within the communication range of the sink node, based on a reception strength corresponding to communication between a respective node that is within the communication range of the problem node and the problem node, and wherein a communication control unit of the selected node controls a transfer function of the selected node to activate a transfer of data transmitted from the problem node to the sink node. [8] The communication system according to any one of claims 1 to 7, wherein the communication control unit of the destination node treats only a node whose corresponding reception strength is equal to or greater than a second reference reception strength among the plurality of nodes as a valid node. [9] A communication method carried out in a communication system comprising a sink node and a plurality of nodes and capable of establishing a multi-hop wireless communication network, the communication method comprising: Updating a first update value to an updated first update value after receiving transfer data transmitted from a source node included in the plurality of nodes to the sink node and indicating an update value corresponding to a hop count from the source node to the destination node, the first update value being the update value indicated by the received transfer data, by a computer included in a destination node that is a respective node of the plurality of nodes; and Transferring transfer data in which the first update value has been updated to the updated first update value to an environment of the target node if the updated first update value has not reached a transfer end value, by the computer, where a difference between the first update value and the updated first update value corresponds to a single hop, and wherein an initial value of the update value indicated by the transfer data is a value corresponding to a hop count from the source node to the sink node. [10] A communication program executed in a communication system comprising a sink node and a plurality of nodes and capable of establishing a multi-hop wireless communication network by a computer included in a destination node that is a respective node of the plurality of destination nodes, the communication program causing the computer to execute: a communication control process of updating a first update value to an updated first update value when the destination node receives transfer data transmitted from a source node included in the plurality of nodes to the sink node and indicating an update value corresponding to a hop number from the source node to the destination node, the first update value being the update value indicated by the received transfer data; and a transmission and reception process of transmitting transfer data in which the first update value has been updated to the updated first update value to an environment of the destination node when the updated first update value has not reached a transfer end value, where a difference between the first update value and the updated first update value corresponds to a single hop, and wherein an initial value of the update value indicated by the transfer data is a value corresponding to a hop count from the source node to the sink node.

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