JPWO2018143094A1 - Wireless communication system management node and wireless communication system - Google Patents

Abstract

A management node of a wireless communication system configured by a plurality of communication nodes that operate by switching between a first mode that does not relay data and a second mode that relays data according to an instruction, from the management node When communication nodes with a wireless communication distance of up to n hops (n is a natural number) are identified, among the communication nodes with a wireless communication distance of n hops, the largest number of communications not included in the specified communication node A communication node capable of directly communicating with the node (S14, S15) is instructed to operate in the second mode (S17).

Description

  The present invention relates to a management node of a wireless communication system constituted by a plurality of communication nodes and a wireless communication system.

  Conventionally, there is a wireless communication system including a plurality of communication nodes (for example, Patent Document 1). The wireless communication system of Patent Document 1 is composed of two or more nodes. The wireless communication system includes a management node (coordinator) that manages the wireless communication system. For each relay node (coordinator or router) that transfers data to other nodes in the wireless communication system, the management node sets a group composed of nodes that communicate directly with the relay node. Get the communication strength at each node. The management node reconfigures the network by changing the function to a relay node to a node of a specific group to which a node whose communication strength acquired by the acquisition unit is below a predetermined strength among nodes of the wireless communication system belongs Output instructions.

  In this specification, in accordance with the designation in the ZigBee (registered trademark) standard, an end point wireless node that operates as a sensor or an actuator is referred to as an end device, a wireless node that relays information is referred to as a router, and a wireless node that aggregates information is referred to as a coordinator. .

JP 2014-86776 A

  In a general wireless communication system as well as the wireless communication system disclosed in Patent Document 1, the receivable distance is limited for wireless communication transmitted from an end device. For this reason, in order to receive communication from an end device arranged in a place where the coordinator cannot receive directly, it is necessary to arrange a router between the end device and the coordinator.

  In the past, routers were generally set manually, but because the receivable distance depends on the environment, such as the presence or absence of obstacles, it is difficult to determine the appropriate location and number of routers. Know-how is required. Further, since the router is accompanied by a transfer operation, the power consumption increases, so it is desirable to reduce it as much as possible. In particular, when the wireless node is battery-powered, the router has a short life, and it is desirable for the management and maintenance to reduce the number of routers.

  Therefore, the present invention provides a management node that automatically configures a wireless communication system having as few routers as possible and having an optimized arrangement location and number of routers, and a wireless communication system including such a management node. The purpose is to do.

  In order to achieve the above object, a management node of a wireless communication system according to an aspect of the present invention operates by switching between a first mode in which data is not relayed and a second mode in which data is relayed according to an instruction. When a management node of a wireless communication system composed of a plurality of communication nodes and a communication node having a wireless communication distance of up to n hops (n is a natural number) from the management node is known, the wireless communication distance is n A communication node that can directly communicate with the largest number of communication nodes that are not included in the communication node whose wireless communication distance is known among the communication nodes that are hops is instructed to operate in the second mode.

  According to this configuration, when the communication nodes in the wireless communication distance from the coordinator to n hops are known, the wireless communication distance is not yet known (in other words, the largest number of communication nodes that are not connected to the network). A communication node that can directly communicate with the router is set in the router. The router to be set is connected to the wireless communication system as a communication node having a wireless communication distance of n + 1 hops as the maximum number of communication nodes, so that it has as few routers as possible, and the location and number of routers are optimized. A wireless communication system can be automatically configured.

  In addition, the management node performs a first process of classifying a communication node capable of directly communicating with the management node as a communication node having a radio communication distance of 1 hop, and then the radio communication distance is classified. Of the first communication nodes that are one or more communication nodes having the maximum number of hops, the second communication node that is capable of directly communicating with the largest number of second communication nodes that have not yet been classified in the wireless communication distance is the second communication node. A second process of classifying the largest number of the second communication nodes as a communication node having a hop number greater than the hop number of the first communication node. It may be executed until there are no communication nodes whose distances are not classified.

  According to this configuration, by repeating the above-described processing, the largest number of communication nodes are connected to the wireless communication system for each wireless communication distance. An optimized wireless communication system can be configured automatically.

  Further, the management node transmits a beacon signal in the first process, classifies the communication node responding to the beacon signal as a communication node having a wireless communication distance of 1 hop, and in the second process, the 1 The first communication node is instructed to transmit a beacon signal, the list information of communication nodes responding to the beacon signal is obtained from each of the one or more first communication nodes, and is included in the list information and wireless The first communication node having the largest number of communication nodes whose communication distances are not yet classified may be instructed to operate in the second mode.

  According to this configuration, whether or not direct communication is possible can be specified by a beacon signal, and therefore an appropriate communication node reflecting the propagation situation in the field is set as a router. Therefore, for example, significant automation and labor saving are achieved as compared with the operation of setting the router while manually measuring the propagation state.

  In addition, when there are a plurality of the first communication nodes, the management node instructs the one first communication node to transmit a beacon signal, and then sends a response signal to the beacon signal to the one first communication node. May be instructed to transmit a beacon signal to another first communication node.

  According to this configuration, since beacon signals are transmitted and response signals are received sequentially for each communication node, radio signal congestion is less likely to occur.

  In addition, when there are a plurality of the first communication nodes, the management node instructs the one first communication node to transmit a beacon signal, and then sends a response signal to the beacon signal to the one first communication node. Before receiving from, the other first communication node may be instructed to transmit a beacon signal.

  According to this configuration, since transmission of a beacon signal and reception of a response signal are performed in parallel by a plurality of communication nodes, it is easy to shorten the time required for signal transmission / reception.

  In addition, when a predetermined condition is satisfied, the management node may redo the process of instructing the second mode after setting the plurality of communication nodes to the first mode.

  According to this configuration, when the routing once set does not function due to a failure of the communication node, the routing can be redone.

  A wireless communication system according to an aspect of the present invention includes a plurality of communication nodes that operate by switching between a first mode that does not relay data and a second mode that relays data according to an instruction, The aforementioned management node that instructs at least one of the communication nodes to operate in the second mode.

  According to this configuration, the management node connects the largest number of communication nodes to the wireless communication system for each wireless communication distance, thereby having as few routers as possible and optimizing the placement location and number of routers. A wireless communication system can be automatically configured.

  Each of the plurality of communication nodes is periodically activated, performs time synchronization with the management node at the time of activation, performs intermittent operation waiting for a predetermined connection waiting time, and reduces connection waiting time during normal operation. A, B is the intermittent operation start interval, C is the connection waiting time at the time of initial setting and disconnection, D is the installation period, and X is the clock accuracy. A ≧ BX and C ≧ (B + D) X may be satisfied.

  According to this configuration, each connection state is set by providing an appropriate connection waiting time in the initial state (before the routing is performed during the installation work) and in the normal operation (after the installation work is completed and the routing is performed). Time synchronization with the management node of the communication node can be appropriately performed. As a result, time synchronization can be achieved while intermittently operating the communication node, so that power saving of the communication node can be realized.

  According to the management node and the wireless communication system of the wireless communication system of the present invention, the largest number of communication nodes are connected to the wireless communication system for each wireless communication distance from the management node. Thereby, it is possible to automatically configure a wireless communication system having as few routers as possible and having optimized router placement locations and number of placements.

FIG. 1 is a block diagram illustrating an example of a functional configuration of a general node. FIG. 2 is a block diagram illustrating an example of a functional configuration of a general coordinator. FIG. 3 is a conceptual diagram illustrating an example of a wireless communication system with a mesh topology. FIG. 4 is a conceptual diagram illustrating an example of a tree topology wireless communication system. FIG. 5 is a schematic diagram showing an arrangement example of nodes and coordinators. FIG. 6A is a diagram illustrating an example of a routing result by flooding. FIG. 6B is a diagram illustrating an example of a manual routing result. FIG. 7 is a flowchart illustrating an example of the routing process according to the first embodiment. FIG. 8A is a sequence chart illustrating a specific example of the routing process according to the first embodiment. FIG. 8B is a sequence chart illustrating a specific example of the routing process according to the first embodiment. FIG. 8C is a sequence chart illustrating a specific example of the routing process according to the first embodiment. FIG. 9A is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9B is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9C is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9D is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9E is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9F is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9G is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9H is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9I is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9J is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9K is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 9L is a schematic diagram illustrating a progress status of the routing process according to the first embodiment. FIG. 10 is a diagram illustrating an example of a tree network configured by the routing process according to the first embodiment. FIG. 11 is a diagram illustrating an example of a mesh network configured by routing processing according to the first embodiment. FIG. 12 is a diagram illustrating an example of a mesh network configured by excluding the failed node by the routing process according to the first embodiment. FIG. 13 is a diagram illustrating an example of a mesh network configured to bypass an obstacle by the routing process according to the first embodiment. FIG. 14A is a sequence chart illustrating a specific example of routing processing according to the second embodiment. FIG. 14B is a sequence chart illustrating a specific example of the routing process according to the second embodiment. FIG. 15 is a diagram illustrating an example of a mesh network in which efficiency is increased according to the second embodiment. FIG. 16 is a diagram illustrating an example of a mesh network in which efficiency is improved according to the second embodiment. FIG. 17 is a diagram illustrating an example of a mesh network in which efficiency is improved according to the second embodiment. FIG. 18A is a diagram for explaining intermittent operation of a node according to the third embodiment. FIG. 18B is a diagram for explaining an intermittent operation of a node according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. Among the constituent elements in the following embodiments, constituent elements not described in the independent claims are described as optional constituent elements. In addition, the size or ratio of components shown in the drawings is not necessarily strict.

(Embodiment 1)
The wireless communication system according to Embodiment 1 includes a management node (coordinator) and a plurality of communication nodes (also simply referred to as nodes) whose initial state is an end device (first mode in which data is not relayed). Wireless communication network. The end device can operate by switching to a router (second mode in which data is relayed) in accordance with an instruction.

  The coordinator sets the number of nodes that can be directly connected to the farthest most distant nodes in the router for each wireless communication distance represented by the number of hops from the coordinator. Automatically configure an optimized wireless communication system.

  Below, for convenience, the configuration of a general wireless communication system and nodes will be described, and then characteristic routing processing by the coordinator will be described in detail.

  FIG. 1 is a block diagram illustrating an example of a functional configuration of a general node. As shown in FIG. 1, the node 10 includes a communication circuit 11, an antenna 16, and an I / F (interface) 17, and can operate as any of an end device and a router.

  The node 10 is used, for example, as a communication adapter for an external device such as a sensor or an actuator for transmitting and receiving measurement results and control data.

  The communication circuit 11 includes a transmission / reception unit 12, a CPU (Central Processing Unit) 13, a ROM (Read Only Memory) 14, and a RAM (Random Access Memory) 15.

  The transmission / reception unit 12 transmits and receives a radio signal (radio frequency electromagnetic wave) using the antenna 16 in accordance with a radio communication standard such as ZigBee (registered trademark), for example.

  A communication circuit control program is written in the ROM 14 connected to the CPU 13. The RAM 15 is a memory area for operating the communication circuit control program. The RAM 15 may hold operation mode information that specifies whether the node 10 operates as an end device or a router. The communication circuit control program causes the node 10 to operate as an end device or a router according to the operation mode information stored in the RAM 15.

  The I / F 17 transmits / receives data to / from an external device such as a sensor or actuator according to a wired or wireless communication standard such as USB (Universal Serial Bus).

  FIG. 2 is a block diagram illustrating an example of a functional configuration of a general coordinator. As shown in FIG. 2, the coordinator 20 is configured by changing the I / F 18 of the node 10 and adding a network control unit 21.

  The coordinator 20 is used, for example, as a gateway that relays measurement results and control data of external devices between the node 10 and the Internet or server.

  The I / F 18 transmits and receives data to and from the Internet or a server according to a wired or wireless communication standard such as Ethernet (registered trademark).

  The network control unit 21 is a broadband router that relays data between a wireless communication network including the coordinator 20 and the Internet or a server.

  By using the plurality of nodes 10 and the coordinator 20, it is possible to construct a large-scale wireless communication system with a low-output communication device without arranging a high-output, high-sensitivity base station or access point. Such a wireless communication system is constructed as a multi-hop network having a mesh or tree topology configuration.

  FIG. 3 is a conceptual diagram illustrating an example of a wireless communication system with a mesh topology.

  FIG. 4 is a conceptual diagram illustrating an example of a tree topology wireless communication system.

  3 and 4, the communication path is represented by a solid line connecting the two nodes 10. Further, the node 10 operating as an end device is represented by a white rectangle, the node 10 operating as a router is represented by a light gray rectangle, and the coordinator 20 is represented by a dark gray rectangle. Such color coding of end devices, routers, and coordinators is used as appropriate in other figures. The wireless communication systems 1 and 2 in FIGS. 3 and 4 are configured in accordance with a wireless communication standard such as ZigBee (registered trademark), for example.

  The node 10 is used, for example, as a communication adapter for sensors and actuators, for transmitting and receiving sensor measurement results and actuator control data. The node 10 can operate by switching between an end device that does not relay data (first mode) and a router that relays data (second mode) according to an instruction from the coordinator 20.

  The coordinator 20 sets a communication route (solid line between the nodes 10 in FIGS. 3 and 4) in the wireless communication systems 1 and 2 and distributes a route table representing the set communication route to each node 10. The node 10 operating as a router relays data according to the routing table.

  The wireless communication systems 1 and 2 are connected to the Internet 40 or the server 30 via a coordinator 20 as a gateway, and are used as a sensor network that collects sensor measurement data and a control network that performs actuator drive control. The server 30 may be arranged in the wireless communication systems 1 and 2.

  FIG. 5 is a schematic diagram illustrating an arrangement example of the nodes 10 and the coordinator 20. In FIG. 5, the individual nodes 10 are distinguished by the letters A to L. With reference to FIG. 5, a general routing process conventionally performed by the coordinator 20 will be described as a comparative example.

  For example, in the routing by flooding generally performed in the sensor network, the coordinator 20 broadcasts a survey signal. The investigation signal is transferred (flooded) between the nodes 10 capable of direct communication and spreads over the entire wireless communication network. The node 10 performs routing by recording the node 10 that is the transmission source of the received investigation signal as a router. The node 10 transmits the sensor data to the recorded router, so that the sensor data is transferred in the reverse direction along the route of the investigation signal and reaches the coordinator 20.

  FIG. 6A is a diagram illustrating an example of a routing result by flooding. As shown in FIG. 6A, when routing by flooding is performed, all the nodes 10 to which the investigation signal is transferred become routers, and therefore, it is easy to set routers excessively and obtain an efficient route with a small number of hops. Is difficult.

  Although it is possible to reduce the number of routers manually, selection and arrangement of nodes to be operated as routers require know-how such as confirmation of propagation conditions at the site, and there is no routine procedure.

  FIG. 6B is a diagram illustrating an example of a manual routing result. As shown in FIG. 6B, in the case of manual operation, routers are often arranged all along the route from the coordinator 20 to the node 10 with an emphasis on the stability of wireless connection. In order to further reduce the number of routers, complicated and difficult work is required, such as confirmation of the propagation state in the field so that the stability of the wireless connection is maintained.

  In view of such circumstances, as a result of intensive studies, the present inventors have conducted routing processing capable of automatically configuring a wireless communication system having as few routers as possible and having optimized router placement locations and number of placements, and We have devised a coordinator that performs such routing processing.

  FIG. 7 is a flowchart illustrating an example of the routing process according to the embodiment. The flowchart of FIG. 7 represents a process of setting, as a router, a node that can be directly connected to the largest number of nodes farther away for each wireless communication distance represented by the number of hops from the coordinator 20.

  For example, the routing process may include a first process and a second process.

  In the first process, a communication node capable of directly communicating with the coordinator 20 is classified as a communication node having a wireless communication distance of 1 hop.

  In the second processing, among the first communication nodes that are one or more communication nodes having the largest number of hops among the classified wireless communication distances, the largest number of second communications whose wireless communication distances are not yet classified. A first communication node capable of directly communicating with the node is instructed to operate in the second mode. Further, the largest number of the second communication nodes are classified as communication nodes having a hop number larger than the hop number of the first communication node. The second process is executed until there is no communication node whose wireless communication distance is not classified.

  For example, a beacon signal for investigation is used to determine a directly connectable node. In the following description and illustration, for the sake of brevity, the wireless communication distance is referred to as a short distance, and a hop that is a unit of the wireless communication distance may be omitted.

  8A to 8C are sequence charts showing a specific example of the routing process of FIG. 7 corresponding to the node arrangement of FIG. 8A to 8C show the passage of time from the top to the bottom of the figure.

  9A to 9L are schematic diagrams showing the progress of the routing process of FIG. 7 corresponding to the node arrangement of FIG. 9A to 9L, the reach range of the beacon signal is indicated by a thick broken line, the node whose distance is not known is indicated by a dotted circle, and the node whose distance is known is indicated by a circle of a line type different for each distance. ing. Further, the node 10 operating as an end point is indicated by a white circle, the node 10 operating as a router is indicated by a light gray circle, and the coordinator 20 is indicated by a dark gray circle.

  The description will be continued with reference to FIGS. 7, 8A to 8C, and 9A to 9L.

  First, a node capable of directly communicating with the coordinator 20 is identified (S11 in FIG. 7), and the identified node is classified as a node having a distance of 1 (S12 in FIG. 7). Here, the processing of S11 to S12 in FIG. 7 is an example of the first processing.

  As a specific example, the coordinator 20 broadcasts a beacon signal for investigation (S11 in FIG. 8A). The beacon signals are received by the nodes A, B, C, and E (FIG. 9A), and the nodes A, B, C, and E transmit response signals for the beacon signals. Here, the set of response signals is an example of list information of nodes that responded to the beacon signals.

  The response signal may simply be confirmation that the beacon signal has been successfully received. Further, even if it is determined that the beacon signal has a predetermined received signal quality (for example, the signal strength RSSI or the signal-to-noise ratio S / N is equal to or higher than a predetermined value), a response signal is transmitted. Good. Further, the response signal may include an identifier of a node that transmits the response signal, and additional information such as received signal quality may be added.

  The coordinator 20 receives response signals from the nodes A, B, C, and E. The coordinator 20 specifies that the coordinator 20 and the nodes A, B, C, and E can communicate directly based on the response signal.

  The coordinator 20 classifies the nodes A, B, C, and E as nodes having a distance of 1 (S12 in FIG. 8A). Here, the classification may be that the identifiers of the nodes A, B, C, and E are associated with the distance value 1 and recorded in the RAM 15 of the coordinator 20. In FIG. 9A to FIG. 9L, a node whose distance is 1 is indicated by a thick solid line circle.

  Next, the loop counter i is initialized to 1 (S13 in FIG. 7), and loop processing is executed (S14 to S19 in FIG. 7). Here, the processing of S14 to S19 in FIG. 7 is an example of the second processing.

  In the loop processing, first, a node that can directly communicate with each of the nodes having the distance i (that is, the first communication node having the largest number of hops in the classified wireless communication distance) is identified (in FIG. 7). S14).

  As a specific example in the first iteration of the loop process, the coordinator 20 instructs each of the nodes A, B, C, and E having a distance of 1 to transmit a beacon (S14 in FIG. 8B). Each of the nodes A, B, C, and E, when receiving the beacon transmission instruction, broadcasts a beacon signal for investigation.

  The beacon signal transmitted from node A is received by nodes B, D, and E (FIG. 9B), and nodes B, D, and E transmit a response signal indicating that the beacon signal has been received. The node A receives the response signal from the nodes B, D, and E and transfers it to the coordinator 20. The coordinator 20 specifies that the node A and the nodes B, D, and E can be directly communicated based on the response signal transferred from the node A.

  Similarly, the beacon signal of node B is received by nodes A, C, D, E, and F (FIG. 9C), and the beacon signal of node C is received by nodes B, E, and F (FIG. 9D), and the node The beacon signal of E is received by nodes A, B, C, D, F, G, H, and I (FIG. 9E). Nodes B, C, and E receive response signals for their respective beacon signals and transfer them to the coordinator 20.

  The coordinator 20 can directly communicate with the node B and the nodes A, C, D, E, and F based on the transferred response signal, and can directly communicate with the node C and the nodes B, E, and F. , Node E and nodes A, B, C, D, F, G, H, and I are identified as being directly communicable.

  Next, for each node having a distance i, the number of additional connections, which is the number of nodes that have not yet been classified among the nodes that can directly communicate with the node (that is, the second communication node), is counted. (S15 in FIG. 7).

  In the first iteration, nodes A, B, C, and E are classified as nodes having a distance of 1. Therefore, for each of the nodes A, B, C, and E, the number of nodes excluding the nodes A, B, C, and E from the nodes that responded to the beacon signal for investigation is counted as the number of additional connections (in FIG. 8B). S15). As a result, the numbers of additional connections of nodes A, B, C, and E are obtained as 1, 2, 1, and 5, respectively.

  If the maximum number of additional connections is 0 (YES in S16 in FIG. 7), there are no more nodes to be connected to the wireless communication network (in other words, there are no nodes whose distances are not classified). finish.

  If the maximum number of additional connections is not 0 (NO in S16 in FIG. 7), the second mode is instructed to the node for which the maximum number of additional connections is obtained (S17 in FIG. 7), and direct communication with the node is possible. And the node whose distance is not yet classified is classified as a node whose distance is i + 1 (S18 in FIG. 7).

  In the specific example, the coordinator 20 transmits a switching instruction to the second mode to the node E for which the maximum number of additional connections 5 is counted, and the node E becomes a router (S17 in FIG. 8B). At this time, the coordinator 20 instructs the node E to connect to the nodes D, F, G, H, and I as routers. This instruction corresponds to a route table representing a communication route.

  The coordinator 20 classifies the nodes D, F, G, H, and I as nodes having a distance of 2 (S18 in FIG. 8B). Here, the classification may be that the identifiers of the nodes D, F, G, H, and I are associated with the distance value 2 and recorded in the RAM 15 of the coordinator 20. In FIG. 9F to FIG. 9L, a node having a distance of 2 is indicated by a double circle.

  Although not shown, there is a case where any of the nodes A, B, and C can directly communicate with the node Z that cannot communicate directly with the node E. In that case, in addition to the node E, the node node A, B, or C that can directly communicate with the node Z is also set in the router, so that the signal path to the node Z can be secured.

  The loop counter i is incremented (S19 in FIG. 7), and the loop processing is continued.

  As a specific example in the second iteration of the loop processing, the coordinator 20 instructs each of the nodes D, F, G, H, and I having a distance of 2 to transmit a beacon (S14 in FIG. 8C). Similarly to the first iteration, nodes D, F, G, H, and I broadcast investigation beacon signals (FIGS. 9G to 9K), and nodes D, F, G, H, Nodes that can communicate directly with each of I are identified.

  In the second iteration, nodes A, B, C, and E are classified as nodes having a distance of 1, and nodes D, F, G, H, and I are classified as nodes having a distance of 2. Therefore, for each of nodes D, F, G, H, and I, the number of nodes excluding nodes A, B, C, D, E, F, G, H, and I from the nodes that responded to the investigation beacon signal Is counted as the number of additional connections (S15 in FIG. 8C). As a result, the number of additional connections of nodes D, F, G, H, and I is obtained as 0, 0, 2, 3, 2, respectively.

  The coordinator 20 transmits a switching instruction to the second mode to the node H for which the maximum number of additional connections 3 is counted, and the node H becomes a router (S17 in FIG. 8C). At this time, the coordinator 20 instructs the node H to connect to the nodes J, K, and L as routers. This instruction corresponds to a route table representing a communication route.

  The coordinator 20 classifies the nodes J, K, and L as nodes having a distance of 3 (S18 in FIG. 8C). Here, the classification may be that the identifiers of the nodes J, K, and L are associated with the distance value 3 and recorded in the RAM 15 of the coordinator 20. In FIG. 9L, the node whose distance is 3 is indicated by a thin solid circle.

  When it is known in advance that the nodes A to L are all nodes constituting the wireless communication network, the routing process may be terminated at this point. When the flowchart of FIG. 7 is followed, in the third iteration, nodes that can communicate directly with the nodes J, K, and L are identified, the number of additional connections of the nodes J, K, and L is obtained, and the maximum number of additional connections is 0. In some cases, the routing process may be terminated.

  The tree network shown in FIG. 10 is configured through the above procedure.

  According to the routing process described above, when a communication node within the wireless communication distance from the coordinator 20 to n hops is known, the wireless communication distance is not yet known (in other words, the network is not connected to the network). A node 10 capable of directly communicating with a large number of communication nodes is set as a router. The router to be set is connected to the wireless communication system as a communication node having a wireless communication distance of n + 1 hops as the maximum number of communication nodes, so that it has as few routers as possible, and the location and number of routers are optimized. A wireless communication system can be automatically configured.

  In addition, since whether or not direct communication is possible is specified by the beacon signal for investigation, an appropriate communication node reflecting the propagation situation at the site is set as a router. Therefore, for example, significant automation and labor saving are achieved as compared with the operation of setting the router while manually measuring the propagation state.

  In addition, after instructing one node to transmit a beacon signal, a response signal to the beacon signal is received from the one node and then another node is instructed to transmit a beacon signal. In addition, the response signal is less likely to be congested.

  The routing process described above can be modified as follows.

  For example, in S <b> 17 of FIG. 7, a connection for configuring the mesh network may be instructed to the node instructing the second mode.

  In the specific example, in the first iteration (S17 in FIG. 8B), the coordinator 20 instructs the node E to connect to the nodes A, B, and C in addition to the nodes D, F, G, H, and I. May be.

  In the second iteration (S17 in FIG. 8C), the coordinator 20 instructs the node H to connect to the nodes D, E, F, G, and I in addition to the nodes J, K, and L. Also good.

  Thus, the mesh network shown in FIG. 11 can be configured.

  In addition, the above-described routing processing can automatically configure a wireless communication system in which the location and number of routers are optimized even in an environment where there is a node failure or obstacle.

  The coordinator 20 can detect that there is no response from the node and its connection destination by detecting the loss of sensor data or detecting the response to the actuator setting.

  When the coordinator 20 detects the disconnection of the response from the node and the connection destination, the coordinator 20 sets all the nodes that can be directly connected from the node and the nodes set in the router at that time as end devices (that is, the first mode). Above, the above routing process may be performed again from the beginning. As a result, an appropriate signal path is reset by excluding a node in which the response is interrupted. Here, the disruption of the response from the node and its connection destination is an example of a condition for restarting the routing process from the beginning.

  For example, consider the case where the coordinator 20 detects that there is no response from the node E and its connection destination in the arrangement example of FIG. In this case, by performing the routing process from the beginning again, a mesh network excluding the node E as shown in FIG. 12 can be automatically configured.

  Further, in the arrangement example of FIG. 5, consider a case where there is an obstacle such as a wall that prevents direct communication between the node D and the node E and the node G and the node H. Even in this case, according to the routing processing described above, it is possible to specify that the node D and the node E, the node G and the node H are not directly communicable using the investigation beacon signal. Therefore, a mesh network that bypasses the obstacle 51 as shown in FIG. 13 can be automatically configured.

(Embodiment 2)
In the second embodiment, a modification of a method for transmitting a beacon signal for investigation for specifying a node capable of direct communication will be described.

  14A and 14B are sequence charts showing a specific example of the routing process of FIG. 7 corresponding to FIG. The sequence charts of FIGS. 14A and 14B are obtained by changing the sequence charts shown in FIGS. 8B and 8C, respectively, as follows. That is, after S14a in FIGS. 14A and 14B instructs one node to transmit a beacon signal, before receiving a response signal to the beacon signal from the one node, the beacon signal is transmitted to another node. It is changed to instruct to send.

  Each node transmits a beacon signal and a response signal under arbitration using an interference prevention function such as CSMA / CA (Carrier Sense Multiple Access / Collection Avidance).

  This makes it possible to transmit a beacon signal and receive a response signal in parallel at a plurality of nodes, and to easily reduce the time required for specifying whether or not direct communication is possible using a beacon signal.

  Even if a beacon signal is transmitted and a response signal is received in parallel at a plurality of nodes in accordance with the sequence charts of FIGS. 14A and 14B, the same network as in the first embodiment can be obtained. For example, specifically, the tree network shown in FIG. 10 and the mesh network shown in FIG. 11 are configured corresponding to the arrangement example of FIG.

  The coordinator 20 can improve the efficiency of the network based on each connection information. Here, efficiency means that a network having a more efficient configuration is obtained by deleting a communication path in the network. Hereinafter, an example of network efficiency improvement by the coordinator 20 will be described.

  FIG. 15 is a diagram illustrating an example of a mesh network connection in which efficiency is improved. According to this, for example, the route from the node A to the coordinator via the router E is not used, and when the router fails, the connection becomes impossible, that is, the route having no meaning for redundancy is removed.

  FIG. 16 shows the efficiency of the routing of FIG. 12, which is an example of the routing when the node E fails. A tree network can be constructed by reducing the number of routers and eliminating redundant routes from FIG. ing.

  FIG. 17 shows the efficiency of the routing of FIG. 13, which is an example of routing when there is an obstacle such as a wall, and is configured by eliminating redundant routes from FIG.

  In the first and second embodiments, the coordinator 20 has all the controller functions for controlling the construction of the network. However, the present invention is not limited to this example. For example, a part or all of the controller function may be performed by a server connected directly or indirectly to the coordinator 20. In particular, by providing a cloud server via the Internet with a function for performing flexible updates such as a routing optimization function, it becomes possible to construct a system corresponding to the development of algorithms.

(Embodiment 3)
In the third embodiment, an intermittent operation of the node 10 will be described.

  For the purpose of reducing power consumption when the node 10 is driven by a battery, all the nodes 10 may be operated intermittently in synchronization. For example, in a sensor network, a case where all nodes in the network are operated only during a period of sensor data collection provided periodically. When the entire network is operated intermittently, it is necessary to synchronize all the nodes and operate simultaneously. Therefore, time synchronization between the nodes is considered.

  The node 10 has a time mechanism such as an RTC (real time clock), and it is considered that the times of all the nodes 10 coincide when the routing is completed. Further, it is considered that an error with the clock accuracy X as a limit occurs at the time of the node 10.

  Assuming that the start cycle of the intermittent operation is B, the time of the node 10 is shifted by a maximum of BX per cycle of the intermittent operation. For example, when the activation cycle B is 1 day (= 86400 seconds) and the clock accuracy X is ± 50 ppm, the time error that can occur in one node 10 is ± 4.32 seconds, and the maximum deviation width between the nodes 10 is It becomes 8.64 seconds.

  It is considered that communication per intermittent operation is normally completed in 10 milliseconds or less. It is assumed that the node 10 can perform time synchronization with the coordinator 20 within this communication time.

  At this time, with respect to the activation cycle B and the clock accuracy X, the connection waiting time A for the node 10 to wait for connection at each activation of the intermittent operation is set so as to satisfy A ≧ BX.

  As shown in FIG. 18A, if the above conditions are satisfied, even if the time of the two nodes 10 is shifted to the maximum during one cycle of the intermittent operation, all the nodes 10 are simultaneously connected in the next cycle of the intermittent operation. Since there is a waiting period T (period shown in gray in FIG. 18A, T = A−BX), connection in the entire network can be established.

  Next, consider the initial setting and the resetting time when the connection is lost.

  Assuming that the maximum period for initial setting (installation construction) or failure repair (including maintenance) is D, the time of the node 10 is shifted by a maximum of DX per period D. For example, when the period D is 10 days (= 864000 seconds) and the clock accuracy is ± 50 ppm, the time error that can occur in one node 10 is ± 43.2 seconds, and the maximum deviation between the nodes 10 is 86. It will be 4 seconds.

  As shown in FIG. 18B, in order to connect a terminal that has not been connected to the synchronized period to the synchronized network, the connection waiting time C of the unconnected terminal is set to C based on the same concept as described above. It may be set to satisfy ≧ A + DX. A ≧ BX may be used to satisfy C ≧ (B + D) X. Specifically, the value of C is 95.04 seconds or more and rounded to 96 seconds or more.

  As a result, when using the wireless node setting device that synchronizes the time with the coordinator 20 when the node 10 is started, and if timing synchronization is established at the time of communication connection, the connection waiting time of only A and C is provided. Communication can be established and intermittent operation including a router becomes possible.

  In the above, for the sake of simplicity, time synchronization by RTC or the like is assumed. However, since it is only necessary to ensure a connection waiting time corresponding to the operation interval, for example, synchronization is achieved by a method of resetting a counter using an internal clock. May be. That is, according to this method, a synchronized intermittent operation can be performed without a circuit for holding time.

(Modification)
The management node and the wireless communication system of the wireless communication system according to the embodiments of the present invention have been described above, but the present invention is not limited to individual embodiments. Unless it deviates from the gist of the present invention, one or more of the present invention may be applied to various modifications that can be conceived by those skilled in the art, or forms constructed by combining components in different embodiments. It may be included within the scope of the embodiments.

  INDUSTRIAL APPLICABILITY The present invention can be widely used in various wireless networks such as sensor networks and actuator control networks as a management node and wireless communication system of a wireless communication system.

DESCRIPTION OF SYMBOLS 1, 2 Wireless communication system 10 Node 11 Communication circuit 12 Transmission / reception part 13 CPU
14 ROM
15 RAM
16 Antenna 17, 18 I / F
20 Coordinator 21 Network Control Unit 30 Server 40 Internet 51 Obstacle

Claims (8)

A management node of a wireless communication system composed of a plurality of communication nodes that operate by switching between a first mode that does not relay data and a second mode that relays data according to an instruction,
When a communication node having a radio communication distance of up to n hops (n is a natural number) is known from the management node, the communication having a known radio communication distance among communication nodes having a radio communication distance of n hops. Instructing a communication node capable of directly communicating with the largest number of communication nodes not included in the node to operate in the second mode;
A management node of a wireless communication system. The management node is
After performing a first process of classifying a communication node capable of directly communicating with the management node as a communication node having a wireless communication distance of 1 hop,
Among the first communication nodes that are one or more communication nodes having the maximum number of hops among the classified wireless communication distances, it is possible to directly communicate with the largest number of second communication nodes that are not yet classified. The first communication node is instructed to operate in the second mode, and the largest number of the second communication nodes are set as communication nodes having a hop count greater than a hop count of the first communication node. Performing the second process of classifying until there is no communication node whose radio communication distance is not classified,
The management node of the radio | wireless communications system of Claim 1. The management node is
In the first process, a beacon signal is transmitted and a communication node responding to the beacon signal is classified as a communication node having a wireless communication distance of 1 hop,
In the second process, the one or more first communication nodes are instructed to transmit a beacon signal, and a list of communication nodes responding to the beacon signal is obtained from each of the one or more first communication nodes, Instructing the first communication node having the largest number of communication nodes included in the list information and not yet classified in the wireless communication distance to operate in the second mode;
The management node of the radio | wireless communications system of Claim 2. When there are a plurality of the first communication nodes,
The management node, after instructing one first communication node to transmit a beacon signal, receives a response signal to the beacon signal from the one first communication node, and then sends it to the other first communication node. Instructing the beacon signal to be sent to
The management node of the radio | wireless communications system of Claim 3. When there are a plurality of the first communication nodes,
The management node directs the transmission of a beacon signal to one first communication node, and then, before receiving a response signal to the beacon signal from the first communication node, sends it to another first communication node. Instructing the beacon signal to be sent to
The management node of the radio | wireless communications system of Claim 3. When the predetermined condition is satisfied, the management node sets the plurality of communication nodes to the first mode, and then restarts the process of instructing the second mode from the beginning.
The management node of the radio | wireless communications system of any one of Claim 1 to 5. A plurality of communication nodes that operate by switching between a first mode that does not relay data and a second mode that relays data according to an instruction;
The management node according to any one of claims 1 to 6, which instructs at least one of the plurality of communication nodes to operate in the second mode;
A wireless communication system comprising: Each of the plurality of communication nodes is periodically activated, performs time synchronization with the management node at the time of activation, and performs an intermittent operation waiting for a predetermined connection waiting time,
A ≧ BX where A is the connection wait time during normal operation, B is the intermittent operation start interval, C is the connection wait time during initial setting and when the connection is broken, D is the period of installation, and X is the clock accuracy. And satisfying C ≧ (B + D) X.
The wireless communication system according to claim 7.

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