JP2013207763A - Path creation method and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to avoid path concentration in a specific node in radio communication.SOLUTION: A path creation method is the one in a communication system including a first communication device arranged in plurality in each geographically divided area and a second communication device communicating by radio with each of the first communication devices. To ensure that each of the first communication devices belonging to an area will not have their radio channel numbers overlapping in the area, and that each of radio channel numbers will be assigned to at least one of the first communication devices in the area, any one of a plurality of radio channel numbers is assigned to each of the first communication devices in an area, the channel assignment being made for each area in this way. Radio channels used by the second communication device and each of the first communication devices synchronously for each radio channel number are switched in order, and while so doing, a path is created between the second communication device and each of the first communication devices to which the switched radio channel number is assigned.

Description

  The present invention relates to a route creation method and a communication system.

  A wireless ad hoc network is a wireless communication network that wireless communication terminals establish autonomously. A wireless ad hoc network basically does not require a base infrastructure such as a base station required for wireless communication. Therefore, there is an advantage that a highly flexible network can be constructed at low cost.

JP 2009-86697 A JP 2011-14119 A

  However, when creating a communication path using existing protocols in a wireless ad hoc network, the efficiency of the entire network is not considered, and an optimal path (path with the lowest cost) is created between each wireless communication terminal. There is a high possibility. As a result, there is a possibility that the route is concentrated on a specific wireless communication terminal.

  Therefore, an object of one aspect is to make it possible to avoid concentration of routes to specific nodes in wireless communication.

  In one proposal, the route creation method includes a plurality of first communication devices arranged for each geographically divided area, and a second communication device that performs wireless communication with each of the first communication devices. A route creation method in a communication system, wherein, for each area, the first communication devices belonging to the area do not have overlapping radio channel numbers in the area, or each radio channel number in the area is at least Assigning any one of a plurality of radio channel numbers to each first communication device belonging to the area, so as to be assigned to one first communication device, the second communication device and each The first communication device synchronously switches the wireless channel to be used for each wireless channel number in order, and the second communication device and the switching destination wireless channel number are assigned. Wherein executing the path to create a process between the first communication device.

  According to one aspect, it is possible to avoid concentration of routes to specific nodes in wireless communication.

It is a figure which shows the structural example of the water level observation system in embodiment of this invention. It is a figure which shows the hardware structural example of the radio | wireless communication apparatus which each communication node in embodiment of this invention has. It is a figure for demonstrating an example of the process sequence of the production | generation process of the communication path | route in a water level observation system. It is a figure for demonstrating an example of the process sequence of the production | generation process of the communication path | route in a water level observation system. It is a figure for demonstrating an example of the process sequence of the production | generation process of the communication path | route in a water level observation system. It is a figure for demonstrating an example of the process sequence of the production | generation process of the communication path | route in a water level observation system. It is a figure which shows an example of the path | route for every wireless channel. It is a figure which shows an example of the route information in one observation node. It is a figure which shows the function structural example of the aggregation node in embodiment of this invention. It is a figure which shows the function structural example of the observation node in embodiment of this invention. It is a flowchart for demonstrating an example of the process sequence which an aggregation node performs at the time of a route creation. It is a figure which shows the structural example of a radio | wireless group information storage part. It is a flowchart for demonstrating an example of the process sequence which each observation node performs at the time of path | route creation. It is a flowchart for demonstrating an example of the process sequence which each observation node performs at the time of path | route creation. It is a figure which shows the structural example of a connection channel information storage part. It is a flowchart for demonstrating an example of the process sequence of a radio channel number allocation process. It is a figure which shows the example of the memory content of the connection channel information storage part for description of the allocation process of a radio channel number. It is a flowchart for demonstrating an example of the process sequence of the water level observation process which an aggregation node performs. It is a flowchart for demonstrating an example of the process sequence of the water level observation process which each observation node performs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a water level observation system according to an embodiment of the present invention. In FIG. 1, a water level observation system 1 includes an aggregation node N0 installed along a river R, observation nodes Ns1 to Ns9, and the like.

  The observation nodes Ns1 to Ns9 are devices that observe the water level of the river R at the position where each is installed. Note that, when the observation nodes Ns1 to Ns9 are not distinguished from each other, they are referred to as “observation node Ns”.

  The aggregation node N0 is a device that executes collection of observation data including the value of the observation water level from each observation node Ns. Wireless communication is used to collect observation data from each observation node Ns. That is, the aggregation node N0 and each observation node Ns have a wireless communication device. A wireless communication network (wireless ad hoc network) is formed between the aggregation node N0 and each observation node Ns using a wireless communication device. In addition, when not distinguishing the aggregation node N0 and each observation node Ns, it is called "communication node N".

  In the present embodiment, the range in which the water level is observed by the observation nodes Ns1 to Ns9 is divided by a plurality of observation areas. The observation area is a concept that divides the observation range of the water level observation system 1 based on a physical or geographical positional relationship. In FIG. 1, the example divided | segmented into observation area A1-A3 is shown. Observation area A1 includes observation nodes Ns1 to Ns3. Observation area A2 includes observation nodes Ns4 to Ns6. Observation area A3 includes observation nodes Ns7 to Ns9. Hereinafter, when the observation areas A1 to A3 are not distinguished, they are referred to as “observation area A”. Each observation node Ns stores the area number of the observation area A to which the observation node Ns belongs. The area number is an example of identification information of the observation area A. In the present embodiment, the numerical value at the end of observation area A is the area number of observation area A. Therefore, “1” is stored as the area number in the observation nodes Ns1 to Ns3. In the observation nodes Ns4 to Ns6, “2” is stored as the area number. In the observation nodes Ns7 to Ns9, “3” is stored as the area number.

  FIG. 2 is a diagram illustrating a hardware configuration example of a wireless communication device included in each communication node according to the embodiment of the present invention. 2, the wireless communication device 10 includes a ROM 101, a nonvolatile storage medium 102, a RAM 102, a CPU 104, a communication interface 105, and the like.

  A program for executing processing in the wireless communication apparatus 10 is installed in the ROM 101 or the nonvolatile storage medium 102. For example, the program may be stored in the ROM 101 when the program is installed in advance when the wireless communication device 10 is shipped. In addition to the program, the ROM 101 and the nonvolatile storage medium 102 can also store various data used by the program. The RAM 102 stores a program read from the ROM 101 or the non-volatile storage medium 102 when a program activation instruction is issued. The CPU 104 executes functions to be described later related to the wireless communication device 10 according to a program stored in the RAM 102. The communication interface device 105 is hardware including an antenna for performing wireless communication.

  Hereinafter, an outline of a processing procedure executed in the water level observation system 1 will be described. 3-6 is a figure for demonstrating an example of the process sequence of the production | generation process of the communication path | route in a water level observation system. The process of FIGS. 3-6 is performed when the water level observation system 1 starts operation, for example.

  In step S101, the aggregation node N0 transmits a “connection request” by broadcast (BC) using a predetermined specific radio channel (hereinafter referred to as “radio channel A”). The “connection request” is an example of a telegram or a message (hereinafter, referred to as “telegram”) indicating a connection request for a wireless communication network with the aggregation node N0. The wireless channel A is, for example, a wireless channel having a minimum frequency among channels usable in the water level observation system 1. The messages in steps S101 to S128, S130, and S132 are transmitted using the wireless channel A.

  In the “connection request” packet, 1 is set as TTL (Time To Live) so that ad hoc relaying is not performed. In the “connection request”, all radio channel numbers used in radio communication at the time of water level observation are designated. In the present embodiment, 1, 2, and 3 are designated as radio channel numbers. That is, in the present embodiment, three radio channels are used during water level observation. In addition, when the radio channel number to be used is known in each observation node Ns, the radio channel number does not necessarily have to be specified in the “connection request”.

  The observation node Ns that has received the “connection request” transmitted from the aggregation node N0 transmits the “connection response” by broadcast (S102 to S105). The “connection response” is an example of a message indicating a response that the “connection request” has been received. FIG. 3 shows an example in which the “connection request” radio wave reaches a range including observation nodes Ns1 to Ns3 belonging to observation area A1 and observation node Ns4 belonging to observation area A2 (see step S101). . Therefore, the “connection response” is transmitted by the observation nodes Ns1 to Ns4.

  The aggregation node N0 recognizes that the observation node Ns is installed in the neighboring area by receiving the “connection response”. The aggregation node N0 continues to transmit the “connection request” until a “connection response” equal to or greater than the number of radio channels to be used is received. That is, each “connection response” is returned at random with a time shift so as not to collide with each other. In the present embodiment, three radio channels are used. Therefore, the aggregation node N0 stops transmitting the “connection request” when three connection responses are received.

  Subsequently, each observation node Ns that has received the “connection request” executes arbitration of the radio channel to be used in the observation area A to which the own node belongs after transmitting the “connection response”. Radio channel arbitration means assignment of radio channel numbers. That is, in the present embodiment, different observation channel Ns belonging to the same observation area A are assigned different radio channel numbers. However, if there is a relationship of the number of observation nodes Ns in one observation area A> the number of radio channels to be used, the same radio channel number may be assigned to a plurality of observation nodes Ns. In this case, each radio channel number to be used may be assigned to at least one observation node Ns.

  Specifically, each observation node Ns that has transmitted the “connection response” transmits a “ch arbitration request” by broadcast (S106 to S109). Steps S106 to S109 indicate “ch arbitration requests” transmitted from the observation nodes Ns1 to Ns4 in that order. The “ch arbitration request” is an example of a message for requesting radio channel arbitration to another node belonging to the same observation area A as the own node. In the “ch arbitration request” packet, TTL is set to 1 so that ad-hoc relaying is not performed. In the “ch arbitration request”, the area number of the observation area A to which the own node belongs, the radio channel number specified in the received “connection request”, and priority information are specified. Since 1 to 3 are designated as the wireless channel numbers for the connection nodes from the aggregation node N0, 1 to 3 are designated as the wireless channel numbers even in the “ch arbitration request”. The priority information is information indicating the priority in the arbitration of the radio channel number. In the present embodiment, the node number of each observation node Ns is designated as priority information. In the present embodiment, the node number matches the number at the end of the sign of each observation node Ns. The smaller the node number, the higher the priority.

  The observation node Ns that has received the “ch arbitration request” from all other nodes in the same observation area A to which the own node belongs has the priority information specified in the received “ch arbitration request” and the priority of the own node. Compare with information. As a result of the comparison, the observation node Ns having the highest priority indicated by the priority information of the own node (that is, the observation node Ns having the smallest node number of the own node) is assigned to each observation node in the same observation area A. Assign radio channel numbers. Details of the allocation method will be described later.

  In observation area A1, “ch arbitration request” is transmitted from all observation nodes A in steps S106 to S108. Accordingly, the observation node Ns1 having the highest priority determines the assignment of radio channel numbers to the observation nodes Ns2 and Ns3 including the own node. When the assignment of the radio channel number is determined, the observation node Ns1 broadcasts a “ch arbitration response” that is an example of a message indicating the assignment result of the radio channel number (S110). In the “ch arbitration response” packet, TTL is set to 1 so that ad-hoc relaying is not performed. In the “ch arbitration response”, the node number of the observation node Ns to which the wireless channel number is assigned is specified for each wireless channel number. In the example of step S110, an example in which the observation node Ns1, the observation node Ns2, and the observation node Ns3 are assigned in the order of the wireless channel numbers 1, 2, and 3 is shown. After transmitting the “ch arbitration response”, if there is no retransmission of the “ch arbitration request” from another node within a certain period (eg, 10 seconds), the assignment of the radio channel number is confirmed.

  The radio channel number assignment may be performed by each observation node Ns in the same observation area A. This is because if the allocation logic is unified in each observation node Ns, the allocation result should be the same. However, in the unlikely event of an inconsistency, in the present embodiment, radio channel number assignment is performed by one observation node Ns having the highest priority.

  On the other hand, as a result of comparison between the priority information specified in the “ch arbitration request” and the priority information of the own node, the observation nodes Ns2 and Ns3 whose priority indicated by the priority information of the own node is not the highest Wait for receipt of "response". When the “ch arbitration response” is received, the observation nodes Ns2 and Ns3 transmit the radio channel number assigned to the node number of the own node in the “ch arbitration response” to, for example, the RAM 102 or the nonvolatile RAM 103. Remember.

  In the observation area A2, the observation nodes Ns5 and Ns6 have not received the “connection request”. Therefore, the observation nodes Ns5 and Ns6 have not yet transmitted “ch arbitration request”. Therefore, at this time, the observation node Ns4 does not receive the “ch arbitration request” from all other nodes in the same observation area A to which the own node belongs. Therefore, the observation node Ns4 continues to transmit the “ch arbitration request”.

  Subsequently, the observation nodes Ns1 to Ns3 for which the assignment of the radio channel number is determined transmit “inter-area connection request” by broadcast (S111, S112, FIG. 4: S113). The “inter-area connection request” is an example of a message indicating a wireless communication network connection request to another observation area A such as the adjacent observation area A. The “inter-area connection request” is a message for notifying the observation node Ns in another observation area A of the radio channel number used by the observation node Ns that is the transmission source of the message.

  In the “inter-area connection request”, the radio channel number assigned to the transmission source observation node Ns, the area number of the observation area A to which the observation node Ns belongs, the cost value, the belonging node number, and the like are designated. In the present embodiment, the cost value is the number of hops from the aggregation node 0. The belonging node number is a list of node numbers of observation nodes to which the radio channel number assigned to the transmission source observation node Ns has already been assigned. In steps S111 to S113, the node number designated as the belonging node number matches the node number of the observation node that is the transmission source of the “inter-area connection request”.

  Subsequently, each observation node Ns that has received an “inter-area connection request” from another observation area A executes arbitration of the radio channel to be used in the observation area A to which the own node belongs. That is, as in the case where the “connection request” is received from the aggregation node N0, arbitration of the radio channel to be used is executed.

  Specifically, each observation node Ns that has transmitted an “inter-area connection request” in which the area numbers of other observation areas A are specified transmits a “ch arbitration request” by broadcast (S114 to S116). Steps S114 to S116 indicate “ch arbitration requests” transmitted from the observation nodes Ns4 to Ns6 in order. In the “ch arbitration request” transmitted in response to the “inter-area connection request”, in addition to the node number, area number, and priority information of the own node, the aggregation node N0 or any other observation area A and which Information indicating at what cost value the wireless channel number can be connected is designated. This information is specified based on the “connection request” or “inter-area connection request” received at the own node.

  For example, the observation node Ns4 receives the “connection request” from the aggregation node N0 and the “interarea connection requests” from the observation nodes Ns1 to Ns3. Therefore, the observation node Ns4 can be connected to the aggregation node N0 with the wireless channel numbers 1 to 3 at the cost value 0, and can be connected to the observation area A1 with the wireless channel numbers 1 to 3 at the cost 1. Information is designated in the “ch arbitration request” in step S114. That is, the parameters specified in the received “connection request” or each received “inter-area connection request” are integrated and specified in the “ch arbitration request”. As the cost value with the observation area A1, the cost value specified in the “inter-area connection request” transmitted from the observation node Ns in the observation area A1 is used as it is. In step S114, the aggregation node N0 is expressed as “area 0”.

  The observation node Ns5 receives each “inter-area connection request” from the observation nodes Ns1 to Ns3. Therefore, the observation node Ns5 designates information indicating that connection is possible at the cost 1 by the observation area A1 and the wireless channel numbers 1 to 3 in the “ch arbitration request” in step S115.

  The observation node Ns6 receives each “inter-area connection request” from the observation nodes Ns2 and Ns3. Therefore, the observation node Ns5 designates information indicating that connection is possible at the cost 1 by the observation area A1 and the wireless channel number 2 or 3 in the “ch arbitration request” in step S116.

  The “ch arbitration request” from all other nodes belonging to the observation area A2 is received, and the observation node Ns4 having the highest priority receives the assignment of the radio channel numbers to the observation nodes Ns5 and Ns6 including the own node. It is determined based on the “ch arbitration request” or the like. When the assignment of the radio channel number is determined, the observation node Ns4 broadcasts a “ch arbitration response” indicating the assignment result of the radio channel number (S117). The observation nodes Ns5 and Ns6 store the radio channel number assigned to the node number of the own node in the “ch arbitration response”, for example, in the RAM 102 or the nonvolatile RAM 103.

  The “inter-area connection request” in step S113 is also received by the observation nodes Ns7 to Ns9 belonging to the observation area A3. Accordingly, the observation nodes Ns7 and Ns8 start transmitting the “ch arbitration request” in response to the reception of the “inter-area connection request”, which is described in the figure after step S121 for convenience.

  Subsequently, the observation nodes Ns4 to Ns6 for which the assignment of the radio channel number is determined transmit “inter-area connection request” by broadcast (S118, S119, S120). In each “inter-area connection request”, as the belonging node number, in addition to the node number of the observation node Ns that is the transmission source of the “inter-area connection request”, the same radio channel number as the observation node Ns in the observation area A1 Is assigned to the observation node Ns. The node number of the corresponding observation node Ns in the observation area A1 is specified based on the belonging node number specified in the “inter-area connection request” from each observation node Ns in the observation area A1.

  The description of the processing procedure (FIG. 5: S121 to S124) executed in the observation area A3 in response to the “inter-area connection request” transmitted from each observation node Ns in the observation area A2 is omitted because it is obvious from the above. . In this processing procedure, a radio channel number is assigned to each observation node Ns belonging to the observation area A3.

  In the present embodiment, when assignment of the radio channel number of each observation node Ns is determined in observation area A3, which is the final observation area, all observation nodes Ns in observation area A3 transmit a “route creation request” by broadcast. (FIG. 6: S125-S127). The “route creation request” is a message that requests the aggregation node N0 to start creation of a wireless communication route. Therefore, in the “route creation request” packet, for example, “128” is specified as the TTL so that the message reaches the aggregation node N0. In the “route creation request”, the radio channel number assigned to the observation node Ns as the transmission source and the node number associated with the radio channel number are specified.

  When the “route creation request” is received for all the wireless channel numbers of the wireless channel numbers to be used, the aggregation node N0 creates routes in order for each wireless channel. Specifically, the aggregation node N0 uses, for example, the wireless channel A to broadcast “ch change notification” in which the wireless channel number that is the target of route creation is specified (S128). The “ch change notification” is an example of a message requesting all the observation nodes Ns to change the radio channel used for communication. Accordingly, for example, “128” is specified as the TTL in the “ch change notification” packet so that the message reaches all the observation nodes Ns. In the first “ch change notification”, for example, “1” is designated as the radio channel number.

  Each observation node Ns that has received the “ch change notification” matches the radio channel number used for communication with the radio channel number specified in the “ch change notification”. Therefore, initially, communication is performed using the radio channel associated with radio channel number 1.

  Subsequently, a route from the aggregation node N0 to each observation node Ns is created using the radio channel associated with the radio channel number 1 (S129). For the route creation, a known protocol such as ADOV (Ad hoc On-Demand Distance Vector) may be used. However, the observation node Ns to which the wireless channel number 1 which is the current wireless channel number is not assigned does not transfer the route search packet (route search packet). That is, the observation node Ns to which the wireless channel number 1 is not assigned is set so that it does not become a relay node but a terminal node of the route. Therefore, the observation node Ns to which the radio channel number 1 is not assigned can receive a message from the aggregation node N0 using the radio channel path related to the radio channel number 1, but the aggregation node N0 The message is not transferred to other observation node Ns.

  Subsequently, the processing similar to steps S128 and S129 is repeated for other radio channel numbers (S130 to S133).

  As a result, a route for each radio channel number is created so that the observation node Ns having the same radio channel number is connected as a relay node across the observation area A. Therefore, it is possible to avoid the concentration of the route to the specific observation node Ns. In the path for each radio channel number, the observation node Ns to which the radio channel number is not assigned is connected to the path as a termination node. Therefore, for example, even when the observation node Ns cannot communicate with the aggregation node N0 due to the route of the radio channel number assigned to the observation node Ns, the route of another radio channel number (that is, the detour) ), The observation node Ns can communicate with the aggregation node N0.

  FIG. 7 is a diagram illustrating an example of a route for each wireless channel. FIG. 7 shows an example of the main route between the aggregation node N0 and each observation node Ns1. The main route refers to a route on the radio channel related to the radio channel number assigned to the own node for each observation node Ns.

  For example, the observation node Ns9 in the observation area A3 communicates with the aggregation node N0 via a route in the wireless channel with the wireless channel number 2 (hereinafter referred to as “route 2”). In the route 2, relay is performed by the observation node Ns2 and the observation node Ns5.

  However, as described above, each observation node Ns also participates as a termination node in a route on a wireless channel related to a wireless channel number other than the wireless channel number assigned to the own node. Therefore, even if a failure occurs in the observation node Ns2 or Ns5, the observation node Ns9 may communicate with the aggregation node using the route 3 or route 1 in the wireless channel related to the wireless channel number 3 or 1. it can. In FIG. 7, such a route is also indicated by a dashed arrow. That is, when using the path 3, the observation node Ns9 can communicate with the aggregation node N0 by relaying between the observation node Ns3 and the observation node Ns7. Further, when using the route 1, the observation node Ns9 can communicate with the aggregation node N0 by relaying between the observation node Ns4 and the observation node Ns8. Such communication is possible when the observation node Ns7 recognizes the existence of the observation node Ns9 when the path 3 is created, and the observation node Ns8 recognizes the existence of the observation node Ns9 when the path 1 is created. Because.

  Note that the observation node Ns9 stores route information as shown in FIG. 8, for example. FIG. 8 is a diagram illustrating an example of route information in one observation node.

  The route information shown in FIG. 8 includes a NextHop and a cost value for each radio channel number as a route destined for the aggregation node N0. NextHop is the node number of the observation node Ns that is the next hop destination. The cost value is a cost value in the route. As shown in FIG. 7, since the radio channel number assigned to the observation node Ns9 is 2, normally, the next hop destination is the observation node Ns5.

  Note that similar route information is stored for other observation nodes Ns by creating routes. However, the observation node Ns serving as the relay node in the radio channel associated with the radio channel number assigned to the own node is not only the aggregation node but also the path including the Next Hop and the cost value when the other observation node Ns is the destination. Store information.

  Next, an example of communication processing using the route created as described above will be described. In the present embodiment, such a route is used for transferring observation data indicating the observation water level. In other words, in the present embodiment, when the creation of the route for each radio channel is completed, the observation of the water level is started. In the following description, a set of observation nodes Ns to which the same radio channel number is assigned is referred to as a “radio channel group”. As is clear from the above, the radio channel group is formed across a plurality of observation areas A.

  Regarding the observation of the water level, in the present embodiment, there are mainly two time periods. One is a cycle in which the aggregation node N0 collects water level observation data from each observation node Ns. Hereinafter, this period is referred to as “collection period”. The collection cycle is a longer cycle than the other cycle, such as an interval of 10 minutes. The other is a cycle in which, for each radio channel group, the observation node Ns belonging to the radio channel group is activated and water level observation (sensing) is performed. This period is called “observation start-up period”. The observation start cycle is shorter than the collection cycle, such as an interval of 10 seconds. Each observation node Ns shifts to a sleep state (power saving state) after the water level observation is executed. Therefore, the activation of the observation node Ns means a return from the sleep state.

  Hereinafter, an outline of the operation of the water level observation system 1 during the water level observation will be described.

  When the observation of the water level is started, each observation node Ns is activated in turn in, for example, a round robin method for each observation node Ns belonging to the same radio channel group in the observation activation period, and the observation of the water level (sensing). I do. If the water level does not exceed the threshold value for the warning water level (or the warning water level), the observation nodes Ns belonging to the radio channel group enter a sleep state. That is, each observation node Ns belonging to the same radio channel group repeats activation, observation, and sleep at a timing different from that of each observation node Ns belonging to another radio channel group and in synchronization with the observation activation period. Note that, from the viewpoint of early detection of exceeding the warning water level, it is preferable that the difference in the observation activation period between the radio channel groups is formed so that at least one radio channel group is always activated.

  The observation node Ns that has detected that the warning water level has been exceeded at the time of observation start-up period uses the radio channel associated with the radio channel number assigned to the own node to immediately detect that the water level has been exceeded. Notify N0 by unicast. The notification is transferred to the aggregation node N0 through the route created for the radio channel. “Immediately” includes meaning that is independent of the collection period.

  On the other hand, the aggregation node N0 collects observation data from each observation node Ns in the collection cycle. Specifically, the aggregation node N0 requests transmission of observation data by unicast from the observation nodes Ns belonging to the radio channel group in order in units of radio channel groups. Each observation node Ns that receives the observation data transmission request observes the water level and returns the observation data.

  When the notification of exceeding the water level is received at a timing different from the collection cycle, the aggregation node N0 shortens the collection cycle for all the observation nodes Ns of the radio channel group to which the observation node Ns that is the notification source of excess water level belongs. An instruction is given to switch to (for example, one minute interval). Thereafter, for the radio channel group, the aggregation node N0 collects observation data in a short cycle.

  When the next radio channel group is activated after receiving the notification of exceeding the water level, the aggregation node N0 instructs all the observation nodes Ns of the radio channel group to switch the collection cycle to a short cycle. Thus, the collection cycle of each radio channel group is switched to a short cycle in order.

  Thereafter, when the monitoring water level excess is no longer detected by all the observation nodes Ns of all the radio channel groups, the collection cycle is sequentially switched to the normal cycle (for example, every 10 minutes) in units of radio channel groups.

  Subsequently, in order to realize the processing procedure described above, a functional configuration example included in the aggregation node N0 or each observation node Ns will be described.

  FIG. 9 is a diagram illustrating a functional configuration example of the aggregation node according to the embodiment of the present invention. In FIG. 9, the aggregation node N0 includes a connection request transmission unit 121, a connection response confirmation unit 122, a channel change notification transmission unit 123, a route creation request processing unit 124, a route creation unit 125, an observation data request unit 126, and an observation data response process. A unit 127, a sleep command transmission unit 128, a water level excess notification processing unit 129, a collection cycle switching notification unit 130, a processing time setting unit 131, and the like. Each of these units is realized by processing that the program installed in the aggregation node N0 causes the CPU 104 of the aggregation node N0 to execute.

  The aggregation node N0 also uses the radio group information storage unit 141, the route information storage unit 142, the cycle information storage unit 143, and the like. These units can be realized by using, for example, the RAM 102 or the nonvolatile RAM 103 of the aggregation node N0.

  The connection request transmission unit 121 transmits a “connection request”. The connection response confirmation unit 122 confirms reception of the “connection response” returned in response to the “connection request”. The channel change notification transmission unit 123 transmits “channel change notification”. In response to the reception of the “route creation request” transmitted from the observation node Ns in the final observation area, the route creation request processing unit 124 obtains the wireless channel number specified in the “route creation request” and the belonging node number. The data is stored in the wireless group information storage unit 141 in association with each other. That is, the radio group information storage unit 141 stores information indicating to which radio channel group each observation node Ns belongs. The route creation unit 125 controls creation of a wireless channel route for each wireless channel number.

  The observation data request unit 126 transmits an “observation data request”, which is an example of a message requesting transmission of the water level observation data, to the observation node Ns. The observation data response processing unit 127 determines whether the collection cycle should be a normal cycle or a short cycle based on the observation data included in the response returned from the observation node Ns in response to the “observation data request”. . The sleep command transmission unit 128 transmits a “sleep command”, which is an example of a message for instructing transition to a sleep state (power supply OFF state or power saving state), to the observation node Ns. The water level excess notification processing unit 129 executes a process corresponding to a “water level excess notification” which is a message for notifying that the observed water level has exceeded the warning water level threshold. The collection cycle switching notifying unit 130 transmits “collection cycle switching”, which is an example of a message notifying that the collection cycle is switched from the normal cycle to the short cycle, to the observation node Ns. The processing time setting unit 131 sets a time at which the aggregation node N0 should next execute processing based on the collection cycle or the observation activation cycle for each radio channel group.

  The route information storage unit 142 stores a so-called routing table (route information). For example, route information as illustrated in FIG. 8 is stored in the route information storage unit 142. However, the route information in the aggregation node N0 includes a NextHop, a cost value, and the like when each observation node Ns is a destination for each wireless channel. The period information storage unit 143 stores information indicating the collection period and the observation activation period of each radio channel group.

  FIG. 10 is a diagram illustrating a functional configuration example of the observation node according to the embodiment of the present invention. As shown in FIG. 10, each observation node Ns includes a connection request processing unit 201, a connection response transmission unit 202, a channel arbitration request transmission unit 203, a channel arbitration request processing unit 204, a channel arbitration unit 205, and a channel arbitration response transmission unit. 206, ch arbitration response processing unit 207, inter-area connection request transmission unit 208, inter-area connection request processing unit 209, route creation request transmission unit 210, route creation request transfer unit 211, ch change processing unit 212, route selection unit 213, A water level observation unit 214, an observation data response unit 215, a sleep command processing unit 216, a water level excess notification unit 217, a collection cycle switching processing unit 218, a startup time setting unit 219, a group switching unit 220, and the like. Each of these units is realized by processing executed by the CPU 104 of each observation node Ns by a program installed in each observation node Ns.

  Each observation node Ns also uses the connection channel information storage unit 231 and the path information storage unit 232. Each of these storage units can be realized using the RAM 102 or the nonvolatile RAM 103 of each observation node Ns.

  The connection request processing unit 201 executes processing according to the “connection request”. For example, the connection request processing unit 201 stores information specified in “connection request” in the connection channel information storage unit 231. The connection response transmission unit 202 transmits a “connection response”. The ch arbitration request transmission unit 203 transmits a “ch arbitration request”. The channel arbitration request processing unit 204 executes processing according to the “channel arbitration request”.

  The ch arbitration unit 205 assigns a radio channel number to each observation node Ns in the same observation area A when the priority of the own node is the highest. When the priority of the own node is the highest, the ch arbitration response transmission unit 206 transmits a “ch arbitration response”. The ch arbitration response processing unit 207 executes processing according to the “ch arbitration response”. The inter-area connection request transmission unit 208 transmits an “inter-area connection request”. The inter-area connection request processing unit 209 executes processing according to the “inter-area connection request”. For example, the inter-area connection request processing unit 209 stores information specified in “inter-area connection request” in the connection channel information storage unit 231. The connection channel information storage unit 231 stores information indicating which observation channel A or the aggregation node N0 can be connected to with which radio channel number.

  The route creation request transmitting unit 210 transmits a “route creation request” when the own node belongs to the final observation area. The route creation request transfer unit 211 transfers or relays the “route creation request” transmitted from each observation node Ns in the final observation area when the node does not belong to the final observation area. The ch change processing unit 212 executes processing according to “ch change notification”.

  The water level observation unit 214 controls water level observation. In response to the “observation data request”, the observation data response unit 215 returns a response including the water level observation data to the aggregation node N0. The sleep command processing unit 216 executes processing according to the “sleep command”. The water level excess notification unit 217 transmits a “water level excess notification” to the aggregation node N0 when the observed water level exceeds the warning water level.

  The collection cycle switching processing unit 218 executes processing according to “collection cycle switching”. The activation time setting unit 219 sets the next time when the own node is activated based on the collection period or the observation activation period of the radio channel group to which the own node belongs. The group switching unit 220 switches a radio channel to be used to a radio channel of another radio channel group when communication with the aggregation node N0 is disabled in the radio channel of the radio channel group to which the own node belongs. By doing so, a detour is secured for communication with the aggregation node N0.

  The route information storage unit 232 stores a so-called routing table (route information). For example, the route information storage unit 232 stores route information as described in FIG.

  Hereinafter, an example of a processing procedure executed by the aggregation node N0 or each observation node Ns in the processing described with reference to FIGS.

  FIG. 11 is a flowchart for explaining an example of a processing procedure executed by the aggregation node when creating a route. The contents of each message are as described in FIGS. 3 to 6 unless otherwise specified.

  In step S201, the connection request transmission unit 121 transmits a “connection request” by broadcast. Subsequently, the connection response confirmation unit 122 waits for reception of a “connection response” (S202). Whenever the “connection response” is received (YES in S202), the connection response confirmation unit 122 determines whether or not the “connection response” in which the area number of the observation area A1 is specified is received more than the number of radio channels to be used. Is determined (S203).

  When the “connection response” in which the area number of the observation area A1 is designated is received more than the number of radio channels to be used (YES in S203), the route creation request processing unit 124 sends each observation node belonging to the final observation area A3. Waiting for reception of a “route creation request” from Ns (S204). Each time a “route creation request” is received, the route creation request processing unit 124 associates the radio channel number specified in the “route creation request” with the belonging node number, and creates a wireless group information storage unit. 141 stored.

  FIG. 12 is a diagram illustrating a configuration example of a wireless group information storage unit. In FIG. 12, the wireless group information storage unit 141 stores the belonging node number for each wireless channel number. The belonging node number is a list of node numbers of the observation nodes Ns to which the wireless channel number is assigned. With the radio group information storage unit 141, the aggregation node N0 can specify the observation node Ns belonging to each radio channel group.

  When “route creation requests” for the number of radio channels to be used are received (YES in S204), the ch change notification transmission unit 123 designates one radio channel number of the radio channels to be used, and “ch” “Change notification” is transmitted to all observation nodes Ns (S205). Subsequently, the path creation unit 125 controls the creation of a path from the aggregation node N0 to each observation node Ns in the radio channel associated with the radio channel number (S206). That is, the communication in step S206 is performed using the radio channel. Also, a known protocol such as ADOV may be used for creating the route. When the creation of a route with each observation node Ns for the wireless channel is completed (YES in S207), the route creation unit 125 determines whether or not the creation of the route has been completed for all the wireless channels to be used (S208). . If there is a wireless channel for which a route has not yet been created (NO in S208), Step S205 and subsequent steps are executed for the wireless channel. When routes are created for all the radio channels (YES in S209), the aggregation node N0 executes a water level observation process (S210). Details of the water level observation process will be described later.

  13 and 14 are flowcharts for explaining an example of a processing procedure executed by each observation node when a route is created.

  In step S301, the observation node Ns waits for reception of a message. When the “connection request” is received (YES in S302), the connection request processing unit 201 associates the cost value with the identification information of the aggregation node N0 for each wireless channel number specified in the “connection request”. “0” is stored in the connection channel information storage unit 231. Subsequently, the connection response transmission unit 202 transmits a “connection response” (S303).

  On the other hand, when the “inter-area connection request” is received (NO in S302 and YES in S304), the connection request processing unit 201 determines the area number specified in the “inter-area connection request” for each radio channel number. And the cost value are stored in the connection channel information storage unit 231.

  Note that the storage of information in the connection channel information storage unit 231 in response to reception of the “connection request” or “inter-area connection request” is performed every time a “connection request” or “inter-area connection request” is received. The Therefore, when the “connection request” or “inter-area connection request” shown in FIGS. 3 to 6 is transmitted / received, information as shown in FIG. 15 is connected to each observation node Ns in each observation area A. It is stored in the channel information storage unit 231.

  FIG. 15 is a diagram illustrating a configuration example of a connection channel information storage unit. In FIG. 15, (1) collectively shows the storage contents of the connection channel information storage unit 231 of the observation nodes Ns1 to Ns3 in the observation area A1. Each column in the first row indicates the node number of each observation node Ns. Each row in the first column indicates a radio channel number. For example, channel number 1 is expressed as “ch1”. In FIG. 15, the identification information of the aggregation node N0 is expressed as “area 0”.

  Each of the observation nodes Ns1 to Ns3 receives the “connection request” in which the wireless channel numbers 1 to 3 are designated from the aggregation node N0 (see S101 in FIG. 3). Therefore, in the observation nodes Ns1 to Ns3, information (area 0: cost 0) indicating that connection is possible from the aggregation node N0 (area 0) at the cost 0 is stored for each of the radio channel numbers 1 to 3. . Note that the information stored in the connection channel information storage unit 231 of each observation node Ns is for one column. For example, the information stored in the connection channel information storage unit 231 of the observation node Ns1 is information related to the column whose node number is “1”.

  (2) collectively shows the storage contents of the connection channel information storage unit 231 of the observation nodes Ns4 to Ns6 in the observation area A2. The observation node Ns4 has received the “connection request” from the aggregation node N0 (see FIG. 3: S101). Therefore, in the observation node Ns4, information (area 0: cost 0) indicating that connection is possible from the aggregation node N0 (area 0) at the cost 0 is stored for each of ch1 to ch3. The observation nodes Ns4 and Ns5 have received “inter-area connection requests” from all the observation nodes Ns in the observation area A1 (see FIG. 3: S111, S112, FIG. 4: S113). Therefore, in the observation nodes Ns4 and Ns5, information (area 1: cost 1) indicating that connection is possible from the observation area A1 (area 1) with the cost 1 is stored for each of ch1 to ch3. “Connectable from observation area A1 at cost 1” means that it can be connected to the aggregated node N0 at cost 1 via observation area A1.

  The observation node Ns6 receives the “inter-area connection request” in which the radio channel number 2 or 3 is designated from the observation nodes Ns2 and Ns3 in the observation area A1 (see FIG. 3: S112, FIG. 4: S113). . Accordingly, in the observation node Ns6, information (area 1: cost 1) indicating that connection is possible from the observation area A1 (area 1) with the cost 1 is stored for each of the ch2 and ch3.

  (3) collectively shows the storage contents of the connection channel information storage unit 231 of the observation nodes Ns7 to Ns9 in the observation area A3. The observation nodes Ns7 to Ns9 have received the “interarea connection request” in which the radio channel number 3 is designated from the observation node Ns3 in the observation area A1 (see FIG. 4: S113). Therefore, in the observation nodes Ns7 to Ns9, information (area 1: cost 1) indicating that connection is possible from the observation area A1 (area 1) at the cost 1 is stored for ch3. The observation nodes Ns7 and Ns8 have received the “interarea connection request” in which the radio channel number 1 and the cost 1 are specified from the observation node Ns4 in the observation area A2 (see FIG. 4: S118). Therefore, in the observation nodes Ns7 and Ns8, information (area 2: cost 1) indicating that connection is possible from the observation area A2 (area 2) with the cost 1 is stored for ch1. Further, the observation nodes Ns7 to Ns9 have received the “inter-area connection request” in which the radio channel number 2 and the cost 2 are designated from the observation node Ns5 in the observation area A2 (see FIG. 4: S119). Therefore, in the observation nodes Ns7 to Ns9, information (area 2: cost 2) indicating that connection is possible from the observation area A2 (area 2) at the cost 2 is stored for ch2. Furthermore, the observation nodes Ns7 and Ns8 have received the “inter-area connection request” in which the radio channel number 3 and the cost 2 are designated from the observation node Ns6 in the observation area A2 (see FIG. 4: S120). Therefore, in the observation nodes Ns7 and 8, information (area 2: cost 2) indicating that connection is possible from the observation area A2 (area 2) at the cost 2 is stored for ch2.

  Subsequent to YES in step S303 or step S304, the ch arbitration request transmission unit 203 transmits a “ch arbitration request” (S305). In the “ch arbitration request”, an area number to which the own node belongs, priority information, and information stored in the connection channel information storage unit 231 of the own node at the time when the “ch arbitration request” is transmitted are specified. .

  Subsequently, the ch arbitration request processing unit 204 waits for a certain period of time and determines whether or not a “ch arbitration request” has been received from all other nodes belonging to the same observation area A as the own node (S306). When the “ch arbitration request” has not been received from one or more other nodes belonging to the same observation area A (NO in S306), Step S304 and subsequent steps are repeated. If a “ch arbitration request” is received from all other nodes belonging to the same observation area A (YES in S306), the process proceeds to step S307.

  Note that the ch arbitration request processing unit 204 is designated as the “ch arbitration request” each time a “ch arbitration request” in which the same area number as the area number of the observation area A to which the own node belongs is received. Information is stored in the connection channel information storage unit 231. As a result, for example, when the own node belongs to the observation area A1, the storage content of the connection channel information storage unit 231 of the own node is as shown in FIG. That is, the information stored in the connection channel information storage unit 231 of the other node until then is also stored in the connection channel information storage unit 231 of the own node. Similarly, when the own node belongs to the observation area A2, the storage content of the connection channel information storage unit 231 of the own node is as shown in FIG. Similarly, when the own node belongs to the observation area A3, the storage contents of the connection channel information storage unit 231 of the own node are as shown in FIG. 15 (3).

  In step S307, the channel arbitration unit 205 compares the node number that is the priority information of the own node with the node number that is the priority information specified in the “ch arbitration request” from another node. That is, the priorities of the own node and other nodes are compared. When the priority of the own node is the highest (YES in S307), the ch arbitration unit 205 executes a wireless channel number assignment process (S308). In the radio channel number assignment process, radio channel numbers are assigned to the own node and all other nodes belonging to the same observation area A. The radio channel number assigned to the own node is stored in, for example, the nonvolatile RAM 103. Details of the radio channel number assignment process will be described later. Further, as described above, the channel arbitration unit 205 of each observation node Ns may determine the radio channel number for the own node.

  Subsequently, the ch arbitration response transmission unit 207 transmits a “ch arbitration response” in which the radio channel number assignment result is designated (S309). If a “ch arbitration request” is received from another node in the same observation area A after transmission of the “ch arbitration response” (YES in S311), step S307 and subsequent steps are repeated. For example, in the other node that has received the “ch arbitration response”, if the radio channel number specified in the “ch arbitration response” cannot communicate with another observation area A, the “ch arbitration request” from the other node. Is sent.

  When a “ch arbitration request” from another node in the same observation area A is not received (NO in S311), the ch arbitration unit 205 waits for a certain time (S312). When the accumulated value of the waiting time of the predetermined time has not passed the preset waiting time (NO in S313), Step S309 and subsequent steps are repeated. When the accumulated value of the waiting time of the predetermined time has passed a preset waiting time (YES in S313), the process proceeds to step S316 in FIG.

  On the other hand, if the priority of the own node is not the highest in step S307 (YES in S307), the ch arbitration response processing unit 207 waits for reception of a “ch arbitration response” from another node in the same observation area A. (S314). When the “ch arbitration response” is received (YES in S314), the ch arbitration request processing unit 204 receives the radio channel number assigned to the own node in the “ch arbitration response” from another observation area A. It is then determined whether or not the “area indirect connection request” is designated (S315). The determination is based on whether the connection channel information storage unit 231 stores information indicating any area number and cost value for the combination of the node number of the own node and the wireless channel number. It can be carried out. Note that this determination corresponds to a determination as to whether or not the own node can communicate with another observation area A by the wireless channel associated with the wireless channel number assigned in the “ch arbitration response”.

  When the wireless channel number assigned to the own node in the “ch arbitration response” is not specified in the “area indirect connection request” received from the other observation area A (NO in S315), steps S304 and after are repeated. . In other words, by retransmitting the “ch arbitration request”, the reassignment of the radio channel number is requested to another node.

  If the channel number assigned to the own node in the “ch arbitration response” is specified in the “area indirect connection request” received from another observation area A (YES in S315), the process proceeds to step S316 in FIG. move on. In this case, the radio channel number assigned to the own node in the “ch arbitration response” is stored in the nonvolatile RAM 103, for example.

  In step S316 of FIG. 14, the route creation request transmission unit 210 determines whether or not the own node belongs to the final observation area. For example, information indicating belonging to the final observation area may be stored in the nonvolatile RAM 103 of each observation node Ns in the final observation area. Alternatively, the area number of the last observation area may be stored in the nonvolatile RAM 103 of each observation node Ns. Based on such information stored in the non-volatile RAM 103, the determination in step S316 can be executed.

  When the own node does not belong to the final observation area (NO in S316), the inter-area connection request transmission unit 208 transmits an “inter-area connection request” (S317). Subsequently, the route creation request transfer unit 211 waits for reception of a “route creation request” from the observation node Ns belonging to the final observation area (S318). When the “route creation request” is received (YES in S318), the route creation request transfer unit 211 subtracts 1 from the TTL specified in the “route creation request”, and forwards the “route creation request” by broadcast. (S319). Then, it progresses to step S321.

  On the other hand, when the own node belongs to the final observation area (YES in S316), the route creation request transmitting unit 210 transmits a “route creation request” (S320). Then, it progresses to step S321.

  In step S321, the ch change processing unit 212 waits for reception of a “ch change notification” from the aggregation node N0. When “ch change communication” is received, the ch change processing unit 212 subtracts 1 from the TTL specified in the “ch change notification” and forwards the “ch arbitration request” by broadcast (S322). Subsequently, the ch change processing unit 212 changes the radio channel used for communication to the radio channel associated with the radio channel number designated in the “ch change notification” (S323). Therefore, next time communication is performed using the wireless channel until step S323 is executed.

  Subsequently, the path selection unit 213 determines whether or not the radio channel number designated in the “ch change notification” is the radio channel number assigned to the own node (S324). When the wireless channel number designated in the “ch change notification” is the wireless channel number assigned to the own node (YES in S324), the route selection unit 213 sends the route search packet to the own node so as to forward it. It sets (S325). On the other hand, when the wireless channel number designated in the “ch change notification” is not the wireless channel number assigned to the own node (NO in S324), the route selection unit 213 does not forward the route search packet so as not to forward the route search packet. (S326).

  The setting for the own node in step S325 or S326 may be performed by storing flag information in the RAM 102, for example.

  Subsequently, the route selection unit 213 performs route selection using a known protocol such as ADOV (S327). At this time, the handling of the route search packet is changed according to the setting in step S325 or S326.

  Steps S321 to S327 are executed for all radio channel numbers to be used (S328).

  Subsequently, the observation node Ns executes a water level observation process (S329). Details of the water level observation process will be described later.

  Next, details of step S308 in FIG. 13 will be described. FIG. 16 is a flowchart for explaining an example of a processing procedure of radio channel number assignment processing.

  In step S401, the channel arbitration unit 205 refers to the connection channel information storage unit 231, and determines whether there is a radio channel number for which there is only one connectable observation node Ns. Here, for convenience of explanation, it is assumed that the own node is the observation node Ns7, and the storage content of the connection channel information storage unit 231 is in the state shown in FIG.

  FIG. 17 is a diagram illustrating an example of the contents stored in the connection channel information storage unit for explaining the radio channel number assignment process.

  In FIG. 17, only the observation node Ns7 can be connected to ch1. Accordingly, the process proceeds to step S402, and the ch arbitration unit 205 assigns ch1 to the observation node Ns7.

  Subsequently, the ch arbitration unit 205 excludes the information stored in the column of the observation node Ns7 to which ch1 is assigned and the information stored in the row of ch1 from the processing targets in FIG. Subsequently, the channel arbitration unit 205 determines whether or not the assignment of radio channel numbers to all the observation nodes Ns belonging to the same observation area A is completed (S408). This determination can be made based on whether all information stored in the connected channel information storage unit 231 has been excluded from the processing target.

  Here, since no radio channel number is assigned to the observation nodes Ns8 and Ns9 (NO in S408), the process returns to step S401.

  In step S401, the ch arbitration unit 205 determines whether or not there is a radio channel number in which only one observation node Ns is connectable among ch2 and ch3. Here, there is no corresponding radio channel number (NO in S401). Therefore, the ch arbitration unit 205 selects the observation node Ns having the highest priority among the observation nodes Ns to which no radio channel number is assigned (S403). Here, the observation node Ns8 having the smallest node number is selected.

  Subsequently, the channel arbitration unit 205 determines whether or not the minimum cost value is recorded for only one radio channel number for the observation node Ns8 (S404). In FIG. 17, regarding the observation node Ns8, the minimum cost 1 is recorded only for ch2 (YES in S404). Therefore, the ch arbitration unit 205 assigns ch2 in which the cost 1 is recorded to the observation node Ns8 (S405).

  Subsequently, the ch arbitration unit 205 excludes information stored in the column of the observation node Ns8 to which ch2 is assigned and information stored in the ch2 row from subsequent processing targets (S407). Subsequently, since no radio channel number is assigned to the observation node Ns9 (NO in S408), the process returns to step S401.

  In step S401, the channel arbitration unit 205 determines the presence / absence of a wireless channel number for which there is only one connectable observation node Ns. Here, since only the pair of ch3 and observation node Ns9 remains, the process proceeds to step S402. In step S402, the ch arbitration unit 205 assigns ch3 to the observation node Ns9.

  Since the assignment of the radio channel numbers to all the observation nodes Ns in the same observation area A has been completed (YES in S408), the processing in FIG.

  If the cost 1 is also recorded for ch3 in step S404 (NO in S404), the ch arbitration unit 205 determines the radio channel number in which the cost 1 is recorded for the observation node Ns8. Among these, the smallest radio channel number is assigned to the observation node Ns8 (S406). Therefore, ch2 having the smaller value of ch2 and ch3 is assigned to observation node Ns8.

  Next, details of step S209 in FIG. 11 will be described. FIG. 18 is a flowchart for explaining an example of the processing procedure of the water level observation processing executed by the aggregation node.

  When the observation data requesting unit 126 detects the arrival of the observation data collection time based on the collection period (YES in S501), the radio channel group to be the first to collect the observation data is selected as the radio channel group to be collected for the observation data. (S502). The collection time is set at the previous collection time, as will be described later.

  Subsequently, the aggregation node N0 collects observation data from all the observation nodes Ns belonging to the wireless channel group (S503). Specifically, the observation data request unit 126 transmits “observation data request” in turn to each observation node Ns belonging to the radio channel group by unicast. The observation data response processing unit 127 receives a response from the observation node Ns with respect to the “observation data request”, and stores the observation data included in the response in, for example, the RAM 102. That is, polling is sequentially performed on each observation node Ns belonging to the radio channel group. Each observation node Ns belonging to the radio channel group can be identified with reference to the radio group information storage unit 141.

  Steps S502 and S503 are executed in order for all the radio channel groups (S504). When the collection of observation data from all the wireless channel groups is completed (YES in S504), the observation data response processing unit 127 determines whether or not the warning water level threshold has been exceeded for all collected observation data (S505). . When the water level indicated by all the observation data is equal to or less than the threshold value (NO in S505), the observation data response processing unit 127 sets the collection cycle as the normal cycle in the cycle information storage unit 143 (S506). The normal period is, for example, an interval of 10 minutes. On the other hand, when the water level indicated by at least one observation data exceeds the threshold (YES in S505), the observation data response processing unit 127 sets the collection period to the short period in the cycle information storage unit 143 (S507). The short period is, for example, one minute interval.

  Subsequently, the observation data response processing unit 127 turns off the collection cycle switching transmission setting (S508). The collection cycle switching transmission setting is a setting indicating whether or not “collection cycle switching” should be transmitted to the observation node Ns when the observation start time described later arrives. If the collection cycle switching transmission setting is OFF, it means that it is not necessary to transmit the message.

  Subsequently, the sleep command transmission unit 128 first sets the radio channel used for transmission of the “sleep command” to the radio channel number of the radio channel group to be transmitted (S509). Subsequently, the sleep command transmission unit 128 transmits “sleep command” in order by unicast to all the observation nodes Ns belonging to the wireless channel group (S510). In the “sleep command”, information that can specify the next collection time is specified. For example, information indicating whether the collection cycle is a normal cycle or a short cycle is specified in the “sleep instruction”. Alternatively, the next collection time determined based on the normal cycle or the short cycle may be designated as a “sleep command”.

  Steps S509 and S510 are executed in order for all the radio channel groups (S511). When the transmission of the “sleep command” is completed for all the wireless channel groups (YES in S511), the processing time setting unit 131 determines whether the next processing time is the collection time or the observation start time (S512). ). The collection time and the observation activation time can be specified based on the collection period or the observation activation period of each radio channel group.

  When the next processing time is the collection time (YES in S512), the processing time setting unit 131 determines whether the collection cycle is a normal cycle with reference to the cycle information storage unit 143 (S513). When the collection cycle is a normal cycle (YES in S513), the processing time setting unit 131 calculates the next collection time by adding the normal cycle to the last collection time (S514). If the collection cycle is a short cycle (NO in S513), the processing time setting unit 131 calculates the next collection time by adding the short cycle to the last collection time (S515). The collection time calculated in step S514 or S515 is stored in the RAM 102, for example.

  If it is determined in step S512 that the next processing time is the observation start time of any one of the radio channel groups (NO in S512), the processing time setting unit 131 displays the last observation start time of the radio channel group. Is added to the observation activation period to calculate the next observation activation time. The processing time setting unit 131 stores the calculated observation start time in, for example, the RAM 102 (S516).

  On the other hand, when the water level excess notification processing unit 129 detects the arrival of the observation start time set for a certain radio channel group in step S516 (YES in S521), the radio channel excess radio channel group associated with the radio channel number of the radio channel group is selected. The wireless channel to be used is set (S522).

  Subsequently, the water level excess notification processing unit 129 determines whether or not the collection cycle switching transmission setting is ON (S523). When the collection cycle switching transmission setting is OFF (NO in S523), the water level excess notification processing unit 129 receives the “water level excess notification” during the reception waiting time of the “water level excess notification” (S526). (YES in S524), the collection cycle switching transmission setting is turned ON (S525).

  After the elapse of the reception time of “water level excess notification” (YES in S526), when the collection cycle switching transmission setting is ON (YES in S527), the collection cycle switching notification unit 130 sets “collection cycle switching” to the current It transmits by unicast in order with respect to all the observation nodes Ns of a radio channel group (S528). For transmission of “collection cycle switching”, the wireless channel set in step S522 is used.

  On the other hand, when the collection cycle switching transmission setting is ON in step S523 (YES in S523), step S528 is immediately executed. In this case, since the excess water level is observed in the other radio channel groups, the current radio channel group is also notified of the fact that the collection cycle is short.

  Subsequent to step S528, steps after step S512 are executed.

  Next, details of step S329 in FIG. 14 will be described. FIG. 19 is a flowchart for explaining an example of a processing procedure of water level observation processing executed by each observation node.

  When the observation node Ns reaches the activation time (S601), the observation node Ns changes from the sleep state to the activation state. The activation time is either an observation time determined based on the collection cycle or an observation activation time determined based on the observation activation cycle.

  When the current time is the collection time (YES in S602), the observation data response unit 215 sets the radio channel related to the radio channel number of the radio channel group to which the own node belongs as the radio channel to be used (S603). Subsequently, the water level observation unit 214 performs water level observation (S604). The water level observation at the collection time may be performed for a longer time than the water level observation at the observation start time. For example, the observation may be performed for about 20 seconds to 60 seconds, and the smoothing process may be performed. Subsequently, the observation data response unit 215 waits for reception of an “observation data request” from the aggregation node N0 using the radio channel set in step S603 (S605). When the “observation data request” is received (YES in S605), the observation data response unit 215 returns a response including the observation data indicating the observation result in step S604 to the aggregation node N0 (S606).

  Subsequently, the sleep command processing unit 216 waits for reception of a “sleep command” (S607). If the “sleep command” is not received after waiting for the waiting time (YES in S608), the observation node Ns returns to step S601 without sleeping.

  When the “sleep command” is received (YES in S607), the activation time setting unit 219 determines whether the collection cycle specified in the “sleep command” is a normal cycle (S609). When the collection cycle specified in the “sleep instruction” is a normal cycle (YES in S609), the activation time setting unit 219 determines whether the next activation time is the collection time or the observation activation time. (S610). The collection time and the observation activation time can be specified based on the collection period or the observation activation period of the radio channel group to which the own node belongs.

  When the next activation time is the collection time (YES in S610), the activation time setting unit 219 sets the next collection time as the next activation time (S611). When the next activation time is the observation activation time (NO in S610), the activation time setting unit 219 sets the next observation activation time of the radio channel group to which the own node belongs as the next activation time (S612).

  In step S609, when the collection cycle specified in the “sleep instruction” is a short cycle (NO in S609), the activation time setting unit 219 adds the short cycle to the last collection time to obtain the next collection time. Is calculated. The activation time setting unit 219 sets the calculated collection time as the next activation time (S613).

  After execution of step S611, S612, or S613, the observation node Ns enters a sleep state.

  On the other hand, when the activation time is not the collection time (NO in S602), the water level observation unit 214 performs water level observation (S614). For example, a short-term observation of about 3 seconds is performed. Subsequently, the water level observation unit 214 determines whether or not the observation water level exceeds the warning water level threshold value (S615). When the observed water level is equal to or lower than the threshold value (NO in S615), step S609 and subsequent steps are executed.

  When the observed water level exceeds the threshold (YES in S615), the water level excess notification unit 217 transmits the “water level excess notification” to the aggregation node N0 by unicast using the radio channel set in step S603. (S616). Subsequently, the collection cycle switching processing unit 218 waits for reception of “collection cycle switching” (S617). When “collection cycle switching” is received (YES in step S617), step S609 and subsequent steps are executed. At this time, in step S609, it is determined that the collection cycle is a short cycle.

  Thus, according to the water level observation method of the present embodiment, each observation node Ns is grouped across a plurality of observation areas A based on the concept of a radio channel group, and is round-robin in units of radio channel groups. To observe the water level. Therefore, water level observation can always be performed in the same observation area A. As a result, it is possible to ensure the real-time property of detecting the excess of the warning water level. That is, it is possible to immediately detect that the observation water level has exceeded the threshold value. For example, the observation frequency can be increased by immediately switching the collection cycle to a short cycle.

  If “collection cycle switching” is not received even after the waiting time has elapsed (YES in S618), there is a possibility that a failure has occurred on the route of the current wireless channel. Therefore, the group switching unit 220 changes the radio channel number used by the own node to the radio channel number of the next radio channel group in the order of the radio channel numbers (S619). Subsequently, the group switching unit 220 sets the observation start time of the next radio channel group as the start time of the own node (S620). The difference in the observation start cycle for each radio channel group may be set in advance for each observation node Ns. Based on the deviation, the observation activation time of the next radio channel group can be calculated. After execution of step S620, the observation node Ns enters a sleep state. When the observation node Ns is activated next time, the observation node Ns is activated in synchronization with the observation node Ns of the next radio channel group. Therefore, the observation node Ns can communicate with the aggregation node N0 by using the radio channel route (that is, the detour) of the next radio channel group.

  As described above, according to the communication path creation method of the present embodiment, a radio channel number is assigned to each observation node Ns for each observation area A. Thereafter, the aggregation node N0 and each observation node Ns are synchronized to switch the radio channel for each radio channel number, and a path between the aggregation node N0 and the observation node Ns to which the radio channel number is assigned is created. . As a result, the route is distributed for each radio channel group. Therefore, it is possible to avoid the concentration of routes on a specific observation node Ns.

  In addition, the observation node Ns to which the radio channel number of the radio channel related to the creation of the route is not assigned configures the route as a termination node of the route. Since it is a terminal node, there is a low possibility that the route is concentrated on the observation node Ns. In addition, by configuring a route related to a wireless channel number that is not assigned to the own node, the need for route reconfiguration in the event of a communication failure is reduced. As a result, each observation node Ns can quickly secure a detour. In addition, it is possible to reduce the necessity of installing the detour observation node Ns in advance.

  Furthermore, when the observation channel Ns completes the assignment of the radio channel numbers to all the observation nodes Ns in the same observation area A, each observation node Ns transmits an “inter-area connection request” in which the radio channel number assigned to the own node is designated. To do. Each observation node Ns in the subsequent observation area A is assigned one of the radio channel numbers specified in the “inter-area connection request” received by the own node. Therefore, a radio channel number that is highly likely to be actually communicable can be dynamically assigned to each observation node Ns.

  Thus, by automatically selecting the radio channel number of each observation node Ns, the designer of the water level observation system 1 or the like reduces the necessity of designing the assignment of the radio channel number to each observation node Ns. Can be made.

  More specifically, when the radio channel number of each observation node Ns is determined in advance by design, a situation may occur in which the received electric field strength between the actual observation nodes Ns is weaker than the value assumed at the time of design due to the influence of the surrounding environment. sell. In this case, change the installation position (observation position) of the observation node Ns in question, or replace the radio channel used by the observation node Ns with another observation node in the same observation area A, It is necessary to change the design so that communication can be performed via the observation node Ns having a high received electric field strength. According to the present embodiment, it is possible to reduce the possibility that such complicated work occurs.

  In addition, since each observation node Ns is a terminal node in a route related to a radio channel number that is not assigned to the own node, when the communication is performed using the radio channel related to the radio channel number, each observation node Ns enters a sleep state. However, the possibility of affecting the communication of the other observation node Ns to which the radio channel number is assigned is low. In other words, each observation node Ns can enter a sleep state during a period in which communication is performed using a radio channel associated with a radio channel number that is not assigned to the own node. Therefore, power consumption can be reduced.

  Also, according to the water level observation method of the present embodiment, each observation node Ns is grouped across a plurality of observation areas A based on the concept of a radio channel group, and the water level is round-robin in units of radio channel groups. Observe. Therefore, water level observation can always be performed in the same observation area A. As a result, it is possible to ensure the real-time property of detecting the excess of the warning water level.

  Further, since the water level observation is performed in a round robin manner for each radio channel group, a sleep time can be secured for each observation node Ns. Therefore, a reduction in power consumption by the observation node Ns can be expected.

  In this way, conflicting problems such as real-time observation and power saving can be solved.

  That is, if all the observation nodes Ns repeat sleep and activation at the same timing and in the same cycle, if the cycle is shortened, power consumption increases, and if the cycle is lengthened, the water level observation real time Deteriorates. In this embodiment, such a problem can be solved simultaneously.

  Further, when an excess of the warning water level is detected, the collection cycle is switched to a short cycle. The latest information on the observation basin can be collected at an early stage in a state that requires vigilance.

  Note that the use of the communication method using the route created by the method described in the present embodiment is not limited to the communication of the observation data of the water level. For example, it may be used for communication of other observation information, or may be used for communication such as a smart grid or a smart meter.

  In the present embodiment, the observation node Ns is an example of a first communication device. The aggregation node N0 is an example of a second communication device.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to such specific embodiment, In the range of the summary of this invention described in the claim, various deformation | transformation・ Change is possible.

Regarding the above description, the following items are further disclosed.
(Appendix 1)
A path creation method in a communication system including a plurality of first communication devices arranged for each geographically divided area and a second communication device that performs wireless communication with each of the first communication devices,
For each area, the first communication devices belonging to the area are assigned to at least one first communication device so that the radio channel numbers do not overlap in the area or in the area. And assigning any one of a plurality of radio channel numbers to each of the first communication devices belonging to the area,
The second communication device and each of the first communication devices are synchronously switched in order to switch the wireless channel used for each wireless channel number, and the second communication device and a switching destination wireless channel number are assigned. A path creation method for executing a process of creating a path between each of the first communication devices.
(Appendix 2)
In the process of creating the route, the first communication device to which the wireless channel number of the switching destination is not assigned is a message from the second communication device that uses the route of the wireless channel related to the wireless channel number. The route creation method according to supplementary note 1, wherein the route is set so as not to transfer a message from the second communication device to the other first communication device using the route.
(Appendix 3)
When each first communication device cannot communicate with the second communication device using the wireless channel associated with the wireless channel number assigned to the first communication device, the first communication device 3. The route creation method according to appendix 2, wherein communication with the second communication device is performed using radio channels associated with different radio channel numbers.
(Appendix 4)
The first communication device group to which the same radio channel number is assigned communicates in a cycle that is synchronous and has a deviation from the first communication device group to which another radio channel number is assigned. 4. The route creation method according to any one of appendices 1 to 3, wherein the transition to an impossible power saving state and the return from the power saving state are repeated.
(Appendix 5)
Each of the first communication devices observes the state of the observation target in a state of returning from the power saving state,
The second communication device collects observation results from the first communication devices from the first communication devices in a first period,
The route creation method according to supplementary note 4, wherein when the second communication device detects that the observation target is in a predetermined state based on the observation result, the second cycle is shortened.
(Appendix 6)
The assigning process is:
In order for each area, assign a radio channel number to each first communication device,
Each of the first communication devices is assigned to the first communication device upon completion of the assignment of radio channel numbers to all the first communication devices in the area to which the first communication device belongs. Send a message with a specified radio channel number,
Each first communication device belonging to an area in which assignment of a radio channel number to each first communication device is executed later than another area includes the first communication device belonging to the other area. The route creation method according to any one of supplementary notes 1 to 5, wherein any one of the wireless channel numbers specified in the message received by the first communication device is assigned among the transmitted messages.
(Appendix 7)
A communication system including a plurality of first communication devices arranged for each geographically divided area and a second communication device that performs wireless communication with each of the first communication devices,
For each area, the first communication devices belonging to the area are assigned to at least one first communication device so that the radio channel numbers do not overlap in the area or in the area. And assigning any one of a plurality of radio channel numbers to each of the first communication devices belonging to the area,
The second communication device and each of the first communication devices are synchronously switched in order to switch the wireless channel to be used for each wireless channel number, and the second communication device and a switching destination wireless channel number are assigned. A communication system (4) for creating a route between each of the first communication devices.
(Appendix 8)
The first communication device to which the switch-destination radio channel number is not assigned receives a message from the second communication device that uses the route of the wireless channel related to the wireless channel number and uses the route. The communication system according to appendix 7, wherein a route is set so as not to transfer a message from the second communication device to the other first communication device.
(Appendix 9)
When each first communication device cannot communicate with the second communication device using the wireless channel associated with the wireless channel number assigned to the first communication device, the first communication device 9. The communication system according to appendix 8, wherein communication with the second communication device is performed using radio channels associated with different radio channel numbers.
(Appendix 10)
The first communication device group to which the same radio channel number is assigned communicates in a cycle that is synchronous and has a deviation from the first communication device group to which another radio channel number is assigned. The communication system according to any one of appendices 7 to 9, wherein a transition to an incapable power saving state and a return from the power saving state are repeated.
(Appendix 11)
Each of the first communication devices observes the state of the observation target in a state of returning from the power saving state,
The second communication device collects observation results from the first communication devices from the first communication devices in a first period,
The communication system according to supplementary note 10, wherein the second communication device shortens the first period when detecting that the observation target is in a predetermined state based on the observation result.
(Appendix 12)
In order for each area, assign a radio channel number to each first communication device,
Each of the first communication devices is assigned to the first communication device upon completion of the assignment of radio channel numbers to all the first communication devices in the area to which the first communication device belongs. Send a message with a specified radio channel number,
Each first communication device belonging to an area in which assignment of a radio channel number to each first communication device is executed later than another area includes the first communication device belonging to the other area. The communication system according to any one of appendices 7 to 11, to which any one of the radio channel numbers specified in the message received by the first communication device is assigned among the transmitted messages.

1 Water level observation system 10 Wireless communication device 101 ROM
102 Nonvolatile storage medium 103 RAM
104 CPU
105 Communication Interface 121 Connection Request Transmitting Unit 122 Connection Response Confirming Unit 123 Channel Change Notification Transmitting Unit 124 Route Creation Request Processing Unit 125 Route Creation Unit 126 Observation Data Requesting Unit 127 Observation Data Response Processing Unit 128 Sleep Command Transmitting Unit 129 Water Level Exceeding Notification Processing Unit 130 collection cycle switching notification unit 131 processing time setting unit 141 radio group information storage unit 142 route information storage unit 143 cycle information storage unit 201 connection request processing unit 202 connection response transmission unit 203 ch arbitration request transmission unit 204 ch arbitration request processing unit 205 ch arbitration unit 206 ch arbitration response transmission unit 207 ch arbitration response processing unit 208 inter-area connection request transmission unit 209 inter-area connection request processing unit 210 route creation request transmission unit 211 route creation request transfer unit 212 ch change processing unit 213 route selection Part 214 Water Level Observation Part 2 5 Observation data response unit 216 Sleep command processing unit 217 Water level excess notification unit 218 Collection cycle switching processing unit 219 Start time setting unit 220 Group switching unit 231 Connection channel information storage unit 232 Path information storage unit A1 to A3 Observation area N0 Aggregation node Ns1 ~ Ns9 observation node

Claims (7)

A path creation method in a communication system including a plurality of first communication devices arranged for each geographically divided area and a second communication device that performs wireless communication with each of the first communication devices,
For each area, the first communication devices belonging to the area are assigned to at least one first communication device so that the radio channel numbers do not overlap in the area or in the area. And assigning any one of a plurality of radio channel numbers to each of the first communication devices belonging to the area,
The second communication device and each of the first communication devices are synchronously switched in order to switch the wireless channel to be used for each wireless channel number, and the second communication device and a switching destination wireless channel number are assigned. A path creation method for executing a process of creating a path between each of the first communication devices.   In the process of creating the route, the first communication device to which the wireless channel number of the switching destination is not assigned is a message from the second communication device that uses the route of the wireless channel related to the wireless channel number. The route creation method according to claim 1, wherein the route is set so that a message is not transferred from the second communication device to the other first communication device using the route.   When each first communication device cannot communicate with the second communication device using the wireless channel associated with the wireless channel number assigned to the first communication device, the first communication device 3. The route creation method according to claim 2, wherein communication with the second communication device is performed using radio channels associated with different radio channel numbers.   The first communication device group to which the same radio channel number is assigned communicates in a cycle that is synchronous and has a deviation from the first communication device group to which another radio channel number is assigned. The route creation method according to any one of claims 1 to 3, wherein a transition to an impossible power saving state and a return from the power saving state are repeated. Each of the first communication devices observes the state of the observation target in a state of returning from the power saving state,
The second communication device collects observation results from the first communication devices from the first communication devices in a first period,
5. The route creation method according to claim 4, wherein the second communication device shortens the first cycle when detecting that the observation target is in a predetermined state based on the observation result. The assigning process is:
In order for each area, assign a radio channel number to each first communication device,
Each of the first communication devices is assigned to the first communication device upon completion of the assignment of radio channel numbers to all the first communication devices in the area to which the first communication device belongs. Send a message with a specified radio channel number,
Each first communication device belonging to an area in which assignment of a radio channel number to each first communication device is executed later than another area includes the first communication device belonging to the other area. The route creation method according to any one of claims 1 to 5, wherein any one of the wireless channel numbers specified in the message received by the first communication device is assigned among the transmitted messages. A communication system including a plurality of first communication devices arranged for each geographically divided area and a second communication device that performs wireless communication with each of the first communication devices,
For each area, the first communication devices belonging to the area are assigned to at least one first communication device so that the radio channel numbers do not overlap in the area or in the area. And assigning any one of a plurality of radio channel numbers to each of the first communication devices belonging to the area,
The second communication device and each of the first communication devices are synchronously switched in order to switch the wireless channel to be used for each wireless channel number, and the second communication device and a switching destination wireless channel number are assigned. A communication system for creating a route between each of the first communication devices.

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