DESCRIPTION

COMMUNICATIONS SYSTEM

Field

[0001] The present invention relates to a communications system that includes a mesh network used in an automated meter reading system for electric power.

Background

[0002] In a conventional wireless mesh (referred to as "mesh" in the present specification, although there are other designations such as ad-hoc and multi-hop) communication technique, when a wireless terminal newly enters into a wireless mesh network, a wireless terminal, which desires to enter, determines the state of a communication route, based on information such as received signal strength, consumed power, security level, and interference wave immunity characteristics in wireless communication between a correspondent wireless terminal and a base station, and enters into a network in which the communication quality and the transmission rate become optimum (for example, see Patent Literature 1).

[0003] Furthermore, as an application example of the wireless mesh communication technique, an automated meter reading system that performs automated meter reading of electric power by using the wireless mesh communication technique has been known. In a conventional automated meter reading system, a wireless communication device is mounted on electric power, gas, and water meters installed in respective houses of consumers such as free-standing houses and apartment buildings. The communication devices mounted on the meters transmit the meter reading data such as quantities of electric power, gas, and water acquired from the meters to a high-order system (a meter-reading data management device or a business management device) directly or via another peripheral communication device. Because the automated meter reading system is a wide-area and large-scale system, a gateway (also referred to as a "concentrator" or "aggregate device"; however, it is referred to as a "gateway" in the present specification) is installed on a power pole, to consolidate the meter reading data in a step-by-step manner. When data is transmitted from each house, it has been proposed to apply a mechanism such as a routing function by wireless mesh communication, thereby collecting the meter reading data efficiently (for example, see Non Patent Literature 1). The meter mounted with a communication device (communication function) is referred to as a "smart meter".

Citation List

Patent Literature

[0004] Patent Literature 1: Japanese Patent Application

Laid-open No. 2003-324443

Non Patent Literature

[0005] Non Patent Literature 1: GOTODA et al., "Advanced metering infrastructure (AMI) solution integrating system controls with information exchange technology", Hitachi Hyoron, August 2010, pages 34-37

Summary

Technical Problem

[0006] In the conventional automated meter reading system that applies the wireless mesh communication technique, the state of the communication route is determined to select a wireless mesh network to enter. However, the meter reading system had a problem that balancing of the number of meters (smart meters) accommodated in each gateway, that is, load distribution between the gateways is not taken into consideration.

[0007] The present invention has been achieved to solve the above problem. An object of the present invention is to provide a communications system for realizing a mesh network that can autonomously perform load distribution between gateways by balancing the number of smart meters accommodated in each gateway.

Solution to Problem

[0008] The present invention is directed to a communications system. The communications system includes a plurality of wireless mesh networks. Each wireless mesh network is formed by a single gateway and at least one node accommodated in the gateway, and the node is installed in a consumer's house to measure usage of at least one of electric power, gas, and water. The communications system includes further includes a management server that manages number of nodes accommodated in each of the gateways, and collects and manages measurement results by the nodes. When having detected activation of a gateway, the management server determines nodes that are caused to change an entry-destination wireless mesh network, based on the number of nodes accommodated in each gateway as a management target and position information of each node, and instructs each of the determined nodes to change the entry-destination wireless mesh network to a wireless mesh network managed by the activated gateway.

Advantageous Effects of Invention

[0009] In the communications system according to the present invention, when having detected activation of a gateway, a management server instructs a part of smart meters accommodated in a gateway adjacent to the activated gateway to change an entry destination to a wireless mesh network managed by the activated gateway. Accordingly, balancing of the number of smart meters accommodated in the gateways, that is, load distribution between the gateways can be autonomously performed.

Brief Description of Drawings

[0010] FIG. 1 is a configuration example of a communications system according to the present invention.

FIG. 2A is a sequence diagram of an operation example when loads between gateways are adjusted in the communications system according to a first embodiment.

FIG. 2B is a sequence diagram of a load adjusting operation between gateways in the communications system according to the first embodiment.

FIG. 2C is a sequence diagram of the load adjusting operation between gateways in the communications system according to the first embodiment.

FIG. 2D is a sequence diagram of the load adjusting operation between gateways in the communications system according to the first embodiment.

FIG. 3 is a sequence diagram of the load adjusting operation between gateways in the communications system according to the first embodiment.

FIG. 4 depicts a control operation in a communications system according to a second embodiment.

FIG. 5 depicts a control operation in a communications system according to a third embodiment.

FIG. 6A depicts a control operation in a communications system according to a fourth embodiment.

FIG. 6B depicts the control operation in the communications system according to the fourth embodiment.

FIG. 6C depicts the control operation in the communications system according to the fourth embodiment.

Description of Embodiments

[0011] Exemplary embodiments of a communications system according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.

[0012] First embodiment

FIG. 1 is a configuration example of a communications system according to the present invention. The communications system according to the present invention includes server devices 1 and 2, a gateway 10 (hereinafter, also referred to as a "GW#1"), a gateway 20 (hereinafter, also referred to as a "GW#2"), a gateway 30 (hereinafter, also referred to as a "GW#3"), which are connected to these server devices via a wide area network 3, and a plurality of smart meters 101 to 109 and 201 to 209 that are directly or indirectly connected to the gateway 10, 20, or 30. The respective gateways form a wireless mesh network together with the smart meters under management thereof.

[0013] In the communications system shown in FIG. 1, the server device 1 collects meter reading data such as quantities of electric power, gas, or water from smart meters (smart meters having entered into the wireless mesh network) via the gateway 10, 20, or 30. The server device 2 manages the route and the state (the number of smart meters accommodated in each gateway, and an installation position of each smart meter) in each wireless mesh network. The respective gateways (GW#1, GW#2, and GW#3) connect the wireless mesh network formed together with the smart meters under management thereof to the wide area network 3. The respective smart meters (the smart meters 101 to 109 and 201 to 209) have a function of connecting to other smart meters or gateways by wireless communication and a function of measuring the usage of electric power, gas, and water (meter reading function). In the meter reading function, at least one of the usage of electric power and the like is measured. The smart meters 101 to 109 perform bidirectional data communication with the server devices 1 and 2 via the gateway 10 (GW#1). The smart meters 201 to 209 perform bidirectional data communication with the server devices 1 and 2 via the gateway 20 (GW#2) . In FIG. 1, the GW#3 is in a state immediately after being activated, and it is assumed that there is no smart meter under management of the GW#3 (there is no smart meter having entered into the wireless mesh network managed by the GW#3). In FIG. 1, dotted lines connecting the respective gateways and smart meters, and dotted lines connecting the smart meters indicate communication routes of the wireless mesh network.

[0014] It is assumed that a wireless communication function of the smart meter complies with any one of or a plurality of specified lower power radio, wireless LAN
(Local Area Network) (IEEE 802.11),and ZigBee (IEEE 802.15.4). Because the server devices 1 and 2 have different functions, the server devices are individual devices. However, one server device can be used that has a collection function of the meter reading data and a management function of the route and state in the wireless mesh network. The wide area network 3 is a network between the respective gateways and the respective server devices, and is a wireless wide area network for mobile phones, or a wired wide area network using an optical fiber or a telephone line (a modem or an ADSL (Asymmetric Digital Subscriber Line)).

[0015] In the communications system having such a configuration, the server device 2 (hereinafter, referred to as a "network management server 2" to distinguish it from the server device 1) monitors the states of the smart meters accommodated in the respective gateways to determine whether processing loads need to be adjusted between the gateways. When having determined that adjustment is necessary, the network management server 2 adjusts the loads by shifting a part of smart meters accommodated in any of the wireless mesh networks to an adjacent wireless mesh network (by changing an entry destination). Operations for adjusting the processing loads between the gateways are explained below in detail.

[0016] FIGS. 2A to 2D and FIG. 3 are sequence diagrams of an operation example when the loads are adjusted between the gateways in the communications system according to a first embodiment. FIGS. 2A to 2D depict operation sequences when the smart meters having entered into the wireless mesh network of the gateway 10 (GW#1) are caused to re-enter into the wireless mesh network of the adjacent gateway 30 (GW#3) to switch the entry-destination wireless mesh network. FIG. 3 depicts an operation sequence when the smart meters having entered into the wireless mesh network of the gateway 20 (GW#2) are caused to re-enter into the wireless mesh network of the adjacent gateway 30 (GW#3) to switch the entry-destination wireless mesh network.

[0017] As shown in FIG. 2A, when the GW#3 is newly installed or is recovered from a device fault, the GW#3 first transmits an activation completion notification message indicating activation completion of the device to the network management server 2 (Step S101). Upon reception of the activation completion notification message, the network management server 2 adds the gateway (GW#3), which is a sender of the message, to the gateways under management thereof, to start state management (monitoring of the load condition), and returns an activation completion response message (Step S102).

[0018] Furthermore, based on the position information of each smart meter having entered into the respective wireless mesh networks of the GW#1 and GW#2 adjacent to the newly activated GW#3 and the number of smart meters in the GW#1 and GW#2 (the number of smart meters accommodated in the GW#1 and the number of smart meters accommodated in the GW#2), so as to balance the number of smart meters accommodated in the respective gateways, the network management server 2 selects smart meters to re-enter into the wireless mesh network of the GW#3 and determines the re-entry order (Step S103). The re-entry order is such that a smart meter that can directly enter into the wireless mesh network of the GW#3 is the first, and a smart meter that can enter via the first smart meter is the second. The third and thereafter are determined in the same manner. Re-entry of all the smart meters selected to re-enter should be executed efficiently.

[0019] It is assumed here for explanations that the network management server 2 selects a smart meter 102 that can be connected to the GW#3 (the smart meter 102 installed at a position capable of communicating with the GW#3), a smart meter 106 that can be connected to the smart meter 102, and a smart meter 107 that can be connected to the smart meter 106, and determines that these smart meters are caused to re-enter into the wireless mesh network of the GW#3 in order of the smart meters 102>106->107. At Step S103, the number of smart meters of the gateway (GW#1), in which the selected smart meters have been accommodated, is also updated.

[0020] Upon completion of the processing at Step S103, at Step S104, a switching operation of the entry destination is performed. In this switching operation, with respect to the smart meters 102, 106, and 107 selected at Step S103, the network management server 2 transmits a re-entry instruction message including a gateway ID (=#3) of the gateway indicating the re-entry destination wireless mesh network and an entry start time, sequentially in order from the smart meter having a late entry order (a start time) (Steps S105 to S107) .

[0021] The smart meters 102, 106, and 107 having received the re-entry instruction message perform an adjacency search operation (Steps S108, S120, S132) , respectively, for entering into the wireless mesh network, according to the instructed entry start time.

[0022] If the entry start time is not specified in the re-entry instruction message, for example, an entry operation may be performed at the same timing by the respective smart meters instructed to re-enter. In this case, the re-entry operation of the smart meters 106 and 107 may not be performed successfully until the re-entry, operation of the smart meter 102 completes, due to a position relation between the respective smart meters and the GW#3 that manages the entry-destination wireless mesh network. And the re-entry operation is repeated, thereby unnecessarily increasing the traffic and power consumption. Furthermore, the operation (transmission) of the smart meters 106 and 107 interferes with the communication of the smart meter 102, and processing delay may increase. In the present embodiment, since the network management server 2 determines the entry start time for each smart meter, taking such a case into consideration, respective operations described later are performed efficiently, and the entry destination can be switched in a short time.

[0023] In the adjacency search operation at Step S108, the smart meter 102 instructed to start entry immediately activates a search response message reception-waiting timer, as shown in FIG. 2B, and broadcasts a search request message (Step S109). The broadcast search request message reaches the GW#1 and GW#3 and the adjacent smart meter 106 present within the reach of radio waves of the smart meter 102. The GW#1 and GW#3 put the gateway ID (#1 or #3) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message, respectively and transmit the search response message to the smart meter 102 (Steps S110 and Sill) . The number of hops here is the number indicating how many smart meters are to be passed through from the gateway to the own node. When a smart meter can directly communicate with the gateway, the number of hops is one; when a smart meter passes through one smart meter to the gateway, the number of hops is two; and when a smart meter passes through N smart meters to the gateway, the number of hops is N+l.

[0024] The smart meter 106 has activated an entry start waiting timer to wait for the time until entry start specified in the re-entry instruction message received at Step S106. At this point, because the smart meter 106 is in a state before entry start, the smart meter 106 does not transmit the search response message.

[0025] When the search response message reception-waiting timer has timed out, the smart meter 102 selects a search response message having the smallest number of hops up to the gateway 30 (GW#3) specified in the re-entry instruction message, from one of or a plurality of search response messages received up to that time point, and designates a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Step S112) . In the example shown in FIG. 2B, the GW#3 is designated as the access point to the wireless mesh network to enter.

[0026] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meter 102 restarts the search response message reception-waiting timer, broadcasts a search request message (Step S109), and repeatedly performs this operation (the adjacency search operation) until a search response message can be received.

[0027] When the adjacency search operation at Step S108 (Steps S109 to Sill in FIG. 2B) is performed and selection of the entry destination is complete, the smart meter 102 activates a response waiting timer and transmits an entry registration request message to the GW#3 selected as the access point to the wireless mesh network to enter (Step S113). At this time, at the previous .Step S108 (in the adjacency search operation), when there is another wireless mesh network into which the smart meter 102 can enter (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. The ID (=#1) of the GW#1 is notified here as the ID of the adjacent GW. Although not shown, the entry registration request message includes information required for authentication processing on the gateway side (authentication information).

[0028] If the entry registration response message from the GW#3 cannot be received before the response waiting timer has timed out, the smart meter 102 transmits the entry registration message again. When the entry registration response message from the GW#3 is received before the response waiting timer has timed out, the smart meter 102 stops the response waiting timer.

[0029] The GW#3 authenticates the smart meter 102 by using the authentication information included in the received entry registration request message (Step S114), updates the number of smart meters (Step S115), and transmits an entry registration response message including information indicating that registration is acceptable (OK) to the smart meter 102 (Step S116).

[0030] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 102 having entered into the wireless mesh network of the GW#3 to the network management server 2 (Step S117). The network management server 2 updates the number of smart meters in the GW#3 (Step S118), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the GW#3 (Step S119).

[0031] On the other hand, the smart meter 106 having received the re-entry instruction message at Step S106 activates the entry start waiting timer to wait for the time until entry start specified, and when the timer has timed out, performs the adjacency search operation (Step S120).

[0032] The smart meter 106 stops the operation for entering into the wireless mesh network during the time from activation to time out of the entry start waiting timer.

[0033] In the adjacency search operation at Step S120, the smart meter 106 activates the search response message reception-waiting timer, as shown in FIG. 2C, and broadcasts a search request message (Step S121) . The broadcast search request message reaches the adjacent smart meters 101, 102, and 107 present within the reach of radio waves of the smart meter 106. The smart meters 101 and 102 put the gateway ID (#1 or #3) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message and transmit the search response message to the smart meter 106 (Steps S122 and S123).

[0034] The smart meter 107 has activated the entry start waiting timer to wait for the time until entry start specified in the re-entry instruction message received at Step S105. At this point, because the smart meter 107 is in the state before entry start, the smart meter 107 does not transmit the search response message.

[0035] When the search response message reception-waiting timer has timed out, the smart meter 106 selects a search response message having the smallest number of hops up to the gateway 30 (GW#3) specified in the re-entry instruction message, from one of or a plurality of search response messages received up to that time point, and designates a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Step S124). In the example shown in FIG. 2C, because only the smart meter 102 is connected to the GW#3, the smart meter 102 is designated as the access point to the wireless mesh network to enter.

[0036] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meter 106 restarts the search response message reception-waiting timer, broadcasts a search request message (Step S121), and repeatedly performs this operation (the adjacency search operation) until a search response message can be received.

[0037] When the adjacency search operation at Step S120 (Steps S121 to S124 in FIG. 2C) is performed and selection of the entry destination is complete, the smart meter 106 activates the response waiting timer and transmits an entry registration request message to the GW#3 that manages the entry-destination wireless mesh network via the smart meter 102 selected as the access point to the wireless mesh network to enter (Step S125). At this time, at the previous Step S120 (the adjacency search operation), when there is another wireless mesh network into which the smart meter 106 can enter (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. The ID (#1) of the GW#1 is notified here as the ID of the adjacent GW.

[0038] If the entry registration response message from the GW#3 cannot be received before the response waiting timer is timed out, the smart meter 106 transmits the entry registration message again. When the entry registration response message from the GW#3 is received before the response waiting timer is timed out, the smart meter 106 stops the response waiting timer.

[0039] The GW#3 authenticates the smart meter 106 by using the authentication information included in the received entry registration request message (Step S126), updates the number of smart meters (Step S127), and transmits an entry registration response message including the information indicating that registration is acceptable
(OK) to the smart meter 106 (Step S128).

[0040] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 106 having entered into the wireless mesh network of the GW#3 to the network management server 2 (Step S129). The network management server 2 updates the number of smart meters in the GW#3 (Step S130), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the GW#3 (Step S131).

[0041] On the other hand, the smart meter 107 having received the re-entry instruction message at Step S105 activates the entry start waiting timer to wait for the time until entry start specified, and when the timer is timed out, performs the adjacency search operation (Step S132) .

[0042] The smart meter 107 stops the operation for entering into the mesh network during the time from activation to time out of the entry start waiting timer.

[0043] In the adjacency search operation at Step S132, the smart meter 107 activates the search response message reception-waiting timer, as shown in FIG. 2D, and broadcasts a search request message (Step S133). The broadcast search request message reaches the adjacent smart meters 102 and 106 present within the reach of radio waves of the smart meter 107. The smart meters 102 and 106 put the gateway ID (#3) indicating the entry-destination wireless mesh network and the number of hops to the gateway on the search response message and transmit the search response message to the smart meter 107 (Steps S134 and S135) .

[0044] When the search response message reception-waiting timer has timed out, the smart meter 107 selects a search response message having the smallest number of hops up to the gateway 30 (GW#3) specified in the re-entry instruction message, from one of or a plurality of search response messages received up to that time point, and designates a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Step S136). In the example shown in FIG. 2D, because the smart meter 102 has the smallest number of hops up to the GW#3, the smart meter 102 is designated here as the access point to the wireless mesh network to enter.

[0045] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meter 107 restarts the search response message reception-waiting timer, broadcasts a search request message (Step S133), and repeatedly performs this operation (the adjacency search operation) until a search response message can be received.

[0046] When the adjacency search operation at Step SS132
(Steps S133 to S136 in FIG. 2D) is performed and selection of the entry destination is complete, the smart meter 107 activates the response waiting timer and transmits an entry registration request message to the GW#3 that manages the entry-destination wireless mesh network, via the smart meter 102 selected as the access point to the wireless mesh network to enter (Step S137). At this time, at the previous Step S132 (the adjacency search operation), when there is another wireless mesh network into which the smart meter 107 can enter (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. Because there is no accessible wireless mesh network here, the ID of the adjacent GW is not notified.

[0047] If the entry registration response message from the GW#3 cannot be received before the response waiting timer is timed out, the smart meter 107 transmits the entry registration message again, and when the entry registration response message from the GW#3 is received before the response waiting timer is timed out, the smart meter 107 stops the response waiting timer.

[0048] The GW#3 authenticates the smart meter 107 by using the authentication information included in the received entry registration request message (Step S138), updates the number of smart meters (Step S139), and transmits an entry registration response message including the information indicating registration is acceptable (OK) to the smart meter 107 (Step S140).

[0049] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 107 having entered into the wireless mesh network of the GW#3 to the network management server 2 (Step S141). The network management server 2 updates the number of smart meters in the GW#3 (Step S142), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the GW#3 (Step S143).

[0050] The operation described above is a control operation when the network management server 2 determines that the processing loads need to be adjusted between the gateways and shifts a part of smart meters in the GW#1 to the adjacent GW#3 (to change the entry destination). Specifically, the operation described above is an operation to switch the entry destination of the smart meters 102, 106, and 107, among the smart meters in the wireless mesh network of the GW#1 in a high load condition, to the wireless mesh network of the adjacent GW#3. Furthermore, a control operation when a part of the smart meters in the GW1 is shifted to the adjacent GW#3 is shown in FIG. 3. FIG. 3 depicts an operation when the entry destination of the smart meters 201, 204, and 205, among the smart meters in the wireless mesh network of the GW#2, is switched to the wireless mesh network of the adjacent GW#3. Because the operations of the network management server 2, the respective gateways (GW#1, GW#2, and GW#3), and the respective smart meters (the smart meters 201, 204, and 205) that switch the entry destination are identical to those shown in FIG. 2, explanations thereof will be omitted.

[0051] As described above, in the present embodiment, when the network management server detects activation of a gateway and adds this gateway as a management target, the network management server instructs a part of the smart meters accommodated in a gateway adjacent to the activated gateway, among the respective smart meters having entered into the wireless mesh network of each gateway, to re-enter into the adjacent wireless mesh network, that is, the wireless mesh network managed by the activated gateway (to change the entry destination), so that the number of smart meters accommodated in each gateway as the management target is balanced. Furthermore, the network management server also instructs the entry start time, which is a timing to perform the re-entry operation. Accordingly, because the entry registration is performed again at the specified timing, each smart meter instructed to re-enter can perform an entry-destination change sequence efficiently. Balancing of the number of smart meters to be accommodated in the gateways, that is, load distribution between the gateways, can be achieved autonomously.

[0052] Second embodiment

A second embodiment is explained next. The configuration of a communications system of the present embodiment is explained on the assumption that it is identical to that of the first embodiment (see FIG. 1).

FIG. 4 is an explanatory diagram of a control operation in the communications system according to the second embodiment. As in the first embodiment, a control operation when the GW#3 is newly activated is explained.

[0053] In the communications system according to the present embodiment, as an operation before the GW#3 is newly installed or is recovered from a device fault, each gateway activates a regular meter-reading value collection timer in order to collect the regular meter-reading values, as shown in FIG. 4, and transmits a meter-reading data request message including an adjacency search request to each smart meter accommodated therein at a certain interval (Steps S201 and S211). That is, when the regular meter-reading value collection timer has timed out, the gateway transmits the meter-reading data request message including the adjacency search request. Although details thereof are described later, after having received a response message with respect to the meter-reading data request message and notified the search result acquired as a result thereof to the network management server 2, the gateway restarts the regular meter-reading value collection timer. FIG. 4 depicts transmission and reception operations of the meter-reading data request message and the meter-reading data response message while focusing on the GW#1 and the smart meter 102. However, the operation between the GW#1 and other smart meters and the operation between other gateways and the smart meters are the same.

[0054] The smart meter 102 having received the meter-reading data request message performs the adjacency search operation (Step S202) . In the adjacency search operation, the smart meter 102 first activates a search response message reception-waiting timer, and broadcasts a search request message (Step S203) . The broadcast search request message reaches the adjacent smart meter 106 and the GW#1 present within the reach of radio waves of the smart meter 102. The smart meter 106 and the GW#1 put the gateway ID (#1) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message and transmit the search response message to the smart meter 102 (Steps S204 and S205).

[0055] Once the search response message reception-waiting timer has timed out, the smart meter 102 extracts as a search result a set of the gateway ID indicating the wireless mesh network and the number of hops, based on one of or a plurality of search response messages received up to that time point, and transmits a meter-reading data response message including the regular meter-reading values (electric power usage (kWh) at a certain interval) and the search result to the GW#1 (Step S206).

[0056] The GW#1 having received the meter-reading data response message including the regular meter-reading values (electric power usage (kWh) at a certain interval) and the search result transmits a search notification message including the search result to the network management server 2 (Step S207). The network management server 2 holds the search result of the smart meter 102 (Step S208) .

[0057] In a state where the collecting operation of the regular meter-reading values being regularly performed, when the GW#3 is newly installed or is recovered from a device fault, the GW#3 transmits an activation completion notification message indicating activation completion of the device to the network management server 2 (Step S209) . The network management server 2 transmits an activation completion response message to the GW#3 (Step S210).

[0058] After having transmitted the search notification message to the network management server 2 at Step S207, the GW#1 activates a regular meter-reading value collection timer, and when the timer has timed out, transmits a meter-reading data request message including an adjacency search request to the smart meter 102 again (Step S211).

[0059] The smart meter 102 having received the meter-reading data request message at Step S211 performs the adjacency search operation, as in the case of receiving the meter-reading data request message at Step S201 (Step S212). That is, the smart meter 102 activates the search response message reception-waiting timer, and broadcasts a search request message (Step S213) .

[0060] The broadcast search request message reaches the adjacent smart meter 106 and the GW#1 present within the reach of radio waves of the smart meter 102 and also the GW#3 having been activated. The smart meter 106, the GW#1, and GW#3 put the gateway ID (#1, #3) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message and transmit the search response message to the smart meter 102 (Steps S214 to S216).

[0061] When the search response message reception-waiting timer has timed out, the smart meter 102 extracts as a search result a set of the gateway ID indicating the wireless mesh network and the number of hops, based on one of or a plurality of search response messages received up to that time point, and transmits a meter-reading data response message including the regular meter-reading values (electric power usage (kWh) at a certain interval) and the search result to the GW#1 (Step S217).

[0062] The GW#1 having received the meter-reading data response message including the regular meter-reading values (electric power usage (kWh) at a certain interval) and the search result transmits a search notification message including the search result to the network management server 2 (Step S218). The network management server 2 holds the search result of the smart meter 102 (Step S219).

[0063] Because each gateway perform the operation (the adjacency search operation at Step S202) described above and notifies the network management server 2 of the search result, the network management server 2 can acquire the search result acquired by each smart meter, and can ascertain the reachability in the wireless communication between the smart meters having entered into each wireless mesh network in the communications system. That is, the network management server 2 can ascertain an adjacent smart meter that can be connected (that can perform direct wireless communication) for each smart meter.

[0064] Thereafter, as explained in the first embodiment, the network management server 2 determines whether to adjust the loads between the gateways. When the switching operation of the entry-destination wireless mesh network of the smart meters (the operation corresponding to Step S104 in FIG. 2A and Step S144 in FIG. 3) is to be performed, the network management server 2 performs selection of the smart meters that are caused to re-enter into the wireless mesh network of the GW#3 and determination of the re-entry order of the selected smart meters, taking into consideration not only the position information of each smart meter but also the adjacency search result (the reachability in the wireless communication between the smart meters).

[0065] After the selection of the smart meters that are caused to re-enter into the wireless mesh network of the GW#3 and the determination of the re-entry order have been complete, operations of causing the selected smart meters to re-enter into the adjacent wireless mesh network (the wireless mesh network of the GW#3) are identical to those explained in the first embodiment (Step S104 in FIG. 2A and Step S144 in FIG. 3).

Thus explanations thereof will be omitted.

[0066] As described above, in the present embodiment, each gateway transmits a regular meter-reading value request message including an adjacency search request at a certain interval. Upon reception of the regular meter-reading value request message including the adjacency search request, each smart meter performs adjacency search, and transmits the adjacency search result to the gateway together with the meter reading data. The gateway transfers the adjacency search results received from the smart meters accommodated therein to the network management server. The network management server ascertains the reachability in the wireless communication between the smart meters, based on the received adjacency search result. Furthermore, when adjusting the loads between the gateways, the network management server selects the smart meters that are caused to change the entry-destination wireless mesh network and determines the order to change the entry destination, based on the position information of the respective smart meters and the reachability in the wireless communication between the smart meters. Accordingly, the selected smart meters can re-enter into the adjacent wireless mesh network reliably and efficiently, thereby autonomously achieving balance of the number of smart meters accommodated in respective gateways, that is, load distribution between the gateways.

[0067] Third embodiment

A third embodiment is explained next. The configuration of a communications system of the present embodiment is explained on the assumption that it is identical to that of the first embodiment (see FIG. 1).

FIG. 5 is an explanatory diagram of a control operation in a communications system according to the third embodiment. As in the first and second embodiments, a control operation when the GW#3 is newly activated is explained.

[0068] As shown in FIG. 5, when the GW#3 is newly installed or is recovered from a device fault, the GW#3 first transmits an activation completion notification message indicating activation completion of the device to the network management server 2 (Step S301). The gateway according to the present embodiment (GW#3 in the example shown in FIG. 5) adds an activation reason (newly installation or recovery from a device fault) to the activation completion notification and transmits the activation completion notification. In the example shown in FIG. 5, the GW#3 transmits the activation completion notification message that includes the activation reason indicating recovery from a fault. Upon reception of the activation completion notification message, the network management server 2 adds the gateway (GW#3), which is a sender of the message, to the gateways under management thereof, to start state management (monitoring the load condition), and returns an activation completion respohs.e message (Step S302).

[0069] The network management server 2 confirms the activation reason of the GW#3 (Step S303) . When the GW#3 is newly installed (new installation at Step S303), the network management server 2 reads the position information of the respective smart meters in the wireless network of the GW#1 and GW#2 adjacent to the GW#3 (Step S305). On the other hand, when the GW#3 is recovered from a device fault (fault recovery at Step S303), the network management server 2 reads the information of the respective smart meters, which had been in the wireless network of the GW#3 (that is, the smart meters, which had been accommodated in the GW#3 before occurrence of the device fault) (Step S304).

[0070] After performing Step S304 or S305, so as to balance the number of smart meters accommodated in the respective gateways, based on the read information (position information of each smart meter accommodated in the gateway adjacent to the GW#3 or information of each smart meter that was accommodated in the GW#3), the network management server 2 selects smart meters that are caused to re-enter into the wireless mesh network of the GW#3 and determines the re-entry order (Step S306).

[0071] After the selection of the smart meters that are caused to re-enter into the wireless mesh network of the GW#3 and the determination of the re-entry order have been complete, the operation of causing the selected smart meters to re-enter into the adjacent wireless mesh network (the wireless mesh network of the GW#3) is identical to the operation explained in the first embodiment (Step S104 in FIG. 2A and Step S144 in FIG. 3). Thus explanations thereof will be omitted.

[0072] As described above, in the present embodiment, when the respective gateways are activated due to new installation or fault recovery, the gateways first add the activation reason to the activation completion notification message and transmit the activation completion notification message. When the activation reason is recovery from a device fault, the network management server 2 performs selection of the smart meters that are caused to change the entry-destination wireless network and determination of the order to change the entry destination, based on the information of the smart meters accommodated in the past (before occurrence of the fault) in the activated gateway. When the activation reason is new installation, the network management server 2 performs selection of the smart meters that are caused to change the entry-destination wireless network and determination of the order to change the entry destination, based on the position information of the smart meters accommodated in the gateway adjacent to the activated gateway. Accordingly, the selected smart meters can re-enter into the adjacent wireless mesh network reliably and efficiently. Balancing of the number of smart meters to be accommodated in the respective gateways, that is, load distribution between the gateways can be achieved autonomously.

[0073] In the explanations above, the activated gateway notifies the network management server of the activation reason, and based on the notification content, the network management server determines whether activation reason is recovery from a device fault. However, the network management server can determine the activation reason without the notification of the activation reason. That is, upon reception of the activation completion notification, the network management server confirms whether the information of the gateway (information of the smart meters accommodated therein), which has transmitted the notification, is held therein. When the network management server holds the information, the network management server can determine the gateway as a gateway recovered from a device fault.

[0074] Fourth embodiment

A fourth embodiment is explained next. The configuration of a communications system of the present embodiment is explained on the assumption that it is identical to that of the first embodiment (see FIG. 1). FIGS. 6A to 6C are explanatory diagrams of a control operation in a communications system according to the fourth embodiment. As in the first embodiment, a control operation when the GW#3 is newly activated is explained. FIG. 6A depicts an operation of a smart meter at the first hop from the GW#3 (the smart meter that can be connected directly to the GW#3). FIG. 6B depicts an operation of a smart meter at the second hop from the GW#3 (the smart meter that can be connected to the GW#3 via one smart meter). FIG. 6C depicts an operation of a smart meter at the third hop from the GW#3 (the smart meter that can be connected to the GW#3 via two smart meters).

[0075] When the GW#3 is newly installed, or is recovered from a device fault, as shown in FIG. 6A, the GW#3 first transmits an activation completion notification message indicating activation completion of the device to the network management server 2 (Step S401) . Upon reception of the activation completion notification message, the network management server 2 adds the gateway (GW#3), which is a sender of the message, to the gateways under management thereof, to start state management (monitoring the load condition), and returns an activation completion response message (Step S402).

[0076] Upon reception of the activation completion response message, the GW#3 activates a notification information transmission timer indicating operation start (hereinafter, "operation-start notification information transmission timer"), and broadcasts a notification information message in which the number of hops is set to one (Step S403) . The notification information message includes identification information of the sender device GW#3 and information indicating that the sender device has started an operation. Only the smart meters 102 and 201 at the first hop from the GW#3 receive the broadcast notification information message, and perform the adjacency search operation, respectively (Steps S404 and S416). Because the number of hops in the notification information message is one, the respective smart meters having received the notification information message do not transfer the received message.

[0077] In the adjacency search operations at Steps S404 and S416, the smart meters 102 and 201 activate a search response message reception-waiting timer, respectively, and broadcast a search request message (Steps S405 and S417) . The search request message broadcast from the smart meter 102 reaches the GW#1 and the GW#3 present within the reach of radio waves of the smart meter 102. The GW#1 and the GW#3 put the gateway ID (#1 or #3) indicating the entry-destination wireless mesh network and the number of hops to the gateway on the search response message, respectively, and transmit the search response message to the smart meter 102 (Steps S406 and S407). Similarly, the search request message broadcast from the smart meter 201 reaches the GW#2 and the GW#3 present within the reach of radio waves of the smart meter 201. The GW#2 and the GW#3 put the gateway ID (#2 or #3) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message, respectively, and transmit the search response message to the smart meter 201 (Steps S418 and S419).

[0078] When the search response message reception-waiting timer has timed out, the smart meters 102 and 201 each select a search response message having the smallest number of hops up to the gateway 30 (GW#3), which is the sender of the notification information message received at Step S403, from one of or a plurality of search response messages received up to that time point, and designate a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Steps S408 and S420). In the example shown in FIG. 6A, the smart meters 102 and 201 designate the GW#3 as the access point to the wireless mesh network to enter.

[0079] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meters 102 and 201 restart the search response message reception-waiting timer, broadcast a search request message (Steps S405 and S417), and repeatedly perform this operation (the adjacency search operation) until a search response message can be received.

[0080] When the adjacency search operation is performed and selection of the entry destination is complete, the smart meters 102 and 201 each activate a response waiting timer and transmit an entry registration request message to the GW#3 selected as the access point to the wireless mesh network to enter (Steps S409 and S421). At this time, in the previous adjacency search operation (at Steps S404 and S416), when there is another wireless mesh network (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. The smart meter 102 notifies the ID (=#1) of the GW#1 as the ID of the adjacent GW, and the smart meter 201 notifies the ID (=#2) of the GW#2 as the ID of the adjacent GW.

[0081] If the entry registration response message from the GW#3 cannot be received before the response waiting timer is timed out, the smart meters 102 and 201 each transmit the entry registration message again. When the entry registration response message from the GW#3 is received before the response waiting timer is timed out, the smart meters 102 and 201 stop the response waiting timer.

[0082] Upon reception of the entry registration request message from the smart meter 102, the GW#3 authenticates the smart meter 102 by using the authentication information included in the received entry registration request message (Step S410), updates the number of smart meters (Step S411), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the smart meter 102 (Step S412). Similarly, upon reception of the entry registration request message from the smart meter 201, the GW#3 authenticates the smart meter 201 by using the authentication information included in the received entry registration request message
(Step S422), updates the number of smart meters (Step S423), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the smart meter 201 (Step S424).

[0083] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 102 having entered into the wireless mesh network of the GW#3 and a registration request message including the ID of the smart meter 201 having entered therein, respectively, to the network management server 2 (Steps S413 and S425) . The network management server 2 updates the number of smart meters in the GW#3 every time the registration request message is received (Steps S41.4 and S426) , and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the GW#3 (Steps S415 and S427).

[0084] When the operation-start notification information transmission timer activated at the time of performing Step S403 has timed out, the GW#3 adds one to the number of hops and broadcasts the notification information message again (Step S428). At this time, the GW#3 restarts the operation-start notification information transmission timer. The smart meters 102 and 201 present at the first hop from the GW#3 receive the notification information message, and because the number of hops is two, subtract one from the set number of hops to update the number of hops to one, and transfer the notification information message.

[0085] The notification information message transferred from the smart meter 102 or 201 is received by the smart meters 106 and 204 present at the second hop from the GW#3, and the smart meters 106 and 204 each perform the adjacency search operation (Steps S429 and S440 in FIG. 6B).

[0086] In the adjacency search operations at Steps S429 and S440, the smart meters 106 and 201 each activate a search response message reception-waiting timer and broadcast a search request message (Steps S430 and S441). The search request message broadcast from the smart meter 106 reaches the smart meter 102, which is an adjacent smart meter present within the reach of radio waves of the smart meter 106. The smart meter 102 puts the gateway ID (#3) indicating the entry-destination wireless mesh network and the number of hops to the gateway on the search response message, and transmits the search response message to the smart meter 106 (Step S431). Similarly, the search request message broadcast from the smart meter 204 reaches the smart meter 201, which is an adjacent smart meter present within the reach of radio waves of the smart meter 204. The smart meter 201 puts the gateway ID (#3) indicating the entry destination wireless mesh network and the number of hops to the gateway on the search response message, and transmits the search response message to the smart meter 204 (Step S442).

[0087] When the search response message reception-waiting timer has timed out, the smart meters 106 and 204 each select a search response message having the smallest number of hops up to the gateway 30 (GW#3), which is the sender of the notification information message received at Step S428, from one of or a plurality of search response messages received up to that time point, and designates a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Steps S432 and S443) . In the example shown in FIG. 6B, the smart meter 106 assumes the smart meter 102 as the access point to the wireless mesh network to enter, and the smart meter 204 assumes the smart meter 201 as the access point to the wireless mesh network to enter.

[0088] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meters 106 and 204 restart the search response message reception-waiting timer, broadcast a search request message (Steps S430 and S441), and repeatedly perform this operation (the adjacency search operation) until a search response message can be received.

[0089] When the adjacency search operation is performed and selection of the entry destination is complete, the smart meters 106 and 204 each activate a response waiting timer, and transmit an entry registration request message to the GW#3 that manages the entry destination wireless mesh network, via the smart meter selected as the access point to the wireless mesh network to enter (Steps S433 and S444) . At this time, in the previous adjacency search operation (at Steps S429 and S440), when there is another wireless mesh network (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. The smart meter 106 notifies the ID (=#1) of the GW#1 as the ID of the adjacent GW; and the smart meter 204 notifies the ID (=#2) of the GW#2 as the ID of the adjacent GW.

[0090] If the entry registration response message from the GW#3 cannot be received before the response waiting timer is timed out, the smart meters 106 and 204 each transmit the entry registration message again. When the entry registration response message from the GW#3 is received before the response waiting timer is timed out, the smart meters 106 and 204 stop the response waiting timer.

[0091] Upon reception of the entry registration request message from the smart meter 106, the GW#3 authenticates the smart meter 106 by using the authentication information included in the received entry registration request message (Step S434), updates the number of smart meters (Step S435), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the smart meter 106 (Step S436) . Likewise, upon reception of the entry registration request message from the smart meter 204, the GW#3 authenticates the smart meter 204 by using the authentication information included in the received entry registration request message
(Step S445), updates the number of smart meters (Step S446), and transmits an entry registration response message including the information indicating registration is acceptable (OK) to the smart meter 204 (Step S447).

[0092] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 106 having entered into the wireless mesh network of the GW#3 and a registration request message including the ID of the smart meter 204 having entered therein, respectively, to the network management server 2 (Steps S437 and S448) . The network management server 2 updates the number of smart meters in the GW#3 every time the registration request message is received (Steps S438 and S449), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the GW#3 (Steps S439 and S450).

[0093] When the operation-start notification information transmission timer activated at the time of performing Step S428 has timed out, the GW#3 adds one to the number of hops and broadcasts the notification information message again (Step S451) . At this time, the GW#3 restarts the operation-start notification information transmission timer. The smart meters 102 and 201 present at the first hop from the GW#3 receive the notification information message, and because the number of hops is three, subtract one from the set number of hops to update the number of hops to two, and transfer the notification information message. The smart meters 106 and 204 present at the second hop from the GW#3 receive the notification information message transferred from the smart meters at the first hop, and because the number of hops is two, subtract one from the set number of hops to update the number of hops to one, and transfer the notification information message.

[0094] The notification information message transferred from the smart meter 106 or 204 is received by the smart meters 107 and 205 present at the third hop from the GW#3. The smart meters 107 and 205 each perform the adjacency search operation (Steps S452 and S464 in FIG. 6C).

[0095] In the adjacency search operations at Steps S452 and S464, the smart meters 107 and 205 each activate a search response message reception-waiting timer and broadcast a search request message (Steps S453 and S465). The search request message broadcast from the smart meter 107 reaches the smart meter 106, which is an adjacent smart meter present within the reach of radio waves of the smart meter 107. The smart meter 106 puts the gateway ID (#3) indicating the entry-destination wireless mesh network and the number of hops to the gateway on the search response message, and transmits the search response message to the smart meter 107 (Steps S454) . Similarly, the search request message broadcast from the smart meter 205 reaches the smart meter 204, which is an adjacent smart meter present within the reach of radio waves of the smart meter 205. The smart meter 204 puts the gateway ID (#3) indicating the entry-destination wireless mesh network and the number of hops to the gateway on the search response message, and transmits the search response message to the smart meter 205 (Steps S466) .

[0096] When the search response message reception-waiting timer has timed out, the smart meters 107 and 205 each select a search response message having the smallest number of hops up to the gateway 30 (GW#3), which is the sender of the notification information message received at Step S451, from one of or a plurality of search response messages received up to that time point, and designates a smart meter or a gateway that has transmitted the selected message as an access point to the wireless mesh network to enter (Steps S456 and S467). In the example shown in FIG. 6C, the smart meter 107 designates the smart meter 106 as the access point to the wireless mesh network to enter, and the smart meter 205 designates the smart meter 204 as the access point to the wireless mesh network to enter.

[0097] When the search response message reception-waiting timer has timed out, if no search response message has been received, the smart meters 107 and 205 restart the search response message reception-waiting timer, broadcast a search request message (Steps S453 and S465), and repeatedly perform this operation (the adjacency search operation) until a search response message can be received.

[0098] When the adjacency search operation is performed and selection of the entry destination is complete, the smart meters 107 and 205 each activate a response waiting timer and transmit an entry registration request message to the GW#3 that manages the entry-destination wireless mesh network, via the smart meter selected as the access point to the wireless mesh network to enter (Steps S457 and S468). At this time, in the previous adjacency search operation (at Steps S452 and S464), when there is another wireless mesh network into which the smart meters 107 and 205 can enter (a wireless mesh network managed by a GW other than the GW#3), an ID of the GW indicating the other accessible wireless mesh network is notified together. The smart meter 107 notifies the ID (=#1) of the GW#1 as the ID of the adjacent GW, and the smart meter 205 notifies the ID (=#2) of the GW#2 as the ID of the adjacent GW.

[0099] If the entry registration response message from the GW#3 cannot be received before the response waiting timer is timed out, the smart meters 107 and 205 each transmit the entry registration message again. When the entry registration response message from the GW#3 is received before the response waiting timer is timed out, the smart meters 107 and 205 stop the response waiting timer.

[0100] Upon reception of the entry registration request message from the smart meter 107, the GW#3 authenticates the smart meter 107 by using the authentication information included in the received entry registration request message (Step S458), updates the number of smart meters (Step S459), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the smart meter 107 (Step S460). Likewise, upon reception of the entry registration request message from the smart meter 205, the GW#3 authenticates the smart meter 205 by using the authentication information included in the received entry registration request message (Step S469), updates the number of smart meters (Step S470), and transmits an entry registration response message including the information indicating that registration is acceptable (OK) to the smart meter 205 (Step S471) .

[0101] After having transmitted the entry registration response message, the GW#3 transmits a registration request message including the ID of the smart meter 107 having entered into the wireless mesh network of the GW#3 and a registration request message including the ID of the smart meter 205 having entered therein, respectively, to the network management server 2 (Steps S461 and S472). The network management server 2 updates the number of smart meters in the GW#3 every time the registration request message is received (Steps S462 and S473), and transmits an entry registration response message including the information indicating that registration is acceptable (OK)to the GW#3 (Steps S463 and S474) .

[0102] As described above, in the present embodiment, after the respective gateways are activated to start an operation, the respective gateways periodically broadcast the notification information indicating the operation start, so that the notification information is sequentially propagated from the smart meter at the first hop to the smart meter at the next hop, and cause the smart meter to re-select the entry-destination wireless mesh network, sequentially from the smart meter at the first hop. Accordingly, balancing of the number of smart meters accommodated in the respective gateways, that is, load distribution between the gateways can be achieved autonomously.

[0103] In the present embodiment, a case where the entry destination is re-selected by the smart meters up to the third hop from the activated gateway (GW#3) has been explained. However, the range of reselection of the entry destination can be widened or narrowed. Furthermore, reselection of the entry destination can be continuously performed until the network management server determines that the number of smart meters accommodated in the respective gateways is balanced. That is, the network management server instructs the activated gateway to transmit the notification information message indicating an operation start (a notification information message transmitted at Step S403), and updates the number of smart meters in the gateway upon reception of the entry registration request message, and then determines whether the reselection operation of the entry destination is to be continued.

Industrial Applicability

[0104] As described above, the present invention is useful as a communications system including a plurality of wireless mesh networks formed by smart meters, which are nodes having a meter reading function of electric power, and is particularly suitable for a communications system that can achieve load distribution between gateways that accommodate respective wireless mesh networks.

Reference Signs List

[0105] 1 server device
2 server device (network management server)
3 wide area network
10, 20, 30 gateway
101 to 109, 201 to 209 smart meter

CLAIMS

1. A communications system comprising:

a plurality of wireless mesh networks, each wireless mesh network being formed by a single gateway and at least one node accommodated in the gateway, the node being installed in a consumer's house to measure usage of at least one of electric power, gas, and water; and

a management server that manages number of nodes accommodated in each of the gateways, and collects and manages measurement results by the nodes,

wherein when having detected activation of a gateway, the management server determines nodes that are caused to change an entry-destination wireless mesh network, based on the number of nodes accommodated in each gateway as a management target and position information of each node, and instructs each of the determined nodes to change the entry-destination wireless mesh network to a wireless mesh network managed by the activated gateway.

2. The communications system according to claim 1,

wherein the gateway regularly transmits a message for requesting a notification of the measurement results of the usage to each node accommodated therein, causes each node to perform regularly a search operation of an adjacent node by using the message, and notifies the management server of each search result acquired as a result thereof, and

wherein the management server determines nodes that are caused to change the entry-destination wireless mesh network based on the number of nodes accommodated in each gateway as the management target, the position information of each node, and the search result.

3. The communications system according to claim 1,

wherein the activated gateway notifies the management server of an activation reason, and

wherein when the activation reason indicates recovery from a device fault, the management server determines nodes that are caused to change the entry-destination wireless mesh network, based on management information of the gateway, which had been used before occurrence of the fault in the activated gateway.

4. The communications system according to claim 1, wherein the management server instructs each of the selected nodes on a timing to perform an entry destination change operation, thereby causing each node to perform the entry destination change operation at a different timing.

5. The communications system according to claim 4,

wherein the management server causes the nodes to perform the entry-destination change operation in order from a node installed near the activated gateway.

6. A communications system comprising:

a plurality of wireless mesh networks, each wireless mesh network being formed by a single gateway and at least one node accommodated in the gateway, the node being installed in a consumer's house to measure usage of at least one of electric power, gas, and water; and

a management server that manages number of nodes accommodated in each of the gateways, and collects and manages measurement results by the nodes,

wherein after being activated, the gateway instructs the nodes to reselect an entry destination wireless mesh network, in order from a node having a smallest number of hops and adjacent thereto toward a node having a largest number of hops, and causes a part of the nodes accommodated in an adjacent wireless mesh network to enter into a wireless mesh network managed thereby.