DESCRIPTION COMMUNICATIONS SYSTEM

Field

[0001] The present invention relates to a communications system including a mesh network used in an automated meter reading system for electricity or the like. 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 path based on pieces of 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, 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 electricity or the like using the wireless mesh communication technique has been known. In a conventional automated meter reading system, a wireless communication device is mounted on an electricity, gas or water meter installed in each house of consumers such as free-standing houses and apartment buildings, and the communication device mounted on the meter transmits the meter reading data such as a quantity of electricity, gas or water acquired from the meter to a higher-order system (meter-reading data management device, business management device, or the like) 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 "concentrator" or "aggregate device"; however, referred to as "gateway" in the present specification) is installed on a power pole or the like, to consolidate the meter reading data in a step-by-step manner. It has been proposed to apply a mechanism such as a routing function based on wireless mesh communication so as to collect the meter reading data efficiently, when data are transmitted from each house (for example, Non Patent Literature 1). The meter mounted with a communication device (communication function) is referred to as "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 to which the wireless mesh communication technique is applied, the state of the communication path is determined to select a wireless mesh network to enter. However, there has been a problem that balancing of the number of meters (smart meters) functionally accommodated in each gateway, that is, load distribution among the gateways is not taken into consideration.

[0007] The present invention has been achieved in view of the above-mentioned circumstances, and an object of the present invention is to provide a communications system that realizes a mesh network that can autonomously perform load distribution among gateways by balancing the numbers of smart meters functionally accommodated in the gateways. Solution to Problem

[0008] In order to solve the above-mentioned problems and achieve the object, the present invention provides a communications system comprising a plurality of wireless mesh networks each formed by a single gateway and at least one node accommodated in the gateway, which is installed in a consumer's house to measure a usage amount of at least one of electricity, gas and water, and a management server that manages the number of nodes accommodated in each of the gateways, and collects and manages measurement results obtained by the nodes, wherein when the node desires to enter into a wireless mesh network, the node notices information of all the gateways that can be connected to the node and transmits an entry request to one of the gateways that can be connected to the node directly or via another node, and upon reception of the entry request into the own network that is a wireless mesh network managed by the own gateway, the gateway confirms the number of nodes accommodated in the own gateway and the number of nodes accommodated in another gateway that can. be connected to the node having transmitted the entry request, and when there is another gateway having a smaller number of nodes accommodated therein than the number of nodes accommodated in the own gateway, the gateway instructs the node having transmitted the entry request to enter into a wireless mesh network managed by the other gateway.

Advantageous Effects of Invention
[0009] In the communications system according to the present invention, the gateway having received the entry request into the wireless mesh network is responsive to a case where there is an other gateway which has a smaller number of nodes accommodated therein than the number of nodes accommodated in the former gateway and to which a node having transmitted the entry request can be connected, and in the case instructs the node to enter into the wireless mesh network managed by the other gateway. Accordingly, load distribution among gateways can be achieved autonomously. Brief Description of Drawings

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

FIG. 2 is an illustration showing an example of a case when a smart meter newly enters into a wireless mesh network.

FIG. 3 is an explanatory chart of a control operation in a communications system according to a first embodiment.

FIG. 4 is an explanatory chart of a control operation in a communications system according to a second embodiment.

FIG. 5 is an explanatory chart of a control operation in a communications system according to a third embodiment.

FIG. 6 is an explanatory chart of a control operation in a communications system according to a fourth embodiment.

FIG. 7 is an explanatory chart of a control operation in a communications system according to a fifth embodiment.

FIG. 8 is an illustration showing an example of a case when a smart meter newly enters into a wireless mesh network.

FIG. 9 is an illustration showing an example of a case when a smart meter newly enters into a wireless mesh network.

FIG. 10A is an explanatory chart of a control operation in a communications system according to a sixth embodiment.

FIG. 10B is an explanatory chart of a control operation in the communications system according to the sixth embodiment.

FIG. 11 is an explanatory chart of a control operation in a communications system according to a seventh embodiment.

Description of Embodiments
[0011] Embodiments of a communications system according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments. [0012] First embodiment.

FIG. 1 is an illustration showing a configuration example of a communications system according to the present invention. The communications system according to the present invention is configured to include server devices 1 and 2, a gateway 10 (hereinafter, sometimes referred to as "GW#1") and a gateway 20 (hereinafter, sometimes referred to as "GW#2") connected to these server devices via a wide area network 3, and a plurality of smart meters 101 to 113 and 201 to 212 that are directly or indirectly connected to the gateway 10 or 20. Each gateway forms a wireless mesh network together with the smart meters that are subordinate under the gateway.

[0013] In the communications system shown in FIG. 1, the server device 1 collects meter reading data such as the quantities of electricity, gas or water from the smart meters (smart meters having entered into the wireless mesh network) via the gateway 10 or 20. The server device 2 manages paths and states (the number of smart meters accommodated in each gateway, an installation position of each smart meter, and the like) in each wireless mesh network. Each gateway (GW#1, GW#2) connects the wireless mesh network formed together with the smart meters that are subordinate under the gateway to the wide area network 3. The smart meters (smart meters 101 to 113 and 201 to 212) have a function of connecting to other smart meters or gateways by wireless communication and a function of measuring the used amount of electricity, gas, water or the like (meter reading function). In the meter reading function, the used amount is measured in at least one of the electricity and the like. The smart meters 101 to 113 perform bidirectional data communication with the server devices 1 and 2 via the gateway 10 (GW#1). The smart meters 201 to 212 perform bidirectional data communication with the server devices 1 and 2 via the gateway 20 (GW#2). In FIG. 1, dotted lines connecting between the gateways and the smart meters, and dotted lines connecting between the smart meters indicate communication paths of the wireless mesh network.

[0014] A wireless communication function of the smart meter complies with any one of or a plurality of specified low power radio, wireless LAN (Local Area Network) (IEEE 802.11), ZigBee (IEEE 802.15.4), and the like. Because the server devices 1 and 2 have different functions, the server devices are individual devices. However, these server devices may be realized by one server device having a collection function of the meter reading data and a management function of the paths and the states in the wireless mesh network. The wide area network 3 is a network between the gateways and the server devices, and is a wireless wide area network for mobile phones or the like, or a wired-system wide area network using an optical fiber, a telephone line (a modem, an ADSL (Asymmetric Digital Subscriber Line)) and/or the like.

[0015] FIG. 2 is an illustration showing an example a case when a smart meter newly enters into one of the wireless mesh networks included in the communications system shown in FIG. 1. Specifically, it shows a case where a smart meter 301 is newly installed, and is caused to enter into the wireless mesh network under the GW#1 or the wireless mesh network under the GW#2. In FIG. 2, a range of access of radio waves of the smart meter 301 is indicated by a one-dot chain line, and an installation position of the smart meter 301 is a position in which the smart meter 301 can communicate with the smart meter 113 under the GW#1 and the smart meter 212 under the GW#2. FIG. 3 is an explanatory chart of a control operation in the communications system according to a first embodiment. Specifically, FIG. 2 is a sequence diagram showing an example of an operation when the smart meter 301 is newly installed in the position shown in FIG. 2. An operation of the present embodiment (operation when the smart meter 301 newly enters into the wireless mesh network) is explained with reference to FIGS. 2 and 3. In the following explanations, the server device 2 is referred to as "network management server 2" to distinguish it from the server device 1.

[0016] When the smart meter 301 is newly installed, an adjacency search operation (Step S101) is performed to select an entry destination wireless mesh network first. At Step S101, the smart meter 301 initially activates a search response message reception-waiting timer and broadcasts a search request message (Step S102).

[0017] The broadcast search request message reaches the adjacent smart meters 113 and 212 present in the range of access of radio waves of the smart meter 301, and the smart meters 113 and 212 post the gateway ID (#1 or #2) indicating the entry destination wireless mesh network and the number of hops to the gateway, in a search response message, and transmit the search response message to the smart meter 301 (Steps SI03 and SI04). The number of hops here means the number indicating how many smart meters are to be passed through from the gateway to the own node, and when it is possible to directly communicate with the gateway, the number of hops is 1, when it is required to pass through one smart meter, the number of hops is 2, and when it is required to pass through N smart meters, the number of hops is N+l.

[0018] Once the search response message reception-waiting timer has timed out, the smart meter 301 selects a search response message having the smallest number of hops up to the gateway, from one or more search response messages received until that time point (during a period of time from activation of the timer to time out of the timer), and designates a smart meter that is a transmission source of the selected message as an access point to the wireless mesh network to enter. In FIGS. 2 and 3, because the number of hops of the smart meter 113 is the smallest, the smart meter 113 (GW#1 side) is designated as the access point to the wireless mesh network to enter (Step S105). At this time, the GW#2 is handled as an adjacent gateway.

[0019] When there are a plurality of search response messages having the smallest number of hops up to the gateway (when M search response messages are received and from among them N (M>N) search response messages have the same number of hops), a plurality of different selection conditions are provided, including a received signal strength (RSSI (Receive Signal Strength Indicator)) at the time of receiving the message and the like, so that one of the N search response messages can be selected.

[0020] If any search response message has not been received at the time when the search response message reception-waiting timer has timed out, then the search response message reception-waiting timer is activated again, a search request message is broadcast (Step S102), and the operation is repeatedly performed until the search response message can be received.

[0021] When the adjacency search operation at Step S101 (Steps S102 to S105) is performed and selection of the entry destination is completed, the smart meter 301 next activates a response waiting timer and transmits an entry registration request message to the GW#1 that manages the entry destination wireless mesh network via the adjacent smart meter 113 selected as the access point to the wireless mesh network to enter (Step S106). At this time, at the previous Step S101 (in the adjacency search operation), when there is another wireless mesh network into which the smart meter 301 can enter (a wireless mesh network managed by a GW other than the GW#1), an ID of the GW indicating this other accessible wireless mesh network is noticed together. Here, the ID (=#2) of the GW#2 is noticed as an ID of the adjacent GW together therewith. Although not shown in the figure, the entry registration request message includes information required for authentication processing on the gateway side (authentication information).

[0022] If the entry registration response message from the GW#1 cannot be received until the response waiting timer is timed out, the smart meter 301 transmits the entry registration message again, and when the entry registration response message from the GW#1 is received before the response waiting timer is timed out, the smart meter 301 stops the response waiting timer.

[0023] The GW#1 authenticates the smart meter 301 using the authentication information included in the received entry registration request message (Step S107), and compares the number of smart meters having entered into the wireless mesh network, that are managed by the own gateway, that is, the number of smart meters accommodated therein with the number of smart meters accommodated in the adjacent gateway (here, the GW#2) (Step S108). The number of smart meters accommodated in the adjacent GW#2 is managed by the network management server 2, and the GW#1 acquires and holds information on the number of smart meters accommodated in the adjacent gateway beforehand from the network management server 2 (an operation for acquiring the information on the number of smart meters accommodated is described later). In the present example, because the number of smart meters accommodated in the adjacent gateway is small, the GW#1 determines whether or not the smart meter 301 can enter into another wireless mesh network based on the information of the adjacent gateway included in the entry registration request message (Step S109).

[0024] In the authentication at Step S107 (authentication of the smart meter 301), when it is not authenticated, the GW#1 transmits an entry registration response message provided with information of registration being unacceptable (NG).

[0025] When the number of smart meters accommodated in the adjacent GW#2 is small and the smart meter 301 can also enter into the wireless mesh network under the GW#2 (small number of accommodated smart meters at Step S108, YES at Step S109), the GW#1 determines to instruct the smart meter 301 to re-enter into the wireless mesh network (Step S110), and transmits the entry registration response message provided with the ID (=#2) of the GW#2 indicating the re¬entry destination wireless mesh network to the smart meter 301 (Step S112) .

[0026] Meanwhile, when the number of smart meters accommodated in its own gateway (GW#1) is small or is the same as the number of smart meters accommodated in the adjacent GW#2, or when the smart meter having entered into the wireless mesh network cannot enter into another wireless mesh network (for example, when it is determined that the smart meter 301 cannot enter into another wireless mesh network at Step S109 for determining whether or not the smart meter can enter into another wireless mesh network, because an ID of the gateway indicating the adjacent wireless mesh network is not noticed in the entry registration request message), the GW#1 updates the number of accommodated smart meters managed by the own gateway (Step Sill), and transmits the entry registration response message added with the information of registration being acceptable (OK), instead of the entry registration response message transmitted at Step S112.

[0027] The smart meter 301 having been instructed to re-enter into the wireless mesh network in the entry registration response message transmits an entry registration request message to the GW#2 via the adjacent smart meter 212 that is the access point to the indicated wireless mesh network (Step S113).

[0028] Similarly to the GW#1, the GW#2 authenticates the smart meter 301 using the authentication information included in the received entry registration request message (Step S114), and compares the number of smart meters accommodated in its own gateway with the number of smart meters accommodated in the adjacent gateway (GW#1) (Step S115). When the number of smart meters accommodated in the adjacent gateway is small (small number of accommodated smart meters at Step S115), the GW#2 determines whether or not the smart meter 301 can enter into another wireless mesh network based on the information of the adjacent gateway included in the entry registration request message (Step S116). When the smart meter 301 can enter into another wireless mesh network (YES at Step S116), the GW#2 determines to instruct the smart meter 301 to re-enter into the adjacent gateway (Step S117). In this example, because the number of smart meters accommodated in its own gateway is small (large number of smart meters accommodated in the adjacent GW side at Step S115), the GW#2 updates the number of accommodated smart meters (Step S118), and transmits an entry registration response message provided with the information of registration being acceptable (OK) to the smart meter 301 (Step S119).

[0029] After having transmitted the entry registration response message, the GW#2 transmits a registration request message provided with the ID of the smart meter 301 having entered into the wireless mesh network to the network management server 2 (Step S120). The network management server 2 updates the number of smart meters accommodated in the GW#2 (Step S121), and transmits an entry registration response message provided with the number of smart meters accommodated in the adjacent GW#1 that manages the number of accommodated smart meters likewise (the number of smart meters accommodated in the GW#1), and the information of registration being acceptable (OK), to the GW#2 (Step S122) .

[0030] The GW#2 stores the number of smart meters accommodated in the adjacent GW provided in the entry registration response message received from the network management server 2 (Step S123). The GW#2 uses the number of smart meters accommodated in the adjacent GW noticed in the entry registration response message (the number of smart meters accommodated in the smart meters in the GW#1) . in the process at Step S115. An example in which the new smart meter 301 enters into the wireless mesh network on the GW#2 side is shown here. However, the same applies to the case where the smart meter 301 enters into the wireless mesh network on the GW#1 side. That is, the network management server 2 transmits an entry registration response message provided with the number of smart meters accommodated in the adjacent GW#2 and the information of registration being acceptable (OK) to the GW#1, and the GW#1 stores the number of smart meters accommodated in the adjacent GW (GW#2) provided in the received message.

[0031] Although not shown in the figure, the network management server 2 notifies other GWs (the GW#1 in the example shown in FIG. 3) adjacent to the GW#2 of the updated number of smart meters accommodated in the GW#2. The GW#2 itself may directly notify each adjacent GW of the updated number of accommodated smart meters. In the case where the number of smart meters accommodated in a certain GW changes, notification may be performed in any procedure as long as the latest number of accommodated smart meters after the change is noticed to all the adjacent GWs.

[0032] In the present embodiment, the case where there are two GWs has been explained. However, the same applies to a case where the number of GWs is three or more. When the number of GWs is three or more, plural pieces of information of the adjacent GWs (IDs of the GWs and the numbers of smart meters accommodated therein) are provided to the above-described various messages. [0033] As described above, in the present embodiment, the newly installed smart meter notices the ID of the gateway indicating one or more other wireless mesh networks detected by the adjacency search operation at the time of entry registration to the gateway of the wireless mesh network selected as the entry destination. Then, the gateway having received the entry registration compares the number of smart meters accommodated in the adjacent gateway noticed from the network management server with the number of accommodated smart meters managed by the own gateway, specifies a gateway having a smaller number of accommodated smart meters, and instructs the newly installed smart meter to re-enter thereinto. Then, the newly installed smart meter performs entry registration again according to the instruction. Accordingly, balancing of the number of smart meters accommodated in the gateways, that is, load distribution among the gateways can be achieved autonomously.

[0034] Second embodiment.
A second embodiment is explained next. The following description is made on an assumption that the -configuration of a communications system of the present embodiment is identical to that of the first embodiment (see FIG. 1). Similarly to the first embodiment, a case where the smart meter 301 is newly installed in a position shown in FIG. 2 is explained.

[0035] FIG. 4 is an explanatory chart of a control operation in a communications system according to the second embodiment. Specifically, FIG. 4 is a sequence diagram showing an example of an operation when a smart meter newly enters into one of the wireless mesh networks included in the communications system according to the second embodiment. In FIG. 4, as one example, there is shown a sequence when the smart meter 301 is newly installed in a position shown in FIG. 2. An operation of the present embodiment (operation when the smart meter 301 newly enters into the wireless mesh network) is explained with reference to FIGS. 2 and 4.

[0036] In the communications system according to the present embodiment, each gateway (GW#1, GW#2) activates a notification information timer, and broadcasts a notification information massage provided with the number of accommodated smart meters (the total number of smart meters accommodated therein) to the smart meters accommodated therein at regular intervals (Steps S201 to S204). Each smart meter having received the notification information massage stores the number of accommodated smart meters provided in the received message.

[0037] In such a state that the notification information message provided with the number of accommodated smart meters is broadcast on a steady basis at regular intervals, when the smart meter 301 is newly installed, the adjacency search operation (Step S205) is first performed to select an entry destination wireless mesh network. At Step S205, the smart meter 301 initially activates the search response message reception-waiting timer and broadcasts a search request message (Step S206).

[0038] The broadcast search request message reaches the i adjacent smart meters 113 and 212 present in the range of access of radio waves of the smart meter 301, and the smart meters 113 and 212 post a gateway ID (#1 or #2) indicating the entry destination wireless mesh network, the number of hops to the gateway, and the number of smart meters j accommodated in the gateway that has been acquired from the gateway by receiving the notification information message described above, in a search response message, and transmit the search response message to the smart meter 301 (Steps S207 and S208). The number of hops is as explained in the first embodiment.

[0039] Once the search response message reception-waiting timer has timed out, the smart meter 301 selects a search response message having the smallest number of accommodated smart meters, from one or more search response messages received up to that time point, and designates a smart meter that has transmitted the selected message as an access point to the wireless mesh network to enter. In the case shown in FIGS. 2 and 4, because the number of accommodated smart meters noticed from the smart meter 212 is the smallest, the smart meter 212 (the GW#2 side) is designated as the access point to the wireless mesh network to enter (Step S209) . At this time, the GW#1 is handled as an adjacent gateway.

[0040] When there are a plurality of search response messages having the smallest number of smart meters accommodated in the gateway (when M search response messages are received and among them N (M^N) search response messages have the same number of accommodated smart meters), a plurality of different selection conditions are provided including the number of hops to the gateway, the received signal strength (RSSI) at the time of receiving the message and the like, so that one of the N search response messages can be selected.

[0041] If any search response message has not been received at the time when the search response message reception-waiting timer has timed out, then the search response message reception-waiting timer is activated again, a search request message is broadcast (Step S206), and this operation is performed repeatedly until a search response message can be received.

[0042] When the adjacency search operation at Step S205 (Steps S206 to S209) is performed and selection of the entry destination is completed, the smart meter 301 activates a response waiting timer and transmits an entry registration request message to the GW#2 that manages the entry destination wireless mesh network via the adjacent smart meter 212 selected as the access point to the wireless mesh network to enter (Step S210). Although not shown in the figure, the entry registration request message includes information required for authentication processing on the gateway side (authentication information). [0043] If the entry registration response message from the GW#2 cannot be received until the response waiting timer is timed out, the smart meter 301 transmits the entry registration message again, and when the entry registration response message from the GW#2 is received before the response waiting timer is timed out, the smart meter 301 stops the response waiting timer.

[0044] The GW#2 authenticates the smart meter 301 using the authentication information included in the received entry registration request message (Step S211), updates the number of accommodated smart meters (Step S212), and transmits an entry registration response message provided with the information of registration being acceptable (OK) to the smart meter 113 (Step S213).

[0045] After having transmitted the entry registration response message, the GW#2 transmits a registration request message provided with the ID of the smart meter 301 having entered into the wireless mesh network to the network management server 2 (Step S214). Then, the network management server 2 updates the number of smart meters accommodated in the GW#2 (Step S215), and transmits an entry registration response message provided with the information of registration being acceptable (OK) to the GW#2 (Step S216).

[0046] As described above, in the present embodiment, each gateway broadcasts the notification information message provided with the number of accommodated smart meters (the total number of smart meters accommodated in the own gateway) to the smart meters accommodated therein (smart meters having entered into the wireless mesh network, to which the own gateway belongs) at regular intervals. Each smart meter adds the number of smart meters accommodated in the gateway to the response message responding to the search request message of the newly installed smart meter. The newly installed smart meter selects a response message having the smallest number of smart meters accommodated in the gateway and designates the adjacent smart meter that has returned the response message as the access point to the wireless mesh network to enter. Accordingly, balancing of the numbers of smart meters accommodated in the gateways, that is, the load distribution among the gateways can be achieved autonomously.

[0047] Third embodiment.
A third embodiment is explained next. The description herein is made on an assumption that the configuration of a communications system of the present embodiment is identical to that of the first embodiment (see FIG. 1). Similarly to the first embodiment, the description is made for a case where the smart meter 301 is newly installed in a position shown in FIG. 2 is explained.

[0048] FIG. 5 is an explanatory chart of a control operation in a communications system according to the third embodiment. Specifically, FIG. 5 is a sequence diagram showing an example of an operation when a smart meter newly enters into one of the wireless mesh networks included in the communications system according to the third embodiment. In FIG. 5, as an example, a sequence when the smart meter 301 is newly installed at a position shown in FIG. 2 is shown. An operation of the present embodiment (operation when the smart meter 301 newly enters into the wireless mesh network) is explained with reference to FIGS. 2 and 5.

[0049] In the communications system according to the present embodiment, each gateway (GW#1, GW#2) activates a regular meter-reading value collection timer in order to collect the regular meter-reading values, and transmits a meter-reading data request provided with the number of accommodated smart meters (the total number of smart meters accommodated therein) sequentially to the smart meter accommodated therein at regular intervals (Steps S301 and S303). Each smart meter having received the meter-reading data request message stores the number of smart meters accommodated in the gateway added to the meter-reading data request message, and transmits a meter-reading data response message provided with the regular meter-reading values (in electricity usage (kWh) in regular intervals or the like) to the gateway (Steps S302 and S304).

[0050] In a state where the meter-reading data request message for collecting the regular meter-reading values is transmitted to each smart meter at regular intervals and each smart meter grasps the number of smart meters accommodated in the gateway, when the smart meter 301 is newly installed, the adjacency search operation (Step S305) is performed first to select the entry destination wireless mesh network. The processes at Step S305 and subsequent steps are identical to those at Step S205 and subsequent steps explained in the second embodiment. Therefore, explanations of the processes on and after Step S305 will be omitted.

[0051] As described above, in the present embodiment, each gateway transmits the regular meter-reading data request message provided with the number of accommodated smart meters to the smart meters accommodated therein (smart meters having entered into the wireless mesh network to which the own gateway belongs) at regular intervals. Each smart meter adds the number of smart meters accommodated in the gateway to the response message responding to the search request message of the newly installed smart meter. Then, the newly installed smart meter selects a response message having the smallest number of smart meters accommodated in the gateway and designates the adjacent smart meter that has returned the response message as the access point to the wireless mesh network to enter. Accordingly, balancing of the numbers of smart meters accommodated in the gateways, that is, the load distribution among the gateways can be achieved autonomously.

[0052] Fourth embodiment.
A fourth embodiment is explained next. In the present embodiment, a modification of the communications system according to the second embodiment is explained. [0053] FIG. 6 is an explanatory chart of a control operation in the communications system according to the fourth embodiment. Specifically, FIG. 6 is a sequence diagram showing an example of an operation in which the gateway transmits the notification information message to the smart meters having entered into the wireless mesh network.

[0054] In the communications system according to the present embodiment, each gateway transmits (broadcasts) a notification information massage provided with the number of accommodated smart meters at regular intervals, similarly to the gateway explained in the second embodiment. However, each gateway does not always transmit the message with adding the number of accommodated smart meters every time. That is, in the present embodiment, at the time of transmitting the notification information message at regular intervals, each gateway determines whether or not there is increase or decrease in the number of accommodated smart meters by comparing that number with the number of accommodated smart meters at the time of transmitting the previous notification information message (Steps S401 and S404) . When there is the increase or decrease (YES at Steps S401 and YES at Step S404), each gateway adds the number of accommodated smart meters to the notification information message (Steps S402 and S405), and transmits the notification information message (Steps S403 and S406). On the other hand, when there is no increase or decrease in the number of accommodated smart meters (NO at Step S401 and NO at Step S404), each gateway transmits the notification information message without adding the number of accommodated smart meters. Only the operation of one gateway (GW#1) is shown in FIG. 6. However, other gateways perform the same operation. The operation when a smart meter is newly installed is identical to the operation in the second embodiment (the processes at Steps S205 to S216 shown in FIG. 4 are performed).

[0055] As described above, in the present embodiment, each gateway adds the number of accommodated smart meters to the notification information message broadcast to the smart meters accommodated therein at regular intervals, only when there is increase or decrease in the number of accommodated smart meters. Accordingly, effects identical to those of the second embodiment can be acquired and the amount of information of the message to be broadcast can be reduced.

[0056] Fifth embodiment.
A fifth embodiment is explained next. In the present embodiment, a modification of the communications system according to the third embodiment is explained. [0057] FIG. 7 is an explanatory chart of a control operation in the communications system according to the fifth embodiment. Specifically, FIG. 7 is a sequence diagram showing an example of an operation in which a gateway transmits a meter-reading data request message to smart meters having entered into the wireless mesh network to collect regular meter-reading values.

[0058] In the communications system according to the present embodiment, each gateway transmits a meter-reading data request massage provided with the number of accommodated smart meters at regular intervals, similarly to the gateway explained in the third embodiment. However, each gateway does not always transmit the message by adding the number of smart meters every time. That is, in the present embodiment, at the time of transmitting the meter-reading data request massage at regular intervals, each gateway determines whether there is increase or decrease in the number of accommodated smart meters as compared with the number of accommodated smart meters at the time of transmitting the previous meter-reading data request massage (Steps S501 and S505). When there is the increase or decrease (YES at Step S501 and YES at Step S505), each gateway adds the number of accommodated smart meters to the meter-reading data request massage (Steps S502 and S506), and transmits the meter-reading data request massage (Steps S503 and S507). On the other hand, when there is no increase or decrease in the number of accommodated smart meters (NO at Step S501 and No at Step S505), each gateway transmits the meter-reading data request massage without providing the number of accommodated smart meters. Only the operation of one gateway (GW#1) is shown in FIG. 7. However, other gateways perform the same operation. The operation when a smart meter is newly installed is identical to the operation in the third embodiment (the processes at Steps S305 to S316 shown in FIG. 5 are performed).

[0059] As described above, in the present embodiment, each gateway adds the number of accommodated smart meters to the meter-reading data request massage broadcast to the smart meters accommodated therein at regular intervals only when there is increase or decrease in the number of accommodated smart meters. Accordingly, effects identical to those of the third embodiment can be acquired and the amount of information of the meter-reading data request massage can be reduced.

[0060] Sixth embodiment.
A sixth embodiment is explained next. The configuration of a communications system of the present embodiment is explained on an assumption that it is identical to that of the first embodiment (see FIG. 1). [0061] FIGS. 8 and 9 are illustrations showing examples of a case where a smart meter newly enters into one of the wireless mesh networks included in the communications system having the configuration shown in FIG. 1. Specifically, FIGS. 8 and 9 depict a case where the smart meter 301 is newly installed and caused to enter into the network under the GW#1 or the network under the GW#2. FIG. 8 depicts a network configuration at the time of start of the entry operation of the smart meter 301 (before entry). FIG. 9 depicts a network configuration at the time of completion of the entry operation of the smart meter 301 (after entry). In FIGS. 8 and 9, the ranges of access of radio waves of the smart meter 301 and a smart meter 113, that becomes an access point of the smart meter 301 are indicated by one-dot chain lines. In the present embodiment, it is assumed that the smart meter 301 is installed in a position in which the smart meter 301 can communicate with only the smart meter 113 under the GW#1. The smart meter 113, which becomes the access point of the smart meter 301, has entered into the network on the GW#1 side at the time of start of the entry operation of the smart meter 301. However, it is assumed that the smart meter 113 is installed in a position in which the smart meter 113 can also communicate with the smart meter 207 having entered into the network on the GW#2 side. FIGS. 10A and 10B are explanatory charts of a control operation in the communications system according to the sixth embodiment. Specifically, FIGS. 10A and 10B are sequence diagrams of an example of an operation when the smart meter 301 is newly installed in a position shown in FIG. 8. Operations (operations when the smart meter 301 newly enters into the wireless mesh network) according to the present embodiment are explained with reference to FIGS. 8 to 10B.

[0062] When the smart meter 301 is newly installed, an adjacency search operation (Step S601) is performed to select an entry destination wireless mesh network first. At Step S601, the smart meter 301 initially activates a search response message reception-waiting timer and broadcasts a search request message (Step S602). [0063] The broadcast search request message reaches the adjacent smart meter 113 present in the range of access of radio waves of the smart meter 301, and the smart meter 113 posts a gateway ID (#1) indicating the entry destination wireless mesh network and the number of hops to the gateway (four in this example) in a search response message, and transmits the search response message to the smart meter 301 (Steps S603) . The number of hops here is as explained in the first embodiment.

[0064] Once the search response message reception-waiting timer has timed out, the smart meter 301 selects a search response message having the smallest number of hops up to the gateway, from one or more search response messages received up to that time point, and designates a smart meter that has transmitted the selected message as an access point to the wireless mesh network to enter. In FIG. 8, because only the search response message from the smart meter 113 is received, the smart meter 113 (the GW#1 side) is designated as the access point to the wireless mesh network to enter (Step S604) .

[0065] When the adjacency search operation at Step S601 (Steps S602 to S604) is performed and selection of the entry destination is completed, the smart meter 301 activates a response waiting timer and transmits an entry registration request message to the GW#1 that manages the entry destination wireless mesh network via the adjacent smart meter 113 selected as the access point to the wireless mesh network to enter (Step S605). At this time, in the previous adjacency search operation (Step S601), because there is no other wireless mesh network (no wireless mesh network managed by a GW other than the GW#1) into which the smart meter 301 can enter, "no adjacent gateway" indicating that there is no adjacent wireless mesh network into which the smart meter 301 can enter is noticed.

[0066] If the entry registration response message from the GW#1 cannot be received until the response waiting timer is timed out, the smart meter 301 transmits the entry registration message again, and when the entry registration response message from the GW#1 is received before the response waiting timer is timed out, the smart meter 301 stops the response waiting timer.

[0067] The GW#1 authenticates the smart meter 301 using the authentication information included in the received entry registration request message (Step S606), updates the number of accommodated smart meters (Step S607), and transmits the entry registration response message provided with the information of registration being acceptable (OK) to the smart meter 301 (Step S608).

[0068] After having transmitted the entry registration response message, the GW#1 transmits a registration request message provided with the ID of the smart meter 301 having entered into the wireless mesh network to the network management server 2 (Step S609). The network management server 2 updates the number of smart meters accommodated in the GW#1 (Step S610), and transmits an entry registration response message added with the information indicating registration being acceptable (OK) to the GW#1 (Step S611).

[0069] After having transmitted the entry registration response message to the GW#1, the network management server 2 determines the necessity of load adjustment between the gateways (Step S612). When having determined that the number of smart meters accommodated in the GW#1 into which the new smart meter 301 has entered is larger than the number of smart meters accommodated in the adjacent GW#2 (load adjustment is required at Step S612), the network management server 2 performs a switching operation of the entry destination wireless mesh network of the smart meter (details thereof are described later) (Step S613 in FIG. 10B). At Step S612, the network management server 2 determines that the load adjustment is required, for example, when a difference in the number of accommodated smart meters between the gateways is M or more. Alternatively, the network management server 2 may determine that the load adjustment is required when the number of smart meters accommodated in one gateway is larger than that in another gateway by N% or more. Any other methods may be used as long as the loads can be compared between the gateways. When the network management server 2 determines that the load adjustment between the gateways is not required at Step S612, the entry operation of the smart meter 301 is finished. [0070] In the switching operation of the entry destination wireless mesh network performed for Step S613 shown in FIG. 10B, the network management server 2 selects smart meters caused to re-enter into the wireless mesh network of the GW#2 on the lightly-loaded side (smart meters caused to change the entry destination) based on the difference in the number of accommodated smart meters between the gateways and the position information of each smart meter having entered into the wireless mesh network of the GW#1, and determines the re-entry order (Step S614). At this time, the number of smart meters accommodated in the GW#1 is also updated. Among the smart meters having entered into the wireless mesh network of the GW#1 (the gateway on the heavily-loaded side), as the smart meters caused to re-enter, there are selected smart meters that can also enter into another wireless mesh network (that is, that can communicate with a smart meter having entered into the other wireless mesh network), and that are as close as possible to the newly installed smart meter 301 (having a small number of hops to the smart meter 301), and smart meters positioned on a path from this smart meter to the smart meter 301. The re-entry order is such that a smart meter that can directly enter into the other wireless mesh network is the first, and a smart meter that can enter via the first smart meter is the second. The third-to-last smart meters are determined in the same manner, so that re entry of all the smart meters selected to be caused to re enter can be executed efficiently.

[0071] In the example shown in FIG. 8, since the smart meter 113 that is the access point of the smart meter 301 can also enter into the GW#2, the description is made based on an assumption that the smart meters 113 and 301 are selected, and the smart meter 301 conducts the re-entry operation first.

[0072] The network management server 2 then transmits a re-entry instruction message provided with a gateway ID (#2) of the gateway indicating the re-entry destination wireless mesh network and an entry start time (for example, after 30 seconds, immediately, or the like) to the selected smart meters 113 and 301, sequentially in the order from a smart meter having a lower entry order (later start time to re-enter) (Steps S615 and S616).

[0073] The smart meters 113 and 301 having received the re-entry instruction message respectively perform the adjacency search operations (Steps S617 and S630) in order to enter into the wireless mesh network, according to the entry start time instructed thereto.

[0074] At Step S617, the smart meter 113 instructed to start entry immediately activates a search response message reception-waiting timer, and broadcasts a search request message (Step S618) .

[0075] The broadcast search request message reaches the adjacent smart meters 109, 2 07 and 301 present in the range of access of radio waves of the smart meter 113, and the smart meters 109 and 207 post the gateway ID (#1 or #2) indicating the entry destination wireless mesh network and the number of hops to the gateway in the search response message and transmit the search response message to the smart meter 113 (Steps S620 and S619). The smart meter 301 has already activated an entry start waiting timer for waiting for the time until entry start specified in the re¬entry instruction message received at Step S615, and at this time, because the smart meter 301 is in a state before entry start, the smart meter 301 does not transmit the search response message.

[007 6] Once the search response message reception-waiting timer has timed out, the smart meter 113 selects a search response message having the smallest number of hops up to the gateway 20 (GW#2) specified in the re-entry instruction message, from one or more search response messages received up to that time point, and designates a smart meter that has transmitted the selected message as an access point to the wireless mesh network to enter. In FIG. 8, because only the smart meter 207 is connected to the GW#2, the smart meter 207 is designated as the access point to the wireless mesh network to enter (Step S621).

[0077] If any search response message has not been received when the search response message reception-waiting timer has timed out, then the smart meter 113 activates the search response message reception-waiting timer again, broadcasts a search request message (Step S618), and repeatedly performs this operation until a search response message can be received.

[0078] When the adjacency search operation at Step S617 (Steps S618 to S621) is performed and selection of the entry destination is completed, the smart meter 113 activates a response waiting timer, and transmits an entry registration request message to the GW#2 that manages the entry destination wireless mesh network via the adjacent smart meter 207 selected as the access point to the wireless mesh network to enter (Step S622). At this time, at the previous Step S617 (in the adjacency search operation), when there is another accessible wireless mesh network into which the smart meter 113 can enter (a wireless mesh network managed by a GW other than the GW#2), an ID of the GW indicating this another accessible wireless mesh network is noticed together. The ID (=#1) of the GW#1 is notice together here as an ID of the adjacent GW.

[0079] If the entry registration response message from the GW#2 cannot be received until the response waiting timer is timed out, the smart meter 113 transmits the entry registration message again, and when the entry registration response message from the GW#2 is received before the response waiting timer is timed out, the smart meter 113 stops the response waiting timer.

[0080] The GW#2 authenticates the smart meter 113 using the authentication information included in the received entry registration request message (Step S623), updates the number of accommodated smart meters (Step S624), and transmits an entry registration response message provided with information of registration being acceptable (OK) to the smart meter 113 (Step S625).

[0081] After having transmitted the entry registration response message, the GW#2 transmits a registration request message provided with the ID of the smart meter 113 having entered into the wireless mesh network to the network management server 2 (Step S626). Then, the network management server 2 updates the number of smart meters accommodated in the GW#2 (Step S627), and transmits an entry registration response message provided with the information of registration being acceptable (OK) to the GW#2 (Step S628).

[0082] After having transmitted the entry registration response message to the GW#2, the network management server 2 determines whether or not load adjustment between the gateways is required in the same manner as at Step S612 mentioned above (Step S629) . The network management server 2 determines here that load adjustment is not required (unrequired load adjustment at Step S629), and the re-entry operation (switching operation of the entry destination from the GW#1 side to the GW#2 side) of the smart meter 113 is finished.

[0083] On the other hand, the smart meter 301 having received the re-entry instruction message at Step S615 activates the entry start waiting timer for waiting for the time until entry start specified, and when the timer is timed out, performs the adjacency search operation (Step S630).

[0084] The smart meter 301 stops the operation for entering into the mesh network during the period of time from activation to time out of the entry start waiting timer. The above-mentioned re-entry operation of the smart meter 113 (Steps S617 to S629 mentioned above) is executed for a period until the entry start waiting timer is timed out. As described above, the network management server 2 determines the entry order, taking into consideration the position relation of the smart meters caused to re-enter, and instructs the entry start time to each smart meter that is to re-enter, so that the entry operation (re-entry operation) is performed in the determined order, thereby enabling to realize the re-entry operation efficiently. When the entry start time is not instructed, the entry operations may be performed adversely at the same timing by the smart meters instructed to re-enter, for example. In this case, the re-entry operation of the smart meter 301 may not be performed well until the re-entry operation of the smart meter 113 finishes, and the re-entry operation is repeated, thereby unnecessarily increasing the traffic and power consumption. The operation (transmission) of the smart meter 301 interferes with the communication of the smart meter 113, and processing delay may increase.

[0085] Steps S630 to S640 indicating the re-entry operation of the smart meter 301 are identical to the operation (Steps S602 to S611) after newly installing the smart meter, except that the entry destination wireless mesh network is different. Therefore, explanations of the re-entry operation of the smart meter 301 will be omitted.

[0086] As described above, in the present embodiment, upon reception of the entry registration request of the smart meter to be accommodated in each gateway, the network management server 2 determines the necessity of load adjustment between the gateways. When the load adjustment is required, the network management server 2 specifies a gateway having a small number of smart meters accommodated therein and instructs the smart meter selected to change the entry destination wireless network to re-enter into the specified gateway, and each smart meter instructed to reenter performs entry registration again after the specified entry start time. Accordingly, balancing of the numbers of smart meters accommodated in the respective gateways, that is, the load distribution among the gateways can be achieved autonomously.

[0087] Seventh embodiment.
A seventh embodiment is explained next. The configuration of a communications system of the present embodiment is explained on an assumption that it is identical to that of the first embodiment (see FIG. 1). In the present embodiment, similarly to the sixth embodiment, a case where the smart meter 301 is newly installed in a position shown in FIG. 8 is explained.

[0088] In the communications system according to the present embodiment, as an operation before the smart meter 301 is newly installed, each gateway (GW#1, GW#2) activate a regular meter-reading value collection timer in order to collect the regular meter-reading values, and transmits a meter-reading data request message provided with the adjacency search request to the smart meters accommodated therein at regular intervals (Step S701) . In FIG. 11, the transmission and reception operations of the meter-reading data request message and the meter-reading data response message are described while focusing on the GW#1 and the smart meter 113. However, the operation between the GW#1 and other smart meters and the operation between another gateway and the smart meter are performed in the same manner.

[0089] The smart meter 113 having received the meter-reading data request message performs the adjacency search operation (Step S702). In the adjacency search operation, the smart meter 113 activates the search response message reception-waiting timer and broadcasts a search request message (Step S703). The broadcast search request message reaches the adjacent smart meters 109 and 207 present in the range of access of radio waves of the smart meter 113, and the smart meters 109 and 207 each post the gateway ID (#1 or #2) indicating the entry destination wireless mesh network and the number of hops to the gateway in the search response message and transmit the search response message to the smart meter 113 (Steps S704 and S705).

[0090] Once the search response message reception-waiting timer' has timed out, the smart meter 113 extracts a set of the gateway ID indicating the wireless mesh network and the number of hops as a search result, based on one or more search response messages received up to that time point, and transmits a meter-reading data response message provided with the regular meter-reading values (electricity usage (kWh) in certain intervals) and the search result to the GW#1 (Step S706).

[0091] The GW#1 having received the meter-reading data response message provided with the regular meter-reading values (electricity usage (kWh) in certain intervals) and the search result transmits a search notification message provided with the search result to the network management server 2 (Step S707). Then, the network management server 2 holds the search result of the smart meter 113 (Step S708).

[0092] Because each gateway performs the operation described above (the adjacency search operation at Step S702) 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 grasp the reachability in the wireless communication between the smart meters having entered into each wireless mesh network in the communications system. That is, an adjacent smart meter that can be connected (that can perform direct wireless communication) can be grasped for each smart meter.

[0093] After having transmitted the search notification message to the network management server 2 at Step S707, the GW#1 activates the regular meter-reading collection timer, and once the timer has timed out, transmits a meter-reading data request message provided with an adjacency search request to the smart meter 113 again (Step S709). Operations thereafter (Steps S710 to S716) are identical to those explained at Steps S702 to S708, and thus explanations thereof will be omitted.

[0094] The operation after the smart meter 301 is newly installed in the communications system according to the present embodiment in which collection of the meter-reading data and the search results is performed according to the sequence shown in FIG. 11 is generally identical to that explained in the sixth embodiment. The difference between the operation of the sixth embodiment and the operation of the present embodiment is that, in the switching operation of the entry destination, the switching operation is performed, also taking into consideration the reachability in the wireless communication between the smart meters. That is, in the entry operation of a new smart meter in the present embodiment, as explained in the sixth embodiment, the smart meter 301 that desires to enter is supposed to once enter into the wireless mesh network of the GW#1 via the adjacent smart meter 113 (see Steps S601 to S611 in FIG. 10A). However, the network management server 2 determines the necessity of load adjustment between the gateways. When it is determined that the load adjustment is required and the switching operation of the entry destination wireless mesh network for the smart meter (Step S613) is to be performed, the smart meters that are caused to re-enter into the wireless mesh network of the GW#2 on the lightly-loaded side are selected based on not only the position information of the smart meters but also the reachability in the wireless communication between the smart meters covering the adjacent wireless mesh network, and the re¬entry order is determined.

[0095] Operations of causing a plurality of smart meters to re-enter into the adjacent wireless mesh network are identical to those explained in the sixth embodiment (see Steps S615 to S640 in FIG. 10B), and thus explanations thereof will be omitted.

[0096] As described above, in the present embodiment, upon reception of the meter-reading data transmission request (the meter-reading data request message) from the gateway, each smart meter performs the adjacency search, and transmits the adjacency search result to the gateway together with the meter-reading data. Then, the gateway transfers the adjacency search result received from the smart meters accommodated therein to the network management server. Then, the network management server beforehand grasps the reachability in the wireless communication between the smart meters based on the received adjacency search results, and receives the entry registration request of the smart meter. In response to this, when having determined that the load adjustment between the gateways is required, the network management server determines the smart meters that need to perform the switching operation of the entry destination, which is executed for load adjustment, taking into consideration the position information of each smart meter and the reachability in the wireless communication between the smart meters. Accordingly, balancing of the numbers of smart meters accommodated in the respective gateways, that is, the load distribution among the gateways can be achieved autonomously. Industrial Applicability

[0097] As described above, the present invention is useful as a communications system including a plurality of wireless mesh networks formed by smart meters that are nodes each having a meter reading function of electricity or the like, and is particularly suitable for a communications system that can achieve load distribution among gateways, which accommodates the wireless mesh networks.

Reference Signs List
[0098] 1 server device
2 server device (network management server)
3 wide area network 10, 20 gateway
101 to 113, 201 to 212, 301 smart meter

CLAIMS

1. A communications system comprising a plurality of wireless mesh networks each formed by a single gateway and at least one node accommodated in the gateway, which is installed in a consumer's house to measure a usage amount of at least one of electricity, gas and water, and a management server that manages the number of nodes accommodated in each of the gateways, and collects and manages measurement results obtained by the nodes, wherein when the node desires to enter into a wireless mesh network, the node notices information of all the gateways that can be connected to the node and transmits an entry request to one of the gateways that can be connected to the node directly or via another node, and

upon reception of the entry request into the own network that is a wireless mesh network managed by the own gateway, the gateway confirms the number of nodes accommodated in the own gateway and the number of nodes accommodated in another gateway that can be connected to the node having transmitted the entry request, and when there is another gateway having a smaller number of nodes accommodated therein than the number of nodes accommodated in the own gateway, the gateway instructs the node having transmitted the entry request to enter into a wireless mesh network managed by the other gateway.

2. The communications system according to claim 1, wherein when the number of nodes accommodated in each of the gateways changes, the management server notices the number of nodes after the change to each of the gateways.

3. A communications system comprising a plurality of wireless mesh networks each formed by a single gateway and at least one node accommodated in the gateway, which is installed in a consumer's house to measure a usage amount of at least one of electricity, gas and water, and a management server that manages the number of nodes accommodated in each of the gateways, and collects and manages measurement results obtained by the nodes, wherein

the gateway regularly broadcasts a notification information message in which predetermined information is stored into a wireless mesh network managed by the own gateway, and broadcasts information of the number of nodes accommodated in the own gateway using the notification information message, and

when entering into a wireless mesh network, the node selects a wireless mesh network managed by a gateway having the smallest number of nodes accommodated therein, as an entry destination.

4. The communications system according to claim 3, wherein when the number of nodes accommodated in the own gateway changes, the gateway adds the information of the number of nodes after the change to the notification information message and transmits the resultant notification information message.

5. A communications system comprising a plurality of wireless mesh networks each formed by a single gateway and at least one node accommodated in the gateway, which is installed in a consumer's house to measure a usage amount of at least one of electricity, gas and water, and a management server that manages the number of nodes accommodated in each of the gateways, and collects and manages measurement results obtained by the nodes, wherein

the gateway regularly transmits a message for requesting notification of a measurement result of the usage amount to each node accommodated in the own gateway, and notices the number of nodes accommodated in the own gateway to each node using the message, and

when entering into a wireless mesh network, the node selects a wireless mesh network managed by a gateway having the smallest number of nodes accommodated therein, as an entry destination.

6. The communications system according to claim 5, wherein when the number of nodes accommodated in the own gateway changes, the gateway adds the information of the number of nodes after the change to the message and transmits the resultant message.

7. A communications system comprising a plurality of wireless mesh networks each formed by a single gateway and at least one node accommodated in the gateway, which is installed in a consumer's house to measure a usage amount of at least one of electricity, gas and water, and a management server that manages the number of nodes accommodated in each of the gateways and position information of each node, and collects and manages measurement results obtained by the nodes, wherein

when a new node enters into a wireless mesh network managed by the own gateway, the gateway updates information of the number of nodes accommodated in the own gateway, and notices the updated number of nodes to the management server, and

when notification of the updated number of nodes is made, the management server determines the necessity of load adjustment among the gateways based on the number of nodes accommodated in each gateway, and when the load adjustment is required, the management server selects a part of the nodes accommodated in a gateway that is in an overload condition based on the position information, and instructs the selected node to change an entry destination to a wireless mesh network managed by a gateway that is not in an overload condition.

8. The communications system according to claim 7, wherein when instructing the selected nodes to change the entry destination, the management server instructs each node to have a different operation start timing as a timing to perform the entry destination change operation, so that the entry destination change operations of the nodes are caused to be performed in a desired order.

9. The communications system according to claim 7 or 8, wherein the gateway regularly instructs each node accommodated therein to search an adjacent node to acquire a search result from each node, and notices the search results to the management server, and

when having determined that the load adjustment is required, the management server selects a part of nodes accommodated in a gateway that is in an overload condition, based on the position information and the search results.