WO2015198403A1 - Communication device, smart meter, and wireless mesh network - Google Patents

Abstract

This communication device is a host device (1) that forms a wireless mesh network together with smart meters each including a power supply synchronization-type clock, the communication device comprising: a synchronization partner determination unit (13) that selects a candidate for synchronizing the local time of the present communication device on the basis of the hop count to each smart meter forming the wireless mesh network and/or the wireless communication quality between the communication device and each smart meter, and that determines a reference smart meter on the basis of the local time of the reference candidate smart meter and the local time of each smart meter with which the reference candidate smart meter can directly communicate; and a time synchronization control unit (12) that adjusts the local time of the present communication device and synchronizes the local time with the local time of the reference smart meter, and also distributes information on the local time of the present communication device to at least the smart meters other than the reference smart meter within the wireless mesh network.

Description

Communication device, smart meter and wireless mesh network

The present invention relates to a communication device, a smart meter, and a wireless mesh network that transmit / receive a meter reading value of power used by multi-hop communication.

In recent years, a system has been studied in which a measuring instrument (meter) equipped with a wireless communication unit is installed in each consumer and the usage amount of electricity, gas, water, etc. is automatically collected. This system is called an automatic meter reading system. Each measuring instrument forms a wireless mesh network, and transmits a meter reading value as a measurement result to a device that collects the meter reading value by multi-hop communication.

For example, in an automatic meter reading system that automatically collects electricity usage at consumers, schedule management of the time to collect meter readings is performed, and the meter reading value from the meter to the central data collecting device at a certain time Sending data such as. Therefore, in the automatic meter reading system, it is necessary to synchronize the time managed individually by the data collection device and each measuring instrument.

As a technique for realizing time synchronization between devices forming a communication network, for example, there are inventions described in Patent Documents 1 and 2.

In the wireless communication system described in Patent Document 1, a device that manages a reference time distributes information on a reference time, and surrounding devices that receive the information on the reference time adjust their own time (local time). To match the reference time and distribute time information. Hereinafter, similarly, each device that receives the time information adjusts the local time and distributes the time information to realize time synchronization.

The data collection system described in Patent Document 2 realizes time synchronization using an NTP (Network Time Protocol) server. In this data collection system, a gateway of a multi-hop wireless communication network formed by a measuring instrument terminal installed at a consumer periodically acquires information on a reference time from an NTP server, corrects an internal clock, Send time information into the network. The scale terminal corrects the internal clock when receiving the time information.

JP 2013-153400 A JP 2011-35699 A

In the conventional system as described above, the reference time information is acquired using an NTP server. However, when the NTP server cannot be used, such as when a device that manages the reference time must be installed in a location where access to the NTP server is not possible, the time of each device in the system can be adjusted to the correct time. There was a problem that it was not possible. In an automatic meter reading system, a host device that collects meter reading values often uses a clock with a crystal that is not highly accurate, so if the time managed by the host device is a reference time, the number of devices per day Deviations from 10 seconds to several minutes occur. In the automatic meter reading system, for example, when real-time meter reading in units of 30 minutes is required, it becomes a problem.

The present invention has been made in view of the above, and an object thereof is to obtain a communication device, a smart meter, and a wireless mesh network that realize time synchronization between devices in a wireless mesh network.

In order to solve the above-described problems and achieve the object, the present invention is a communication device that forms a wireless mesh network together with each smart meter, the number of hops to each smart meter and the wireless between each smart meter. Based on at least one of the communication qualities, a reference candidate smart meter that is a candidate for a reference smart meter that synchronizes the local time of its own device is selected from each smart meter, and the local time and reference of the reference candidate smart meter are selected. Based on the local time of each smart meter with which the candidate smart meter can communicate directly, the synchronization partner determination unit that determines the reference smart meter, and adjusts the local time of its own device to synchronize with the local time of the reference smart meter, and , Information on the local time of its own device in the wireless mesh network, Characterized by comprising a time synchronization controller to be distributed to each smart meter other than the reference smart meter, the even without.

According to the communication device of the present invention, the time of each smart meter in the wireless mesh network is synchronized with the correct time even when installed in a place where it is difficult to acquire the correct time information from an external NTP server or the like. There is an effect that can be.

FIG. 1 is a diagram illustrating an example of an automatic meter reading system using a wireless mesh network. FIG. 2 is a diagram illustrating a configuration example of the host device. FIG. 3 is a diagram illustrating a configuration example of the smart meter. FIG. 4 is a flowchart illustrating an example of an operation in which the host device adjusts the time. FIG. 5 is a flowchart illustrating an example of an operation in which the smart meter adjusts the time. FIG. 6 is a sequence diagram showing an example of a control procedure for realizing initial time synchronization in the wireless mesh network having the configuration shown in FIG. FIG. 7 is a sequence diagram illustrating an example of a meter reading transmission operation in a wireless mesh network. FIG. 8 is a diagram illustrating an example of the network status table. FIG. 9 is a sequence diagram illustrating an example of a time synchronization control procedure. FIG. 10 is a sequence diagram illustrating an example of a time synchronization control procedure. FIG. 11 is a diagram illustrating an example of a time quality evaluation value calculation operation. FIG. 12 is a diagram for explaining the time quality evaluation value.

Hereinafter, embodiments of a communication device, a smart meter, and a wireless mesh network according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an example of an automatic meter reading system using a wireless mesh network formed by a communication device according to the present invention.

As shown in FIG. 1, the automatic meter reading system of the present embodiment is a communication device according to the present invention, and a smart meter that is a watt hour meter including a host device 1 that collects meter reading values and a wireless communication unit. 2 ₁ to 2 ₁₂ . The host device 1 and the smart meters 2 ₁ to 2 ₁₂ form a wireless mesh network.

The host device 1 manages a local time that is a reference in the wireless mesh network (hereinafter also referred to as a reference time), and appropriately distributes information on the reference time into the wireless mesh network. It is assumed that the host device 1 manages the reference time with a clock using a crystal resonator.

The smart meters 2 ₁ to 2 ₁₂ manage the local time using a power synchronous clock, and when receiving information on the reference time managed by the host device 1, adjust the local time to adjust the reference time. Synchronize with. Further, the smart meters 2 ₁ to 2 ₁₂ measure the power consumption in the customer in which they are installed, and transmit the meter reading value indicating the measurement result to the host device 1 at a predetermined timing. Further, when the smart meters 2 ₁ to 2 ₁₂ receive data that is not addressed to themselves, the smart meters 2 ₁ to 2 ₁₂ transfer the data to the destination. For example, when a meter reading value transmitted to the host device 1 is received, the meter reading value is transferred to the host device 1.

The configuration of the wireless mesh network shown in FIG. 1 will be described.

The smart meters 2 ₁ , 2 ₂ , 2 ₃ and 2 ₄ are set to communicate with the host device 1. That is, the smart meters 2 ₁ , 2 ₂ , 2 ₃ and 2 ₄ are located at the first hop from the host device 1 and directly transmit the meter reading value to the host device 1.

Smart meter 2 ₅ is set to communicate with the smart meters 2 ₁ is a device from the host device 1 first hop. That is, the smart meter 2 ₅ is located from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₁ of 1 hop higher.

The smart meter 2 ₆ is set to communicate with the smart meter 2 ₂ which is a first hop device from the host device 1. That is, the smart meter 2 ₆ are located from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₂ 1 hop higher.

The smart meter 2 ₇ is set to communicate with the smart meter 2 ₂ , which is a first hop device from the host device 1. That is, the smart meter 2 ₇ is located at the second hop from the host device 1 and transmits the meter reading value to the host device 1 via the smart meter 2 ₂ that is one hop higher.

Smart meter 2 ₈ is set to communicate with a smart meter 2 ₂ is a device from the host device 1 first hop. That is, the smart meter 2 ₈ is located from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₂ 1 hop higher.

Smart meter 2 ₉ is configured to communicate with a smart meter 2 ₃ is a device from the host device 1 first hop. That is, the smart meter 2 ₉ is positioned from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₃ one hop higher.

Smart meter 2 ₁₀ is configured to communicate with a smart meter 2 ₄ is a device from the host device 1 first hop. That is, the smart meter 2 ₁₀ is located from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₄ 1 hop higher.

Smart meter ₂₁₁ is configured to communicate with a smart meter 2 ₄ is a device from the host device 1 first hop. That is, the smart meter ₂₁₁ is positioned from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₄ 1 hop higher.

Smart meter 2 ₁₂ is configured to communicate with the smart meters 2 ₁ is a device from the host device 1 first hop. That is, the smart meter 2 ₁₂ is located from the host device 1 to 2 th hop, and transmits to the host device 1 the meter reading value via the smart meters 2 ₁ of 1 hop higher.

In FIG. 1, the maximum number of hops from the host device 1 to the smart meter is 2, but a smart meter having three or more hops from the host device 1 may be included. It is assumed that the host device 1 holds identification information of each smart meter forming the wireless mesh network and information regarding the configuration of the wireless mesh network (connection relationship of each smart meter). That is, the host device 1 grasps each smart meter of 1 hop from itself, each smart meter of 2 hops or more, and grasps a route (communication route) through which the meter reading value is transmitted from each smart meter. It shall be. The identification information of each smart meter and the information related to the connection relationship of each smart meter can be acquired, for example, when the smart meter enters the wireless mesh network. The operation of the smart meter entering the wireless mesh network will be briefly described. For example, the smart meter searches for a communicable device (another smart meter or host device 1 that has already entered the wireless mesh network) at the time of startup. When a communicable device is found, a network entry request is transmitted to the device. There may be a plurality of communicable devices. In that case, one device is selected in consideration of the number of hops to the higher-level device 1 and the wireless communication quality. The selected device becomes the transmission destination of the meter reading value after the entry into the wireless mesh network is completed. The entry request is transferred as necessary, and finally reaches the host device 1. When the host device 1 recognizes the entry of the smart meter requesting entry, the host device 1 returns a response indicating that. At this time, for example, when the device that transmits the entry request (the smart meter that has already entered the wireless mesh network) adds its identification information to the entry request and transfers it, the host device 1 can newly enter the smart It is possible to grasp the connection relationship between a meter and a smart meter that has already entered the market. If the connection relationship is known, the number of hops to the smart meter can be found. The host device 1 can know the connection relationship of each smart meter other than when receiving the entry request. For example, when the meter reading value is received from each smart meter, the connection relationship can be known by the same method.

When each smart meter of the wireless mesh network becomes unable to communicate with the transmission destination of the meter reading value which is the device (other smart meter or host device 1) selected when entering the wireless mesh network, the wireless mesh network Entry operation is again executed, and a new connection destination device (the transmission destination of the meter reading value) is selected. Also, the wireless communication quality is unstable and the optimal connection destination may change, and the optimal communication path to the host device 1 may change when a new smart meter enters the wireless mesh network. Each smart meter may reset the connection destination device at a predetermined timing.

In the following description, it is not necessary to distinguish between the two ₁₂ from the smart meter 2 _1, when describing common matters (configuration and operation) from the smart meter 2 ₁ to 2 _12, 2 ₁₂ from the smart meter 2 ₁ Are collectively referred to as a smart meter 2.

As described above, since the host device 1 manages the local time using a clock that uses a crystal resonator, the local time starts from the correct time as time elapses due to variations in the specifications and performance of the crystal resonator used. There is a possibility of shifting. For example, in the case of using a crystal resonator with high accuracy, there is a possibility that a deviation of several tens of seconds or more per day may occur. As a countermeasure to this problem, when the host device 1 can access an external NTP server or the like that manages the correct time, it acquires the correct time information from the outside and adjusts the local time to indicate the correct time. To do. However, when the host device 1 is installed in a place where it cannot access an external NTP server or the like, the local time cannot be adjusted.

On the other hand, since each smart meter 2 uses a highly accurate power synchronous clock, basically, if the local time of the smart meter 2 is adjusted to indicate the correct time, the local time will be indicated thereafter. Will not deviate from the correct time. However, when the smart meter 2 is installed at a position close to a power source such as an elevator, the local time may not show the correct time due to the influence of noise generated from the inverter.

Therefore, in the wireless mesh network according to the present embodiment, when the host device 1 cannot acquire the correct time information from the NTP server or the like, the host device 1 uses the correct time among the local times managed by each smart meter 2. Is adjusted so that the reference time indicates the correct time. Further, control is performed so that the local time of all smart meters is synchronized with the reference time. Specifically, first, the host device 1 identifies a smart meter whose local time is correct, and uses its time information acquired from this smart meter to adjust its own time (reference time) to the correct time. At the same time, the reference time information is broadcast into the wireless mesh network. Next, each smart meter adjusts its own time based on the reference time information transmitted from the host device 1 and synchronizes with the reference time.

Hereinafter, the wireless mesh network according to the present embodiment will be described in detail.

FIG. 2 is a diagram illustrating a configuration example of the host device 1. The host device 1 includes a timer unit 11, a time synchronization control unit 12, a synchronization partner determination unit 13, a data collection unit 14, a network management unit 15, and a wireless communication unit 16.

The timer unit 11 is constituted by a clock using a crystal resonator and manages the local time of the host device 1. The time managed by the time measuring unit 11 is the reference time of the wireless mesh network.

The time synchronization control unit 12 adjusts the time managed by the time measuring unit 11 to the correct time. For example, when it is possible to access an external NTP server that manages the correct time, information on the correct time is periodically acquired from the outside, and the time managed by the time measuring unit 11 is adjusted. When it is impossible to acquire the correct time information from the outside, the time managed by the time measuring unit 11 is adjusted so that the time is synchronized with the smart meter 2 of the local time indicating the correct time. . Further, the adjusted time information is distributed as reference time information in the wireless mesh network, and an instruction is given to synchronize the local time of each smart meter 2 with the reference time.

The synchronization partner determination unit 13 adjusts and synchronizes the time managed by the time measurement unit 12 with the time synchronization control unit 12 when it is impossible to obtain correct time information from the outside. And time information (information of the correct time) is acquired from the selected smart meter 2.

The data collection unit 14 collects meter reading values from each of the smart meters 2 forming the wireless mesh network.

The network management unit 15 manages the wireless mesh network and manages the identification information of each smart meter 2 forming the wireless mesh network, the communication path to each smart meter 2, and the like. Moreover, when the entry request to a wireless mesh network is received from the smart meter 2, it is determined whether entry is permitted.

The wireless communication unit 16 transmits and receives wireless signals to and from the smart meter 2 via an antenna (not shown). Further, the wireless communication unit 16 measures the quality of wireless communication with each smart meter 2 capable of direct communication.

FIG. 3 is a diagram illustrating a configuration example of the smart meter 2. The smart meter 2 includes a timer unit 21, a time synchronization control unit 22, a time evaluation unit 23, a weighing unit 24, a route management unit 25, and a wireless communication unit 26.

The timer unit 21 is composed of a power synchronous clock and manages the local time of the smart meter 2.

When the time synchronization control unit 22 receives the reference time information (hereinafter referred to as reference time information) transmitted from the host device 1, the time synchronization control unit 22 determines the time managed by the time measuring unit 21 based on the received reference time information. adjust. Also, the received reference time information is transferred. Further, when a time inquiry is received from the host device 1, the time managed by the timer unit 21 is notified to the host device 1.

The time evaluation unit 23 collects time information from other smart meters 2 capable of direct communication, and whether the time managed by the time measuring unit 21 is synchronized with the time managed by the other smart meter. Is determined.

The measuring unit 24 performs meter reading at a predetermined timing, and transmits the obtained meter reading value to the host device 1.

The route management unit 25 manages a communication route with the host device 1. In addition, a request to participate in the wireless mesh network is transmitted to the host device 1.

The wireless communication unit 26 transmits and receives wireless signals to and from the host device 1 or another smart meter 2 via an antenna (not shown). Further, the wireless communication unit 26 measures the wireless communication quality between the host device 1 and each smart meter 2 that can perform direct communication.

FIG. 3 shows a configuration example in which the components of the smart meter 2 are housed in the same housing, but some components may be configured separately. For example, the route management unit 25 and the wireless communication unit 26 and other components are configured separately, and a measuring device having a meter reading function (a device provided with a time measuring unit 21, a time synchronization control unit 22, a time evaluation unit 23, and a measuring unit 24) ) May be connected to a wireless communication unit (a device including the path management unit 25 and the wireless communication unit 26).

FIG. 4 is a flowchart showing an example of the operation of the host device 1 adjusting the time. FIG. 5 is a flowchart illustrating an example of an operation in which the smart meter 2 adjusts the time. In the wireless mesh network of the present embodiment, when an external NTP server or the like that manages correct time information cannot be used, the host device 1 operates according to FIG. 4 and each smart meter 2 operates according to FIG. Thus, time synchronization is realized.

As shown in FIG. 4, the host device 1 monitors whether or not it is time synchronization execution time and whether or not data is received (steps S11 and S17). (Step S11: Yes), a smart meter candidate (time information acquisition source meter candidate) that is an acquisition source of information indicating the correct time is selected (step S12). In this step S12, the synchronization partner determining unit 13 determines the time information acquisition source smart meter candidates based on the number of hops from itself (the host device 1), wireless communication quality (for example, electric field strength), that is, Select a reference candidate smart meter. For example, when selecting based on the number of hops, a certain number of smart meters 2 are selected as candidates in order from the smallest number of hops. When selecting based on wireless communication quality, a certain number of smart meters 2 are selected as candidates in order from the best wireless communication quality. Candidates may be selected based on both the number of hops and the wireless communication quality. The time synchronization is performed at a frequency of once / day, for example.

When the synchronization partner determination unit 13 of the higher-level device 1 selects a candidate for a time information acquisition source meter, it instructs each smart meter 2 selected as a candidate to perform a peripheral search (step S13). Specifically, another smart meter in the vicinity is searched, and an instruction is given to collect time information from the discovered smart meter. Next, the synchronization partner determination unit 13 selects a smart meter as a time information acquisition source, that is, a reference smart meter, based on the peripheral search results (collected time information) performed by each of the time information acquisition source meter candidates. Further, time information (information on the local time of the smart meter 2 as a time information acquisition source) is acquired from the determined reference smart meter (step S14).

Next, the time synchronization control unit 12 adjusts the time managed by the time measuring unit 11 in accordance with the time information acquired in step S14 (step S15). When the time adjustment is completed, the time synchronization control unit 12 distributes the adjusted time information to each smart meter 2 in the wireless mesh network (step S16). When the smart meter 2 receives the time information distributed in step S16, the smart meter 2 adjusts the local time according to the received time information. In addition, since the time information distributed in step S16 is the local time of the reference smart meter itself, it is not necessary to distribute it to the reference smart meter. Of course, in each smart meter 2 other than the host device 1 and the reference smart meter, the time information is sent to the reference smart meter for the purpose of notifying that the synchronization with the reference time is completed or notifying that it is the reference smart meter. You may distribute. Further, the time information may be distributed to the reference smart meter in order to distribute the time information via the reference smart meter to the smart meter 2 in a position where the host device 1 cannot communicate directly. Furthermore, in order to simplify the configurations of the host device 1, the smart meter 2, and the wireless mesh network, the time information is distributed to the reference smart meter without being distinguished from other smart meters 2, and the same time information as the local time is obtained. However, the reference smart meter may adjust the local time. For these reasons, it can be said that the time synchronization control unit 12 distributes time information to each smart meter 2 other than at least the reference smart meter in the wireless mesh network.

Further, when the data collection unit 14 of the host device 1 receives data from the smart meter 2 (step S11: No, step S17: Yes), the network status table (hereinafter referred to as a network status table) is updated ( Step S18). The received data is, for example, meter reading values and wireless communication quality data. The network status table is a table in which the number of hops to each smart meter 2 forming the wireless mesh network, the quality of wireless communication with each smart meter 2, and the like are registered. Used when selecting acquisition source meter candidates. Details of the network status table will be described later. The network status table may be held by the data collection unit 14 or may be held by a storage unit (not shown). The time synchronization control unit 12 or the synchronization partner determination unit 13 may hold it.

As shown in FIG. 5, the smart meter 2 monitors whether it is a data transmission time, whether it has received time information, whether it has received a time inquiry, and whether it has received a peripheral search instruction. (Steps S21 to S24). In the case of the data transmission time (step S21: Yes), the measuring unit 24 transmits the meter reading value and the wireless communication quality data to the host device 1 (step S27). The wireless communication quality data is, for example, data of wireless communication quality with a device (host device 1 or smart meter 2) one hop higher, for example, information indicating the electric field strength. The wireless communication quality data is managed by the wireless communication unit 26, and the measuring unit 24 acquires the wireless communication quality data from the wireless communication unit 26 and transmits it together with the meter reading value. The timing at which the meter reading value and the wireless communication quality data are transmitted by executing step S27 is determined in advance, and the measuring unit 24 transmits the meter reading value and the wireless communication quality data, for example, every 30 minutes.

When the time synchronization control unit 22 of the smart meter 2 receives the time information (step S22: Yes), the time synchronization control unit 22 adjusts its own time (the time managed by the time measuring unit 21) according to the received time information, The time of the transmission source device is synchronized with the own time (step S28). Further, when a time inquiry is received (step S23: Yes), time information indicating its own time is transmitted to the host device 1 (step S29). In addition, when the time evaluation unit 23 of the smart meter 2 receives a surrounding search instruction (step S24: Yes), the smart meter 2 searches for the surrounding smart meter 2 (step S25). Specifically, the management time (local time) is inquired to surrounding smart meters 2, and information on the local time of each smart meter 2 in the cycle is collected. When the peripheral search is completed, a time quality evaluation value is calculated based on the collected local time information and transmitted to the host device 1 (step S26). Although details of the time quality evaluation value will be described later, the time quality evaluation value is information indicating the reliability of its own time. In the present embodiment, a case where the time quality evaluation value is large and the possibility that the own time is likely to be correct is high will be described as an example. The time evaluation unit 23 may transmit the collected local time information as it is to the higher-level device 1 and calculate a time quality evaluation value on the higher-level device 1 side.

That is, in either case where the host device 1 calculates the time quality evaluation value or the smart meter 2 calculates the time quality evaluation value, the synchronization partner determination unit 13 determines the local time and the reference of the reference candidate smart meter. It can be said that the reference smart meter is determined based on the local time of the smart meter 2 around the candidate smart meter (the smart meter 2 to which the reference candidate smart meter 2 can directly communicate). Therefore, it can be said that the host device 1 acquires the time quality evaluation value includes the case where the host device 1 itself calculates the time quality evaluation value.

Further, when the host device 1 calculates the time quality evaluation value, the local time of the smart meter 2 around the reference candidate smart meter (the smart meter 2 to which the reference candidate smart meter 2 can directly communicate) is determined from the reference candidate smart meter. Is acquired through the reference candidate smart meter, and only the local time of the reference candidate smart meter is acquired. Next, the local time of the acquired reference candidate smart meter may be compared to determine the reference candidate smart meter having the local time with the highest time reliability as the reference smart meter. That is, the local time of the reference candidate smart meter is compared, and the time quality evaluation value for each local time of the reference candidate smart meter is calculated, and the local time with the highest time reliability is obtained from the time quality evaluation value. The reference candidate smart meter is determined as the reference smart meter. The time quality evaluation value calculation method here is also calculated from the local time of the reference candidate smart meter and the local time of the smart meter 2 around the reference candidate smart meter (the smart meter 2 to which the reference candidate smart meter 2 can directly communicate). Since it is the same as that to do, description is abbreviate | omitted.

Next, the overall operation in the wireless mesh network of this embodiment, specifically, the time synchronization control operation when an external NTP server that manages the correct time information cannot be used will be described. FIG. 6 is a sequence diagram showing an example of a control procedure for realizing initial time synchronization in the wireless mesh network having the configuration shown in FIG. As shown in FIG. 6, information on the correct time is input to the host device 1 from the outside (operator) at the timing of startup, for example. In the host device 1 to which the correct time information is input, the time synchronization control unit 12 sets the time managed by the time measuring unit 11 to the correct time in accordance with the input information (correct time information) (step) S31).

When the host device 1 sets its own time to the correct time, the host device 1 broadcasts information on its own time (a reference time that is a time managed by the timer unit 11) into the wireless mesh network (step S32). The broadcast time information reaches the smart meters 2 ₁ to 2 ₄ that can directly communicate with the host device 1.

Smart meter 2 ₁ to 2 ₄ receives the time information from the host device 1, and adjusts its own time synchronize to the time of the host apparatus 1 (reference time) (step S33). That is, in the smart meter 2 ₁ to 2 _4, the time synchronization control unit 22 in accordance with time information received from the host device 1, set the time managed by the time measuring section 21 to the correct time (time of the host device 1).

Smart meter 2 ₁ to 2 _4, setting its own time to the correct time, broadcasts the information of the time to the wireless mesh network (step S34). The broadcast time information reaches the smart meters 2 ₅ to 2 ₁₂ that can directly communicate with the smart meters 2 ₁ to 2 ₄ . Specifically, the time information transmitted by the smart meter 2 ₁ reaches the smart meters 2 ₅ and 2 ₁₂ , and the time information transmitted by the smart meter 2 ₂ reaches the smart meters 2 ₆ , 2 ₇ and 2 ₈ , time information smart meter 2 ₃ sends reaches the smart meter 2 _9, time information smart meter 2 ₄ transmits arrives at the smart meter 2 ₁₀ and 2 _11. The smart meters 2 ₁ to 2 ₄ may transmit their own time information in the broadcast of time information, or may transmit (transfer) the time information received from the host device 1 as it is. In the former case, the time information transmitted indicates the time at which the smart meters 2 ₁ to 2 ₄ executes the transmission process, in the latter case, the time information transmitted, the upper device 1 executes the transmission process Indicates the current time.

2 ₁₂ from the smart meter 2 ₅ receives the time information, and adjusts its own time synchronize to the time of the host apparatus 1 (reference time) (step S35). The operations of the smart meters 2 ₅ to 2 ₁₂ in step S35 are the same as when the smart meters 2 ₁ to 2 ₄ receive time information from the host device 1. However, when the received time information indicates the time at which the host apparatus 1 executes the transmission process, the smart meters 2 ₅ to 2 ₁₂ are configured to execute the transfer process by the smart meters 2 ₁ to 2 _4. The time is adjusted in consideration of the accompanying delay time. The delay time generated by the transfer process can be grasped in advance by performing a simulation or the like. Each smart meter 2 is assumed to know in advance the delay time that occurs in association with the transfer process.

The time synchronization is established in the wireless mesh network by the host device 1 and each smart meter 2 executing the processes in steps S31 to S35 according to the sequence shown in FIG.

In a state in which time synchronization is established in the wireless mesh network, as shown in FIG. 7, each smart meter 2 periodically (for example, every 30 minutes) displays the wireless communication quality information together with the meter reading value as the host device 1. (Steps S41A to S52A). The wireless communication quality is, for example, at least a reception level (also referred to as electric field strength) of a signal received from a higher-level device (high-level device 1 or smart meter 2) and a reception level of a signal received from a lower-level device (smart meter 2). One or both.

The host device 1 updates the wireless network status every time it receives wireless communication quality information from the smart meter 2 (steps S41B to S52B). The wireless network status updated in steps S41B to S52B is, for example, the information table having the configuration shown in FIG. 8, and this information table corresponds to the “network status table” described above. The host device 1 holds the network status table shown in FIG. 8, and grasps the number of hops to each smart meter 2 forming the wireless mesh network and the quality of wireless communication with each smart meter 2. ing.

As shown in FIG. 8, the network status table includes “smart meter ID”, “information acquisition date / time”, “hop count”, “first hop smart meter”, “radio quality up to one hop”, “ The “second hop smart meter” and “wireless quality up to two hops” are registered. In addition, when the smart meter 2 of the 3rd hop or more exists from the high-order apparatus 1, the information regarding the smart meter of the 3rd hop or more is also registered into a network status table.

“Smart meter ID” is identification information of each smart meter that has already entered the wireless mesh network. “Information acquisition date and time” indicates the date and time when wireless communication quality information is acquired from the corresponding smart meter 2. “Number of hops” indicates the number of hops to the corresponding smart meter 2. The “first hop smart meter” is identification information of the first hop smart meter 2 in the communication path to the corresponding smart meter 2. “Radio quality up to one hop” indicates the radio communication quality with the smart meter 2 at the first hop. The “second hop smart meter” is identification information of the second hop smart meter 2 in the communication path to the corresponding smart meter 2. “Radio quality up to two hops” indicates the radio communication quality with the smart meter 2 of the second hop. The wireless quality registered in the “wireless quality up to 2 hops” is the wireless quality between the host device 1 and the first hop smart meter 2 and the first hop smart meter 2 and the second hop smart meter. 2 based on the wireless quality between the two. For example, the average value of the former (the radio quality between the host device 1 and the first hop smart meter 2) and the latter (the radio quality between the first hop smart meter 2 and the second hop smart meter 2) Register for. Of the previous night and the latter, the one with the lower quality may be selected and registered.

Further, in order to maintain the state in which time synchronization is established in the wireless mesh network, the host device 1 and each smart meter 2 periodically execute the operations shown in FIG. 9 and FIG. Correct the time. Further, information on the reference time is notified to each smart meter 2, and an instruction is given to synchronize the local time with the reference time. The period for executing the operation (time synchronization control) shown in FIG. 9 and FIG. 10 depends on the performance of the crystal unit used by the host device 1 and the required specifications of the automatic meter reading system to which the wireless mesh network is applied. Decide in consideration. For example, the cycle is one day (24 hours).

That is, the host device 1 selects a candidate for obtaining time information from the smart meters 2 ₁ to 2 ₁₂ forming the wireless mesh network at a predetermined timing (FIG. 9, step S61). ). Specifically, a certain number of smart meters 2 are selected as candidates based on at least one of the number of hops to each smart meter 2 and the wireless communication quality. When the wireless communication quality is poor, the transmission delay increases due to the occurrence of retransmission, and the error included in the acquired time information increases. The error included in the time information acquired from the smart meter 2 having a large number of hops tends to be larger than the error included in the time information acquired from the smart meter 2 having a small number of hops. Therefore, the host device 1 selects the smart meter 2 having a small number of hops and good wireless communication quality. For example, 1-hop wireless communication quality (field strength) from the top to the Nth is selected as a candidate. When the number of 1-hop smart meters 2 is less than N, one having a higher wireless communication quality is further selected from the 2-hop smart meters 2. Instead of setting the number of candidates to be selected as a fixed value, a condition may be set for each of the number of hops and wireless communication quality, and the smart meter 2 that satisfies the condition may be selected as a candidate. Here, the description will be continued assuming that the smart meters 2 ₁ , 2 ₂ , 2 ₃ and 2 ₄ are selected.

When the host apparatus 1 executes step S61 and selects a candidate, next, it instructs the selected smart meters 2 ₁ , 2 ₂ , 2 ₃ and 2 ₄ to sequentially search for surroundings (steps S62, S67, S71, S75).

Smart meter 2 ₁ receives the peripheral search instruction broadcasts a message inquiring the time to a smart meter 2 near that enables direct communication (step S63). This message reaches the smart meters 2 ₂ , 2 ₄ , 2 ₅ , 2 ₆ and 2 ₁₂ and is received. The smart meters 2 ₂ , 2 ₄ , 2 ₅ , 2 ₆ and 2 _{12 which} have received the time inquiry return the local time information (step S 64).

Smart meter 2 ₁ receives the time information transmitted in step S64, to calculate the time quality evaluation value indicating the reliability of the local time of the own (Step S66). For example, as shown in FIG. 11, each local Tn (n = ₂ , ₄ , ₅ , _{6, 12} ) and its own local time in the surrounding smart meters 2 ₂ , 2 ₄ , 2 ₅ , 2 ₆ and 2 ₁₂ The difference of T1 is calculated, respectively, the number of smart meters 2 where the difference T1-Tn is less than the specified value (Ts) (referred to as the number of time synchronization devices Ns), and the number of smart meters 2 detected by the peripheral search (the number of detections) N), a time quality evaluation value is calculated. Here, (time quality evaluation value) = Ns / N.

Smart meter 2 _1, the calculation time quality evaluation value is completed, the evaluation results as to transmit to the host device 1 (step S66).

When the smart meters 2 ₂ , 2 _3, and 2 ₄ receive the surrounding search instruction, the smart meters 2 ₂ , 2 _3, and 2 ₄ calculate a time quality evaluation value in the same procedure as the smart meter 2 ₁ and transmit it to the host device 1 (steps S 67 to S 78).

Upon receiving the time quality evaluation values from all candidates selected in step S61, the host device 1 compares the received time quality evaluation values, and the time quality evaluation value having the maximum value, that is, the time quality evaluation value is the highest. The smart meter 2 that has transmitted the reliability value is determined as a reference smart meter from which time information is acquired (step S79 in FIG. 10). If all the received time quality evaluation values are equal to or smaller than a certain value (threshold value), step S61 is executed again to select a candidate, and the same processes as in steps S62 to S78 are executed. The time quality evaluation value may be reacquired. Here, the description will be continued assuming that determine the smart meter 2 ₂ to retrieve.

Host device 1 may then request time information to the smart meter 2 ₂ determined in step S79 (step S80), smart meter 2 which has received the request ₂ to the host device 1 the time information indicating the local time Transmit (step S81).

Host device 1 receives the time information from the smart meter 2 _2, synchronize its time to the local time of the smart meter 2 ₂ (step S82). That is, by adjusting its time, adjusted to the time at which the received time information indicates (local time of the smart meter 2 _2). Next, the host device 1 broadcasts its own time (reference time) information into the wireless mesh network (step S83). When each smart meter 2 receives the reference time information, it adjusts the local time to the reference time (steps S84 to S86). Note that the processing of steps S83 to S86 is the same as the processing of steps S32 to S35 shown in FIG.

In step S61 described above, by selecting the first hop smart meter 2 as a candidate, the transmission delay associated with the transfer process can be minimized. In addition, by selecting a field whose electric field strength is greater than a specified value, it is less susceptible to the dynamic switching of the route, which is a feature of a wireless mesh network using multi-hops. I try to be a hop.

In step S79, the smart meter 2 having the largest time quality evaluation value, that is, the smart meter 2 having the smallest time difference from the surroundings is determined as the time information acquisition source, which affects the power supply quality. When there is a smart meter 2 in which noise occurs locally and the time is shifted from that of the surrounding area, it is not selected. At this time, by inserting the number of detections into the time quality evaluation value, even a smart meter with a small number of detections but a small time difference from the surroundings is left as a reference clock candidate. A specific example will be described with reference to FIG.

In FIG. 12, it is assumed that the smart meters 2 ₂ and 2 ₃ are affected by noise, and the time is advanced by 10 seconds from the surroundings. The signal transmitted from the smart meter 2 ₁ reaches only the smart meter 2 _{12, the} signal transmitted from the smart meter 2 ₄ reaches only the smart meter 2 ₁₁ , and the signal transmitted from the smart meter 2 ₂ is transmitted to the smart meter 2. ₃ , 2 ₆ , 2 ₇ and 2 ₈ , and the signal transmitted by the smart meter 2 ₃ reaches the smart meters 2 ₂ , 2 ₈ , 2 ₉ , and 2 ₁₀ . At this time, if the difference in time is within the specified value (here, assumed to be 5 seconds), it becomes like the “evaluation value (case in which the number of detections are not included)” in the table shown in FIG. The evaluation values of the smart meters 2 ₂ and 2 _{3 that} are affected by and the smart meters 2 ₁ and 2 ₄ that are not affected are the same. By putting the number of detections in the evaluation value, as shown in the “evaluation value (case including the number of detections)” in the table shown in FIG. 12, the evaluation of the smart meters 2 ₂ and 2 ₃ affected by noise Since the value is lowered, it is not possible to select a smart meter having a time lag.

As described above, in the wireless mesh network according to the present embodiment, the host device 1 manages the correct time among the smart meters 2 provided with the power-synchronous clock that is a highly accurate clock. To adjust the own time to synchronize with the local time of the selected smart meter 2, and to distribute the information of the adjusted time in the wireless mesh network so that the local time is synchronized with the own time. It was decided to instruct the smart meter 2. Further, as the smart meter 2 managing the correct time, a smart meter 2 having a small number of hops from itself and good wireless communication quality, and having a small error between the local time and the local time of the surrounding smart meter 2 is selected. It was decided. Thereby, for example, even when the host device 1 is installed in a place where it is difficult to obtain correct time information from an external NTP server, the reference time managed by the host device 1 is adjusted to the correct time. In addition, it is possible to resynchronize the time of the smart meter 2 in which a shift occurs due to the influence of noise with the reference time.

Embodiment 2. FIG.
In the operation for maintaining the state in which time synchronization is established (the operation shown in FIGS. 9 and 10), the host device 1 according to the first embodiment selects the time information acquisition source candidate in the same procedure every time. A peripheral search is instructed for each selected candidate, and time quality evaluation values are collected. However, the place where each smart meter 2 is installed is less likely to change, and the place such as an inverter that is a source of noise is less likely to change. That is, the smart meter 2 in which the local time is shifted is always likely to be the same. For this reason, for example, for the smart meter 2 that has transmitted a time quality evaluation value lower than a predetermined allowable value, the host device 1 preliminarily obtains the time information acquisition source candidate from the next time synchronization control. You may make it exclude. Thereby, it is possible to prevent an unnecessary peripheral search sequence from being executed.

In addition, when a time quality evaluation value lower than the allowable value is transmitted only once, it is not immediately excluded from the candidates, but when the number of times of transmission of the time quality evaluation value lower than the allowable value reaches a certain value You may make it exclude from.

Embodiment 3 FIG.
In the operation for maintaining the state in which time synchronization is established (the operation shown in FIGS. 9 and 10), the host device 1 according to the first and second embodiments selects all the candidates for the time information acquisition source, The candidate is instructed to search the surroundings in order, and the time quality evaluation value is acquired. However, when a time quality evaluation value satisfying a certain condition is received, for example, the received time quality evaluation value is found to be five or more smart meters 2 and the same time as all the smart meters 2 found. , The local time of the smart meter 2 that is the transmission source of the time quality evaluation value is likely to be correct. Therefore, it may be decided to acquire time information from the smart meter 2 that is the transmission source of the time quality evaluation value that satisfies a certain condition, and the peripheral search may not be instructed for the remaining candidates. As a result, it is possible to avoid unnecessary searching around and prevent traffic from increasing.

At this time, after selecting the time information acquisition source candidate, the host device 1 may instruct the peripheral search in order from the candidate with the smallest number of hops and good wireless communication quality. This increases the possibility of receiving a time quality evaluation value that satisfies a certain condition earlier and determining the acquisition source of time information, thereby reducing the time required to determine the acquisition source of time information. Further, it is possible to avoid performing an unnecessary peripheral search.

Embodiment 4 FIG.
The host device 1 according to the first, second, and third embodiments sets the time information acquisition source candidate as the latest radio in the operation for maintaining the state in which time synchronization is established (the operation illustrated in FIGS. 9 and 10). The selection was made based on the communication quality. However, wireless communication quality is unstable and may vary with time. Therefore, each time the host device 1 receives the meter reading value and the wireless communication quality from each smart meter 2, the upper level device 1 determines the network status table (FIG. 8) based on the number of hops to each smart meter 2 and the received wireless communication quality. Reference) is generated and stored. Then, based on a plurality of network status tables generated after the previous operation for maintaining the state in which time synchronization is established, a candidate for obtaining time information may be selected.

For example, referring to the table having the smallest number of 1-hop smart meters among a plurality of stored network status tables, the source of time information acquisition is in order from the one with the best wireless communication quality among them. Select a candidate. Thereby, the smart meter 2 in which the wireless network status (the number of hops and the wireless communication quality) is stable can be selected.

Or, for example, from the information registered in each of a plurality of stored network status tables, for each smart meter 2, the number of times of one hop and the number of times that wireless communication quality is the best (any of the other smart meters 2 The number of times when the wireless communication quality is better than) is calculated, and the candidate of the acquisition source of the time information is selected in order from the smart meter having the largest total value of both. Also in this case, the smart meter 2 whose wireless network status is stable can be selected.

In order to simplify the description, in each embodiment, the wireless mesh network has been described as being formed by the host device 1 and the smart meter 2, but is transmitted and received between the host device 1 and the smart meter 2. A relay device that relays data (for example, a device having a configuration in which the measuring unit 24 is removed from the smart meter) may be included in the wireless mesh network.

In each embodiment, the timekeeping unit 21 of each smart meter 2 has been described as a power-synchronized timepiece. However, as the timekeeping unit 21, even when a radio timepiece is used for each smart meter 2, Depending on the installation environment of the meter 2, since radio waves cannot be received, the time of the smart meter may be greatly shifted as in the case of power supply system noise of the power supply synchronization method. The present invention can also be applied to the case where such a radio timepiece is used for each smart meter 2, and the same effect can be achieved.

As described above, the communication device according to the present invention is useful as a communication device for managing a reference time in an automatic meter reading system using a wireless mesh network.

DESCRIPTION OF SYMBOLS 1 Host apparatus, 2 ₁ to 2 ₁₂ Smart meter, 11, 21 Time measuring part, 12, 22 Time synchronization control part, 13 Synchronization partner determination part, 14 Data collection part, 15 Network management part, 16, 25 Wireless communication part, 23 Time evaluation unit, 24 weighing unit, 25 route management unit.

Claims (12)

1. A communication device that forms a wireless mesh network with each smart meter,
   Based on at least one of the number of hops to each smart meter and the wireless communication quality with each smart meter, a candidate for a reference smart meter that synchronizes the local time of its own device from each of the smart meters. Select the standard candidate smart meter to be
   A synchronization partner determination unit that determines the reference smart meter based on the local time of the reference candidate smart meter and the local time of each smart meter with which the reference candidate smart meter can directly communicate;
   The local time of the own device is adjusted to synchronize with the local time of the reference smart meter, and further, the local time information of the own device is distributed to at least each of the smart meters other than the reference smart meter in the wireless mesh network. A time synchronization control unit,
   A communication apparatus comprising:
2. The synchronization partner determination unit
   From the reference candidate smart meter, the local time of the reference candidate smart meter obtained by comparing the local time of the reference candidate smart meter with the local time of each smart meter with which the reference candidate smart meter can directly communicate. Obtain a time quality evaluation value indicating the reliability of each time,
   Determining the reference candidate smart meter whose time quality evaluation value is the highest reliability value as the reference smart meter;
   The communication apparatus according to claim 1.
3. The synchronization partner determination unit
   Priority is given to those with a small number of hops, and if the number of hops is the same, priority is given to those with good wireless communication quality, and the reference candidate smart meter is selected.
   The communication device according to claim 2.
4. The synchronization partner determination unit
   Each time the wireless communication quality between each smart meter is measured, a table storing the measured wireless communication quality and the number of hops to each smart meter is stored.
   Refers to the table with the smallest number of registered 1-hop smart meters among the tables stored after the previous process of determining the smart meter to synchronize the local time of its own device, and the 1-hop wireless communication quality In order from the best, select the reference candidate smart meter,
   The communication device according to claim 2.
5. The synchronization partner determination unit
   Each time the wireless communication quality between each smart meter is measured, a table storing the measured wireless communication quality and the number of hops to each smart meter is stored.
   From the information registered in each of the tables stored after the previous process of determining the smart meter that synchronizes the local time of its own device, the number of 1 hops and the wireless communication quality are the best for each smart meter. The number of times is calculated, and the reference candidate smart meter is selected in order from the smart meter having the largest total value of the two calculated values.
   The communication device according to claim 2.
6. The synchronization partner determination unit
   Among the smart meters whose time quality evaluation values have been calculated in the past, smart meters whose time quality evaluation values calculated in the past are lower than a predetermined allowable value are excluded in advance from the reference candidate smart meter. deep,
   The communication device according to any one of claims 2 to 5, wherein:
7. The synchronization partner determination unit
   In turn for each of the selected reference candidate smart meters,
   From the reference candidate smart meter, the local time of the reference candidate smart meter obtained by comparing the local time of the reference candidate smart meter with the local time of each smart meter with which the reference candidate smart meter can directly communicate. Instructed to calculate the time quality evaluation value indicating the reliability of each time,
   When the smart meter that has calculated the time quality evaluation value reaching a certain value is detected, the detected smart meter is determined as the reference smart meter.
   The communication apparatus according to claim 1.
8. The synchronization partner determination unit
   Instructing each of the selected reference candidate smart meters to calculate the time quality evaluation value in order from the wireless communication quality that is the best,
   The communication apparatus according to claim 7.
9. In an automatic meter reading system, a smart meter that forms a wireless mesh network with a host device that collects meter reading values,
   A time evaluation unit that calculates a time quality evaluation value indicating the reliability of its own local time based on the local time of each of the other smart meters capable of direct communication and its own local time, and transmits the time quality evaluation value to the host device.
   A smart meter characterized by comprising:
10. The time evaluation unit
    The local time of the local device is individually compared with the local time of other smart meters capable of direct communication, and the smart meter whose local time is synchronized with the local time of the local device Information indicating how many units are present in the smart meter, and the time quality evaluation value,
    The smart meter according to claim 9.
11. A wireless mesh network configured to include each smart meter and a host device that collects meter reading values from the smart meter,
    The smart meter is
    A time evaluation unit that calculates a time quality evaluation value indicating the reliability of its own local time and transmits it to the host device;
    The host device comprises:
    Based on at least one of the number of hops to each smart meter and the wireless communication quality between each smart meter, a reference candidate smart meter that is a candidate for time synchronization reference is selected from each smart meter; A synchronization partner determination unit that determines the reference smart meter based on the time quality evaluation value calculated by the selected reference candidate smart meter;
    The local time of the own device is adjusted and synchronized with the local time of the reference smart meter, and information on the local time of the own device is distributed to each smart meter other than the reference smart meter in the wireless mesh network. A time synchronization control unit;
    A wireless mesh network comprising:
12. The wireless mesh network according to claim 11, wherein the reference candidate smart meter calculates a time quality evaluation value from a local time of each of the smart meters other than itself capable of directly communicating with the reference candidate smart meter and its own local time. .

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