JP6180305B2 - COMMUNICATION DEVICE, COMMUNICATION METHOD, AND COMMUNICATION SYSTEM - Google Patents

Description

  The present invention relates to a communication apparatus, a communication method, and a communication system suitable for application to, for example, an ad hoc network.

  An ad hoc network is one of network construction methods using various types of wireless communication, and is configured by autonomously connecting wireless communication devices without requiring a dedicated base station or router. It is a network. Ad hoc networks often do not require routing settings and the like for routers and communication devices as compared to infrastructure networks in which data communication is performed via access points.

  In an ad hoc network, communication devices that exist in places where radio waves do not reach each other cannot directly transmit and receive data. Therefore, in an ad hoc network, generally, a communication device that exists within a wireless reachable range serves as a relay, and performs multi-hop communication that transfers data like a so-called bucket relay.

  One application form of such an ad hoc network is a sensor network. If an ad hoc network is used, the sensor network can easily construct a large-scale sensor network including a large number (several hundreds or more) of communication devices including sensors and a data collection device. This sensor network has a network configuration in which a large number of communication devices can simultaneously transmit sensing data including sensor information measured by the sensors to the data collection device. In the following description, sensing data, path control data for constructing a communication path of an ad hoc network, and the like are collectively referred to as “data”.

  The sensor network is mainly used in a communication system that collects data from a large number of communication devices within a predetermined time. For example, a sensor network is used for a remote monitoring system such as a factory or a building, a smart grid system for power control, a state monitoring system for monitoring various states of a house, and the like. Here, the remote monitoring system is a system that collects data including security information such as temperature information acquired from a device in a building, image data taken by a monitoring camera, and the state monitoring system is a home appliance in a house. This system collects data such as the amount of power used.

  When a large number of communication devices constituting the sensor network are in a network environment with a narrow communication band and a low communication speed, a transmission timing control technique such as TDMA (Time Division Multiple Access) is applied. When TDMA is applied, the communication apparatus needs to adjust the transmission / reception timing of data performed with other communication apparatuses.

  However, in a network in which multi-hop communication is performed, communication quality is likely to fluctuate because physical environment fluctuations and communication circuit characteristics are intertwined in a complicated manner. For this reason, the communication time required from the data transmission source to the final destination and the degree of success or failure of communication fluctuate, and it is difficult to maintain a certain accuracy in communication.

  As a method for improving communication quality under such an environment, a technique disclosed in Patent Document 1 is known. This technology measures the network performance and automatically obtains the optimal response waiting time, retransmission interval, and number of retransmissions, and modifies the transmission parameters described in the transmission parameter table, thereby transmitting data with the optimal transmission parameters. Is to do.

JP-A-6-252978

  As described above, in the sensor network, the data collection device collects data from a number of communication devices within a predetermined time. For this reason, each communication apparatus is controlled to transmit data at the transmission timing assigned to each communication apparatus. In this way, in the sensor network, in addition to controlling the transmission timing and efficiently transmitting data to the communication device, data collision can be prevented by dynamically changing the transmission channel or assigning a specific channel. There is a device to communicate without waking up.

  Here, when constructing a communication path in a commonly used communication system, the radio wave intensity and communication quality in each communication path is calculated, and if the communication path is unstable and communication becomes difficult, Control for changing to another communication path (such control is referred to as “path change”) is performed. In a general communication system, such a route change is performed so that stable data collection can be continued.

  However, in a sensor network constructed with an ad hoc network, frequent route changes may be rejected to reduce the data collection rate. Here, the data collection rate is a ratio indicating how many communication devices the data collection device has collected from all communication devices per unit time. When the data collection device can collect data from all the communication devices per unit time, the data collection rate becomes 100%, and the data collection rate decreases according to the number of communication devices that could not collect data.

  As described above, a major factor that decreases the data collection rate is that the above-described transmission timing control and channel control are performed also in the sensor network. For example, when the route of a communication device belonging to the sensor network is changed, it is necessary to change the transmission timing or the transmission channel. Furthermore, it may be necessary to change the transmission timing and transmission channel for another communication device that communicates via the communication device whose route has been changed. In the following description, making all of these changes is defined as “network reconstruction”.

  If this network reconfiguration takes a long time, the communication device cannot transmit data at an appropriate transmission timing during the network reconfiguration, and the data collection rate decreases. In order not to reduce the data collection rate, it is necessary to change the route so that the time for network reconstruction is minimized.

  Here, in the technique disclosed in Patent Document 1, it is only studied to adjust the retransmission interval and the number of retransmissions between one-to-one communication apparatuses connected by wire. For this reason, it has not been considered to change the route so that the data collection rate in the sensor network does not decrease under the conditions of performing transmission timing control and channel control.

  The present invention has been made in view of such a situation, and an object thereof is to change a route without reducing the data collection rate.

The present invention belongs to the first network, and transmits / receives data to / from other communication apparatuses via a communication path mutually established by wireless communication.
Next, a data transmission amount is obtained for each data type of data to be transmitted to another communication device, and when the data transmission amount per unit time of data completed in the past is less than the data allowable value, from the other communication device A data allowance value determination process for determining that a route change is necessary when the continuous data in a predetermined period requested for transmission is transmitted and the data transmission amount of the requested data is less than the data allowance value; or Determine the change in the number of hops based on the network topology change factor of one network, change the communication route in the order of no change in the number of hops, a decrease in the number of hops, and an increase in the number of hops. The priority for route change that specifies the relative difference in network reconfiguration time required for construction is determined high, and the determined priority is specified in advance. If the priority is higher than the specified priority, it is necessary to change the route, and if the determined priority is the same as or lower than the priority specified in advance, the route is not required and the network determines whether the communication route can be changed. Whether or not the communication path can be changed is determined by at least one of the reconstruction time determination processes .
Then, based on the result of measuring the communication performance in the communication path, the communication path for constructing the first network is determined, and when it is determined that the path change is necessary, the communication path is changed, 1 network is reconstructed.

  According to the present invention, if the communication performance of the communication path decreases, the first network can be reconstructed without reducing the data collection rate by changing to a communication path with better communication performance.

It is a block diagram which shows the example of the network topology used for the ad hoc network which concerns on one Embodiment of this invention. It is a system configuration figure showing an example of composition of a sensor network communication system concerning one embodiment of the present invention. It is a block diagram of the network topology applied to the sensor network communication system which concerns on one Embodiment of this invention. It is a table block diagram which shows an example of the ad hoc network communication path candidate table which concerns on one Embodiment of this invention. It is a table block diagram which shows an example of the communication history table which concerns on one Embodiment of this invention. It is a table block diagram which shows an example of the communication path | route table which concerns on one Embodiment of this invention. It is a flowchart which shows the process example of the path | route change possibility judgment function part which concerns on one Embodiment of this invention. It is a flowchart which shows the detailed process example of the data allowable value judgment process which concerns on one Embodiment of this invention. It is a flowchart which shows the detailed process example of the past performance confirmation process which concerns on one Embodiment of this invention. It is a flowchart which shows the detailed process example of the network reconstruction time judgment process which concerns on one Embodiment of this invention.

Hereinafter, a sensor network communication system constructed using an ad hoc network according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Before describing the system configuration of the sensor network communication system according to the present embodiment, the premise of the configuration and operation of the ad hoc network employed in the sensor network communication system will be described with reference to FIG.

[Ad hoc network overview]
First, an outline of the configuration and operation of an ad hoc network will be described.
FIG. 1 shows an example of a network topology used for an ad hoc network. FIG. 1A shows an example of a network topology, and FIG. 1B shows an example of data transmission timing.
The network topology represents a logical communication path of data, and is a concept different from a communication path that physically connects communication apparatuses by wireless or wired communication.

  A tree-type network topology 1 shown as one form of an ad hoc network is applied to a sensor network communication system 10 (see FIG. 2) as described later. This network topology 1 is configured by combining two tree-type network topologies 2A and 2B shown in FIG. 1A. The network topology 2A includes communication devices 3A, 3C, 3E, and 3F, and the network topology 2B includes communication devices 3B, 3D, 3G, and 3H (in FIG. 1, “A” to “H” are shown for each node). )

  The communication device 3A is a data collection device that collects data from the communication devices 3C, 3E, and 3F, and is a gateway device (in the figure, abbreviated as “GW1”) that serves as an interface to another network (for example, the network topology 2B). .). The communication device 3B is a data collection device that collects data from the communication devices 3D, 3G, and 3H, and is a gateway device (in the figure, abbreviated as “GW2”) that serves as an interface to another network (for example, the network topology 2A). .).

  In the following description, in the network topology 1, when the communication devices 3C and 3D are used as a reference, the communication devices 3A and 3B, which are GW1 and GW2 that collect data at the top end of the tree, are referred to as “upper communication devices. Also called. Further, when the communication devices 3C and 3D are used as a reference, the communication devices 3E, 3F, 3G, and 3H located on the end side of the tree are also referred to as “lower communication devices”.

By the way, as shown in FIGS. 1A and 1B, each of the communication devices 3C to 3H is provided with a time slot (abbreviated as “TS” in the figure), and communication is performed by TDMA. These time slots can be identified by any of numbers (1) to (5).
Specifically, one time slot (1) is assigned to the communication device 3C located immediately below the communication device 3A. Two different time slots (2) and (3) are assigned to the communication device 3E located immediately below the communication device 3C, and two different time slots (2) are assigned to the communication device 3F located directly below the communication device 3C. 4) and (5) are given.
Time slots (1) to (5) are also assigned to the communication devices 3D, 3G, and 3H of the network topology 2B.

  The communication devices 3A and 3B are not provided with any time slot for wireless transmission. This is because the communication devices 3A and 3B are separately provided with a communication function unit for transmitting data to a server (not shown) (for example, a management server SV1 which will be described later) higher than the communication devices 3A and 3B. is there. The communication devices 3A and 3B can transmit data to a server or the like (not shown) using this communication function unit.

The communication devices 3C to 3H will be described again. The time slot numbers assigned to the communication devices 3C to 3H indicate the data transmission timing based on the reference time, and all the communication devices 3A to 3H share the reference time. This reference time elapses in the order of the time slot numbers shown in FIG. 1B.
Then, the communication devices 3C to 3H execute processing in the order of the number of the time slot assigned to each. For example, each of the communication devices 3C, 3E, 3F included in the network topology 2A, when the reference time corresponding to the assigned time slot number arrives, holds the data (for example, measurement received from a sensor (not shown)). Data) to the higher-level communication device. The final destination of data transmitted from each of the communication devices 3C and 3E is the communication device 3A.

Specifically, as shown in FIG. 1B, when the time corresponding to the time slot (1) arrives, the communication device 3C transmits data collected from a sensor (not shown) to the upper communication device 3A. . Next, when the time corresponding to the time slot (2) arrives, the communication device 3E transmits data collected from a sensor or the like (not shown) to the upper communication device 3C. Next, when the time corresponding to the time slot (3) arrives, the communication device 3C transfers the data received from the lower communication device 3E to the upper communication device 3A. In this way, the data collected from the sensor or the like by the communication device 3E is transmitted to the communication device 3A with the transmission timing controlled.
In the time slots (4) and (5), as in the case of the time slots (2) and (3), control is performed so that the communication device 3F transmits data collected from a sensor (not shown) to a higher-level communication device. Is called.
In addition, the communication devices 3D, 3G, and 3H included in the network topology 2B perform the same operations as the communication devices 3C, 3E, and 3F included in the network topology 2A.

  In the example shown in FIG. 1B, the communication devices 3C, 3E, 3F and the communication devices 3D, 3G, 3H all transmit data in the same time slot. Although the two network topologies 2A and 2B are different, there is a possibility that data transmitted at the same timing may collide when the times are completely the same. That is, as shown in FIG. 1B, the communication devices 3C and 3D belong to different network topologies 2A and 2B, respectively, but transmit data in the same time slot (1), so data may collide.

  As one of solutions for avoiding such data collision, there is a method of changing channels such as frequencies used for data communication. For example, the channel topology 2A is set to use channel 1, and the network topology 2B is set to use channel 2. Different channels used in the network topologies 2A and 2B can prevent collision of data transmitted at the same transmission timing.

  Further, as one of solutions for avoiding data collision, there is a method of changing a channel used for data communication for each communication path. For example, the communication path between the communication apparatuses 3A and 3C is channel 1, the communication path between the communication apparatuses 3C and 3E is channel 2, and the communication path between the communication apparatuses 3C and 3F is channel 3. Similarly, the communication path between the communication apparatuses 3B and 3D is channel 4, the communication path between the communication apparatuses 3D and 3G is channel 5, and the communication path between the communication apparatuses 3D and 3H is channel 6. In this way, if six different channels are used for data transmission for each communication path, collision of data transmitted at the same transmission timing can be prevented.

[Configuration example of sensor network communication system]
Next, a sensor network communication system 10 according to an embodiment of the present invention will be described.
FIG. 2 is a system configuration diagram illustrating a configuration example of the sensor network communication system 10.

  The sensor network communication system 10 (an example of a communication system) is configured by combining an ad hoc network AN (an example of a first network) and infrastructure networks IN1 and IN2 (an example of a second network). This ad hoc network AN has a network topology similar to the network topology 1 shown in FIG. The two communication devices T1 and T2 belonging to the ad hoc network AN can transmit / receive data to / from each other using a predetermined communication method via a communication path wirelessly connected to each other.

  The infrastructure networks IN1 and IN2 are networks different from the ad hoc network AN configured by the communication devices T1 and T2. The infrastructure networks IN1 and IN2 are configured by various networks such as a cellular phone communication network, an optical line network, or a public wireless LAN (Local Area Network), and a router, an access point, etc. (not shown) are installed.

  The communication device T1 is connected to the management server SV1 via the infrastructure network IN1, and is also connected to the management server SV2 via the infrastructure network IN2. The management servers SV1 and SV2 collect data from the communication device T1 via the infrastructure networks IN1 and IN2, respectively.

  The communication device T2 shows a part of a large number of communication devices (not shown). In the ad hoc network AN constructed with the communication device T1, the communication device T2 is higher or lower in relation to the communication device T1. Used as a communication device. When the communication device T2 is higher than the communication device T1, the communication device T2 is used as a data collection device, and the communication device T1 transmits data to the communication device T2. On the other hand, when the communication device T2 is lower than the communication device T1, the communication device T1 is used as a data collection device. At this time, the communication device T1 collects data from the communication device T2, and transmits the collected data to the management server SV1 via the infrastructure network IN1.

  In the following description, the communication device T1 is mainly described, and the detailed description of the communication device T2 having the same configuration as the communication device T1 is omitted. Actually, it is assumed that there are a large number of communication devices (not shown) configuring the ad hoc network AN in addition to the communication devices T1 and T2.

<Description of communication device>
First, a configuration example and an operation example of the communication device T1 will be described.
The communication device T1 includes a communication device interface 11 (indicated as “communication device IF” in FIG. 2), a central processing unit 12, an internal memory 13, and a storage unit 14. The communication device T1 is connected to the infrastructure networks IN1 and IN2 and the communication device T2 via the communication device interface 11.

  The communication device interface 11 transmits data via a communication path mutually established by wireless communication with the communication device T2 at the higher level. The communication device interface 11 includes a first communication interface 11a (denoted as “first communication IF” in FIG. 2) that transmits and receives data via a communication path for configuring the ad hoc network AN and performing data communication. . In addition, the communication device interface 11 is connected to the infrastructure networks IN1 and IN2 to transmit and receive data via a communication path for performing data communication (in FIG. 2, “second communication IF”). Notation).

As the first communication interface 11a, for example, an ad hoc mode of wireless LAN, specific low power wireless communication, or a dedicated network device may be used.
In addition, the communication device interface 11 can perform various communication controls such as selection, disconnection, data transmission / reception, communication availability determination, and communication volume measurement of the infrastructure networks IN1 and IN2 via the second communication interface 11b. it can.

  For the central processing unit 12, for example, a CPU (Central Processing Unit) is used. Various programs included in the communication device T1 are stored in the storage unit 14, and are read into the central processing unit 12 via the internal memory 13 and executed as necessary.

The storage unit 14 stores an ad hoc network communication control function unit 15, a route change availability determination function unit 16, and a communication control function unit 17 as programs.
Instead of these programs, the functions of the respective functional units may be realized using a dedicated hardware device that can execute at least a part of these functions.

  Further, the ad hoc network communication path candidate table 18, the communication history table 19, and the communication path table 20 used for various controls are also stored as data in the storage unit 14. The contents of each table are updated as appropriate according to the communication status.

Here, an outline of each table stored in the storage unit 14 will be described.
The ad hoc network communication path candidate table 18 is used for managing information necessary for the communication apparatus T1 to communicate with another communication apparatus (communication apparatus T2 in FIG. 2) around the communication apparatus T1. This information includes information such as the communication quality of the communication path established with the upper communication device T2 existing in the vicinity of the communication device T1.

  The communication history table 19 is used to manage the data type of data transmitted by the communication device T1 to the higher-level communication device T2 in unit time, the communication device that is the destination, the success or failure of data transmission, and the like. The data type includes the type of data that the communication device T1 transmits to the management server SV1 or the communication device T2, sensor information, path control information, communication performance information, instruction information received from the management servers SV1 and SV2, and firmware update information. Etc. are included.

  The communication path table 20 is a so-called routing table, and is used, for example, to manage to which communication device the communication device T1 should transmit data among communication devices belonging to the ad hoc network AN. Since the ad hoc network AN is composed of a large number of communication devices, it is important to predetermine communication devices to which data should be transmitted with priority.

Among these tables, the ad hoc network communication path candidate table 18 corresponds to the ad hoc network communication control function unit 15, and data is read or written according to the processing of the ad hoc network communication control function unit 15.
The ad hoc network communication route candidate table 18 and the communication history table 19 correspond to the route change possibility determination function unit 16, and data is read or written according to the processing of the route change possibility determination function unit 16.
The communication path table 20 corresponds to the communication control function unit 17, and data is read or written according to processing of the communication control function unit 17.

Next, an outline of each functional unit stored in the storage unit 14 will be described.
The ad hoc network communication control function unit 15 (an example of a first network communication control unit) is in charge of communication control necessary when the communication device T1 establishes an ad hoc network AN with the communication device T2. The ad hoc network communication control function unit 15 determines a communication path for constructing the ad hoc network AN based on the result of measuring the communication performance in the communication path. When the route change possibility determination function unit 16 determines that a route change is necessary, the communication route is changed to reconstruct the ad hoc network AN.

  At this time, the ad hoc network communication control function unit 15 performs detection of the communication device T2, construction of the ad hoc network communication path candidate table 18, and the like using a routing protocol. For example, AODV (Ad hoc On-Demand Distance Vector) or OLSR (Optimized Link State Routing Protocol) is used as the routing protocol.

The route change possibility determination function unit 16 determines whether or not the communication route can be changed based on a predetermined condition. This predetermined condition includes at least one determination process among a data allowable value determination process, a past performance confirmation process, and a network reconstruction time determination process. Although details will be described later, the data allowance value determination process is a process for determining a change in the communication path when the data transmission amount of data that has been transmitted in the past is smaller than the data allowance value. The past performance confirmation process is a process for determining a change in the communication path based on the performance of the communication path changed in the past. The network rebuilding time determination process is a process of determining a change in the communication path based on a network rebuilding time required to change the communication path and rebuild the ad hoc network AN.

  For this reason, the route change possibility determination function unit 16 acquires the data type of the data received from the lower communication device via the communication device interface 11 during a predetermined period, and sends it to the higher communication device T2 based on this data type. Acquires success or failure of data transmission when data is transmitted. Further, the route change possibility determination function unit 16 stores the acquired data type and success / failure of data transmission in the communication history table 19 in the communication route read from the ad hoc network communication route candidate table 18.

Further, the route change possibility determination function unit 16 acquires a setting value necessary for determining whether a route can be changed from a higher-level communication device through the communication device interface 11, and stores the setting value in a table (not shown) in the storage unit 14. Let This set value includes a transmission threshold, a degree threshold, a data transmission amount, and the like as shown in FIGS. The communication device T1 can receive setting values from the management server SV1 via the infrastructure network IN1, and can also receive setting values from the communication device T2 via the ad hoc network AN. Then, the route change possibility determination function unit 16 determines whether or not the route should be changed based on the contents of the communication history table 19 and the setting values stored in the storage unit 14.
An example of processing performed by the route change possibility determination function unit 16 will be described in detail later.

  The communication control function unit 17 is performed via the infrastructure network IN1 and controls communication with the management server SV1 that manages the configuration of the ad hoc network AN. At this time, the communication control function unit 17 transmits the communication information of the ad hoc network AN and the data collected from other lower communication devices to the management server SV1 through the communication path of the infrastructure network IN1. Examples of the communication protocol used for this communication control include TCP / IP (Transmission Control Protocol / Internet Protocol). However, other communication protocols may be used for communication control. The communication control function unit 17 can also transmit the above data to the management server SV2 via the communication path of the infrastructure network IN2.

<Description of management server>
Next, a configuration example and operation of the management server SV1 will be described.
The management server SV1 includes a management server interface 21, a central processing unit 22, an internal memory 23, and a storage unit 24.

  The management server interface 21 selects various infrastructure networks IN1 and IN2 to be connected, disconnects communication with the infrastructure networks IN1 and IN2, transmits / receives data to / from the communication device T1, determines whether communication is possible, and measures the amount of communication. Perform communication control.

  The storage unit 24 stores a communication control function unit 25 as a program. The communication control function unit 25 is executed by the central processing unit 22 read from the storage unit 24 via the internal memory 23 as necessary. In addition, a condition setting accumulation table 26, a communication path table 27, and a connected communication device management table 28 used for various controls are stored in the storage unit 24 as data.

  The communication control function unit 25 performs communication control when communicating with the communication device T1 via the infrastructure network IN1. The communication control function unit 25 also generates a condition setting accumulation table 26, a communication path table 27, and a connected communication device management table 28 in the storage unit 24.

  Here, in the condition setting accumulation table 26, setting values and the like necessary for establishing a communication path when the communication devices T1 and T2 autonomously determine whether or not to change the path are processed by the communication control function unit 25. Saved by.

The communication path table 27 manages what communication path the communication apparatuses T1 and T2 are connected to in the ad hoc network AN.
The connected communication device management table 28 manages what communication devices T1 and T2 that constitute the sensor network communication system 10 are. The connected communication device management table 28 is generated by organizing communication performance information acquired by the communication control function unit 25 from the communication devices T1 and T2 and various setting information.

Then, the communication control function unit 25 refers to the communication path table 27 and the connected communication device management table 28, and transmits setting values and the like to the communication devices T1 and T2 via the management server interface 21 as necessary.
Note that the program executed by the management server SV1 may be stored in the storage unit 24 in advance, or may be acquired from another management server via a storage medium (not shown) or a communication network and stored as necessary. It may be stored in the unit 24.

[Description of network topology]
FIG. 3 shows a configuration example of the network topology 2C applied to the sensor network communication system 10.

  The network topology 2C has the same configuration as that of the network topology 2A shown in FIG. 1, but three communication devices 3Z1 to 3Z3 and communication for collecting data transmitted by the communication devices 3Z1 to 3Z3 above the communication device 3A. And a device 3I. Here, description will be made assuming that communication device 3A corresponds to communication device T1 shown in FIG. 2, and communication devices 3Z1 to 3Z3, 3I correspond to communication device T2 shown in FIG. Therefore, the communication device 3A is used as a data collection device that collects data from the communication devices 3C, 3E, and 3F, and is further used to transmit data to the communication device 3I used as the data collection device. The description will be made assuming that the communication device 3I is connected to the infrastructure network IN1 with the management server SV1 shown in FIG. 2 and transmits the data collected by the communication device 3I to the management server SV1.

  In the network topology 2C, the communication device 3A constructs an ad hoc network AN with any of the communication devices 3Z1 to 3Z3 and transmits data to the communication device 3I. An ad hoc network AN cannot be constructed with a communication device other than the communication devices 3Z1 to 3Z3 (for example, the communication device 3ZN) because the communication quality is low as described later.

  As described above, all communication devices have a reference time. Then, for example, the communication device 3A transmits data to the communication device 3I via the communication device 3Z1 while the reference time is from 0:00 to 0:30. If the communication quality of the communication path between the communication devices 3A and 3Z1 deteriorates within this period, the communication device 3A autonomously changes the communication route with the communication device 3Z2 or the communication device 3Z3. In the example of FIG. 3, the communication device 3A changes the communication path with the communication device 3Z3, as indicated by the reference time in the drawing. Then, the communication device 3A transmits data to the communication device 3I via the communication device 3Z3 during the reference time from 0:30 to 1:00. Hereinafter, when the communication quality of the communication path decreases within a predetermined period, the communication device 3A autonomously changes to another communication path and transmits data. In this way, the communication device 3A can continue data transmission to the communication device 3I via any one of the communication devices 3Z1 to 3Z3 by the changed communication path.

<Table configuration example>
Here, a detailed configuration example of each table included in the communication device T1 used as the communication device 3A will be described with reference to FIGS.
FIG. 4 shows an example of the ad hoc network communication path candidate table 18.

  The ad hoc network communication route candidate table 18 manages the communication state with the communication devices Z1 to ZN that are higher than the communication device 3A configuring the ad hoc network AN. The ad hoc network communication path candidate table 18 indicates a communication path established with the communication device 3A.

  The ad hoc network communication path candidate table 18 is used when each communication apparatus constructs the network topology 2C using a routing protocol such as OLSR or RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks). The ad hoc network communication path candidate table 18 is created by the ad hoc network communication control function unit 15 by exchanging information such as the communication state and the number of hops between the communication devices constituting the ad hoc network AN. The ad hoc network communication path candidate table 18 holds the upper communication apparatus candidate name 18a, the link state 18b, the hop count 18c, and the communication quality 18d.

The higher-level communication device candidate name 18a is stored as candidates for establishing a communication path of the ad hoc network AN, which belong to the ad hoc network AN and are higher than the communication device 3A.
The link state 18b is information indicating the communication state between the communication devices 3Z1 to 3ZN and the communication device 3A indicated by the higher-level communication device candidate name 18a, and it is possible to determine whether communication is possible based on this information. The communication device 3A can establish a communication path and transmit data to the communication device in which the link state 18b is “present”. The communication device 3A cannot establish a communication path and transmit data to a communication device whose link state 18b is “none”.

  The number of hops 18c indicates how far away the communication devices 3Z1 to 3ZN that are higher than the communication device 3A are when the communication device 3A constructs a tree-type network topology 2C with another communication device. It is the information which shows. Since there is only one communication path between the communication apparatus 3A and the higher-level communication apparatuses 3Z1 to 3ZN, the number of hops is stored as “1” in the ad hoc network communication path candidate table 18. For the communication device 3A, when the communication device 3I as the final destination of data transmission is also stored in the ad hoc network communication route candidate table 18, the number of hops “2” indicating that two communication routes are necessary. "Is memorized.

  The communication quality 18d is obtained by indexing the communication success rate when data is transmitted to the communication device 3A and any of the communication devices 3Z1 to 3ZN indicated by the upper communication device candidate name 18a. The closer the communication quality 18d value is to “0” such as “0.01”, the less suitable for communication, and the closer the communication quality 18d value is “1” to “1”, the more suitable for communication. It is recognized that Therefore, the communication quality 18d indicates that the communication device 3A can satisfactorily communicate with any of the communication devices 3Z1 to 3ZN and cannot establish a communication path with the communication device 3ZN.

FIG. 5 shows an example of the communication history table 19.
The communication history table 19 is information indicating what type of data the communication device 3A included in the network topology 2C transmits to which upper level communication device in a predetermined time zone, and whether or not this data transmission is successful. Is remembered. The communication history table 19 has a reference start time 19a indicating a unit time for performing data transmission on a certain communication path, and a reference end time 19b. The communication history table 19 stores the destination communication device 19c, the data type 19d, and the number of successful transmissions 19e as one set of communication history in one data transmission. Then, when the communication device 3A performs data transmission a plurality of times within the period indicated by the reference start time 19a and the reference end time 19b, the communication device 3A increases the number of communication history sets by the number of times of data transmission. For this reason, the set of the destination communication device 19f, the data type 19g, and the number of successful transmissions 19h indicates a communication history when data transmission is performed just before the reference end time 19b.

The reference start time 19a indicates a start time of a unit time (in this example, 30 minutes) for the communication device 3A to transmit data to any one of the upper communication devices 3Z1 to 3Z3.
The reference end time 19b indicates the end time of this unit time. The reference start time 19a and the reference end time 19b are managed based on the above-described reference time. When the current unit time elapses, management of transmission information is continued in the next unit time.
The destination communication device 19c indicates what communication device is the destination of the data transmitted by the communication device 3A. In unit time, in order to prevent frequent path changes and processing delays, a communication path is maintained with a specific communication device as much as possible. If the communication quality in this unit time is poor, the communication path is changed so that communication is performed with another communication device in the next unit time.

The data type 19d indicates the type of data transmitted from the communication device 3A to the destination communication device. For example, if the data transmitted by the communication device 3A is sensing data, “sensor” is stored in the data type 19d as the data type, and if the data is path control data, “path control” is stored in the data type 19d. The
The successful transmission count 19e indicates the successful transmission count of data transmitted by the communication device 3A. After the communication device 3A transmits data to one of the destination communication devices 3Z1 to 3Z3, when receiving a receipt confirmation (for example, ACK) from this communication device, “1” is written in the transmission success count 19e. Indicates successful transmission. If a receipt confirmation cannot be received after a certain period of time has elapsed after data transmission, “0” is written in the number of successful transmissions 19e, indicating a transmission failure.

  Note that data transmission from the communication device 3A to any one of the higher-level communication devices 3Z1 to 3Z3, which is a destination one hop ahead, is performed many times in a unit time. Then, a field group having “destination communication device”, “data type”, and “successful transmission count” as one set is added to the communication history table 19 by the number of times data transmission is performed per unit time. When the reference end time is reached, the total number of successful transmissions per unit time is calculated. If the ratio of successful transmissions to the number of transmissions is low, the path is changed.

FIG. 6 shows an example of the communication path table 20.
The communication path table 20 stores data when the communication device 3A transmits data to the communication device 3Z1. Then, the communication control function unit 17 refers to the communication path table 20 and transmits data to the communication device 3Z1. The communication path table 20 holds a host communication device name 20a, a transmission timing 20b, and a transmission channel 20c.

  The host communication device name 20a indicates a communication device for which a communication path is defined with the communication device 3A. In this example, the communication device 3Z1 is defined as the upper communication device name 20a, and it is shown that a communication path is established between the communication devices 3A and 3Z1. The communication device 3A can transmit data to the communication device 3I by transmitting data to the communication device 3Z1, and can finally reach the management server SV1 connected to the communication device 3I. Note that when the communication device 3A autonomously changes the communication path, the content of the upper communication device name 20a is also rewritten with the changed name of the communication device.

The transmission timing 20b indicates a transmission timing at which the communication device 3A transmits data to the destination communication device. The numerical value stored in the transmission timing 20b corresponds to the time slot number as shown in FIG. In this example, “2” is stored as the transmission timing 20b.
The transmission channel 20c indicates a channel for the communication device 3A to transmit data to the destination communication device. When the communication path between the communication device 3A and the destination communication device is changed, the transmission channel 20c is also changed. In this example, “1” is stored as the transmission channel 20c.

<Processing example of route change availability determination function unit>
Next, a processing example performed by the route change permission determination function unit 16 included in the communication device T1 used as the communication device 3A will be described with reference to FIG. 7 first, and then with reference to FIGS. Detailed contents will be described. Also in the following description, a case where the communication device T1 transmits data to the higher-level communication device T2 will be described apart from the configuration of the network topology 2C of FIG.

  FIG. 7 is a flowchart illustrating a processing example of the route change possibility determination function unit 16.

  First, the route change possibility determination function unit 16 performs a data allowable value determination process (S1). This process determines whether the data transmission amount of data that has been transmitted in the past is equal to or greater than a transmission threshold value (an example of an allowable data value) of the data transmission amount requested by the sensor network communication system 10, and the data transmission amount is data This is processing for determining that a route change is necessary when the number is smaller than the threshold. This process is performed based on the data transmission amount obtained for each data type of data to be transmitted to another communication device. Such processing is performed because the communication device T1 cannot transmit a sufficient amount of data if the communication quality of the communication path established between the communication device T1 and the upper communication device T2 is low. This is because it is necessary to change to a communication path with high communication quality. Details of this processing will be described later with reference to FIG.

  Further, as will be described later, in the data allowance value determination process (S1), when the data transmission amount is smaller than the data allowance value, continuous data (referred to as recovery data) in a predetermined period requested from another communication device. ) Is transmitted. Even if this processing is performed, it is determined that the path needs to be changed when the data transmission amount of the data requested to be transmitted is smaller than the allowable data value.

  Subsequently, the route change possibility determination function unit 16 determines whether a route change is necessary as a result of determining the data allowable value (S2). When the route change is not necessary (No in S2), the route change possibility determination process is terminated. If a route change is necessary (Yes in S2), the process proceeds to the next past result confirmation process (S3).

  Next, the route change possibility determination function unit 16 performs a past performance confirmation process (S3) of the communication route. This process is a process in which the route change availability determination function unit 16 confirms whether there is a similarity between the route changes made in the same time zone as in the past, and determines that a route change is necessary if there is a similarity. is there. For example, it is known that there is a difference in communication quality of a communication path for each time zone such as day and night and for each season. For this reason, even if the communication quality decreases in a certain time zone, the communication quality may be good in the same past time zone.

  Therefore, the route change possibility determination function unit 16 confirms the communication quality in the past same time zone when the communication quality decreases in a certain time zone. If the communication quality in the past time zone is high, it is considered that the current communication path happens to have a low communication performance. Therefore, processing for changing to a communication path with a high communication quality is performed based on the past performance. Details of this processing will be described later with reference to FIG.

  Subsequently, the route change possibility determination function unit 16 determines whether or not the route change is necessary as a result of confirming the past performance of the communication route (S4). If the route change is not necessary (No in S4), the route change is determined. The change permission determination process is terminated. If a route change is necessary (Yes in S4), the process proceeds to the next network reconstruction time determination process (S5).

  Further, the route change possibility determination function unit 16 performs a network reconstruction time determination process (S5). This process considers the time until the ad hoc network AN returns to the steady state and data transmission is resumed, including all elements such as transmission timing and channel settings, as a result of the route change enable / disable judgment function unit 16 changing the route. Process. Then, it is a process of determining that a route change is necessary only when the reconstruction time of the ad hoc network AN is short. If the reconfiguration time of the ad hoc network AN is long, the time required for the data collection device to collect data will increase accordingly. Therefore, the time required for the route change is shortened as much as possible, and the time required for returning to the steady state is shortened. In order to do this, this processing is performed. Details of this processing will be described later with reference to FIG.

Subsequently, as a result of determining the network rebuilding time, the route change possibility determination function unit 16 determines whether a route change is necessary (S6). When the route change is not necessary (No in S6), the route change enable / disable determining process is terminated. If a route change is necessary (Yes in S6), the process proceeds to a route change process (S7).
Finally, a route change process (S7) is performed. This process is the same as the normal path change process and depends on the communication protocol and system settings.

  As described above, the route change possibility determination function unit 16 performs the data allowance value determination process to determine whether the route change is necessary (S1), and confirms the past results to determine whether the route change is necessary. (S3) The network reconfiguration time is determined to determine whether a route change is necessary (S5). As a result, the route change possibility determination function unit 16 does not determine the route change unless all the three determination processes (S1, S3, S5) are satisfied. However, the route change enable / disable determining function unit 16 may make a route change determination if at least one of the three determination processes (S1, S3, S5) is satisfied.

  Further, the route change possibility determination function unit 16 gives importance to the above-described three determination processes (S1, S3, S5), and if the determination process with high importance is satisfied, the other importance is low. The route change determination may be performed even if the determination processing is not satisfied. Further, when importance is given to the three determination processes (S1, S3, S5), the importance may be changed for each data type. Further, the processing order of the three determination processes (S1, S3, S5) may be arbitrarily changed.

  FIG. 8 is a flowchart showing a detailed processing example of the data allowable value determination processing (S1) in FIG.

  First, the route change possibility determination function unit 16 sets a data type for performing data allowable value determination (S11). As this data type, for example, there are “sensor” and “route control” (see FIG. 5), and a determination process is performed as to whether or not the data transmission amount satisfies the data allowable value for each set data type.

  Subsequently, the route change possibility determination function unit 16 determines whether the allowable value determination is performed for all data types (S12). If the allowable data value has been determined for all data types (Yes in S12), the allowable data value determination process is terminated. If the data allowable value has not been determined for all data types (No in S12), the process proceeds to the calculation of data transmission amount (S13) for the transmission data of the set data type.

  Next, the route change possibility determination function unit 16 calculates a data transmission amount (S13). This process of step S13 calculates the data transmission amount of the data transmitted in the past unit time for each data type. In this process, the route change possibility determination function unit 16 refers to the communication history table 19 shown in FIG. 5 to determine how many times the data of the data type set in step S11 has been successfully transmitted per unit time. It is possible to grasp. Then, the route change possibility determination function unit 16 calculates the data amount of the transmission data for each data type based on the contents read from the communication history table 19. The route change possibility determination function unit 16 can also refer to the communication history table 19 and calculate the number of data transmissions per unit time.

  Subsequently, the route change possibility determination function unit 16 compares the calculated data transmission amount with the transmission threshold value, and determines whether the data transmission amount is smaller than the transmission threshold value (S14). Here, the transmission threshold is used to determine whether or not the data transmission amount of data transmitted in unit time satisfies the data allowable value, and the data allowable value includes the transmission threshold. The fact that the data transmission amount per unit time is equal to or greater than the transmission threshold is referred to as “the data transmission amount satisfies the data allowable value”. For this reason, the communication device T1 is required that the data transmission amount of the data transmitted per unit time satisfies the data allowable value.

  The process of comparing the data transmission amount and the transmission threshold as described above (S14) is performed even if the first data transmission fails, the data that could not be transmitted at the first time by the second and subsequent data transmissions. This is because there is a possibility of transmission. For example, it is assumed that the data transmitted from the communication device T1 to the higher-level communication device T2 at one time always includes the data transmitted over the past six times. At this time, even if the communication device T1 fails to transmit data five times consecutively, if the data transmission is successful at the sixth time, the communication device T2 has acquired all the past six data from the communication device T1. The same result. As described above, if the communication device T2 does not always have to acquire the latest data, even if data is continuously lost, the data collection device (for example, the communication device T2) collects data by one successful transmission. The rate can be maintained.

  In the process of comparing the data transmission amount and the transmission threshold value (S14), a constant transmission threshold value is set regardless of the data type and used for the process. However, a different transmission threshold value is provided for each data type, It can also be used for comparison with the data transmission amount. For example, suppose sensor data 1 that includes a measured value of power usage and sensor data 2 that includes a measured value of gas usage. In some cases, the communication device T1 is required to control to transmit one of the sensor data 1 and 2 with priority. In this case, for example, when the power usage data is transmitted with priority, a transmission threshold is set for the sensor data 1, and when the gas usage data is transmitted with priority, the sensor data 2 is transmitted. It is necessary to set a transmission threshold for. Furthermore, the priority of the power usage amount and gas usage amount data may be switched depending on the time zone.

  Here, when the data type is sensor data 1, it is set that there is no problem even if data transmission fails three times continuously in three hours. Further, when the data type is sensor data 2, it is set that there is no problem even if data transmission fails continuously six times during one hour. Thus, by providing different transmission threshold values for each data type, it is possible to maintain or increase the data collection rate of necessary data according to the data type. The sensor data 1 and 2 can include various measurement data such as environmental temperature and environmental humidity in addition to electric power and gas.

Returning to the description of the flowchart of FIG.
When the data transmission amount is equal to or larger than the transmission threshold (No in S14), the route change possibility determination function unit 16 proceeds to the next data type setting (S11) because the data transmission amount for this data type is sufficient. . When the data transmission amount is smaller than the transmission threshold (Yes in S14), the data transmission amount does not satisfy the data allowable value, so the data transmission amount of the recovery data and the transmission threshold of the recovery data (an example of the data allowable value) The process proceeds to the next process (S15).

Here, for example, when the communication device T2 higher than the communication device T1 cannot collect the data in a unit time in a specific time zone, the recovery data is transmitted again to the communication device T1 by the communication device T2. This is data that is instructed to be transmitted and retransmitted to the communication device T1.
When the data transmission failure continues, the communication device T1 is periodically requested to transmit recovery data from the communication device T2, and transmits the recovery data in response to the request. As a result, even if the communication device T1 cannot transmit data in a specific time zone, it retransmits all data as much as possible in another time zone. For example, when transmission of recovery data is requested and transmission of recovery data is successful within 12 hours, there is no need to change the path, but when transmission of recovery data does not succeed even after 12 hours, It is determined that a route change is necessary.

  The path change possibility determination function unit 16 determines whether or not the data transmission amount of the recovery data is smaller than the recovery threshold of the recovery data (S15). If the data transmission amount of the recovery data is equal to or greater than the recovery data transmission threshold (No in S15), the data transmission amount for this data type is sufficient, and the process proceeds to the next data type setting (S11). However, when the data transmission amount of the recovery data is smaller than the recovery data transmission threshold (Yes in S15), it is considered that the communication quality of the communication path is deteriorated. For this reason, the route change possibility determination function unit 16 determines the presence of a route change (S16).

  If the upper communication device T2 does not always have to acquire the latest data in a specific time zone, data that should be received from the communication device T1 in a unit time in the specific time zone was continuously lost. However, it is only necessary that the recovery data can be received in another specific time zone. If the response transmission for one recovery data request from the communication device T2 to the communication device T1 is successful, the data collection rate can be maintained.

  For example, this transmission threshold is provided for each data type, and when the data type is the sensor data 1 described above, it is set that there is no problem even if data transmission fails continuously for 6 hours as a specific time zone. . Similarly, when the data type is sensor data 2, it is set that there is no problem even if 12 data transmissions fail during 24 hours as a specific time zone. The path change possibility determination function unit 16 may determine whether the necessary data transmission amount is satisfied by comparing the data transmission amount of the recovery data with a transmission threshold for each data type of data transmitted as the recovery data. it can.

  FIG. 9 is a flowchart showing a detailed processing example of the past performance confirmation processing (S3) in FIG.

  The past performance confirmation processing is performed by the route change possibility determination function unit 16 when the degree of route change performed during a predetermined period exceeds the degree threshold. Then, the route change possibility determination function unit 16 needs to change the route when the content of the route change made during the predetermined period is similar to the past result of the route change made during the same period as the predetermined period. It will be judged.

  Specifically, the route change possibility determination function unit 16 first determines whether the degree of route change performed per unit time exceeds a degree threshold (S21). Here, the degree of route change is an index indicating how many route changes have been attempted per unit time in the past. When the route is frequently changed, it can be determined that the communication quality of the communication route per unit time is deteriorated.

  In the ad hoc network communication route candidate table 18 and the communication history table 19, the route candidate, the changed communication route, the number of times of route change, and the like are stored as described above. For this reason, the route change possibility determination function unit 16 can determine whether the number of times the route change is attempted per unit time is larger or smaller than the degree threshold. For example, when the unit time is set to 30 minutes, a case is assumed in which twice is set as a degree threshold for performing a route change with the communication device that is the best route candidate per unit time. In this case, it is considered that the degree of route change is high when the route change is performed 12 times with the communication device as the route candidate.

  If the degree of route change does not exceed the degree threshold (No in S21), the past result confirmation process is terminated. If the degree of route change exceeds the degree threshold value (Yes in S21), the process proceeds to detailed storage of route change data (S22).

  Subsequently, the route change availability determination function unit 16 performs detailed storage of route change data (S22). Here, the route change data is information that the ad hoc network communication control function unit 15 acquires along with the route change. The route change data includes the time when the communication device T1 changed the route, the communication device that became the route candidate due to the route change, the communication quality and the link state of the changed communication route, and the like. The route change data is stored in the ad hoc network communication route candidate table 18 and the communication history table 19.

  However, the communication devices T1 and T2 normally used in the sensor network communication system 10 have a small housing size and the like, and the storage capacity of the storage unit 14 is limited. For this reason, a large amount of route change data cannot be stored in the storage unit 14, and only the minimum route change data is concentrated and stored in the storage unit 14. For example, in the detailed saving of the route change data (S22), a process of saving a small amount of route change data in the storage unit 14 by shortening the unit time is performed. Further, even if a small amount of route change data is used, the sensor network communication system 10 as a whole can store a sufficient amount of route change data by increasing the number of communication devices that can store the route change data. .

  The communication device T1 may store the route change data in the large-capacity storage unit 24 by transmitting the data stored in detail in the storage unit 14 to the management server SV1. In this case, the management server SV1 can manage the entire ad hoc network AN by collecting route change data and various tables (see FIG. 2) from all the communication devices constituting the ad hoc network AN.

Returning to the description of the flowchart of FIG.
The route change possibility determination function unit 16 determines whether or not there has been a route change for which a past performance should be confirmed in a specific time zone (S23). When there is no route change for confirming the past performance (No in S23), the past performance confirmation processing is terminated. When there is a route change for which the past performance should be confirmed (Yes in S23), a time axis to be confirmed is set (S24).

Here, whether or not there has been a route change for which past results should be confirmed is indicated by the route change data previously stored in detail, and the same communication device as the route-changed communication device was connected by this route change It is determined by confirming whether it is a communication device.
In this confirmation process, the communication device T1 transmits the route change data to the higher-level communication device T2, and the route change is determined based on the past results confirmed based on the route change data collected by the communication device T2. It can also be realized by transmitting to the communication device T1.

Subsequently, the route change possibility determination function unit 16 sets a time axis and a range for confirming past results (S24). This time axis and range are set in units of, for example, 1 hour, 24 hours, 1 week, and 1 month.
Furthermore, the route change possibility determination function unit 16 determines whether or not the current and past track changes are similar for each time axis within the set range (S25). For example, when the set range is one week and the time axis is one hour, this process is performed seven times.

  When there is no time axis similar to the past record (No in S25), the route change possibility determination function unit 16 proceeds to the determination (S26) of whether the similarity calculation has been completed on all the time axes. If there is a time axis similar to the past performance (Yes in S25), it is determined that there is a route change (S27).

  Finally, the route change possibility determination function unit 16 determines whether the similarity calculation has been completed on all time axes (S26). If the similarity calculation has been completed (Yes in S26), the past performance confirmation process (S3) is terminated. If the similar calculation is not completed (No in S26), the process proceeds to the process of setting the time axis to be confirmed (S24), and the similar calculation in the other time axis is repeated.

  Note that the past performance confirmation process S3 may require a storage unit with a large storage capacity or a central processing unit with high performance for storing history data or determining similarity. However, the communication devices T1, T2 and the like constituting the sensor network communication system 10 are often configured by a storage unit 14 having a low storage capacity and a low-speed central processing unit 12. For this reason, you may comprise the function for performing past performance confirmation process S3 so that a process may be performed by communication apparatus T2 or another alternative apparatus (for example, management server SV1).

  FIG. 10 is a flowchart showing a detailed processing example of the network reconstruction time determination processing (S5) in FIG.

The network reconstruction time determination process is performed by the path change possibility determination function unit 16 that determines a change in the number of hops based on a change factor of the network topology of the ad hoc network AN. The route change allowability determining function unit 16, without change in the number of hops, a decrease in the number of hops, in order of increasing number of hops, and to high rather determines the priority for the route change.

First, the route change possibility determination function unit 16 determines what is the network topology change factor (S31). When the change factor is a new appearance of a communication device (increase in the number of communication devices in S31), the route change possibility determination function unit 16 determines a change in the number of hops (S32). When it is determined that the communication device in which the change factor has existed has disappeared or the link has been broken (disappearance of the communication device in S31), the path change possibility determination function unit 16 determines the change in the number of hops (S3 6 ). Further, the route change possibility determination function unit 16 determines the change in the number of hops even when the change factor is other than the increase or disappearance of the communication device (S40). As a change factor, for example, the installation position of the communication device T1 may be changed.

  Here, fluctuations in the number of hops include an increase and a decrease in the number of hops. “Increase in the number of hops” means, for example, that the communication device T1 becomes a communication path located at a lower position away from the upper communication device T2 than the current position indicated by the network topology. The “decrease in the number of hops” means, for example, that the communication device T1 becomes a communication path located at a higher position closer to the communication device T2 than the current position indicated by the network topology. “No change in the number of hops” means neither an increase nor a decrease in the number of hops, and means that, for example, the number of hops of the communication device T1 does not change.

  The change factor of the network topology is determined by the path change enable / disable determination function unit 16 during the path construction process of the normal ad hoc network AN. In addition to this, by measuring the communication quality of the communication path or notifying that the network topology has changed from the communication apparatus T2 to the communication apparatus T1, the path change permission determination function unit 16 can The change factor may be determined.

  The route change possibility determination function unit 16 determines that the priority is (7) when the hop count increases (S32 increase) in the hop count variation determination (S32) due to the increase in communication devices (S33). . If there is no change in the number of hops (no change in S32), the priority is determined as (1) (S34). When the number of hops decreases (decrease in S32), the priority is determined as (4) (S35).

  Further, in the change determination of the number of hops due to the disappearance of the communication device (S36), the route change possibility determination function unit 16 determines the priority as (9) when the number of hops increases (increase in S36) ( S37). When there is no change in the number of hops (no change in S36), the priority is determined as (2) (S38). When the number of hops decreases (decrease in S36), the priority is determined as (5) (S39).

  The route change possibility determination function unit 16 determines the priority as (8) when the hop count increases (S40 increase) in the hop count variation determination (S40) due to factors other than the increase or disappearance of the communication devices. (S41). If there is no change in the number of hops (no change in S40), the priority is determined as (3) (S42). When the number of hops decreases (decrease in S40), the priority is determined as (6) (S43).

As described above, the route change possibility determination function unit 16 defines the relative difference in the network reconfiguration time by the index called the priority based on the cause of the change in the network topology. This is because the processing performance of the central processing unit 12 provided in the communication device T1 is not sufficient. In this case, performing the process of calculating the network rebuilding time may take time in the low-speed central processing unit 12 or may affect other communication processes. For this reason, the route change availability determination function unit 16 can determine whether or not a route change has occurred in a short time by using a standardized determination process.
Note that the case where there is no fluctuation in the number of hops has the least influence on the transmission timing and channel setting.

Finally, the route change possibility determination function unit 16 performs a process of determining whether or not there is a route change (S44). The route change enable / disable determining function unit 16 determines that there is a route change if the priority is higher than the priority defined in advance by the set value or the like based on the priority determined up to this processing (S44). If the priority is the same or lower than the specified priority, the route is not changed. Here, the priority shown in FIG. 10, (1) the priority is rather low as it approaches, the priority is not high as it approaches the (9).

  This defined priority may be changed dynamically. For example, it is assumed that the network reconstruction time is proportional to the network scale, that is, the number of communication devices included in the sensor network communication system 10. At this time, when the network scale of the ad hoc network AN is small, that is, when the number of communication devices is small, the specified priority is lowered, and the specified priority is increased as the network scale of the ad hoc network AN increases. When the priority defined in this way is changed, if the network scale is small, the time for network reconstruction accompanying the route change is short, so that the data collection rate can be easily maintained. In addition, if the network scale is large, it is possible to prevent the data collection rate from being lowered due to the time required for network reconstruction due to frequent route changes.

  In the present embodiment, the relative difference in network reconfiguration time is defined by an index called priority determined based on the cause of network topology change. However, in addition to the cause of the network topology change, if the network reconstruction time can be assumed for each embodiment in which the ad hoc network AN is used, the priority may be determined based on that time.

  Further, as a condition leading to network reconstruction, it may be permitted to change the route only in the case of a specific network topology. For example, there is a case where the communication device T1 is located at the end of the tree-type network topology, or a case where only a prescribed number of communication devices, for example, only one, are connected to the communication device T1. In this case, even if a communication device lower than the communication device T1 changes the route, the influence range of the route change is narrower and the time until the network reconstruction is completed is shorter than when the communication device T1 changes the route. can do. Therefore, each communication device can transmit data to a higher-level communication device without reducing the data collection rate.

  Furthermore, special conditions such as when there is no sub-route that can transmit data on another communication channel or when the communication device is located at a specific location are specified as conditions for network reconstruction. May be. Such a special case may be designated via the communication device T2 or another communication device.

  According to the sensor network communication system 10 according to the present embodiment described above, when the communication device T1 belonging to the ad hoc network AN autonomously constructs a communication path with another communication device T2, the communication quality deteriorates. The route is changed autonomously. Each of the communication devices T1 and T2 can determine a route change that minimizes the network reconstruction time without reducing the data collection rate. For this reason, each communication device T1, T2 included in the sensor network communication system 10 can perform data transmission without locally reducing the data collection rate required for the entire system. In addition to route changes that take into account normal communication quality and the number of failed data transmissions, an optimal sensor network is constructed by utilizing a route change method that allows the data collection rate to continue at a high value. It becomes possible.

Further, the route change possibility determination function unit 16 according to the present embodiment determines whether or not the communication route should be changed based on a predetermined condition. At this time, as a predetermined condition, by determining whether or not the route can be changed depending on whether the data transmission amount exceeds or does not exceed the data allowable value, the communication route having a low communication performance is quickly changed to the communication route having a high communication performance. It is possible to improve the data collection rate by changing the route.
In addition, as a predetermined condition, determine past communication performance in various time widths, determine that changing the communication path can improve the data collection rate as a result, and determine whether the communication path can be changed Can do. Further, as a predetermined condition, it is possible to determine whether or not the route can be changed depending on how long the network reconstruction time is.
The route change possibility determination function unit 16 can reconstruct the ad hoc network AN without reducing the data collection rate of the entire sensor network communication system 10 by determining whether the route change is possible by combining each condition.

  The management server SV1 can be connected to the infrastructure network to which the communication device T1 belongs, and can collect communication information from all the communication devices T1 and T2 belonging to the ad hoc network AN. Therefore, the management server SV1 grasps the configuration of the ad hoc network AN, distributes setting values for improving the data collection rate to the communication devices T1 and T2, and efficiently uses the ad hoc network AN for the communication devices T1 and T2. Can be reconstructed automatically.

[Modification]
In the sensor network communication system 10 according to the above-described embodiment, the tree-type network topology 2C is applied. However, various network topologies such as a mesh type and a star type can be applied. Further, these various network topologies can be appropriately combined and applied to the sensor network communication system 10.

  It is also possible to grasp the configuration of the ad hoc network AN by installing an analyzer or the like in the ad hoc network AN and acquiring the tables and transmission data stored in the storage units 14 of the communication devices T1 and T2. It is also possible to grasp the configuration of the ad hoc network AN by taking out and analyzing the storage unit 24 of the management server SV1.

  The data collected by the sensor network communication system 10 is not limited to the amount of power and gas used, but may include measurement values of human sensors in the security field.

  Further, the communication path established between the communication devices T1 and T2 may be established by a network using an access point in addition to the ad hoc network AN, for example.

The above-described embodiments are examples for explaining the present invention, and are not intended to limit the scope of the present invention to the embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.
For example, in the above-described embodiment, the configuration of the apparatus and the system is described in detail and specifically in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one having all the configurations described. Absent. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, or replace another configuration for a part of the configuration of each embodiment.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

T1, T2 ... communication device, SV1, SV2 ... management server, 10 ... sensor network communication system, 11 ... communication device interface, 12 ... central processing unit, 13 ... internal memory, 14 ... storage unit, 15 ... ad hoc network communication control function , 16 ... Route change permission determination function unit, 17 ... Communication control function unit, 18 ... Ad hoc network communication route candidate table, 19 ... Communication history table, 20 ... Communication route table

Claims (4)

A communication device interface that transmits data via a communication path that is mutually established by wireless communication with another communication device that belongs to the first network and is located above,
A data transmission amount is obtained for each data type of the data to be transmitted to the other communication device, and the other communication is performed when the data transmission amount in the unit time of the data completed in the past is less than a data allowable value. Data allowance for transmitting continuous data in a predetermined period requested for transmission from a device, and determining that a route change is necessary when the data transmission amount of the requested data is less than the data allowance A change in hop count is determined based on a value determination process or a network topology change factor of the first network, and the communication is performed in the order of no change in the hop count, a decrease in the hop count, and an increase in the hop count. In order to change the route that defines the relative difference in network rebuilding time required to change the route and rebuild the first network A priority is determined to be high, and if the determined priority is higher than a pre-specified priority, a route change is necessary, and the determined priority is determined to be the pre-defined priority. If it is equal to or lower than the degree, the route change is not necessary, and the route change possibility is determined by determining whether the communication route can be changed by at least one of the network rebuilding time determination processing for determining whether the communication route can be changed. A judgment function unit;
Based on the result of measuring the communication performance in the communication path, the communication path for constructing the first network is determined, and when it is determined that the path change is necessary by the path change permission determination function unit, A first network communication control unit for changing the communication path and reconstructing the first network;
A communication device comprising: Further, the communication path of the second network constructed with the management server for managing the configuration of the first network, the communication information of the first network, and from the other communication device that is subordinate The communication apparatus according to claim 1, further comprising a communication control function unit that transmits the collected data to the management server. Transmitting and receiving data via a communication path that belongs to the first network and is mutually established by wireless communication with another communication device;
A data transmission amount is obtained for each data type of the data to be transmitted to the other communication device, and the other communication is performed when the data transmission amount in the unit time of the data completed in the past is less than a data allowable value. Data allowance for transmitting continuous data in a predetermined period requested for transmission from a device, and determining that a route change is necessary when the data transmission amount of the requested data is less than the data allowance A change in hop count is determined based on a value determination process or a network topology change factor of the first network, and the communication is performed in the order of no change in the hop count, a decrease in the hop count, and an increase in the hop count. In order to change the route that defines the relative difference in network rebuilding time required to change the route and rebuild the first network A priority is determined to be high, and if the determined priority is higher than a pre-specified priority, a route change is necessary, and the determined priority is determined to be the pre-defined priority. Determining whether or not the communication path can be changed by at least one determination process among the network reconstruction time determination processes for determining whether or not the communication path can be changed;
Based on the result of measuring the communication performance in the communication path, the communication path for constructing the first network is determined, and when it is determined that the path needs to be changed, the communication path is changed. And reconstructing the first network. A plurality of communication devices belonging to the first network, and a management server belonging to the second network,
The communication device
A communication device interface for transmitting and receiving data via a communication path mutually constructed by wireless communication with other communication devices;
A data transmission amount is obtained for each data type of the data to be transmitted to the other communication device, and the other communication is performed when the data transmission amount in the unit time of the data completed in the past is less than a data allowable value. Data allowance for transmitting continuous data in a predetermined period requested for transmission from a device, and determining that a route change is necessary when the data transmission amount of the requested data is less than the data allowance A change in hop count is determined based on a value determination process or a network topology change factor of the first network, and the communication is performed in the order of no change in the hop count, a decrease in the hop count, and an increase in the hop count. In order to change the route that defines the relative difference in network rebuilding time required to change the route and rebuild the first network A priority is determined to be high, and if the determined priority is higher than a pre-specified priority, a route change is necessary, and the determined priority is determined to be the pre-defined priority. If it is equal to or lower than the degree, the route change is not necessary, and the route change possibility is determined by determining whether the communication route can be changed by at least one of the network rebuilding time determination processing for determining whether the communication route can be changed. A judgment function unit;
Based on the result of measuring the communication performance in the communication path, the communication path for constructing the first network is determined, and when it is determined that the path change is necessary by the path change permission determination function unit, A first network communication control unit for changing the communication path and reconstructing the first network;
The communication performance of the communication path of the first network to the management server via the second network constructed with the management server managing the configuration of the first network; and A communication control function unit for transmitting the data;
Have
The management server
A communication system that receives the communication performance of the communication path of the first network and the data from the communication device via the second network.

Images