JP7245664B2 - multi-hop communication system - Google Patents

Description

Embodiments of the present invention relate to multi-hop communication systems.

Conventionally, multi-hop communication is known in which communication from a source node terminal to a destination node terminal is relayed by another node terminal.

In addition, in a multi-hop communication system including a plurality of node terminals that perform such multi-hop communication, a technique is known in which a root node terminal is set as the top and data transmitted from other node terminals is collected to the root node terminal. It is

JP 2007-251529 A JP 2013-175864 A

However, communication between the root node terminal and the node terminal may be cut off due to changes in the radio wave environment or the like. In such cases, it may be difficult to collect data transmitted from node terminals.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the stability of data collection in a multi-hop communication system.

A multi-hop communication system according to an embodiment comprises a first root node terminal, which is an aggregation device arranged at the top of a first tree-structured network, and an aggregation device arranged at the top of a second tree-structured network. A certain second root node terminal, and a plurality of node terminals wirelessly connectable to the first root node terminal or the second root node terminal. Each of the node terminals has a transmitter. At a first timing for transmitting information to the first root node terminal or to another node terminal connected to the first root node terminal, the transmission unit transmits information to the second root node terminal or to the second root node terminal. At a second timing of transmitting information to the second root node terminal or other node terminals connected to the second root node terminal without transmitting information to other node terminals connected thereto, the first root node terminal No information is sent to the terminal or other node terminals connected to the first root node terminal. The network address and assigned frequency of the first root node terminal, the second root node terminal and the plurality of node terminals are the same.

FIG. 1 is a diagram illustrating an example of the overall configuration of a multi-hop communication system according to an embodiment; FIG. 2 is a diagram illustrating an example of a hardware configuration of a node terminal and a root node terminal according to the embodiment; 3 is a block diagram illustrating an example of a functional configuration of a node terminal according to the embodiment; FIG. FIG. 4 is a diagram illustrating an example of changing a connection destination according to the embodiment; FIG. 5 is a diagram illustrating another example of changing a connection destination according to the embodiment; 6 is a block diagram illustrating an example of a functional configuration of a root node terminal according to the embodiment; FIG. FIG. 7 is a flowchart illustrating an example of the flow of parent node change processing executed by the node terminal according to the embodiment;

FIG. 1 is a diagram showing an example of the overall configuration of a multi-hop communication system S according to this embodiment. As shown in FIG. 1, the multi-hop communication system S includes a first root node terminal 20a, a second root node terminal 20j, and node terminals 10b to 10i.

The first root node terminal 20a, the second root node terminal 20j, and the node terminals 10b to 10i are communication devices that are wirelessly connectable to each other. Hereinafter, the first root node terminal 20a and the second root node terminal 20j are simply referred to as the root node terminal 20 when collectively referred to. Also, when an unspecified node terminal 10 is shown, it will simply be described as the node terminal 10 .

In FIG. 1 , the alphabets shown in each of the root node terminal 20 and the plurality of node terminals 10 are examples of IDs (identification information) of each of the root node terminal 20 and the plurality of node terminals 10 . Also, the arrows in FIG. 1 indicate the direction of information transmission.

Further, in the present embodiment, a network configured by the root node terminals 20 and the node terminals 10 included in the multihop communication system S is referred to as a multihop network N.

The node terminal 10 is a node that configures the multihop network N. FIG. In other words, the node terminal 10 is a communication device that performs wireless communication by relaying information through multi-hop communication. In multi-hop communication, another node terminal 10 relays communication from a source node terminal 10 to a destination node terminal 10 (or root node terminal 20). Therefore, the information transmitted by each node terminal 10 is relayed by other node terminals 10 or directly transmitted to the root node terminal 20 .

The root node terminal 20 collects information transmitted from each of the node terminals 10 . The plurality of node terminals 10 and the root node terminal 20 form a tree-structured network with the root node terminal 20 as the root node. A root node may also be referred to as a root node, an aggregator, and so on.

In the multi-hop communication system S of this embodiment, a plurality of node terminals 10 are wirelessly connected in a tree structure to each of the first root node terminal 20a and the second root node terminal 20j.

The first tree T1 shown in FIG. 1 is a tree structure with the first root node terminal 20a as the top. Also, the second tree T2 has a tree structure with the second root node terminal 20j as the top. Hereinafter, the first tree T1 and the second tree T2 are simply referred to as trees T when not distinguished from each other. Each node terminal 10 and the root node terminal 20 in the tree T are connected to each other.

Here, in the present embodiment, "the node terminal 10 is connected to the root node terminal 20" means not only the state in which the node terminal 10 is directly communicating with any root node terminal 20, It includes a state in which information can be transmitted to the root node terminal 20 by being relayed by another node terminal 10 . For example, in the example shown in FIG. 1, the node terminal 10f is connected to the first root node terminal 20a via the node terminals 10e and 10h.

Further, in this embodiment, the side closer to the root node terminal 20 in each tree T is called upstream, and the side away from the root node terminal 20 is called downstream.

Also, the root node terminal 20 and the node terminal 10 included in the multi-hop communication system S of this embodiment have the same network address. Also, the same frequency is assigned to the root node terminal 20 and the node terminal 10 included in the multihop communication system S. FIG. The assigned frequency is a frequency that the root node terminal 20 and the node terminal 10 use for wireless communication. A network address is also called a network ID.

Next, hardware configurations of the node terminal 10 and the root node terminal 20 will be described. In this embodiment, the node terminal 10 and the root node terminal 20 are assumed to have the same hardware configuration.

FIG. 2 is a diagram showing an example of hardware configurations of the node terminal 10 and the root node terminal 20 according to this embodiment. The node terminal 10 and the root node terminal 20 each include a first wireless module 101, a second wireless module 102, a flash memory 103, a processor 104, a ROM (Read Only Memory) 105, and a RAM (Random Access Memory). 106 and a communication interface (I/F) 107 . First wireless module 101 , second wireless module 102 , flash memory 103 , processor 104 , ROM 105 , RAM 106 and communication interface 107 are connected by bus 108 .

The first wireless module 101 wirelessly communicates with another node terminal 10 or the root node terminal 20 . Also, the second wireless module 102 performs wireless communication with the sensor.

The processor 104 is an arithmetic device that controls the node terminal 10 and the root node terminal 20 of this embodiment. The ROM 105 also stores programs and the like executed by the processor 104 . Also, the RAM 106 and the flash memory 103 store information, sensor data, and the like necessary for executing various processes by the processor 104 .

The communication interface 107 is an interface for connecting with an external device such as a PC (Personal Computer), such as a USB (Universal Serial Bus) port.

Note that the hardware configurations of the node terminal 10 and the root node terminal 20 are not limited to the example shown in FIG. For example, the node terminal 10 and the root node terminal 20 may have a configuration in which other hardware components are connected in a star configuration with the processor 104 at the center.

Also, the node terminal 10 and the root node terminal 20 may be provided with other components that implement wireless communication functions instead of the first wireless module 101 and the second wireless module 102 . For example, the node terminal 10 and the root node terminal 20 may be equipped with a NIC (Network Interface Card), a wireless LAN adapter, or the like.

Note that the node terminal 10 and the root node terminal 20 may have different hardware configurations. In this case, the node terminal 10 may not have the communication interface 107 . Also, the root node terminal 20 does not have to include the second wireless module 102 .

Next, the details of the functions of the node terminal 10 of this embodiment will be described. FIG. 3 is a block diagram showing an example of the functional configuration of the node terminal 10 according to this embodiment.

As shown in FIG. 3 , the node terminal 10 includes an acquisition unit 111 , a reception unit 112 , a transmission unit 113 , a connection control unit 114 and a storage unit 150 . Node terminals 10b to 10i included in the multi-hop communication system S are all assumed to have similar functions.

The storage unit 150 stores sensor data acquired from the sensor 30 , sensor data transmitted from other node terminals 10 , connection information, and various information necessary for processing of the node terminals 10 . The storage unit 150 is, for example, the flash memory 103, the RAM 106, or the like.

The connection information is information specifying another node terminal or the root node terminal 20 to which the node terminal 10 sends information. As an example, the connection information is a part of the MAC address of the root node terminal 20 or another node terminal to which information is to be sent, but may be another code or the like.

Also, the connection information registered in the storage unit 150 is connection information for either one of the other node terminals or the root node terminal 20 . For example, in the example shown in FIG. 1, the storage unit 150 of the node terminal 10f stores connection information of the node terminal 10e. Also, the storage unit 150 of the node terminal 10d stores the connection information of the first root node terminal 20a.

Acquisition unit 111 acquires sensor data from sensor 30 via second wireless module 102 . Acquisition unit 111 stores the acquired sensor data in storage unit 150 . Although there is one sensor 30 in FIG. 3, it is assumed that separate sensors 30 are installed around the node terminals 10b to 10i and the root node terminal 20, respectively.

The sensor 30 detects, for example, environmental information of a specific area. The environmental information includes, for example, atmospheric components, air temperature, water temperature, amount of light such as ultraviolet rays, sound volume, etc., but is not limited to these. Sensor data is the detection result of the sensor 30 . In this embodiment, it is assumed that the sensor 30 transmits sensor data to the node terminal 10 by wireless communication. Sensor data is an example of information in this embodiment.

The receiving unit 112 receives sensor data from another node terminal 10 via the first wireless module 101 . The receiving unit 112 stores the received sensor data in the storage unit 150 .

The transmitting unit 113 transmits the sensor data acquired from the sensor 30 by the acquiring unit 111 to the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20j via the communication interface 107, and It transmits sensor data transmitted from other node terminals 10 . Hereinafter, the sensor data acquired from the sensor 30 by the acquisition unit 111 and the sensor data transmitted from other node terminals 10 are simply referred to as sensor data unless otherwise distinguished.

The transmission unit 113 identifies the transmission destination of the sensor data based on the connection information saved in the storage unit 150 . Since the connection information stores the connection information of one of the other node terminals 10 or the root node terminal 20, the transmission unit 113 transmits the sensor data to one of the other node terminals. 10 or root node terminal 20 .

Therefore, at the first timing of transmitting the sensor data to either the first root node terminal 20a or the node terminals 10b to 10f connected to the first root node terminal 20a, the transmission unit 113 of the present embodiment , sensor data is not transmitted to the second root node terminal 20j or to the node terminals 10h and 10i connected to the second root node terminal 20j. Further, at the second timing of transmitting the sensor data to the second root node terminal 20j or the node terminals 10h and 10i connected to the second root node terminal 20j, the transmission unit 113 transmits the sensor data to the first root node terminal 20a. Alternatively, the sensor data is not transmitted to the node terminals 10b to 10f connected to the first root node terminal 20a.

Further, the other node terminal 10 or the root node terminal 20 to which sensor data is transmitted by the transmission unit 113 is called a parent node. For example, in the example shown in FIG. 1, the parent node of the node terminal 10f is the node terminal 10e. Also, the parent node of the node terminal 10i is the second root node terminal 20j.

Returning to FIG. 3, the connection control unit 114 selects any of the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20j as the transmission destination of the sensor data by the transmission unit 113, that is, the parent node. decide whether

The connection control unit 114 determines either the other node terminal 10 or the root node terminal 20 connectable to the own device as the sensor data transmission destination. Further, when the connection control unit 114 determines that the connection with the destination of the sensor data is disconnected, the connection control unit 114 identifies the connectable other node terminal 10 or the root node terminal 20, and selects any one of the other node terminals. 10 or the root node terminal 20 as the destination of the sensor data.

Specifically, the connection control unit 114 identifies the connectable other node terminal 10 or the root node terminal 20 by detecting a beacon signal transmitted from the other node terminal 10 or the root node terminal 20 . The beacon signal includes the connection information of the other node terminal 10 or the root node terminal 20 that is the source of the beacon signal, and the relay number or level of the connection information of the other node terminal 10 or the root node terminal 20. shall be A beacon signal is an example of a signal in this embodiment.

When there are a plurality of connectable other node terminals 10 or root node terminals 20, the connection control unit 114 selects, from among the connectable other node terminals 10 or root node terminals 20, the connection to the root node terminal 20. The other node terminal 10 or the root node terminal 20 with the smallest number of relays is determined as the sensor data transmission destination.

Here, the number of relays is the number of node terminals 10 through which other node terminals 10 go through to connect to the first root node terminal 20a or the second root node terminal 20j. The number of relays is also called the number of hops.

Further, in the multi-hop network N, each node terminal 10 is divided into levels so that the level of the node terminal 10 becomes lower as it connects to the root node terminal 20 with a smaller number of relays. Therefore, in other words, the connection control unit 114 determines the node terminal 10 or the root node terminal 20 with the lowest level among other connectable node terminals 10 or the root node terminal 20 as the sensor data transmission destination. do.

In addition, when the number of relays or the level of a plurality of connectable node terminals 10 or the root node terminal 20 is the same, the connection control unit 114 selects the other node terminal 10 with the strongest radio wave intensity of the transmitted beacon signal. Alternatively, the root node terminal 20 is determined as the transmission destination of the sensor data. The connection control unit 114 detects the radio field strength of the beacon signal based on, for example, LQI (Link Quality Indicator) or RSSI (Received Signal Strength Indication).

For example, the number of relays for the root node terminal 20 itself is “0” for connecting to the root node terminal 20 , so the number of relays for the root node terminal 20 is smaller than any of the node terminals 10 . Similarly, the level of the root node terminal 20 is lower than any of the node terminals 10 . Therefore, when the connection control unit 114 detects a beacon signal transmitted from either the first root node terminal 20a or the second root node terminal 20j, the connection control unit 114 detects the beacon signal transmitted from the first root node terminal 20a or the second root node terminal 20j. The root node terminal 20a or the second root node terminal 20j is determined as the sensor data transmission destination. Further, when the connection control unit 114 detects beacon signals transmitted from both the first root node terminal 20a and the second root node terminal 20j, the connection control unit 114 Among the terminals 20j, the root node terminal 20 having the strong radio wave intensity of the transmitted beacon signal is determined as the transmission destination of the sensor data.

In addition, the connection control unit 114, when the radio wave intensity of the beacon signal transmitted from the other node terminal 10 or the root node terminal 20, which is the transmission destination of the sensor data, is equal to or less than a predetermined intensity, or when the sensor data transmission destination When the beacon signal of a certain other node terminal 10 or the root node terminal 20 is not detected, it is determined that the connection with the other node terminal 10 or the root node terminal 20 has been disconnected. Although the predetermined intensity is not particularly limited, it is assumed to be a radio wave intensity capable of transmitting sensor data.

The case where the radio field strength of the beacon signal transmitted from the other node terminal 10 or the root node terminal 20, which is the destination of the sensor data, is equal to or less than a predetermined strength is, for example, the case where the device itself and the other node terminal 10 or the root node For example, when a building is constructed between the terminal 20 and the radio wave environment deteriorates, or when an interfering radio wave occurs.

Further, when the connection control unit 114 does not detect the beacon signal of the other node terminal 10 or the root node terminal 20 to which the sensor data is to be sent, for example, the other node terminal 10 or the root node terminal 20 to which the sensor data is to be sent. This is the case, for example, when some failure occurs in the node terminal 20 and transmission of the beacon signal is stopped.

Here, the object for which the connection control unit 114 detects the beacon signal is the node terminal 10 or the root node terminal 20 having the same network address as its own device and the same allocated frequency as its own device. In other words, the connection control unit 114 can detect a beacon signal transmitted from the node terminal 10 or the root node terminal 20 belonging not only to the tree T to which the device belongs but also to another tree T included in the multihop network N. can.

FIG. 4 is a diagram showing an example of changing the connection destination according to the present embodiment. The parent node of the node terminal 10d shown in FIG. 4 was the first root node terminal 20a as in FIG. At this point, the node terminal 10d belonged to the first tree T1. However, it is assumed that due to deterioration of the radio wave environment, the radio wave intensity of the beacon signal transmitted from the first root node terminal 20a has become equal to or less than a predetermined intensity. In this case, the connection control unit 114 of the node terminal 10d identifies the connectable other node terminal 10 or the root node terminal 20 by detecting the beacon signal transmitted from the other node terminal 10 or the root node terminal 20. do.

In the example shown in FIG. 4, the connection control unit 114 of the node terminal 10d detects the beacon signal transmitted from the node terminal 10h belonging to the second tree T2, and detects the beacon signal transmitted from the other node terminals 10 or the root node terminal 20. beacon signal is not detected. In this case, the connection control unit 114 of the node terminal 10d determines the node terminal 10h as a new parent node. Therefore, as shown in FIG. 4, the node terminal 10d moves from the first tree T1 to the second tree T2. Due to such movement, the sensor data of the node terminal 10d are collected by the second root node terminal 20j located at the top of the second tree T2.

Since the multi-hop communication system S of this embodiment includes two root node terminals 20, as shown in FIG. However, the other root node terminal 20 continues collecting the sensor data of the node terminal 10 concerned.

FIG. 5 is a diagram showing another example of changing the connection destination according to this embodiment. The parent node of the node terminal 10b and the node terminal 10c shown in FIG. 5 is the first root node terminal 20a as in FIG. However, some kind of failure occurred in the first root node terminal 20a, and transmission and reception of information and signals stopped. In this case, the first tree T1 whose top is the first root node terminal 20a disappears.

In the example shown in FIG. 7, for example, the connection control unit 114 of the node terminal 10c detects the beacon signal transmitted from the node terminal 10d and determines the node terminal 10d as the new parent node. It is also assumed that the connection control unit 114 of the node terminal 10b detects beacon signals from both the node terminal 10c and the node terminal 10g. In this case, the node terminal 10g has a smaller number of relays for connecting to the second root node terminal 20j than the node terminal 10c. Therefore, the connection control unit 114 of the node terminal 10b determines the node terminal 10g as a new parent node.

The connection control unit 114 stores the connection information of the other node terminal 10 or the root node terminal 20 determined as the parent node to which the sensor data is to be sent, among the connectable other node terminals 10 or the root node terminal 20. Store in unit 150 .

Also, the connection control unit 114 periodically transmits a beacon signal including the connection information of its own device and the relay number or level of its own device to the other node terminal 10 or the root node terminal 20 .

Next, the details of the functions of the root node terminal 20 of this embodiment will be described. FIG. 6 is a block diagram showing an example of the functional configuration of the root node terminal 20 according to this embodiment.

As shown in FIG. 6 , the root node terminal 20 includes an acquisition unit 211 , a reception unit 212 , a communication unit 213 and a storage unit 250 . All root node terminals 20 included in the multi-hop communication system S (that is, the first root node terminal 20a and the second root node terminal 20j) are assumed to have similar functions.

Acquisition unit 211 acquires sensor data from sensor 30 via second wireless module 102 . Acquisition unit 211 stores the acquired sensor data in storage unit 250 .

The receiving unit 212 receives sensor data from the node terminal 10 directly connected to its own device. More specifically, the receiving unit 212 of the first root node terminal 20a receives the sensor data acquired by the node terminals 10b to 10d from each of the node terminals 10b to 10d and the nodes under each of the node terminals 10b to 10d. It receives the sensor data acquired by the terminals 10e to 10g. The receiving unit 212 stores the received sensor data in the storage unit 250 .

The storage unit 250 stores the sensor data received by the reception unit 212 and the sensor data acquired by the acquisition unit 211 . The storage unit 250 is the flash memory 103 or the RAM 106, for example.

The communication unit 213 transmits sensor data saved in the storage unit 250 to the PC 40 . The communication units 213 of all the root node terminals 20 included in the multi-hop communication system S transmit the sensor data to one PC 40, so that the sensor data collection results can be integrated. Moreover, the destination of the sensor data collected by the root node terminal 20 is not limited to the PC 40 . For example, the communication unit 213 may transmit sensor data to the cloud environment by wireless communication.

Next, the flow of changing the parent node executed in the multi-hop communication system S configured as above will be described.

FIG. 7 is a flowchart showing an example of the flow of changing the parent node executed by the node terminal 10 according to this embodiment. The processing of this flowchart may be executed periodically, for example, at the timing when the acquiring unit 111 of the node terminal 10 acquires sensor data, or at the timing when the receiving unit 112 of the node terminal 10 receives sensor data. It may be executed by

First, the connection control unit 114 determines whether or not it is currently connected to the parent node (S1).

The connection control unit 114 determines whether the radio wave intensity of the beacon signal transmitted from the node terminal 10 or the root node terminal 20 specified by the connection information stored in the storage unit 150 is equal to or less than a predetermined intensity, or by the connection information. If no beacon signal transmitted from the specified node terminal 10 or root node terminal 20 is detected, it is determined that the connection with the parent node has been disconnected (S1 "No"). In this case, the connection control unit 114 determines whether or not a beacon signal transmitted from any other node terminal 10 or the root node terminal 20 other than the parent node is detected (S2).

The connection control unit 114 selects the node terminal 10 or the root node terminal 20 with the lowest rank (that is, the node terminal 10 or the root node terminal 20 with the smallest number of relays) among the detected beacon signal transmission sources as a new parent node. (S3). The connection control unit 114 saves the connection information of the other node terminal 10 or the root node terminal 20 determined as the new parent node in the storage unit 150 .

The transmitting unit 113 then identifies a new parent node based on the connection information saved in the storage unit 150 . The transmission unit 113 transmits the sensor data to the new parent node (S4). If the new parent node is the node terminal 10 belonging to the second tree T2 or the second root node terminal 20j, the transmission timing is an example of the second transmission timing. Since the transmission unit 113 transmits the sensor data to one destination, at the timing of the process of S4, the transmission unit 113 transmits the sensor data to the node terminal 10 or the first root node terminal 20a belonging to the first tree T1. Send no data.

Also, when the connection control unit 114 determines that it is currently connected to the parent node (S1 “Yes”), the connection information saved in the storage unit 150 is not changed.

In this case, the transmission unit 113 identifies the parent node based on the connection information stored in the storage unit 150, and transmits the sensor data to the parent node (S5). If the existing parent node is the node terminal 10 or the first root node terminal 20a belonging to the first tree T1, the transmission timing is an example of the first transmission timing. Since the transmission unit 113 transmits the sensor data to one destination, the transmission unit 113 sends the sensor data to the node terminal 10 belonging to the second tree T2 or the second root node terminal 20j at the timing of the process of S5. Send no data.

Here, the processing of this flowchart ends. Note that the parent node change process and the sensor data transmission process may be executed at different timings as separate processes.

In the conventional technology, when information is collected from each node terminal using a tree-structured multi-hop network, communication between the root node terminal and the node terminal is cut off due to changes in the radio wave environment, etc., and the node terminal sends Collecting data was sometimes difficult. In addition, in order to avoid such a situation, if one node terminal is configured to be always connected to a plurality of root node terminals, the same information will be redundantly collected by the plurality of node terminals. Accumulation of unnecessary data could occur.

On the other hand, the multi-hop communication system S of this embodiment includes the first root node terminal 20a, the second root node terminal 20j, and the first root node terminal 20a or the second root node terminal 20j. and a plurality of node terminals 10 that are wirelessly connectable. Then, at the first timing when the node terminal 10 transmits sensor data to the first root node terminal 20a or another node terminal 10 connected to the first root node terminal 20a, the second root node terminal 20j Alternatively, sensor data is not transmitted to other node terminals 10 connected to the second root node terminal 20j. Further, at the second timing when the node terminal 10 transmits the sensor data to the second root node terminal 20j or another node terminal 10 connected to the second root node terminal 20j, the first root node terminal 20a Alternatively, sensor data is not transmitted to other node terminals 10 connected to the first root node terminal 20a. Therefore, according to the multi-hop communication system S of the present embodiment, it is possible to avoid redundant collection of the same sensor data by a plurality of root node terminals 20 and improve the stability of data collection. .

Also, in the multi-hop communication system S of the present embodiment, the network address and allocated frequency of the first root node terminal 20a, the second root node terminal 20j, and the plurality of node terminals 10 are the same. Therefore, each node terminal 10 can be connected to other node terminals or the root node terminal 20 belonging to the tree T different from its own device. Therefore, according to the multi-hop communication system S of the present embodiment, even if the connection with one root node terminal 20 is disconnected, the other root node terminal 20 collects the sensor data of the node terminal 10. can be continued.

Further, according to the multi-hop communication system S of the present embodiment, by unifying the network addresses and frequencies, it is possible to make the settings of each node terminal 10 and the root node terminal 20 uniform. It is possible to reduce the burden on the operator when installing the root node terminal 20, or the occurrence of problems due to incorrect settings or the like.

Further, when the node terminal 10 of the present embodiment determines that the connection with the destination of the sensor data is disconnected, the node terminal 10 that can be connected to the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20a The node terminal 20j is identified, and any one other node terminal, the first root node terminal 20a, or the second root node terminal 20j is determined as a new transmission destination of the sensor data. Specifically, the node terminal 10 of the present embodiment can be connected by detecting a beacon signal transmitted from another node terminal 10, the first root node terminal 20a, or the second root node terminal 20b. other node terminal 10 or the root node terminal 20 is specified. Therefore, according to the multi-hop communication system S of this embodiment, it is possible to automatically detect a new parent node without previously registering backup connection destination information.

Further, when the node terminal 10 of the present embodiment detects a beacon signal transmitted from another node terminal 10, the first root node terminal 20a, or the second root node terminal 20b, the detected beacon signal Among the senders, the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20b, which has the smallest number of relays, is determined as the sensor data transmission destination. Therefore, according to the multi-hop communication system S of this embodiment, the shortest route for collecting sensor data to the root node terminal 20 can be selected.

Further, when the number of relays is the same, the node terminal 10 of the present embodiment selects the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20j having the strongest radio wave intensity of the beacon signal. Decide as the destination of the sensor data. Therefore, according to the multi-hop communication system S of this embodiment, it is possible to further improve the stability of sensor data collection.

Further, the node terminal 10 of the present embodiment has a beacon signal transmitted from another node terminal 10, the first root node terminal 20a, or the second root node terminal 20j, which is the sensor data transmission destination, and the radio wave intensity of the beacon signal is When the intensity is less than a predetermined intensity, or when the beacon signal of the other node terminal 10, the first root node terminal 20a, or the second root node terminal 20j, which is the destination of the sensor data, is not detected, the other node It is determined that the connection with the terminal 10, the first root node terminal 20a, or the second root node terminal 20j is disconnected. Therefore, according to the multi-hop communication system S of the present embodiment, it is possible to automatically determine the connection state and quickly search for a new connection destination.

Although the multi-hop communication system S has two root node terminals 20 in this embodiment, the multi-hop communication system S may have three or more root node terminals 20 . Also, the configuration of the multi-hop communication system S shown in FIGS. 1, 4, and 5 is an example, and the number of node terminals 10 and root node terminals 20 and the connection relationship between the node terminals 10 and root node terminals 20 are , but not limited to the above examples.

Further, in the present embodiment, the sensor 30 transmits sensor data to the node terminal 10 and the root node terminal 20 by wireless communication. Also good. For example, a configuration in which the sensor 30 is incorporated in the same unit as the node terminal 10 or the root node terminal 20 may be employed. In this case, sensor 30 is assumed to be connected to node terminal 10 or root node terminal 20 via communication interface 107 . Sensor 30 may also be capable of providing sensor data to processor 104 of node terminal 10 or root node terminal 20 by other means. Moreover, when adopting this configuration, the node terminal 10 and the root node terminal 20 may not have the second wireless module 102 . The sensor 30 may be provided in the same housing as the node terminal 10 or the root node terminal 20, or may be provided as a separate housing.

Further, in the present embodiment, the multi-hop communication system S collects sensor data acquired by each node terminal 10, but the information collected by the multi-hop communication system S is limited to sensor data. isn't it.

Note that the programs executed by the node terminal 10 and the root node terminal 20 of the present embodiment are files in an installable format or an executable format and can be stored on a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk), USB (Universal Serial Bus) memory or other computer-readable recording medium, or may be configured to be provided or distributed via a network such as the Internet. Also good. In addition, various programs may be configured to be pre-installed in a ROM or the like and provided.

A program executed by the node terminal 10 of the present embodiment has a module configuration including each functional unit (acquisition unit, reception unit, transmission unit, connection control unit) described above.

Further, the program executed by the root node terminal 20 of the present embodiment has a module configuration including each functional unit (acquisition unit, reception unit, communication unit) described above.

Further, the program for executing the above processing in the present embodiment has a module configuration including each of the above functional units. is read and executed to load each functional unit described above onto the RAM (main memory), and each functional unit described above is generated on the RAM (main memory). Part or all of the functional units described above can also be realized using dedicated hardware such as ASIC (Application Specific Integrated Circuit) and FPGA (Field-Programmable Gate Array).

In addition, in the present embodiment, the acquisition unit 111, the reception unit 112, the transmission unit 113, the connection control unit 114 of the node terminal 10, and the acquisition unit 211, the reception unit 212, and the communication unit 213 of the root node terminal 20 are controlled by the processor 104. Although described as an example of the functions to be implemented, each functional unit may be implemented by a hardware circuit or the like. For example, the acquisition unit 111 of the node terminal 10 and the acquisition unit 211 of the root node terminal 20 may be implemented by the second wireless module 102 or the communication interface 107 . Also, the receiving unit 112 and transmitting unit 113 of the node terminal 10 and the receiving unit 212 of the root node terminal 20 may be realized by the first wireless module or communication interface. Also, the communication unit 213 of the root node terminal 20 may be realized by a communication interface. Also, the communication unit 213 of the root node terminal 20 may be implemented by a hardware component that implements a wireless communication function.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

10, 10b to 10i node terminal 20a first root node terminal 20j second root node terminal 30 sensor 111 acquisition unit 112 reception unit 113 transmission unit 114 connection control unit 150 storage unit 211 acquisition unit 212 reception unit 213 communication unit 250 storage part N multihop network S multihop communication system T1 first tree T2 second tree

Claims (6)

a first root node terminal which is an aggregating device arranged at the vertex of the first tree-structured network ; a second root node terminal which is an aggregating device arranged at the vertex of the second tree-structured network; a plurality of node terminals wirelessly connectable to the first root node terminal or the second root node terminal;
each of the node terminals,
At a first timing for transmitting information to the first root node terminal or another node terminal connected to the first root node terminal, the second root node terminal or the second root node terminal and In a second timing of transmitting the information to the second root node terminal or another node terminal connected to the second root node terminal without transmitting the information to other node terminals to be connected, a transmission unit that does not transmit the information to the first root node terminal or to another node terminal connected to the first root node terminal;
with
network addresses and assigned frequencies of the first root node terminal, the second root node terminal, and the plurality of node terminals are the same;
multi-hop communication system. each of the node terminals,
a connection control unit that determines, as a transmission destination of the information, any of another node terminal connectable to the node terminal, the first root node terminal, or the second root node terminal,
The connection control unit identifies another connectable node terminal, the first root node terminal, or the second root node terminal when determining that the connection with the transmission destination of the information is disconnected. , determining any one other node terminal, the first root node terminal, or the second root node terminal as a new destination of the information;
A multi-hop communication system according to claim 1. The connection control unit detects a signal transmitted from another node terminal, the first root node terminal, or the second root node terminal to detect a signal transmitted from the other node terminal, the first root node terminal, or the other node terminal to which the connection is possible. identifying the root node terminal, or the second root node terminal;
A multi-hop communication system according to claim 2. The connection control unit, when detecting the signal transmitted from a plurality of other node terminals, the first root node terminal, or the second root node terminal, , another node terminal having the smallest number of relays for connecting to the first root node terminal or the second root node terminal, the first root node terminal, or the second root node terminal is selected from the information to be determined as the destination of the
A multi-hop communication system according to claim 3. When the number of relays of a plurality of other node terminals, the first root node terminal, or the second root node terminal is the same, the connection control unit controls the other node having the strongest radio wave intensity of the signal. determining the terminal, the first root node terminal, or the second root node terminal as a transmission destination of the information;
A multi-hop communication system according to claim 4. When the radio wave intensity of the signal transmitted from another node terminal, the first root node terminal, or the second root node terminal, which is the transmission destination of the information, is equal to or less than a predetermined intensity, the connection control unit , or when the signal of the other node terminal, the first root node terminal, or the second root node terminal, which is the destination of the information, is not detected, the other node terminal, the first root node terminal, Determining that the connection with the root node terminal or the second root node terminal is disconnected;
The multi-hop communication system according to claim 4 or 5.

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