Communication system and communication method

Abstract

This communication system (100) comprises a plurality of containers (2) that have conductivity and are stacked, and a plurality of electric field communication terminals (5) attached to the plurality of containers (2) so as to be electrically coupled to one of the containers (2), wherein: the plurality of containers (2) include a container (2) in which a sensing terminal (4) for acquiring sensing data is accommodated; the plurality of electric field communication terminals (5) include a first electric field communication terminal (5) mounted inside the container (2) in which the sensing terminal (4) is accommodated, and a second electric field communication terminal (5) attached to the outside of at least one container (2) among the plurality of containers (2); and the first electric field communication terminal (5) transmits the sensing data from the sensing terminal (4) to the second electric field communication terminal (5) via the plurality of containers (2).

Description

[Technical Field]

[0001] The present disclosure relates to a communication system and a communication method. [Background technology]

[0002] For example, Patent Document 1 discloses a communication device in which an external conductor is used as an antenna by radiating electromagnetic waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-34617 Summary of the Invention [Problem to be solved by the invention]

[0004] When attempting to transmit sensing data of cargo or the like stored in a container from inside the container to the outside of the container using electromagnetic waves, the electromagnetic waves may be blocked by the container, making it impossible to retrieve the sensing data from the container.

[0005] One aspect of the present disclosure allows sensing data to be extracted outside the container. [Means for solving the problem]

[0006] A communication system according to one aspect of the present disclosure comprises a plurality of stacked containers that are conductive, and a plurality of electric field communication terminals attached to the containers so as to be electric field coupled with any of the plurality of containers, wherein the plurality of containers includes a container that houses a sensing terminal that acquires sensing data, and the plurality of electric field communication terminals include a first electric field communication terminal attached inside the container that houses the sensing terminal, and a second electric field communication terminal attached outside at least one of the plurality of containers, and the first electric field communication terminal transmits sensing data from the sensing terminal to the second electric field communication terminal via the plurality of containers.

[0007] A communication method according to one aspect of the present disclosure includes a first electric field communication terminal attached to the inside of a container that houses a sensing terminal that acquires sensing data among a plurality of stacked conductive containers so as to be electric field coupled with the container, transmitting the sensing data from the sensing terminal via the plurality of containers to a second electric field communication terminal attached to the outside of at least one of the plurality of containers so as to be electric field coupled with the container. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a communication system according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a schematic configuration of a sensing terminal. [Figure 3] FIG. 1 is a diagram illustrating an example of a schematic configuration of an electric field communication terminal. [Figure 4] FIG. 1 is a diagram illustrating an example of a schematic configuration of an electric field communication transceiver. [Figure 5] FIG. 2 is a diagram illustrating an example of a schematic configuration of a gateway device. [Figure 6] FIG. 10 is a diagram illustrating an example of node types and communication. [Figure 7] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. [Figure 8] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. [Figure 9] FIG. 1 is a diagram illustrating an example of application of a communication system to a container ship. [Figure 10] FIG. 10 is a diagram illustrating an example of a schematic configuration of a communication system according to a second embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of node types and communication. [Figure 12] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. [Figure 13] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. [Figure 14] FIG. 10 is a diagram illustrating an example of terminal information. [Figure 15] 1 is a flowchart illustrating an example use case of a communication system. [Figure 16] 10 is a flowchart illustrating an example of processing executed in the electric field communication terminal. [Figure 17] 10 is a flowchart illustrating an example of processing executed in the electric field communication terminal. [Figure 18] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. [Figure 19] FIG. 1 is a diagram illustrating an example of a node configuration of a communication system. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same elements are designated by the same reference numerals, and redundant description will be omitted.

[0010] The present disclosure will be described in the following order: 1. First embodiment 2. Example of application to container ships 3. Second embodiment 4. Example Use Cases 5. Example of processing by electric field communication terminal 6. Variations 7.Example of effects

[0011] 1. First embodiment FIG. 1 is a diagram illustrating an example of a schematic configuration of a communication system according to the first embodiment. The communication system 100 includes one or more container stacks 1, multiple terminals 5, and a gateway device 6. As will be described later, the terminal 5 may have the functionality of the gateway device 6, in which case the communication system 100 does not need to include the gateway device 6. The communication system 100 is capable of communicating with an external network NW. Sensing data of the luggage 3, which will be described later, is transmitted to the external network NW.

[0012] The container stack 1 includes a plurality of stacked containers 2. All of the containers 2 are electrically conductive. An example of such a container 2 is a steel container. The containers 2 are electrically connected (coupled) when adjacent containers 2 come into contact with each other in the height direction of the container stack 1 (the stacking direction of the containers 2). Note that Figure 1 shows two container stacks 1 arranged with a gap between them. Unless otherwise specified, the following description will refer to one container stack 1 shown on the left side of Figure 1.

[0013] Of the multiple containers 2, at least one container 2 contains luggage 3 and a sensing terminal 4. The same container 2 may contain multiple luggage 3 and multiple sensing terminals 4. Some containers 2 may not contain luggage 3 and sensing terminals 4. In the example shown in FIG. 1 , the second container 2 from the top does not contain luggage 3 and a sensing terminal 4.

[0014] The cargo 3 may be any cargo that can be transported, stored, etc. by the container 2. An example of a cargo is a carton or the like.

[0015] The sensing terminal 4 senses (detects) the state of the luggage 3 and acquires the sensing data. The sensing terminal 4 will be described with reference to FIG.

[0016] 2 is a diagram illustrating an example of a schematic configuration of a sensing terminal 4. In this example, the sensing terminal 4 includes a sensor 41, an M2M communication device 42, a CPU 43, and a storage device 44.

[0017] The sensor 41 senses the state of the luggage 3 and outputs sensing data indicating the sensing result. Various information indicating the state of the luggage 3 may be included in the sensing data.

[0018] The M2M communication device 42 performs M2M (Machine to Machine) communication. Examples of M2M communication include WiFi (registered trademark), BL (Bluetooth) (registered trademark), BLE (Bluetooth Low Energy) (registered trademark), and Zigbee (registered trademark). An example of the communication partner is a terminal 5 installed in the same container 2. Note that although wireless communication is preferable for M2M communication, wired communication may also be used.

[0019] The CPU 43 is a central processing unit that performs overall control of the sensing terminal 4. For example, the CPU 43 controls the sensor 41 to acquire sensing data of the package 3. The CPU 43 controls the M2M communication device 42 to transmit the sensing data to the terminal 5.

[0020] The storage device 44 stores information necessary for processing executed in the sensing terminal 4. The stored information may also include a program for causing the CPU 43 to execute desired processing.

[0021] Returning to Fig. 1, the multiple terminals 5 extract sensing data from the container 2 and transmit it to the external network NW. Each of the multiple terminals 5 is an electric field communication terminal attached to one of the multiple containers 2 so as to be electrically coupled with that container 2. The terminals 5 will be described with reference to Fig. 3 as well.

[0022] 3 is a diagram illustrating an example of a schematic configuration of an electric field communication terminal 5. In this example, the terminal 5 includes an M2M communication device 51, an electric field communication transceiver 52, a LAN communication device 53, an external NW communication device 54, a CPU 55, and a storage device 56.

[0023] The M2M communication device 51 performs M2M communication. An example of the communication partner is the sensing terminal 4. The terminal 5 and the sensing terminal 4 detect each other, for example, by pairing. This makes it possible to identify the sensing terminal 4 used in the communication system 100 and establish a connection between the sensing terminal 4 and the terminal 5. Various known pairing methods may be used for the pairing.

[0024] The electric field communication transceiver 52 performs electric field communication by utilizing electric field coupling with the container 2. Any communication method using an electric signal may be used for electric field communication. An example of the communication partner is another terminal 5. The configuration of the electric field communication transceiver 52, particularly the part related to electric field communication, will be described with reference to FIG. 4.

[0025] 4 is a diagram showing an example of a schematic configuration of an electric field communication transceiver, in which a signal processing unit 521 and an antenna 522 are shown as components related to electric field communication.

[0026] The signal processing unit 521 processes signals transmitted and received by the antenna 522. For example, the signal processing unit 521 generates a signal and supplies it to the antenna 522. The signal processing unit 521 also processes the signal from the antenna 522.

[0027] The antenna 522 is provided to face the container 2. For example, the antenna 522 is provided at a distance from the container 2 so as to face a part of the steel plate of the container 2. The antenna 522 may have a plate shape extending to face the container 2. A dielectric D is provided or present between the antenna 522 and the container 2. The dielectric D may be plastic or the like, or air or the like. When the dielectric D is air, the dielectric D may be an air gap. As will be described next, the antenna 522 generates dielectric polarization in the dielectric D.

[0028] The arrows in (A) of FIG. 4 schematically indicate signal transmission. The signal generated by the signal processing unit 521 is supplied to the antenna 522. An electric field is generated in the dielectric D, causing polarization (dielectric polarization). Charges of opposite polarity to that of the antenna 522 are generated in the container 2. The respective charges are schematically illustrated as + / - and - / +. Since the polarization changes according to the signal, the charge generated in the container 2 also changes according to the signal. Due to such electric field coupling, the signal from the antenna 522 is transmitted to the container 2, and a signal (electric field signal) is generated in the container 2.

[0029] The arrows in (B) of Figure 4 schematically show the reception of a signal. In the reverse flow to the above, the signal from the container 2 is transmitted to the antenna 522 and received by the antenna 522. The signal processing unit 521 processes the signal from the antenna 522.

[0030] By using electric field communication using the electric field coupling as described above, a communication network can be established between multiple terminals 5 via the container stack 1. Such a communication network is called an "electric field communication network." In one embodiment, multiple terminals 5 establish an electric field communication network by each terminal 5 establishing a connection with another terminal 5 via the container stack 1. For example, multiple terminals 5 establish an electric field communication network by detecting each other through pairing. In electric field communication between pairs, low-intensity signals may be used that suppress the flow of signals to containers 2 outside the path between the pairs.

[0031] Returning to FIG. 3, the LAN communication device 53 performs LAN (Local Area Network) communication. An example of the communication partner is the gateway device 6. The LAN communication may be wireless communication or wired communication. Examples of LAN communication include Wi-Fi (registered trademark) communication, Ethernet (registered trademark) communication, and LTE (Long Term Evolution) communication.

[0032] The external NW communication device 54 communicates with the external network NW. Communication with the external network NW is sometimes referred to as "external network communication." Examples of external network communication include LTE (Long Term Evolution) communication, LPWAN (Low Power Wide Area-network) communication, satellite communication, etc. The external NW communication device 54 provides a communication interface with the external network NW. Data can be transmitted to the external network NW through a gateway.

[0033] The CPU 55 performs overall control of the terminal 5. For example, the CPU 55 controls the M2M communication device 51 to receive sensing data from the sensing terminal 4. The CPU 55 controls the electric field communication transceiver 52 to transmit and receive various information to and from other terminals 5. The CPU 55 controls the LAN communication device 53 to transmit and receive various information to and from the gateway device 6. The CPU 55 controls the external NW communication device 54 to transmit sensing data to the external network NW.

[0034] The storage device 56 stores information necessary for processing executed in the terminal 5. The stored information may also include a program for causing the CPU 55 to execute desired processing.

[0035] Returning to Fig. 1, the multiple terminals 5 include a terminal 5 (first electric field communication terminal) attached to the inside of the container 2 that houses the luggage 3 and the sensing terminal 4. In the example shown in Fig. 1, a terminal 5 is attached to the inside of each of the uppermost container 2 and the lowermost container 2. No terminal 5 is attached to the inside of the second-highest container 2.

[0036] The multiple terminals 5 include a terminal 5 (second electric field communication terminal) attached to the outside of at least one container 2 among the multiple containers 2. In the example shown in Fig. 1, one terminal 5 is attached to the outside of the top of the uppermost container 2. However, the position of the terminal 5 attached to the outside of the container stack 1 is not limited to the example shown in Fig. 1. For example, the terminal 5 may be attached to the outside of a side of the container 2.

[0037] Hereinafter, the terminal 5 attached to the inside of the container 2 may be simply referred to as the "terminal 5 inside the container 2." The terminal 5 attached to the outside of the container 2 may be simply referred to as the "terminal 5 outside the container 2."

[0038] The gateway device 6 communicates with the external network NW. The gateway device 6 will be described with reference to FIG.

[0039] 5 is a diagram illustrating an example of a schematic configuration of a gateway device. In this example, the gateway device 6 includes a LAN communication device 61, an external NW communication device 62, a CPU 63, and a storage device 64. The LAN communication device 61 and the external NW communication device 62 are similar to the LAN communication device 53 and the external NW communication device 54 previously described with reference to FIG. 3, and therefore description thereof will not be repeated.

[0040] The CPU 63 performs overall control of the gateway device 6. For example, the CPU 63 controls the LAN communication device 61 to transmit and receive various information to and from the terminal 5. The CPU 63 controls the external NW communication device 62 to transmit and receive various information to and from the external network NW.

[0041] The storage device 64 stores information necessary for processing executed in the gateway device 6. The stored information may also include a program for causing the CPU 63 to execute desired processing.

[0042] Returning to FIG. 1 , in the communication system 100, a sensing terminal 4 inside a container 2 acquires sensing data of a cargo 3 in the container 2. The sensing terminal 4 transmits the sensing data to a terminal 5 inside the same container 2 via M2M communication. The terminal 5 inside the container 2 receives the sensing data from the sensing terminal 4 and transmits the sensing data to a terminal 5 outside the container stack 1 via electric field communication. The terminal 5 outside the container stack 1 receives the sensing data from the terminal 5 inside the container 2. In this way, the sensing data of the cargo 3 housed in the container 2 can be retrieved outside the container 2. By using electric field communication, communication between the inside and outside of the container 2 can be made wireless. For example, there is no need to connect the inside and outside of the conductive container 2 with a wire (by processing the wall, etc.). This simplifies the device configuration and also makes it easier to install the terminal 5 (mount it on the container 2, etc.).

[0043] Furthermore, the terminal 5 outside the container stack 1 transmits the sensing data directly or indirectly to the external network NW. For example, the terminal 5 transmits the sensing data (directly) to the external network NW using the external NW communication device 54 included in the terminal 5. Alternatively, the terminal 5 transmits the sensing data to the gateway device 6 using the LAN communication device 53 included in the terminal 5. The gateway device 6 transmits the sensing data from the terminal 5 to the external network NW. As a result, the sensing data from the terminal 5 is transmitted (indirectly) to the external network NW via the gateway device 6. In this case, the terminal 5 can also be said to be a network bridge terminal that relays communication to the external network NW. Transmitting the sensing data to the external network NW makes it possible to collect the sensing data via the external network NW. By using electric field communication, the sensing data can be transmitted more reliably to the terminal 5 outside the container 2 that is capable of external network communication, compared to, for example, using wireless communication outside the container 2. This is because wireless communication (electromagnetic waves) outside the container 2 has the problem of being blocked by adjacent container stacks 1, etc., but such a problem does not exist in electric field communication using the container stack 1. According to the communication system 100, it is possible not only to extract the sensing data of the cargo 3 outside the container 2, but also to reliably transmit the sensing data to a terminal 5 installed in a location connectable to an external network NW.

[0044] Hereinafter, unless otherwise specified, directly or indirectly transmitting sensor data to the external network NW may also be simply referred to as "transmitting to the external network NW."

[0045] The sensing terminal 4, terminal 5, and gateway device 6 described above can also be explained in association with the nodes that make up the communication system 100. These nodes are also shown in FIG. 1, which was previously explained. Specifically, the sensing terminal 4 functions as node s. The terminal 5 functions as node vg, node v1, or node t1. The gateway device 6 functions as node g. The node configuration of the communication system 100 will be explained with reference to FIGS. 6 to 8.

[0046] 6 is a diagram showing examples of node types and communication. Node g corresponds to the function of gateway device 6. The communication of node g includes LAN communication and external network communication, which are provided by LAN communication device 61 and external NW communication device 62 of gateway device 6 (FIG. 5).

[0047] The nodes vg, v1, and t1 correspond to the functions of the terminal 5. The communications between the nodes vg, v1, and t1 include at least electric field communications. The electric field communications are performed by the electric field communications transceiver 52 of the terminal 5.

[0048] Node vg and node v1 correspond to the function of a terminal 5 outside the container stack 1. Node vg corresponds to the function of the terminal 5 that transmits sensing data directly to the external network NW. The communication of node vg includes LAN communication and external network communication in addition to electric field communication. The LAN communication and external network communication are performed by the LAN communication device 53 and the external NW communication device 54 (FIG. 3) of the terminal 5. Note that, since the communication of node vg includes LAN communication, for example, in the communication system 100A (FIG. 10) described later, it is possible to relay sensing data to another node vg when the node vg moves together with the container 2 to a location where communication with the external network NW is difficult. Node v1 corresponds to the function of the terminal 5 that transmits sensing data indirectly (via the gateway device 6) to the external network NW. The communication of node v1 includes LAN communication in addition to electric field communication.

[0049] The node t1 corresponds to the function of the terminal 5 inside the container 2. The communication of the node t1 includes M2M communication in addition to electric field communication. The M2M communication is performed by the M2M communication device 51 of the terminal 5 (FIG. 3).

[0050] The node s corresponds to the function of the sensing terminal 4. The communication of the node s includes M2M communication. The M2M communication is provided by the M2M communication device 42 of the sensing terminal 4 (FIG. 2).

[0051] 7 and 8 are diagrams showing examples of node configurations of a communication system, in which the electric field communication network is referred to as electric field communication network 1N.

[0052] In the example shown in FIG. 7, node g exists between the external network NW and multiple container stacks 1. In each of the multiple container stacks 1, node v1, node t1, and node s exist. Node v1 is the highest node (on the node g side), and node s is the lowest node. Node t1 is a node between node v1 and node s.

[0053] Node s transmits sensing data to node t1. Node t1 transmits sensing data from node s to node v1. Node v1 transmits sensing data from node t1 indirectly (via node g) to an external network NW.

[0054] In the example shown in Fig. 8, a node vg exists instead of the node v1 (Fig. 7). The node vg transmits the sensing data from the node t1 directly to the external network NW.

[0055] In the communication system 100, the node configuration can change dynamically. For example, due to the loading or unloading of containers 2, some of the multiple containers 2 that were previously included in the container stack 1 are no longer included in the container stack 1. The node (e.g., node t1) corresponding to the terminal 5 that was attached to that container 2 is removed from the node configuration. The node (node ​​s) corresponding to the sensing terminal 4 that was housed in that container 2 is also removed from the node configuration. The same applies when the cargo 3 and sensing terminal 4 that were housed in some of the containers 2 are removed from those containers 2.

[0056] The above-described change in node configuration also changes previously established connections between multiple terminals 5. For example, connections with some of the multiple terminals 5 are no longer established. The multiple terminals 5 reconstruct the electric field communication network 1N (dynamically construct the electric field communication network 1N) in response to the change in connections. For example, when a terminal 5 (e.g., node t1) that has left the electric field communication network 1N because its connection is no longer established is detected, the remaining terminals 5 construct a new electric field communication network 1N that does not include the terminal 5 that has left.

[0057] The electric field communication network 1N is reconstructed in response to changes in the node configuration, thereby maintaining the functionality of the communication system 100. For example, even if the number or installation state of the sensing terminals 4 and 5 changes, the sensing data of the luggage 3 stored in the container 2 can still be extracted to the outside of the container 2 and transmitted to the external network NW.

[0058] 2. Application example to container ships A description will be given of an application example of the communication system 100. For example, the communication system 100 is applied to transportation means such as a container ship that transports containers 2, ports, warehouses that store containers 2, and the like.

[0059] FIG. 9 is a diagram showing an example of application of a communication system to a container ship. The container ship is shown as a container ship 7. Communication with an external network NW is satellite communication using an artificial satellite 8. Multiple containers 2 are stacked on the upper and lower sides of the deck of the container ship 7. An electric field communication network can be constructed for each container stack on each of the upper and lower sides of the deck. In FIG. 9, the terminal 5 is shown as node t1, node v1, or node vg. Below, an example will be described in which sensing data from the container 2 located lowest on the lower side of the deck is extracted outside the container 2 and transmitted to the external network NW.

[0060] As indicated by an arrow AR1, node t1 transmits sensing data to node v1 or node vg above it (near the deck) by electric field communication via the electric field communication network below.

[0061] When the node vg near the deck receives the sensing data, the node vg transmits the sensing data to the external network NW as indicated by the arrow AR2.

[0062] When node v1 near the deck receives the sensing data, as indicated by arrow AR3, node v1 transmits the sensing data to node g or node vg provided on the upper part of the container ship 7. For example, node v1 transmits the sensing data to node g or node vg using LAN communication. From there, the sensing data is transmitted to the external network NW. Alternatively, the sensing data may be transmitted to node vg via the upper electric field communication network. For example, node v1 transmits the sensing data via LAN communication to another node v1 (not shown) also provided near the deck and connected to the upper electric field communication network. The other node v1 transmits the sensing data from node v1 to node vg provided on the upper part of the container ship 7 via the upper electric field communication network. From there, the sensing data is transmitted to the external network NW.

[0063] For example, in the manner described above, the communication system 100 extracts sensing data of the cargo 3 stored in the container 2 on board the container ship 7 and transmits it to the external network NW. Without laying cables or the like, the sensing data can be relayed up to the top floor where radio waves can be transmitted to, for example, an artificial satellite 8.

[0064] 3. Second embodiment In the above, an example has been described in which one terminal 5 is attached to the outside of the container 2. However, a plurality of terminals 5 may be attached to the outside of the container 2. This will be described with reference to Figs. 10 to 13.

[0065] FIG. 10 is a diagram illustrating an example of a schematic configuration of a communication system according to the second embodiment. Unless otherwise specified, the following description will be made with reference to one container stack 1 shown on the left side of FIG. 10. In this example, each of the illustrated containers 2 contains luggage 3 and a sensing terminal 4, and a terminal 5 (node ​​t1) is provided inside each of the containers. However, similar to the communication system 100 (FIG. 1) described above, there may be containers 2 that do not contain luggage 3 and a sensing terminal 4, or that do not have a terminal 5 attached inside.

[0066] In the illustrated communication system 100A, the multiple terminals 5 include multiple terminals 5 (second electric field communication terminals) attached to the outside of the container 2. Nodes corresponding to the functions of the terminals 5 outside the container 2 are referred to and illustrated as node vg, node v2, or node t2. In this example, a terminal 5 is attached to the outside of each of the multiple containers 2. Also, in this example, the terminal 5 on the outside of the container 2 is attached on the opposite side of the container 2 from the terminal 5 (node ​​t1) inside the container 2. The multiple terminals 5 on the outside of the container 2 are located at different positions in the height direction of the container stack 1. However, the number and positions of the multiple terminals 5 provided on the outside of the container stack 1 are not limited to the example shown in FIG. 10.

[0067] Any of the multiple terminals 5 outside the container 2 may be capable of transmitting sensing data from the terminals 5 inside the container 2 to the external network NW. In the communication system 100A, any of the multiple terminals 5 outside the container 2 may aggregate (collect) the sensing data and transmit it to the external network NW. This, for example, improves the efficiency of transmitting sensing data to the external network NW.

[0068] Hereinafter, a terminal 5 that transmits sensing data to the external network NW will also be referred to as a "parent device." A terminal 5 that does not transmit sensing data to the external network NW will also be referred to as a "child device." A node corresponding to the function of a parent device is node vg or node v2. A node corresponding to the function of a child device is node t2 or node t1.

[0069] 11 is a diagram showing an example of node types and communication. Compared to the previously described FIG. 6, node v2 exists instead of node v1. Also, node t2 exists in addition.

[0070] Node v2 and node t2 correspond to the functions of a terminal 5 outside the container stack 1. The communication of node v2 includes LAN communication in addition to electric field communication. Node t2 includes electric field communication.

[0071] 12 and 13 are diagrams showing examples of node configurations of a communication system. In the example shown in FIG. 12, node g exists between an external network NW and multiple container stacks 1. In each of the multiple container stacks 1, node v2, node t2, node t1, and node s exist. Node v2 is the highest node (node ​​g side), and node s is the lowest node. Node t1 and node t2 are nodes between node v2 and node s. Node t1 is a node higher than node t2 (node ​​v2 side). Node t2 is a node lower than node t1 (node ​​s side).

[0072] Node s transmits sensing data to node t1. Node t1 transmits sensing data from node s to node t2 or node v2. Node t2 transmits sensing data from node t1 to node v2. Node v2 transmits sensing data from node t1 or node t2 indirectly (via node g) to the external network NW.

[0073] In the example shown in Fig. 13, a node vg exists instead of the node v2 (Fig. 12). The node vg transmits the sensing data from the node t1 or the node t2 directly to the external network NW.

[0074] In the communication system 100A, the multiple terminals 5 also reconstruct the electric field communication network 1N in response to changes in the connections between them (dynamically constructing the electric field communication network 1N). For example, when a terminal 5 (e.g., node vg, node v2, node t1, or node t2) that has left the electric field communication network 1N because a connection is no longer established is detected, the remaining terminals 5 construct a new electric field communication network 1N that does not include the terminal 5 that has left.

[0075] In the communication system 100A, the reconstruction of the electric field communication network 1N may also include changing the master device. For example, even if the master device leaves the electric field communication network 1N for some reason, such as loading or unloading of the container 2, failure, removal, or movement of the master device, a new master device is determined, and the master device transmits the sensing data to the external network NW. By dynamically changing the master device in this way, it is possible to maintain the transmission of the sensing data to the external network NW.

[0076] The multiple terminals 5 determine one terminal 5 of the multiple terminals 5 as a parent terminal (node ​​vg or node v2), and determine the other terminals 5 as child terminals (node ​​t1 or node t2). The parent terminal transmits the sensing data received by the child terminals from the sensing terminals 4 to the external network NW.

[0077] In one embodiment, the plurality of terminals 5 determine a master device based on the reliability of communication from each terminal 5 to the external network NW. The reliability of communication is calculated based on an evaluation of the communication situation.

[0078] Some examples of communication conditions will be described. For example, the communication conditions may include the presence or absence of wired connections in LAN communication or external network communication. The communication conditions may be evaluated (scored) so that the more wired connections there are, the higher the communication reliability. The communication conditions may include RSSI (Received Signal Strength Indication) strength in communication. The communication conditions may be evaluated so that the greater the RSSI strength, the higher the communication reliability. The communication conditions may include the presence or absence of gateway access. Gateway access is access to a communication interface with an external network NW, and is provided by, for example, the gateway device 6, the external NW communication device 54, etc. The communication conditions may be evaluated so that the communication reliability is higher when there is gateway access than when there is no gateway access. In addition to these, various communication conditions that can be used to evaluate communication reliability may be adopted.

[0079] Among the multiple terminals 5, the terminal 5 with the highest communication reliability may be determined as the parent device, and the other terminals 5 may be determined as child devices. For example, a terminal 5 that is wired or has a stronger RSSI strength than the other terminals 5 and can access the gateway may be determined as the parent device. By determining the terminal 5 with the highest communication reliability as the parent device, the reliability of transmission of sensing data to the external network NW can be increased.

[0080] The communication reliability may differ among the multiple terminals 5. The terminal 5 inside the container 2 cannot communicate with an external network or a LAN, and is therefore evaluated as having low communication reliability, and is therefore not determined as a parent device. The communication reliability of the multiple terminals 5 outside the container 2 is evaluated to some extent depending on the communication conditions of the external network communication and the LAN communication, and so there is a possibility that they may be determined as parent devices. The communication reliability of each of the multiple terminals 5 outside the container 2 may also differ from one another.

[0081] For example, as shown in FIG. 11, multiple terminals 5 outside a container 2 are located at different positions in the height direction of the container stack 1, i.e., in the stacking direction of the multiple containers 2, while an adjacent container stack 1 is located nearby. The lower the terminal 5, the greater the influence of the adjacent container stack 1, and the worse the communication situation may be. For example, the lower the terminal 5, the smaller the RSSI strength. The upper terminal 5 is less influenced by the adjacent container stack 1, and the worsening of the communication situation may be suppressed more than the lower terminal 5. For example, the higher the terminal 5, the greater the RSSI strength obtained compared to the lower terminal 5. Therefore, there is an advantage to (dynamically) determining the master unit based on communication reliability.

[0082] In order to determine a master device based on the communication status as described above, each of the multiple terminals 5 generates terminal information including the communication status and transmits (transmits) it to the electric field communication network 1N. The multiple terminals 5 share the terminal information and determine a master device based on the communication reliability that is uniquely calculated from the terminal information. The terminal information will be described with reference to FIG. 14.

[0083] 14 is a diagram showing an example of terminal information. The terminal information includes "myinfo" and "nodes." "myinfo" is information about the terminal 5 (own terminal information). "nodes" is information about other terminals 5 (other terminal information).

[0084] Examples of "myinfo" include "myid," "node type," "whether or not there is a wired connection," "RSSI strength," "gateway access," and "number of small sensing terminals." "myid" is information (terminal ID) for uniquely identifying terminal 5. "Node type" indicates the node type of terminal 5, more specifically, whether terminal 5 is a parent device or a child device. "whether or not there is a wired connection," "RSSI strength," and "gateway access" are examples of communication conditions for evaluating the communication reliability mentioned above. "Number of small sensing terminals" indicates the number of sensing terminals 4 that have established connections with that terminal 5.

[0085] "Nodes" includes one or more "nodeinfo." "Nodeinfo" is myinfo of other terminals 5, and in this example is schematically shown as "nodeinfo_1," "nodeinfo_2," "nodeinfo_k," etc.

[0086] The nodes in the terminal information are generated based on the myinfo and nodes included in the terminal information from other terminals 5 previously received.

[0087] For example, each of the multiple terminals 5 broadcasts its terminal information to all other terminals 5. As a result, each of the multiple terminals 5 receives the terminal information from the other terminals 5 with which a connection has been established. Each of the multiple terminals 5 incorporates (merges) the received terminal information from the other terminals 5 into the "nodeinfo" of terminal information that it generates, while eliminating duplication. Sharing the terminal information among the multiple terminals 5 makes it possible to determine a parent device, for example, as described above.

[0088] In one embodiment, a slave device may relay sensing data from other slave devices to the master device. Even if there is a slave device that cannot directly communicate with the master device (i.e., it is out of range and no connection has been established), the sensing data from that slave device can be transmitted to the master device.

[0089] For example, if the nodes included in the terminal information from the child device include the node info of a child device that has not established a connection with the parent device, the parent device determines that a child device exists outside its communication range. The parent device requests a child device with an established connection to transmit (relay) sensing data from other child devices to the parent device. The child device that is requested to relay transmits sensing data from other child devices with which it has established a connection (including child devices outside the communication range of the parent device) to the parent device.

[0090] When there are multiple slave devices that can request the relaying, the master device may select a slave device that requests relaying so that the communication load of the relaying is distributed among the multiple slave devices. The communication load distribution may take into consideration the communication conditions (reliability, etc.) of electric field communication between the slave devices. For example, the communication load may be distributed so that the communication load is smaller for slave devices with poorer electric field communication conditions.

[0091] 4. Example Use Cases 15 is a flowchart showing an example of a use case of a communication system. Description of content that overlaps with the content that has been explained so far will be omitted where appropriate.

[0092] In step S1, an electric field communication terminal is attached to a container. Each of the plurality of terminals 5 is attached to the inside or outside of the container 2.

[0093] In step S2, the luggage and the sensing terminal are housed in a container. An arbitrary container 2 houses luggage 3 and a sensing terminal 4.

[0094] In step S3, the containers are stacked to obtain a container stack. A plurality of containers 2 are stacked to obtain one or more container stacks 1.

[0095] In step S4, an electric field communication network is established. The multiple terminals 5 provided in the container stack 1 establish connections with each other by, for example, pairing through electric field communication. An electric field communication network 1N is established by the container stack 1 and the multiple terminals 5. Connections between the sensing terminals 4 and the terminals 5 inside the containers 2 are also established.

[0096] In step S5, the sensing data is extracted from the container 2 and transmitted to an external network. Details are as described above, and will be described again later with reference to Figs.

[0097] In step S6, the containers are unloaded. For example, some of the containers 2 among the plurality of containers 2 that make up the container stack 1 are unloaded.

[0098] In step S7, the detached electric field communication terminal is detected, and the electric field communication network is reconstructed. The connection between the terminal 5 attached to the container 2 that was unloaded in the previous step S6 and the terminal 5 attached to the container 2 that was not unloaded (remaining) is no longer established. It is detected that the terminal 5 attached to the unloaded container 2 has detached from the electric field communication network 1N. In response to the change in connection, the electric field communication network 1N is reconstructed. Specifically, the remaining terminals 5 excluding the detached terminal 5 newly construct an electric field communication network 1N that does not include the detached terminal 5.

[0099] In step S8, the luggage and the sensing terminal are removed from the container. For example, the luggage 3 and the sensing terminal 4 stored in one of the containers 2 among the multiple containers 2 that make up the container stack 1 are removed from that container 2.

[0100] In step S9, the detached sensing terminal is detected. The connection between the sensing terminal 4 removed from the container 2 in the previous step S8 and the corresponding terminal 5 is lost, and it is detected that the removed sensing terminal 4 has been detached.

[0101] Note that the above steps S6 and S8 are not limited to the order shown in the figure and can occur at any timing. Also, although not shown, there may be a step of adding a container. In that case, a new connection is established by the terminal 5 attached to the added container 2, and the electric field communication network 1N is reconstructed in response to the change in connection.

[0102] 5. Example of processing by electric field communication terminal 16 and 17 are flowcharts showing an example of processing (communication method) executed in an electric field communication terminal. The processing in this flowchart is repeatedly executed at a predetermined timing. The predetermined timing may be regular or irregular. The processing of each step is executed in the terminal 5 where that processing (function) is required.

[0103] In step S11, sensing data is received from the sensing terminal. The sensing terminal 4 (node ​​s) housed in the container 2 acquires sensing data of the luggage 3, for example, periodically, and transmits the data to a terminal 5 (node ​​t1) inside the same container 2 via M2M communication. The terminal 5 receives the sensing data from the sensing terminal 4.

[0104] In step S12, the communication status is confirmed. For example, in the communication system 100A (FIG. 11), the terminal 5 (node ​​vg or node v2) outside the container stack 1 confirms the communication status (presence or absence of a wired connection, RSSI strength, gateway access, etc.) and generates terminal information including the communication status.

[0105] In step S13, the sensing data is taken out of the container and transmitted to an external network. The terminal 5 inside the container 2 transmits the sensing data from the sensing terminal 4 to the terminal 5 outside the container 2. This sensing data is transmitted to the external network NW. For example, in the case of the communication system 100 (FIG. 1), the terminal 5 outside the container 2 (node ​​v1 or node vg) transmits the sensing data to the external network NW. In the case of the communication system 100A (FIG. 11), the parent terminal (node ​​vg or node v2) of the multiple terminals 5 outside the container 2 (node ​​vg, node v2, or node t2) transmits the sensing data to the external network NW.

[0106] FIG. 17 illustrates details of the process of step S13 (FIG. 16) when the master unit is dynamically determined in the communication system 100A (FIG. 11).

[0107] In step S21, a parent device is determined. Each of the multiple terminals 5 transmits (transmits) terminal information and shares the terminal information. As explained above, the parent device is determined based on the terminal information. A terminal 5 that was previously a parent device may continue to be determined as the parent device, or a terminal 5 that was previously a child device may be determined as the parent device (the parent device is changed). The determination result is reflected in the next terminal information that is transmitted.

[0108] In step S22, it is determined whether the own terminal is a parent device. If the own terminal is a parent device (step S22: Yes), the process proceeds to step S23. If not (step S22: No), the process proceeds to step S26.

[0109] The processes of steps S23 to S25 are executed in the parent device. In step S23, sensing data is requested from the child device. The parent device transmits a request (sensing data request) to transmit sensing data to the parent device to the child device. The sensing data request may be transmitted to all child devices that have established connections with the parent device.

[0110] In step S24, it is determined whether or not there is a slave device outside the communication range. For example, as described above, the master device determines that there is a slave device outside the communication range when the nodes included in the terminal information from the slave device include nodeinfo of a slave device that has not established a connection with the master device. If there is a slave device outside the communication range (step S24: Yes), the process proceeds to step S25. If not (step S24: No), the process proceeds to step S31.

[0111] In step S25, the slave devices are requested to relay the sensing data. The master device transmits a command (relay request) to the slave devices within the communication range, requesting that the slave devices relay the sensing data from the other slave devices to the master device.

[0112] The processes of steps S26 to S30 are executed in the slave device. In step S26, a request is received from the master device. The slave device receives the sensing data request or relay request from the master device.

[0113] In step S27, the process branches depending on the received request. If a sensing data request is received, the process proceeds to step S30. If a relay request is received, the process proceeds to step S28.

[0114] In step S28, sensing data is requested from other slave devices within the communication range. The slave device requests sensing data from other slave devices with which a connection has been established. In response to the request, the other slave devices transmit (reply) sensing data to the slave device. In step S29, the slave device receives the sensing data from the other slave devices.

[0115] In step S30, the sensing data is transmitted to the parent device. The child device transmits the sensing data requested up to that point to the parent device.

[0116] The processes of steps S31 and S32 are executed in the master device. In step S31, sensing data is received from the slave device. The master device receives the sensing data from the slave device. In step S32, the master device transmits the sensing data to the external network NW.

[0117] For example, in this manner, in the case of the communication system 100A, a master device is determined from the plurality of terminals 5, and the determined master device collects sensing data from the slave devices and transmits it to the external network NW.

[0118] 6. Variations The disclosed technology is not limited to the above-described embodiment, and several modifications will be described below.

[0119] The sensing terminal 4 may also be provided outside the container 2. In that case, a terminal 5 (second electric field communication terminal) outside the container 2 receives sensing data from the sensing terminal 4 by M2M communication. As an example of the node configuration in this case, the node configuration of the communication system 100 (FIG. 1) will be described.

[0120] 18 and 19 are diagrams showing examples of node configurations of a communication system. In the node configuration shown in FIG. 18, node v1 receives sensing data from node s as well, as compared to the node configuration in FIG. 7. The communication of node v1 also includes M2M communication. The node configuration when node vg is used instead of node v1 is as shown in FIG. 19. The communication of node vg also includes M2M communication.

[0121] In one embodiment, the terminal 5 may have only a device configuration according to the required functions (nodes). For example, if it is determined that the terminal 5 will be installed inside the container 2 and it is known that LAN communication and external network communication will not be performed, the terminal 5 does not need to have the LAN communication device 53 and the external NW communication device 54. This simplifies the configuration of the terminal 5 and reduces costs.

[0122] In one embodiment, an application for using the communication system 100 may be provided. The application may run on a computer such as a smartphone, tablet terminal, or laptop that can access the external network NW from a location separate from the communication system 100. The application may provide a user interface that accepts selection (user operation) of luggage 3 from which sensing data should be collected, and presents (displays, etc.) the collected sensing data.

[0123] 7.Example of effects The technology described above can be specified, for example, as follows. As described with reference to FIGS. 1 to 4 and 10 , the communication system 100 (or the communication system 100A) includes a plurality of containers 2 and a plurality of terminals 5 (electric field communication terminals). The plurality of containers 2 are conductive and stacked. The plurality of terminals 5 are attached to the containers 2 so as to be electrically coupled to any of the plurality of containers 2. The plurality of containers 2 includes a container 2 accommodating a sensing terminal 4 that acquires sensing data. The plurality of terminals 5 include a terminal 5 (first electric field communication terminal) attached inside the container 2 in which the sensing terminal 4 is accommodated, and a terminal 5 (second electric field communication terminal) attached outside at least one container 2 of the plurality of containers 2. The terminal 5 inside the container 2 transmits sensing data from the sensing terminal 4 to the terminal 5 outside the container 2 via the plurality of containers 2.

[0124] The above-described communication system 100 and the like make it possible to extract sensing data to the outside of the container 2. By using electric field communication, communication between the inside and outside of the container 2 can be made wireless. For example, there is no need to connect the inside and outside of the conductive container 2 with wires (by processing the walls, etc.). The device configuration is simplified, and the installation of the terminal 5 (attaching it to the container 2, etc.) can be easily performed.

[0125] As described with reference to Figures 7, 8, 12, and 13, the terminal 5 may construct an electric field communication network 1N by establishing connections with other terminals 5, and may reconstruct the electric field communication network 1N in response to changes in the connections. For example, the electric field communication network 1N may be reconstructed in response to a situation where some of the multiple terminals 5 no longer have connections. The electric field communication network 1N may also be reconstructed in response to a situation where some of the multiple containers 2 are no longer included. In this way, even if, for example, the number or installation state of the sensing terminals 4 and terminals 5 changes, the sensing data can still be extracted to the outside of the container 2.

[0126] As described with reference to Figures 1, 7, 8, 10, 12, and 13, the terminal 5 outside the container 2 may directly or indirectly transmit sensing data from the terminal 5 inside the container 2 to the external network NW. This makes it possible, for example, to collect sensing data via the external network NW. For example, the terminal 5 outside the container 2 may transmit sensing data to the external network NW via the gateway device 6. In this case, the terminal 5 outside the container 2 can be used as a network bridge terminal. Not only can the sensing data be extracted outside the container 2, but the sensing data can also be reliably transmitted to a terminal 5 installed in a location connectable to the external network NW.

[0127] 10 and the like, the multiple terminals 5 may include multiple terminals 5 outside the container 2, and the multiple terminals 5 may determine one terminal 5 of the multiple terminals 5 outside the container 2 as a parent device and determine the other terminals 5 as child devices, and the parent device may transmit the sensing data received by the child devices from the sensing terminals 4 to the external network NW. This may, for example, improve the efficiency of transmitting the sensing data to the external network NW.

[0128] The terminal 5 may reconstruct the electric field communication network 1N by changing the master device. This makes it possible to maintain transmission of sensing data to the external network NW, even if the master device leaves the electric field communication network 1N, for example.

[0129] The multiple terminals 5 may determine a master device based on the reliability of communication from each terminal 5 to the external network NW. For example, by determining the terminal 5 with the highest communication reliability as the master device, the reliability of transmission of sensing data to the external network NW can be increased. For example, as described with reference to FIG. 11 etc., even if the communication conditions may differ among the multiple terminals 5 outside the containers 2 located at different positions in the stacking direction of the multiple containers 2, the sensing data can be transmitted to the external network NW by an appropriately determined master device.

[0130] A slave unit may relay sensing data from other slave units to the master unit. This allows the sensing data from a slave unit that cannot directly communicate with the master unit (because it is outside the communication range) to be transmitted to the master unit.

[0131] 4 and the like, the terminal 5 may include an antenna 522 that is disposed to face the container 2 and generates dielectric polarization in the dielectric D between the terminal 5 and the container 2. For example, such an antenna 522 can be used to establish electric field coupling with the container 2.

[0132] The communication method described with reference to Fig. 16 etc. is also one of the embodiments. The communication method includes a terminal 5 (first electric field communication terminal) attached to the inside of a container 2 that houses a sensing terminal 4 that acquires sensing data, among a plurality of stacked containers 2 that are conductive, so as to be electrically coupled to the container 2, transmitting the sensing data from the sensing terminal 4 via the plurality of containers 2 to a terminal 5 (second electric field communication terminal) attached to the outside of at least one of the plurality of containers 2 so as to be electrically coupled to the container 2 (e.g., step S13). This communication method also makes it possible to extract the sensing data outside the container 2, as described above.

[0133] The effects described in this disclosure are merely examples and are not limited to the disclosed contents. Other effects may also be obtained.

[0134] Although the embodiments of the present disclosure have been described above, the technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, components of different embodiments and modifications may be combined as appropriate.

[0135] The present technology can also be configured as follows. (1) a plurality of stacked conductive containers; a plurality of electric field communication terminals attached to the containers so as to be electrically coupled to any of the plurality of containers; Equipped with the plurality of containers include a container that houses a sensing terminal that acquires sensing data, The plurality of electric field communication terminals include: a first electric field communication terminal attached to the inside of the container in which the sensing terminal is housed; a second electric field communication terminal attached to the outside of at least one of the plurality of containers; Including, the first electric field communication terminal transmits sensing data from the sensing terminal to the second electric field communication terminal via the plurality of containers; Communication system. (2) the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to a change in the connection; (1) A communication system according to (1). (3) the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to the connection of some electric field communication terminals among the plurality of electric field communication terminals being no longer established; A communication system according to (1) or (2). (4) the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to a fact that some of the plurality of containers are no longer included; A communication system according to any one of (1) to (3). (5) the second electric field communication terminal directly or indirectly transmits the sensing data from the first electric field communication terminal to an external network; A communication system according to any one of (1) to (4). (6) the second electric-field communication terminal transmits the sensing data to the external network via a gateway device; (5) A communication system according to (5). (7) the plurality of electric field communication terminals include a plurality of the second electric field communication terminals, the plurality of electric field communication terminals determine one of the plurality of second electric field communication terminals as a parent device and determine the other electric field communication terminals as child devices; The parent device transmits the sensing data received by the child device from the sensing terminal to an external network. A communication system according to any one of (1) to (6). (8) the electric field communication terminal establishes a connection with another electric field communication terminal to construct an electric field communication network, and reconstructs the electric field communication network by changing the parent device; (7) A communication system according to (7). (9) the plurality of electric field communication terminals determine the master device based on the communication reliability from each electric field communication terminal to the external network; A communication system according to (7) or (8). (10) The plurality of second electric field communication terminals are located at different positions in the stacking direction of the plurality of containers. A communication system according to any one of (7) to (9). (11) The slave device relays sensing data from other slave devices to the master device. A communication system according to any one of (7) to (10). (12) the electric field communication terminal includes an antenna provided to face the container and generating dielectric polarization in a dielectric between the container and the antenna; A communication system according to any one of (1) to (11). (13) a first electric field communication terminal attached to the inside of a container that houses a sensing terminal that acquires sensing data, among a plurality of stacked containers that are conductive, so as to be electrically coupled to the container, and transmits the sensing data from the sensing terminal via the plurality of containers to a second electric field communication terminal attached to the outside of at least one of the plurality of containers so as to be electrically coupled to the container; Including, Communication method. [Explanation of symbols]

[0136] 1. Container stack 2. Container 3. Luggage 4. Sensing terminal 41 Sensors 42 M2M communication devices 43 CPU 44 Storage device 5. Terminal 51 M2M communication devices 52 Electric field communication transmitter / receiver 521 Signal Processing Unit 522 Antenna 53 LAN communication equipment 54 External network communication device 55 CPU 56 Storage device 6 Gateway Device 61 LAN communication equipment 62 External network communication device 63 CPU 64 Storage device 7. Container ships 8 satellite 100 Communication Systems 1N Electric Field Communication Network NW External network D. Dielectric g-node vg node v1 node v2 node t1 node t2 node

Claims

1. a plurality of stacked conductive containers; a plurality of electric field communication terminals attached to the containers so as to be electrically coupled to any of the plurality of containers; Equipped with the plurality of containers include a container that houses a sensing terminal that acquires sensing data, The plurality of electric field communication terminals include: a first electric field communication terminal attached to the inside of the container in which the sensing terminal is housed; a second electric field communication terminal attached to the outside of at least one of the plurality of containers; Including, the first electric field communication terminal transmits sensing data from the sensing terminal to the second electric field communication terminal via the plurality of containers; Communication system.

2. the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to a change in the connection; The communication system of claim 1 .

3. the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to the connection of some electric field communication terminals among the plurality of electric field communication terminals being no longer established; The communication system of claim 1 .

4. the electric field communication terminal constructs an electric field communication network by establishing a connection with another electric field communication terminal, and reconstructs the electric field communication network in response to a fact that some of the plurality of containers are no longer included; The communication system of claim 1 .

5. the second electric field communication terminal directly or indirectly transmits the sensing data from the first electric field communication terminal to an external network; The communication system of claim 1 .

6. the second electric field communication terminal transmits the sensing data to the external network via a gateway device; The communication system according to claim 5 .

7. the plurality of electric field communication terminals include a plurality of the second electric field communication terminals, the plurality of electric field communication terminals determine one of the plurality of second electric field communication terminals as a parent device and determine the other electric field communication terminals as child devices; The parent device transmits the sensing data received by the child device from the sensing terminal to an external network. The communication system of claim 1 .

8. the electric field communication terminal establishes a connection with another electric field communication terminal to construct an electric field communication network, and reconstructs the electric field communication network by changing the parent device; The communication system according to claim 7.

9. the plurality of electric field communication terminals determine the master device based on the communication reliability from each electric field communication terminal to the external network; The communication system according to claim 7.

10. the plurality of second electric field communication terminals are located at different positions in the stacking direction of the plurality of containers; The communication system according to claim 7.

11. The slave device relays sensing data from other slave devices to the master device. The communication system according to claim 7.

12. the electric field communication terminal includes an antenna provided to face the container and generating dielectric polarization in a dielectric between the container and the antenna; The communication system of claim 1 .

13. a first electric field communication terminal attached to the inside of a container that houses a sensing terminal that acquires sensing data, among a plurality of stacked containers that are conductive, so as to be electrically coupled to the container, and transmitting the sensing data from the sensing terminal via the plurality of containers to a second electric field communication terminal attached to the outside of at least one of the plurality of containers so as to be electrically coupled to the container; Including, Communication method.

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