Communication device

Abstract

The present technology relates to a communication device that expands a communicable area to enable stable communication to be performed. N nodes are included, and each of the n nodes is provided with a power feeding point and a switch for switching between a path including the power feeding point and a path not including the power feeding point. The power feeding point and the switch are included in an insulator, in which structure the n nodes are connected in a row, with nodes located at ends being connected to metal conductors exposed in a conductive medium. The present technology can be applied, for example, to a communication device installed in a conductive medium and performing communication.

Description

Communication device

[0001] This technology relates to a communication device, and more particularly, to a communication device suitable for use in communication in a liquid, for example.

[0002] In recent years, wireless communications such as wireless LAN (Local Area Network) and contactless communication have become widely popular. In Patent Document 1, a proposal has been made for a communication device that communicates with a communication device separated in water.

[0003] Japanese Patent Application Laid-Open No. 2010-21874

[0004] It is desired to enable stable communication even in seawater or the like.

[0005] This technology has been made in view of such a situation, and enables stable communication even in seawater or the like.

[0006] The first communication device according to one aspect of the present technology includes n nodes, each of the n nodes includes a power supply point and a switch for switching a path including or not including the power supply point, the power supply point and the switch are configured to be encapsulated in an insulator, the n nodes are connected in a row, and among the n nodes, the node located at an end is connected to a metal conductor exposed in a conductive medium.

[0007] The second communication device according to one aspect of the present technology includes n nodes, each of the n nodes includes a communication unit for communicating with other nodes and a sensor, one of the n nodes further includes a power supply point, the n nodes are connected in a row, the node located at an end of the n nodes is connected to a metal conductor exposed in a conductive medium, the communication unit transmits information acquired by the sensor to the node including the power supply point, and the node including the power supply point transmits the information to another communication device.

[0008] A third communication device, representing one aspect of this technology, comprises a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, wherein the power supply point and the switch are enclosed within an insulator, and the insulator has terminals at both ends that are connected to a metal conductor or insulated cable exposed in a conductive medium.

[0009] In a first communication device representing one aspect of this technology, n nodes are provided, each of the n nodes is provided with a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, the power supply point and the switch are enclosed in an insulator, the n nodes are connected in a row, and the node located at the end of the n nodes is connected to a metal conductor exposed in a conductive medium.

[0010] In a second communication device, which is one aspect of this technology, n nodes are provided, each of the n nodes is equipped with a communication unit that communicates with the other nodes and a sensor, one of the n nodes is further equipped with a power supply point, the n nodes are connected in a row, the node located at the end of the n nodes is connected to a metal conductor exposed in a conductive medium, the communication unit transmits information acquired by the sensor to the node equipped with the power supply point, and the node equipped with the power supply point transmits the information to the other communication device.

[0011] In a third communication device representing one aspect of this technology, a power supply point and a switch for switching between a path including the power supply point and a path that does not include the power supply point are provided, the power supply point and the switch are enclosed within an insulator, and terminals are provided at both ends of the insulator for connecting to a metal conductor or insulated cable exposed in a conductive medium.

[0012] The communication device may be an independent device or an internal block that makes up a single device.

[0013] This figure shows the configuration of one embodiment of a communication system to which this technology is applied. This figure shows an example of the configuration of a slave station. This figure illustrates the position of the power supply point and the range of the electromagnetic wave communication area. This figure shows an example of the configuration of a communication device. This figure shows an example of the configuration of a communication device. This figure shows an example of the configuration of a communication device. This figure illustrates the switching of the switch during radiation. This figure illustrates the expanded communication area. This figure shows an example of the configuration of a communication device in the second embodiment. This figure shows an example of the configuration of a communication device in the third embodiment. This figure shows an example of the configuration of a communication device in the fourth embodiment. This figure shows an example of the configuration of a communication device in the fifth embodiment. This figure shows an example of the configuration of a communication device in the sixth embodiment. This figure shows an example of the configuration of a communication device in the sixth embodiment. This figure shows an example of the configuration of a communication device in the seventh embodiment. This figure shows an example of the configuration of a communication device in the eighth embodiment. This figure illustrates the operation of the communication device in the eighth embodiment. This figure illustrates the operation of the system.

[0014] The following describes the embodiments for implementing this technology.

[0015] <Configuration of the Communication System> Figure 1 shows the configuration of one embodiment of a communication system 1 to which this technology is applied. The communication system 1 shown in Figure 1 includes a master station 11, a communication station 12, a communication station 13, a satellite 14, slave stations 21-1 to 21-6, slave stations 31-1, 31-2, and a repeater 32. In the following description, when it is not necessary to distinguish between slave stations 21-1 to 21-6 individually, they will simply be referred to as slave station 21. The same applies to other parts.

[0016] The master station 11 and the communication station 12 communicate using, for example, local 5G. The master station 11 and the communication station 13 communicate using, for example, LPWA (Low Power Wide Area). The master station 11 is configured to acquire location information from satellite 14 using, for example, GNSS (Global Navigation Satellite System). Here, we will continue the explanation using local 5G, LPWA, and GNSS as examples, but it is also possible to configure the system to use other communication networks, such as WLAN (Wireless Local Area Network) or satellite communication networks.

[0017] The master station 11 also communicates with the slave station 21. Of the master station 11, the part that communicates with the aforementioned communication stations 12 and 13, and the satellite 14 is located in the air, while the part that communicates with the slave station 21 is located in seawater. The slave station 21 is located in seawater.

[0018] Here, we will use the example of a scenario where the communication system 1 is installed in the sea, but it can also be installed in environments such as lakes, ponds, rivers, and aquariums. The technology described below can be applied to devices installed in media other than lossless air (lossy media). Lossy media include not only the aforementioned seawater and brackish lakes, but also the inside of the human body.

[0019] Here, we will explain that one of the master stations 11 is located in the air (gas) and the other is located in seawater (liquid), but it is also possible for one of the master stations 11 to be located on the seabed (solid) or in a vacuum.

[0020] The configuration of communication system 1 shown in Figure 1 is an example and not an exhaustive description. In communication system 1 shown in Figure 1, the master station 11 is shown as communicating with communication stations 12, 13, and satellite 14, but it may also have the function to communicate with other devices, or it may not have the function to communicate with all of them, but may be configured to communicate with one or two of them. The master station 11 may also have the function to communicate only with slave station 21, in other words, it may not have the function to communicate with communication stations 12, 13, or satellite 14.

[0021] Each of the slave stations 21-1 to 21-6 communicates with the master station 11. A so-called ad-hoc network may be configured in which the slave stations 21 communicate with each other. For example, each slave station 21 is equipped with a sensor that senses the underwater environment and transmits the sensed data to the master station 11. Each slave station 21 can be configured to have only a transmission function that sends data to the master station 11, or it can be configured to have both a transmission function and a reception function that sends and receives data with the master station 11 and other slave stations 21. The slave stations 21 are installed at a depth of, for example, between 0 and 10 meters from the sea surface.

[0022] Substations 31-1 and 31-2 each communicate with the repeater 32. Substation 31 is equipped with a sensor that senses the underwater environment and transmits the sensed data to the repeater 32. Substation 31 can be configured to have only a transmission function that sends data to the repeater 32, or it can be configured to have both a transmission function and a reception function that sends and receives data to and from the repeater 32 and other substations 31. Substation 31 is installed on the seabed (or near the seabed).

[0023] The repeater 32 and the master station 11 can be configured to communicate via wired connection or via optical communication.

[0024] The signal from the substation 21 installed underwater is propagated to the master station 11 via two paths: a direct wave that travels in a straight line between the antenna of the substation 21 and the antenna of the master station 11, and a lateral wave that travels vertically upward from the antenna of the substation 21 to the sea surface directly above it, emerges at the sea surface, travels along the sea surface, and travels from the sea surface to the antenna of the master station 11 directly above it.

[0025] If the attenuation of the lateral wave is less than that of the direct wave, the lateral wave becomes dominant and is received by the master station 11. Since lateral waves propagate further than direct waves, the lateral wave becomes dominant as the distance between the slave station 21 and the master station 11 increases. This phenomenon occurs when the antenna is not far from the sea surface.

[0026] The signal from the substation 31 installed on the seabed is propagated to the repeater 32 via two paths: a direct wave that travels in a straight line between the antenna of substation 31 and the antenna of repeater 32, and a signal that travels vertically downward from the antenna of substation 31 to the seabed directly below it, travels along the seabed, and then travels from the seabed to the antenna of repeater 32 near the antenna of repeater 32.

[0027] The signal propagated from the slave station 31 into the seawater undergoes significant attenuation, but the signal propagated along the seabed from the slave station 31 undergoes less attenuation. Therefore, the repeater 32 receives the signal propagated along the seabed. Using a signal propagated along the seabed allows for a wider network coverage. Power consumption of the slave station 31 can be reduced. When the slave station 31 is configured to form a mesh network, the number of terminals required for that mesh network can be reduced.

[0028] <Outer Structure of the Substation> The master station 11 and substation 21 have the configuration shown in Figure 2. Here, we will continue the explanation using substation 21 as an example, but the configuration can also be applied to the master station 11.

[0029] As shown in Figure 2A, the slave station 21 includes a feed point 121, to which wiring 111, which forms part of the antenna, is connected. The wiring 111 can function as a current antenna, which is formed, for example, as a dipole antenna. The feed point 121 and the wiring 111 are enclosed in an insulator 112.

[0030] The substation 21 is expected to be installed in a conductive medium such as underwater. When the substation 21 is installed in a conductive medium, the feed point 121 and the wiring 111 (the part that will become the antenna) are configured to be covered with an insulator 112 so that they do not come into contact with the conductive medium. The substation 21 is equipped with a sensor 122, and the sensor 122 is connected to a data processing unit (not shown) located inside the insulator 112.

[0031] The insulator 112 can be, for example, pure water, resin material, or air, and a substance with low conductivity can be used. The insulator 112 may be composed of multiple materials. For example, the insulator 112 can be a resin housing filled with pure water, air, insulating oil, etc., and the power supply point 121 and wiring 111 can be enclosed within that housing.

[0032] The electrodes at both ends of the wiring 111 that are exposed outside the insulator 112 may be formed of spherical electrodes 101-1 and 101-2, which are formed as spheres.

[0033] In the following explanation, the portion of the slave station 21 shown in Figure 2A that excludes the sensor 122 and the spherical electrode 101 will be referred to as a node as appropriate.

[0034] To expand the electromagnetic wave communication area of ​​the slave station 21, one can enlarge the portion of the slave station 21 that acts as an antenna. Specifically, as shown in Figure 2B, by making the wiring 111 connected to the feed point 121 within the node longer, the overall size of the slave station 21 can be increased, thereby enlarging the portion that effectively functions as an antenna and expanding the electromagnetic wave communication area.

[0035] In Figure 2B, the slave station 21 has its power supply point 121 located in the center of the node, and the length of the wiring 111 connected to the power supply point 121 is long.

[0036] The slave station 21 shown in Figure 2C has a configuration in which the power supply point 121 is located on the left side of the figure. In the slave station 21 shown in Figure 2C, the node is located on the left side of the figure, and the node and the spherical electrode 101-2 are connected by wiring 131, so that the slave station 21 as a whole is formed to be about the same size as the slave station 21 shown in Figure 3B.

[0037] As shown in Figure 2B and Figure 2C, the electromagnetic wave communication area can be expanded by making the antenna portion larger, as in the slave station 21.

[0038] Figure 3A shows the electromagnetic wave communication area of ​​the slave station 21 shown in Figure 2B, and Figure 3B shows the electromagnetic wave communication area of ​​the slave station 21 shown in Figure 2C. In Figure 3, areas of the same intensity are represented by the same color density. Comparing Figure 3A and Figure 3B, it can be seen that the extent of the electromagnetic wave communication area is approximately the same.

[0039] In Figure 2B and Figure 2C, the electrical length of the parts of the substation 21 other than the exposed electrode (spherical electrode 101) is longer than that of the exposed part, which indicates that balanced power supply is possible regardless of the location of the power supply point.

[0040] From the results in Figure 3, it can be seen that the electromagnetic wave communication area has approximately the same distribution regardless of the position of the power supply point 121. Taking advantage of this, the configuration of the slave station 21 (a communication device to which this technology is applied), which can expand the electromagnetic wave communication area, is described below.

[0041] <Configuration of the Communication Device> Figure 4 shows the configuration of one embodiment of a communication device 200 to which this technology is applied. The communication device 200 can be used as, for example, a master station 11, a slave station 21, and a repeater 32. Here, the explanation will continue with the case where the communication device 200 is a slave station 21 as an example.

[0042] The communication device 200 is configured to include nodes 201-1 and 201-2. A sensor 202-1 is connected to node 201-1, and a sensor 202-2 is connected to node 201-2. A spherical electrode 101-1 is connected to the left side of node 201-1, and a spherical electrode 101-2 is connected to the right side of node 201-2. Nodes 201-1 and 201-2 are connected by an insulating cable 203. The insulating cable 203 is a cable in which conductor wiring is encapsulated in an insulator, and a coaxial cable or the like can be used.

[0043] The communication device 200 has a configuration in which the spherical electrode 101-1, node 201-1, insulating cable 203, node 201-2, and spherical electrode 101-2 are connected in a row.

[0044] The communication device 200 may be configured to be disassembled into individual parts as shown in FIG. 5. That is, the communication device 200 can be divided into three parts: a node 201, an insulating cable 203, and a spherical electrode 101, and can be configured to be manufactured and sold for each of these parts. The node 201 includes connectors 221-1 and 221-2 connected to the spherical electrode 101 or the insulating cable 203 at both ends. The connector 221 can use a waterproof connector.

[0045] The insulating cable 203 is composed of a conductor wiring 203a and an insulator 203b that encapsulates the conductor wiring 203a. The insulating cable 203 includes connectors 222-1 and 222-2 connected to the spherical electrode 101 or the node 201 at both ends. The connector 222 can use a waterproof connector.

[0046] The spherical electrode 101 includes a connector 223 connected to the insulating cable 203 or the node 201 at a part of its outer periphery. The connector 223 can use a waterproof connector. The spherical electrode 101 has an insulating thin film for corrosion prevention applied to a metal conductor. Here, the case of a spherical electrode is taken as an example for continuing the explanation, but a metal conductor formed in a shape other than a sphere may also be used.

[0047] By combining these nodes 201, insulated cables 203, and spherical electrode 101, each part may be formed so that the communication device 200 shown in FIG. 4 is configured.

[0048] Returning to the description of the communication device 200 shown in FIG. 4. Node 201-1 includes a switch 211-1, a switch 212-1, a power supply point 213-1, and a wiring 214-1, and these are configured to be enclosed in an insulator 215-1. Node 201-1 has, for example, the same configuration as the slave station 21 shown in FIG. 2.

[0049] The communication device 200 having such a configuration is installed in a conductive medium and is configured to exhibit better performance when installed in the conductive medium. As an example of the conductive medium in which the communication device 200 is installed, it is a medium having an electrical conductivity of 0.5 S / m or more.

[0050] <Internal Configuration Example of Communication Device> FIG. 6 shows an internal configuration example of the communication device 200, mainly the configuration of the part corresponding to the node 201. The communication device 200 is configured to include a sensing unit 251, a signal processing unit 252, a high-frequency processing unit 253, an RF transceiver unit 254, an inter-node communication unit 255, a switching unit 256, and a control unit 257.

[0051] The communication device 200 can be a mobile station such as an underwater drone or a robot disposed in water. The communication device 200 is configured to include, in the sensing unit 251, for example, sensors for observing water temperature, tidal current, etc., and image sensors, etc., and can also be installed at a specific position.

[0052] The data sensed by the sensing unit 251 is supplied to the high-frequency processing unit 253. The high-frequency processing unit 253 is configured to process the received signal or to process the received signal and the transmitted signal. The operating frequency fw of the high-frequency processing unit 253 is set, for example, to 1 MHz or less.

[0053] The high-frequency processing unit 253 takes the supplied data as a baseband signal, performs the necessary processing on the baseband signal, for example, operates at the operating frequency fw, converts the frequency to a signal of frequency fw, and transmits it via the RF transceiver unit 254 to other communication devices 200 (slave station 21), repeater 32, or master station 11. The RF transceiver unit 254 transmits or receives signals transmitted and received underwater.

[0054] The signal received by the RF transceiver 254 is supplied to the high-frequency processing unit 253. The high-frequency processing unit 253 performs processing on the received signal, such as demodulation, and extracts data as needed.

[0055] As shown in Figure 4, the communication device 200 can be configured to include two or more nodes 201. In the case of a communication device 200 with two or more nodes 201, the inter-node communication unit 255 controls the communication between the nodes 201.

[0056] The switching unit 256 includes switches 211 and 212 (Figure 4) and controls the switching of these switches 211 and 212. The control unit 257 controls each part of the communication device 200.

[0057] The correspondence between the example configuration of the communication device 200 shown in Figure 6 and the example configuration of the communication device 200 shown in Figure 4 will be explained.

[0058] The power supply point 213-1 within node 201-1 shown in Figure 4 corresponds to the RF transceiver 254 shown in Figure 6, and can be configured, for example, with an RFIC (Radio Frequency Integrated Circuit). Switches 211-1 and 212-1 within node 201-1 shown in Figure 4 correspond to the switching unit 256 shown in Figure 6. Switches 211 and 212 are appropriately referred to as RF switches.

[0059] The sensor 202-1 shown in Figure 4 is included in the sensing unit 251 shown in Figure 6. The signal processing unit 252, high-frequency processing unit 253, and control unit 257 shown in Figure 6 are not shown in Figure 4, but are included in node 201-1 (included in insulator 215-1) and connected to the power supply point 213-1 (RF transceiver 254).

[0060] Returning to the explanation with reference to Figure 4, the communication device 200 also includes node 201-2. Node 201-2 has the same configuration as node 201-1. Node 201-2 also includes switch 211-2, switch 212-2, power supply point 213-2, and wiring 214-2, all of which are enclosed within an insulator 215-2.

[0061] The communication device 200 is configured such that it is possible to select whether node 201-1 or node 201-2 will radiate by switching switches 211 and 212 (processing by the switching unit 256). The communication device 200 shown in Figure 7 shows an example where node 201-2 radiates.

[0062] Switches 211-1 and 212-1 of the non-radiating node 201-1 are both connected to wiring 214-1. The non-radiating node 201-1 is configured to have a selected path that does not include the power supply point 213-1.

[0063] Switches 211-2 and 212-2 of the radiating node 201-2 are both connected to the power supply point 213-2. The radiating node 201-2 is configured to have a selected path that includes the power supply point 213-2.

[0064] Switches 211-1 and 212-1 of node 201-1, which do not radiate, are both connected to wiring 214-1, creating a path that does not include feed point 213-1. In this path, switches 211-1, wiring 214-1, and switch 211-2 function as part of the antenna.

[0065] Although not shown in the diagram, when node 201-1 radiates, switches 211-1 and 212-1 of the radiating node 201-1 are both connected to the feed point 213-1, forming a path that includes the feed point 213-1. Switches 211-2 and 212-2 of the non-radiating node 201-2 are both connected to wiring 214-2, forming a path that does not include the feed point 213-2, in other words, includes wiring 214-2, and functions as part of the antenna.

[0066] In the state shown in Figure 7, the power supply point 213-2 located on the right side of the figure functions as the power supply point. Although not shown in the figure, as described above, the power supply point 213-1 located on the left side of the figure can also function as the power supply point. The communication device 200 is equipped with power supply points 213 on both the left and right sides of the figure, and is configured so that one of them radiates, and the radiating side can be switched.

[0067] As explained with reference to Figures 2 and 3, the electromagnetic wave communication area is not affected by the position of the feed point 121. That is, in the communication device 200 shown in Figures 5 and 7, the communication area when radiation is emitted from the feed point 213-1 located on the left side of the figure is approximately the same size and intensity as the communication area when radiation is emitted from the feed point 213-2 located on the right side of the figure.

[0068] In the communication device 200, the electromagnetic wave communication area can be expanded by increasing the size of the antenna portion, which includes the insulated cable 203 connecting the nodes 201.

[0069] The applicant has confirmed that when the length of the antenna including the insulated cable 203 is increased by half, for example, the length from the spherical electrode 101-1 to the center of the insulated cable 203 in Figure 4, the communication area expands in the radiating direction by the amount of the increase, up to a length that does not exceed the wavelength, but the communication area does not expand beyond the wavelength. From this, the distance between node 201-1 and node 201-2, in other words, the length of the insulated cable 203, is set to a length that can expand the communication area to the maximum extent possible, depending on the wavelength of the radiated signal.

[0070] Referring to Figure 8, we will explain how the communication area can be expanded and stable communication can be achieved using the communication device 200 shown in Figure 4. For comparison, Figure 8A shows the communication area when communication is performed using the slave station 21 shown in Figure 2A. Referring to Figure 8A, slave stations 21-1, 21-2, and 21-3 are arranged at a predetermined distance from each other.

[0071] The circles centered on each slave station 21 represent the communication area of ​​the slave station 21. For example, when slave station 21-1 and slave station 21-2 communicate, there is no overlap between the communication areas of slave station 21-1 and slave station 21-2, so they cannot communicate directly. Slave station 21-1 and slave station 21-2 communicate via repeater 32. Slave station 21-2 and slave station 21-3 also communicate via repeater 32, and slave station 21-3 and slave station 21-1 also communicate via repeater 32.

[0072] Figure 8B shows the communication area when communication is performed using the communication device 200 shown in Figure 4. Referring to Figure 8B, the communication device 200 and the slave station 21-3 are arranged at a predetermined distance from each other. Node 201-1, included in the communication device 200, is located at the position where slave station 21-2 is located in Figure 8A, and node 201-2 is located at the position where slave station 21-1 is located in Figure 8A. Suppose slave station 21-3 is located at the position where slave station 21-3 is located in Figure 8A.

[0073] As described above, the communication area of ​​the communication device 200 expands, and as shown in Figure 8B, the communication area extends in an elliptical shape that includes the communication device 200. There is an overlap between the communication area of ​​the communication device 200 and the communication area of ​​the slave station 21-3, making it possible for the communication device 200 and the slave station 21-3 to communicate directly.

[0074] If the same size communication area is to be secured, the configuration shown in Figure 8A requires the installation of communication devices (substations 21-1 to 21-3 and repeater 32) in four locations, whereas the configuration shown in Figure 8B only requires the installation of communication devices (communication device 200 and substation 21-3) in two locations. Therefore, by applying this technology, the entire system can be simplified and costs can be reduced.

[0075] <Example of the configuration of the communication device in the second embodiment> An example of the configuration of the communication device 200b in the second embodiment is shown in Figure 9. The communication device 200 shown in Figure 4 will be referred to as the communication device 200 in the first embodiment, and will be described as the communication device 200a as appropriate.

[0076] In the first embodiment of the communication device 200a (Figure 4), the spherical electrodes 101-1 and 101-2 provided at both ends of the communication device 200a are shown to be directly connected to nodes 201-1 and 201-2, respectively. However, as shown in Figure 9, the spherical electrode 101 can also be connected to an insulated cable 203.

[0077] In the communication device 200b shown in Figure 9, the spherical electrode 101-1 and node 201-1 are directly connected, node 201-1 and node 201-2 are connected by an insulated cable 203-1, and node 201-2 and spherical electrode 101-2 are connected by an insulated cable 203-2. Thus, node 201 and spherical electrode 101 can also be connected via an insulated cable.

[0078] In the example shown in Figure 9, node 201-2 and spherical electrode 101-2 are connected by an insulated cable 203-2. However, it is also possible to have a configuration where node 201-1 and spherical electrode 101-1 are connected by an insulated cable 203. Furthermore, it is also possible to have a configuration where node 201-1 and spherical electrode 101-1 are connected by an insulated cable 203, and node 201-2 and spherical electrode 101-2 are also connected by an insulated cable 203.

[0079] Since the size of the communication area does not change regardless of the location of the radiating node 201 within the communication device 200, the same effect can be obtained in the configuration shown in Figure 9 as in the configuration shown in Figure 4.

[0080] <Example of the configuration of the communication device in the third embodiment> An example of the configuration of the communication device 200c in the third embodiment is shown in Figure 10.

[0081] In the first embodiment, the communication device 200a (Figure 4), and in the second embodiment, the communication device 200b (Figure 9), were described using the example of having two nodes 201. However, the number of nodes 201 that a single communication device 200 has is not limited to two; it can also be configured to have three or more nodes.

[0082] The communication device 200c shown in Figure 10 includes three nodes 201: node 201-1, node 201-2, and node 201-3. In the example shown in Figure 10, the spherical electrode 101-1 is directly connected to node 201-1, node 201-1 and node 201-2 are connected by an insulated cable 203-1, node 201-2 and node 201-3 are connected by an insulated cable 203-2, and node 201-3 is directly connected to the spherical electrode 101-2.

[0083] Since the size of the communication area does not change regardless of the location of the radiating node 201 within the communication device 200, the same effect can be obtained in the configuration shown in Figure 10 as in the configuration shown in Figure 4.

[0084] It is also possible to implement a combination of the second and third embodiments, in which node 201-1 and spherical electrode 101-1 are connected by an insulated cable 203, and / or node 201-3 and spherical electrode 101-2 are connected by an insulated cable 203.

[0085] Figure 10 illustrates an example configuration including three nodes 201, but the communication device 200 can also consist of four or more n nodes 201 connected in a single line.

[0086] <Example of the configuration of the communication device in the fourth embodiment> An example of the configuration of the communication device 200d in the fourth embodiment is shown in Figure 11.

[0087] In the first embodiment of the communication device 200a (Figure 4), a configuration in which two nodes 201 are connected by an insulated cable 203 was described as an example. However, it is also possible to have a configuration in which the two nodes 201 are directly connected without using an insulated cable 203.

[0088] The communication device 200d shown in Figure 11 comprises two nodes 201, node 201-1 and node 201-2, which are directly connected. One end of switch 212-1 on node 201-1 and one end of switch 211-2 on node 201-2 are connected by a long wiring.

[0089] In other words, the communication device 200d includes two nodes 201, node 201-1 and node 201-2, but is formed as an integrated unit, with insulators 215-1 and 215-2 connected as if they were a single node 201.

[0090] In the example shown in Figure 11, the power supply point 213-1 is located to the left of node 201-1, and the power supply point 213-2 is located to the right of node 201-2. However, the power supply point 213-1 may be located in the center of node 201-1, or the power supply point 213-2 may be located in the center of node 201-2. Since the size of the communication area does not change regardless of the location of the radiating node 201 within the communication device 200, there is a high degree of flexibility in the placement of the power supply point 213 within node 201.

[0091] In the configuration shown in Figure 11, the same effect as in the configuration shown in Figure 4 can be obtained by configuring the communication device 200d to have a certain size (length). For example, the communication area can be expanded by increasing the length of the wiring placed between the power supply point 213-1 and the power supply point 213-2 (switch 212-1 and switch 211-2) and the insulator 215 that encloses that wiring.

[0092] The fourth embodiment can also be implemented in combination with either the second or third embodiment, or both. For example, node 201-1 and spherical electrode 101-1 can be connected by an insulated cable 203, and / or node 201-2 and spherical electrode 101-2 can be connected by an insulated cable 203. Alternatively, a communication device 200 can be provided in which three or more nodes 201 are directly connected.

[0093] <Example of the configuration of the communication device in the fifth embodiment> An example of the configuration of the communication device 200e in the fifth embodiment is shown in Figure 12.

[0094] In the first to fourth embodiments, the node 201 of the communication device 200 was described using the example of a case where it is equipped with two switches 211 and switch 212, but it is also possible to have a configuration that is equipped with one switch 211 or switch 212.

[0095] The node 201-1 of the communication device 200d shown in Figure 12 includes a switch 212-1, a power supply point 213-1, and wiring 214-1, all of which are enclosed within an insulator 215-1. One end of the power supply point 213-1 is connected to the wiring 214-1 and the spherical electrode 101-1, while the other end is connected to the switch 212-1.

[0096] Similarly, node 201-2 of the communication device 200d shown in Figure 12 includes a switch 211-2, a power supply point 213-2, and wiring 214-2, all of which are enclosed within an insulator 215-2. One end of the power supply point 213-2 is connected to wiring 214-2 and a spherical electrode 101-2, while the other end is connected to switch 211-2.

[0097] Thus, a configuration can be adopted in which one switch is provided within a single node 201, with the radiating side connected to the power supply point 213 and the non-radiating side connected to the wiring 214. In this case as well, it is possible to expand the communication area and obtain the same effects as in the configuration shown in Figure 4.

[0098] The fifth embodiment can also be implemented in combination with one or more of the second to fourth embodiments.

[0099] <Example of the configuration of the communication device in the sixth embodiment> An example of the configuration of the communication device 200f in the sixth embodiment is shown in Figure 13. In the communication device 200f shown in Figure 13, the spherical electrode 101 is not shown.

[0100] The communication device 200 in the first to fifth embodiments comprises node 201-1 and node 201-2, and is controlled so that when one node 201 is radiating, the other node 201 does not radiate.

[0101] In other words, one of the multiple nodes 201 is controlled to radiate while the other nodes 201 do not, and simultaneously, multiple nodes 201 are controlled not to radiate. To perform this control, a function is provided for communication between the nodes 201 so that they can agree on which node 201 will radiate and notify each node 201 of this agreement.

[0102] As shown in Figure 13, node 201-1 is equipped with an inter-node communication unit 255-1, and node 201-2 is equipped with an inter-node communication unit 255-2. Inter-node communication units 255-1 and 255-2 are connected by an optical fiber 302. Inter-node communication units 255-2 exchange instructions with each other using optical fiber communication.

[0103] For example, one of node 201-1 and node 201-2 is designated as the master and the other as the slave. The master node 201 issues instructions to the slave node 201 regarding the timing of radiation, in other words, instructions regarding the switching timing of switches 211 and 212 (switching unit 256). The slave node 201 performs the switching using the switching unit 256 based on the instructions from the master node 201. Such exchange of instructions takes place between node-to-node communication unit 255-1 and node-to-node communication unit 255-2 via optical fiber 302.

[0104] Optical terminals 303-1 and 304-1 are provided at the interface of both ends of node 201-1. One end of the inter-node communication unit 255-1 is connected to optical terminal 303-1 via an optical fiber wired inside node 201-1, and the other end is connected to optical terminal 304-1 via an optical fiber wired inside node 201-1.

[0105] Similarly, optical terminals 303-2 and 304-2 are provided at the interface of both ends of node 201-2. One end of the inter-node communication unit 255-2 is connected to optical terminal 303-2 via an optical fiber wired inside node 201-2, and the other end is connected to optical terminal 304-2 via an optical fiber wired inside node 201-2.

[0106] Optical terminal 304-1 of node 201-1 and optical terminal 303-2 of node 201-2 are each connected to optical fiber 302.

[0107] The system can be configured to allow communication between nodes 201 via a connection using such an optical fiber 302.

[0108] Referring to Figure 14, an example configuration of a communication device 200 in which communication is performed by the inter-node communication unit 255 without using optical fiber 302 will be described.

[0109] The communication device 200f' shown in Figure 14 is configured to allow communication between the node communication units 255 using an insulated cable 203 that connects node 201-1 and node 201-2.

[0110] The communication device 200f' shown in Figure 14, as in the embodiment described above, establishes communication between the nodes 201 by using an insulated cable 203 to connect the nodes 201 and superimposing a signal using a frequency sufficiently higher than that of RF communication using the insulated cable 203 as an antenna onto the RF wiring (insulated cable 203).

[0111] Node 201-1 is equipped with an inter-node communication unit 255-1 and an HPF (High-Pass Filter) 321-1. The inter-node communication unit 255-1 and the HPF 321-1 are connected, and the HPF 321-1 is connected to one end of switch 211-1 and one end of switch 212-1. Furthermore, the HPF 321-1 is also connected to an isolated cable 203 via an RF terminal so that signals from the inter-node communication unit 255-1 are transmitted to node 201-1 via the HPF 321-1.

[0112] Similarly, node 201-2 is equipped with an inter-node communication unit 255-2 and an HPF 321-2. The inter-node communication unit 255-2 and the HPF 321-2 are connected, and the HPF 321-2 is connected to one end of switch 211-2 and one end of switch 212-2. Furthermore, the HPF 321-2 is also connected to the isolated cable 203 via an RF terminal so that signals from the inter-node communication unit 255-2 are transmitted to node 201-2 via the HPF 321-2.

[0113] Communication via the inter-node communication unit 255 uses signals with a higher frequency than communication via the feed point 213 (communication via the RF transceiver unit 254 (Figure 6)). Since communication via the inter-node communication unit 255 is limited to between nodes 201, in other words, limited to within the communication device 200f', it can use signals with a higher frequency than communication via the feed point 213.

[0114] To prevent communication by the inter-node communication unit 255 from affecting communication by the power supply point 213, and to prevent communication by the power supply point 213 from affecting communication by the inter-node communication unit 255, an HPF 321 is provided, and the system is configured so that only the high-frequency components of the signal from the inter-node communication unit 255 are transmitted and received through the insulated cable 203.

[0115] Thus, communication between nodes 201 can also be configured to be performed via an RF line (insulated cable 203), in other words, superimposed on the RF path.

[0116] The sixth embodiment can be implemented in combination with any one or more of the first to fifth embodiments.

[0117] <Example of the configuration of the communication device in the seventh embodiment> An example of the configuration of the communication device 200g in the seventh embodiment is shown in Figure 15.

[0118] As explained with reference to Figures 13 and 14, if an inter-node communication unit 255 is provided within node 201 to enable communication between nodes 201, it is also possible to provide only one power supply point 213, and configure the system so that data obtained from multiple nodes 201 (sensors 202) is transmitted from that power supply point 213.

[0119] The communication device 200g shown in Figure 15 includes node 201-1 and node 201-2. Node 201-1 is configured to include a power supply point 213-1, an inter-node communication unit 255-1, and an HPF 321-1, while node 201-2 is configured to include an inter-node communication unit 255-2 and an HPF 321-2.

[0120] The communication device 200g shown in Figure 15 applies the configuration of the communication device 200f' shown in Figure 14, and shows a configuration in which communication between nodes 201 is superimposed on RF wiring (insulated cable 203). However, it is also possible to apply the configuration of the communication device 200f shown in Figure 13, and a configuration in which communication between nodes 201 is performed using optical fiber 302 is also possible.

[0121] Sensor information acquired by sensor 202-1 connected to node 201-1 is transmitted from node 201-1. Sensor information acquired by sensor 202-2 connected to node 201-2 is transmitted to node 201-1 by processing by the inter-node communication unit 255-2. When the inter-node communication unit 255-1 of node 201-1 receives sensor information transmitted from the inter-node communication unit 255-2, it transmits it via the power supply point 213-1 (RF transceiver 254) included in node 201-1.

[0122] Thus, a function is provided that allows communication between nodes 201, and a configuration can be set up where one of the multiple nodes 201 is responsible for transmission. Here, we have explained using a communication device 200g equipped with two nodes 201 as an example, but this can also be applied when the communication device 200g includes three or more nodes 201.

[0123] The seventh embodiment can be implemented in combination with any one or more of the first to fifth embodiments.

[0124] <Eighth Embodiment> An example of the configuration of the communication device 200h in the eighth embodiment is shown in Figure 16.

[0125] In the first to seventh embodiments, the communication device 200 was configured to include two or more nodes 201, but it can also be configured to include one node 201. The communication device 200h shown in Figure 16A includes a switch 211, a switch 212, a power supply point 213, and wiring 214, all of which are enclosed within an insulator 215. Spherical electrodes 101-1 and 101-2 are connected to both ends of the insulator 215.

[0126] As shown in Figure 16A, when switches 211 and 212 are connected to the wiring 214, the communication device 200h itself does not emit radiation. In this state, the communication device 200h can function as a passive repeater operating as a repeater.

[0127] As shown in Figure 16B, when switches 211 and 212 are connected to the power supply point 213, the communication device 200h is in a state where it is radiating sensor information acquired by sensor 202. In this state, the communication device 200h can function as a communication device (slave station 21).

[0128] An example of a use case for the communication device 200g shown in Figure 16 will be explained with reference to Figure 17.

[0129] The system configuration shown in Figure 17 is an example in which a communication device 200c, a slave station 21, and a communication device 200h are installed in the sea, and the communication device 200c and the master station 11 are connected by an optical fiber 401. The communication device 200c has the configuration of the communication device 200c shown in Figure 10 and has three nodes, Nodes 201-1 to 201-3. The slave station 21 has the configuration shown in Figure 2A. The communication device 200h has the configuration of the communication device 200h shown in Figure 16 and has one node 201.

[0130] Although the slave station 21 and the communication device 200c are within communication range, they are in a positional relationship where their polarizations are orthogonal, making direct communication impossible. In such a case, the slave station 21 first transmits data to the communication device 200h, and the communication device 200h then transfers the data to the communication device 200c.

[0131] As shown in Figure 16A, when the communication device 200h is not connected to the feed point 213, it can function as a passive repeater that is sensitive to both the polarization of the antenna of the communication device 200c and the polarization of the antenna of the slave station 21. By using the communication device 200h functioning as a passive repeater, a system can be constructed that appears to allow the slave station 21 to communicate directly with the communication device 200c.

[0132] Since the substation 21 and the communication device 200c are installed underwater, their relative positions may change, potentially resulting in a situation where their polarizations become orthogonal, making direct communication impossible. In such a situation, as described above, by making the communication device 200h function as a passive repeater and enabling communication via the communication device 200h, stable communication can be ensured, improving the overall communication stability of the system.

[0133] Furthermore, while it is possible to configure the system so that communication is performed via the communication device 200h when the slave station 21 and the communication device 200c are unable to communicate directly, it is also possible to configure the system so that communication is performed via the communication device 200h even when direct communication is not impossible.

[0134] The communication device 200h can be configured to have switches 211 and 212 to switch between a mode in which it functions as a passive repeater and a mode in which it functions as a slave station 21 (communication device). By enabling communication through the communication device 200h functioning as a passive repeater, the communication range can be expanded and stable communication can be achieved.

[0135] <System Operation> The operation of the system including the communication device 200 in the first to seventh embodiments will be described with reference to Figure 18.

[0136] The system configuration shown in Figure 18 is an example in which a communication device 200c, a slave station 21, a communication device 200a, and a communication device 200i are installed in the sea, and the communication device 200c and the master station 11 are connected by an optical fiber 401.

[0137] Communication device 200c has the configuration shown in Figure 10 and has three nodes, Nodes 201-1 to 201-3. Substation 21 has the configuration shown in Figure 2A. Communication device 200a has the configuration shown in Figure 4 and has two nodes, Nodes 201-1 and Node 201-2. Communication device 200i has four nodes 201i, Nodes 201i-1 to 200i-4.

[0138] In the system shown in Figure 18, the communication device 200c acts as a base station and is initially installed in the sea and begins operation. The communication device 200c and the master station 11 are connected by an optical fiber 401, and an example of communication via the optical fiber 401 is shown, but as explained with reference to Figure 1, the system may also be configured to communicate wirelessly.

[0139] The slave station 21 and the communication device 200a are installed underwater with the base station communication device 200c already in place, and begin operation after establishing a link with the communication partner that offers the best communication quality. The arrows shown in Figure 18 represent the uplink direction. A link is established in which the communication device 200a transmits to the slave station 21, and the slave station 21 transmits to the communication device 200c.

[0140] The following describes the process that occurs when the communication device 200i is installed, given that such a link has already been established. When the communication device 200i is installed underwater, it performs the process of establishing a link with other communication devices.

[0141] The process for establishing a link by the communication device 200i is described below. Link establishment is performed by node 201i, which is designated as the master. The communication device 200i comprises nodes 201i-1, 201i-2, 201i-3, and 201i-4. Of these, node 201i-1 is set as the master, and nodes 201i-2, 201i-3, and 201i-4 ​​are set as slaves. The master and slave configurations are set at the time of installation, for example, by a mechanical switch.

[0142] If the communication partner is already in operation, the node 201i-1, which is set as the master, maintains a receive mode state, is installed in a fixed position underwater, and remains in a standby state until it receives a transmission signal from the communication partner, such as a SYN signal. Upon receiving a transmission signal from the communication partner, a link is established based on a link establishment sequence, such as a 3-way handshake.

[0143] The communication device 200i may be installed underwater when the communication partner has not yet been installed, and it may also function as a base station itself. The process related to establishing a link in such cases will be described. Node 201i-1, which is set as the master of the communication device 200i, is connected to land, sea, and satellite communication devices by wire or wireless and is in a state where it can be remotely controlled.

[0144] After power is turned on, node 201i-1 is set to receive mode and, after being installed in a fixed position underwater, remotely initiates link establishment processing based on a link establishment sequence, such as a 3-way handshake. Specifically, it begins periodically transmitting a transmission signal, such as a SYN signal. If a request is received from another communication device that has received this transmitted signal, node 201i-1 establishes a link with that communication device.

[0145] Figure 18 shows the case where a link is established between communication device 200i and communication device 200a. The established link shown in Figure 18 represents a situation where the route is established as follows: communication device 200i → communication device 200a → slave station 21 → communication device 200c. Underwater, the relative positions of each communication device may change, and the strength of transmission and reception may also change. A mechanism may be provided to detect changes in transmission and reception strength or to periodically review the communication route. As a result, a mechanism may be provided to operate the network in a way that ensures it is always optimal, such as changing the route to communication device 200a → communication device 200i → communication device 200c.

[0146] The following describes the processes performed by node 201i-1, which is set as the master. When node 201i-1 is powered on, the RF switches (switches 211, 212) are switched to the RF transceiver unit 254 (power supply point 213) side. Node 201i-1 communicates with other nodes 201i, for example, using the inter-node communication unit 255, and obtains information about connected slaves. In this case, information is obtained that nodes 201i-2, 201i-3, and 201i-4 ​​are connected.

[0147] As described above, a link is established with other communication devices that will be the communication partners. Once the link is established, node 201i-1 notifies each of the nodes 201i-2 through 201i-4, which are set as slaves, of the information of the communication partner with which the link has been established, via communication using the inter-node communication unit 255. When this notification is made, the switching order of the RF switch, in other words, the order in which to communicate with the communication partner, is also notified to each of the nodes 201i-2 through 201i-4, which are set as slaves.

[0148] To ensure that the timing of communication between nodes 201i-1 to 201i-4 ​​and their respective communication partners does not overlap, and that the radiating process is carried out sequentially, the master sets the communication order for the slaves and notifies the slaves of the set communication order (switching timing of switches 211 and 212).

[0149] Node 201i-1, which is set as the master, switches the RF switch to the power supply point 213 side and communicates with the communication partner when it is its turn to communicate, according to the order of communications it has notified.

[0150] This section describes the processes performed by each of the nodes 201i-2 through 201i-4, which are configured as slaves. Here, we will use the processes performed by node 201i-2 as an example. When node 201i-2 is powered on, the RF switches (switches 211, 212) are switched to the path side that does not include the RF transceiver 254 (power supply point 213), that is, the path side that includes the wiring 214.

[0151] When node 201i-2 receives a query from node 201i-1, which is set as the master, it notifies node 201i-1 of its own information. This notification is performed using the inter-node communication unit 255. Node 201i-2 obtains information about the communication partner and the order of communication from node 201i-1, which is set as the master.

[0152] Node 201i-2, which is configured as a slave, switches the RF switch to the power supply point 213 side and communicates when it is its turn to communicate, according to the communication order notified by Node 201i-2, which is configured as a master.

[0153] For example, if the master fails, a mechanism could be implemented to automatically reconfigure one of the slave nodes 201 as the master. Alternatively, a sequence for becoming the master could be pre-assigned to the slaves, and when a master failure is detected, the slaves could be configured to become the master in that sequence.

[0154] According to this technology, multiple nodes 201 are connected either directly or via an insulated cable 203, and the antenna aperture is shared among multiple nodes 201, allowing two or more sensors to share a single antenna. Therefore, this technology makes it possible to expand the communication range while suppressing an increase in antenna size. Because the communication range can be expanded, a wide area can be covered with fewer communication devices, making it possible to reduce the cost of the system.

[0155] In this specification, "system" refers to an entire apparatus composed of multiple devices.

[0156] Furthermore, the effects described herein are merely illustrative and not limiting, and other effects may also occur.

[0157] It should be noted that the embodiments of this technology are not limited to those described above, and various modifications are possible without departing from the spirit of this technology.

[0158] Furthermore, this technology can also take the following configurations: (1) A communication device comprising n nodes, each of the n nodes comprising a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, wherein the power supply point and the switch are enclosed in an insulator, the n nodes are connected in a row, and the node located at the end of the n nodes is connected to a metal conductor exposed in a conductive medium. (2) The communication device according to (1), wherein the n nodes are connected via conductive wiring enclosed in an insulator. (3) The communication device according to (1) or (2), wherein the metal conductor is connected to the node via conductive wiring enclosed in an insulator. (4) The communication device according to any one of (1) to (3), wherein the switch is provided at both ends of the power supply point. (5) The communication device according to any one of (1) to (4), wherein the metal conductor is spherical in shape and coated with a corrosion-resistant insulating thin film. (6) The communication device according to any one of (1) to (5), wherein each of the n nodes further comprises a communication unit for communicating with the other nodes. (7) The communication device according to (6), wherein the communication units are connected to each other by optical fiber. (8) The communication device according to (6), wherein the communication unit performs communication using a frequency higher than the operating frequency of the power supply point. (9) The communication device according to (8), wherein the node further comprises an HPF (HIGH Pass Filter) connected to the communication unit. (10) The communication device according to any one of (6) to (9), wherein the communication unit is another communication device installed in the conductive medium and exchanges information with the other communication device with which a link has been established. (11) The communication device according to any one of (1) to (10), wherein if the switch included in one of the n nodes is connected to the path side including the power supply point, the other nodes are connected to the path side not including the power supply point.(12) The communication device according to any one of (1) to (11), wherein one of the n nodes is set as a master and the other nodes are set as slaves, and the switch of the node set as the master is connected to the path side including the power supply point after power is turned on until a link is established with another communication device installed in the conductive medium, and the switch of the node set as a slave is connected to the path side not including the power supply point after power is turned on until a link is established with the other communication device. (13) The communication device according to (1), wherein n is 1 and the switch is connected to a path not including the power supply point, and functions as a passive repeater. (14) A communication device comprising n nodes, each of the n nodes comprising a communication unit for communicating with the other nodes and a sensor, one of the n nodes further comprising a power supply point, the n nodes being connected in a row, the node located at the end of the n nodes being connected to a metal conductor exposed in a conductive medium, the communication unit transmitting information acquired by the sensor to the node comprising the power supply point, and the node comprising the power supply point transmitting the information to other communication devices. (15) The communication device according to (14), wherein the communication unit performs communication using a frequency higher than the operating frequency of the power supply point. (16) The communication device according to (14) or (15), wherein the node further comprises an HPF (HIGH Pass Filter) connected to the communication unit. (17) A communication device comprising a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, wherein the power supply point and the switch are enclosed in an insulator, and terminals are provided at both ends of the insulator for connection to a metal conductor or insulated cable exposed in a conductive medium. (18) The communication device according to (17), wherein the switch is provided at both ends of the power supply point. (19) The communication device according to (17) or (18), wherein n of the communication devices are connected in a line via the insulated cable.

[0159] 1 Communication system, 11 Master station, 12, 13 Communication stations, 14 Satellite, 21, 31 Slave stations, 32 Repeater, 101 Spherical electrode, 111 Wiring, 112 Insulator, 121 Power supply point, 122 Sensor, 131 Wiring, 200 Communication device, 201 Node, 202 Sensor, 203 Insulated cable, 211, 212 Switch, 213 Power supply point, 214 Wiring, 215 Insulator, 221, 222, 223 Connector, 251 Sensing unit, 252 Signal processing unit, 253 High-frequency processing unit, 254 RF Transceiver unit, 255 Inter-node communication unit, 256 Switching unit, 257 Control unit, 302 Optical fiber, 303 Optical terminal, 304 Optical terminal, 321 HPF, 401 Optical fiber

Claims

1. A communication device comprising n nodes, each of the n nodes comprising a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, wherein the power supply point and the switch are enclosed in an insulator, the n nodes are connected in a row, and the node located at the end of the n nodes is connected to a metal conductor exposed in a conductive medium.

2. The communication device according to claim 1, wherein the n nodes are connected via conductive wiring enclosed in an insulator.

3. The communication device according to claim 1, wherein the metal conductor is connected to the node via conductive wiring enclosed in an insulator.

4. The communication device according to claim 1, wherein the switches are provided at both ends of the power supply point.

5. The communication device according to claim 1, wherein the metal conductor is spherical in shape and coated with a corrosion-resistant insulating thin film.

6. The communication device according to claim 1, wherein each of the n nodes further comprises a communication unit for communicating with the other nodes.

7. The communication device according to claim 6, wherein the communication units are connected to each other by optical fiber.

8. The communication device according to claim 6, wherein the communication unit performs communication using a frequency higher than the operating frequency of the power supply point.

9. The communication device according to claim 8, further comprising a High Pass Filter (HPF) connected to the communication unit as the node.

10. The communication unit is another communication device installed in the conductive medium, and the communication device according to claim 6, which exchanges information with the other communication device with which a link has been established.

11. The communication device according to claim 1, wherein if the switch included in one of the n nodes is connected to the path side including the power supply point, the other nodes are connected to the path side not including the power supply point.

12. The communication device according to claim 1, wherein one of the n nodes is set as a master, and the other nodes are set as slaves, the switch of the node set as the master is connected to the path side including the power supply point after power is turned on until a link is established with another communication device installed in the conductive medium, and the switch of the node set as a slave is connected to the path side not including the power supply point after power is turned on until a link is established with the other communication device.

13. The communication device according to claim 1, wherein n is 1, and the switch functions as a passive repeater when connected to a path that does not include the power supply point.

14. A communication device comprising n nodes, each of the n nodes comprising a communication unit for communicating with the other nodes and a sensor, one of the n nodes further comprising a power supply point, the n nodes being connected in a row, the node located at the end of the n nodes being connected to a metal conductor exposed in a conductive medium, the communication unit transmitting information acquired by the sensor to the node comprising the power supply point, and the node comprising the power supply point being a communication device for transmitting the information to other communication devices.

15. The communication device according to claim 14, wherein the communication unit performs communication using a frequency higher than the operating frequency of the power supply point.

16. The communication device according to claim 14, further comprising a High Pass Filter (HPF) connected to the communication unit as the node.

17. A communication device comprising a power supply point and a switch for switching between a path including the power supply point and a path not including the power supply point, wherein the power supply point and the switch are enclosed within an insulator, and terminals are provided at both ends of the insulator for connection to a metal conductor or insulated cable exposed in a conductive medium.

18. The communication device according to claim 17, wherein the switches are provided at both ends of the power supply point.

19. The communication device according to claim 17, wherein n communication devices are connected in a row via the insulating cable.

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