Communication device and communication method

Abstract

This communication device for underwater visible light communication with a target communication device includes: a visible light communication unit for transmitting and receiving a visible light signal containing communication data; a sound wave communication unit for receiving a sound wave signal transmitted from a target communication device or another communication device and containing information used to control establishment of visible light communication connection; and a control unit for performing control for establishing visible light communication connection with the target communication device on the basis of the information contained in the received sound wave signal.

Description

[Technical Field]

[0001] The present disclosure relates to a communication device and a communication method for underwater visible light communication. [Background technology]

[0002] Visible light is a well-known transmission medium for underwater communications. However, because visible light has strong directionality, conventional visible light communications typically involve communication between a transmitter and a receiver facing each other, assuming that the transmitter and receiver are fixed.

[0003] In visible light communication, when at least one of the transmitter and receiver is mobile, each communication device on the transmitter and receiver must point the visible light communication direction (e.g., the optical axis direction), which is the direction in which the visible light signal is transmitted, toward the other party. While it is possible to determine the direction of the other party using radio waves on land or in space, radio waves are significantly attenuated underwater, making it difficult to use radio waves to determine the direction of the other party in underwater visible light communication.

[0004] Patent Document 1 describes an underwater laser communication device with a sonar device. This communication device receives elevation and depression angle and azimuth information about the communication target from the sonar device and controls a servo motor to point the laser optical system in that direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-103232 Summary of the Invention

[0006] A communication device according to a first aspect is a device that performs underwater visible light communication with a target communication device, and includes: a visible light communication unit that transmits and receives visible light signals containing communication data; a sonic communication unit that receives sonic signals that are transmitted from the target communication device or another communication device and contain information used to control the establishment of a visible light communication connection; and a control unit that performs control to establish the visible light communication connection with the target communication device based on the information contained in the received sonic signals.

[0007] A communication method according to a second aspect is a method used in a communication device that performs underwater visible light communication with a target communication device, and includes the steps of receiving a sound signal transmitted from the target communication device or another communication device and including information used to control establishment of a visible light communication connection, performing control for establishing the visible light communication connection with the target communication device based on the information included in the received sound signal, and transmitting and receiving a visible light signal including communication data. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a communication device according to an embodiment. [Figure 2] 1 is a diagram illustrating an application example of a communication device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of an operation scenario of the communication device according to the first embodiment. [Figure 4] 4 is a diagram showing the contents (format) of sound wave signals transmitted and received in an example of an operation scenario according to the first embodiment. FIG. [Figure 5] FIG. 3 is a diagram illustrating an example of an operation flow of the communication device according to the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of an operation scenario of a communication device according to a first modification of the first embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of an operation flow of a communication device according to a first modification of the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of an operation scenario of a communication device according to a second modification of the first embodiment. [Figure 9]FIG. 10 is a diagram showing the contents (format) of sound wave signals transmitted and received in an example of an operation scenario according to a second modified example of the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of an operation flow of a communication device according to a second modification of the first embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of an operation scenario of a communication device according to a second modification of the first embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of an operation flow of a communication device according to a third modified example of the first embodiment. [Figure 13] FIG. 10 is a diagram illustrating an example of an operation scenario of a communication device according to the second embodiment. [Figure 14] FIG. 10 is a diagram showing the contents (format) of sound wave signals transmitted and received in an example of an operation scenario according to the second embodiment. [Figure 15] FIG. 10 is a diagram illustrating an example of an operation flow of a communication device according to the second embodiment. [Figure 16] FIG. 11 is a diagram showing an example of the content (format) of an alarm sound signal according to the third embodiment. [Figure 17] FIG. 11 is a diagram illustrating an example of an operation scenario of a communication device according to a third embodiment. [Figure 18] FIG. 11 is a diagram illustrating an example of an operation scenario of a communication device according to a first modification of the third embodiment. [Figure 19] FIG. 11 is a diagram illustrating an example of an operation scenario of a communication device according to a second modification of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Compared to visible light, sound waves have a longer communication distance underwater (i.e., they are less attenuated underwater), and are less directional than visible light, making them suitable as a transmission medium for determining the direction of a communication partner. By using a sonar device such as the communication device described in Patent Document 1, it is possible to detect an object by emitting sound waves and capturing the reflected waves.

[0010] However, because it is not possible to determine whether an object detected using a sonar device is a visible light communication device, unnecessary control of the visible light communication direction may occur. Furthermore, even if an object detected using a sonar device is a visible light communication device, if the visible light communication direction of the communication partner is not directed toward the device, a visible light communication connection cannot be established. Therefore, conventional technologies have room for improvement in terms of facilitating the establishment of a visible light communication connection.

[0011] Therefore, an object of the present disclosure is to facilitate the establishment of a visible light communication connection.

[0012] A communication device according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0013] (1) First embodiment First, a communication device according to a first embodiment will be described. The communication device according to the first embodiment is a device that performs underwater visible light communication with a target communication device (i.e., a communication partner). Such a communication device may be referred to as an underwater communication device or an underwater visible light communication device. Note that, in the following, underwater communication is mainly assumed to be undersea communication, but underwater communication may also be communication in a lake or a river.

[0014] (1.1) Configuration of communication device 1 is a diagram showing the configuration of a communication device 100 according to the first embodiment. The communication device 100 has a visible light communication unit 110, a sound wave communication unit 120, and a control unit .

[0015] The visible light communication unit 110 transmits and receives visible light signals including communication data under the control of the control unit 130. In other words, the visible light communication unit 110 performs data communication with the target communication device through visible light communication. The visible light communication unit 110 includes a light emitting unit 111, a light receiving unit 112, and a driving unit 113.

[0016] The light-emitting unit 111 includes at least one light-emitting element. The light-emitting element may be a laser diode (LD) or a light-emitting diode (LED). The light-emitting unit 111 converts an electrical signal (transmission signal) output by the control unit 130 for visible light communication into a visible light signal, and transmits the visible light signal to the target communication device. The light-emitting unit 111 may include multiple light-emitting elements arranged facing in various directions so that the visible light signal can be transmitted in various directions (for example, in all directions of 360 degrees).

[0017] In the following, we will mainly assume that the light-emitting element is an LD and that underwater laser communication is used as underwater visible light communication. Note that the communication distance when using an LED is approximately several tens of meters, while the communication distance when using an LD is approximately 200 meters. However, since visible light is highly directional, highly accurate optical axis alignment technology is required. Furthermore, visible light communication allows for faster communication speeds than acoustic wave communication, and can be made smaller and consume less power than acoustic wave communication.

[0018] The light receiving unit 112 includes at least one light receiving element. The light receiving unit 112 receives a visible light signal from the target communication device, converts the received visible light signal into an electrical signal (received signal), and outputs the received signal to the control unit 130. The light receiving unit 112 may include multiple light receiving elements arranged facing in various directions so that it can receive visible light signals from various directions (for example, all directions of 360 degrees).

[0019] Under the control of the control unit 130, the driving unit 113 drives the light-emitting unit 111 so as to vary the visible light communication direction (e.g., the optical axis direction) in which the visible light communication unit 110 (specifically, the light-emitting unit 111) transmits a visible light signal. The driving unit 113 may include an actuator for changing the orientation of the light-emitting unit 111. The driving unit 113 may include an actuator for changing the orientation of the light-receiving unit 112. The actuator may change the orientation of the set of the light-emitting unit 111 and the light-receiving unit 112. The driving unit 113 may include a driving circuit for selectively driving some light-emitting elements corresponding to a specific direction from among a plurality of light-emitting elements arranged in various directions.

[0020] The ultrasonic communication unit 120 transmits and receives ultrasonic signals including information used to control the establishment of a visible light communication connection under the control of the control unit 130. In other words, the ultrasonic communication unit 120 performs communication for controlling the establishment of a visible light communication connection by ultrasonic communication. The ultrasonic communication unit 120 includes a wave transmitting unit 121 and a wave receiving unit 122.

[0021] The wave transmitting unit 121 includes at least one wave transmitter. The wave transmitting unit 121 converts an electrical signal (transmission signal) output by the control unit 130 for acoustic communication into an acoustic signal, and transmits the acoustic signal. The wave receiving unit 122 includes at least one wave receiver. The wave receiving unit 122 receives the acoustic signal, converts the received acoustic signal into an electrical signal (received signal), and outputs the received signal to the control unit 130.

[0022] Sound waves (sound signals) are more effective for communication underwater than visible light. Noden It has a long transmission distance, meaning that there is little attenuation in water, but the communication speed is much slower than visible light communication. Sound waves (sound wave signals) have weaker directionality than visible light (visible light signals), and do not require the high-precision optical axis alignment required for visible light communication. In other words, sound wave communication can communicate over a wider range than visible light communication. However, sound wave communication consumes more power than visible light communication.

[0023] The control unit 130 controls the overall operation of the communication device 100. For example, the control unit 130 controls the visible light communication unit 110 and the acoustic wave communication unit 120. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a digital signal processor and a CPU (Central Processing Unit). The digital signal processor performs modulation / demodulation and encoding / decoding of digital signals. The CPU executes programs stored in the memory to perform various processes.

[0024] In the communication device 100 configured in this manner, the sonic communication unit 120 (receiving unit 122) receives a sonic signal that is transmitted from the target communication device or another communication device and includes information used to control the establishment of a visible light communication connection. The control unit 130 performs control to establish a visible light communication connection with the target communication device based on the information included in the sonic signal received by the sonic communication unit 120. This enables more advanced control than when a sonar device is used, and can facilitate the establishment of a visible light communication connection.

[0025] The sonic communication unit 120 (receiving unit 122) may receive a sonic signal including an identifier of the target communication device. This allows the control unit 130 to identify the target communication device based on the identifier included in the received sonic signal. The sonic communication unit 120 (transmitting unit 121) may transmit a sonic signal including the identifier of the communication device 100. This allows another communication device that receives the sonic signal to identify the communication device 100 based on the identifier included in the received sonic signal.

[0026] In the first embodiment, the control unit 130 acquires the position of the target communication device through acoustic communication using the acoustic communication unit 120. Based on the position of the target communication device and the position of the communication device 100 (i.e., its own position), the control unit 130 controls the visible light communication unit 110 (e.g., the drive unit 113) so that the visible light communication direction is directed toward the target communication device. This makes it possible to appropriately direct the visible light communication direction (e.g., the optical axis direction) toward the target communication device. Note that the "position" may be a three-dimensional position, for example, a position on a reference point coordinate system. Alternatively, the "position" may be an absolute position consisting of latitude, longitude, and altitude.

[0027] In the first embodiment, the ultrasonic communication unit 120 (receiving unit 122) receives an ultrasonic signal including location information indicating the location of the target communication device. The control unit 130 acquires the location of the target communication device based on the location information included in the received ultrasonic signal. This allows the control unit 130 to appropriately acquire the location of the target communication device. Also, in the first embodiment, the ultrasonic communication unit 120 (receiving unit 122) receives an ultrasonic signal including location information indicating the location of the target communication device from the target communication device. This allows the control unit 130 to acquire the location of the target communication device directly from the target communication device.

[0028] As a method of acquiring the position of communication device 100 (i.e., its own position), if communication device 100 is fixed to, for example, the seabed, an undersea structure, or a buoy, control unit 130 may store its own position in advance. Alternatively, assuming that communication device 100 is capable of receiving satellite signals from positioning satellites, communication device 100 may have a GNSS (Global Navigation Satellite System) receiver, and control unit 130 may acquire its own position using GNSS positioning. These methods of acquiring its own position are suitable as methods of acquiring the own position of communication device 100 operating as a base station device.

[0029] On the other hand, assuming that the communication device 100 is mobile but cannot receive satellite signals from positioning satellites, the control unit 130 may acquire its own location using acoustic communication. This method of acquiring its own location is suitable as a method of acquiring its own location for the communication device 100 operating as a terminal device. For example, the acoustic communication unit 120 may transmit a first acoustic signal (hereinafter referred to as a "query acoustic signal") and then receive a second acoustic signal (hereinafter referred to as a "response acoustic signal") from each base station device that received the query acoustic signal. The control unit 130 acquires the location (own location) of the terminal device based on the round-trip propagation time to each base station device determined in response to the reception of the response acoustic signal. Specifically, the control unit 130 can acquire the distance between the terminal device and each base station device from the sound propagation speed (average speed of sound) in water and the round-trip propagation time. When the control unit 130 acquires the distances to three or more base stations, it can acquire its own location on a reference coordinate system with each base station device as the reference point. Such a self-location acquisition method is sometimes called an LBL (Long Base Line) method or an SBL (Short Base Line) method. In the first embodiment, the LBL is mainly assumed as the self-location acquisition method.

[0030] The ultrasonic communication unit 120 (transmitting unit 121) transmits to the target communication device an ultrasonic signal including location information indicating the location (self-location) of the communication device 100. This allows the target communication device to obtain the location of the communication device 100 directly from the communication device 100.

[0031] The control unit 130 acquires the distance between the target communication device and the communication device 100 based on the positions of the target communication device and the communication device 100. The control unit 130 may control the initial transmission power of the visible light signal in visible light communication based on the acquired distance. This allows the control unit 130 to appropriately control and set the initial transmission power of the visible light signal in visible light communication.

[0032] When there are multiple candidates for the target communication device (hereinafter referred to as "candidate communication devices"), the sonic communication unit 120 (receiving unit 122) may receive a sonic signal including location information from each candidate communication device. In this case, the control unit 130 may acquire the distance to each candidate communication device based on the location of each candidate communication device and the location of the communication device 100. The control unit 130 may select a target communication device from these candidate communication devices based on the acquired distances. For example, the control unit 130 may select a candidate communication device that is closest to the communication device 100 as the target communication device, giving priority to the other candidate communication devices. This allows the control unit 130 to appropriately select a target communication device from among the multiple candidate communication devices.

[0033] The ultrasonic communication unit 120 may transmit and / or receive a connection ultrasonic signal for establishing a visible light communication connection to and from the target communication device. After the visible light communication connection is established, the control unit 130 controls the visible light communication unit 110 to perform underwater visible light communication with the target communication device. This explicitly establishes the visible light communication connection, making it possible to properly start visible light communication.

[0034] (1.2) Examples of communication device applications FIG. 2 is a diagram showing an application example of the communication device 100 according to the first embodiment. Here, it is assumed that underwater communication is performed between a terminal device and a base station device. However, it may also be assumed that underwater communication is performed between terminal devices. Alternatively, it may be assumed that underwater communication is performed between base station devices. When underwater communication is performed between terminal devices, both of the pair of communication devices (the own communication device and the target communication device) performing underwater visible light communication are terminal devices. When underwater communication is performed between base station devices, both of the pair of communication devices (the own communication device and the target communication device) performing underwater visible light communication are base station devices.

[0035] 2, one communication device 100 performing underwater visible light communication is a terminal device 100a, and the other communication device 100 performing underwater visible light communication is a base station device 100b. From the viewpoint of the terminal device 100a, the base station device 100b is the target communication device, and from the viewpoint of the base station device 100b, the terminal device 100a is the target communication device.

[0036] The base station device 100b includes a backhaul communication unit 140. The backhaul communication unit 140 communicates with the network side (for example, on land or on a ship) via wired communication, radio wave communication, or visible light communication under the control of the control unit 130b. The backhaul communication unit 140 may be capable of inter-base station communication with other surrounding base station devices.

[0037] The base station device 100b may include a GNSS positioning unit 150 that acquires the position (self-location) of the base station device 100b by GNSS positioning. The GNSS positioning unit 150 may include at least one GNSS receiver from, for example, the Global Positioning System (GPS), the Global Navigation Satellite System (GLONASS), the Indian Regional Navigational Satellite System (IRNSS), COMPASS, and Galileo. However, if the base station device 100b is fixed, the control unit 130b may store the position (self-location) of the base station device 100b in advance. In this case, the base station device 100b does not need to include the GNSS positioning unit 150.

[0038] The visible light communication unit 110a of the terminal device 100a and the visible light communication unit 110b of the base station device 100b perform visible light communication (specifically, underwater visible light communication) to transmit and receive visible light signals, while the acoustic wave communication unit 120a of the terminal device 100a and the acoustic wave communication unit 120b of the base station device 100b perform acoustic wave communication (specifically, underwater acoustic wave communication) to transmit and receive acoustic signals.

[0039] In the base station device 100b, the ultrasonic communication unit 120b (receiving unit 122b) receives an ultrasonic signal transmitted from the terminal device 100a (transmitting unit 121a) and including information used to control the establishment of a visible light communication connection. The control unit 130b performs control to establish a visible light communication connection with the terminal device 100a based on the information included in the ultrasonic signal received by the ultrasonic communication unit 120b. For example, the control unit 130b acquires the position of the terminal device 100a through ultrasonic communication using the ultrasonic communication unit 120b. Based on the positions of the terminal device 100a and the position of the base station device 100b (i.e., its own position), the control unit 130b controls the visible light communication unit 110b (for example, the driving unit 113b) so that the visible light communication direction is oriented toward the terminal device 100a.

[0040] In the base station device 100b, the ultrasonic communication unit 120b (transmitter 121b) may transmit an ultrasonic signal including a base station ID to the terminal device 100a. The ultrasonic communication unit 120b (receiver 122b) may receive an ultrasonic signal including a terminal ID from the terminal device 100a.

[0041] In the base station device 100b, the ultrasonic communication unit 120b (transmitter 121b) may transmit an ultrasonic signal including base station location information indicating the location of the base station device to the terminal device 100a. The ultrasonic communication unit 120b (receiver 122b) may receive an ultrasonic signal including terminal location information indicating the location of the terminal device 100a from the terminal device 100a.

[0042] In the base station device 100b, the sonic communication unit 120b may transmit to and / or receive from the terminal device 100a a connection sonic signal for establishing a visible light communication connection. For example, the sonic communication unit 120b may receive a connection request sonic signal from the terminal device 100a and transmit to the terminal device 100a an acknowledgement response sonic signal (hereinafter referred to as an "ACK sonic signal") indicating acceptance of the connection request.

[0043] In the base station device 100b, the control unit 130b may acquire the distance between the terminal device 100a and the base station device 100b based on the positions of the terminal device 100a and the base station device 100b (its own position). The control unit 130b may control the initial transmission power of the visible light signal in visible light communication based on the acquired distance.

[0044] Meanwhile, in the terminal device 100a, the ultrasonic communication unit 120a (receiving unit 122a) receives an ultrasonic signal transmitted from the base station device 100b (transmitting unit 121b) and including information used to control the establishment of a visible light communication connection. The control unit 130a performs control to establish a visible light communication connection with the base station device 100b based on the information included in the ultrasonic signal received by the ultrasonic communication unit 120a. For example, the control unit 130a acquires the position of the base station device 100b through ultrasonic communication using the ultrasonic communication unit 120a. Based on the position of the base station device 100b and the position of the terminal device 100a (i.e., its own position), the control unit 130a controls the visible light communication unit 110a (for example, the driving unit 113a) so that the visible light communication direction is oriented toward the base station device 100b.

[0045] In the terminal device 100a, the ultrasonic communication unit 120a (transmitting unit 121a) may transmit an ultrasonic signal including an identifier of the terminal device 100a (hereinafter referred to as a "terminal ID") to the base station device 100b. The ultrasonic communication unit 120a (receiving unit 122a) may receive an ultrasonic signal including an identifier of the base station device 100b (hereinafter referred to as a "base station ID") from the base station device 100b.

[0046] In the terminal device 100a, the ultrasonic communication unit 120a (transmitter 121a) may transmit an ultrasonic signal including terminal location information indicating the location of the terminal device 100a to the base station device 100b. The ultrasonic communication unit 120a (receiver 122a) may receive an ultrasonic signal including base station location information indicating the location of the base station device 100b from the base station device 100b.

[0047] In the terminal device 100a, the sonic communication unit 120a may transmit to and / or receive from the base station device 100b a connection sonic signal for establishing a visible light communication connection. For example, the sonic communication unit 120a may transmit a connection request sonic signal to the base station device 100b and receive an ACK sonic signal from the base station device 100b.

[0048] In the terminal device 100a, the control unit 130a may acquire the distance between the terminal device 100a and the base station device 100b based on the position (self-position) of the terminal device 100a and the position of the base station device 100b. The control unit 130a may control the initial transmission power of the visible light signal in visible light communication based on the acquired distance.

[0049] The terminal device 100a may perform underwater visible light communication with a base station device 100b selected from a plurality of base station devices 100b (i.e., a plurality of candidate communication devices) as a target communication device. The control unit 130a may perform control to select a target communication device from the plurality of base station devices 100b based on information included in the acoustic signal received by the acoustic communication unit 120a. This makes it possible to perform underwater visible light communication with the most suitable target communication device among the plurality of base station devices 100b.

[0050] In the terminal device 100a, the control unit 130a may acquire the distance between the terminal device 100a and each base station device 100b based on the acoustic signal received by the acoustic communication unit 120a. The control unit 130a may select a target communication device from among the multiple base station devices 100b based on the distance acquired for each base station device 100b. For example, the control unit 130a may preferentially select the base station device 100b that is closest to the terminal device 100a as the target communication device.

[0051] In the base station device 100b, the ultrasonic communication unit 120b may transmit an ultrasonic signal including accommodation capability information indicating whether the base station device 100b can accommodate the terminal device 100a. For example, if the base station device 100b is capable of visible light communication with only one terminal device 100a at a given time and the base station device 100b is currently performing visible light communication with the terminal device 100a, the ultrasonic communication unit 120b transmits an ultrasonic signal including accommodation capability information indicating that the base station device 100b cannot newly accommodate the terminal device 100a.

[0052] In the terminal device 100a, the ultrasonic communication unit 120a receives an ultrasonic signal including accommodation capability information from the base station device 100b. The control unit 130a may select a target communication device from among the multiple base station devices 100b based on the accommodation capability information included in the received ultrasonic signal. Specifically, the control unit 130a extracts, from among the multiple base station devices 100b, a base station device 100b that can newly accommodate the terminal device 100a, and selects a target communication device from the extracted base station device 100b.

[0053] (1.3) Example of communication device operation Fig. 3 is a diagram showing an example of an operation scenario of the communication device 100 according to the first embodiment. Fig. 4 is a diagram showing the contents (format) of sound wave signals transmitted and received in this example of the operation scenario.

[0054] In the example operation scenario according to the first embodiment, it is assumed that the LBL reference point exists within each base station device 100b, that is, each base station device 100b has a function as a transponder in the LBL.

[0055] In this example operation scenario, three base station devices 100b (100b1, 100b2, 100b3) are on the water surface, and each base station device 100b is fixed to a buoy, for example. In each base station device 100b, the visible light communication unit 110b and the ultrasonic communication unit 120b are underwater (below the water surface), and the GNSS positioning unit 150 and the backhaul communication unit 140 are on the water surface (above the water surface). The terminal device 100a is underwater.

[0056] First, the terminal device 100a transmits and receives positioning sound wave signals in the LBL to and from each base station device 100b. Specifically, the terminal device 100a transmits a query sound wave signal to each base station device 100b and receives a response sound wave signal from each base station device 100b, thereby acquiring the round-trip propagation time to and from each base station device 100b. The terminal device 100a then acquires its own location based on the acquired round-trip propagation time.

[0057] Second, the terminal device 100a receives a broadcast sound signal from each base station device 100b. The broadcast sound signal is a sound signal that is periodically transmitted and includes information about the base station device 100b. The broadcast sound signal is a broadcast message that does not specify a destination of the broadcast sound signal.

[0058] In the first embodiment, the annunciation sound wave signal includes information about the base station device 100b that is the source of the annunciation sound wave signal, as shown in Fig. 4. Specifically, the annunciation sound wave signal includes the base station ID of the base station device 100b that is the source of the annunciation sound wave signal, base station location information of the base station device 100b, and accommodation availability information of the base station device 100b. However, instead of including the accommodation availability information in the annunciation sound wave signal, only the base station device 100b that can accommodate the terminal device 100a may transmit the annunciation sound wave signal.

[0059] The terminal device 100a receives the sound wave broadcast signals from each base station device 100b to acquire the position of each base station device 100b.

[0060] Third, the terminal device 100a selects the base station device 100b as a target communication device and transmits and receives a connection sound wave signal to and from the base station device 100b (target communication device). For example, the terminal device 100a transmits a connection request sound wave signal to the base station device 100b (target communication device) and receives an ACK sound wave signal from the base station device 100b (target communication device).

[0061] In the first embodiment, the connection request sonic signal includes the base station ID of the base station device 100b selected by the terminal device 100a (i.e., the destination of the connection request sonic signal), the terminal ID of the terminal device 100a (i.e., the sender of the connection request sonic signal), and the terminal location information of the terminal device 100a, as shown in Fig. 4. The ACK sonic signal includes the base station ID of the base station device 100b that is the sender of the ACK sonic signal, and the terminal ID of the terminal device 100a that is the destination of the ACK sonic signal, as shown in Fig. 4.

[0062] The base station device 100b (target communication device) receives the connection request sound wave signal and thereby acquires the location of the terminal device 100a.

[0063] Fourth, the terminal device 100a controls the visible light communication unit 110a based on the position of the base station device 100b (target communication device) and the position of the terminal device 100a (its own position) so that the visible light communication direction is directed toward the base station device 100b. Similarly, the base station device 100b controls the visible light communication unit 110b based on the position of the base station device 100b (its own position) and the position of the terminal device 100a so that the visible light communication direction is directed toward the terminal device 100a. As a result, a visible light communication connection is established between the base station device 100b and the terminal device 100a. Once the visible light communication connection is established, the base station device 100b and the terminal device 100a transmit and receive communication data via visible light communication.

[0064] When the base station device 100b receives the connection request sonic signal and rejects the connection request, the base station device 100b sends a negative response instead of an ACK sonic signal. Answer( The base station device 100b may transmit an ACK (NACK) sonic signal to the base station device 100b when the base station device 100b rejects the connection request. Alternatively, if the base station device 100b rejects the connection request, the base station device 100b may not transmit an ACK (NACK) sonic signal. When the terminal device 100a receives a NACK sonic signal or when a predetermined time has elapsed since the transmission of the connection request sonic signal (i.e., when the timeout is deemed to have occurred), the terminal device 100a may select the base station device 100b with the second highest priority and transmit a connection request sonic signal to the selected base station device 100b.

[0065] In the acoustic communication region, the positioning acoustic signal, the broadcast acoustic signal, and the connection acoustic signal may be multiplexed using time division multiplexing (TDM). The positioning acoustic signal, the broadcast acoustic signal, and the connection acoustic signal may be multiplexed using frequency division multiplexing (FDM). Alternatively, the positioning acoustic signal, the broadcast acoustic signal, and the connection acoustic signal may be multiplexed using code division multiplexing (CDM). The broadcast acoustic signal of each base station device 100b may be multiplexed using time division multiplexing. Alternatively, the broadcast acoustic signal may be multiplexed using frequency division multiplexing. Alternatively, the broadcast acoustic signal may be multiplexed using code division multiplexing using an orthogonal code sequence unique to each communication device 100.

[0066] 5 is a diagram showing an example of an operation flow of the communication device 100 according to the first embodiment. In this example of the operation flow, it is assumed that each base station device 100b has acquired its own position in advance.

[0067] In step S101, the terminal device 100a transmits an interrogation sound wave signal to each base station device 100b. The terminal device 100a may transmit the interrogation sound wave signal when a need for data communication arises, for example, when communication data (e.g., sensing data) to be transmitted to the network side is generated in the terminal device 100a.

[0068] In step S102, the base station device 100b3 that has received the interrogation sound wave signal transmits a response sound wave signal to the terminal device 100a. In step S103, the base station device 100b2 that has received the interrogation sound wave signal transmits a response sound wave signal to the terminal device 100a. In step S104, the base station device 100b1 that has received the interrogation sound wave signal transmits a response sound wave signal to the terminal device 100a. In this way, in the first embodiment, each base station device 100b functions as a transponder in the LBL.

[0069] In step S105, the terminal device 100a acquires its own location by LBL based on the results of steps S101 to S104.

[0070] In step S106, the base station device 100b3 transmits a broadcast sound wave signal to the terminal device 100a. In step S107, the base station device 100b2 transmits a broadcast sound wave signal to the terminal device 100a. In step S108, the base station device 100b1 transmits a broadcast sound wave signal to the terminal device 100a. Each base station device 100b may transmit a broadcast sound wave signal triggered by receiving an interrogation sound wave signal from the terminal device 100a. In this case, each base station device 100b may transmit the broadcast sound wave signal only once. Alternatively, each base station device 100b may periodically transmit the broadcast sound wave signal only within a certain period after receiving the interrogation sound wave signal. This allows for lower power consumption than when the broadcast sound wave signal is always transmitted periodically.

[0071] The terminal device 100a receives the sound wave broadcast signals from each base station device 100b to acquire the position of each base station device 100b.

[0072] In step S109, the terminal device 100a selects the base station device 100b as the target communication device (i.e., the connection request destination). Here, the explanation will continue assuming that the terminal device 100a has selected the base station device 100b1 as the target communication device.

[0073] In step S110, the terminal device 100a transmits a connection request sound wave signal to the base station device 100b1. This connection request sound wave signal includes the base station ID of the base station device 100b1 as its destination, and also includes terminal location information of the terminal device 100a.

[0074] In step S111, the base station device 100b1 transmits an ACK sound signal to the terminal device 100a. This ACK sound signal includes the terminal ID of the terminal device 100a as its destination.

[0075] In step S112, the terminal device 100a controls the visible light communication unit 110a so that the visible light communication direction is directed toward the base station device 100b1, based on its own position acquired in step S105 and the position of the base station device 100b1 acquired in step S108.

[0076] In step S113, the base station device 100b1 controls the visible light communication unit 110b so that the visible light communication direction is directed toward the terminal device 100a, based on its own position acquired in advance and the position of the terminal device 100a acquired in step S110.

[0077] In step S114, the base station device 100b1 and the terminal device 100a perform processing to establish a visible light communication connection. Here, the base station device 100b1 and the terminal device 100a each set an initial transmission power of a visible light signal based on the distance between the base station device 100b1 and the terminal device 100a. Once the visible light communication connection is established, the base station device 100b1 and the terminal device 100a transmit and receive communication data via visible light communication.

[0078] (1.4) First Modification of the First Embodiment Next, a communication device 100 according to a first modification of the first embodiment will be described, focusing on differences from the first embodiment. In this modification, the LBL reference point is located outside the base station device 100b. That is, a positioning communication device that serves as the LBL reference point is provided separately from the base station device 100b.

[0079] In this modified example, the sonic communication unit 120 of the communication device 100 transmits interrogation sonic signals to a plurality of positioning communication devices and receives response sonic signals from each of the positioning communication devices that has received the interrogation sonic signals. The control unit 130 of the communication device 100 acquires its own position based on the round-trip propagation time to each of the positioning communication devices 200 that is determined in response to the reception of the response sonic signals.

[0080] FIG. 6 is a diagram showing an example of an operation scenario of the communication device 100 according to the first modification of the first embodiment.

[0081] 6, multiple positioning communication devices 200 are installed underwater. Each positioning communication device 200 has an acoustic wave communication unit and functions as a reference point and a transponder in the LBL. However, some of the multiple positioning communication devices 200 may be integrated with any of the base station devices 100b (see the first embodiment).

[0082] In this modified example, the terminal device 100a transmits and receives positioning sound wave signals in the LBL to and from each positioning communication device 200. Specifically, the terminal device 100a transmits a query sound wave signal to each positioning communication device 200 and receives a response sound wave signal from each positioning communication device 200, thereby obtaining a round-trip propagation time to and from each positioning communication device 200. The terminal device 100a then obtains its own location based on the obtained round-trip propagation time. Note that in this modified example, the base station device 100b may be mobile. The base station device 100b may obtain its own location by transmitting and receiving a positioning sound wave signal to and from each positioning communication device 200.

[0083] 7 is a diagram showing an example of an operation flow of the communication device 100 according to the first modification of the first embodiment. In this example of the operation flow, it is assumed that each base station device 100b has acquired its own position in advance.

[0084] In step S121, the terminal device 100a transmits a query sound wave signal to each positioning communication device 200.

[0085] In step S122, each positioning communication device 200 that has received the interrogation sound wave signal transmits a response sound wave signal to the terminal device 100a.

[0086] In step S123, the terminal device 100a acquires its own location by LBL based on the results of steps S121 and S122.

[0087] The subsequent operations are the same as those in the first embodiment.

[0088] (1.5) Second Modification of the First Embodiment Next, a communication device 100 according to a second modification of the first embodiment will be described, focusing on differences from the first embodiment. In this modification, a location management communication device is provided that manages the location of each communication device 100. The ultrasonic communication unit 120 of the communication device 100 receives an ultrasonic signal including location information indicating the location of the target communication device from the location management communication device.

[0089] Fig. 8 is a diagram showing an example of an operation scenario of the communication device 100 according to the second modification of the first embodiment. Fig. 9 is a diagram showing the contents (format) of sound wave signals transmitted and received in this example of the operation scenario.

[0090] 8, multiple positioning communication devices 200 and a location management communication device 300 are installed underwater. The positioning communication device 200 is the same as that in the first modified example described above. The location management communication device 300 has an acoustic wave communication unit and performs acoustic wave communication with the terminal device 100a and the base station device 100b.

[0091] First, similarly to the first modification example described above, the terminal device 100a acquires its own location using the positioning communication device 200. The base station device 100b may also acquire its own location using the positioning communication device 200. Therefore, the base station device 100b may be mobile.

[0092] Second, the terminal device 100a transmits a registration sound wave signal including terminal location information to the location management communication device 300. For example, the registration sound wave signal from the terminal device 100a includes the terminal ID of the terminal device 100a and the terminal location information of the terminal device 100a, as shown in Fig. 9. The registration sound wave signal may further include the ID of the location management communication device 300 as a destination.

[0093] Each base station device 100b may transmit a registration sound wave signal including base station location information to the location management communication device 300. For example, as shown in FIG. 9, the registration sound wave signal from the base station device 100b includes the base station ID of the base station device 100b, the base station location information of the base station device 100b, and the accommodation availability information of the base station device 100b. However, under the assumption that each base station device 100b is fixed, the location management communication device 300 may acquire the location of each base station device 100b in advance. In that case, the location management communication device 300 may not require a registration sound wave signal from the base station device 100b. Alternatively, the base station device 100b may transmit a registration sound wave signal including the base station ID and the accommodation availability information without including the base station location information.

[0094] Third, the location management communication device 300 transmits a sound wave broadcast signal including location information of each communication device 100 based on information of each communication device 100 that it manages. For example, as shown in Fig. 9, the sound wave broadcast signal according to this modification includes the base station ID, base station location information, and accommodation availability information of each base station device 100b, and the terminal ID and terminal location information of the terminal device 100a.

[0095] The terminal device 100a acquires the location of each base station device 100b (and whether the base station device 100b can accommodate the terminal) by receiving the annunciation sound wave signal from the location management communication device 300. Each base station device 100b acquires the location of the terminal device 100a by receiving the annunciation sound wave signal from the location management communication device 300. Therefore, in this modified example, the connection request sound wave signal transmitted by the terminal device 100a does not need to include terminal location information of the terminal device 100a.

[0096] In this modified example, in the sound wave communication region, the positioning sound signal, the registration sound signal, the notification sound signal, and the connection sound signal may be multiplexed using time division multiplexing (TDM). The positioning sound signal, the registration sound signal, the notification sound signal, and the connection sound signal may be multiplexed using frequency division multiplexing (FDM). Alternatively, the positioning sound signal, the registration sound signal, the notification sound signal, and the connection sound signal may be multiplexed using code division multiplexing (CDM). The registration sound signal of each communication device 100 may be multiplexed using time division multiplexing. Alternatively, the registration sound signal of each communication device 100 may be multiplexed using frequency division multiplexing. Alternatively, the registration sound signal of each communication device 100 may be multiplexed using code division multiplexing using an orthogonal code sequence unique to each communication device 100.

[0097] In this modified example, when the terminal accommodation availability state changes, specifically when it becomes unable to accommodate the terminal device 100a or becomes able to accommodate the terminal device 100a, each base station device 100b may transmit a registration sound wave signal including accommodation availability information indicating the changed terminal accommodation availability state to the location management communication device 300. When it determines that its own location has changed, each base station device 100b may transmit a registration sound wave signal to the location management communication device 300.

[0098] 10 is a diagram showing an example of an operation flow of the communication device 100 according to the second modification of the first embodiment. In this example of the operation flow, it is assumed that each base station device 100b has acquired its own position in advance.

[0099] In step S130, the terminal device 100a acquires its own location in the same manner as in the first modified example described above.

[0100] In step S131, the base station device 100b1 transmits a registration sound wave signal to the location management communication device 300. In step S132, the base station device 100b2 transmits a registration sound wave signal to the location management communication device 300. In step S133, the base station device 100b3 transmits a registration sound wave signal to the location management communication device 300. The location management communication device 300 acquires the location of each base station device 100b and / or whether it can accommodate a terminal, based on the registration sound wave signal from each base station device 100b.

[0101] In step S134, the terminal device 100a transmits a registration sound wave signal to the location management communication device 300. The location management communication device 300 acquires the location of the terminal device 100a based on the registration sound wave signal from the terminal device 100a.

[0102] In step S135, the location management communication device 300 transmits a sound wave broadcast signal. The terminal device 100a receives the sound wave broadcast signal to acquire the location of each base station device 100b. Each base station device 100b receives the sound wave broadcast signal to acquire the location of the terminal device 100a.

[0103] The subsequent operations are the same as those in the first embodiment. However, the connection request sonic signal transmitted from the terminal device 100a to the base station device 100b1 in step S110 may include the identifier of the base station device 100b1 (destination) and the identifier of the terminal device 100a (source) without including the location information of the terminal device 100a.

[0104] (1.6) Third Modification of the First Embodiment Next, a communication device 100 according to a third modification of the first embodiment will be described, focusing on differences from the first embodiment. In this modification, the ultrasonic communication unit 120a of the terminal device 100a receives, as an ultrasonic signal, positioning reference signals transmitted from the base station devices 100b in synchronization with each other. The control unit 130a of the terminal device 100a acquires the position of the terminal device 100a based on the received positioning reference signals.

[0105] FIG. 11 is a diagram showing an example of an operation scenario of the communication device 100 according to the second modification of the first embodiment.

[0106] In this modification, each base station device 100b transmits a positioning reference signal as a sound wave signal in synchronization with each other. As a result, the terminal device 100a can acquire its own position on the reference point coordinate system with each base station device 100b as the reference point based on the arrival time difference of each positioning reference signal. Therefore, there is no need to transmit and receive positioning sound wave signals (interrogation sound wave signals and response sound wave signals) in the LBL system as described above.

[0107] Each base station device 100b may always transmit a positioning reference signal separately from the broadcast sound signal. Each base station device 100b may configure a positioning reference signal using an orthogonal sequence with its own base station ID as a seed. This allows the terminal device 100a to acquire the base station ID based on the positioning reference signal, and therefore associate the positioning reference signal with the broadcast sound signal based on the base station ID.

[0108] In this modification, in the acoustic communication region, the positioning reference signal, the broadcast sound signal, and the connection sound signal may be multiplexed using time division multiplexing (TDM). The positioning sound signal, the registration sound signal, the broadcast sound signal, and the connection sound signal may be multiplexed using frequency division multiplexing (FDM). Alternatively, the positioning sound signal, the registration sound signal, the broadcast sound signal, and the connection sound signal may be multiplexed using code division multiplexing (CDM).

[0109] However, the positioning reference signal may be a common signal for the broadcast sound wave signal, and in this case, each base station device 100b may simultaneously transmit the broadcast sound wave signal using an orthogonal code sequence.

[0110] 12 is a diagram showing an example of an operation flow of the communication device 100 according to the third modification of the first embodiment. In this example of the operation flow, it is assumed that each base station device 100b has acquired its own position in advance.

[0111] In steps S141 to S143, the base station devices 100b1 to 100b3 transmit positioning reference signals as acoustic signals.

[0112] In step S144, the terminal device 100a acquires its own location based on the positioning reference signals received from the base station devices 100b1 to 100b3.

[0113] The subsequent operations are the same as those in the first embodiment.

[0114] (2) Second embodiment Next, the second embodiment will be described, focusing on the differences from the first embodiment. In the first embodiment, the visible light communication direction is controlled by acquiring the position of each communication device 100. In the second embodiment, instead of acquiring the position of each communication device 100, the visible light communication direction is controlled by acquiring the direction of arrival of a sound wave signal from a target communication device.

[0115] In the communication device 100 according to the second embodiment, the ultrasonic communication unit 120 receives an ultrasonic signal transmitted from a target communication device. The control unit 130 estimates the direction of arrival of the ultrasonic signal based on the ultrasonic signal received by the ultrasonic communication unit 120. The control unit 130 then controls the visible light communication unit 110 so that the visible light communication direction (e.g., the optical axis direction) coincides with the direction of arrival. This makes it possible to appropriately orient the visible light communication direction toward the target communication device.

[0116] In the second embodiment, the receiving unit 122 of the ultrasonic communication unit 120 of the communication device 100 includes a receiver array consisting of receivers installed at intervals approximately equal to the wavelength of the ultrasonic waves. The control unit 130 obtains the arrival angle (arrival direction) of the ultrasonic signal as a phase difference between the receivers. A method using this method is also called a USBL (Ultra Short Base Line) method.

[0117] In the second embodiment, the control unit 130 of the communication device 100 may acquire the distance between the target communication device and the communication device 100 based on the amount of attenuation calculated from the transmission power of the sound wave signal in the target communication device and the reception power of the sound wave signal received by the sound wave communication unit 120. Then, the control unit 130 may control the initial transmission power of the visible light signal in visible light communication based on the acquired distance.

[0118] The sonic communication unit 120 of the communication device 100 may receive a sonic signal from each of the plurality of candidate communication devices. The control unit 130 may acquire the distance between each candidate communication device and the communication device 100 based on the amount of attenuation, and select a target communication device from among the plurality of candidate communication devices based on the acquired distance.

[0119] Fig. 13 is a diagram showing an example of an operation scenario of the communication device 100 according to the second embodiment. Fig. 14 is a diagram showing the contents (format) of sound wave signals transmitted and received in this example of the operation scenario.

[0120] In this example operation scenario, the base station device 100b is on the water surface. Specifically, in the base station device 100b, the visible light communication unit 110b and the sonic wave communication unit 120b are underwater (below the water surface), and the backhaul communication unit 140 is above the water surface (above the water surface). The base station device 100b does not need to have the GNSS positioning unit 150. In the second embodiment, the base station device 100b may be mobile because it is configured to control the direction of visible light communication by acquiring the direction of arrival of the sonic wave signal. The terminal device 100a is underwater.

[0121] First, the base station device 100b transmits a broadcast sound signal. In the second embodiment, the broadcast sound signal includes the base station ID of the base station device 100b, accommodation availability information of the base station device 100b, and transmission power information indicating the transmission power of the broadcast sound signal, as shown in Fig. 14. However, if the transmission power of the broadcast sound signal is known (fixed), the broadcast sound signal does not need to include the transmission power information.

[0122] The terminal device 100a receives the broadcast sound signal and acquires the direction of arrival of the broadcast sound signal. The terminal device 100a also acquires the distance between the base station device 100b and the terminal device 100a based on the amount of attenuation calculated from the transmission power of the broadcast sound signal and the received power of the broadcast sound signal.

[0123] The terminal device 100a may receive an annunciation sound wave signal from each of the plurality of base station devices 100b. The terminal device 100a may acquire the distance between each base station device 100b and the terminal device 100a, and may select a target communication device from the plurality of base station devices 100b based on the acquired distance.

[0124] Second, the terminal device 100a transmits and receives a connection sonic signal to and from the base station device 100b (target communication device). For example, the terminal device 100a transmits a connection request sonic signal to the base station device 100b and receives an ACK sonic signal from the base station device 100b.

[0125] In the second embodiment, as shown in Fig. 14, the connection request sonic signal includes the base station ID of the base station device 100b selected by the terminal device 100a (i.e., the destination of the connection request sonic signal), the terminal ID of the terminal device 100a (i.e., the source of the connection request sonic signal), and distance information indicating the distance between the base station device 100b and the terminal device 100a. The distance information is used by the base station device 100b to control the initial transmission power of the visible light signal. As shown in Fig. 14, the ACK sonic signal includes the base station ID of the base station device 100b that is the source of the ACK sonic signal, and the terminal ID of the terminal device 100a that is the destination of the ACK sonic signal.

[0126] Here, the base station device 100b receives a connection request sound wave signal from the terminal device 100a, acquires the direction of arrival of the notification sound wave signal, and acquires the distance between the base station device 100b and the terminal device 100a based on distance information included in the connection request sound wave signal.

[0127] Third, based on the arrival direction estimated for the annunciation sound wave signal, the terminal device 100a controls the visible light communication unit 110a so that the visible light communication direction coincides with the arrival direction. Based on the arrival direction estimated for the connection request sound wave signal, the base station device 100b controls the visible light communication unit 110b so that the visible light communication direction coincides with the arrival direction. As a result, a visible light communication connection is established between the base station device 100b and the terminal device 100a. Once the visible light communication connection is established, the base station device 100b and the terminal device 100a transmit and receive communication data via visible light communication.

[0128] In the acoustic communication region, the broadcast sound signal and the connection sound signal may be multiplexed using time division multiplexing (TDM). The broadcast sound signal and the connection sound signal may be multiplexed using frequency division multiplexing (FDM). Alternatively, the broadcast sound signal and the connection sound signal may be multiplexed using code division multiplexing (CDM). The broadcast sound signal of each base station device 100b may be multiplexed using time division multiplexing. Alternatively, the broadcast sound signal of each base station device 100b may be multiplexed using frequency division multiplexing. Alternatively, the broadcast sound signal of each base station device 100b may be multiplexed using code division multiplexing using an orthogonal code sequence unique to each base station device 100b.

[0129] 15 is a diagram showing an example of an operation flow of the communication device 100 according to the second embodiment. Here, it is assumed that the terminal device 100a receives alarm sound wave signals from three base station devices 100b.

[0130] In step S201, the base station device 100b3 transmits a broadcast sound wave signal to the terminal device 100a. In step S202, the base station device 100b2 transmits a broadcast sound wave signal to the terminal device 100a. In step S203, the base station device 100b1 transmits a broadcast sound wave signal to the terminal device 100a.

[0131] In step S204, the terminal device 100a estimates the direction of arrival of the broadcast sound wave signal from each base station device 100b. The terminal device 100a also acquires (estimates) the distance between the terminal device 100a and each base station device 100b based on the amount of attenuation of the broadcast sound wave signal from each base station device 100b. The terminal device 100a may receive the broadcast sound wave signal from each base station device 100b multiple times and estimate the direction of arrival for each base station device 100b multiple times, thereby performing processing to improve the accuracy of the direction of arrival estimation.

[0132] In step S205, the terminal device 100a selects a base station device 100b to be the target communication device (i.e., connection request destination). The terminal device 100a may preferentially select the base station device 100b that is closest to the terminal device 100a as the target communication device. The terminal device 100a may extract a base station device 100b that can accommodate the terminal device 100a based on the alarm sound wave signals from each base station device 100b, and select the extracted base station device 100b as the target communication device. Here, the explanation will continue assuming that the terminal device 100a has selected the base station device 100b1 as the target communication device.

[0133] In step S206, the terminal device 100a transmits a connection request sound wave signal to the base station device 100b1. This connection request sound wave signal includes the base station ID of the base station device 100b1 as its destination, and also includes distance information indicating the distance between the base station device 100b1 and the terminal device 100a.

[0134] In step S207, the base station device 100b1 receives the connection request sound wave signal and estimates the direction from which the connection request sound wave signal arrives.

[0135] In step S208, the base station device 100b1 transmits an ACK sound wave signal to the terminal device 100a. This ACK sound wave signal includes the terminal ID of the terminal device 100a as its destination. In addition, taking into account the possibility that the base station device 100b1 may move, the terminal device 100a may estimate the arrival direction of the ACK sound wave signal. If the arrival direction of the ACK sound wave signal has changed from the arrival direction estimated in step S204, the terminal device 100a may control the direction of visible light communication using the arrival direction of the ACK sound wave signal.

[0136] In step S209, the terminal device 100a controls the visible light communication unit 110a based on the estimated arrival direction so that the visible light communication direction coincides with the estimated arrival direction.

[0137] In step S210, the base station device 100b1 controls the visible light communication unit 110b based on the arrival direction estimated in step S207 so that the visible light communication direction coincides with the arrival direction.

[0138] In step S211, the base station device 100b1 and the terminal device 100a perform processing to establish a visible light communication connection. Here, the base station device 100b1 and the terminal device 100a each set an initial transmission power of a visible light signal based on the distance between the base station device 100b1 and the terminal device 100a. Once the visible light communication connection is established, the base station device 100b1 and the terminal device 100a transmit and receive communication data via visible light communication.

[0139] In the second embodiment, the control unit 130 of the communication device 100 may calculate an evaluation value indicating the estimation accuracy of the direction of arrival. Then, the control unit 130 may control a movable range (also referred to as a "perturbation range") when adjusting the visible light communication direction (optical axis) in visible light communication based on the calculated evaluation value. The evaluation value indicating the estimation accuracy of the direction of arrival may be, for example, a variance value and a change in direction when direction estimation using acoustic wave communication is performed multiple times. Specifically, when the variance is small, the control unit 130 may determine that the accuracy of narrowing down the direction of arrival is high and narrow the perturbation range. Furthermore, the control unit 130 may estimate the movement direction and speed of the target communication device from the change in direction, and when the movement speed is fast, widen the perturbation range to the movement direction of the target communication device. Furthermore, when the evaluation value indicating the estimation accuracy of the direction of arrival is worse than a threshold, the control unit 130 may re-estimate (repeatedly) the direction of arrival.

[0140] (3) Third embodiment Next, the third embodiment will be described, focusing mainly on the differences from the first and second embodiments described above. In the first and second embodiments described above, the terminal device 100a selects a target communication device (connection request destination) based on the distance to the base station device 100b and / or whether the base station device 100b can accommodate the terminal.

[0141] However, the base station device 100b selected by such a selection method is not necessarily the optimal base station device 100b in terms of the propagation environment in visible light communication. Because the terminal device 100a does not know the optical propagation environment between the selected base station device 100b and the base station device 100b until a visible light communication connection is established with the selected base station device 100b, the optical propagation environment between the terminal device 100a and the base station device 100b may be poor.

[0142] Therefore, in the third embodiment, the terminal device 100a selects the base station device 100b to which the connection request is to be sent, taking into consideration the propagation environment, in addition to or instead of the base station selection methods of the first and second embodiments described above. Note that the third embodiment can be used in combination with the first and second embodiments described above.

[0143] Specifically, in the third embodiment, the acoustic communication unit 120a of the terminal device 100a receives an acoustic signal including propagation environment information indicating a propagation environment that affects underwater visible light communication. The propagation environment information indicates at least one of turbidity and solar noise as the propagation environment. The control unit 130a of the terminal device 100a selects a base station device 100b to which a connection request is to be sent from among multiple base station devices 100b based on the propagation environment information included in the received acoustic signal. This makes it possible to select the most appropriate base station device 100b in terms of the propagation environment in visible light communication. The operations performed after the terminal device 100a selects the base station device 100b to which a connection request is to be sent are the same as those in the first and second embodiments described above.

[0144] FIG. 16 is a diagram illustrating an example of the content (format) of a broadcast sound signal according to the third embodiment. The broadcast sound signal according to the third embodiment includes a base station ID of the base station device 100b, base station location information of the base station device 100b, accommodation availability information of the base station device 100b, and propagation environment information indicating the propagation environment for the base station device 100b. The propagation environment information includes at least one of a value indicating turbidity and a value indicating solar noise. These values ​​may be numerical values ​​corresponding to measured values. Alternatively, these values ​​may be index values ​​such as high, medium, or low. However, when the third embodiment is used in combination with the second embodiment, the broadcast sound signal may include transmission power information indicating the transmission power of the broadcast sound signal instead of the base station location information.

[0145] The terminal device 100a receives annunciation sound wave signals as shown in FIG. 16 for the multiple base station devices 100b, thereby acquiring (estimating) the propagation environment of each base station device 100b, and selects the base station device 100b to which a connection request is to be made based on the acquired propagation environment. The annunciation sound wave signal may be transmitted from the base station device 100b or from the location management communication device 300. In the latter case, each base station device 100b may register its own propagation environment information with the location management communication device 300 using a registration sound wave signal. The annunciation sound wave signal transmitted from the location management communication device 300 may include the propagation environment information of each of the multiple base station devices 100b (see FIG. 9).

[0146] FIG. 17 is a diagram showing an example of an operation scenario of the communication device 100 according to the third embodiment.

[0147] In this example operation scenario, base station devices 100b1 and 100b2 are underwater (specifically, at the bottom of the water), and base station device 100b3 is on the surface of the water. Base station device 100b1 is located closer to the water surface than base station device 100b2. Terminal device 100a is underwater. Here, it is assumed that each base station device 100b has a turbidity sensor and a sunlight noise sensor (for example, an illuminance sensor for measuring ambient light that becomes noise). It is also assumed that each base station device 100b is in a state where it can newly accommodate terminal device 100a. Note that, since anything that emits light, not just sunlight noise, can become noise, any sensor that measures ambient light that becomes noise will suffice, not just a sunlight noise sensor.

[0148] The base station device 100b1 transmits an alarm sound signal including propagation environment information indicating the turbidity and solar noise it has measured itself. The measured turbidity is "medium" and the measured solar noise is "medium". The base station device 100b2 also transmits an alarm sound signal including propagation environment information indicating the turbidity and solar noise it has measured itself. The measured turbidity is "high" and the measured solar noise is "low". The base station device 100b3 also transmits an alarm sound signal including propagation environment information indicating the turbidity and solar noise it has measured itself. The measured turbidity is "low" and the measured solar noise is "high".

[0149] The terminal device 100a, which has received the sound wave alarm signals from each base station device 100b, acquires the propagation environment of each base station device 100b based on the propagation environment information included in each sound wave alarm signal, and selects the base station device 100b to which the connection request is to be made based on the acquired propagation environment. In the example of Fig. 17, the terminal device 100a determines that the base station device 100b2, whose turbidity is "high," and the base station device 100b3, whose solar noise is "high," are inappropriate as connection request destinations, and selects the base station device 100b3 as the connection request destination.

[0150] The terminal device 100a may select the base station device 100b to which the connection request is to be sent based on the distance between each base station device 100b and the terminal device 100a, in addition to the propagation environment of each base station device 100b. The method for acquiring the distance may be a distance acquisition method based on location as in the first embodiment. Alternatively, the method for acquiring the distance may be a distance acquisition method based on attenuation as in the second embodiment.

[0151] For example, if there are two base station devices 100b with the same turbidity and distance but different solar noise, the terminal device 100a may select the base station device 100b with the smaller solar noise of the two base station devices 100b.

[0152] As another example, Condition 1: The distance (A) between the terminal device 100a and the base station device 100b (A) is greater than the distance (B) between the terminal device 100a and the base station device 100b (B), but the difference between the distances (A) and (B) is within a threshold. Condition 2: The terminal device 100a can communicate with the base station device 100b(A) at a maximum transmission power or less. Condition 3: The propagation environment (turbidity and sunlight noise amount) for the base station device 100b(A) is better than the propagation environment (turbidity and sunlight noise amount) for the base station device 100b(B). If all of the above conditions 1 to 3 are met, the terminal device 100a may select the distant base station device 100b(A) rather than the closer base station device 100b(B).

[0153] In the third embodiment, turbidity and sunlight noise have been described as examples of propagation environments that affect underwater visible light communication. However, chlorophyll concentration may also be considered in addition to turbidity and sunlight noise. Furthermore, the terminal device 100a may select the color of visible light to be used for visible light communication based on chlorophyll concentration. This allows the terminal device 100a to select the optimal color.

[0154] In the third embodiment, an example in which each base station device 100b measures the propagation environment has been described, but another communication device, for example, the positioning communication device 200 (see FIG. 6) and / or the location management communication device 300 (see FIG. 8), may also have a turbidity sensor and a sunlight noise sensor. The other communication device may notify the terminal device 100a and / or the base station device 100b of the measured propagation environment by acoustic communication.

[0155] (3.1) First Modification of the Third Embodiment Next, a first modification of the third embodiment will be described, focusing on differences from the third embodiment. In this modification, a recommended base station device 100b to which a connection request is to be made by a terminal device 100a is selected on the network side.

[0156] Specifically, the ultrasonic communication unit 120a of the terminal device 100a receives an ultrasonic signal including recommended base station information indicating at least one base station device 100b selected by the network side, and the control unit 130a of the terminal device 100a selects the base station device 100b to which the connection request is to be sent based on the recommended base station information.

[0157] FIG. 18 is a diagram showing an example of an operation scenario of the communication device 100 according to the first modification of the third embodiment.

[0158] First, each base station device 100b notifies the network node 400 of the measured propagation environment (turbidity and solar noise information). The network node 400 may be a node provided on a communication network. The network node 400 may be a node attached to one of the base station devices 100b. The propagation environment information notified from each base station device 100b to the network node 400 may be a numerical value corresponding to the measured value. The propagation environment information may be an index value such as high, medium, or low. The notification may be made when the turbidity and solar noise measured by each base station device 100b change, or at regular intervals.

[0159] Second, the network node 400 generates or updates an environment information map based on the propagation environment information from each base station device 100b. The environment information map may be map information indicating the correspondence between positions and propagation environments.

[0160] Third, the terminal device 100a notifies the network node 400 of its own location information and a connection request via any base station device 100b within the range where acoustic wave communication is possible.

[0161] Fourth, the network node 400 notifies the terminal device 100a of a base station device 100b that is preferable for the terminal device 100a via the base station device 100b. The base station device 100b notified to the terminal device 100a may be one, or may be a list in order of preference from top to bottom. The base station devices 100b included in the list may be a list that does not take into account whether they can accommodate a terminal, or may be a list that excludes base station devices 100b that cannot accommodate a terminal.

[0162] When using a list that does not take into account whether a terminal can be accommodated, the terminal device 100a determines whether a terminal can be accommodated based on the sound wave broadcast signal from each base station device 100b. When using a list that excludes base station devices 100b that cannot accommodate a terminal, each base station device 100b may notify the network node 400 of a change in the state of whether a terminal can be accommodated (the state after the change) in response to a change. This notification may be made together with the notification of environmental information or independently. Furthermore, each base station device 100b may notify in response to a request from the network node 400.

[0163] (3.2) Second Modification of the Third Embodiment Next, a second modification of the third embodiment will be described, focusing on differences from the third embodiment and its first modification. In this modification, similar to the first modification of the third embodiment, the recommended base station device 100b to which the terminal device 100a will make a connection request is selected on the network side.

[0164] 19 is a diagram showing an example of an operation scenario of the communication device 100 according to a second modification of the third embodiment. In this modification, a large number of fixed optical sensors 500 having an optical communication function are arranged.

[0165] First, each base station device 100b acquires the optical propagation state between itself and a known fixed point (optical sensor 500) by periodically performing visible light communication at an arbitrary timing with the optical sensor 500. The optical propagation state may be information indicating, for example, the amount of attenuation of a visible light signal.

[0166] Here, the base station device 100b in optical communication with the terminal device 100a may request location information from the terminal device 100a at any timing, acquire the location information and optical propagation state of the terminal device 100a, and notify the network node 400 of the acquired information. Alternatively, the terminal device 100a may notify the network node 400 of its own location information and optical propagation state. This notification may be made via visible light communication via the base station device 100b with which it is connected, or via acoustic wave communication via an arbitrary base station device 100b. These notifications may be accompanied by a timestamp indicating the time when the optical propagation state was acquired.

[0167] Second, each base station device 100b notifies the network node 400, which manages the optical propagation state, of the optical propagation state and the corresponding position at any timing.

[0168] Third, the network node 400 generates or updates an optical propagation state map, which may be map information indicating the correspondence between positions and optical propagation states.

[0169] Fourth, the terminal device 100a notifies the network node 400 of its own location information and a connection request via any base station device 100b within the range where acoustic wave communication is possible.

[0170] Fifth, the network node 400 notifies the terminal device 100a of the base station device 100b that is preferable for the terminal device 100a via the base station device 100b.

[0171] (4) Other embodiments In the above-described embodiment, an example in which the terminal device 100a and the base station device 100b perform underwater communication has been mainly described, but it is also possible to assume a case in which underwater communication is performed between base station devices and / or a case in which underwater communication is performed between terminal devices. Also, in the above-described embodiment, an example in which the communication device 100 performs underwater communication has been described, but the communication device 100 may be configured to be capable of communication not only underwater communication but also on land or in space.

[0172] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. Furthermore, the order of the steps in each of the above-described operational flows is merely an example, and the order of the steps may be changed as appropriate.

[0173] A program may be provided that causes a computer to execute each process performed by communication device 100. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by communication device 100 may be integrated, and at least a part of communication device 100 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0174] As used in this disclosure, the terms "based on" and "in response to" do not mean "based only on" or "in response to," unless otherwise specified. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "in response to" means both "in response to" and "in response to." Furthermore, "obtain" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining information by generating the information. The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may also mean including only the listed items or including additional items in addition to the listed items. Furthermore, the term "or" as used in this disclosure is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0175] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0176] This application claims priority from Japanese Patent Application No. 2022-060911 (filed March 31, 2022), the entire contents of which are incorporated herein by reference.

[0177] (Addendum) The following additional notes are about the features of the above-described embodiment.

[0178] (1) A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal. Communication equipment.

[0179] (2) The sonic communication unit receives the sonic signal including the identifier of the target communication device as the information. The communication device according to (1) above.

[0180] (3) a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, The control unit acquiring the position of the target communication device through sound wave communication using the sound wave communication unit; Based on the position of the target communication device and the position of the communication device, the visible light communication unit is controlled so that the visible light communication direction is directed toward the target communication device. The communication device according to (1) or (2) above.

[0181] (4) the sonic wave communication unit receives the sonic signal including location information indicating the location of the target communication device as the information; The control unit acquires the position of the target communication device based on the position information included in the sound wave signal. A communication device according to any one of (1) to (3) above.

[0182] (5) The sonic communication unit receives the sonic signal including the location information from the target communication device. A communication device according to any one of (1) to (4) above.

[0183] (6) The sonic communication unit receives the sonic signal including the location information from a location management communication device different from the target communication device. A communication device according to any one of (1) to (5) above.

[0184] (7) the communication device is a terminal device that performs the underwater visible light communication with a base station device selected from a plurality of base station devices as the target communication device, The control unit further acquires the location of the terminal device through the sonic communication. A communication device according to any one of (1) to (6) above.

[0185] (8) The acoustic wave communication unit Transmitting a first sound signal; receiving a second sound wave signal from each base station device that has received the first sound wave signal; The control unit acquires the position of the terminal device based on a round-trip propagation time to each of the base station devices determined in response to reception of the second sound wave signal. A communication device according to any one of (1) to (7) above.

[0186] (9) The acoustic wave communication unit transmitting a first sound wave signal to a plurality of positioning communication devices different from the base station device; receiving a second sound wave signal from each positioning communication device that has received the first sound wave signal; The control unit acquires the position of the terminal device based on a round-trip propagation time to and from each of the positioning communication devices determined in response to reception of the second sound wave signal. A communication device according to any one of (1) to (8) above.

[0187] (10) the acoustic wave communication unit receives, as the acoustic signal, a positioning reference signal transmitted from each base station device in synchronization between the base station devices; The control unit acquires the position of the terminal device based on the received positioning reference signal. A communication device according to any one of (1) to (9) above.

[0188] (11) The control unit Based on the location of the target communication device and the location of the communication device, subject obtaining a distance between the communication device and the communication device; and controlling an initial transmission power of the visible light signal in the underwater visible light communication based on the acquired distance. A communication device according to any one of (1) to (10) above.

[0189] (12) a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the sonic communication unit receives the sonic signal transmitted from the target communication device; The control unit estimating the direction of arrival of the sound wave signal based on the sound wave signal received by the sound wave communication unit; Controlling the visible light communication unit so that the visible light communication direction coincides with the arrival direction A communication device according to any one of (1) to (11) above.

[0190] (13) The control unit acquiring a distance between the target communication device and the communication device based on an amount of attenuation calculated from the transmission power of the sound wave signal in the target communication device and the reception power of the sound wave signal received by the sound wave communication unit; and controlling an initial transmission power of the visible light signal in the underwater visible light communication based on the acquired distance. A communication device according to any one of (1) to (12) above.

[0191] (14) The control unit calculating an evaluation value indicating the accuracy of the direction of arrival estimation; Based on the calculated evaluation value, a movable range when adjusting the visible light communication direction in the underwater visible light communication is controlled. A communication device according to any one of (1) to (13) above.

[0192] (15) the sonic communication unit transmits to the target communication device and / or receives from the target communication device a connection sonic signal for establishing the visible light communication connection; The control unit controls the visible light communication unit to perform the underwater visible light communication with the target communication device after the visible light communication connection is established. A communication device according to any one of (1) to (14) above.

[0193] (16) the communication device is a terminal device that performs the underwater visible light communication with a base station device selected from a plurality of base station devices as the target communication device, The control unit controls the plurality of base station devices based on the information included in the sound wave signal. the control for selecting the target communication device from the A communication device according to any one of (1) to (15) above.

[0194] (17) The control unit acquiring a distance between the communication device and each base station device based on the sound wave signal; Based on the distance acquired for each of the base station devices, the control for selecting the target communication device from the A communication device according to any one of (1) to (16) above.

[0195] (18) the sonic wave communication unit receives the sonic signal including accommodation availability information indicating whether the base station device can accommodate the terminal device; The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the accommodation availability information included in the sound wave signal. A communication device according to any one of (1) to (17) above.

[0196] (19) the sonic communication unit receives the sonic signal including propagation environment information indicating a propagation environment that affects the underwater visible light communication with the base station device; the propagation environment information indicates at least one of turbidity and sunlight noise as the propagation environment, The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the propagation environment information included in the sound wave signal. A communication device according to any one of (1) to (18) above.

[0197] (20) the sonic wave communication unit receives the sonic signal including, as the information, recommended base station information indicating at least one base station device selected by a network side from among the plurality of base station devices; The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the recommended base station information included in the sound wave signal. A communication device according to any one of (1) to (19) above.

[0198] (twenty one) A communication method used in a communication device that performs underwater visible light communication with a target communication device, receiving a sound signal transmitted from the target communication device or another communication device, the sound signal including information used to control establishment of a visible light communication connection; performing control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal; and transmitting and receiving a visible light signal including communication data. Communication method. [Explanation of symbols]

[0199] 100: Communication equipment 100a: Terminal device 100b: Base station equipment 110: Visible light communication unit 111: Light-emitting part 112: Light receiving part 113: Drive unit 120: Sonic Communication Department 121: Transmitting unit 122: Receiving section 130: Control unit 140: Backhaul communication unit 150: GNSS positioning unit 200: Positioning communication device 300: Location management communication device 400: Network node 500: Optical sensor

Claims

1. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, the sonic wave communication unit receives the sonic signal including location information indicating the location of the target communication device as the information; The control unit performs control to establish the visible light communication connection with the target communication device based on the position information included in the sound wave signal. Communication equipment.

2. The sonic communication unit receives the sonic signal including the identifier of the target communication device as the information. The communication device according to claim 1 .

3. a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, The control unit acquiring the position of the target communication device through sound wave communication using the sound wave communication unit; Based on the position of the target communication device and the position of the communication device, the visible light communication unit is controlled so that the visible light communication direction is directed toward the target communication device.

3. The communication device according to claim 1 or 2.

4. A visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the sonic communication unit receives the sonic signal transmitted from the target communication device; The control unit estimating the direction of arrival of the sound wave signal based on the sound wave signal received by the sound wave communication unit; Controlling the visible light communication unit so that the visible light communication direction coincides with the arrival direction 3. The communication device according to claim 1 or 2.

5. The acoustic communication unit transmits a connection acoustic signal to the target communication device to establish the visible light communication connection and / or receives it from the target communication device; The control unit controls the visible light communication unit to perform the underwater visible light communication with the target communication device after the visible light communication connection is established.

3. The communication device according to claim 1 or 2.

6. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the sonic wave communication unit receives the sonic signal including location information indicating the location of the target communication device as the information; The control unit acquiring the position of the target communication device through sound wave communication using the sound wave communication unit; controlling the visible light communication unit based on a position of the target communication device and a position of the communication device so that the visible light communication direction is oriented toward the target communication device; The position of the target communication device is acquired based on the position information included in the sound wave signal. Communication equipment.

7. The sonic communication unit receives the sonic signal including the location information from the target communication device. The communication device according to claim 6.

8. The sonic communication unit receives the sonic signal including the location information from a location management communication device different from the target communication device. The communication device according to claim 6.

9. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the communication device is a terminal device that performs the underwater visible light communication with a base station device selected from a plurality of base station devices as the target communication device, The control unit acquiring the position of the target communication device through sound wave communication using the sound wave communication unit; controlling the visible light communication unit based on a position of the target communication device and a position of the communication device so that the visible light communication direction is oriented toward the target communication device; The location of the terminal device is further obtained through the acoustic wave communication. Communication equipment.

10. The acoustic wave communication unit Transmitting a first sonic signal; receiving a second sound wave signal from each base station device that has received the first sound wave signal; The control unit acquires the position of the terminal device based on a round-trip propagation time to and from each of the base station devices determined in response to reception of the second sound wave signal. The communication device according to claim 9.

11. The acoustic wave communication unit transmitting a first sound wave signal to a plurality of positioning communication devices different from the base station device; receiving a second sound wave signal from each positioning communication device that has received the first sound wave signal; The control unit acquires the position of the terminal device based on a round-trip propagation time to and from each of the positioning communication devices determined in response to reception of the second sound wave signal. The communication device according to claim 9.

12. the acoustic wave communication unit receives, as the acoustic signal, a positioning reference signal transmitted from each base station device in synchronization between the base station devices; The control unit acquires the position of the terminal device based on the received positioning reference signal. The communication device according to claim 9.

13. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, The control unit acquiring the position of the target communication device through sound wave communication using the sound wave communication unit; controlling the visible light communication unit based on a position of the target communication device and a position of the communication device so that the visible light communication direction is oriented toward the target communication device; acquiring a distance between the target communication device and the communication device based on the location of the target communication device and the location of the communication device; and controlling an initial transmission power of the visible light signal in the underwater visible light communication based on the acquired distance. Communication equipment.

14. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the sonic communication unit receives the sonic signal transmitted from the target communication device; The control unit estimating the direction of arrival of the sound wave signal based on the sound wave signal received by the sound wave communication unit; controlling the visible light communication unit so that the visible light communication direction is the arrival direction; acquiring a distance between the target communication device and the communication device based on an amount of attenuation calculated from the transmission power of the sound wave signal in the target communication device and the reception power of the sound wave signal received by the sound wave communication unit; and controlling an initial transmission power of the visible light signal in the underwater visible light communication based on the acquired distance. Communication equipment.

15. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, a visible light communication direction, which is a direction in which the visible light communication unit transmits the visible light signal, is variable, the sonic communication unit receives the sonic signal transmitted from the target communication device; The control unit estimating the direction of arrival of the sound wave signal based on the sound wave signal received by the sound wave communication unit; controlling the visible light communication unit so that the visible light communication direction is the arrival direction; calculating an evaluation value indicating the accuracy of the direction of arrival estimation; Based on the calculated evaluation value, a movable range when adjusting the visible light communication direction in the underwater visible light communication is controlled. Communication equipment.

16. A communication device that performs underwater visible light communication with a target communication device, a visible light communication unit that transmits and receives a visible light signal including communication data; a sonic communication unit that receives a sonic signal transmitted from the target communication device or another communication device and that includes information used to control establishment of a visible light communication connection; a control unit that performs control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal, the communication device is a terminal device that performs the underwater visible light communication with a base station device selected from a plurality of base station devices as the target communication device, The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the information included in the sound wave signal. Communication equipment.

17. The control unit acquiring a distance between the communication device and each base station device based on the sound wave signal; The control for selecting the target communication device from the plurality of base station devices is performed based on the distance acquired for each of the base station devices.

17. The communication device of claim 16.

18. the sonic wave communication unit receives the sonic signal including accommodation availability information indicating whether the base station device can accommodate the terminal device; The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the accommodation availability information included in the sound wave signal.

17. The communication device of claim 16.

19. the sonic communication unit receives the sonic signal including propagation environment information indicating a propagation environment that affects the underwater visible light communication with the base station device; the propagation environment information indicates at least one of turbidity and sunlight noise as the propagation environment, The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the propagation environment information included in the sound wave signal.

17. The communication device of claim 16.

20. the sonic wave communication unit receives the sonic signal including, as the information, recommended base station information indicating at least one base station device selected by a network side from among the plurality of base station devices; The control unit performs the control of selecting the target communication device from the plurality of base station devices based on the recommended base station information included in the sound wave signal.

17. The communication device of claim 16.

21. A communication method used in a communication device that performs underwater visible light communication with a target communication device, receiving a sound signal transmitted from the target communication device or another communication device, the sound signal including information used to control establishment of a visible light communication connection; performing control to establish the visible light communication connection with the target communication device based on the information included in the received sound wave signal; transmitting and receiving a visible light signal including communication data; In the receiving step, the sound wave signal including location information indicating a location of the target communication device is received as the information; In the step of performing the control, control is performed to establish the visible light communication connection with the target communication device based on the position information included in the sound wave signal. Communication method.

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