Control device, control system, control method, and control program

Abstract

In underwater communication using sound waves, there is a possibility that interference between sound waves may occur during a change in a use frequency. Thus, this control device performs control wherein, when changing respective use frequencies, which are the frequencies respectively used for wireless communication by a plurality of wireless communication devices using sound waves to communicate wirelessly underwater with a base station, a blank time is determined on the basis of the underwater wireless communication propagation period, said blank time being the period from a stop timing, which is the timing at which wireless communication using a pre-change use frequency is stopped, to a start timing, which is the timing at which wireless communication using a post-change use frequency is started, the start timing is calculated by adding the blank time to the stop timing, wireless communication using the pre-change use frequency is stopped at the stop timing, and wireless communication using the post-change use frequency is started at the calculated start timing.

Description

Control device, control system, control method, and recording medium

[0001] The present invention relates to a control device, a control system, a control method, and a recording medium.

[0002] It is being considered to communicate using acoustic waves underwater. Hereinafter, communication using acoustic waves underwater will be referred to as underwater acoustic communication.

[0003] Radio wave communication cannot be used at deep water because radio waves are significantly attenuated underwater. Therefore, sound waves are more suitable for communication than radio waves at deep water.

[0004] Recently, a method has been known in which a control device on land or on water communicates with a communication device underwater via a base station floating on the water surface. In this case, communication between the base station and the communication device is carried out by underwater acoustic communication, while communication between the base station and the control device is carried out by radio wave communication or wired communication.

[0005] In a system in which a control device communicates with an underwater communication device via a base station floating on the water surface, and communication between the base station and the communication device is performed by underwater acoustic communication, if multiple communication devices are present underwater, each communication device communicates with the base station, and therefore interference may occur between the sound waves transmitted from the multiple communication devices or base stations. Because interference may occur between sound waves, the operator of the underwater acoustic communication determines in advance the sound wave frequency used by each communication device so as to minimize the impact of interference between sound waves on communication.

[0006] Related techniques include those described in Patent Documents 1 and 2.

[0007] JP-T-2012-529230A JP-A-2019-153940A

[0008] Takenobu Tsuchiya, "Numerical analysis of acoustic wave propagation in the ocean," Information Processing Society of Japan Research Report, June 2019

[0009] However, even if the frequencies used by communication devices and base stations are set to minimize interference, acoustic interference may occur. For example, acoustic interference may occur if an interference source appears unexpectedly. An interference source is an object that emits interference waves. Furthermore, interference waves are waves that interfere with underwater acoustic communication.

[0010] During operation of a system in which communication between a base station and a communication device is performed by underwater acoustic communication, it is conceivable to change the frequency used by the wireless communication device in order to avoid interference of acoustic waves. Furthermore, since acoustic waves generally propagate farther than radio waves, there is a possibility that interference waves may affect multiple wireless communication devices. For this reason, it is conceivable to change the frequency used by multiple wireless communication devices.

[0011] However, while the frequencies used by the multiple wireless communication devices are being changed, interference between the sound waves transmitted from the multiple wireless communication devices or base stations may occur.

[0012] In view of the above-mentioned problems, an object of the present invention is to provide a control device, a control system, a control method, and a recording medium that make it possible to reduce the occurrence of interference caused by changes in the frequency used in underwater acoustic communication.

[0013] In one aspect of the present invention, when changing each of the operating frequencies, which are the frequencies used for each of the wireless communications by each of a plurality of wireless communication devices that perform wireless communication using acoustic waves with a base station underwater, the control device comprises: a determination means that determines a blank time, which is the time from a stop time, which is the time at which the wireless communication at the operating frequency before the change, to a start time, which is the time at which the wireless communication at the operating frequency after the change, based on the propagation time of the wireless communication underwater; a calculation means that calculates the start time by adding the blank time to the stop time; and a control means that controls a change target device, which is a wireless communication device that is the target of the change in the operating frequency, to stop wireless communication at the operating frequency before the change at the stop time and start wireless communication at the operating frequency after the change at the calculated start time.

[0014] In another aspect of the present invention, a control system includes a determination means for determining a blank time, which is the time from a stop time at which the wireless communication at the previous frequency before the change is stopped to a start time at which the wireless communication at the new frequency after the change is started, based on the propagation time of the wireless communication underwater when changing each of the operating frequencies, which are the frequencies used for each of the wireless communication by each of a plurality of wireless communication devices that perform wireless communication using acoustic waves with a base station underwater; a calculation means for calculating the start time by adding the blank time to the stop time; and a control means for controlling a change target device, which is a wireless communication device that is the target of the change in operating frequency, to stop wireless communication at the previous frequency before the change at the stop time and start wireless communication at the new frequency after the change at the calculated start time.

[0015] In another aspect of the present invention, when changing each of the operating frequencies, which are the frequencies used for each of the wireless communications by each of multiple wireless communication devices that perform wireless communication using acoustic waves with a base station underwater, the control method determines a blank time, which is the time from the stop time, which is the time at which the wireless communication at the operating frequency before the change, to the start time, which is the time at which the wireless communication at the operating frequency after the change, is started, based on the propagation time of the wireless communication underwater, calculates the start time by adding the blank time to the stop time, and controls the change target device, which is the wireless communication device that is the target of the change in the operating frequency, to stop the wireless communication at the operating frequency before the change at the stop time and start the wireless communication at the operating frequency after the change at the calculated start time.

[0016] In another aspect of the present invention, a control program recorded on a computer-readable recording medium causes a computer to realize the following functions when changing each of the operating frequencies used by multiple wireless communication devices that perform acoustic wireless communication with a base station underwater: a determination function that determines a blank time, which is the time from a stop time at which the wireless communication at the operating frequency before the change is stopped to a start time at which the wireless communication at the operating frequency after the change is started, based on the propagation time of the wireless communication underwater; a calculation function that calculates the start time by adding the blank time to the stop time; and a control function that controls a change target device, which is a wireless communication device that is the target of the change in the operating frequency, to stop wireless communication at the operating frequency before the change at the stop time and start wireless communication at the operating frequency after the change at the calculated start time.

[0017] According to the above aspect of the present invention, it is possible to reduce the occurrence of interference caused by changes in the frequency used in underwater communication using sound waves.

[0018] FIG. 1 is a diagram illustrating an example of the configuration of a control device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of the operation flow of a control device according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating an example of the configuration of a communication system including a control device according to a second embodiment of the present invention. FIG. 4 is a diagram for explaining blank time. FIG. 5 is a diagram illustrating another example of the configuration of a control device according to a second embodiment of the present invention. FIG. 6 is a diagram illustrating an example of the operation flow of a wireless communication device according to a second embodiment of the present invention. FIG. 7 is a diagram illustrating an example of the hardware configuration of each embodiment of the present invention.

[0019] First Embodiment A first embodiment of the present invention will be described. A specific example of the control device 10 in the first embodiment is a control device 20 in a second embodiment, which will be described later.

[0020] 1 shows an example of the configuration of a control device 10 according to this embodiment. The control device 10 includes a determination unit 11, a calculation unit 12, and a control unit 13.

[0021] When changing each of the operating frequencies, the determination unit 11 determines the blank time based on the propagation time of wireless communication underwater. The multiple wireless communication devices perform wireless communication using sound waves with a base station underwater. The operating frequencies are frequencies used for each of the wireless communication communications by each of the multiple wireless communication devices. The blank time is the time from the stop time to the start time. The stop time is the time at which wireless communication using the operating frequency before the change is stopped. The start time is the time at which wireless communication using the operating frequency after the change is started.

[0022] The calculation unit 12 calculates the start time by adding the blank time to the stop time.

[0023] The control unit 13 controls the change target device to stop wireless communication at the frequency used before the change at the stop time and start wireless communication at the frequency used after the change at the calculated start time. The change target device is a wireless communication device whose frequency is to be changed.

[0024] Next, FIG. 2 shows an example of an operation flow of the control device 10 of this embodiment.

[0025] The determination unit 11 determines the blank time based on the propagation time of wireless communication in water (step S101).

[0026] The calculation unit 12 calculates the start time by adding the blank time to the stop time (step S102).

[0027] The control unit 13 controls the change target device to stop wireless communication at the frequency used before the change at the stop time and start wireless communication at the frequency used after the change at the calculated start time (step S103).

[0028] As described above, in the first embodiment of the present invention, the control device 10 includes a determination unit 11, a calculation unit 12, and a control unit 13. When changing each of the operating frequencies, the determination unit 11 determines a blank time based on the propagation time of wireless communication underwater. The multiple wireless communication devices perform wireless communication using acoustic waves with a base station underwater. The operating frequency is a frequency used by each of the multiple wireless communication devices for wireless communication. The blank time is the time from the stop time to the start time. The stop time is the time at which wireless communication using the operating frequency before the change is stopped. The start time is the time at which wireless communication using the operating frequency after the change is started. The calculation unit 12 calculates the start time by adding the blank time to the stop time. The control unit 13 controls the change target device to stop wireless communication using the operating frequency before the change at the stop time and start wireless communication using the operating frequency after the change at the calculated start time. The change target device is a wireless communication device whose operating frequency is to be changed.

[0029] This provides a blank time between the termination of wireless communication at the previous operating frequency and the commencement of wireless communication at the new operating frequency. The blank time is determined based on the underwater propagation time of wireless communication. As a result, it is possible to reduce the possibility of interference between signals transmitted before the termination of wireless communication and wireless communication at the new operating frequency. This makes it possible to reduce interference caused by a change in operating frequency in underwater acoustic wave communications.

[0030] Second Embodiment Next, a second embodiment of the present invention will be described. A specific example of the control device 10 in the first embodiment is a control device 20 in the second embodiment.

[0031] 3 shows an example of the configuration of a communication system 60 including the control device 20 of this embodiment. The communication system 60 includes the control device 20, a base station 40, and a wireless communication device 50-i (i is an integer from 1 to N, and N is an integer equal to or greater than 1).

[0032] The base station 40 is located on the water and is capable of wireless communication with the wireless communication device 50-i using acoustic waves.

[0033] The wireless communication device 50-i exists underwater. The wireless communication device 50-i can perform wireless communication using acoustic waves with the base station 40. The wireless communication device 50-i can communicate with the control device 20 via the base station 40.

[0034] The control device 20 is connected to the base station 40. The control device 20 is located on water or on land. The control device 20 can communicate with the base station 40 wirelessly using radio waves or via wired communication. The control device 20 also controls the frequency used by the wireless communication device 50-i. The frequency used is a frequency used by the wireless communication device 50-i for wireless communication using sound waves with the base station 40. The wireless communication may be communication using band signals. In this case, the frequency used may be a frequency band. When the wireless communication is communication using band signals, the term "frequency" refers to a "frequency band." The frequencies used by the wireless communication devices 50-1 to 50-N may be different from each other or may include the same frequencies.

[0035] 4 shows an example of the configuration of the control device 20 of this embodiment. The control device 20 includes a determination unit 21, a calculation unit 22, and a control unit 23.

[0036] The determination unit 21 determines the blank time based on the propagation time of wireless communication between the wireless communication device 50-i and the base station 40. The blank time is the time from the stop time to the start time. The stop time is the time at which wireless communication using the frequency before the change is stopped. The start time is the time at which the wireless communication device 50-i starts wireless communication using the frequency after the change.

[0037] The determination unit 21 determines the blank time when it is determined that the frequency used by the wireless communication device 50-i is to be changed. The control device 20 determines to change the frequency used by the wireless communication device 50-i, for example, when there is a possibility that interference will occur in the wireless communication between the wireless communication device 50-i and the base station 40. The control device 20 can change the frequencies used by one or more wireless communication devices. A wireless communication device whose frequency is to be changed may hereinafter be referred to as a device subject to change.

[0038] Interference may occur, for example, when another operator communicates using sound waves or when unexpected interference waves occur. Note that interference waves are waves that interfere with wireless communication between the wireless communication device 50-i and the base station 40. Unexpected interference waves may occur, for example, when construction work that generates noise is carried out on water, on land, or underwater.

[0039] The determination unit 21 determines the blank time based on the propagation time of wireless communication between the change target device and the base station 40. When there are two or more change target devices, the determination unit 21 determines, for example, the longest round-trip propagation time (maximum round-trip propagation time) among the round-trip propagation times of wireless communication between each of the change target devices and the base station 40 as the blank time.

[0040] FIG. 5 is a diagram illustrating blank time. In the example of FIG. 5, the change target devices are wireless communication device 50-1, wireless communication device 50-2, and wireless communication device 50-3. The control device 20 transmits a change instruction for the frequency in use via the base station 40 (step S201). The wireless communication devices 50-1 to 50-3 stop wireless communication using the pre-change frequency in accordance with the stop time information included in the change instruction (steps S202 to S204). The wireless communication devices 50-1 to 50-3 also start wireless communication using the post-change frequency in accordance with the start time information included in the change instruction (steps S205 to S207). Note that in FIG. 5, it is assumed that there is no discrepancy between the internal times of the base station 40 and the wireless communication devices 50-1 to 50-3.

[0041] Here, it is assumed that wireless communication device 50-3 is the device with the longest round-trip propagation time among wireless communication devices 50-1 to 50-3. Furthermore, it is assumed that wireless communication device 50-3 transmits a signal (dashed arrow in FIG. 5 ) to base station 40 before stopping wireless communication in step S204. In this case, if wireless communication device 50-1 or wireless communication device 50-2 starts wireless communication at the changed frequency before the signal reaches base station 40, there is a possibility that the signal will not reach base station 40 due to the influence of interference. In other words, if any wireless communication device starts wireless communication between the time when any wireless communication device starts changing the frequency in use and the time when all wireless communication devices have completed the change, there is a possibility that interference will occur due to the change in the frequency in use.

[0042] To avoid this interference, it is conceivable to synchronize the time between wireless communication devices and simultaneously change the frequency used. However, because GNSS (Global Navigation Satellite System) signals are difficult to reach underwater, time synchronization using GNSS signals is difficult. Furthermore, because the uplink and downlink propagation times can differ underwater, it is difficult to estimate the downlink or uplink propagation times alone. Therefore, even with methods such as NTP (Network Time Protocol), time synchronization between wireless communication devices is difficult.

[0043] Therefore, in this embodiment, a blank time is provided between the stop time and the start time to reduce the possibility of interference occurring when the frequency used is changed.

[0044] In this embodiment, a blank time is provided between the stop of wireless communication at the previous operating frequency and the start of wireless communication at the new operating frequency, thereby reducing the occurrence of interference due to a change in the operating frequency. Furthermore, by determining the blank time based on the propagation time, the blank time can be made shorter than when a fixed blank time is set redundantly with respect to the propagation time, thereby shortening the time during which wireless communication is stopped.

[0045] If the blank time is longer than the time it takes for a signal transmitted from the change target device to reach the base station 40, it is possible to reduce the possibility of interference occurring due to the change in the frequency used. Therefore, the blank time should be longer than the longest one-way propagation time among the one-way propagation times from each of the change target devices to the base station 40.

[0046] However, in underwater wireless communication using sound waves, the sound waves may travel different routes on the outbound and return journeys, which may result in significantly different propagation times for the outbound and return journeys. Furthermore, it is not easy to determine the one-way propagation time. Therefore, in this embodiment, the longest round-trip propagation time (maximum round-trip propagation time) among the round-trip propagation times for wireless communication between each of the change target devices and the base station 40 is used as the blank time.

[0047] The determination unit 21 may further determine the blank time by taking into consideration at least one of the effects of multipath, a deviation in the internal time, and a deviation in the wireless communication device 50-i's own location. The internal time is the time measured by a clock means provided in the wireless communication device 50-i. The own location is the location of the wireless communication device 50-i estimated by the wireless communication device 50-i.

[0048] The propagation time may be simply estimated based on the distance between the base station 40 and the change target device and the speed of sound. However, due to the influence of multipath, the propagation time may differ from the simply estimated time. Therefore, the propagation time may be estimated by a method that takes into account the influence of multipath. The blank time may then be determined based on the propagation time estimated by the method that takes into account the influence of multipath.

[0049] Furthermore, the change instruction sent to the change target device includes information on the stop time and the start time. However, if there is a discrepancy between the internal time of the change target device and the internal time of the base station 40, wireless communication may start in a shorter time than originally expected. Therefore, the blank time may be determined taking into account the discrepancy between the internal time of the change target device and the internal time of the base station 40.

[0050] Furthermore, when the propagation time is calculated based on the position of the change target device, an error in the propagation time occurs due to an error in the position information. When the position of the change target device is estimated by the change target device, an error in the estimated position (self-position) occurs due to an error in the propagation time. If the calculated propagation time is shorter than the actual propagation time, wireless communication at the changed frequency may start while a signal at the frequency before the change is being propagated, which may cause interference. Therefore, the blank time may be determined taking into account the difference between the self-position and the actual position.

[0051] The determination unit 21 may determine the blank time as, for example, the sum of (A) the longest round-trip propagation time, (B) the propagation time error due to a deviation in internal time, and (C) the propagation time error due to a deviation in the self-position.

[0052] (A) Longest Round Trip Propagation Time The longest round trip propagation time is the longest round trip propagation time among the round trip propagation times of wireless communication between each of the change target devices and the base station 40.

[0053] When the distance between the base station 40 and the change target device can be determined by some method, the determination unit 21 may calculate the round-trip propagation time using the following formula: For example, the determination unit 21 may receive location information of the change target device from the change target device.

[0054] [Mathematical Expression 1] Round-trip propagation time = (distance between base station 40 and change target device) / speed of sound × 2 Furthermore, when the distance between base station 40 and change target device is unknown, determination unit 21 may calculate the longest round-trip propagation time using the following formula: In this case, the longest round-trip propagation time is a fixed value.

[0055] [Mathematical Expression 2] Longest round trip propagation time = Maximum distance over which communication from base station 40 can be received ÷ Speed ​​of sound × 2 Furthermore, the determination unit 21 may measure the round trip propagation time for each change target device. For example, the determination unit 21 sends a signal to the change target device via base station 40 and receives an ACK (Acknowledgement) from the change target device. Then, the determination unit 21 determines the longest time (round trip propagation time) from signal transmission to ACK reception as the longest round trip propagation time. With this method, the round trip propagation time is derived by actual measurement, and therefore the influence of multipath is taken into account in the longest round trip propagation time.

[0056] The determination unit 21 may also calculate the longest round-trip propagation time from a sound wave propagation profile. The propagation profile indicates the results of a simulation of sound wave propagation. For example, the propagation profile indicates the extent to which sound waves emitted from a certain point are attenuated at each underwater point. The propagation profile is created in advance. Note that the propagation profile is created taking into account the effects of multipath, so this method also takes into account the effects of multipath in the longest round-trip propagation time. The determination unit 21 can calculate the longest round-trip propagation time from the position of the device to be changed and the propagation profile.

[0057] The propagation profile is statistically created and may be stored in advance in a storage unit (not shown) inside or outside the control device 20 .

[0058] The propagation profile may also be created by the creation unit 24. In this case, the control device includes the creation unit 24. The creation unit 24 creates the propagation profile. An example configuration of the control device 30 including the creation unit 24 is shown in FIG. 6. The creation unit 24 can create the propagation profile from, for example, the positions and depths of the base station 40 and the wireless communication device 50-i, topographical information about the area around the base station 40, and sound speed distributions in the vertical and horizontal directions.

[0059] The topographical information is information that indicates the shape of the land. For example, the topographical information indicates the topography of the seabed. The topographical information is stored in advance in a storage unit (not shown) inside or outside the control device 20. Note that in this embodiment, it is assumed that the base station 40 does not move, or if it does move, the distance it moves is short. The storage unit stores underwater topographical information around the base station 40.

[0060] The speed of sound in the ocean, for example, depends on water temperature, pressure (depth), and salinity. The creation unit 24 may receive information acquired by an information acquisition device (not shown) from the information acquisition device and estimate the vertical and horizontal sound speed distributions based on the received information. The sound speed distribution indicates the sound speed at each point in the water. In this case, the information acquisition device acquires information about the depth of the information acquisition device. The information acquisition device also acquires information about at least one of the water temperature and salinity around the information acquisition device. For example, the information acquisition device may be equipped with a depth sensor and acquire information about the depth of the information acquisition device. For example, the information acquisition device may be equipped with a water temperature sensor and acquire information about the water temperature around the information acquisition device. For example, the information acquisition device may be equipped with a salinity sensor and acquire information about the salinity around the information acquisition device. The information acquisition device may also be a wireless communication device 50-i. The information acquisition device may also be an underwater drone for information acquisition.

[0061] Note that GNSS cannot be used to estimate the position of the information acquisition device underwater. Therefore, the creation unit 24 may estimate the position of the information acquisition device based on the direction of arrival of sound waves emitted by the information acquisition device relative to the base station 40. For example, the creation unit 24 receives information on the direction of arrival of sound waves emitted by the information acquisition device from the base station 40. The creation unit 24 also receives information on the vertical position (depth) of the information acquisition device from the information acquisition device via the base station 40. The creation unit 24 can then estimate the position of the information acquisition device based on the information on the direction of arrival and the information on the vertical position (depth).

[0062] Alternatively, the creation unit 24 may receive information from an information server (not shown). The information server estimates the current water temperature and salinity at a predetermined location based on, for example, information on past water temperature and salinity.

[0063] The creation unit 24 can also receive information about the vertical position (depth) of the wireless communication device 50-i from the wireless communication device 50-i. The wireless communication device 50-i is equipped with a pressure (depth) sensor and acquires information about the vertical position (depth) of the wireless communication device 50-i. The creation unit 24 may also estimate the position of the wireless communication device 50-i in a manner similar to the method described above.

[0064] Furthermore, the creation unit 24 can simulate the propagation of sound waves based on the sound speed distribution in the vertical and horizontal directions, for example, by using the method described in Non-Patent Document 1, and create a propagation profile.

[0065] Next, (B) the propagation time error due to internal time deviation will be described. The internal time is the time of the clock means provided in the change target device. The determination unit 21 may calculate the propagation time error due to internal time deviation, for example, using catalog values ​​or statistical data of the internal time deviation. Note that the catalog values ​​are design values, and are values ​​listed in, for example, a catalog of the clock means. The statistical data is data related to the measurement results of the internal time deviation. The catalog values ​​or statistical data are stored in advance in a memory unit inside or outside the control device 20. The determination unit 21 may also calculate the propagation time error based on the time elapsed since time synchronization. For example, the determination unit 21 may calculate the propagation time error by multiplying the elapsed time by a predetermined coefficient.

[0066] The determination unit 21 uses the largest error among the errors of the change target devices as (B) the propagation time error due to internal time deviation. In the above method, the wireless communication device moves close to the base station 40 at predetermined time intervals to perform time synchronization. The control device 20 then stores the time when time synchronization was last performed for each of the wireless communication devices 50-1 to 50-N in a storage unit (not shown).

[0067] Next, (C) Error in propagation time due to deviation in self-position will be described. Self-position is the position of the wireless communication device 50-i that is known by the wireless communication device 50-i. When the wireless communication device 50-i estimates its self-position using an inertial sensor, deviation occurs between the estimated self-position and the actual position as time passes after calibration. When the propagation time is estimated using this self-position, an error occurs in the propagation time.

[0068] The determination unit 21 calculates the deviation of the self-position, for example, using a catalog value or statistical data. The catalog value is a design value, for example, a value listed in a catalog of an acceleration sensor. The statistical data is data related to the measurement results of the deviation of the self-position. The catalog value or statistical data is stored in advance in a storage unit inside or outside the control device 20. The determination unit 21 may calculate the propagation time error due to the deviation of the self-position using the catalog value or statistical data of the deviation of the self-position. The determination unit 21 may also calculate the propagation time error based on the elapsed time since calibration. For example, the determination unit 21 may calculate the propagation time error by multiplying the elapsed time since calibration by a predetermined coefficient. The control device 20 stores the time when the last position calibration was performed for each of the wireless communication devices 50-1 to 50-N in a storage unit (not shown).

[0069] Even when the position of the wireless communication device 50-i is estimated by the control device 20 based on the depth of the wireless communication device 50-i and the direction of arrival of the signal, an error occurs in the estimated position due to an error in the direction of arrival or the depth. Therefore, in this case as well, the determination unit 21 may calculate an error in the propagation time due to a deviation in the estimated position.

[0070] The calculation unit 22 calculates the start time by adding the blank time to the stop time. The stop time is the time when wireless communication using the previous operating frequency is stopped. The start time is the time when wireless communication device 50-i starts wireless communication using the new operating frequency.

[0071] As described above, the blank time is a time based on the propagation time of wireless communication between the change target device and the base station 40. The stop time is later than the time when the change instruction arrives at the change target device. Therefore, the calculation unit 22 may, for example, determine the stop time to be the time obtained by adding the blank time to the scheduled time of transmission of the instruction to change the frequency in use. The stop time may also be a time later than the time obtained by adding the blank time to the scheduled time of transmission of the change instruction. For example, the stop time may be the time obtained by adding a fixed value larger than the blank time to the scheduled time of transmission of the change instruction.

[0072] Furthermore, the calculation unit 22 calculates the start time by adding a blank time to the calculated stop time. As described above, by providing a blank time between the start time and the stop time, it is possible to reduce the influence of interference caused by a change in the frequency used.

[0073] The control unit 23 controls the change target device to stop wireless communication at the frequency used before the change at the stop time and start wireless communication at the frequency used after the change at the calculated start time. The change target device is a wireless communication device whose frequency used is to be changed. The control unit 23 transmits, for example, an instruction to change the frequency used to the change target device. The instruction to change includes information on the stop time, information on the calculated start time, and information on the frequency used after the change.

[0074] The frequency used to transmit the change instruction may be the frequency used before the change, or, since interference may occur, a frequency for the change instruction that is different from the frequency used before the change may be used to transmit the change instruction.

[0075] In this embodiment, the control device 20 does not assume that an ACK is received in response to the change instruction, but the change instruction may be issued by a method that assumes the receipt of an ACK. For example, the control unit 23 may first notify the change target devices of a change notification indicating that the operating frequency will be changed. Then, when the control unit 23 receives ACKs from all of the change target devices, it may transmit a change instruction including a stop time, a start time, and the operating frequency after the change. In this case, the determination unit 21 may measure the round-trip propagation time using the change notification.

[0076] Furthermore, the control device 20 may use a method that does not require an ACK when it is desired to change the operating frequency as quickly as possible, such as when changing the frequency due to the occurrence of interference, and may use a method that requires an ACK when reliability is required. The control device 20 may also be able to switch between a method that requires an ACK and a method that does not require an ACK. This switching may be performed based on an instruction from another device to the control device 20, or may be performed by the control device 20 depending on the reason for the frequency change.

[0077] In response to the change instruction, the change target device stops wireless communication at the pre-change operating frequency when the stop time arrives, and also starts wireless communication at the post-change operating frequency when the start time arrives, in response to the change instruction.

[0078] Next, an example of the operation flow of the control device 20 and the wireless communication device 50-i will be described with reference to Fig. 7 and Fig. 2. Fig. 7 shows an example of the operation flow of the wireless communication device 50-i.

[0079] The determination unit 21 of the control device 20 determines the blank time based on the propagation time of wireless communication in water (step S101 in FIG. 2). Note that the determination unit 21 determines the blank time when, for example, it is determined to change the frequency to be used.

[0080] The calculation unit 22 calculates the start time by adding the blank time to the stop time (step S102).

[0081] The control unit 23 controls the change target device to stop wireless communication at the frequency used before the change at the stop time and start wireless communication at the frequency used after the change at the calculated start time (step S103). The control unit 23 transmits, for example, a change instruction to the change target device. The change instruction includes information on the stop time, information on the calculated start time, and information on the frequency used after the change.

[0082] When the wireless communication device 50-i receives the change instruction (step S301 in FIG. 7), it stops wireless communication at the frequency used before the change when the internal time of the wireless communication device 50-i reaches the stop time (step S302).

[0083] The wireless communication device 50-i changes the frequency used (step S303).

[0084] When the internal time of the wireless communication device 50-i reaches the start time, the wireless communication device 50-i starts wireless communication at the new operating frequency (step S304).

[0085] As described above, in the second embodiment of the present invention, the control device 20 includes the determination unit 21, the calculation unit 22, and the control unit 23. When changing each of the operating frequencies, the determination unit 21 determines a blank time based on the propagation time of wireless communication underwater. The multiple wireless communication devices perform wireless communication using acoustic waves underwater with a base station. The operating frequency is a frequency used by each of the multiple wireless communication devices for wireless communication. The blank time is the time from the stop time to the start time. The stop time is the time at which wireless communication using the operating frequency before the change is stopped. The start time is the time at which wireless communication using the operating frequency after the change is started. The calculation unit 22 calculates the start time by adding the blank time to the stop time. The control unit 23 controls the change target device to stop wireless communication using the operating frequency before the change at the stop time and start wireless communication using the operating frequency after the change at the calculated start time. The change target device is a wireless communication device whose operating frequency is to be changed.

[0086] This provides a blank time between the termination of wireless communication at the previous operating frequency and the commencement of wireless communication at the new operating frequency. The blank time is determined based on the underwater propagation time of wireless communication. As a result, it is possible to reduce the possibility of interference between signals transmitted before the termination of wireless communication and wireless communication at the new operating frequency. This makes it possible to reduce interference caused by a change in operating frequency in underwater acoustic wave communications.

[0087] Furthermore, the determination unit 21 determines the blank time based on the longest round-trip propagation time of wireless communication between each of the change target devices and the base station. This makes it possible to reduce interference caused by changing the frequency used in underwater sound wave communication, where it is difficult to estimate the one-way propagation time.

[0088] Furthermore, the determination unit 21 calculates the propagation time based on a propagation profile indicating the results of a simulation of sound wave propagation and the position of the change target device, thereby enabling the determination unit 21 to more accurately calculate the propagation time even when there is an effect of multipath.

[0089] The control device 30 may further include a creation unit 24 that creates a propagation profile based on topographical information about the area around the base station and a sound speed distribution that indicates the sound speed at each underwater point. This allows the control device 20 to create the propagation profile itself.

[0090] Furthermore, the determination unit 21 may determine the blank time based on the error in propagation time due to the difference between the internal time of the wireless communication device and the internal time of the base station, thereby making it possible to further reduce the occurrence of interference due to changes in the frequency used.

[0091] Furthermore, the determination unit 21 may determine the blank time based on an error in propagation time due to a difference between the location indicated by the location information of the wireless communication device and the actual location, thereby making it possible to further reduce the occurrence of interference due to a change in the frequency used.

[0092] Furthermore, the change target device stops wireless communication at the frequency used before the change at the stop time and starts wireless communication at the frequency used after the change at the start time, thereby realizing the change of frequency in the wireless communication device.

[0093] [Hardware Configuration Example] An example of the configuration of hardware resources for realizing the control device (10, 20, 30) in each of the above-described embodiments of the present invention using one information processing device (computer) will be described. Note that the control device may be physically or functionally realized using at least two information processing devices. Also, the control device may be realized as a dedicated device. Also, only some of the functions of the control device may be realized using an information processing device. Also, at least some of the functions of the control device may be realized on the cloud.

[0094] 8 is a diagram illustrating an example of the hardware configuration of an information processing device that can realize the control device according to each embodiment of the present invention. The information processing device 90 includes a communication interface 91, an input / output interface 92, a computing device 93, a storage device 94, a nonvolatile storage device 95, and a drive device 96.

[0095] 1 can be realized by the communication interface 91 and the arithmetic unit 93. The determination unit 11 and the calculation unit 12 can be realized by the arithmetic unit 93.

[0096] The communication interface 91 is a communication means for the control device of each embodiment to communicate with an external device via a wired or / and wireless connection. When the control device is realized using at least two information processing devices, the devices may be connected to each other via the communication interface 91 so as to be able to communicate with each other.

[0097] The input / output interface 92 is a man-machine interface including a keyboard as an example of an input device and a display as an output device.

[0098] The arithmetic unit 93 is realized by a general-purpose central processing unit (CPU), a microprocessor, or other arithmetic processing device, and a plurality of electric circuits. The arithmetic unit 93 is capable of, for example, reading various programs stored in a nonvolatile storage device 95 into the storage device 94 and executing processing in accordance with the read programs.

[0099] The storage device 94 is a memory device such as a RAM (Random Access Memory) that can be accessed by the arithmetic device 93, and stores programs, various data, etc. The storage device 94 may be a volatile memory device.

[0100] The nonvolatile storage device 95 is a nonvolatile storage device such as a ROM (Read Only Memory) or a flash memory, and is capable of storing various programs, data, and the like.

[0101] The drive device 96 is, for example, a device that processes reading and writing of data from and to a recording medium 97, which will be described later.

[0102] The recording medium 97 is any recording medium capable of recording data, such as an optical disk, a magneto-optical disk, or a semiconductor flash memory.

[0103] Each embodiment of the present invention may be realized, for example, by configuring a control device using the information processing device 90 illustrated in Figure 8 and supplying this control device with a program capable of realizing the functions described in each of the above embodiments.

[0104] In this case, the embodiment can be realized by having the arithmetic unit 93 execute a program supplied to the control unit. Also, it is possible to configure some, but not all, of the functions of the control unit in the information processing unit 90.

[0105] Furthermore, the control device may be configured so that the program is recorded on a recording medium 97 and is stored in the nonvolatile storage device 95 as appropriate when the control device is shipped or when it is in operation. In this case, the program may be supplied by installing it in the control device using an appropriate jig during the manufacturing stage before shipping or during operation. The program may also be supplied by a general procedure such as downloading it from an external source via a communication line such as the Internet.

[0106] Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0107] (Supplementary Note 1) A control device comprising: a determination means for determining, when changing each of the operating frequencies used by a plurality of wireless communication devices that perform underwater wireless communication using acoustic waves with a base station, a blank time, which is the time from a stop time at which the wireless communication at the operating frequency before the change is stopped to a start time at which the wireless communication at the operating frequency after the change is started, based on a propagation time of the wireless communication underwater; a calculation means for calculating the start time by adding the blank time to the stop time; and a control means for controlling a change target device, which is a wireless communication device that is the target of the change of the operating frequency, to stop wireless communication at the operating frequency before the change at the stop time and start wireless communication at the operating frequency after the change at the calculated start time.

[0108] (Supplementary Note 2) The control device according to Supplementary Note 1, wherein the determining means determines the blank time based on a longest round-trip propagation time among round-trip propagation times of the wireless communication between each of the change target devices and the base station.

[0109] (Supplementary Note 3) The control device according to Supplementary Note 1 or Supplementary Note 2, wherein the determining means calculates the propagation time based on a propagation profile indicating a result of a simulation of sound wave propagation and a position of the change target device.

[0110] (Supplementary Note 4) The control device according to Supplementary Note 3, further comprising: a creating unit that creates the propagation profile based on topographical information around the base station and a sound speed distribution that indicates the sound speed at each underwater point.

[0111] (Supplementary Note 5) The control device according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the determining means further determines the blank time based on an error in the propagation time due to a difference between an internal time of the wireless communication device and an internal time of the base station.

[0112] (Supplementary Note 6) The control device according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the determining means further determines the blank time based on an error in the propagation time due to a difference between a position indicated by position information of the wireless communication device and an actual position.

[0113] (Supplementary Note 7) The control device according to any one of Supplementary Notes 1 to 6, wherein the change target device stops the wireless communication using the operating frequency before the change at the stop time and starts the wireless communication using the operating frequency after the change at the start time.

[0114] (Supplementary Note 8) A control system comprising: a determination means for, when changing each of a plurality of wireless communication devices that perform wireless communication using sound waves with a base station underwater, determining a blank time, which is the time from a stop time at which the wireless communication at the operating frequency before the change is stopped to a start time at which the wireless communication at the operating frequency after the change is started, based on a propagation time of the wireless communication underwater; a calculation means for calculating the start time by adding the blank time to the stop time; and a control means for performing control for a change target device, which is a wireless communication device that is the target of the change of the operating frequency, to stop the wireless communication at the operating frequency before the change at the stop time and start the wireless communication at the operating frequency after the change at the calculated start time.

[0115] (Supplementary Note 9) A control method, when changing each of the operating frequencies which are frequencies used for each of a plurality of wireless communication devices which perform wireless communication by sound waves with a base station underwater, comprising: determining a blank time which is the time from a stop time at which the wireless communication at the operating frequency before the change is stopped to a start time at which the wireless communication at the operating frequency after the change is started based on a propagation time of the wireless communication underwater; calculating the start time by adding the blank time to the stop time; and controlling a change target device which is a wireless communication device which is the target of the change of the operating frequency to stop the wireless communication at the operating frequency before the change at the stop time and start the wireless communication at the operating frequency after the change at the calculated start time.

[0116] (Supplementary Note 10) A computer-readable recording medium having recorded thereon a control program that causes a computer to realize the following: a determination function that, when changing each of the operating frequencies used by each of a plurality of wireless communication devices that perform wireless communication using sound waves with a base station underwater, determines a blank time, which is the time from a stop time at which the wireless communication at the operating frequency before the change is stopped to a start time at which the wireless communication at the operating frequency after the change is started, based on a propagation time of the wireless communication underwater; a calculation function that calculates the start time by adding the blank time to the stop time; and a control function that performs control for a change target device, which is a wireless communication device that is the target of the change of the operating frequency, to stop the wireless communication at the operating frequency before the change at the stop time and start the wireless communication at the operating frequency after the change at the calculated start time.

[0117] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0118] This application claims priority based on Japanese Patent Application No. 2023-118751, filed on July 21, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0119] 10, 20, 30 Control device 11, 21 Determination unit 12, 22 Calculation unit 13, 23 Control unit 24 Creation unit 40 Base station 50-i Wireless communication device 90 Information processing device 91 Communication interface 92 Input / output interface 93 Arithmetic unit 94 Storage device 95 Non-volatile storage device 96 Drive device 97 Recording medium

Claims

1. When each of multiple wireless communication devices that conduct underwater wireless communication using sound waves with a base station changes the operating frequency used for each of the wireless communications, a determination means for determining a blank time, which is the time from the stop time when the wireless communication on the operating frequency before the change is stopped to the start time when the wireless communication on the operating frequency after the change is started, based on the propagation time of the wireless communication underwater, A calculation means for calculating the start time by adding the blank time to the stop time, Control means for controlling a wireless communication device, which is the wireless communication device whose operating frequency is to be changed, to stop the wireless communication at the operating frequency before the change at the stop time, and to start the wireless communication at the operating frequency after the change at the calculated start time. A control device equipped with the following features.

2. The determination means determines the blank time based on the longest round-trip propagation time of the wireless communication between each of the devices to be modified and the base station. The control device according to claim 1.

3. The determination means calculates the propagation time based on the propagation profile showing the results of a sound wave propagation simulation and the position of the device to be modified. The control device according to claim 1.

4. A creation means for creating the propagation profile based on topographic information around the base station and a sound velocity distribution indicating the sound velocity at each point in the water. The control device according to claim 3, further comprising:

5. The determination means further determines the blank time based on the propagation time error caused by the difference between the internal time of the wireless communication device and the internal time of the base station. The control device according to claim 1.

6. The determination means further determines the blank time based on the error in propagation time caused by the discrepancy between the position indicated by the position information of the wireless communication device and the actual position. The control device according to claim 1.

7. The device subject to modification shall stop the wireless communication at the frequency used before the modification at the stop time, and start the wireless communication at the frequency used after the modification at the start time. The control device according to any one of claims 1 to 6.

8. When each of multiple wireless communication devices that conduct underwater wireless communication using sound waves with a base station changes the operating frequency used for each of the wireless communications, a determination means for determining a blank time, which is the time from the stop time when the wireless communication on the operating frequency before the change is stopped to the start time when the wireless communication on the operating frequency after the change is started, based on the propagation time of the wireless communication underwater, A calculation means for calculating the start time by adding the blank time to the stop time, Control means for controlling a wireless communication device, which is the wireless communication device whose operating frequency is to be changed, to stop the wireless communication at the operating frequency before the change at the stop time, and to start the wireless communication at the operating frequency after the change at the calculated start time. A control system equipped with the following features.

9. When changing the operating frequency used for each of the wireless communications performed underwater by multiple wireless communication devices that communicate with a base station using sound waves, a blank time is determined based on the propagation time of the wireless communications underwater, which is the time from the stop time when the wireless communications on the previous operating frequency are stopped to the start time when the wireless communications on the new operating frequency are started. The start time is calculated by adding the blank time to the stop time. With respect to the wireless communication device that is subject to the change in the operating frequency, control is performed to stop the wireless communication at the operating frequency before the change at the stop time, and to start the wireless communication at the changed frequency at the calculated start time. Control method.

10. On the computer, When each of multiple wireless communication devices that perform underwater wireless communication using sound waves with a base station changes the operating frequency used for each of the wireless communications, a determination function is provided to determine the blank time, which is the time from the stop time when the wireless communication on the operating frequency before the change is stopped to the start time when the wireless communication on the operating frequency after the change is started, based on the propagation time of the wireless communication underwater. A calculation function that calculates the start time by adding the blank time to the stop time, A control function that controls the wireless communication device, which is the wireless communication device whose operating frequency is to be changed, to stop the wireless communication at the operating frequency before the change at the stop time, and to start the wireless communication at the operating frequency after the change at the calculated start time. A control program that makes this possible.