Communication device, communication system, and communication method

Abstract

To achieve high positioning accuracy even when a communication frequency band is a narrow band.SOLUTION: A communication device 101A that is mounted on a research vessel and communicates using acoustic signals with a communication target device 102 mounted on an unmanned submersible receives an acoustic signal transmitted from the communication target device 102 over a plurality of channels. A synchronization processing unit 105A obtains a correlation waveform from the acoustic signal received on a channel-by-channel basis using a synchronization reference signal, extracts a reference correlation waveform from the correlation waveform of each channel, and corrects the correlation waveform on the channel-by-channel basis using the reference correlation waveform. A positioning calculation unit 111 calculates three-dimensional positioning.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication device, a communication system, and a communication method. [Background technology]

[0002] Decarbonization requires the use of storage batteries and motors that accompany electrification, and rare metals are required for their manufacture. In the future, the demand for rare metals is expected to accelerate as the trend toward decarbonization spreads. It is believed that abundant rare metal resources lie buried on the ocean floor, and it is hoped that seabed resource exploration will become more precise and efficient.

[0003] In seabed resource exploration, one method is to use an unmanned underwater vehicle to survey the seabed, which is controlled from a research vessel. For communication between the unmanned underwater vehicle and the research vessel, sound waves are used because wired communication would be problematic due to resistance from water pressure, and radio waves cannot propagate far due to scattering and attenuation by water. Among sound waves, frequencies between 5kHz and 50kHz are preferred for long-distance communication because they have low noise and little attenuation in the ocean.

[0004] If a single research vessel could control multiple unmanned underwater vehicles simultaneously, it would lead to more accurate and efficient seafloor resource exploration. However, this would require coordinated control of the unmanned underwater vehicles, which would require constant positioning of the unmanned underwater vehicles. Furthermore, if frequencies between 5 kHz and 50 kHz are to be divided and used, the frequency bands allocated to each unmanned underwater vehicle would be very narrow. Positioning in narrow bands generally results in poor accuracy.

[0005] Known underwater positioning techniques include Patent Document 1 and Patent Document 2. For example, in Patent Document 1, the position of an ROV (Remotely Operated Vehicle) connected to a wired cable is calculated in three-dimensional coordinates from depth information of the ROV, angle information calculated by receiving a signal transmitted from the ROV with two receivers, and distance information calculated from the time difference between transmission and reception. Three-dimensional positioning is possible with two receivers.

[0006] In addition, in Patent Document 2, in order to suppress the effect of multipath during positioning, the received signal is subjected to DFT (Discrete Time Fourier) processing to convert the signal to the frequency axis, and after dividing it by a reference signal, the signal is returned to the time axis through inverse DFT processing. Since the signal is converted to an impulse response by division processing on the frequency axis, this is effective in suppressing noise.

[0007] In both Patent Document 1 and Patent Document 2, the assumption is that positioning will be performed basically by one-to-one wireless communication, and so they do not consider the degradation in accuracy of underwater positioning that occurs due to narrowband caused by frequency allocation to multiple vehicles. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2022-112072 A [Patent Document 2] JP 2020-176902 A Summary of the Invention [Problem to be solved by the invention]

[0009] In the background art, when frequencies are assigned to multiple vehicles, each communication frequency band becomes a narrow band, and the degradation of three-dimensional positioning accuracy caused by the narrow band becomes an issue.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a communication device, a communication system, and a communication method that are capable of achieving high positioning accuracy even when the communication frequency band is narrow. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the above-mentioned object, one embodiment of the present invention is a communication device that communicates with a communication target device using acoustic signals, and is characterized in that it comprises an acoustic receiving unit that receives acoustic signals transmitted from the communication target device on multiple channels, a synchronization processing unit that acquires correlation waveforms from the received acoustic signals for each channel using a pre-prepared synchronization reference signal, extracts reference correlation waveforms from the correlation waveforms, and performs correction of the correlation waveforms for each channel using the reference correlation waveform, and a positioning calculation unit that performs positioning calculations based on the correlation waveforms obtained by the synchronization processing unit.

[0012] Another embodiment of the present invention is a communication system in which communication is performed between a communication target device and a communication device using acoustic signals, wherein the communication target device has an acoustic transmitting unit that transmits acoustic signals to the communication device in a predetermined communication frequency band, and the communication device has an acoustic receiving unit that receives acoustic signals transmitted from the communication target device on multiple channels, a synchronization processing unit that acquires correlation waveforms from the received acoustic signals for each channel using a predetermined synchronization reference signal, extracts reference correlation waveforms from the correlation waveforms, and performs correction of the correlation waveforms for each channel using the reference correlation waveform, and a positioning calculation unit that performs positioning calculations for the communication target device based on the correlation waveforms obtained by the synchronization processing unit.

[0013] Another embodiment of the present invention is a communication method of a communication device that communicates with a communication target device using an acoustic signal, comprising: an acoustic receiving step of receiving an acoustic signal transmitted from the communication target device on multiple channels; a first correlation processing step of acquiring a first correlation waveform from the received acoustic signal for each channel based on a synchronization reference signal prepared in advance; a second correlation processing step of extracting a reference correlation waveform from the first correlation waveforms acquired for each channel and correcting the first correlation waveform acquired for each channel based on the reference correlation waveform to acquire a second correlation waveform; and a positioning calculation step of performing a positioning calculation based on the second correlation waveform acquired for each channel. Effect of the Invention

[0014] According to the present invention, it is possible to provide a communication device, a communication system, and a communication method that are capable of achieving high positioning accuracy even when the communication frequency band is a narrow band. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing an example of the configuration of a communication system according to an embodiment of the present invention; [Figure 2A] 10 is an explanatory diagram showing that angle positioning is performed based on the timing at which a synchronization signal is received by an acoustic receiver in one embodiment of the present invention. FIG. [Figure 2B] FIG. 2 is an explanatory diagram showing the configuration of an audio packet in one embodiment of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram showing a synchronous correlation waveform in a wideband signal according to an embodiment of the present invention. [Figure 4] FIG. 2 is an explanatory diagram showing a synchronous correlation waveform in a narrowband signal according to an embodiment of the present invention. [Diagram 5] FIG. 10 is an explanatory diagram showing a timing misdetection occurring in a synchronous correlation waveform in a narrowband signal according to an embodiment of the present invention. [Figure 6] FIG. 13 is an explanatory diagram showing how false detection is avoided by correlation between channels of synchronous correlation waveforms according to an embodiment of the present invention. [Figure 7A] FIG. 11 is an explanatory diagram showing a spectrum obtained by positioning calculation in a case where erroneous detection is included according to an embodiment of the present invention. [Figure 7B] FIG. 2 is an explanatory diagram showing a spectrum according to one embodiment of the present invention. [Figure 8] 4 is a flowchart illustrating an operation according to an embodiment of the present invention. [Figure 9] FIG. 11 is a block diagram showing an example of the configuration of a communication device when synchronization processing according to another embodiment of the present invention is performed in baseband. [Figure 10A]FIG. 11 is an explanatory diagram showing an example of a synchronization correlation waveform when synchronization processing according to another embodiment of the present invention is performed in baseband. [Figure 10B] 13 is an explanatory diagram showing another example of a synchronization correlation waveform when synchronization processing according to another embodiment of the present invention is performed in baseband. FIG. [Figure 11] 10 is a flowchart illustrating an operation according to a modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following description and drawings are merely examples for explaining the present invention, and appropriate omissions and simplifications have been made in order to clarify the explanation. The present invention can also be implemented in various other forms. Furthermore, unless otherwise specified, each component may be singular or plural.

[0017] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a configuration diagram showing an example of a wireless communication system (hereinafter referred to as a communication system) according to an embodiment of the present invention. In Fig. 1, the communication system of this embodiment is composed of a wireless communication device (hereinafter referred to as a communication device) 101A and a wireless communication target device (hereinafter referred to as a communication target device) 102, for example, as shown in Fig. 1.

[0018] In this communication system, as an example, a survey vessel (mother ship) is equipped with communication device 101A to control multiple unmanned underwater vehicles (autonomous mobile bodies) that conduct marine resource exploration and the like from a single survey vessel, and each unmanned underwater vehicle is equipped with a communication target device 102. In order to control the routes of the multiple unmanned underwater vehicles from the survey vessel, it is necessary for the survey vessel to accurately determine the locations of the multiple unmanned underwater vehicles. To determine the accurate location, as an example, it is assumed that communication device 101A is fixedly installed on the bottom of the survey vessel, where it is easy to receive direct waves.

[0019] In addition, in this communication system, a different frequency is determined in advance and assigned to each unmanned underwater vehicle (communication target device), so the individual communication frequency bands between the communication device and each communication target device are narrowbands. Of course, since the present invention focuses on narrowbands, the number of communication target devices can be as small as one, and in that case, the premise is that the positioning accuracy can be maintained even under narrowband conditions.

[0020] As an example of operation, an example of marine development such as underwater surveys and observations would be a research vessel equipped with communication device 101A for acoustic communication with unmanned underwater vehicles such as AUVs (Autonomous Underwater Vehicles) and UUVs (Unmanned Undersea Vehicles) that are equipped with a communication target device.

[0021] 1, the communication target device 102 includes an acoustic transmitter 103 that transmits an acoustic signal for acoustic communication with the communication device 101A. Other configurations of the communication target device 102 are not shown or described, but the communication target device 102 is assumed to include configurations and functions necessary for acoustic communication and the like for marine development.

[0022] As shown in FIG. 1, communication device 101A has four channels that simultaneously receive and process waves transmitted from acoustic transmitter 103, but the present invention is not limited to this, and the number of channels may be four or less or more than four as long as multiple channels are provided.

[0023] 1, the communication device 101A is configured to support four channels and includes an acoustic receiving unit 104, a synchronization processing unit 105A, a motion estimation unit 112, and a positioning calculation unit 111. The acoustic receiving unit 104 is equipped with acoustic receivers 104a, 104b, 104c, and 104d corresponding to the four channels, and each of them simultaneously receives a transmission (underwater acoustic signal) from the acoustic transmitter 103 and outputs it to the synchronization processing unit 105A. Note that in the synchronization processing unit 105A, a synchronization signal included in the acoustic signal is used as a processing target.

[0024] The synchronous processing unit 105A is composed of a reference signal generator 106A, a reference correlation waveform extraction unit 109, a first correlation processing unit 107 composed of synchronous correlation processing circuits 107a, 107b, 107c, and 107d for four channels, a correlation storage unit 108 composed of correlation storage circuits 108a, 108b, 108c, and 108d, and a second correlation processing unit 110 composed of synchronous correlation processing circuits 110a, 110b, 110c, and 110d.

[0025] The reference signal generator 106A generates a synchronous reference signal in a passband and outputs it to the first correlation processing unit 107. The synchronous correlation processing circuits 107a, 107b, 107c, and 107d process the correlation between the output waveforms of the acoustic receivers 104a, 104b, 104c, and 104d, respectively, and the synchronous reference signal supplied from the reference period signal generator 106, and output the correlation waveforms to the downstream correlation waveform storage circuits 108a, 108b, 108c, and 108d.

[0026] Here, if there is a synchronization signal, the correlation waveform storage circuits 108a, 108b, 108c, and 108d will determine synchronization and obtain a correlation waveform. A correlation waveform refers to the waveform of a synchronization signal (acoustic signal) that can be compared with the correlation results between the synchronization reference signal among the four channels. As a result of this correlation, it can be seen that the channel of the synchronization signal that has a large deviation from the synchronization reference signal is affected by noise, etc.

[0027] The correlation storage circuits 108a, 108b, 108c, and 108d each store a correlation waveform and output it to the downstream synchronous correlation processing circuits 110a, 110b, 110c, and 110d. The correlation storage circuits 108a, 108b, 108c, and 108d also output each correlation waveform to a reference correlation waveform extraction unit 109. The reference correlation waveform extraction unit 109 extracts the correlation waveform that is closest to the waveform of the synchronous reference signal as a reference correlation waveform and outputs it to each correlation storage circuit 108a, 108b, 108c, and 108d.

[0028] The synchronous correlation processing circuits 110a, 110b, 110c, and 110d appropriately correct channels having errors in the reception timing among the correlation waveforms output from the correlation waveform storage circuits 108a, 108b, 108c, and 108d based on the reference correlation waveform output from the reference correlation waveform extraction unit 109, and output the corrected correlation waveforms to the downstream positioning calculation unit 111 and the motion estimation unit 112.

[0029] The motion estimation unit 112 estimates the attitude, etc. of the communication device 101A based on the correlation waveforms output from each of the synchronous correlation processing circuits 110a, 110b, 110c, and 110d to obtain motion data, and outputs the estimation result (motion data) to the positioning calculation unit 111.

[0030] The positioning calculation unit 111 is composed of digital circuits and analog circuits such as a CPU, DSP, memory, and I / O, and calculates three-dimensional positioning based on the estimation result (vibration data) output from the vibration estimation unit 112 and the correlation waveforms output from each synchronous correlation processing circuit 110a, 110b, 110c, and 110d.

[0031] Next, the reception timing will be described with reference to Figures 2A and 2B. Figure 2A is an explanatory diagram showing that angle positioning is performed based on the timing at which a synchronization signal is received by an acoustic receiver in one embodiment of the present invention, and Figure 2B is an explanatory diagram showing the configuration of an acoustic packet in one embodiment of the present invention.

[0032] If the locations of the acoustic receivers 104a, 104b, 104c, and 104d constituting the multiple channels are known, the angular orientation of the communication target device 102 can be determined from the difference in reception timing 201. For the difference in reception timing 201, a synchronization signal 203 of an acoustic communication packet 202 sent from the communication target device 102 is used. As an example of the configuration of the acoustic communication packet 202, the synchronization signal 203 is always at the beginning of the packet, followed by a data signal 204.

[0033] The detection of the reception timing of this synchronization signal 203 is performed by a synchronization processing unit 105A, which is the output destination of the acoustic receiving unit 104 in the communication device 101A. Since the synchronization reference signal is a predetermined signal, the synchronization processing unit 105A first adopts a synchronization reference signal of a reference signal generator 106A as this predetermined signal, and performs correlation processing with the output waveforms of each of the acoustic receivers 104a, 104b, 104c, and 104d in a first correlation processing unit 107.

[0034] The correlation waveforms calculated by the synchronous correlation processing circuits 107a, 107b, 107c, and 107d of the first correlation processing unit 107 depend on the modulation band and the carrier frequency. Here, the carrier frequency of the acoustic signal is a low frequency of 50 kHz or less if the purpose is long-distance communication underwater, so it is quite possible to perform synchronous processing in the passband before frequency conversion.

[0035] Next, an example of a wideband signal will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing a synchronous correlation waveform in a wideband signal according to one embodiment of the present invention. Fig. 3 shows correlation waveforms in each receiving channel when the modulation band is 10 kHz and the carrier frequency is 20 kHz. The signal-to-noise ratio at this time is 20 dB. The peak 301 of the correlation waveform shown by a black dot in each receiving channel is the point where the correlation is maximum, which corresponds to the reception timing of the synchronization signal.

[0036] The acoustic receivers 104 and the acoustic transmitters 103 are arranged in a square shape with intervals of, for example, 25 cm, and the acoustic transmitters 103 are arranged in a direction at an angle of, for example, 10 degrees to the acoustic receivers 104 .

[0037] In this arrangement, the difference 201 in reception timing between reception channels is approximately 0.03 milliseconds. Also, since the modulation band is 10 kHz, the difference 201 between + / - 1 symbols is 0.2 milliseconds. The correlation waveform stored in the correlation storage unit 108 shows that since there is no correlation between adjacent symbols, a large correlation occurs only between + / - 1 symbols, and since the carrier frequency is 20 kHz, a periodic waveform of 0.05 milliseconds is generated.

[0038] Next, an example of a narrowband signal will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing a synchronous correlation waveform in a narrowband signal according to an embodiment of the present invention. Fig. 4 shows a correlation waveform 108A (correlation storage unit 108) when only the modulation band is narrowed from 10 kHz to 4 kHz under the conditions of Fig. 3.

[0039] As can be seen by comparing with Fig. 3, adjacent peaks 401A and 401B are at similar levels to peak 401 of correlation waveform 108A. Under poor noise conditions, the phenomenon in which adjacent peaks 401A and 401B become maximum often occurs, and the timing of adjacent peaks 401A and 401B is erroneously detected as the reception timing of the synchronization signal. When adjacent peaks 401A and 401B are erroneously detected, an error of one wavelength in the carrier frequency occurs as reception timing difference 201, and the angle positioning of acoustic transmitter 103 cannot be performed correctly.

[0040] Next, erroneous detection will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing erroneous timing detection occurring in a synchronous correlation waveform in a narrowband signal according to one embodiment of the present invention. Fig. 5 shows correlation waveforms 108A (correlation storage unit 108) for four channels when the modulation band is narrowed from 10 kHz to 4 kHz, the signal-to-noise ratio of the received signal is reduced from 20 dB to 0 dB, and the received signal is affected by the Doppler effect of a relative speed of 0.1 knots, compared to the conditions in Fig. 3.

[0041] A peak 501 of the correlation waveform is detected at an incorrect timing in reception channel 2. When the angle positioning of the acoustic transmitter 103 is calculated taking into account this incorrect reception timing of reception channel 2, the result is 28 degrees, whereas the correct angle is 10 degrees, resulting in a large error in the angle positioning.

[0042] Here, focusing on the similarity of correlation waveforms 108A (correlation storage unit 108) of receiving channels 1 to 4 in Fig. 5, consider performing a second synchronous correlation process (second correlation processing unit 110) on correlation waveforms 108A (correlation storage unit 108) between channels. The waveforms in Fig. 5 have a characteristically similar waveform in the range of + / -1 symbol, so the waveform in this range is extracted. Here, the range of + / -1 symbol centered on peak 301 of receiving channel 3 is extracted.

[0043] This extracted signal is the reference correlation waveform 109A (reference correlation waveform extraction unit 109), and correlation processing (second correlation processing unit 110) is performed between this reference correlation waveform 109A (reference correlation waveform extraction unit 109) and the correlation waveforms 108A (correlation storage unit 108) of receiving channels 1 to 4.

[0044] The result of this correlation processing (second correlation processing unit 110) is shown in Figure 6. Here, reception channel 3 was selected, but if a channel with good characteristics in terms of modulation accuracy or signal-to-noise ratio can be selected, the effect of noise can be reduced in the correlation processing (second correlation processing unit 110), leading to improved accuracy of the correlation processing.

[0045] Next, the handling of false detection will be explained with reference to Fig. 6, Fig. 7A and Fig. 7B. Fig. 6 is an explanatory diagram showing that false detection is avoided by correlation between channels of synchronous correlation waveforms according to one embodiment of the present invention, Fig. 7A is an explanatory diagram showing a spectrum obtained by positioning calculation in the case where false detection is included according to one embodiment of the present invention, and Fig. 7B is an explanatory diagram showing a spectrum according to one embodiment of the present invention.

[0046] In Fig. 6, peaks 601 in the waveforms of each receiving channel are indicated by black dots as a result of correlation processing (second correlation processing unit 110). It can be seen that the peak 501 due to erroneous detection of receiving timing that occurred in receiving channel 2 in Fig. 5 has been eliminated in Fig. 6.

[0047] That is, the second correlation processor 110 performs peak correction on the channel waveforms with erroneous detection, and it is possible to obtain correlation waveforms at the correct reception timing for all channels. When the positioning calculation (positioning calculation unit 111) is performed using the peak 601 of the waveform detected in Fig. 6 as the reception timing of the synchronization signal, 10 degrees, which is the correct value of the angular orientation of the acoustic transmitter 103, is detected.

[0048] Well-known positioning calculation methods (positioning calculation unit 111) include the MUSIC (Multiple Signal Classification) method and the DBF (Digital Beam Forming) method.

[0049] As an example, spectra obtained by the MUSIC (Multiple Signal Classification) method are shown in Fig. 7A and Fig. 7B. Fig. 7A shows a spectrum of a result 701 of a positioning calculation using a correlation waveform (correlation storage 108) which is the first correlation processing result shown in Fig. 5, and Fig. 7B shows a result 702 of a positioning calculation using a result of a correlation processing (second correlation processing unit 110) which is the second correlation processing result shown in Fig. 6.

[0050] In Figure 7A, the spectrum has a shape with no clear peak, and the positioning calculation result 701 detected as a peak has, for example, 27.6 degrees theta (Θ) and 3.6 degrees phi (Φ) in a spherical coordinate system. In this case, the correct values ​​for both theta and phi are 10 degrees, which shows that the positioning result is significantly erroneous.

[0051] In Figure 7B, the spectrum has a clearly visible peak, and the positioning calculation result 702 detected as the peak has, for example, 9.9 degrees theta and 9.6 degrees phi in the spherical coordinate system, which is very close to the correct value of 10 degrees in this case. The slight deviation from 10 degrees is due to the addition of noise with a signal-to-noise ratio of 0 dB as described in the explanation of Figure 5, and the effect of applying a relative speed of 0.1 knots.

[0052] Since the survey vessel rocks due to the effects of waves on the water surface, the result of the positioning calculation (positioning calculation unit 111) obtained from the output of the second synchronous correlation processing (second synchronous correlation processing unit 110) of the communication device 101A will include the angle caused by this rocking as an error, thereby degrading the positioning accuracy.

[0053] Therefore, in order to suppress errors caused by this fluctuation, an acoustic packet 202 is periodically transmitted from the communication target device 102, and a packet configuration is adopted in which a synchronization signal 203 is interposed. This makes it possible to obtain the results of multiple positioning calculations (positioning calculation unit 111) within one acoustic packet.

[0054] In addition, for synchronization signals transmitted at regular intervals, the relative speed of the acoustic receiving unit 104 of each receiving channel and the communication target device 102 can be calculated based on the Doppler effect from the deviation between the interval of the periodically received synchronization signal and the transmission interval of the synchronization signal determined by the packet configuration. From this relative speed, the vibration generated in the communication device 101A can be estimated (vibration estimation unit 112) and reflected in the positioning calculation (positioning calculation unit 111), thereby improving the positioning accuracy.

[0055] Next, the operation according to this embodiment will be described with reference to Figures 7A, 7B and 8. Figure 7 is a flow chart for explaining the operation according to one embodiment of the present invention. The flow of Figure 8 shows the overall processing of the communication device 101A.

[0056] When a synchronization signal is received on each channel (step S801), a first synchronization correlation process is performed for each channel (step S802), and a synchronization determination is performed to determine whether the peak level of the correlation waveform exceeds a threshold (step S803). As an example of a parameter for performing the determination using this threshold, the ratio of the peak of the synchronization correlation waveform to the average reception level of the signal is adopted.

[0057] While the synchronization signal is not detected, packet dropout is avoided by performing synchronization correlation processing (step S803) at any time. When the synchronization signal is detected, the correlation waveform around the synchronization timing of each channel is stored in the correlation storage unit 108 having the functions of a register and a memory (step S804).

[0058] Next, the modulation accuracy of the synchronization signal of each channel is calculated (step S805). The modulation accuracy can be determined by using a parameter determined by a threshold value when determining synchronization, such as the ratio of the peak of the correlation waveform to the average reception level. In addition, the signal level when the reception signal is received and when it is not received can be converted into the modulation accuracy as a signal-to-noise ratio.

[0059] Using the calculation result of this modulation accuracy, a reference correlation waveform is extracted by using the channel with the best modulation accuracy as the reference channel (step S806). As for the range of the reference correlation waveform extracted in step S806, m+ / -1 symbols is a rough guide because the level of the synchronous correlation waveform decreases in adjacent symbols.

[0060] Next, a second synchronous correlation process is performed between the reference correlation waveform extracted in step S806 and the correlation waveform of each channel stored in the correlation storage unit 108 (step S807). This second correlation process makes it possible to align channels that are synchronously detected at different timings, such as the receiving channel 2 in Fig. 5, to the synchronous detection timing of the reference correlation waveform.

[0061] An example of the correlation waveform of each channel in this second synchronization correlation process is as shown in Fig. 6. By extracting the peak of the correlation waveform obtained by the second synchronization correlation process, synchronization timing under the same conditions is obtained for each channel (step S808). By performing positioning calculation using this synchronization timing, it is possible to avoid the occurrence of errors such as those shown in spectrum 701 in Fig. 7A, and to obtain the correct positioning result shown in spectrum 702 in Fig. 7B.

[0062] However, when the communication device 101A is mounted on a vehicle that is subject to motion, such as a research vessel, the positioning calculation result (step S809) itself is affected by the motion. As a countermeasure to this, a synchronization signal 203 can be periodically provided at a fixed timing, as shown in the acoustic packet 202 in Fig. 2, so that the transition of the Doppler effect of each channel can be observed, and the motion of the vehicle can be estimated (step S810). The estimated motion is used to correct the positioning result in step S809 (step S811), thereby obtaining a positioning result in which the effect of motion is suppressed, and a highly accurate measurement result can be output to the outside (step S812).

[0063] As described above, according to the above-mentioned embodiment, even if the communication frequency band becomes narrow in acoustic communication between the communication target device and the communication device, it is possible to achieve high three-dimensional positioning accuracy by performing two correlations using a synchronization signal.

[0064] Next, another embodiment of the present invention will be described with reference to Fig. 9, Fig. 10A, and Fig. 10B. Fig. 9 is a block diagram showing a configuration example when synchronization processing according to another embodiment is performed in baseband, Fig. 10A is an explanatory diagram showing an example of a synchronization correlation waveform when synchronization processing according to another embodiment of the present invention is performed in baseband, and Fig. 10B is an explanatory diagram showing another example of a synchronization correlation waveform when synchronization processing according to another embodiment of the present invention is performed in baseband.

[0065] As shown in Fig. 9, in comparison with the communication device 101A, the communication device 101B in another embodiment includes a carrier multiplication unit 701 composed of carrier multiplication circuits 701a, 701b, 701c, and 701d corresponding to four channels, and the synchronization processing unit 105B performs synchronization processing using a baseband synchronization reference signal. The synchronization processing unit 105B differs from the reference signal generator 106A in the above embodiment in that a baseband synchronization reference signal is generated from the reference signal generator 106B. Note that the same reference symbols are used for the same components as those in Fig. 1, and detailed description thereof will be omitted.

[0066] In this other embodiment, the carrier multiplication unit 701 converts the frequency of the output of the acoustic receiving unit 104 from the passband to the baseband, and then the synchronization processing unit 105B performs synchronization processing. In this way, the use of a synchronization reference signal in the baseband as a reference signal and the processing are different from the above-mentioned embodiment.

[0067] Correlation waveform 108A (correlation storage unit 108) is drawn as the envelope of the waveform shown in Fig. 3 and Fig. 4 because there is no influence of the carrier frequency. The synchronization accuracy and the frequency of erroneous detection of reception timing are the same as in the passband synchronization processing of Fig. 1.

[0068] Also, as an effect of avoiding erroneous detection of reception timing due to the second correlation process (second correlation processor 110), the same effect as in the case of the passband in FIG. 1 can be obtained.

[0069] The correlation waveforms obtained in the baseband are shown in Figures 10A and 10B. In the case of Figure 10A, the correlation waveforms in each receiving channel are shown for an example in which the modulation band is 10 kHz and the carrier frequency is 20 kHz, and the waveforms correspond to the envelopes in Figure 3.

[0070] In the case of Fig. 10B, correlation waveforms in each receiving channel are shown for an example where the modulation band is 4 kHz and the carrier frequency is 20 kHz, and the waveforms correspond to the envelopes in Fig. 4. Peaks 1001A and 1001B detected in each channel are also given at the same positions as peaks 301 and 401 in Figs. 3 and 4, respectively.

[0071] In this way, in other embodiments, it is possible to obtain the same effects as in the above-described embodiment.

[0072] Furthermore, in the two embodiments described above, if the relative positions of the communication devices 101A and 101B and the communication target device 102 do not change within the time of the acoustic packet, there is a method of averaging a plurality of positioning results obtained within a predetermined time (predetermined time). Therefore, a modified example of the operation will be described below with reference to Fig. 11. Fig. 11 is a flowchart for explaining the operation according to the modified example of the embodiment described above.

[0073] Regarding the communication process, the processes from step S801 to step S811 are executed similarly to the operation in Fig. 8 (step S1101), and when the fluctuation correction is completed, the positioning result is temporarily stored in the positioning calculation unit 111 (1102). The positioning calculation unit 111 checks the passage of a predetermined time by measuring time. Since steps S1101 and S1102 are repeated many times until the predetermined time has passed, a plurality of positioning results are obtained and stored (NO route of step S1103).

[0074] Then, after a predetermined time has elapsed (step S1103), an average is calculated based on all stored positioning results, and an average positioning result is obtained (step S1104). This average positioning result is output as an output target (step S1106).

[0075] By performing the above process at a predetermined time interval, the positioning accuracy can be improved.

[0076] The present invention is not limited to the above-described embodiments, but includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to an embodiment having all of the configurations described. In addition, it is possible to replace a part of the configuration of this embodiment with another configuration, and it is also possible to add another configuration to a certain configuration. In addition, it is possible to add, delete, or replace a part of the configuration of this embodiment with another configuration.

[0077] In each of the above-described embodiments, an example is given of acoustic communication technology in marine development using mobile bodies such as AUVs and UUVs, in which a single research vessel (communication device) performs 3D positioning of multiple unmanned underwater vehicles (communication target devices). However, the present invention is not limited to this, and since highly accurate 3D positioning can be achieved when the communication frequency band is narrow, it goes without saying that the communication system can also be configured with one unmanned underwater vehicle for one research vessel, i.e., with one communication target device.

[0078] Needless to say, this technology can also be applied to simultaneous and group control of multiple unmanned robots and unmanned aerial vehicles based on 3D positioning technology, regardless of whether they are in the air, on land, on water (including on lakes and seas), or underwater (including under lakes and seas). In particular, it is useful from an industrial perspective for use in communications between fishing boats at sea, resource exploration and various construction projects at sea, as well as in government and private business sectors that require the safety of land, sea (including water areas), and air.

[0079] Furthermore, in each of the above-described embodiments, an acoustic signal is given as an example of wireless communication, but the present invention is not limited to this, and a radio wave signal may also be used. [Explanation of symbols]

[0080] 1. Wireless communication systems 101A Communication equipment 101B Communication equipment 102 Communication target device 103 Acoustic Transmitter 104 Acoustic receiving unit 104a acoustic receiver 104b Acoustic receiver 104c acoustic receiver 104d acoustic receiver 105A Synchronization processing section 105B Synchronization processing section 106A Reference Signal Generator 106B Reference Signal Generator 107 First correlation processor 107a Synchronous correlation processing circuit 107b Synchronous correlation processing circuit 107c Synchronous correlation processing circuit 107d Synchronous correlation processing circuit 108 Correlation Storage Unit 109 Reference correlation waveform extraction unit 110 Second correlation processor 110a Synchronous correlation processing circuit 110b Synchronous correlation processing circuit 110c Synchronous correlation processing circuit 110d Synchronous correlation processing circuit 111 Positioning Calculation Unit 112 Motion Estimation Unit 701 Carrier multiplication unit 701a Carrier multiplication circuit 701b Carrier multiplication circuit 701c Carrier multiplication circuit 701d Carrier multiplication circuit

Claims

1. A communication device that communicates with a communication target device using an acoustic signal, an acoustic receiving unit that receives acoustic signals transmitted from the communication target device through a plurality of channels; a synchronization processing unit that acquires correlation waveforms from the received acoustic signals for each of the channels using a synchronization reference signal prepared in advance, extracts a reference correlation waveform from the correlation waveforms, and corrects the correlation waveform for each of the channels using the reference correlation waveform; a positioning calculation unit that performs positioning calculation based on the correlation waveform obtained by the synchronization processing unit; A communication device comprising:

2. 2. The communication device according to claim 1, wherein the synchronization processing unit detects a peak of a correlation waveform for each of the channels and corrects an error in reception timing of the acoustic signal based on the detected peak.

3. 2. The communication device according to claim 1, wherein periodic communication is performed with the communication target device, and the positioning calculation unit obtains the positioning result by averaging the results of the positioning calculation obtained for each periodic communication.

4. 2. The communication device according to claim 1, wherein the communication device performs periodic communication with the communication target device, calculates a relative speed between the acoustic receiving unit and the communication target device according to an interval at which an acoustic signal is received from the periodic communication, estimates a vibration of the communication device itself based on the calculated relative speed to obtain vibration data, and performs positioning calculations in the positioning calculation unit based on the vibration data obtained by the estimation.

5. 2. The communication device according to claim 1, wherein the correlation waveform obtained by the synchronization processing unit is a synchronization signal contained in the acoustic signal.

6. A communication system for performing communication between a communication target device and a communication device using an acoustic signal, the communication target device includes an acoustic transmission unit that transmits an acoustic signal to the communication device in a predetermined communication frequency band; The communication device includes: an acoustic receiving unit that receives acoustic signals transmitted from the communication target device through a plurality of channels; a synchronization processing unit that acquires correlation waveforms from the received acoustic signals for each of the channels using a synchronization reference signal prepared in advance, extracts a reference correlation waveform from the correlation waveforms, and corrects the correlation waveform for each of the channels using the reference correlation waveform; a positioning calculation unit that performs positioning calculation of the target device based on the correlation waveform obtained by the synchronization processing unit; A communication system comprising:

7. 7. The communication system according to claim 6, wherein communication is performed between one of the communication devices and a plurality of the communication target devices, and wherein different communication frequency bands are pre-assigned to each of the communication target devices, and the communication device communicates with each of the communication target devices using the different communication frequency bands.

8. 8. The communication system according to claim 7, wherein said communication device is mounted on a survey vessel, and each of said communication target devices is mounted on a different unmanned underwater vehicle.

9. A communication method for a communication device that communicates with a communication target device using an acoustic signal, comprising: an acoustic receiving step of receiving an acoustic signal transmitted from the communication target device through a plurality of channels; a first correlation processing step of acquiring a first correlation waveform from the received acoustic signal for each channel based on a synchronization reference signal prepared in advance; a second correlation processing step of extracting a reference correlation waveform from the first correlation waveforms acquired for each channel, and correcting the first correlation waveforms acquired for each channel based on the reference correlation waveform to acquire a second correlation waveform; a positioning calculation step of performing a positioning calculation based on the second correlation waveform acquired for each channel; A communication method comprising:

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