JP4622548B2 - Underwater acoustic transmission method and underwater acoustic transmission apparatus - Google Patents

Description

  The present invention relates to an underwater acoustic transmission method and an underwater acoustic transmission device for transmitting data using underwater acoustics between two points located in water. In particular, the present invention relates to an underwater acoustic transmission method and an underwater acoustic transmission apparatus that can be used even in shallow water.

In general, underwater sound is used for data transmission in water. For data transmission using underwater acoustics in a shallow sea area, reverberation caused by reflection and scattering of sound waves generated at the boundary surface of a medium such as the sea floor or the sea surface is a major obstacle.
When the transmitter transmits underwater sound in the water, the underwater sound propagated to the surroundings is repeatedly reflected on the seabed or the sea surface, and reverberation continues for a predetermined time.
In order to avoid the effects of reverberation, intermittent transmission can be performed in which data transmission is performed intermittently only in a time period in which the sound level of reverberation is hidden by background noise, and transmission is suspended in other time periods. .
In addition, the occurrence of reverberation varies depending on the geometrical positional relationship between the transmission point, reception point, and the surrounding environment, the directivity of the transmitter / receiver, the acoustic frequency used, etc. Even if it is possible, errors may occur frequently and data transmission may not be possible.

Conventionally, in order to avoid the influence of this reverberation, a guard time is set between one data transmission and the next data transmission, and data is intermittently waited until the acoustic level of the reverberation falls below a predetermined value. Was transmitting. The operator determined this guard time empirically.
In this case, MFSK (multi frequency shift keying), DPSK (differential phase shifting keying), etc., which are suitable for short signal reception and do not require carrier wave synchronization on the receiving side, are used.
Also, since the guard time between one data transmission and the next data transmission is fixed, even if the positional relationship between the transmission point and the reception point changes in a direction advantageous for data transmission, the transmission efficiency cannot be improved. It was.
Further, since the modulation method is MFSK or DPSK, the transmission speed is limited, and the amount of transmission information cannot be increased more than now.

JP-A-9-55707 JP 2000-206228 A The state of the art in underwater acoustic telemetry, “Oceanic Eng.”, Vol. 25, Nо. 1, IEEE J, January 2000, p. 4-27

  The present invention has been devised in view of the above-described problems, and can be applied to changes in the state of the sea area with a simple configuration, and can perform underwater acoustics between a first point and a second point located in water. An underwater acoustic transmission method and an underwater acoustic transmission device for transmitting data using the same are provided.

  In order to achieve the above object, an underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water according to the present invention, the first point and the second point A test transmission step for transmitting a pulsed test transmission sound on one side, and a test reception step for receiving a test reception sound generated by propagation of the test transmission sound in water on the other of the first point and the second point. And the actual transmission step of transmitting the first transmission sound having the first signal length Ts1 obtained by modulating the data at the first point, and the first transmission sound propagated in water at the second point. A reception step of receiving the received sound and extracting the first transmission sound from the received sound and demodulating it to obtain data, wherein the first signal length Ts1 is on the time axis of the test received sound. Is located between the direct wave of the test transmission sound and the reverberation wave that appears next to the direct wave. Shorter than the first hour length T1 is the time length of the time zone, and the things.

  According to the configuration of the present invention, one of the first point and the second point transmits a pulsed test transmission sound, and the other of the first point and the second point propagates the test transmission sound in water. And the first signal length Ts1 is located between the direct wave of the test transmission sound and the reverberation wave appearing next to the direct wave on the time axis of the test reception sound. A first transmission sound having a first signal length Ts1 which is shorter than the first time length T1 which is the time length of the first time zone and which is obtained by modulating data at the first point is transmitted. Since the first transmission sound is received through the underwater and the received sound is received and the first transmission sound is extracted from the received sound and demodulated to obtain data, the first transmitted at the first point is obtained. The transmitted sound is received at the second point without overlapping the reverberant wave, and the first transmitted sound can be easily extracted from the received sound. It can be less data transmission error between the first point and the second point.

  In order to achieve the above object, the underwater acoustic transmission device for transmitting data using the underwater sound between the first point and the second point located in the water according to the present invention transmits the underwater sound at the first point. A first data transmission device capable of receiving, and a second data transmission device capable of transmitting and receiving underwater sound at a second point, comprising: a first data transmission device and a second data transmission device; One of them transmits a pulsed test transmission sound, and the other of the first data transmission device and the second data transmission device receives a test reception sound generated by propagation of the test transmission sound in water, Received sound generated by one data transmission apparatus transmitting a first transmission sound having a first signal length Ts1 obtained by modulating data and a second data transmission apparatus propagating through the first transmission sound in water And receiving the first transmitted sound from the received sound. Are extracted and demodulated to obtain data, and the first signal length Ts1 is located between the direct wave of the test transmission sound and the reverberation wave appearing next to the direct wave on the time axis of the test reception sound. It was assumed to be shorter than the first time length T1, which is the time length of the first time zone.

  According to the configuration of the present invention, the first data transmission device can transmit and receive underwater sound at the first point, and the first data transmission device can transmit and receive underwater sound at the second point. Test reception sound generated by transmitting pulsed test transmission sound in one of the first point and the second point and propagating the test transmission sound in water at the other of the first point and the second point And the first signal length Ts1 is a time in a first time zone located between the direct wave of the test transmission sound and the reverberation wave appearing next to the direct wave on the time axis of the test reception sound. A first transmission sound having a first signal length Ts1, which is shorter than a first time length T1 which is a length and obtained by modulating data at a first point, is transmitted, and the first transmission sound is transmitted at a second point. Receives the received sound generated by propagating in the water, extracts the first transmitted sound from the received sound, and recovers it. Thus, the first transmission sound transmitted at the first point is received at the second point without overlapping the reverberation wave, and the first transmission sound can be easily extracted from the received sound. Data transmission with few errors can be performed between the first point and the second point.

As described above, the underwater acoustic transmission method and the underwater acoustic transmission apparatus for transmitting data using the underwater sound between the first point and the second point located in the water according to the present invention have the following configuration. Has an effect.
First, a pulsed test sound is transmitted on the one hand, and a test sound is received on the other hand, and the first time length T1 of the first time zone with a small reverberation between the direct wave and the next reverberating wave is set. Thus, the first signal length Ts1 shorter than T1 is determined, and the first transmission sound having Ts1 at the first point is transmitted in the actual transmission. Therefore, the first transmission sound transmitted at the first point is the reverberation wave. The first transmission sound can be easily extracted from the received sound, and data transmission with less errors can be performed between the first point and the second point.
Accordingly, an underwater acoustic transmission method and an underwater acoustic transmission device that can be applied to changes in the state of the sea area with a simple configuration and transmit data using underwater acoustics between a first point and a second point located in water. Can provide.

  Several embodiments of the underwater acoustic transmission method according to the present invention will be described below. The present invention includes a mode in which any of the embodiments described below or two or more of them are combined.

The underwater acoustic transmission method according to the embodiment of the present invention is obtained by modulating data after elapse of a first guard time Tn1 after the actual transmission step transmits the first transmission sound at the first point. A second transmission sound having a signal length Ts2 is transmitted, and the actual reception step receives a reception sound generated by propagation of the first transmission sound and the second transmission sound in water at the second point. The first transmission sound and the second transmission sound are extracted from the sound and demodulated to obtain data, and the second signal length Ts2 is the first signal length Ts1 on the time axis. The first sound level L1 is maintained after the first guard time Tn1 elapses after the direct wave of the test transmission sound superimposed in the virtual reception sound obtained by superimposing while moving backward. Second time length, which is the length of time in two hours Shorter than T2, the sound level L1 is level that can be demodulated data from the received acoustic at the second point.
According to the configuration of the above embodiment, the second signal length Ts2 is superimposed on the virtual reception sound obtained by superimposing the test reception sound while moving backward on the time axis by the first signal length Ts1. Shorter than a second time length T2 that is a time length of a second time zone that is located after the first guard time Tn1 elapses after the direct wave of the first transmission sound and maintains the sound level equal to or lower than the sound level L1, Second signal length obtained by modulating data after elapse of the first guard time Tn1 after transmitting the first transmission sound having the first signal length Ts1 obtained by modulating data at the first point. A second transmission sound having Ts2 is transmitted, and a reception sound generated by propagation of the first transmission sound and the second transmission sound in water at a second point is received, and the first transmission is received from the reception sound. The sound and the second transmission sound are extracted and demodulated. The second transmission sound transmitted at the first point is received at the second point without overlapping the reverberation wave, and the first transmission sound and the second transmission sound are extracted from the received sound. It is easy to perform data transmission with less errors between the first point and the second point.

In the underwater acoustic transmission method according to the embodiment of the present invention, the modulation / demodulation method is the OFDM method, and the first time length Ts1 is an integer multiple of the unit symbol time length Ts.
According to the configuration of the above embodiment, since the first signal length Ts1 is an integral multiple of the time length Ts of the unit symbol of the OFDM system, the first time length T1 is shorter than the first signal length Ts1. Unless reverberation overlaps the unit symbols, data transmission with less error can be performed between the first point and the second point.

In the underwater acoustic transmission method according to the embodiment of the present invention, the modulation / demodulation method is an OFDM method, and at least one of the plurality of carriers transmitted by the actual transmission step is a specific carrier, and the amplitude value of the specific carrier is calculated. The fixed value is fixed, and the amplitude value of the specific carrier wave received by the actual reception step is used as a reference amplitude value to remove the influence of sound level attenuation from the amplitude of each of the plurality of carrier waves.
With the configuration of the above embodiment, the amplitude width of the specific carrier wave of the first transmission sound to be transmitted at the first point is fixed, and is specified from the amplitude of each carrier wave of the first transmission sound in the reception sound received at the second point. Since the influence of the attenuation of the sound level is removed using the amplitude value of the carrier wave, even if the sound pressure of the first transmission sound extracted from the received sound received at the second point is greatly attenuated, the first point and the first point Data transmission with few errors can be performed between the two points.

In the underwater acoustic transmission method according to the embodiment of the present invention, when the position of the first point or the position of the second point in water changes beyond a predetermined range, the test transmission step and the test reception step are performed. A test transmission update process is performed again to update the test reception sound with the new test reception sound,
Prepare.
With the configuration of the above embodiment, when the position of the first point or the position of the second point in water changes beyond a predetermined range, the test transmission step and the test reception step are performed again to perform the test. Since the received sound is updated with the new test received sound, the new first signal length Ts1 can be determined according to the change in the first time length T1.

The underwater acoustic transmission method according to the embodiment of the present invention repeats the test transmission step and the test reception step again when the occurrence of errors increases in the demodulation of data in the actual reception step. A test transmission updating step for updating with new test reception sound is provided.
With the configuration of the above embodiment, when the occurrence of errors increases in data demodulation in the actual reception step, the test transmission step and the test reception step are repeated again to make the test reception sound a new test reception sound. Therefore, even when a situation occurs in which the first time length T1 becomes shorter than the first signal length Ts1 and reverberation overlaps with the first transmission sound, the first time length T1 responds to the change in the first time length T1. Thus, the new first signal length Ts1 can be determined.

  Several embodiments of the underwater acoustic transmission apparatus according to the present invention will be described below. The present invention includes a mode in which any of the embodiments described below or two or more of them are combined.

The underwater acoustic transmission device according to the embodiment of the present invention is a second signal length obtained by modulating data after elapse of a first guard time Tn1 after the first data transmission device transmits the first transmission sound. A second transmission sound having a length Ts2, and the second data transmission device receives a reception sound generated by propagation of the first transmission sound and the second transmission sound in water. The first transmission sound and the second transmission sound are extracted and demodulated to obtain data, and the second signal length Ts2 moves the test reception sound backward by the first signal length Ts1 on the time axis. However, in the second time zone that is located after the first guard time Tn1 has elapsed after the direct wave of the test transmission sound superimposed in the virtual reception sound obtained by superimposing, and maintains the sound level equal to or lower than the sound level L1. Second time length T which is time length Shorter, the sound level L1 is level that can be demodulated data from the received acoustic at the second point.
According to the configuration of the above embodiment, the second signal length Ts2 is superimposed on the virtual reception sound obtained by superimposing the test reception sound while moving backward on the time axis by the first signal length Ts1. Shorter than a second time length T2, which is a time length of a second time zone that is located after the first guard time Tn1 elapses after the direct wave of the test transmission sound and maintains the sound level equal to or lower than the sound level L1, Transmitting a second transmission sound having a second signal length Ts2 obtained by modulating data after elapse of the first guard time Tn1 after transmitting the first transmission sound at one point, The first transmission sound and the second transmission sound are received through the underwater and the received sound is generated. The first transmission sound and the second transmission sound are extracted from the received sound and demodulated to obtain the data. Because you get
The second transmission sound transmitted at the first point is received at the second point without overlapping the reverberant wave, and the first transmission sound and the second transmission sound can be easily extracted from the reception sound. It is possible to transmit data with less errors between the first point and the second point.

In the underwater acoustic transmission device according to the embodiment of the present invention, the modulation / demodulation method of the first data transmission device and the second data transmission device is an OFDM method, and the first signal length Ts1 is a unit symbol time length. It is an integer multiple of Ts.
According to the configuration of the above embodiment, since the first signal length Ts1 is an integral multiple of the time length Ts of the unit symbol of the OFDM system, the first time length T1 is shorter than the first signal length Ts1. Unless reverberation overlaps the unit symbols, data transmission with less error can be performed between the first point and the second point.

In the underwater acoustic transmission device according to the embodiment of the present invention, the modulation / demodulation method of the first data transmission device and the second data transmission device is an OFDM method, and among the plurality of carriers transmitted by the first data transmission device The amplitude of each of the plurality of carriers is determined by using at least one of the specific carriers as an amplitude value and fixing the amplitude value of the specific carrier to a constant value and using the amplitude value of the specific carrier received by the second data transmission apparatus as a reference amplitude value. Remove the effects of sound level attenuation from
With the configuration of the present embodiment, at least one of the plurality of carriers transmitted at the first point is a specific carrier, the amplitude value of the specific carrier is fixed to a constant value, and the received sound received at the second point Since the influence of the attenuation of the sound level is removed from the amplitude of each carrier wave of the first transmission sound, the sound pressure of the first transmission sound extracted from the reception sound received at the second point is greatly attenuated. Even in such a case, data transmission with few errors can be performed between the first point and the second point.

The underwater transmission device according to the embodiment of the present invention, when the position of the first point or the second point in water changes beyond a predetermined range, the first data transmission device and the second data transmission device One of them transmits the pulsed test transmission sound again, and the other of the first data transmission device and the second data transmission device receives again the test reception sound generated when the test transmission sound propagates in water. The test reception sound is updated with the new test reception sound.
With the configuration of the above embodiment, when the position of the first point or the position of the second point in water changes beyond a predetermined range, the transmission of the test transmission sound and the reception of the test reception sound are performed again. Since the test reception sound is updated with the new test reception sound, the new first signal length Ts1 can be determined according to the change in the first time length T1.

In the underwater transmission apparatus according to the embodiment of the present invention, when the occurrence of errors increases in the demodulation of data in the actual reception process, one of the first data transmission apparatus and the second data transmission apparatus is a pulsed test. The transmission sound is transmitted again, and the other of the first data transmission device and the second data transmission device receives again the test reception sound generated when the test transmission sound propagates in water, and the test reception sound is newly transmitted. Update with the test reception sound.
With the configuration of the above embodiment, when the occurrence of errors increases in data demodulation in the actual reception process, the test transmission sound and the test reception sound are received again, and the test reception sound is renewed. Even if the first time length T1 is shorter than the first signal length Ts1 and reverberation overlaps the first transmission sound, the first time length is updated. The new first signal length Ts1 can be determined according to the change in T1.

The underwater transmission device according to the embodiment of the present invention is a method in which the modulation / demodulation method of the first transmission device and the second transmission device uses a plurality of carriers, and the first data transmission device is located at the first point. It has a plurality of transmitters that radiate sound in water, and the resonance frequency of each of the plurality of transmitters substantially matches the frequency of each of the plurality of carrier waves.
With the configuration of the above-described embodiment, the resonance frequency of each of the plurality of transmitters and the carrier frequency of each of the plurality of carrier waves substantially coincide with each other, so that efficient transmission can be performed over the entire frequency band.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

Initially, the underwater acoustic transmission apparatus 1 which concerns on 1st embodiment of this invention is demonstrated based on a figure.
FIG. 1 is a configuration diagram of an underwater acoustic transmission apparatus according to an embodiment of the present invention. FIG. 2 is a first configuration diagram of the data transmission apparatus according to the embodiment of the present invention.

The underwater sound transmission device is a device that transmits data using underwater sound between a first point and a second point located in water, and includes a first data transmission device 10 and a second data transmission device 20. Composed.
The first data transmission device 10 is a device that can transmit and receive underwater sound at a first point P1. For example, the first data transmission device 10 transmits an acoustic signal obtained by modulating data input from the information source 30 underwater.
The second data transmission device 20 is a device that can transmit and receive underwater sound at the second point P2. For example, the second data transmission device 20 outputs data obtained by demodulating the received acoustic signal to the information terminal 40.

In general, the first data transmission device 10 and the second data transmission device 20 can transmit and receive bidirectionally, and thus have the same configuration. The configuration of the first data transmission device 10 and the second data transmission device 20 will be described with the configuration of the first data transmission device 10.
The first data transmission device 10 includes a communication controller 11, a modulator 12, a transmitter 13, a transmitter 14, a demodulator 15, a receiver 16 and a receiver 17.
The communication controller 11 is a device that exchanges data with the outside.
The modulator 12 is a device that modulates data to be transmitted provided from the communication controller 11 into a signal waveform.
The transmitter 13 is a device that converts the output of the modulator 12 into an acoustic signal,
The transmitter 14 is an element that converts an acoustic signal and radiates acoustic energy into water.
In general, the combination of the transmitter 13 and the transmitter 14 is called a projector, and is a resonance type having a resonance frequency with high output efficiency.
The wave receiver 17 is an element that converts acoustic energy received from underwater into an acoustic signal.
The receiver 16 is a device that inputs an acoustic signal to the demodulator 15 as an input signal.
The demodulator 15 is a device that demodulates an input signal and outputs data to the communication controller 11.

In general, the combination of the receiver 17 and the receiver 16 is called a transducer.

Next, a case where underwater sound is transmitted from the first point P1 to the second point P2 using the first data transmission device 10 and the second data transmission device 20 will be described with reference to the drawings.
FIG. 3 is an acoustic propagation diagram of the underwater acoustic transmission method according to the embodiment of the present invention. FIG. 4 is a reverberation pattern diagram of the underwater acoustic transmission method according to the embodiment of the present invention. FIG. 5 is an explanatory diagram of the utilization time of the underwater acoustic transmission method according to the embodiment of the present invention.
Generally, the sea area is distinguished into a shallow sea area that is shallower than the continental shelf and a deep sea area that is deeper than the continental shelf. It is known that the presence of the sea surface S and the seabed B cannot be ignored when data is transmitted using underwater acoustics in shallow water.
The main propagation paths from the transmission point of the sound wave to the reception point in the shallow sea area are the direct propagation path Z0 and the sea bottom / sea surface reflection paths Z1, Z2,. Here, the seabed / sea surface reflection path having m as the number of sea surface reflections in the propagation path and n as the number of sea bottom reflections is referred to as (m, n) path. The direct propagation path Z0 is called a (0, 0) path. Therefore, the seabed / sea surface reflection path in which one of the sea surface reflection and the sea bottom reflection is one time is referred to as a (0, 1) path and a (1, 0) path. The sea bottom / sea surface reflection path that is one time each of the sea surface reflection and the sea bottom reflection is called a (1, 1) path.

FIG. 3 shows a state of the (0, 0) path Z0, the (0, 1) path Z2, and the (1, 0) path Z1.
FIG. 4 schematically shows the acoustic waveform of the received sound YY received at the second point (reception point) P2 when a single-pulse acoustic wave of the carrier frequency fp is transmitted from the first point (transmission point) P1. Indicate.
First, the sound Y0 passing through the (0, 0) path is received, and then the sounds Y1, Y2 passing through the (1, 0) path and the (0, 1) path are received, and the (1, 1) bus. Sounds Y3 and Y4 that have passed through are received, and sound that has passed through a path in which the sum of m and n is large is received.
In general, the sound Y0 ′ is called a direct wave, and the received sounds after the sounds Y1 and Y2 are called reverberant waves.
As the propagation path length increases, the delay time increases and the absorption loss of sound into seawater increases. As the number of reflections on the sea surface or the sea floor increases, the sea surface reflection loss and the sea floor reflection loss of the reverberant wave increase. The acoustic level of the reverberant wave decreases exponentially as the delay time increases.
The attenuation of the sound level due to absorption loss varies greatly with the carrier frequency. In addition, the attenuation of the sound level due to the sea surface reflection loss and the sea floor reflection loss varies greatly depending on the level of the sea surface waves and the bottom sediment.

In the received sound YY shown in FIG. 4, the sound level of the sound Y0 ′ (direct wave) of the (0, 0) path is referred to as L0.
The first time length T1 is a delay time from the reception of the sound Y0 ′ (direct wave) via the (0, 0) path to the reception of the first reverberation wave.
The sound level L1 is a sound level of a reverberation wave that allows the data transmission apparatus to extract a significant reverberation wave from the received sound.
The time length T0 is the time from when the direct wave is received until the acoustic level of the reverberant wave falls to the acoustic level L1.
If only the first time length T1 is used for data transmission in the time length T0, T1 / T0 is referred to as a utilization time rate for data transmission.

η = T1 / T0 ----------- Formula (1)

Next, a use time (theoretical first time length) T1 ′ when the first point P1 and the second point P2 are in a shallow sea area is estimated.
FIG. 5 shows how sound propagates from the first point P1 to the second point P2 via the (0, 0) path and the (1, 0) path.

T1 ′ = {[(y1 + y2) ² + x1 ² ] ^1/2 − [(y1−y2) ² + x1 ² ] ^1/2 } / c
------- Formula (2)

here,
The first depth y1 is the depth of the first point P1 (transmission point).
The second depth y2 is the depth of the second point P2 (reception point).
The horizontal distance x1 is a horizontal distance between the first point P1 and the second point P2.
c is the speed of sound.
Therefore, when y1 or y2 approaches 0, the usage time T1 ′ approaches 0, and the usage time rate η also approaches 0. A similar phenomenon occurs when y1 or y2 approaches the sea. From this, it can be seen that in order to increase the utilization time rate, it is desirable to install the first point P1 and the second point P2 at a position about one-half of the water depth.

Below, the 1st underwater acoustic transmission method which concerns on embodiment of this invention is demonstrated based on a figure for the case where the 1st underwater acoustic transmission which concerns on embodiment of this invention is used as an example.
FIG. 6 is a flowchart of the underwater acoustic transmission method according to the embodiment of the present invention. FIG. 7 is a sequence diagram of the underwater acoustic transmission method according to the embodiment of the present invention. FIG. 8 is an acoustic chart diagram 1 of the underwater acoustic transmission method according to the embodiment of the present invention.
The underwater acoustic transmission method is a method of transmitting data using underwater acoustics between a first point P1 and a second point P2 located in water, and includes a test transmission step S10, a test reception step S20, and a parameter determination step. It consists of S30, production transmission step S40, production reception step S50, and test transmission update step S60.

The test transmission step S10 is a step of transmitting a pulsed test transmission sound at one of the first point and the second point.
Hereinafter, a case where pulsed test transmission sound is transmitted at the first point P1 will be described as an example.
The first data transmission device 10 transmits the test transmission sound Y0 at the first point P1.
The test transmission signal Y0 may be a short-time sound on a single frequency carrier wave.
For example, the test transmission sound is a sound having a frequency of 10 KHz to 100 KHz having a rectangular envelope.
The frequency is determined in consideration of acoustic attenuation due to the distance between the first point P1 and the second point P2.

The test reception step S20 is a step of receiving the test reception sound YY generated by the test transmission sound Y0 propagating in water at the other of the first point and the second point.
Hereinafter, a case where the test reception sound is received at the second point P2 will be described as an example.
The second data transmission device 20 receives the test reception sound YY at the second point P2.
The test reception sound YY is sound generated by propagation of the test transmission sound Y0 in water, and includes a direct wave Y0 and reverberation waves Y1, Y2, Y3, Y4,.

The parameter determination step S30 is a step of determining parameters to be used in an actual transmission step S40 and an actual reception step S50 described later based on the results of the test transmission step S10 and the test reception step S20.
The parameters are various numerical values used for modulation / demodulation in order to transmit data using underwater sound as a transmission medium.
One or both of the first data transmission device 10 and the second data transmission device 20 may perform the parameter determination step S30.
The parameter determination step S30 includes a parameter estimation step S31, a parameter transmission step S32, an ACK signal transmission step S33, and a CONFIRM signal transmission step S34.
Below, the case where the 2nd data transmission apparatus 20 estimates a parameter and sends a parameter to the 1st data transmission apparatus 10 is demonstrated to an example.

The parameter estimation step S31 is a step of analyzing the test reception sound YY and estimating parameters necessary for transmission.
The second data transmission device 20 estimates the first signal length Ts1 and the first guard time Tn1 from the test reception sound YY.
The first signal length Ts1 is shorter than the first time length T1.
The first time length T1 is located between the direct wave Y0 ′ of the test transmission sound Y0 and the reverberation wave Y1 appearing next to the direct wave Y0 ′ on the time axis of the test reception sound YY, and the sound having the sound level L1 or less. It is the time length of the 1st time slot | zone U1 which continues a level.
The sound level L1 is a level at which significant data can be demodulated from the test reception sound YY at the second point.
A specific value of the first signal length Ts1 is determined in consideration of an acoustic modulation / demodulation method. For example, when the modulation / demodulation method is the OFDM method, the first signal length Ts1 is an integral multiple of the time length Ts of the unit symbol of the modulation / demodulation method.
The ОFDM system is a system in which several hundreds of carriers arranged at fixed frequency intervals are digitally modulated and transmitted at fixed symbol periods. For modulation to an FDM signal, an inverse Fourier transform (IFFT) with a number of points Nu is usually used. One symbol of the transmission signal transmitted from the data transmission apparatus is composed of an effective symbol period signal (B + b) composed of an IFDM signal of Nu sample points modulated by IFFT and a signal b of the last fixed period of the effective symbol period. It consists of a guard interval period signal b 'copied before the period. The time length of the unit symbol is the sum of the time length of the effective symbol period and the time length of the guard interval period.
The first guard time Tn1 is obtained by superimposing the test reception sound YY while moving backward on the time axis by the first signal length Ts1 to obtain virtual reception sound, and the test transmission sound Y0 superimposed on the virtual reception sound. This is the length of time from the direct wave Y0 'until the acoustic level of the reverberant wave is attenuated to the acoustic level L1.
FIG. 8A shows the test transmission sound Y0.
FIG. 8B shows the test reception sound YY.
FIG. 8C shows the virtual reception sound YY ′.

The parameter transmission step S32 is a step of transmitting the estimated parameter from one of the first point or the second point to the other.
Below, the case where the 2nd data transmission apparatus 20 transmits a parameter to the 1st data transmission apparatus 10 is demonstrated to an example.
The second data transmission device 20 acoustically transmits a signal including parameters at the second point P2. As a modulation method at this time, a reliable method can be selected even when the transmission speed is low. For example, an MFSK modulation / demodulation method or a DPSK modulation / demodulation method can be used.
When the first data transmission apparatus 10 does not receive an acoustic signal including a parameter at a predetermined time, the first data transmission apparatus 10 returns to the start and performs the test transmission step S10 again.

The ACK signal transmission step S33 is a step of transmitting an ACK signal from the first point or the second point when the parameters can be received without error.
The first data transmission device 10 demodulates data including parameters from the acoustic signal received at the first point, performs error checking, and transmits an ACK signal when the error checking is passed. For example, the error check is a parity check, a checksum, or the like.
If the error check fails, the first data transmission device 10 returns to the start and performs the test transmission step S10 again.

The CONFIRM signal transmission step S34 is a step in which the side receiving the ACK signal at the first point P1 or the second point P2 transmits the CONFIRM signal.
When receiving the ACK signal, the second data transmission apparatus 20 transmits a CONFIRM signal.
When the first data transmission device 10 does not receive the CONFIRM signal for a predetermined time, the first data transmission device 10 returns to the start and performs the test transmission step S10 again.

  When the first data transmission apparatus 10 receives the CONFIRM signal, the parameter determination process is terminated, and the process proceeds to the actual transmission process S40 and the actual reception process S50.

The actual transmission step S40 is a step of transmitting the first transmission sound W0 obtained by modulating the data at the first point P1 and having the first signal length Ts1.
The first data transmission device 10 modulates data to be transmitted to obtain the first transmission sound W0, and transmits the first transmission sound W0.
When the first data transmission device 10 transmits the first transmission sound W0 and the first guard time Tn1 has elapsed, the first data transmission device 10 modulates the next data to be transmitted to obtain the next first transmission sound W0, The first transmission sound W0 is transmitted.
FIG. 8D shows the first transmission sound W0.

The actual reception step S50 receives the reception sound WW generated by the first transmission sound W0 propagating through the water at the second point P2, extracts the first transmission sound W0 from the reception sound WW, and demodulates the data. It is a process to obtain.
When the second data transmission apparatus 20 receives the underwater sound at the second point P2 and finds the first transmission sound W0 from the underwater sound, the second data transmission apparatus 20 cuts out the sound having the length of the first signal length Ts1 and demodulates it. And get the data.
The second data transmission device 20 tries to find the next first transmission sound W0 to be received after the first guard time Tn1 has elapsed after the first transmission sound W0 has been cut off.
FIG. 8E shows the reception acoustic WW.

  By continuing the above-described production transmission step S40 and production reception step S50, data can be transmitted from the first point P1 to the second point P2 using underwater sound.

The test transmission update step S60 is a step of updating the test reception sound YY with the new test reception sound YY by repeating the test transmission step S10 and the test reception step S20 again when a predetermined condition is satisfied.
The predetermined conditions are the following conditions.
(1) When the position of the first point or the position of the second point in water changes beyond a predetermined range. The above equation (2) is calculated, the usage time T1 ′ is updated timely, and the latest test transmission is performed. This is when the difference between the usage time T1 ′ when the sound is recorded and the current usage time T1 ′ exceeds a preset ΔT.
When the first time length T1 is increased, the transmission speed can be increased by increasing the first signal length Ts1 in accordance with the first time length T1.

(2) When the number of errors increases in data demodulation in the actual reception process The relationship between the first point and the second point changes, the sea level changes, and the first time length T1 is the first signal. When the length is shorter than the length Ts1, the reverberant wave overlaps the first transmission sound W0 in the reception sound WW, so that errors frequently occur in the error check when the first transmission sound W0 is demodulated.
When the first time length T1 is shortened, the transmission accuracy can be improved by shortening the first signal length Ts1 in accordance with the first time length T1.

(3) When a preset time elapses When a preset time elapses, it is estimated that the sea area conditions have changed, and the test reception sound YY is updated with the new test reception sound YY.

Next, an underwater acoustic transmission system according to the second embodiment of the present invention will be described.

FIG. 9 is an acoustic chart diagram 2 of the underwater acoustic transmission method according to the embodiment of the present invention.
The underwater acoustic transmission method is a method of transmitting data using underwater acoustic between a first point and a second point located in water, and includes a test transmission step S10, a test reception step S20, and a parameter determination step S30. It consists of a production transmission step S40, a production reception step S50, and a test transmission update step S60.
Since the configurations of the test transmission step S10, the test reception step S20, and the test transmission update step S60 are the same as those of the underwater acoustic transmission method according to the first embodiment, description thereof will be omitted.

The parameter determination step S30 includes a parameter estimation step S31, a parameter transmission step S32, an ACK signal transmission step S33, and a CONFIRM signal transmission step S34.
Since the configuration of the parameter transmission step S32, the ACK signal transmission step S33, and the CONFIRM signal transmission step S34 is the same as that of the underwater acoustic transmission method according to the first embodiment, description thereof is omitted.
Below, the case where the 2nd data transmission apparatus 20 estimates a parameter and sends a parameter to the 1st data transmission apparatus 10 is demonstrated to an example.

The parameter estimation step S31 is a step of analyzing the test reception sound YY and estimating parameters necessary for transmission.
The second data transmission device 20 estimates the first signal length Ts1, the first guard time Tn1, the second signal length Ts2, and the second guard time Tn2 from the test reception sound YY.
The first signal length Ts1 is shorter than the first time length T1.
The first time length T1 is located between the direct wave Y0 ′ of the test transmission sound Y0 and the reverberation wave Y1 appearing next to the direct wave Y0 ′ on the time axis of the test reception sound YY, and the sound having the sound level L1 or less. It is the time length of the 1st time slot | zone U1 which continues a level.
The second signal length Ts2 is shorter than the second time length T2.
The second time length T2 obtains the first virtual reception sound YY ′ obtained by superimposing the test reception sound YY while moving backward by the first signal length Ts1 on the time axis, and obtains the first virtual reception sound YY ′. Is the time length of the second time period U2 that is located after the first guard time Tn1 after the direct wave Y0 ′ of the test transmission sound Y0 superimposed on and maintains the sound level equal to or lower than the sound level L1.
In other words, the second time length T2 is obtained by superimposing the test reception sound YY while moving backward on the time axis by the first signal length Ts1 to obtain the first virtual reception sound YY ′. This is the time length of the second time period U2 that exists after the direct wave Y0 ′ of the test transmission sound Y0 superimposed on the sound YY ′ and maintains the sound level equal to or lower than the sound level L1. The first guard time Tn1 is the time from the direct wave Y0 ′ of the superimposed test transmission sound Y0 to the beginning of the second time zone U2.

The second guard time Tn2 is obtained by superimposing the test reception sound YY while moving backward on the time axis by the first signal length Ts1 to obtain the first virtual reception sound YY ′. The second virtual reception sound is obtained by superimposing while moving backward by the second signal length Ts2, and the second virtual reception sound is superimposed on the first virtual reception sound after being delayed by the first guard time Tn1. The sound YY ″ is obtained, and in the virtual reception sound YY ″, the sound level of the reverberant wave is attenuated to the sound level L1 after the direct wave Y0 ′ of the test transmission sound Y0 having the second signal length Ts2. It is the length of time until.
FIG. 9B shows the test reception sound YY.
FIG. 9C shows the first virtual reception sound YY ′.
FIG. 9D shows the virtual reception sound YY ″.

The actual transmission step S40 is obtained by modulating the data at the first point P1, and the first transmission sound W0 having the first signal length Ts1 and the first guard time Tn1 after transmitting the first transmission sound have elapsed. This is a step of transmitting a second transmission sound W01 having a second signal length Ts2 obtained by modulating data later.
The first data transmission device 10 modulates data to be transmitted to obtain the first transmission sound W0 and the second transmission sound W01, and transmits the first transmission sound W0 and the second transmission sound W01.
After transmitting the first transmission sound W0, the first data transmission device 10 transmits the second transmission sound W01 when the first guard time Tn1 has elapsed, and the next data to be transmitted when the second guard time Tn2 has elapsed. To obtain the next first transmission sound W0 and the second transmission sound W01 and transmit them.
FIG. 9E shows the first transmission sound W0 and the second transmission sound W01.

The actual reception step S50 receives the reception sound WW generated by the first transmission sound W0 and the second transmission sound W01 propagating in water at the second point P2, and the first transmission sound W0 from the reception sound WW. In this step, the second transmission sound W01 is extracted and demodulated to obtain data.
When the second data transmission apparatus 20 receives the underwater sound at the second point P2 and finds the first transmission sound W0 from the underwater sound, the second data transmission apparatus 20 cuts out the sound having the length of the first signal length Ts1 and demodulates it. And get the data.
When the second data transmission device 20 detects the next second transmission sound W01 to be received after the first guard time Tn1 has elapsed after cutting out the first transmission sound W0, the second data transmission device 20 has the length of the second signal length Ts2. Cut out the sound.
Thereafter, the second data transmission device 20 tries to find the next first transmission sound W0 after the second guard time Tn2 has elapsed.
FIG. 9F shows received sound.

Next, the modulation / demodulation method in the actual transmission step S40 and the actual reception step S50 will be described.
The number N of samples that can be transmitted between the frequency band W and the time width T is expressed by the following equation.
N = 2WT ------- Formula (3)
The amount of data carried by each sample is limited by the signal-to-noise ratio of that sample.
As a modulation method capable of transmitting the number of samples close to the upper limit of the expression (3), there are QAM (including QPSK), VSB (remaining sideband level), etc. for a single carrier (carrier wave). In the case of a plurality of carriers, there are orthogonal QAM (OFDM: Orthogonal Frequency Division Multiplex), orthogonal VSB, and the like.
If high-speed data transmission is to be realized in acoustic communication in shallow water, it is necessary to use a frequency band as wide as possible. Treating this frequency band as a single channel with uniform characteristics is not practical for the following reasons.
Reason 1: A normal transmitter is a resonance type and has a narrow frequency band.
Reason 2: Since the absorption loss of seawater increases with frequency, the propagation loss of high frequency increases as the propagation distance increases.
Therefore, a modulation method of a plurality of carriers (carrier waves) may be adopted, and the amount of data carried for each carrier may be adaptively changed according to the situation.

As the modulation schemes for multiple carriers, orthogonal QAM and orthogonal VSB are theoretically efficient frequency utilization schemes. In addition, an ordinary modulation method that is slightly less efficient but non-orthogonal may be used in a multi-channel manner with a frequency distribution in which the spectra do not overlap. For the purpose of high-speed transmission, it is appropriate to use orthogonal QAM and orthogonal VSB with high frequency utilization efficiency.
In orthogonal QAM, a plurality of carriers are arranged at a frequency interval equal to the sample rate fs, and two samples are orthogonally carried on each carrier. Two samples carried by one carrier can be separated because they are QAM modulated. It can be separated from samples carried by other carriers because the orthogonal condition is satisfied at the sample points.
The orthogonal VSB arranges a plurality of carriers at equal intervals with a frequency interval equal to one half of the sample rate fs, and carries one sample on each carrier. Samples carried on one carrier are VSB modulated. It can be separated from samples carried by other carriers because the orthogonal condition is satisfied at the sample points. The frequency band occupied by each sample is narrower than that of orthogonal QAM, but the frequency utilization efficiency is almost the same.

FIG. 10 shows transmission signal spectrums of orthogonal QAM and orthogonal VSB.
Here, when the carrier arrangement interval Fs is reduced and the number of channels is increased, the sample interval Tsample = 1 / fs is increased, and the time width required for transmitting one sample is increased. In an environment where data transmission is to be realized, assuming that the minimum value of the expected usage time T1 ′ is T1min, at least Tsample <T1min --------
Is necessary, and in practice, Tsample is required to be a fraction of T1min.
In the test transmission step S10 and the test reception step S20, a low-speed channel may be selected from the above multi-channel signals, and 1-2 samples of the channel may be used.

Also, when the OFDM system is selected as the modulation / demodulation system, at the actual transmission step, at least one of the plurality of carrier frequencies is set as a specific carrier, and the amplitude value of the specific carrier is fixed to a constant value and transmitted. The influence of the attenuation of the sound level may be removed from the amplitude of each of the plurality of carriers using the amplitude value of the specific carrier wave received by the second data transmission device as the reference amplitude value in the reception step. For example, the amplitude of each of the plurality of carrier waves is divided by the reference amplitude value.
Underwater acoustics are affected by the salinity of seawater and the state of waves on the sea surface, and the acoustic level is attenuated. In this way, errors in demodulating received acoustics and obtaining data are reduced.
In the actual transmission process, two specific carriers are selected from among a plurality of carriers, and the amplitude values of the two specific carriers are fixed to a constant value and transmitted. In the actual reception process, a reference amplitude value serving as a reference for each carrier wave is generated using the amplitude values of two specific carrier numbers, and the influence of sound level attenuation for each frequency from the amplitude of each carrier wave with each reference amplitude value. May be removed. For example, the amplitude of each of the plurality of carrier waves is divided by each reference amplitude value corresponding to the frequency.
Underwater acoustics are affected by the salinity of seawater and the state of ocean waves, and the degree of attenuation of the acoustic level differs from frequency to frequency. In this way, errors in demodulating received acoustics and obtaining data are reduced.

Below, the underwater acoustic transmission apparatus 1 which concerns on 2nd embodiment of this invention is demonstrated based on a figure.
FIG. 11 is a second configuration diagram of the data transmission apparatus according to the embodiment of the present invention.

The underwater sound transmission device is a device that transmits data using underwater sound between a first point and a second point located in water, and includes a first data transmission device 10 and a second data transmission device 20. Composed.
The first data transmission apparatus 10 has a plurality of transmitters that are located at the first point P1 and radiates sound in water, and each of the plurality of transmitters has a resonance frequency of each of a plurality of OFDM system carrier frequencies. Approximate to the frequency.
In general, the first data transmission device 10 and the second data transmission device 20 can transmit and receive bidirectionally, and thus have the same configuration. The configuration of the first data transmission device 10 and the second data transmission device 20 will be described with the configuration of the first data transmission device 10.
The first data transmission device 10 includes a communication controller 11, a modulator 12, a transmitter 13, a transmitter 14, a demodulator 15, a receiver 16 and a receiver 17.
Since the configuration of the communication controller 11, the demodulator 15, the receiver 16, and the receiver 17 is the same as that of the underwater acoustic transmission apparatus according to the first embodiment of the present invention, the description thereof is omitted.

The modulator 12 is a device that modulates data to be transmitted provided from the communication controller 11 into a signal waveform, and includes N modulators 12a,.
The transmitter 13 is a device that converts the output of the modulator 12 into an acoustic signal, is called a projector, and is composed of N transmitters 13a.
The transmitter 14 is an element that converts an acoustic signal and radiates acoustic energy into the water, and includes N transmitters 14a.
In general, the combination of the transmitter 13 and the transmitter 14 is called a projector and has a resonance frequency with high output efficiency.
When the modulation / demodulation method uses a plurality of carrier waves C1, C2, C3, C4, and C5 (FIG. 10), the resonance frequencies of the plurality of projectors substantially coincide with the carrier frequencies of the plurality of carrier waves. You may let them. For example, the resonance frequencies of the first to fifth transmitters 14a to 14e respectively match the carrier frequencies of the carrier waves C1 to C5.
In general, since a transmitter is manufactured by firing, it is difficult to perfectly match the resonance frequency with a desired frequency. The carrier frequency of each carrier is matched within a practical range.

If the underwater acoustic transmission method and the underwater acoustic transmission apparatus of the above-described embodiment are used, the following effects are exhibited.
Test transmission in the form of a pulse between two points located in the water in advance, detect the time length without the reverberation wave after the direct wave from the test reception sound, the time length in the actual transmission Because the data is transmitted on the transmission sound with a signal length that fits within the transmission sound, the transmission sound and the reverberation wave do not overlap in the received reception sound, and the transmission sound is easily extracted from the reception sound. It is possible to transmit sound between two points in the water without error.
In addition, the next time zone without reverberation is checked from the received sound, and the transmitted sound has a signal length that fits within the first time length and the signal length that fits within the next time length. Since data is transmitted on the next transmitted sound, the transmitted sound and the reverberant wave do not overlap in the received received sound, and the transmitted sound can be easily extracted from the received sound. It is possible to transmit sound without error.
In addition, since the OFDM modulation / demodulation method is used for actual underwater acoustic transmission, underwater acoustic transmission with high frequency utilization can be realized.
In addition, the UFDM modulation / demodulation method is used for actual underwater acoustic transmission, and a plurality of symbols are connected to create and transmit transmission sound that is shorter than the time length, so that reverberant waves do not overlap the symbols and transmit without errors. Efficient underwater acoustic transmission is possible. Here, the symbol is a group of data in the OFDM system.
In addition, when the predetermined conditions are satisfied, the test transmission process and the test reception process are repeated again to update the test reception sound with a new test reception sound. Underwater acoustic transmission with little transmission efficiency is possible.
In addition, as predetermined conditions, (1) when the position of the first point or the second point in water changes beyond a predetermined range, (2) an error occurs in data demodulation in the actual reception process. When increased, (3) When a certain amount of time has passed, by selecting etc., it is possible to transmit transmission sound that is more appropriately adapted to the conditions of the sea area, to transmit underwater acoustic transmission with less transmission error and good transmission efficiency Can do.
In addition, since a plurality of transmitters are provided in the data transmission device and the resonance frequencies of the plurality of transmitters are substantially matched to the carrier frequencies of the plurality of carriers, underwater acoustic transmission using a plurality of frequencies is performed. Wide frequency band can be used more efficiently.

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.
Although the example in which the first data transmission device transmits the test transmission sound and the second data transmission device receives the test reception sound has been described, the present invention is not limited to this. For example, the second data transmission device transmits the test transmission sound and transmits the first test transmission sound. The data transmission device may receive the test reception sound, or both may be repeated. The sound ray path representing the direction in which the sound travels is theoretically reversible, and even in this way, no particular problem occurs.
Although the example in which the second data transmission apparatus estimates the parameters has been described, the present invention is not limited to this. For example, the second data transmission apparatus may estimate the parameters, or both may estimate the parameters.
The test transmission sound transmitted in the test transmission step may also serve as a wake-up signal for the data transmission apparatus. The wake-up signal is a signal for starting up the data transmission apparatus in the sleep state in order to suppress power consumption of the data transmission apparatus.

It is a block diagram of the underwater acoustic transmission apparatus which concerns on embodiment of this invention. 1 is a first configuration diagram of a data transmission apparatus according to an embodiment of the present invention; FIG. It is an acoustic propagation figure of the underwater acoustic transmission method concerning the embodiment of the present invention. It is a reverberation pattern figure of the underwater acoustic transmission method which concerns on embodiment of this invention. It is explanatory drawing of the utilization time of the underwater acoustic transmission method which concerns on embodiment of this invention. It is a flowchart figure of the underwater acoustic transmission method which concerns on embodiment of this invention. It is a sequence diagram of the underwater acoustic transmission method which concerns on embodiment of this invention. It is the acoustic chart figure 1 of the underwater acoustic transmission method which concerns on embodiment of this invention. It is the acoustic chart figure 2 of the underwater acoustic transmission method which concerns on embodiment of this invention. It is a frequency band figure of the underwater acoustic transmission method which concerns on embodiment of this invention. It is the block diagram 2 of the data transmission apparatus which concerns on embodiment of this invention.

Explanation of symbols

S Sea surface B Sea floor P1 1st point P2 2nd point U1 1st time zone U2 2nd time zone Z0 Direct propagation path Z1 Sea floor / Sea surface reflection path Z2 Sea floor / Sea surface reflection path Y0 Test transmission sound Y0 'Test transmission sound direct wave Y1 reverberation wave Y2 reverberation wave YY test reception sound YY 'virtual reception sound YY''virtual reception sound W0 first transmission sound W01 second transmission sound WW reception sound W1 reverberation sound W2 reverberation sound C1 first carrier C2 second carrier C3 first Three carrier C4 Fourth carrier C5 Fifth carrier Ts1 First signal length Ts2 Second signal length Tn1 First guard time Tn2 Second guard time T0 Time length T1 ′ Usage time T1 First time length 10 First data Transmission device 11 Communication controller 12 Modulator 13 Transmitter 14 Transmitter 14a First transmitter 14b Second transmitter 14c Third transmitter 14d Fourth transmitter 1 4e Fifth transmitter 15 Demodulator 16 Receiver 17 Receiver 20 Second data transmission device 30 Information source 40 Information terminal S10 Test transmission step S20 Test reception step S30 Parameter determination step S31 Parameter estimation step S32 Parameter transmission step S33 ACK Signal transmission process S34 CONFIRM signal transmission process S40 Production transmission process S50 Production reception process S60 Test transmission update process

Claims (17)

An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. rather short than the first hour length T1,
The first transmission sound is transmitted after the first guard time Tn1 after the actual transmission step transmits the first transmission sound at the first point,
The first guard time Tn1 is obtained by superimposing the test reception sound while moving backward on the time axis by the first signal length Ts1 to obtain virtual reception sound, and directly applying the test transmission sound superimposed on the virtual reception sound. It is the length of time after the wave until the acoustic level of the residual wave attenuates to the acoustic level L1.
An underwater acoustic transmission method characterized by the above. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The second transmission sound having the second signal length Ts2 obtained by modulating the data after elapse of the first guard time Tn1 after the actual transmission step transmits the first transmission sound at the first point is transmitted. ,
The actual reception step is the second point, and the first transmission sound and the second transmission sound are received by receiving the reception sound generated by propagation of the first transmission sound and the second transmission sound in water. The sound is extracted and demodulated to obtain data,
The second signal length Ts2 is the direct wave of the test transmission sound superimposed on the virtual reception sound obtained by superimposing the test reception sound while moving the test reception sound backward by the first signal length Ts1 on the time axis. It is shorter than the second time length T2 that is the time length of the second time zone that is located after the elapse of the first guard time Tn1 and maintains the sound level equal to or lower than the sound level L1,
The sound level L1 is a level at which data can be demodulated from the received sound at a second point.
An underwater acoustic transmission method characterized by the above. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
Modulation / demodulation method is OFDM method,
The first time width Ts1 is an integral multiple of the unit symbol time length Ts.
An underwater acoustic transmission method characterized by the above. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
Modulation / demodulation method is OFDM method,
At least one of the plurality of carriers transmitted by the production transmission step is a specific carrier, and the amplitude value of the specific carrier is fixed to a constant value,
Using the amplitude value of the specific carrier wave received by the production reception step as a reference amplitude value to remove the influence of attenuation of the sound level from the amplitude of each of the plurality of carrier waves;
An underwater acoustic transmission method characterized by the above. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
When the position of the first point or the position of the second point in water changes beyond a predetermined range, the test transmission step and the test reception step are performed again to make the test reception sound a new one. The test transmission update process to update with received sound,
An underwater acoustic transmission method comprising: An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
Test transmission update for renewing the test reception sound with the new test reception sound by performing the test transmission step and the test reception step again when an error occurrence increases in the data demodulation in the actual reception step Process
An underwater acoustic transmission method comprising: An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. rather short than the first hour length T1,
One of the first data transmission device and the second data transmission device transmits the first transmission sound after the first guard time Tn1 after the first transmission sound is transmitted at the first point,
The first guard time Tn1 is obtained by superimposing the test reception sound while moving backward on the time axis by the first signal length Ts1 to obtain virtual reception sound, and directly applying the test transmission sound superimposed on the virtual reception sound. It is the length of time after the wave until the acoustic level of the residual wave attenuates to the acoustic level L1.
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
Transmitting a second transmission sound having a second signal length Ts2 obtained by modulating data after elapse of a first guard time Tn1 after the first data transmission device transmits the first transmission sound;
The second data transmission device receives reception sound generated by propagation of the first transmission sound and the second transmission sound in water, and the first transmission sound and the second transmission sound are received from the reception sound. Is extracted and demodulated to obtain data,
The second signal length Ts2 is the direct wave of the test transmission sound superimposed on the virtual reception sound obtained by superimposing the test reception sound while moving the test reception sound backward by the first signal length Ts1 on the time axis. It is shorter than the second time length T2 that is the time length of the second time zone that is located after the elapse of the first guard time Tn1 and maintains the sound level equal to or lower than the sound level L1,
The sound level L1 is a level at which data can be demodulated from the received sound at a second point.
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The modulation / demodulation method of the first data transmission device and the second data transmission device is the OFDM method,
The first time width Ts1 is an integral multiple of the unit symbol time length Ts.
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The modulation / demodulation method of the first data transmission device and the second data transmission device is the OFDM method,
The at least one of the plurality of carriers transmitted by the first data transmission device is a specific carrier, and the amplitude value of the specific carrier is fixed to a constant value,
Using the amplitude value of the specific carrier received by the second data transmission device as a reference amplitude value, the influence of attenuation of the sound level is removed from the amplitude of each of the plurality of carriers.
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
When the position of the first point or the second point in water changes beyond a predetermined range,
One of the first data transmission device and the second data transmission device transmits the pulsed test transmission sound again,
The other of the first data transmission device and the second data transmission device receives again the test reception sound generated when the test transmission sound propagates in water,
Updating the test reception sound with the new test reception sound;
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
When the occurrence of errors increases in data demodulation in the actual reception process,
One of the first data transmission device and the second data transmission device transmits the pulsed test transmission sound again,
The other of the first data transmission device and the second data transmission device receives again the test reception sound generated when the test transmission sound propagates in water,
Updating the test reception sound with the new test reception sound;
An underwater acoustic transmission device characterized by that. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The modulation / demodulation method of the first transmission device and the second transmission device is a method using a plurality of carrier waves,
The first data transmission device has a plurality of transmitters located at a first point and radiating sound in water,
The resonance frequency of each of the plurality of transmitters substantially matches the frequency of each of the plurality of carriers.
An underwater acoustic transmission device. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving a test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
In the actual transmission step, two specific carriers are specified from a plurality of carriers, and the amplitude width of the two specific carriers is fixed to a certain value and transmitted.
In the actual reception step, a reference amplitude width serving as a reference for each carrier wave is generated using the amplitude widths of the two specific carrier waves, and the sound level is attenuated for each frequency from the amplitude of each carrier wave with each of the reference amplitude values. To eliminate the effects of
An underwater acoustic transmission device. An underwater acoustic transmission method for transmitting data using underwater sound between a first point and a second point located in water,
A test transmission step of transmitting a pulsed test transmission sound at one of the first point and the second point;
A test reception step of receiving test reception sound generated by propagation of the test transmission sound in water at the other of the first point and the second point; and
A production transmission step of transmitting a first transmission sound obtained by modulating data at a first point and having a first signal length Ts1,
A second receiving step for receiving the reception sound generated by the first transmission sound propagating through the water, extracting the first transmission sound from the reception sound, and demodulating it to obtain data;
With
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The test transmission sound transmitted in the test transmission step also serves as a wake-up signal,
The wake-up signal is a signal for starting the data transmission device in a sleep state in order to suppress power consumption of the data transmission device that transmits data.
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
One of the first data transmission device and the second data transmission device specifies two specific carriers from a plurality of carriers, and transmits the fixed width of the two specific carriers to a fixed value,
The other of the first data transmission device and the second data transmission device generates a reference amplitude width that is a reference for each carrier using the amplitude widths of the two specific carriers, and each of the reference amplitude values is used for each of the reference amplitude values. Remove the effect of attenuation of sound level for each frequency from the amplitude of the carrier,
An underwater acoustic transmission device. An underwater acoustic transmission device that transmits data using underwater sound between a first point and a second point located in water,
A first data transmission device capable of transmitting and receiving underwater sound at a first point;
A second data transmission device capable of transmitting and receiving underwater sound at a second point;
With
One of the first data transmission device and the second data transmission device transmits a pulsed test transmission sound,
The other of the first data transmission device and the second data transmission device receives the test reception sound generated when the test transmission sound propagates in water,
The first data transmission device transmits a first transmission sound obtained by modulating data and having a first signal length Ts1,
The second data transmission device receives the reception sound generated by propagation of the first transmission sound in water, extracts the first transmission sound from the reception sound, demodulates to obtain data,
The first signal length Ts1 is a time length of a first time zone located between a direct wave of the test transmission sound and a reverberation wave that appears next to the direct wave on the time axis of the test reception sound. Shorter than the first time length T1,
The test transmission sound transmitted by one of the first data transmission device and the second data transmission device also serves as a wake-up signal,
The wake-up signal is a signal for starting the data transmission device in a sleep state in order to suppress power consumption of the data transmission device that transmits data.
An underwater acoustic transmission device.

Images