Hydroacoustic communication system and receiving apparatus

1. An underwater acoustic communication system, comprising:

a transmission device including N (N is an integer of two or more) transmitters; and

a reception device, wherein

the reception device comprises:

M (M is an integer of two or more) receivers configured to receive M reception signal sequences corresponding to N transmission signal sequences transmitted from the N transmitters through sound waves;

a beam former configured to suppress multipath waves other than direct waves of the M received reception signal sequences and to generate L (L is an integer of two or more) signal sequences from the M reception signal sequences; and

a signal estimator configured to estimate the N transmission signal sequences based on the L generated signal sequences,

wherein each of the N transmitters, the M receivers, the beam former and the signal estimator is implemented by:

i) computer executable instructions executed by at least one processor,

ii) at least one circuitry or

iii) a combination of computer executable instructions executed by at least one processor and at least one circuity,

wherein a result value obtained by multiplying an interval of the transmitters and an interval of the receivers is an integer multiple of a result value obtained by dividing a result value obtained by multiplying a wavelength of the sound waves and a distance between the transmitters and the receivers, by a number of the receivers.

2. The underwater acoustic communication system according to claim 1 , wherein:

in a case where the transmission device is installed near a bottom of water, the N transmitters each have directivity of a sound wave directed toward a water surface; and

in a case where the reception device is installed near the water surface, the M receivers each have directivity of a sound wave arriving from the bottom of water.

3. The underwater acoustic communication system according to claim 1 , wherein:

in a case where the transmission device is installed near a water surface, the N transmitters each have directivity of a sound wave directed toward a bottom of water; and

in a case where the reception device is installed near the bottom of water, the M receivers each have directivity of a sound wave arriving from the water surface.

4. The underwater acoustic communication system according to claim 1 , wherein:

the beam former suppresses reception power of the multipath waves.

5. The underwater acoustic communication system according to claim 1 , wherein:

the beam former increases a Signal-to-Interference plus Noise power Ratio of the direct waves.

6. A reception device, comprising:

M (M is an integer of two or more) receivers configured to receive M reception signal sequences corresponding to N (N is an integer of two or more) transmission signal sequences transmitted from N transmitters through sound waves;

a beam former configured to suppress multipath waves other than direct waves of the M received reception signal sequences and to generate L (L is an integer of two or more) signal sequences from the M reception signal sequences; and

a signal estimator configured to estimate the N transmission signal sequences based on the L generated signal sequences,

wherein each of the N transmitters, the M receivers, the beam former and the signal estimator is implemented by:

i) computer executable instructions executed by at least one processor,

ii) at least one circuitry or

iii) a combination of computer executable instructions executed by at least one processor and at least one circuity,

wherein a result value obtained by multiplying an interval of the transmitters and an interval of the receivers is an integer multiple of a result value obtained by dividing a result value obtained by multiplying a wavelength of the sound waves and a distance between the transmitters and the receivers, by a number of the receivers.

7. The reception device according to claim 6 , wherein:

in a case where a transmission device including the N transmitters is installed near a bottom of water, the N transmitters each have directivity of a sound wave directed toward a water surface; and

in a case where the reception device is installed near the water surface, the M receivers each have directivity of a sound wave arriving from the bottom of water.

8. The reception device according to claim 6 , wherein:

in a case where a transmission device including the N transmitters is installed near a water surface, the N transmitters each have directivity of a sound wave directed toward a bottom of water; and

in a case where the reception device is installed near the bottom of water, the M receivers each have directivity of a sound wave arriving from the water surface.

9. The reception device according to claim 6 , wherein:

the beam former suppresses reception power of the multipath waves.

10. The reception device according to claim 6 , wherein:

the beam former increases a Signal-to-Interference plus Noise power Ratio of the direct waves.