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Research and development on underwater acoustic communications are in progress in our group. In January, 2010, we carried out the sea area experiment at near bottom in about 1,600m depth area using quadrature phase shift keying (QPSK) and 8-phase shift keying (8PSK) modulation method. A wideband tilted toroidal beam transducer and a multi-channel combined decision feedback equalizer with 4-hydrophone...
An autonomous underwater vehicle (AUV) can achieve precise observation in the sea. Also in Japan agency for Marine-earth Science and Technology (JAMSTEC) some observations with AUV ldquoURASHIMArdquo have been implemented mainly in deep ocean. Tracking or navigation of the AUV is significant to make the observations more valuable. Almost AUV equips an inertial navigation system (INS) to navigate own...
To achieve high-speed acoustic data transmission, the use of a frequency band of 80 plusmn 20 kHz is being considered. However, the absorption attenuation coefficient in these frequencies only has empirical formula. Therefore, the absorption attenuation was measured using the frequency of 60 to 100 kHz within the propagation distance of 530 to 700 m at approximately 1,000 m depth. The transmission...
In JAMSTEC, the acoustic communication is investigated, especially in deep water environment. Then, short-range (up to 500 m) high speed (around 64 kbps) acoustic communication system for deep sea environment is investigated in our group. To obtaining an real sea data of acoustic transmission, an experiment was carried out at the depth of 1,000 m in February 2007. A transmitter was moored at near...
In out research program, research and development on a long cruising autonomous underwater vehicle (AUV) are promoted. In such AUV operation, it is very significant to establish acoustic communication even at low data-transmission rate. Time-reversal techniques have a possibility to realize such long horizontal communication, which converge multipath signals to the focus, decrease intersymbol interference...
The super short base line (SSBL) method of the acoustic underwater positioning is commonly used due to the simplicity to operation. Though the accuracy of each single shot positioning is not so high. The SSBL for the autonomous underwater vehicle (AUV) becomes more accurate and helpful to navigate the AUV by transmitting the data obtained in each side of seabed and surface such as Global Positioning...
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