High-Speed Acoustic Data Link Transmitting Moving Pictures for
Autonomous Underwater Vehicles
A0153Junichi Kojima KDDI R&D Laboratories
A0148Tamaki Ura Underwater Technology Research Center, Institute of Industrial Science, University of Tokyo
A0154Hiromoto Ando National Maritime Research Institute
A0130Kenichi Asakawa Deep Sea Research Department, Japan Marine Science and Technology Center
This paper will describe a new high-speed acoustic data link for an
Autonomous Underwater Vehicle that can inspect underwater structures
at the depth of up to 3000 metes. The acoustic transmission will be
performed between the AUV and a repeater that will be suspended from a
mother ship using an optical fiber cable at distance of 500 meters
from the seabed. This configuration reduces the transmission distance
and enables high-speed transmission of compressed moving video signal.
KDD R&D laboratories have already developed acoustic data transmission
system of 32 kbits/s transmitting compressed still pictures. The
maximum transmission speed for the new link was increased to 128
kbits/s that was enough for transmitting moving video signal.
A wideband transducer is a key device to realize the high-speed
transmission. A new transducer was developed using a composite
oscillator that consists of a number of separated thin cylindrical
piezoelectric ceramic. With this configuration, wide frequency
bandwidth and wide directivity could be realized at the same time.
The frequency band and the directivity of the fabricated transducer is
80kHz to 120 kHz and 30 degrees respectively, that is enough for
transmitting 128 kbits/s signal. The size of the transducer is 60 mm
in diameter and 80 mm in length, that is small enough for being
mounted on a small-sized AUV.
The electronics of the underwater system consists of a DSP board for
the modulation and a power amplifier. The size and weight of the
electronics are very small (160mm (L), 90mm (W), 60mm (D) ) and light
enough to be put on a small AUV.
Tank tests were performed in order to optimize the parameters of the
adaptive equalizer, the carrier recovery circuit and the timing
recovery circuit. As a result, it was confirmed that this acoustic
data link could transmit 128kbits/s signals.