• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.9
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• pp.979-986
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• 2015

Security solutions using fiber-optic cable have not yet secured a solid technical stability, through which the Acoustic detection security system also did not have a complete defense techniques such as false alarm and detecting fail due to a number of variables. In this paper, we investigate 4 characteristics for the channel of underwater acoustic communication. We also construct detection system as a construction method for security system using optical cable through the analysis of acoustic signal in underwater. We perform analysis of signal characteristics and noise of underwater optical cable, and then we confirms the possibility of real application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1229-1236
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• 2016

In underwater acoustic multipath channel, a performance of underwater acoustic (UWA) communication systems is affected by dynamic variation of boundary and high temporal and spatial variability of the channel conditions. Time and spatial variations of UWA channel induce a carrier frequency offset (CFO) since a phase and a frequency of received signal mismatch with a transmitting signal. Therefore, a performance of a phase shift keying underwater acoustic communication system is degraded. In this study, we have analyzed a performance of CFO estimation and compensation using a phase code in time and spatial variation channel. A constant amplitude zero autocorrelation (CAZAC) signal is applied as a phase code signal and its performance is evaluated in water tank. The bit error rate of a quadrature phase shift keying (QPSK) system with a phase code is improved about 4 to 10 times better than that without a phase code.

• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.643-647
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• 2011

In this paper, we study the application of DSSS(Direct Sequence Spread Spectrum) in underwater acoustic communication for robust the ISI(Inter-Symbol Interference. We confirm the application of DSSS in underwater acoustic communication in underwater by the simulation with underwater channel impulse response and experiment. As a simulation result, the BER of QPSK technique is $1.14{\times}10^{-1}$ and the BER of DSSS technique is $6.73{\times}10^{-3}$. And we performed the experiment of DSSS technique in underwater. As a experiment result, the BER of QPSK technique is $3.19{\times}10^{-1}$ and the BER of DSSS technique is $5.17{\times}10^{-4}$.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.110-117
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• 2012

As the demand for underwater systems providing pollution monitoring, marine ecosystem observation, surveillance monitoring is increased, acoustic modem for short-range underwater communication is spotlighted as one of significant research topics. Typically, in shallow water, it is so hard to analyze acoustic wave which undergoes spreading, absorption, reflection and scattering through transmission that there are limited advanced results. Furthermore, in order for the modem to be loaded in a fixed node or a moving vehicle in shallow water, its size should be small enough. In this paper, we address underwater acoustic channel model and design and implement an efficient micro acoustic modem which is adequate for short-range underwater communication. The developed modem is verified in a lake by varying working range and data rate up to 500 meters and 2 kbps, respectively.

• The Journal of the Acoustical Society of Korea
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• v.27 no.3E
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• pp.104-111
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• 2008

Recently, a method for robust time reversal focusing has been introduced to extend the period of stable focusing in time-dependent ocean environments [S. Kim et al., J. Acoust. Soc. Am. 114, 145-157, (2003)]. In this study, concept of focal-size broadening based on waveguide invariant theory in an ocean time reversal acoustics is described. It is achieved by imposing the multiple location constraints. The signal vector used in multiple location constraints are found from the theory on waveguide invariant for frequency band corresponding the extended focal range. The broadening of foci in an ocean waveguide can play an important role in the application of time reversal processing, particularly to the underwater acoustic communication with moving vehicles. The proposed method is demonstrated in the context of the underwater acoustic communication from the transmit/receive array (TRA) to a slowly moving vehicle.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.421-422
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• 2007

In underwater, acoustic waves are used for telecommunication. The communication channels are very complicated, because of the distribution of temperature in depth, reflections from boundaries like as the surface of water and the bottom. We report the constitution of the underwater acoustic channel using the simulation of the Transmission Line Matrix Modeling and cross-correlations from the input and output signals.

• Journal of Ocean Engineering and Technology
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• v.22 no.2
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• pp.65-71
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• 2008

Recently, many researches in relation to data transmission with faster speed and greater volume, many researches have been carried out on sonar systems for underwater communication. According to these researches, an acoustic transducer for underwater communication requires wide bandwidth properties. In domestic researches for underwater communication sonar, an operating frequency in the range of $20{\sim}40\;kHz$ is used. In this paper, we propose anon-resonance type acoustic transducer for underwater communication. The TVR (transmitting voltage response) characteristics increased linearly as the frequency increased, and the RVS (receiving voltage sensitivity) characteristics were constant as the frequency increased. Traditional techniques for wide bandwidth transducershave a limit and a transmission loss difference at lower and higher frequency operating ranges. In this paper, the new transducer proposed decreased the transmission loss under some conditions. It was optimized with the FE analysis tool (ATILA) and evaluated using the TVR and the RVS characteristics in the range of $10{\sim}90\;kHz$. The value of TVR was 138 dB at 20 kHz and 148 dB at 40 kHz, and the differences was 12 dB. The value of RVS was $195{\pm}2\;dB$ and nearly constant. From theseresults, it is certain that the developed transducers can be used for an underwater communication network in the 1.3 km range with both a 20 kHz bandwidth and 30 kHz center frequency.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.239-245
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• 2006

Time-reversal processing (TRP) has been shown as an effective way to focus in both time and space. The temporal focusing properties have been used extensively in underwater acoustics communications. Recently. adaptive time-reversal processing (ATRP) was applied to the simultaneous multiple focusing in an ocean waveguide. In this study. multiple focusing with ATRP is extended to the underwater acoustic communication algorithm for multiple receiving locations. The developed algorithm is applied to the underwater acoustic communication to show, via simulation and real data, that the simultaneous self-equalization at multiple receiving locations is achieved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.212-221
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• 2001

This paper deals with the design techniques for underwater acoustic basin. An underwater acoustic basin is needed for test and calibration of acoustic sensors, acoustic digital communication system, acoustic measurement system, and underwater image data telemetry system. KRISO(Korea Research Institute of Ships and Ocean Engineering) have planned the construction of an underwater acoustic tank from 1999 to 2001 through internal project. We studied about absorbtion characteristics of a porous re-cycled rubber which is selected as a absorption materials and designed absorption plate with wedge shape. The simulation of reflection analysis along the wedge angle for wedged type plate was presented.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.6
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• pp.831-836
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• 2010

In real system application, the path planning and following system for the coordinated control of heterogeneous marine robots based on the underwater acoustic communication has the following problems: surface and underwater robots have different maneuvering properties, an underwater robot requires more effective operating, it has a limited communication range because of the transmission loss (TL) of acoustic wave, it has a communication error because of the Doppler distortion of acoustic wave, and further, it requires an easy design procedure in terms of its structures and parameters. To solve these problems, an intelligent path planning algorithm using the evolution strategy (ES) and the fuzzy logic controller (FLC) based on system modeling, is proposed. To verify the performance of the proposed algorithm, the path planning and following of an underwater robot is performed according to the maneuvering of a surface robot. Simulation results show that the proposed algorithm effectively solves the problems.