• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.105-111
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• 1997

This Paper Proposes a new efficient system design strategies for the acoustic-based underwater multiple modem and media access control protocol. The system aims to establish the acoustic-based communication network of an underwater vehicles for deep sea mining, which ensures a certain level of maximum throughput regardless of the propagation delay of acoustic and allows fast data transmission through the acoustic-based multiple channel. A media access control protocol for integrated communication network and it's acoustic-based communication modems that allows 'peer-to-peer' communication between a surface mining plant multiple underwater system is designed, and the proposed media access control protocol is implemented for its verification. Furthermore, a proposed design strategies which make it possible to control the multiple vehicle for an underwater mining is presented in this paper.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.1
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• pp.239-260
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• 2023

The underwater acoustic wireless communication networks are generally formed by the different autonomous underwater acoustic vehicles, and transceivers interconnected to the bottom of the ocean with battery deployed modems. Orthogonal frequency division multiplexing (OFDM) has become the most popular modulation technique in underwater acoustic communication due to its high data transmission and robustness over other symmetrical modulation techniques. To maintain the operability of underwater acoustic communication networks, the power consumption of battery-operated transceivers becomes a vital necessity to be minimized. The OFDM technology has a major lack of peak to average power ratio (PAPR) which results in the consumption of more power, creating non-linear distortion and increasing the bit error rate (BER). To overcome this situation, we have contributed our symmetry research into three dimensions. Firstly, we propose a machine learning-based underwater acoustic communication system through long short-term memory neural network (LSTM-NN). Secondly, the proposed LSTM-NN reduces the PAPR and makes the system reliable and efficient, which turns into a better performance of BER. Finally, the simulation and water tank experimental data results are executed which proves that the LSTM-NN is the best solution for mitigating the PAPR with non-linear distortion and complexity in the overall communication system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.256-265
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• 2017

In this paper, an ascheme is proposed for multiuser underwater acoustic communication by using the multi-chirp rate signals. It differs from the well known TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access) or CDMA (Code Division Multiple Access), by assigning each users with different chirp-rate carriers instead of the time, frequency or PN code. Multi-chirp rate signals can be separated from each other by FrFT (Fractional Fourier Transform), which can be regarded as the chirp-based decomposing, and superior to the match filter in the underwater acoustic channel. VTRM (Virtual Time Reverse Mirror) is applied into the system to alleviate the ISI caused by the multipatch and make the equalization more simple. Results of computer simulations and pool experiments prove that the proposed multiuser underwater acoustic communication based on the multi-chirp rate exhibit well performance. Outfield experments carrie out in Xiamen Port show that using about 10 kHz bandwidth, four users could communicate at the same time with 425 bps with low BER and can match the UAC application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.810-816
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• 2011

The existing underwater acoustic communications modem is developing based on commercial products, so it is possible on functionality and performance of underwater acoustic communications modem implementation. But the production of development system is required to single platform system implementation at the system's size and cost. So this paper designs and implements the signal processing module as an important role to single hardware platform production of underwater acoustic communication modem by using TigerSHARC DSP processor.

• Journal of Korea Multimedia Society
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• v.17 no.5
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• pp.631-639
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• 2014

Recently, research on Media Access Control (MAC) techniques for underwater acoustic communication has been conducted actively. For successful acoustic communication in underwater conditions, development of environmentally adaptive MAC techniques, which is taking narrow bandwidth, distance, depth, noise level, salinity, multipath and etc into account, is an especially important work. In this paper, knowledge based system is introduced not only to obtain adaptive and optimal communication parameters but also increase network efficiency and availability by requesting change of MAC techniques based on decisions from knowledge-based system Smart Decision Block (SDB). Computer simulations were also conducted to verify the performance of the proposed system in underwater conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.231-234
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• 2008

The paper proposed the new underwater wireless communication system fitted to non-linear acoustic channel. Generally, in non-linear acoustic channel, one used to do acoustic communication using parametric effect that is some effect caused from acoustic wave having frequency different of two primary acoustic wave frequency. In the paper, Offset PSK communication method fitted to non-linear acoustic channel was proposed, and it was demonstrated through simulations.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.509-515
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• 2010

Such as disaster rescue in deep water, undersea exploration and monitering for environmental pollution, many applications require the acoustic communication for high data rate over underwater acoustic channel. As underwater channel is very complex and is time-varying, conventional single carrier communication has good performance. In this paper, An adaptive OFDM system is analyzed for high data rate and reliability and rubust service over UWA channels. Through the adaptive system, we show threshold switching for an adaptive algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.235-242
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• 2006

This paper proposes the new efficient system design strategies for the acoustic-based underwater communication system and it's media access protocol, which make it possible to control the multiple vehicles for underwater duty working by the surface plant. For an approach to implementation of the system, it is inevitable to establish acoustic-based underwater digital communication network to exchange the information between a surface plant and multiple vehicles in underwater.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.336-342
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• 2017

Recently, there has been an increasing need for underwater communication systems to monitor ocean environments and prevent marine disasters, as well as to secure ocean resources. Most underwater communication systems adopted acoustic communication with a consideration of attenuation, absorption, and scattering in conductive sea water, and developed fully digital modems based on processors. In this study, a digital up converter (DUC) and a digital down converter (DDC) was developed for an underwater basestation based on underwater acoustic communication systems. Because one of the most important issues in underwater acoustic communication systems is low power consumption due to environmental problems, this study developed a specific hardware module for DUC and DDC. It supported four links of underwater acoustic communication systems and converted the sampling rate and frequency. The systemwas designed and verified using Verilog-HDL in ModelSim environment with the test data generated from baseband layer parts for an underwater base station.

• The Journal of the Acoustical Society of Korea
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• v.24 no.3E
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• pp.109-114
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• 2005

In this paper, we present a phase coherent all-digital transceiver for underwater acoustic communication, which allows the system to reduce complexity and increase robustness in time variant underwater environments. It is designed in the digital domain except for transducers and amplifiers and implemented by using a multiple digital signal processors (DSPs) system. For phase coherent reception, conventional systems employed phase-locked loop (PLL) and delay-locked loop (DLL) for synchronization, but this paper suggests a frame synchronization scheme based on the quadrature receiver structure without using phase information. We show experimental results in the underwater anechoic basin at MOERI. The results show that the adaptive equalizer compensates frame synchronization error and the correction capability is dependent on the length of equalizer.