• 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.

• 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 the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.97-108
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• 2011

Systems for underwater environment monitoring and natural resources can be considered as a part of digital convergence where real-time data transmission is possible with the help of underwater wireless sensor network (UWSN). One of key technologies required for the deployment of the systems is underwater acoustic micro modem. In this work, we design and implement an acoustic modem equipped with a commercial omnidirectional transducer. We also make experiments at the northern Han river for the verification of the developed modem. According to the experiments, the modem supports the working distance of 250 m and the data rate of 200 bps with a negligible bit error rate. It is expected that the acoustic modem can be used for various applications based on UWSN in a near future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.258-261
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• 2010

The existing underwater acoustic communications modem is developing based on commercial products, so it is possible on functionality and performance of under water 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 thesis 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 chip.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.405-411
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• 2011

As the interest in ocean environment monitoring and ocean development has been increased, the need for researches on underwater wireless sensor network (UWSN) and low power consuming acoustic modem for UWSN has been arisen. In this paper, we design and implement a micro-modem equipped with a tiny and omnidirectional transducer for underwater acoustic communications. In addition, we make experiments in a water tank and a pond in order to verify the performance of the developed modem in terms of supply voltage and communication distance, and analyze the results. According to the outdoor experiments, the modem can send data wirelessly in underwater at a distance of 40 meter with a data rate of 200 bps and a bit error rate of $10^{-5}$ when the supply voltage is 12 V. Due to its small size, low power consumption and omnidirectional property, it is expected that the modem which is implemented in this paper could be utilized for various applications based on UWSN.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.144-149
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• 2016

In this paper, we analyze a QPSK MODEM over underwater acoustic channel model. Ambient noises and parameters of underwater environments debase the BER performance of an underwater modem. In the paper, the BER performance of uncoded QPSK and rate-2/3 convolutional coded QPSK is analyzed. And To improve BER Performance, we apply a channel equalization technique to the underwater modem.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.25-32
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• 2006

We propose a new M-ary state-transition FSK modulator technique for enhancing demodulator's symbol timing recovery which can be applied to acoustic MODEM. In the previous technique, the demodulator's symbol timing performance can degrade when the sequences of same symbols are transmitted. This proposed method, because the transmission symbol changes in every single symbol period, increases the synchronization performance dramatically and has a simple MODEM and frame structure. On the one hand, we improve modulation-derived synchronization(MDS) which is M-ary FSK's symbol timing recovery scheme, then analyze it. Finally the proposed method is analyzed from the viewpoint of frequency efficiency, which proves this method is appropriate for acoustic MODEM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.275-281
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• 2014

Recently, the need for various underwater application systems targeting efficient resource exploration and aquatic ecosystem monitoring is rapidly increasing in littoral sea and inland waters. In this paper, we focus on the research and development of digital module of acoustic micro modem which can be used for underwater mobile communication systems and underwater sensor network systems. Specifically, a digital module of acoustic modem embedding digital signal processor is designed and implemented. On top of the developed hardware platform, physical layer frame generation and recovery and channel coding algorithms are mounted and tested in a water tank and a pond to verify its functionality and performance. According to experimental results, less than 1 percent of total computational power is consumed in the processing of frame control and convolutional code with the data rate of 1 kbps. Thus, the performance of micro modem could be improved by loading efficient baseband algorithms into the processor while maintaining the implemented hardware.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.109-110
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• 2006

The performance of a digital baseband signal processing and data transmission rate depends on the modulation technique. In this paper, We implemented DSP communication system for Underwater acoustic communication using by adaptive BPSK modem technique. In order to implement adaptive modem, we suggested SNR detection block. SNR detection block has the reference SNR value that selects between window filter path and matched filter path. In this paper, suggested system is based on software interface and all Hardware(PLL, modem filter, equalizer etc) is implemented by software, exclusive of DSP, A/D, D/A converter, SDRAM and Flash memory.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.94.4-94
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• 2001

An acoustic ranging system was applied for reckoning the location of an agricultural vehicle in the field. The system has a number of fixed stations and a mobile station such as an agricultural vehicle. The mobile station comprises a radio frequency modulator-demodulator (RF MODEM), a buzzer, and a personal computer. The fixed station comprises an (RF MODEM), a microphone, an amplifier for the microphone, and a personal computer with a soundboard. The mobile station transmits a 7-bit ASCII code and, activates the buzzer simultaneously. The propagation delay time at the fixed station is caused by the difference ...