• Title/Summary/Keyword: Underwater acoustic channel

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Bit Error Parameters on Passive Phase Conjugation Underwater Acoustic Communication (수동 페이저 컨쥬게이션 수중음향통신 기법의 비트오류 영향 인자)

  • Yoon, Jong-Rak;Park, Moon-Kab;Ro, Yong-Ju
    • The Journal of the Acoustical Society of Korea
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    • v.24 no.8
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    • pp.454-461
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    • 2005
  • Time spread due to the multipath in underwater acoustic channel, induces ISI (Inter-Symbol Interference) which degrades the performance of the underwater acoustic communication system. The passive phase conjugation (PPC) which improves the signal to multipath interference ratio (SMR) and therefore reduces the frequency selectivity. is a diversity communication technique giving a less ISI under multipath fading channel. Its frequency selectivity depends on the number of receiver array sensors and time varying source to receiver range. In this study, frequency selectivity of the PPC and its effects on bit error of underwater acoustic communication is analyzed by numerical simulation.

Performance Analysis of an OFDM System over an underwater acoustic channel (수중 음향 채널에서 OFDM 시스템의 성능 분석)

  • Kang, Heehoon;Lee, Youngjong;Han, Wanok
    • Journal of the Institute of Electronics and Information Engineers
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    • v.49 no.11
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    • pp.211-216
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    • 2012
  • 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, In this paper, The proposed OFDM system with synchronization errors and multipath delay spread is analyzed for high data rate and reliability and rubust service over UWA channels.

Analysis of Optimum Iterative Codes for Underwater Acoustic Communication based on Turbo Equalizer (수중 음향통신에 적합한 터보 등화기 기반의 최적의 반복 부호 기법 연구)

  • Park, Tae-Doo;Jung, Ji-Won
    • Journal of Navigation and Port Research
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    • v.37 no.5
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    • pp.487-492
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    • 2013
  • Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In order to improve the performance, it is necessary to employ an iterative coding scheme. Among the iterative coding scheme, turbo codes, LDPC codes and convolutional code based on BCJR algorithm are dominant channel coding schemes in recent. Therefore this paper analyzed the performance of iterative codes based on turbo equalizer with the same coding rate and similar codeword length. The performances of three kinds of iterative codes were evaluated in the environment of underwater acoustic communication channel that are real data collected in Korean east sea. The distance of transmitter and receiver was 5Km and data rate was 1Kbps. As a result, convolutional code based on BCJR algorithm has better performance in underwater channel than turbo codes and LDPC codes.

DSSS-Based Channel Access Technique DS-CDMA for Underwater Acoustic Transmission

  • Lee, Young-Pil;Moon, Yong Seon;Ko, Nak Yong;Choi, Hyun-Taek;Huang, Linyun;Bae, Youngchul
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.15 no.1
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    • pp.53-59
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    • 2015
  • This paper proposes a novel method for acoustically and wirelessly transmitting data underwater with a high transmission rate. The method uses the most promising physical layer and multiple access technique (i.e., the code division multiple channel access technique) to divide the channel into subchannels. Data is transmitted through these subchannels. The codes are pseudo-random noise (PN) sequences. In the spread-spectrum technique, a signal such as electrical, electromagnetic, acoustic signal generated in a particular bandwidth is deliberately spread in the frequency domain, which results in a signal with a wider bandwidth. This paper reviews the possibility of application of the direct-sequence code division multiple access (DS-CDMA) technique in an underwater system using MATLAB. As the result of our review, we recognize that the DS-CDMA technique can be applied to underwater environments.

An Efficient ARQ for Multi-Hop Underwater Acoustic Channel with Long Propagation Delay and High Bit-Error Rate

  • Lee, Jae-Won;Jang, Youn-Seon;Cho, Ho-Shin
    • The Journal of the Acoustical Society of Korea
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    • v.30 no.2
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    • pp.86-91
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    • 2011
  • In the underwater communications, the acoustic channel is in poor communication conditions, such as long propagation delay, narrow bandwidth, and high bit-error rate. For these bad acoustic channels, we propose an efficient automatic repeat request (ARQ) for multi-hop underwater network by using the concepts of concurrent bi-directional transmission, multiple sub-packets, and overhearing data packet instead of the acknowledgement signal. Our results show that the proposed ARQ significantly reduces the transmission latency especially in high BER compared with the existing Stop and Wait ARQ.

Doppler Frequency Estimation for Time-Varying Underwater Acoustic Communication Channel (시변 수중음향통신 채널을 위한 도플러 주파수 추정)

  • Hwang, Chan-Ho;Kim, Ki-Man
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.1
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    • pp.187-192
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    • 2015
  • Underwater acoustic communication channels have very complex channel characteristics caused by time-varying sea surface, submarine topography, sound speed, and geometry between transmitter and receiver. Especially, the channel has time-variance and doppler effect due to wind and sea current. We have to recognize the channel state and apply it to communication technique for increasing transmission efficiency in the underwater acoustic channel. In this paper, we present the frame recursive modulation and demodulation method using ambiguity function and autocorrelation function to estimate the doppler frequency. Furthermore, we conducted the simulation and sea experiment to evaluate the performance of the proposed method. When the channel coding technique was not used, the bit error rate performance of the proposed method was improved about 32 % compared with conventional method.

Performance Comparison of Space Time block coded Frequency Domain Equalization transmission Scheme in Underwater Acoustic Communication Channel (수중음향 통신채널 환경에서 시공간 블록부호를 적용한 주파수영역 등화기법의 성능평가)

  • Hwang, Hoseon;Lee, Seokwoo;Kang, Yeongsik;Choi, Jaehoon
    • Journal of the Institute of Convergence Signal Processing
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    • v.20 no.4
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    • pp.177-185
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    • 2019
  • In this paper, we propose and evaluate a FDE combined with STBC transmission structure to cancellation of ISI in underwater acoustic communication. To achieve this purpose, underwater acoustic channels are modeled and the simulation results are presented. In case of STBC-FDE, the transmission rate is less about 4% than STBC-OFDM, but the SER performance is better than STBC-OFDM that is larger from 4.4% to 16.8% at the SNR of 15dB than STBC-OFDM.

Channel Transfer Function Estimation based on Delay and Doppler Profile for Underwater Acoustic OFDM Communication System

  • Shiho, Oshiro;Tomohisa, Wada
    • International Journal of Computer Science & Network Security
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    • v.23 no.1
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    • pp.96-102
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    • 2023
  • In this paper, we proposed Channel Transfer Function estimation based on Delay and Doppler Profile for underwater acoustic OFDM communication system. It improved the estimation accuracy of the channel transfer function by linear time interpolation the change of Scattered Pilot (SP) insertion frequency in the time direction and the time by Delay and Doppler profile that analyzes the multipath situation of the channel investigated the performance of interpolation by simulation and report it. Previous works is inserted SP every 4 OFDM. It was effective under the environment without multipath, but it has observed that the effect of CTF compensation has been lowered in multipath channel condition. In addition to be better when inserted SP every 2 OFDM. But the amount of sending data will be decrease. Therefore, we conducted research to improve 4 OFDM with new interpolator. A computer simulation was performed as a comparison of SP inserted every 4 OFDM, SP inserted every 2 OFDM, and 4 OFDM with new interpolator. the performance of the proposed system is overwhelmingly improved, and the performance is slightly improved even 64 QAM.

Study on Cooperative Communication for Underwater Acoustic Channels (수중음향 채널에서의 협력통신에 대한 연구)

  • Kang, Heehoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.10
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    • pp.168-174
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    • 2015
  • In this paper, we analyze the performance of cooperative communication techniques on an underwater channel. By analyzing the BER performance of cooperative transmission protocol and combining types ERC, FRC, SNRC and ESNRC on underwater channel, through the result, we can choose an a proper cooperative technique for an underwater channel. The analysis of BER performance is achieved by a computer simulation.

MIMO Vector Channel Modeling and Performance Analysis in Underwater Channel Environments (수중 MIMO 벡터 채널 모델링 및 성능 분석)

  • Lee, Deok-Hwan;Ko, Hak-Lim;Lim, Yong-Kon
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.8
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    • pp.426-431
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    • 2007
  • In this paper we have studied the underwater vector channel modeling for MIMO(Multiple Input Multiple Output) to increase the performance and efficiency for ultrasound communication in underwater channel environments. Also we have analyzed the MIMO techniques using the proposed channel modeling. For underwater MIMO channel modeling. experiments were done in real channel environments and the data were analyzed to estimate parameters such as fading, Doppler, time delay, angle of arrival, and receiving power. These were used for modeling of underwater vector channel modeling for MIMO. Additionally, we have analyzed the performance of MIMO systems using our proposed channel models. As a result we could see that the BER has decreased severely with the same SNR when using the MIMO system.