• Title/Summary/Keyword: Underwater Communications

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Performance Evaluation of Underwater Optical Wireless Communication Depending on the Modulation Scheme

  • Jeong, Gabin;Kim, Sung-Man
    • Current Optics and Photonics
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    • v.6 no.1
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    • pp.39-43
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    • 2022
  • Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

Q-NAV: NAV Setting Method based on Reinforcement Learning in Underwater Wireless Networks (Q-NAV: 수중 무선 네트워크에서 강화학습 기반의 NAV 설정 방법)

  • Park, Seok-Hyeon;Jo, Ohyun
    • Journal of Convergence for Information Technology
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    • v.10 no.6
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    • pp.1-7
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    • 2020
  • The demand on the underwater communications is extremely increasing in searching for underwater resources, marine expedition, or environmental researches, yet there are many problems with the wireless communications because of the characteristics of the underwater environments. Especially, with the underwater wireless networks, there happen inevitable delay time and spacial inequality due to the distances between the nodes. To solve these problems, this paper suggests a new solution based on ALOHA-Q. The suggested method use random NAV value. and Environments take reward through communications success or fail. After then, The environments setting NAV value from reward. This model minimizes usage of energy and computing resources under the underwater wireless networks, and learns and setting NAV values through intense learning. The results of the simulations show that NAV values can be environmentally adopted and select best value to the circumstances, so the problems which are unnecessary delay times and spacial inequality can be solved. Result of simulations, NAV time decreasing 17.5% compared with original NAV.

Overview of anthropogenic underwater sound effects and sound exposure criteria on fishes (어류에 미치는 인위적인 수중소음 영향과 피해기준에 대한 고찰)

  • PARK, Jihyun;YOON, Jong-Rak
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.53 no.1
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    • pp.19-40
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    • 2017
  • A scientific and objective sound exposure criterion for underwater sound damage on fish has been required since there has been many disputes between an underwater sound maker and a fish damage receiver. The existing criteria are still incomplete scientifically owing to a degree of variability of underwater sounds, diversity of fish hearing sensitivity and damage types, etc. This study reviews existing studies on a hearing mechanism of fish species, manmade underwater sound characteristics and sound exposure assessment parameters, and recent sound exposure criteria. A governing equation for damage coverage estimation and damage coverage dependency on sound source level, ambient noise and transmission loss are also reviewed and interpreted based on sound exposure environments. The foreign and Korean (National Environmental Dispute Medication Commission) criteria are reviewed and compared based on scientific aspects. In addition, the deficit and limit of Korean criteria are presented. The objective of this study is to give a direction for related researches and legislation of sound exposure criteria on fish.

Approaches to the Design and Modularization for Implementing Multimedia-based Underwater Communication to Use Integrated MAC (통합 MAC을 이용하는 다중 매체 기반 수중 통신 구현을 위한 설계 및 모듈화 접근방법)

  • You, Dongsun;Kim, Changhwa
    • Journal of Korea Multimedia Society
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    • v.22 no.11
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    • pp.1259-1268
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    • 2019
  • Recently, Communication media have been developed for the underwater communication in underwater environments where the underwater communication failures occur frequently. Although the underwater communication by one medium is not stable due to the influence of the underwater environment, the use of various communication media can complement each other and so this makes the underwater communication more stable. For this reason, this paper proposes approaches to the design and implementation of integrated MAC for complementing individual unstable underwater communications. In addition this paper presents the comparison and analysis on each of the proposed approaches so to be able to provide guidelines to designers and implementers of integrated MAC.

Transmission Performance of Application Traffic on Underwater MANETs (수중 MANET에서 응용 트래픽의 전송 성능)

  • Kim, Young-Dong
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2013.05a
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    • pp.557-560
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    • 2013
  • MANTET(Mobile Ad-Hoc Networks), which is configured and operated by each terminals with no support of communication infra-structures, is recently expanded its application fields from terrestrial communications to underwater environments with technical advances of Wi/Fi and minimized portable terminals. Underwater sensor network, undersea environment explorations and probes, information transmission for underwater area, etc., is typical application fields of underwater MANET. Especially, Performance measurement and analysis on this application fields is one of important research area and base of design, implementation and operation for underwater MANET. However, the research results are focued on various transmission parameters on network level, and its objects of analysis are also performance of network level. In this paper, transmission performances for application levels are measured and analyzed for user levels on underwater MANET. In this study, voice traffic is assumed as object application traffic, computer simulation which is based on NS-2 having additional implemented functions for underwater communications is used. on some defined scale of MANET, transmission performances according to varying traffic environments are measured and analyzed, operation conditions on underwater MANET is suggested with the analysis.

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A study on the Frequency Modulation-based Audio Transmission System for Short-range Underwater Optical Wireless Communications (근거리 수중 광무선 통신을 위한 주파수 변조 기반 오디오 전송 시스템 연구)

  • Kim, Yeon-Joo;Sohn, Kyung-Rak
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.1
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    • pp.166-171
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    • 2012
  • In this paper, short-range underwater wireless communication technique using visible LEDs is proposed. As an alternative to conventional acoustic system, visible LED communications show high quality and high speed data transmission characteristics. We design a frequency modulation-based optical wireless audio transmission system. The CD4046B phase-locked loop device is applied to implement the frequency modulation and demodulation. With a transmission modulation of 100 kHz, audio signal has successfully received at a transmission distance of 30 cm.

Analysis of an Optimal Iterative Turbo Equalizer for Underwater Acoustic Communication (수중 음향통신에 적합한 최적의 반복기반 터보 등화기 분석)

  • Park, Tae Doo;Lee, Seong Ro;Kim, Beom Mu;Jung, Ji Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.3
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    • pp.303-310
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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 and LDPC codes are dominant channel coding schemes in recent. This paper concluded that turbo coding scheme is optimal for underwater communications system in aspect to performance, coded word length, and equalizer combining. Also, we confirmed the performance in the environment of oceanic experimentation using turbo equalizer based on distance 5Km, data rate 1Kbps.

Analysis of PLL Phase Noise Effect for High Data-rate Underwater Communications

  • Lee, Chong-Hyun;Bae, Jin-Ho;Hwang, Chang-Ku;Lee, Seung-Wook;Shin, Jung-Chae
    • International Journal of Ocean System Engineering
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    • v.1 no.4
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    • pp.205-210
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    • 2011
  • High data-rate underwater communications is demanded. This demand imposes stringent requirements on underwater communication equipment of phase-locked-loop (PLL). Phase noise in PLL is unwanted and unavoidable. In this paper, we investigate the PLL phase noise effect on high order QAM for underwater communication systems. The phase noise model using power spectral density is adopted for performance evaluation. The phase noise components considered in PLL are reference oscillator, voltage controlled oscillator (VCO), filter and divider. The filters in PLL noise are assumed to be second order active and passive low pass filters. Through simulation, we analyze the phase noise characteristics of the four components and then investigate the performance improvement factor of each component. Consequently, we derive specifications of VCO, phase detector, divider to meet performance requirement of high data-rate communication using QAM under phase noise influence.

Adaptive Equalization using PDP Matching Algorithms for Underwater Communication Channels with Impulsive Noise (충격성 잡음이 있는 수중 통신 채널의 적응 등화를 위한 확률밀도함수 정합 알고리듬)

  • Kim, Nam-Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.10B
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    • pp.1210-1215
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    • 2011
  • In this paper, a supervised adaptive equalization algorithm based on probability density function (PDF) matching method is introduced and its decision-feedback version is proposed for underwater communication channels with strong impulsive noise and severe multipath characteristics. The conventional least mean square (LMS) algorithm based on mean squared error (MSE) criterion has shown to be incapable of coping with impulsive noise and multipath effects commonly shown in underwater communications. The linear PDF matching algorithm, which shows immunity to impulsive noise, however, has revealed to yield unsatisfying performance under severe multipath environments with impulsive noise. On the other hand, the proposed nonlinear PDF matching algorithm with decision feedback proves in the simulation to possess superior robustness against impulsive noise and multipath characteristics of underwater communication channels.

Performance Analysis of Underwater Communication Channel Using LDPC Codes in the MISO Channel (LDPC 부호를 이용한 MISO 채널에서 수중통신 채널 성능 분석)

  • Park, Tae-Doo;Kim, Min-Hyun;Lim, Byeong-Su;Jung, Ji-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.7B
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    • pp.878-885
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    • 2011
  • Due to reflect at surface of the water and limit bandwidth, it is difficult to design underwater acoustic communication systems with high-reliability and high transmission rate. Therefore the trends of underwater communication is transformed from single sensor to multiple sensor studies. However, underwater MIMO communication techniques have a high correlation value between multiple sensors on transmitters and receivers in underwater environments, it is difficult to expect space diversity gain on muli-path channels. Therefore, this paper proposed the MISO communications system with two transmit sensors and single receiver sensor, and analyzed its performance using the LDPC codes and channel compensation algorithm.