• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.191-197
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• 2017

According to the ubiquitous usage of smartphone, so many smartphone applications have been developed, and especially data communications and position measurement technologies without additional equipments have been developed using acoustic signal. But there is a limitation to select the frequency of the acoustic signal due to the smartphone hardware, and there is non-linearity in the electronic circuits in a sound generation devices, the audible sound generated from the speaker is not avoidable. And it causes critical difficulty to the commercial system deployment. In this paper, a simulation technique to calculate the power of the audible acoustic signal by human is applied to several types of acoustic signals to evaluate the loudness. These could be referred when the acoustic communications or positioning systems are designed, for the purposed of inaudible sounding to human.

• Information and Communications Magazine
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• v.33 no.8
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• pp.52-62
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• 2016

해양에서 음파를 사용하여 수중통신을 시도할 경우 해양매질은 음향 도파관(acoustic waveguide)의 역할을 하게 되고, 이 경우 해양환경의 변동성과 그에 따른 음파와 매질의 간섭에 의해 수중통신 채널의 변동성이 발생한다. 수중음향 채널은 대역 제한 채널이면서 잔향음 제한 채널이고 강한 도플러 변이 채널이므로 수신된 통신 신호는 육상통신에 비해 심한 인접 심볼간 간섭(intersymbol interference)과 위상변이를 가지게 된다. 따라서 수중통신을 시도함에 있어 이러한 해양환경 변동성과 그에 따른 수중음향 채널 변동에 대한 충분한 고려가 필요하다. 본 논문은 수중통신 시스템 구성에 도움을 줄 수 있도록 수중통신 채널에 영향을 미치는 해양 매질의 기본적 특성에 대해 소개하고 수중통신 채널과의 상관성 및 환경 변동성에 따른 통신채널의 변동성에 대해 소개하고자 한다.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.413-419
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• 2014

Underwater acoustic channel has time-variability. Time varying channel which disturbs the continuous transmission of information data reduces the underwater acoustic communication performance. In this paper, we show the temporal coherence as time-variability of channel and indicate throughput efficiency in accordance with transmission time of information data. Then we analyzed influence of underwater channel time-variability on communication throughput efficiency. We confirmed that the throughput efficiency reduced when the time-variability of the channel increased via lake trial.

• 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.21 no.1
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• pp.99-106
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• 2017

Audible Pedestrian Signal(APS) is an additional equipment to provide information about pedestrian signals in non-visual formats such as audible tones and verbal messages. It can provide information to pedestrians about the location and directions of a crosswalk, and the traffic signal status. In general, a pedestrian who is visually impaired uses a 358.5MHz wireless remote controller to activate the APS and crosses at the crosswalk with the help of the APS. The existing APS can only receive an activation message from the remote controller. Therefore, the APS has an issue, especially at intersections, that all APSs within the communication range of the remote controller are activated simultaneously. It makes to confuse the visual impaired pedestrians. In this paper, we propose a BLE-enabled APS that can enable two-way communication via Bluetooth with a smartphone. The proposed system solves the problem and provides them with additional information, so that visually impaired pedestrians can cross at the crosswalk more conveniently.

• Information and Communications Magazine
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• v.33 no.8
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• pp.82-88
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• 2016

본고에서는 은밀 수중음향통신과 관련한 연구동향과 수중 채널 환경의 특징들에 대해 소개한다. 육상 무선통신 환경과 마찬가지로 수중 채널에서도 전달 손실, 다중경로 전달, 도플러 효과 및 잡음이 장애 요인으로 작용하나 물 속의 상황을 정확히 예측하기 어렵고 시간에 따른 변동성이 매우 심하기 때문에 통신 시스템 설계를 어렵게 한다. 이러한 장애 요인들을 극복하면서 은밀 수중음향통신으로써 대표적인 대역확산 기법과 함께 수중 생체 모방형 신호를 사용하는 방법을 소개하고, 실제 국내 해역에서 획득한 데이터를 이용한 결과들을 제시한다.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.107-111
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• 2009

Acoustic OFDM is used for audible frequency band acoustic communication which employs loudspeaker as transmitter and microphone as the receiver antenna. Since acoustic OFDM can transmit about 1 kbps using 1600 Hz band. acoustic OFDM signal is inserted into the audio signal like music or speech, However. audio quality deteriorates definitely during the inserting process. This paper introduces a reason for audio quality deterioration and discuss how to reduce this phenomenon.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.179-182
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• 2004

수중음향통신을 위한 빔형성 알고리듬은 수중음향통신 신호가 상대대역폭(대역폭에 대한 반송주파수 비)이 큰 광대역 신호 특성을 고려해야한다. 우리는 본 논문에서 위상동기식 디지털 수중음향통신을 위한 협대역 신호 가정을 하지 않은 기저대역 배열 신호 모델을 유도하고 RLS 알고리듬을 이용하여 가중치를 갱신하는 FTR 필터 구조의 광대역 적응 빔형성 알고리듬에 대해서 전산 모의실험을 통하여 FIR 필터 길이, tap간 간격 등과 같은 최적의 FIR 필터 파라미터를 제시하였다.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.227-234
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• 2022

Covert Underwater Communication (CUC) signals should not be detected by other unintended users. Similar to the method used in Radio Frequency (RF), covert communication technique sending information underwater is designed in consideration of the characteristics of Low Probability of Detection (LPD) and Low Probability of Intercept (LPI). These conventional methods, however, are difficult to be used in the underwater communications because of the narrow frequency bandwidth. Unlike the conventional methods of reducing transmission power or increasing the modulation bandwidth, a method of mimicking the acoustic signal of an underwater mammal is being studied. The biomimetic underwater acoustic communication mainly mimics the click or whistle sound produced by dolphin or whale. This paper investigates biomimetic communication method and introduces research trends to understand the potential for the development of such biomimetic covert underwater acoustic communication and future research areas.

• 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.