• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.401-404
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• 2004

수중음향통신 관점에서 바다와 같은 수중채널은 수십심벌에 이르는 다중경로와 빠르게 변화하는 도플러 효과가 존재한다. 따라서 신뢰성 있는 수중음향통신을 위해서는 채널 등화가 반드시 필요하다. 본 논문에서는 이차 통계량 기반의 Blind Identification 알고리듬을 이용한 수중음향 채널추정 기법을 이용하여 무향수조의 채널응답을 분석하였다. 실험을 통하여 알고리듬의 추정 정확도 및 트랜스듀서 특성을 포함한 무향수조의 채널 응답 특성에 대하여 논한다.

• 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.

• Journal of the Korean Association of Geographic Information Studies
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• v.4 no.1
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• pp.18-26
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• 2001

Landsat TM band ratio algorithms were made by in-water optical measurement data of each sampling points for water quality monitoring of coastal area using Landsat TM satellite data. The algorithm was derived from in-water optical reflectance data which was measuring by the PRR(profiling reflectance radiometer). And, in-water optical reflectance data were applied to Landsat TM bands. Relationship between in-water optical reflectance and pigments proposed by the ratio of TM band 1 and band 2 showed to as follows; $Y=3.8352{\times}(R(band\;1)/R(band\;2))^{-2.1978}$ ($R^2$=0.7069) and, relationship of the ratio of TM band 1 and band 3 as follows; $Y=23.288{\times}(R(band\;1)/R(band\;3))^{-1.5243}$ ($R^2$=0.8062). Calculated the upwelling radiance of water surface and radiance of TM showed the ratio of atmospheric effect. In the coastal area Rayleigh and Mie scattering of atmosphere is to make over 80% of normalized radiance of Landsat TM. In order to apply in-water algorithm obtained by PRR, we had to calculate the atmospheric effects at sampling site. And, the quantitative analysis of in-water components using Landsat TM data need the calibration of in-water algorithm and effective method of atmospheric correction.

• 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.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2004.06a
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• pp.61-66
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• 2004

본 논문에서는 Tabu Search(TS) 알고리듬과 Simulated Anneal ing(SA) 알고리듬을 결합하여 향상된 성능을 갖는 컴퓨터 형성 홀로그램을 설계할 수 있는 방법을 제안하였다. 회절 효율의 향상을 위해 TS 알고리듬으로 이상적인 홀로그램에 근접한 패턴을 생성하고, 이를 SA 알고리듬에서 무작위로 구성된 초기 패턴과 대체하여 컴퓨터 형성 홀로그램을 설계하였다. 컴퓨터 모의 실험과 광 실험을 통하여 제안한 방법과 SA 알고리듬과의 성능을 비교한 결과 제안한 방법으로 재생한 영상이 SA 알고리듬을 이용하였을 때보다 향상된 회절 효율을 가지는 것을 확인 할 수 있었다.

• Journal of the Korean Association of Geographic Information Studies
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• v.4 no.1
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• pp.27-33
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• 2001

SDD(Secchi disk depth) algorithm were composed of SeaWiFS bands combination using in-water optical data sets obtained Lake Sihwa, Kyungki Bay, Chunsu Bay, and Chinhae Bay. SDD algorithm were compared with in-situ data. Reflectance band ratio, $R_{rs}$(490/665) had the highest correlation($R^2$=0.8188) with in-situ data. For in-water algorithm applied to satellite data, reflectance band ratios of Landsat TM data were calculated. However, the results of applied Landsat TM had the low correlation, these reason were discussed in this paper.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.4 s.310
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• pp.60-66
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• 2006

Underwater ultrasonic communication is critical to explore and development ocean using instrument. Essential to these applications is the reliable teleoperation and telemetering of the unit. But the problem is that the controllability of the instrument and the reliability of submarine communication are decreased, as so various passive noises are generated. In the existing methods, the control informations, received from an observation instrument, are identified used by hardware and repeatedly compared with standard information. However, such a method weakens the efficiency in controllability-centered systems. This study presents an ultrasonic signal detection algorithm that can identify the ultrasonic signal without the influence of disturbances due to underwater environmental changes. Likewise, the logicality of detection algorithm were ascertained by simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.299-306
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• 2011

In this paper, a blind adaptive equalization algorithm based on PDF-distance minimization and a set of Delta functions is introduced and its superior robustness against impulsive noise and multipath characteristics of underwater communication channels is proved. The conventional CMA based on MSE has shown to be incapable of coping with impulsive noise, and correntropy blind algorithm has also revealed to yield not satisfying performance for the mission. On the other hand, the blind adaptive equalization algorithm based on PDF-distance minimization and a set of Delta functions has been proved to solve effectively the problem of impulsive noise and multipath characteristics of underwater communication channels through theoretical and simulation analysis.

• 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.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.6-14
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• 1996

In this paper we present an algorithm to discriminate an underwater target under track against an acoustic counter-measure(ACM) source, based on a sequential hypothesis test. The ACM source is separated from the target under track and generates, while drifting, measurements with false range and Doppler information. The purpose of the ACM is to mislead the target-tracking and to help the true target evade a pursuer. The algorithm uses as a test statistic a function of the innovation sequences from extended Kalman filters to estimate the target dynamics and the drifting position of the ACM source. Numerical experiments on various scenarios show that the proposed algorithm discriminates the target against an ACM source very fast with a high probability of success.