• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1051-1057
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• 2009

USN(Ubiquitous Sensor Network) is used to provide many services such as bridge monitoring, cultural properties monitoring, river monitoring, protection of an old and feeble person, management and control of a city and circumstance monitoring, etc. A RF transceiver is needed for implementing USN. In this paper the implementation and the design of a RF transceiver for sensor nodes operating in 2.4GHz frequency band are presented. The design procedure of AGC, a receiver and a transmitter is described. And the performance of the implemented RF transceiver is also tested. The test results of receiver sensitivity, receiver dynamic range, frequency stability, phase noise, output power of transmitter, flatness and spectrum mask are presented.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.5
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• pp.541-548
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• 2003

Species identification in hydroacoustic survey is one of the key requirements to estimate biomass of organism and to understand the structure of zooplankton community. Feasibility of species identification using two frequencies (38 and 120 kHz) was investigated on the basis of mean volume backscattering strength difference (MVBS). Virtual echogram technique was applied to two frequencies data sets that obtained from surveys in the Antarctic Ocean and Yellow Sea. Virtual echogram method using MVBS revealed the possibility of species identification, which species identification relying on visual scrutiny of single frequency acoustic data resulted in significant errors in biomass estimation. Through noise cancellation using MVBS, much of the acoustic noise caused by acoustic instruments could be removed in new virtual echogram, and the biomass estimation and data quality was improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.279-287
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• 2001

In this paper, we discuss the scale of subjective speech quality measurement over VoIP(Voice over IP) network which is a component of broadband networks. Objective parameters of multimedia services like PSNR or jitter can easily measured and defined, but these factors are not easily meet the user's perceptual recognition. We suggest the speech quality measurement scale through the subjective measurement for end-to-end speech quality composed of sender-side quality, transmission quality, receiver-side quality, which provide the degree of correctness of representation of speaker, the degree of impairment caused by various factors, the degree of recognition of processed speech, respectively. Also, we examined the proposed method and verify it's availability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.948-958
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• 2010

Human body signals collected by the MRI system are very weak, such that they may be easily affected by either external noise or system instability while being imaged. Therefore, this paper analyzes the nonuniformity caused by a design of the RF receiving coil in a low-magnetic-field MRI system, and proposes an efficient method to improve the image uniformity. In this paper, a method for acquiring 3D bias volume data by using phantom data among various methods for correcting such nonuniformity in MRI image is proposed, such that it is possible to correct various-sized images. It is shown by simulations that images obtained by various imaging methods can be effectively corrected using single bias data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1262-1267
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• 2005

Elliptical basis function (EBF) neural network works stably under high-level background noise environment and makes the nonlinear processing possible. It can be adapted real time VAD with simple design. This paper introduces VAD implementation using EBF and the experimental results show that EBF VAD outperforms G729 Annex B and RBF neural networks. The best error rates achieved by the EBF networks were improved more than $70\%$ in speech and $50\%$ in silence while that achieved by G.729 Annex B and RBF networks respectively.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.01a
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• pp.407-408
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• 2014

본 논문에서는 이동환경 및 이동부하를 측정하여 그 특성을 조사하기 위하여 간편하게 측정할 수 있는 휴대용 모니터링 장비를 개발하였다. 온습도 및 가속도, 생체신호를 동시에 측정할 수 있다. 본 장비의 현장적용실험을 위해 공항터미널 이용 시의 상태변화를 측정하였다. 그 결과, 이동환경에서 사용하는데 있어 간편성을 가지는 반면 추후 동잡음 제거, 피험자 편의성 등이 보완 되어야 할 것이다.

• The Journal of Korean Association of Computer Education
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• v.9 no.2
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• pp.101-109
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• 2006

We propose an adaptive digital watermarking algorithm using HVS(human visual system) and SOM(Self-Organizing Map) among neural networks. This method adjusts adaptively the strength of the watermark which is embedded in different blocks according to block classification in DCT(Discrete Cosine Transform) domain. All blocks in 3 classes out of 4 are selected to embed a watermark. Watermark sequences are embedded in 6 lowest frequency coefficients of each block except the DC component. The experimental results are excellent.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1055-1063
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• 2014

Recently, various methods have been proposed for improving the performance of the side channel analysis using the power consumption. Of those method, waveform compression method applies to reduce the noise component in pre-processing step. In this paper, we propose the new LDA(Linear Discriminant Analysis)-based signal compression method finding unique feature vector. Through experimentations, we are comparing the proposed method with the PCA(Principal Component Analysis)-based method which has known for the best performance among existing signal compression methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.583-586
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• 2004

In this paper, we have analyzed the performance of synchronization of CCK(Complementary Code Keying) modulation scheme used for IEEE 802.11g wireless LAM system supporting 54 Mbps of high speed data rate over 2.4 GHz. At receiver, the clock frequency offset is caused by noise or fading. This frequency error occurs the offset of clock timing and causes ISI. Therefore the tracking is required to reduce the clock timing offset. The DLL(Delay Lock Loop), asychronization mode, performing tacking the clock is used for the simulation. The simulation result shows jitter variance and BER performance in the AWGN and multipath fading channel environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.316-321
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• 2007

[ $H{\infty}$ ] controller, which shows robustness for disturbances and noises, can not be used in the case of uncertain system parameters. Even if the $H{\infty}$ controller can be designed for the parameter uncertain system, its performance can be deteriorated. Therefore, in this paper, the robustness of $H{\infty}$ controller is improved by using the SMC(Sliding Mode Control). The LMI based $H{\infty}$ controller is designed first and then SMC controller is added.