• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.700-707
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• 2014

In this paper, we propose the noise reduction method by using the eigenfilter in cyclic prefix system based on SNR. To obtain the signal eigenvectors for the eigenfiltering, we propose a method of obtaining the autocorrelation matrix by exploiting the circulant property of the received block which results from the cyclic extension of the OFDM symbol. Since the structures of the transmitter and the receiver are not changed, the proposed method is easy to apply to the conventional OFDM system. To verify the proposed method, we evaluate the persistency of excitation (POE) criterion for the input and demonstrate the effectiveness of the proposed method in the simulation results.

• The Korean Journal of Applied Statistics
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• v.35 no.1
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• pp.77-91
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• 2022

The optimal threshold estimation is considered in order to discriminate the mixture distribution in the fields of Biostatistics and credit evaluation. There exists well-known various accuracy measures that examine the discriminant power. Recently, Matthews correlation coefficient and the F1 statistic were studied to estimate optimal thresholds. In this study, we explore whether these accuracy measures are appropriate for the optimal threshold to discriminate the mixture distribution. It is found that some accuracy measures that depend on the sample size are not appropriate when two sample sizes are much different. Moreover, an alternative method for finding the optimal threshold is proposed using the correlation coefficient that defines the ratio of the confusion matrix, and the usefulness and utility of this method are also discusses.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.403-408
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• 2005

The techniques of estimating angle of arrival(AOA) have played a key role for enhancement of wireless communications using array antennas. Among those techniques, the superresolution algorithms, such as MUSIC and ESPRIT, calculate the covariance matrix of the array output vectors which are observed at the array antennas, and then by using eigen-decomposition of the covariance matrix, they estimate AOAs of the received signals with high accuracy. However, superresolution algorithms based eigenvalue decomposition fails to estimate AOAs under multipath environments. Under multipath environments, it is difficult to estimate AOAs of the received signals due to coherency and high-correlation. To resolve coherent signals, the covariance matrix is calculated by using the conventional spatial smoothing technique, and then the techniques based on eigen-descomposition is applied. The result of the conventional spatial smoothing technique, however, is obtained at the cost of losing effective spatial aperture. Moreover, the conventional technique ignores any information in the cross-correlations of the array outputs the subarrays. As the result, the performance for AOA estimation is degraded. In this paper, we propose a new spatial smoothing technique, which consider the cross-correlation for subarrays. By computer simulation, the AOA estimation performance of the proposed method is compared with the conventional method and evaluated.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.385-392
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• 2015

Principal component analysis (PCA), a dimension-reduction technique, is usually implemented after the variables are standardized when the measurement unit of variables are different. To standardize a variable we divide it by its standard deviation. But there is another way to transform a variable to be independent of its measurement unit. It is to divide it by its mean rather than standard deviation. Implementing PCA on standardized variables is equivalent to implementing PCA with a correlation matrix of original variables. Similarly, implementing PCA on the transformed variables divided by their means is equivalent to implementing PCA with a matrix related to the coefficients of variation of the original variables. We explain why we need to implement PCA on the variables transformed by their means.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.423-428
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• 2004

High-data rate and high speed communication techniques are required for wireless mobile communication systems to provide multimedia services. A multiple antenna technology may be used to meet this demand. In this paper, a method for performance improvement of a WCDMA downlink system using space time block coding is proposed in quasi-static Rayleigh fading channels. The proposed receiver uses the cross correlation matrix obtained by each finger corresponding to multi paths. To obtain maximum diversity gain, the inverse of cross correlation matrix and the Hermitian matrix of the channel matrix for each path arc computed, and then applied to received signals. Various simulation results show that the proposed receiver outperforms a conventional receiver in Rayleigh fading channels.

• The Korean Journal of Applied Statistics
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• v.28 no.2
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• pp.151-158
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• 2015

This paper discusses how to use projections for the analysis of data from balanced incomplete block designs. A model is suggested as a matrix form for the interblock analysis. A second set of treatment effects can be found by projections from the suggested interblock model. The variance and covariance matrix of two estimated vectors of treatment effects is derived. The uncorrelation of two estimated vectors can be verified from their covaraince structure. The fitting constants method is employed for the calculation of block sum of squares adjusted for treatment effects.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2239-2241
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• 2004

이 논문은 최적 제어 설계방법 중 하나인 LQR 제어기의 과도 상태를 개선하는 방법에 관한 연구이다. 적절한 상태가중행렬과 제어가중행렬을 설정한 후 대수 Riccati 방정식을 풀면 LQR 제어기가 설계된다. 그런데 이 가중행렬은 시행착오 방법을 이용하여 설정하기 때문에 설계된 제어기의 과도 상태를 개선하기 하기가 매우 어렵다. 이러한 문제점을 해결하기 위한 방법으로 closed-loop 근과 가중행렬과의 상관관계를 수학적으로 표현하고, 이를 바탕으로 설계조건을 만족하도록 시스템의 근을 이동시키는 가중행렬을 구하는 방법을 제시한다. 원운동형 도립진자(rotary type inverted pendulum)를 통해 matlab 모의실험으로 그 타당성을 검증한다. 얻어진 결과를 이용하면 원하는 극점을 갖는 LQR 제어기를 체계적으로 설계할 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.133-135
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• 2020

최근 CNN(Convolutional Neural Network)은 영상 분류, 객체 인식 등 다양한 비전 분야에서 우수한 성능을 보여주고 있으나, CNN 모델의 계산량 및 메모리가 매우 커짐에 따라 모바일 또는 IoT(lnternet of Things) 장치와 같은 저전력 환경에 적용되기에는 제한이 따른다. 따라서, CNN 모델의 임무 성능을 유지하연서 네트워크 모델을 압축하는 기법들이 연구되고 있다. 본 논문에서는 행렬 분해 기술인 저계수행렬 근사(Low-rank approximation)와 CP(Canonical Polyadic) 분해 기법을 결합하여 CNN 모델을 압축하는 기법을 제안한다. 제안하는 기법은 계층의 유형에 상관없이 하나의 행렬분해 기법만을 적용하는 기존의 기법과 달리 압축 성능을 높이기 위하여 CNN의 계층 타입에 따라 두 가지 분해 기법을 선택적으로 적용한다. 제안기법의 성능검증을 위하여 영상 분류 CNN 모델인 VGG-16, ResNet50, 그리고 MobileNetV2 모델 압축에 적용하였고, 모델의 계층 유형에 따라 두 가지의 분해 기법을 선택적으로 적용함으로써 저계수행렬 근사 기법만 적용한 경우 보다 1.5~12.1 배의 동일한 압축율에서 분류 성능이 향상됨을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.111-123
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• 2019

In this paper, we propose a method for defining the input termination for on-wafer-type device under test (DUT) measurement. Using the newly defined input termination and noise wave correlation matrix (NWCM) measurement method based on noise power ratio, the NWCM of the on-wafer-type DUT was measured. We demonstrate a noise measurement configuration that includes wafer probes and bias tees to measure the on-wafer DUT. The S-parameter of the adapter that combines the bias tee, probe, and a line terminated by open is required to define the input termination for on-wafer DUT measurement. To measure the S-parameter of the adapter, a 2-port S-parameter measurement method using 1-port measurement is introduced. Using the measured S-parameters, a method for defining the new input termination for on-wafer-type DUT measurement is applied. The proposed method involves the measurement of the NWCM of the chip with a 1.5 dB noise figure. The noise parameters of the chip were obtained using the measured NWCM. The results indicate that the obtained values of the noise parameters are similar to those mentioned on a datasheet for the chip. In addition, repeated measurements yielded similar results, thereby confirming the reliability of the measurements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.77-84
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• 2011

This study is to develop nonlinear analysis algorithm for transfer matrix method, which can be applied to continuous beam analysis. Gauss-Lobatto integral rule is adopted and the transfer matrix is derived from stiffness matrix. In the transfer matrix method, the system equation has a constant number of unknowns regardless of number of D.O.F. Therefore, the transfer matrix method has computational efficiencies not only in linear elastic analysis but also in nonlinear analysis. To verify the developed method, the analysis results of several examples are compared with commercial code in moment-curvature, moment-displacement and load-displacement relation.