• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.467-475
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• 1999

This paper presents an algorithm for scheduling jobs in soft real-time systems. To simplify the scheduling for soft real-time systems, we introduce two-level deadline scheme. Each job in the system has two deadlines, which we call first-level and second-level deadlines, respectively. The first-level deadline is the same as the deadline in traditional real-time systems. The second-level deadline is later than the first-level deadline, and defines the latest point in time when the result is still acceptable. Partial-credit is given for jobs meeting the second-level deadline but missing the first-level deadline, whereas jobs meeting the latter are given full credit. We heuristically compute priorities of jobs in a dynamic way by combining the first-level adn second-level deadlines with the partial-credit. Simulation results indicate that our two-level scheduling algorithm is a viable approach for dealing with both soft real-time systems and temporary overloaded hard real-time systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1433-1443
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• 2004

The power line modem proposed in this paper transmits the remote control signal using CSK(Code Shift Keying) and DS/SS method. The CSK technique provides the increased capacity of transmission and robustness towards noise. Besides, the DS/SS technique provides protection against narrow-band Gaussian interference and multi-path interference. The modem supports full-duplex communication using FDD(Frequency Division Duplex) and the modem structure for forward link is same with that for reverse link. To switch each sub-controlled unit smoothly, 4/$\pi$-DQPSK is adopted for noncoherent demodulation. The PN code for spreading spectrum seues to divide each group which consists of sub-controlled units and Walsh code is used for the M-ary CSK technique. Each block is designed and verified with TMS320C5402 DSP. We show the superiority of the proposed method by analyzing numerically the system performance for the factors of the DS/SS and CSK method ullder additive white Gaussian noise and PBI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1925-1938
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• 2001

In this paper, a new block-matching algorithm for standard video encoder is presented. The slice competition method is proposed as a new scheme, as opposed to a coarse-to-fine approach. The order of calculating the SAD(Sum of Absolute Difference) to fad the best matching block is changed from a raster order to a dispersed one. Based on this scheme, the increasing SAD curve during its calculation is more linear than that of other curves. Then, the candidates of low probability can be removed in the early stage of calculation. And new MV prediction technique with an adaptive search range scheme also assists the proposed block-matching algorithm. As a result, an average of 13% improvement in computational power is recorded by only the proposed MV prediction technique. Synthetically, the computational power is reduced by 3977∼77% than that of the conventional BMAs. The average MAD is always low in various sequences. The results are also very close to the MAD of the full search block-matching algorithm.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.1013-1024
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• 2015

We compare the performance of two representative estimation methods for the dynamic conditional correlation (DCC) GARCH model. The first method is the pairwise estimation which exploits partial information from the paired series, irrespective to the time series dimension. The second is the multi-dimensional estimation that uses full information of the time series. As a simulation for the comparison, we generate a multivariate time series similar to those observed in real markets and construct a DCC GARCH model. As an empirical example, we constitute various portfolios using real KOSPI 200 sector indices and estimate volatility and VaR of the portfolios. Through the estimated dynamic correlations from the simulation and the estimated volatility and value at risk (VaR) of the portfolios, we evaluate the performance of the estimations. We observe that the multi-dimensional estimation tends to be superior to pairwise estimation; in addition, relatively-uncorrelated series can improve the performance of the multi-dimensional estimation.

• Information Systems Review
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• v.5 no.2
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• pp.37-51
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• 2003

Mobile business noticed as a constructive alternative of e-commerce and e-business is being diversely considered as a new form or subset of e-business. In this study, mobile business is defined as a comprehensive alternative including e-business. The framework of the superset of e-business has two axes: connectivity and mobility. In addition, various cases based on the combination of the components are provided and explained. It is the main characteristic of this study that the element of off-line "mobility" is added to "connectivity" generally used while explaining e-commerce and e-business. For place (or location) is a prerequisite for the feature of mobility, we grope for why and how Location-Based Service (LBS) will take an important role in the development of new e-business models and services. As the real and full-scale beginning of IMT-2000 service and the rapid progress and diffusion of mobile communications services including wireless LAN require an immense and innovative way of thinking about e-commerce and e-business, the framework suggested in this study is considered to go far toward satisfying the new needs in this area.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2006.06a
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• pp.730-736
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• 2006

In this paper, we propose a rotation resistant robust logo embedding watermarking technique. Geometric manipulations make the detection process very complex and difficult. Watermark embedding ill the normalized image directly suffers from smoothing effect due to the interpolation during the image normalization. This can be avoided by estimating the transform parameters using image normalization technique, instead of embedding in the normalized image. Conventional rotation resistant schemes that use full frame transform. In this paper, we adopt $8{\times}8$ block DCT and calculate masking using a spatio-frequency localization of the $8{\times}8$ block DCT coefficients. Experimental results show that the proposed algorithm is robust against rotation process.

• Journal of Intelligence and Information Systems
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• v.19 no.1
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• pp.1-17
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• 2013

In this article, several types of hybrid forecasting models are suggested. In particular, hybrid models using the generalized additive model (GAM) are newly suggested as an alternative to those using neural networks (NN). The prediction performances of various hybrid and non-hybrid models are evaluated using simulated time series data. Five different types of seasonal time series data related to an additive or multiplicative trend are generated over different levels of noise, and applied to the forecasting evaluation. For the simulated data with only seasonality, the autoregressive (AR) model and the hybrid AR-AR model performed equivalently very well. On the other hand, if the time series data employed a trend, the SARIMA model and some hybrid SARIMA models equivalently outperformed the others. In the comparison of GAMs and NNs, regarding the seasonal additive trend data, the SARIMA-GAM evenly performed well across the full range of noise variation, whereas the SARIMA-NN showed good performance only when the noise level was trivial.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.394-402
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• 2009

In this paper, we present a new analytical model for estimating the blocking performance of multi-fiber WDM networt:s with sparse and limited wavelength conversion (SLWC). The proposed model is a reduced-load approximation model that can obtain accurate estimates of blocking probability of such networks. Our model employs three new recurrence formulae to obtain the free wavelength distribution on a multi-fiber link, the free wavelength distribution after limited-range wavelength conversion and the end-to-end blocking probability of a multi-hop path, respectively. From the numerical results on the NSFNET, we demonstrate that the blocking performance of two-fiber NSFNET with three wavelength-convertible nodes, each of which translates an input wavelength to its adjacent output wavelengths, closely approximates the blocking performance of full wavelength conversion.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.22 no.3
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• pp.353-371
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• 2011

The purpose of this paper is to analyze the interrelation among research areas based on domestic journal papers, achievements of korea researchers. Generally, the content of papers is appeared through abstracts, subjects, full-text and so on. This paper is focused on subject terms of Domestic journal papers. The experimental data are 80 domestic journals, 7,616 papers and 58,143 subject terms and papers published in 2009. As the result, it was different to use subject terms on each research area: Engineering, Agriculture & Oceanography, Interdisciplinary Science, Social Science, Arts & Physical Education, Medicine & Pharmacology, Humanities and Natural Science. Subject terms of Engineering have used the most in the other research areas in aspect of term co-occurrence. The 8 research areas were grouped in 3 clusters: C1(Engineering, Natural Science, Social Science, Interdisciplinary Science, Humanities), C2(Medicine & Pharmacology, Arts & Physical Education), and C3(Agriculture & Oceanography).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1056-1063
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• 2008

This paper describes an efficient design of a multi-standard Viterbi decoder that supports multiple constraint lengths and code rates. The Viterbi decoder is parameterized for the code rates 1/2, 1/3 and constraint lengths 7,9, thus it has four operation nodes. In order to achieve low hardware complexity and low power, an efficient architecture based on hardware sharing techniques is devised. Also, the optimization of ACCS (Accumulate-Subtract) circuit for the one-point trace-back algorithm reduces its area by about 35% compared to the full parallel ACCS circuit. The parameterized Viterbi decoder core has 79,818 gates and 25,600 bits memory, and the estimated throughput is about 105 Mbps at 70 MHz clock frequency. Also, the simulation results for BER (Bit Error Rate) performance show that the Viterbi decoder has BER of $10^{-4}$ at $E_b/N_o$ of 3.6 dB when it operates with code rate 1/3 and constraints 7.