• The KIPS Transactions:PartB
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• v.10B no.5
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• pp.485-490
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• 2003

In this paper, we propose the possibility of introducing chaotic sequences into digital watermarking systems as potential substitutes to commonly used pseudo noise sequences. Chaotic sequences have several good properties including the availability of a great number of them, the ease of their generation, as well as their sensitive dependence on their initial conditions. And the quantization does not destroy the good property. So this paper proposes a method that transforms Hangul text to chaotic sequence. And we presents how the Hangul text is expressed by an implied data and the implied data is regenerated into the original text. In this paper, we use this implied Hangul text for watermarking.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.226-233
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• 2007

In this paper, we construct new LCZ sequence sets with parameters $(2^{n+1}-2,M,L,2)$. In this scheme, we can relatively freely choose the LCZ length L and the resulting LCZ sequence set has the size in which is nearly optimal with respect to Tang, Fan, and Matsufuji bound.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.1
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• pp.97-104
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• 2011

Pseudo-random sequences with high linear complexity and low correlation function values are widely used in communication and cryptology. In this paper, we study the properties of interleaved sequences generated by shrinking generator. And we give a method for obtaining the shrunken sequence from a partial description of the shrunken sequence by using the phase shifting of PN sequences generated by shrinking generator.

• Journal of Korea Multimedia Society
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• v.17 no.11
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• pp.1279-1285
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• 2014

In this paper, we propose on image encryption method which uses NC(Non-linear Cycle) and 2D CAT(Two-Dimensional Cellular Automata Transform) in sequence to encrypt medical images. In terms of the methodology, we use NC to generate a pseudo noise sequence equal to the size of the original image. We then conduct an XOR operation of the generated sequence with the original image to conduct level 1 NC encryption. Then we set the proper Gateway Values to generate the 2D CAT basis functions. We multiply the generated basis functions by the altered NC encryption image to conduct the 2nd level 2D CAT encryption. Finally, we verify that the proposed method is efficient and extremely safe by conducting an analysis of the key spatial and sensitivity analysis of pixels.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.75-87
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• 1980

Most hydro]ogic phenomena are the complex and organic products of multiple causations like climatic and hydro-geological factors. A certain significant correlation on the run-off in river basin would be expected and foreseen in advance, and the effect of each these causual and associated factors (independant variables; present-month rainfall, previous-month run-off, evapotranspiration and relative humidity etc.) upon present-month run-off(dependent variable) may be determined by multiple regression analysis. Functions between independant and dependant variables should be treated repeatedly until satisfactory and optimal combination of independant variables can be obtained. Reliability of the estimated function should be tested according to the result of statistical criterion such as analysis of variance, coefficient of determination and significance-test of regression coefficients before first estimated multiple regression model in historical sequence is determined. But some error between observed and estimated run-off is still there. The error arises because the model used is an inadequate description of the system and because the data constituting the record represent only a sample from a population of monthly discharge observation, so that estimates of model parameter will be subject to sampling errors. Since this error which is a deviation from multiple regression plane cannot be explained by first estimated multiple regression equation, it can be considered as a random error governed by law of chance in nature. This unexplained variance by multiple regression equation can be solved by stochastic approach, that is, random error can be stochastically simulated by multiplying random normal variate to standard error of estimate. Finally hybrid model on estimation of monthly run-off in nonhistorical sequence can be determined by combining the determistic component of multiple regression equation and the stochastic component of random errors. Monthly run-off in Naju station in Yong-San river basin is estimated by multiple regression model and hybrid model. And some comparisons between observed and estimated run-off and between multiple regression model and already-existing estimation methods such as Gajiyama formula, tank model and Thomas-Fiering model are done. The results are as follows. (1) The optimal function to estimate monthly run-off in historical sequence is multiple linear regression equation in overall-month unit, that is; Qn=0.788Pn+0.130Qn-1-0.273En-0.1 About 85% of total variance of monthly runoff can be explained by multiple linear regression equation and its coefficient of determination (R2) is 0.843. This means we can estimate monthly runoff in historical sequence highly significantly with short data of observation by above mentioned equation. (2) The optimal function to estimate monthly runoff in nonhistorical sequence is hybrid model combined with multiple linear regression equation in overall-month unit and stochastic component, that is; Qn=0. 788Pn+0. l30Qn-1-0. 273En-0. 10+Sy.t The rest 15% of unexplained variance of monthly runoff can be explained by addition of stochastic process and a bit more reliable results of statistical characteristics of monthly runoff in non-historical sequence are derived. This estimated monthly runoff in non-historical sequence shows up the extraordinary value (maximum, minimum value) which is not appeared in the observed runoff as a random component. (3) "Frequency best fit coefficient" (R2f) of multiple linear regression equation is 0.847 which is the same value as Gaijyama's one. This implies that multiple linear regression equation and Gajiyama formula are theoretically rather reasonable functions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.47-55
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• 2010

The power line communication channel has characteristic variation problems which are caused by load. The spread spectrum technique has been used to overcome these problems. One of that is the direct sequence spread spectrum(DS/SS) system which is not necessary to additional hardwares. The BER of DS/SS system is decreased by longer length of PN code, but data transfer rate is decreases, so data transfer rate is hard to satisfies their own specifications especially in narrowband PLC systems. Spread Spectrum system with Dual-processing Gain tries to reflect cyclic characteristics of power line noise. But that system assumes that shapes of power line channel are symmetrical with respect to the 1/4 point of main frequency(60Hz in Korea), therefore cannot achieves various shapes of real power line noise. Thus in this paper, noise adaptive DS/SS system which PN code is changed by noise levels for various channel noises is proposed and simulated. The different kinds of noises are modeled and measured for simulation, the proposed system is verified that has lower data transfer rate and lower error rate than conventional system by simulation results.

• Proceedings of the IEEK Conference
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• 2003.07d
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• pp.1487-1490
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• 2003

This paper shows the watermarking system that inserts copyright holder's logo in music file. In other words, a sound file is able to have an image information like a logo or letters. The watermarking system converts a sound file into an image file using spectrogram. In the spectrogram domain, a logo is inserted using spread spectrum. The proposed technique shows that the verification of copyright is better than the method using PN-Sequence.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1997.11a
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• pp.127-135
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• 1997

In this paper, we apply a digital modulation scheme called Multi-Carrier Code Division Multiple Access (MC-CDMA) in which data symbols are transmitted at multiple subcarriers. Each subcarrier is encoded with a phase offset of -π or π based on a pseudo-random noise(PN) sequence. MC-CDMA scheme is introduced to combat against the multipath fading. We annalize above system and derive the average probability of error in AWGN and Rayleigh fading environment.

• Proceedings of the Korea Database Society Conference
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• 2000.11a
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• pp.358-363
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• 2000

본 논문에서는 디지털오디오 원시 데이터의 양에 따라 적당한 양의 오디오워터마크를 생성, 삽입하여 일정한 수준의 오디오데이터의 품질을 유지하도록 하는 적응적 워터마킹을 제안한다. 제안하는 알고리즘은 심리음향모델인 frequency masking과 Wavelet 변환의 개념을 적용한다. 저작권자 혹은 소유자의 데이터는 PN-sequence를 이용하여 생성된다. 워터마크 생성량의 조절은 특정한 모듈이 담당하게 되는데 이 모듈은 원시 데이터의 크기에 따라 워터마크의 적당한 양을 산출하여 오디오데이터의 품질을 유지하도록 한다.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.8
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• pp.1-7
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• 1997

In tis paper, w eproposed a modeling for direct-sequence spread communication base band modem in RT-level VHDL and implemented in a one-chip VLSI and tested. The transmitter modulates with DQPSK modulation method and spreads a modulated signal with 32-bit PN code into 1.152MHz. The receiver de-spreads a signal using 32-tap matched filter and recovers with DQPSK demodulation method. The digital frequency synthesizer generates the sine signal and the cosine signal of 2.304MHz with ROM tables in the size of 7$\^$*/256 and 6$\^$*/256, respectively. The implemented VLSI has been verified a BER with 10$\^$-4/ at E$\_$b//N$\_$o/ of 13dB with a SPW fixed design model and fabricated in the 0.8.mu.m KG6423 gate array with a VHDL model.