• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.2
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• pp.57-64
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• 2015

In this paper, we propose structures and power spectral densities of UWB radar transmitters of Short Range Automobile. While the conventional transmitters did not consider interferences from self and other automobiles, the proposed method of this paper can minimize interferences. First, we compare a structure of the proposed method with pulse train and pulse compression method. Then, by using mathematical analysis and computer simulations, we show that the proposed method is superior to others. Also we can set proper parameters in UWB radar's transmitter through the numerical method of mathematical results.

• Communications of the Korean Mathematical Society
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• v.26 no.3
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• pp.427-443
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• 2011

In [6, 8], we showed that any ideal of $\mathbb{Z}_4[X]/(X^l\;-\;1)$ is generated by at most two polynomials of the `standard' forms when l is even. The purpose of this paper is to find the `standard' generators of the cyclic codes over $\mathbb{Z}_{p^a}$ of length a multiple of p, namely the ideals of $\mathbb{Z}_{p^a}[X]/(X^l\;-\;1)$ with an integer l which is a multiple of p. We also find an explicit description of their duals in terms of the generators when a = 2.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1247-1250
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• 2005

이 논문은 multicarrier CDMA 이동 통신 시스템에서 직-병렬 혼합 pseudo-noise (PN) 코드 동기 획득 기술을 제안 했으며 다중경로 페이딩 채널에서 multiple access interference (MAI) 의 영향을 분석하였다. 직-병렬 혼합 동기 획득 방식은 입력되는 코드 위상의 불확정 영역 전체를 직렬 획득 방식과 병렬 획득 방식을 조합하여 탐색하는 방식이다. 이러한 방식은 완전 병렬획득보다 MAI의 환경에서 mean acquisition time (MAT)이 조금 늦어지지만 하드웨어의 구조를 훨씬 단순화 할 수 있다. 검파 및 오경보 확률을 closed-form 표현으로 mean acquisition time (MAT)를 유도하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5B
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• pp.599-607
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• 2001

이 논문에서는 부호와 순위를 바탕으로 한 비모수 검파기를 쓰는 직접수열 대역확산 시스템의 의사잡음 부호획득을 다루었다. 먼저 국소 최적 순위 검파기의 검정통계량을 얻고, 점근 점수 함수를 쓰는 국소 준최적 순위 검파기와 변형 부호순위 검파기의 검정통계량을 제외한다. 제안한 국소 준최적 순위 검파기와 변형 부호순위 검파기를 쓴 한 우물기법과 이제까지의 제곱합 검파기와 변형 부호 검파기를 쓴 것을 견주어 본다. 제안한 국소 준최적 순위 검파기와 변형 부호순위 검파기의 성능이 이제까지의 변형 부호 검파기의 성능보다 2-3dB쯤 낮고, 거의 최적임을 모의실험을 통해 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1411-1418
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• 1997

This paper presents a statistical analysis of the decision throeshold for derect-sequence spread-spectrum (DS-SS) prallel Pseudo-Noise (PN) code acquistion with a reference filter. The probabilities of detection and false alarm are derived, and the mean acquistion time is evaluated as a measure of the system performance in both nonfading and Rician fiding channels. From the statistical sresults, it is shown that in the performance analysis of the parallel acquisition system with reference filtering, the statistical evaluaion of the decision threshold seems more appropriate than the approximation of the decision threshold adopted in the other schemes[2,3].

• Journal of the Korea Society of Computer and Information
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• v.5 no.2
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• pp.121-129
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• 2000

The fuzzy-based SAM algorithm is proposed in this thesis to reduce the idle time. to recover call truncation fast when it is handed off and to last frequency acquisition in the mobile communications. It has additive and adaptive elements. Its weight values are generated not by feedback but by input conversion values. The initial expectation value is defined and forwardㆍbackward searching is executed 4o produce the expectation value of one chip. The fuzzy-based SAM algorithm is applied to the demodulator in CDMA system, and the synchronization time is measured. Synchronization time of PN code is 1.678$\mu\textrm{s}$ by SAM algorithm. It is 993 times faster than time of the conventional systems, 1.667$\mu\textrm{s}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1803-1813
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• 1996

This paper describes an automatic threshold decision using a maximum mismatched correlation value in the direct sequence spread spectrum (DS-SS) system. For received PN codes with different single-to-noise ratio (SNR), this scheme is able to detect a desired threshold value in the search mode, i.e. a maximum mismstched correlation value, so that value is utilized as a threshold for the verification mode. Performance of the proposed scheme in both the additive white gaussian noise (AWGN) and frequency-selective Rayleigh fading channels is analyzed through the Monte Carlo simulation. And hardware implementation of this scheme using a DSP processor is demonstrated. The proposed acquisition shceme is compared to the conventional constant threshold (CT) scheme, and significant improvement of performance is shown. Analysis of system performance in the verification mode is presented, and key quantities such as the false alarm probability and the detection probability are derived in a AWGN channel.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.557-564
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• 2000

This paper presents a watermarking algorithm for embedding visually recognizable pattern (Mark, Logo, Symbol, stamping or signature) into the image. first, the color image(RGB model)is transformed in YCbCr model and then the Y component is transformed into 3-level wavelet transform. Next, the values are assembled with pattern watermark. PN(pseudo noise) code at spread spectrum communication method and mutilevel watermark weights. This values are inserted into discrete wavelet domain. In our scheme, new calculating method is designed to calculate wavelet transform with integer value in considering the quantization error. and we used the color conversion with fixed-point arithmetic to be easy to make the hardware hereafter. Also, we made the new solution using mutilevel threshold to robust to common signal distortions and malicious attack, and to enhance quality of image in considering the human visual system. the experimental results showed that the proposed watermarking algorithm was superior to other similar water marking algorithm. We showed what it was robust to common signal processing and geometric transform such as brightness. contrast, filtering. scaling. JPEG lossy compression and geometric deformation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.6
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• pp.279-285
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• 2006

Power line communication channels are very complicated and models for communication channels vary with the types of electrical equipment, devices and load fluctuations. So, modeling and analysis of power line channels for implementation of power line communication systems is a very important process. Power line channel modeling and simulation are performed based on power system transient simulation models and power system CAD tools to create precise and accurate models. In this paper, a channel modeling and simulation method is proposed for power line communication systems using PSCAD/EMTDC, in which a PN 63 sequence code generator is applied for impulse response of the power line channel in the simulation model.