• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5A
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• pp.484-492
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• 2006

A multi-code biorthogonal code keying(MBCK) system consists of multiple waveform coding block, and the sum of output codewords is transmitted. Drawback of MBCK is that it requires amplifier with high linearity because its output symbol is multi-level. MBCK with constant amplitude preceding blcok(CA-MBCK) has been proposed, which guarantees sum of orthogonal codes to have constant amplitude. Redundant bits of CA-MBCK for constant amplitude coding are not only used to make constant amplitude signal but also used to improve the bit error rate(BER) performance at receiver. In this paper, we proposed a transmission scheme which combine CA-MBCK with $Q^{2}PSK$ to improve bandwidth efficiency of CA-MBCK. The BER performance of the scheme is same that of CA-MBCK in additive white gaussian noise(AWGN). And we showed that BER performance of the proposed system can be improved using redundant bits of constant amplitude preceding.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.4
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• pp.25-34
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• 2000

In this paper, we first investigate the effect of residual code phase offset on the DS/CDMA code acquisition scheme. When the code phase offset normalized to the chip duration is within the advancing step size, the sum of two successive matched filter outputs has a constant value regardless of the residual code phase offset if noise is absent. Based on this observation, we propose a new code acquisition scheme, and investigate the performance of the scheme. The Proposed code acquisition scheme is analyzed, and numerical results are given to show that the proposed scheme is more robust to the variation of the residual code phase offset and has better performance than the conventional scheme.

• The Journal of the Acoustical Society of Korea
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• v.27 no.6
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• pp.286-295
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• 2008

Underwater acoustic communication has multi path error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In this paper, we consider the use of various channel coding schemes such as RS code, convolutional code, cross-layer code and LDPC code in order to compensate the multipath effect in underwater channel. As shown in simulation results, characteristic of multipath error is similar to that of random error, so interleaver has little effect for error correcting. For correcting of error floor by multipath error, it is necessary strong channel codes like LDPC code that is similar to Shannon's limit. And the performance of concatenated codes including RS codes has better performance than using singular channel codes.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.9
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• pp.9-17
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• 1999

In this paper, we present a mathematical modeling and perform a performance analysis of double-dwell serial search algorithm, which has a search window concept, for pilot channel in DS-CDMA(Direct Sequence Code Division Multiple Access). We derive a code detection function, a false alarm function, a code miss function, and a mean code acquisition time for the performance analysis. We calculate the mean code acquisition time of the mathematical model in IS-95 forward link and compare it with that of the conventional search methods. The performance of the code acquisition system is also evaluated to investigate the effect of dwell times and search window size. The JTC channel model, which is a PCS channel model in North America, is used for the analysis. The numerical result shows that the mean code acquisition time of the double-dwell serial search algorithm with a search window is reduced by about 17%~25% than those of the conventional ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12C
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• pp.971-976
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• 2010

We introduce an error correcting 4/6 modulation codes for holographic data storage, and simulate under adding mis-alignment noise. The holographic data storage has two-dimensional intersymbol interference. To increase the channel performance, it is necessary to use modulation code. Furthermore, if the modulation code has trellis structure, error correcting capability is added. The error correcting 4/6 modulation code shows better performance than conventional modulation codes with and without mis-alignment noise.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.75-78
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• 2004

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the data rate and the reliability of communications by a channel code, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1540-1545
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• 2001

This paper is concerned with the reverse link performance of multi-code CDMA systems in multipath fading environments. The degree of orthogonality loss among multiple spreading code channels is characterized as the orthogonality factor. It depends on various system parameters including multipath power profiles of propagation channels and the number of Paths resolved at a Rake receiver. The effect of the parameters on the system performance is then investigated in terms of bit error rate and required signal quality. The results show that multipath delay power profiles dominantly affect mutual interference among multi-code channels and multipath combining gain by bandwidth expansion is not so great due to the increase of the mutual interference. Moreover, the orthogonality factor is derived as the value of between (1/m) and 1.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.492-492
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• 2009

Nowadays in Republic of Korea, there is no distinct reference for the related design technology of rotor blade of wind turbine. Therefore the optimum design and evaluation of performance is carried out with foreign commercial code softwares. This paper shows in-house code software that evaluates the aerodynamic design of wind turbine rotor blade using blade element-momentum theory (BEMT) and processes that is applied through various aerodynamics theories such as momentum theory, blade element theory, prandtl's tip loss theory and strip theory. This paper presents the results of the numerical analysis such as distribution of aerodynamic properties and performance curves using in-house code POSEIDON.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.176-179
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• 2005

In this paper, we propose the new method that separate the existing common VQ code book into two parts, one is the common VQ code book which is the half of existing common VQ code book, another is the personal speaker VQ code book which accommodate the personal speaker characteristic, variation to improve the performance of the text-dependent speaker verification system using discrete HMM. We apply the propose method m this paper to the text-dependent speaker verification system using discrete HMM and have the improvement performance of about 0.24% compared to existing method

• Journal of the Korea Society of Computer and Information
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• v.7 no.3
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• pp.128-134
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• 2002

In this paper, the performance on the PN code acquisition of DS/CDMA system was analyzed using the Nakagami-m probability density function considered fading environment. The equations on detection probability, $P_D$ and false alarm probability, $P_{FA}$, decision variables affecting the PN code acquisition time were derived and proved using simulation in order to analyze the performance. In conclusion, It was necessary increasing the gain of PLL for correcting phase errors and improving the acquisition performance of PN code in apply to the rake receiver.