• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.418-424
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• 2007

This paper proposes a scheme to track channel response in OFDM systems with null sub-carriers. The proposed channel tracking scheme estimates the channel response first in the frequency domain by using the decision directed data. The time domain channel estimation is then performed to remove additive white Gaussian noise (AWGN) components further. Due to the channel estimation in the frequency domain, no inverse matrix calculation is required in the time domain channel estimation. Computational reduction in the proposed method is about 93%, compared with the conventional time domain channel estimation method. Mean square error (MSE) and bit error rate (BER) performances are evaluated by using computer simulation. The proposed method shows the same performance as that of the conventional time domain channel estimation even though the significant computational reduction.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1689-1699
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• 2006

A nonlinear channel blind equalizer by using a hybrid genetic algorithm, which merges a genetic algorithm with simulated annealing, and a RBF network is presented. In this study, a hybrid genetic algorithm is used to estimate the output states of a nonlinear channel, based on the Bayesian likelihood fitness function, instead of the channel parameters. From these estimated output states, the desired channel states of the nonlinear channel are derived and placed at the center of a RBF equalizer to reconstruct transmitted symbols. In the simulations, binary signals are generated at random with Gaussian noise. The performance of the proposed method is compared with those of a conventional genetic algorithm(GA) and a simplex GA, and the relatively high accuracy and fast convergence of the method are achieved.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.332-339
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• 1995

In this paper, it was investigated the guided field intensity distribution of the channel in the silver & potassium ion-exchange glass-waveguide. The guided field intensity distribution analysis of ion-exchange glass-waveguide was based on the combination of the WKB dispersion relationship method with a Gaussian distribution function of refractive index profile and the Field Shadow method to the modeling of the channel waveguide. As the results of the channel waveguide modeling, it was represented 2-dimensional and 3-dimensional field distribution of ion-exchange glass waveguide.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.466-472
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• 2007

Single carrier block transmission with frequency domain equalization(SC-FDE) has been shown to be a promising candidate in ultra-wideband(UWB) communications. In this paper, we analyze the performance of SC-FDE over UWB communications with channel estimation error. The probability density functions of the frequency domain minimum mean-squared error(MMSE) equalizer taps are derived in closed form. The error probabilities of single carrier block transmission with frequency domain MMSE equalization under imperfect channel estimation are presented and evaluated numerically. Compared with the simulation results, our semi-analytical analysis yields fairly accurate bit error rate performance, thus validating the use of the Gaussian approximation method in the performance analysis of the SC-FDE system with channel estimation error.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.2
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• pp.116-123
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• 2005

Chirp spread spectrum method using both time and frequency component is fit to time varying channel such as powerline channel. The used chirp symbol based on the CEBus standard is the unit symbol which sweeps from 100kHz to 380kHz over a 25㎲. To evaluate the performance of between Chirp-SS and DSSS, we measured the bit error rate under Gaussian channel. Simulation result is shown that Chirp-SS has a about 3[dB] gain of SNR than DSSS. To verify the performance of implemented modem, it is made up the powerline channel environment. After adding several noises to it, we examined the receiving status of modem. The implemented modem is able to receive the signal over the powerline channel with having several noises and capacitive loads.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.69-72
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• 2000

In CDMA systems, the performance of the typical multipath searcher degrades much according as the signal to noise ratio becomes low. In this paper, multipath searcher algorithm is proposed based on sliding window to overcome this drawback. In searcher systems, correlation values between incoming and local PN sequences are used to acquire multipath components. Therefore more accurate distributions of correlation values obtained through this proposed algorithm enables to get higher detection probability. In computer simulations, it is verified that proposed algorithm has better performances in Rayleigh fading channel and Gaussian channel.

• ETRI Journal
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• v.31 no.3
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• pp.345-347
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• 2009

This letter presents an alternative analytical expression for computing the probability of an M-ary phase shift keying (MPSK) wedge-shaped region in an additive white Gaussian noise channel. The expression is represented by the cumulative distribution function of known noncentral F-distribution. Computer simulation results demonstrate the validity of our analytical expression for the exact computation of the symbol error probability of an MPSK system with phase error.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.16-19
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• 2000

We propose a deterministic vector channel simulation model satisfying not only rigorous temporal correlation but also arbitrary spatial correlation using the method of Doppler phase difference sampling. The model is more efficient than the conventional PN filtered Gaussian model with coloring process in evaluating the laboratory performance of mobile communication systems employing adaptive way antennas or space diversity.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.11-20
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• 1993

In this paper, the asymtotic performance of a multiple trellis coded differential MPSK modulation over a satellite land mobile communication channel characterized by additive white Gaussian noise (AWGN) and fading is presented. Simple formulas for the bit error probability are derived for systems using differential MTCM over Rician and Rayleigh fading channel. Also are given numerical results which are more indicative of the actual system performance. Finally, the comparisons with results previously obtained for the uncoded and conventional trellis coded modulation are provided.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.25-28
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• 2000

시변 특성을 갖는 무선 채널 환경에서 UEP(Unequal Error Protection) 채널 부호화 방법은 효율적인 정보 전송을 가능케 한다. 본 논문에서는 IP-SCCC (Interleaved Puncturing Serially Concatenated Convolutional Codes)로 CSI(Channel State Information)와 SSI(Source Significance Information)를 이용한 두가지 UEP 채널 부호화 방법을 제안한다. 또한 AWGN(Additive White Gaussian Noise)과 Rayleigh 페이딩이 존재하는 채널을 가정하고 모의 실험을 통해 알고리즘의 우수성을 검증한다.