• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.415-421
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• 2009

TOA(time-of-arrival) and TDOA(time-difference-of-arrival) positioning techniques are commonly used in many radio-navigation systems. From the literature, it is known that the position estimate and error covariance matrix of TDOA obtained by GN(Gauss-Newton) method is exactly the same as that of TOA when the error source of the range measurement is only an IID white Gaussian noise. In case of geo-location and indoor positioning, however, multi-path or NLOS(non-line-of-sight) error is frequently appeared in range measurements. Though its occurrence is random, the multipath acts like a bias for a stationary user if it occurs. This paper presents the comparisons of error characteristics between TOA and TDOA positioning in presence of multi-path or NLOS error. It is analytically shown that the position estimate of TDOA is exactly the same as that of TOA even when bias errors are included in range measurements with different magnitudes. By computer simulation, position estimation error and error distribution are analyzed in presence of range bias errors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.259-266
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• 2002

In the CDMA system, the Multiple access interference(MAI) causes system performance and capacity degradation. One of the MAI cancel method is a feedback detector that orthogonal decision-feedback detector(ODFD) and Deocrrelating decision-feedback detector(DDFD) have been studied by now. In this paper, we propose a blind adaptive ODFD(BA-ODFD) with blind equalizer combined ODFD, Also we simulate the operation of BA-ODFD in AWGN channel and Rayleigh (tiding channel. and compare blind adaptive ODFD with blind adaptive DDFD.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.738-745
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• 2012

This paper proposes an approximated soft decision demapping algorithm with low computational complexity for coded 4+12+16 amplitude phase shift keying (APSK) in an additive white Gaussian noise (AWGN) channel. To derive the proposed algorithm, we approximate the decision boundaries for 4+12+16 APSK symbols, and then decide the log likelihood ratio (LLR) value for each bit from the approximated decision boundaries. Although the proposed algorithm shows about 0.6~1.1dB degradation on the error performance compared with the conventional max-log algorithm, it gives a significant result in terms of the computational complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.12
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• pp.1044-1052
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• 1990

We have investigated the digital bit synchronization problem in baseband communication receiver systems using the Gauss-Markov estimation technique which is equivalent to the weighted least square method. The realized bit synchronizer, including the data detector, processes the input signal two dimensionally into the transition phase and data level under the white Gaussian noise environment. We have confrmed the realiation of the bit synchronizer via computer simulation. In addition, we have compared and evaluated the estimation error performance of the proposed method with that of the conventional DTTL method and of the minimum likelihood method.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.109.1-109.1
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• 2012

In the past few years, two-planet circumbinary systems (e.g., HW Vir, NN Ser, DP Leo and HU Aqr) have been detected around short-period eclipsing binaries using ground-based telescopes. The existence of these planets has been inferred by interpreting the O-C variations of the mid-eclipse times. We have tested the orbital stability of these systems and propose to use Light Travel Time Effect (LITE) to detect such circumbinary planets from the ground. We generated synthetically the LITE signal of a two-planet circumbinary system with the aim to apply an analytic LITE model to recover the underlying synthetic system. To mimic a degree of realism inherent to ground-based observations, we added to the synthetic LITE data white noise with a Gaussian distribution and sampled the synthetic LITE signal randomly. We successfully recovered the original system demonstrating that two-planet circumbinary systems can be detected using ground-based telescopes, provided the timing measurements of the mid-eclipses are sufficiently accurate and the observing baseline is long enough to ensure a sufficient coverage of all involved periods. We used HU Aqr as a test system and applied our model to its proposed planetary bodies considering near-circular orbits. We present the results of our calculations and discuss the LITE-detectability of a HU Aqr-like system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.797-803
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• 2002

In this paper we derive the probability density function of the phase error of the received signal over Rician fading channel and verify its propriety as the probability density function using the zeroth moment. In general, for the error probability over fading channel we compute the error probability in the first place when it is only AWGN, and then we get the final result by averaging the first result and the probability density function of the corresponding fading channel. In this paper, however, we compute the error probability by double integration after the probability density function over fading channel is computed.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.115-119
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• 2005

In this paper, we propose a method that search the sweet spot of array antenna beam, and keep it for fast speed transmission in millimeter wave on single array antenna link. We use TDD(Time Division Duplex) as transfer method, and it transfers the control data of antenna. The proposed method is the modified genetic algorithm which selects a superior initial group through slave-processing in order to resolve the local solution of genetic algorithm. The efficiency of the proposed method is verified by means of simulations with white Gaussian noise and not on single array antenna link.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.705-708
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• 2005

In this paper, we propose a method that search the sweet spot of antenna beam, and keep it for fast speed transmission in millimeter wave on point-to-point link We use TDD(Time Division Duplex) as transfer method, and it transfers the control data of antenna. The proposed method is composed of two ADALINE which used the parallel. The efficiency of the proposed method is verified by means of simulations with white Gaussian noise and not on point-to-point link.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.519-529
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• 1993

A spectral and power efficient modulation technique, named Compact Superposed Quadrature Amplitude Modulation (Compact-SQAM), is introduced. The performance of Compact-SQAM system, in a Linearly and nonlinearly amplified single and multicarrier environment, in the presence of additive white Gaussian noise(AWGN), intersymbol interference(ISI), timing jitter and adjacent channel interference (ACI), is experimentally analyzed via computer simulation. Various channel conditions, such as channel spacing, between the main and adjacent channels and fade depth on the desired main channel, are examined. Our result shows that Compact-SQAM, and better P(e) performance that other modems using simple Butteroworth type postdetection receive filters. Especially, Compact-SQAM modem achieves higher efficiency of frequency utilization and better P(e) performance than other modems in the severly bandlimited nonlinear multicarrier channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2696-2705
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• 1997

An exact experssion for the average symbol error rate(SER) of L-order selection diversity for MPSK signals in a frequency-nonselective slowy m-distributed Nakagami fading and additive white Gaussian noise(AWGN) is determs of finite sums is obtained. To derive the SER of MPSK signals with selection combining, the new expression of pdf is introduced and many other mathmatical methods are used. When fading index m is 1, the derived exppression lead to those of MPSK with selection combining in Rayleight fading channels. The results show that the error probability decreases as the order of diversity increases.