• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.536-539
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• 2002

The use of concatenated codes in noncoherent synchronous optical fiber CDMA networks is proposed. The concatenated code sequences are generated using balanced Walsh code sequences and Walsh code sequences. The selection of balanced Walsh code sequences is presented and the design of fully programmable transmitter and receiver is reported. The analysis of the system BER performance shows that multiple-access interference is completely eliminated and the BER performance of the proposed system is better than that of the non-coherent synchronous optical fiber CDMA system using optical orthogonal codes with double hard-limiters.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.821-824
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• 1999

In this article, as a way of pursuing high spectral efficiency and flexible cell planning, co-channel dual-polarization techniques are suggested for B-WLL applications. It provides a double down stream capacity compared with conventional scheme and also makes some flexibility in cell planning. In order to implement co-channel B-WLL system, some frequency plans, interference cancellation methods, and system block diagrams are presented here.

• Journal of the Optical Society of Korea
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• v.6 no.2
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• pp.33-36
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• 2002

We propose a modulation scheme of optical absorption in a coupled asymmetric quantum well (QW) structure via electrically controllable quantum interference. It is based on the parallel-perpendicular energy coupling effect. We show that by applying an external electric Held in the parallel direction (to the QW layers), we can obtain a maximum (peak-type) absorption at a specific wavelength where absorption cancellation would occur due to electrically induced transparency without such an external Held .

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.769-778
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• 2017

In this paper, a self-interference signal cancellation(SIC) circult for In-band Full-Duplex has been developed and tested in RF/analog region. By use of this SIC circuit, a FM two-way radio has been developed working at FRS(Family Radio Service) band. The two-way radio device is transmitting the FM modulated signal and demodulating the wanted FM signal at the same time. A circulator is used to enable a single antenna to transmit and receive simuultaenously. The receiver circuit needs to cancel out the self-interference signal due to the transmit signal. A vector modulator(VM) is used to control the phase and magnitude of the esitmated signal. And in-phase and quadrature correlators are used to figure out the optimal coefficients of the VM to remove the self-interference signal according to the change of channel environment. In this work, SA58646 has been used as the FM transceiver, and the system is tested with a frequency of 465 MHz and a bandwidth of 12.5 kHz FM signal. The output power is 17.2 dBm at the antenna port, and the self intererence signal level is measured -49.2 dBm at the receiver end. Therefore the SIC level is measured by 66.4 dB.

• Progress in Superconductivity
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• v.5 no.1
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• pp.26-30
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• 2003

Magneto-cardiogram(MCG) signals may be highly distorted by the environmental noise, such as power-line interference, broadband white noise, surrounding magnetic noise, and baseline wondering. Several kinds of digital filters and noise cancellation methods have been designed and realized by many researchers, but these methods gave some problems that the original signal may be distorted by digital filter due to the wideband characteristics of background noise. To eliminate noise effectively without distortion of MCG signals, we performed multi-level frequency decomposition using wavelet packets and local adaptive noise cancellation in each local frequency range. In addition to the proposed wavelet filter to eliminate these various non-stationary noise elements, the local adaptive filter using the least mean square(LMS) algorithm and the soft threshold do-noising method are introduced in this paper. The signal to noise ratio(SNR) and the reconstruction square error(RSE) are calculated to evaluate the performance of the proposed method and compared with the results of the conventional wavelet filter and adaptive filter. The experimental results show that the proposed local adaptive filtering method is better than the conventional methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.155-163
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• 2009

OFDM System is a promising transmission technique due to its spectral efficiency But, a major disadvantage of the OFDM system is its sensitivity to frequency offset and phase noise that makes intercarrier interference (ICI), which degrades the system performance severely The ICI self-cancellation method has a good performance with frequency offset or phase noise. This paper proposed the N/2 spacing data-conjugate method that works well in large frequency offset and phase noise (normalized frequency offset=0.2-0.4, phase noise standard deviation=about lodes). Also, an efficiency ICI cancellation method using pilot was proposed. Simulation results confirm that performance of the proposed scheme is better than conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8C
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• pp.771-778
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• 2003

A mobile station in a cell receives interference signals from neighboring base stations. Due to the interference signals, the forward link capacity of the cellular system is reduced. Pilot signal received from a neighboring base station is one of the interference signals. Since the pilot signal is a known signal for all the mobile stations, the pilot interference signal can be cancelled by interference cancellation techniques. In this paper, we propose a demodulator with interference canceller to cancel pilot interference signals received from neighboring base stations. The simulation results show that Eb/No value to obtain BER = 10-2 is lowered by 3㏈ in the propose demodulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1038-1044
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• 2010

Interference may severely deteriorate performance in wireless communication. Han-Kobayashi scheme splits each user's signal into private and common information so that the receiver removes the other's common signal for partial interference cancellation. This paper proposes an optimal power allocation to private and common signals for Han-Kobayashi scheme by using required SNR in a private information only system. Numerical results show that the proposed power allocation is quite close to the optimal power allocation based on exhaustive searches.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.354-356
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• 2001

The demand of the power and gas energy have been rapidly increasing with the industralization, therefore, the area where buried pipelines run parallel with the adjacent power lines and cross them increases in Seoul as well as other cities. These situation cause AC interference from the power lines. However, there aren't any standards to preserve the pipelines from AC interference in Korea. We just use other country's criteria directly. Other developed countries have used the various AC interference mitigation methods such as lumped grounding. cancellation wires and gradient control wires etc.. This paper introduces the steel plate method which is using for AC interference mitigation method in Korea and investigates the effects of mitigation methods through case study by computer simulation.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.149-152
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• 2002

In this paper, an adaptive interference canceller (AIC) Is applied to the space-time coded DS-CDMA system in fading channels with arrival time difference from multiple transmit antennas In a CDMA system, arrival time difference causes not only inter-antenna and Inter-symbol interference but also multiple-access Interference even in a downlink. To mitigate the effect of the Interferences an AIC and ML decoding joint scheme Is proposed fur a space-time coded DS-CDMA system in which an adaptation process of tile AIC is merged in the Viterbi decoding algorithm. The performance of the proposed receiver is evaluated for the system with two transmit antennas. It is shown that the proposed receiver achieves significant performance improvement over the ML decoding receiver without the AIC