• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.753-756
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• 2001

Automatic Identification System(ALS) employed SOTDMA for the multiple access method. In SOTDMA systems, slot reuse may result in discrimination or garbling. Especially Gaussian Minimum Shift Keying(GMSK) Co-Channel Interference(CCI) resulted from the slot reuse in the Aloha zone degrades the system performance such as capacity In this paper we introduce some useful techniques to cancel the CCI and discuss the methodology which is applicable to AIS-SOTDMA

• Journal of Satellite, Information and Communications
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• v.10 no.4
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• pp.101-106
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• 2015

In this paper, a shared band transmission, in which downlink signals from satellite to both earth station and user terminal are transmitted in the same frequency band, is considered. For proper operation of such shared band transmission, self-interference caused by the transmitted signal from its own transmitter should be cancelled and the desired signal from the other transmitter should be obtained. The self-interference is sent by its own transmitter and it can be easily regenerated with the estimated round-trip delay. In addition to this delay, non-linearity effects caused by power amplifiers at the earth station and satellite should be exploited. The proposed interference canceller divided into two parts: one is subtraction of the transmitted signal with delay and non-linearity effects, and the other is adoptive filter to suppressed the residual interference. Through computer simulations, the effectiveness of the proposed system is verified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.91-99
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• 2011

Several repeater systems are used to enhance the cell coverage to location such as shadow and rural areas in mobile systems. But the general RF repeater solutions are not suitable for high power outdoor environment because it has the weakness such as self oscillation problem With adoption of a adaptive digital filter technology, feedback interference cancellation repeater prevents oscillation by detecting and canceling the unwanted feedback signal between transmission and receiver antenna. In this paper, dual NLMS based interference cancellation method is proposed and the step size adaptation can be implemented by the estimation of the feedback channel Doppler frequency characteristics. The performance of the proposed algorithm is quantified via analysis and simulation for the static and multipath fading feedback channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.331-337
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• 2016

In this paper, we analyze performances of in-band full-duplex communication system and self-interference (SI) suppression methods in environment where there exists the SI signal. The SI has to be removed to achieve required error rate performance of the system in order - propagation domain, analog domain and digital domain. In propagation domain, the SI signal is attenuated by separating transmitted and received beams physically. In analog and digital domain, after reconstruction of the SI signal using channel estimates and transmit signal, the SI signal can be cancelled from the desired signal. In this paper, assuming that the SI signal can be sufficiently reduced in propagation domain, we demonstrate that the in-band full-duplex communication system can achieve the target error rate by suppressing the SI signal in order - analog and digital domain, based on channel estimates that can be obtained by the method of Least squares.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.638-647
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• 2006

Recently, the DFT-Spread OFDM has been studied for the PAPR reduction. However, the DFT-Spread OFDM produces more ICI and SCI problems than OFDM because phase offset mismatch of the DFT spreading code results from the random phase noise in the oscillator. In this paper, at first, phase noise influence on the DFT-Spread OFDM system is theoretically analyzed in terms of the BER performance. Then, the conventional ICI self-cancellation methods are discussed and two kinds of ICI self-cancellation methods are newly proposed. Lastly, a new DFT-Spread OFDM system which selectively adopts the ICI self-cancellation technique is proposed to resolve the interference problem and PAPR reduction simultaneously. Proposednew DFT-Spread OFDM system can minimize performance degradation caused by phase noise, and still maintain the low PAPR property. Among the studied methods, DFT-Spread OFDM with data-conjugate method or newly proposed symmetric data-conjugate method show the significant performance improvements, compared with the DFT-Spread OFDM without ICI self-cancellation schemes. The data-conjugate method is slightly better than symmetric data-conjugate method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1258-1268
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• 2014

In this paper, we propose and design IBFD system based on DCR. And then, we analyze effect of DC offset by self-interference in the proposed system. Also, we evaluate BER performance of the proposed system according to DC offset. As a result of the simulation, we can confirm that when the self-interference is not completely cancelled by the RF cancellation, linearity of desired signal and self-interference is distorted by DC offset. Also, in the proposed system using m-QAM modulation, DC offsets of multi-level are caused by self-interference with m-QAM modulation. As a result, constellations of desired signal and self-interference are greatly distorted. In contrast, in the proposed system using m-PSK modulation, DC offset of single level is caused by self-interference with m-PSK modulation. In this condition, we confirm that distortion of constellations of desired signal and self-interference is less than when using m-QAM modulation. That is, we can confirm that m-PSK modulation is effective than m-QAM modulation in DCR based IBFD system. Also, we can confirm that it is important to cancel self-interference as much as possible in RF-stage.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.61-62
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• 2019

최근 자원 효율성을 증대하기 위하여 차세대 유무선 통신시스템에서 동일대역 전이중 방식(In-band full-duplex, FDX)을 채택하고 있다. 하지만 전이중 방식은 송수신이 동시에 이루어지기 때문에 하향신호와 상향신호가 더해져 수신된다. 따라서 원하는 신호를 수신하기 위해 자기간섭(SI: self-interference)으로 존재하는 하향 신호를 제거하는 기술이 요구된다. 본 논문에서는 DOCSIS 3.1 기반 케이블 방송시스템에서 2차 구조의 자기간섭신호 제거(SIC: SI cancellation)기술을 제안하고 실시간 성능을 분석한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1150-1155
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• 2007

Orthogonal Frequency Division Multiplexing (OFDM) is an emerging multi-carrier modulation scheme, which has been adopted for several wireless standards such as IEEE 802.11a and HiperLAN2. A well-known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces inter-carrier interference (ICI) in the OFDM symbol. This paper investigates three methods for combating the effects of ICI: ICI self-cancellation (SC), maximum likelihood (ML) estimation, and extended Kalman filter (EKF) method. These three methods are compared in terms of bit error rate performance.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.11a
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• pp.101-103
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• 2018

최근 자원 효율성을 증대하기 위하여 차세대 유무선 통신시스템에서 동일대역 전이중 방식(in band full-duplex, FDX)을 채택하고 있다. 하지만 전이중 방식은 송수신이 동시에 이루어지기 때문에 하향신호와 상향신호가 더해져 수신된다. 따라서 원하는 신호를 수신하기 위해 자기간섭(SI: self-interference)으로 존재하는 하향 신호를 제거하는 기술이 요구된다. 본 논문에서는 주파수영역에서 자기간섭신호 제거(SIC: SI cancellation)하는 방법에 대해서 제안하고 실제 RF를 통과한 신호에 적용하여 성능을 분석한다.

• Journal of Communications and Networks
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• v.9 no.1
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• pp.50-55
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• 2007

We propose to apply chip interleaving and iterative detection to self-encoded multiple access (SEMA) communications. In SEMA, the spreading code is obtained from user bit information itself without using a pseudo noise code generator. The proposed scheme exploits the inherent diversity in self encoded spread spectrum signals. Chip interleaving not only increases the diversity gain, but also enhances the performance of iterative detection. We employ user-mask and interference cancellation to decouple self-encoded multiuser signals. This paper describes the proposed scheme and analyzes its performance. The analytical and simulation results show that the proposed system can achieve a 3 dB power gain and possess a diversity gain that can yield a significant performance improvement in both Rayleigh and multipath fading channels.