• Title/Summary/Keyword: 상관간섭

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A Study of Interference-Free Home PLC based on the Binary ZCD Code (연속직교 상관특성을 갖는 아진 코드 기반의 구내용 PLC에 관한 연구)

  • Cha, Jae-Sang;Kim, Seong-Kweon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.2
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    • pp.38-44
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    • 2006
  • In this paper, a new interference-free Home CDMA-PLC(Code Division Multiple Access-Power Line Communication) system based on the binary ZCD(Zero Correlation Duration) spreading code is proposed as a key solution to overcome the previous problems. Binary ZCD spreading code sets with enlarged family sizes are generated by carrying out a chip-shift operation of the preferred pairs. The properties or the proposed ZCD-PLC systems are effective for MPI(Multi-Path Interference) and MAI (Multiple Access Interference) cancellation in the CDMA-PLC systems. By BER performance simulation, we certified the availability of proposed ZCD-CDMA-PLC system.

A Study on Hybrid Multi-User Interference Cancellation Scheme for Multirate DS/CDMA System (Multirate DS/CDMA 시스템을 위한 하이브리드 다중사용자 간섭 제거 기법에 관한 연구)

  • 유종엽;우대호;변윤식
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.26 no.8A
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    • pp.1358-1366
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    • 2001
  • Variable Processing Variable Processing Gain 기법을 기반으로 하는 Multirate-DS/CDMA 시스템에서는 다중 사용자 간섭뿐만 아니라, 불완전한 전력제어로 인해 발생되는 현재 이동 통신 시스템에서의 원근효과와 유사한 간섭이 다른 데이터율 사용자 신호들 사이에서 발생하게 된다. 이러한 간섭은 이동통신 시스템 성능을 저하시키고, 용량을 감소시키게 되므로 이들 간섭을 효과적으로 제거할 수 있는 다중 사용자 검출 기법이 절실히 요구된다. 따라서 본 논문에서는 이러한 다중 사용자 간섭과 원근 효과를 효과적으로 제거하기 위한 하이브리드 다중 사용자 간섭 제거 기법을 제안한다. 하이브리드 다중 사용자 간섭 제거 기법은 하나 이상의 다중 사용자 검출 기법을 포함한다. 제안된 하이브리드 다중 사용자 간섭 제거 기법의 성능을 평가하기 위해 본 논문에서는 기존의 단일사용자 검출 기법 및 다중 사용자 검출 기법을 다시 한번 살펴보고, 이들 기존 검출기와 제안된 검출기를 컴퓨터 모의 실험을 통해 그 성능을 비교한다. 모의 실험에서는 AWGN 환경에서 각 SNR[dB]에 따른 BER 곡선을 조사하였다. 모의실험 결과로부터 기존의 병렬 간섭 제거 기법이나 역 상관 검출기보다 제안된 하이브리드 다중 사용자 간섭 제거 기법이 우수한 성능을 갖음을 알 수 있었다. 이는 어느 정도의 복잡도와 시간 지연에 대한 대가이다. 하지만 이 시간 지연은 검출구간을 고 데이터율 사용자 그룹에 맞춤으로써 어느 정도 해결될 것으로 보인다.

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Improved speech enhancement of multi-channel Wiener filter using adjustment of principal subspace vector (다채널 위너 필터의 주성분 부공간 벡터 보정을 통한 잡음 제거 성능 개선)

  • Kim, Gibak
    • The Journal of the Acoustical Society of Korea
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    • v.39 no.5
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    • pp.490-496
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    • 2020
  • We present a method to improve the performance of the multi-channel Wiener filter in noisy environment. To build subspace-based multi-channel Wiener filter, in the case of single target source, the target speech component can be effectively estimated in the principal subspace of speech correlation matrix. The speech correlation matrix can be estimated by subtracting noise correlation matrix from signal correlation matrix based on the assumption that the cross-correlation between speech and interfering noise is negligible compared with speech correlation. However, this assumption is not valid in the presence of strong interfering noise and significant error can be induced in the principal subspace accordingly. In this paper, we propose to adjust the principal subspace vector using speech presence probability and the steering vector for the desired speech source. The multi-channel speech presence probability is derived in the principal subspace and applied to adjust the principal subspace vector. Simulation results show that the proposed method improves the performance of multi-channel Wiener filter in noisy environment.

Adaptive Feedback Interference Cancellation Algorithm Using Correlations for Adaptive Interference Cancellation System (적응 간섭 제거 시스템을 위한 상관도를 적용한 적응적 궤환 간섭 제거 알고리즘)

  • Han, Yong-Sik;Yang, Woon-Geun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.4
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    • pp.427-432
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    • 2010
  • To reduce the outage probability and to increase the transmission capacity, the importance of repeaters in cellular systems is increasing. But a RF(Radio Frequency) repeater has a problem that the output of the transmit antenna is partially feedback to the receive antenna, which is feedback interference. In this paper, we proposed adaptive Sign-Sign LMS(Least Mean Square) algorithm using correlations for the performance enhancement of RF repeater. The weight vector is updated by using sign of input signal and error signal to the least squared error of the conventional algorithms. When compared with the conventional method, the proposed canceller achieves the maximum 10 dB performance gain in terms of the MSE(Mean Square Error).

SINR Maximizing Collaborative Beamforming with Enhanced Robustness Against Antenna Correlation (안테나 간 상관도에 강건한 SINR 최대화 협력적 빔포밍 기법)

  • Kim, Jae-Won;Sung, Won-Jin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.4
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    • pp.95-103
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    • 2009
  • In this paper, a generation method of transmit and receive beamforming vectors based on base station cooperation is proposed which maximizes the user SINR in mobile cellular multi-user MIMO systems. There are two main sources of interference which deteriorate the performance of the system, i.e. the inter-user interference caused by the usage of the same radio resource for multiple users in the system, and the inter-cluster interference from neighboring base stations which are not participating in cooperative transmission. The proposed scheme cancels out the inter-user interference by using the block diagonalization(BD) method, and mitigate the inter-cluster interference by using optimal transmit and receive beamforming vectors based on optimal combining(OC) with the statistic information of inter-cluster interference. We perform computer simulations to verify the performance of the proposed scheme, and compare the result to the conventional performance obtained from utilizing the receiver side information only or utilizing the information from neither sides. The performance evaluations are conducted not only over the independent MIMO channels, but over correlated MIMO channels to demonstrate the robustness of the proposed scheme over the channels with correlation among antennas.

A Study on Blind Adaptive Interference Suppression for DS-CDMA systems (DS-CDMA 시스템을 위한 블라인드 적응 간섭 억제에 관한 연구)

  • 우대호;윤태성;변윤식
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.10B
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    • pp.1995-2003
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    • 1999
  • Since the cross-correlation function which is due to communication channel distortion or interference is not orthogonal, near far problem and multi-user interference are generated in the DS-CDMA system. Those problems degrade performance of the system so that the efficient algorithm to suppress the interference in the DS-CDMA system is required. In this paper, a blind adaptive interference suppressor using constant modulus algorithm is proposed. Simulation results present that the gain of SIR for the blind adaptive receiver is about 7[dB] at steady state over Gaussian channel in forward channel. The gain of noise to interference ration is about 4[dB] over Rayleigh fading channel, is about 11[dB] over multipath channels. Thus the proposed receiver has higher performance than a conventional receiver in the DS-CDMA system.

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Temporal characterization of femtosecond laser pulses using spectral phase interferometry for direct electric-field reconstuction (주파수 위상 간섭계를 이용한 펨토초 레이저 펄스의 시간적 특성연구)

  • 강용훈;홍경한;남창희
    • Korean Journal of Optics and Photonics
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    • v.12 no.3
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    • pp.219-224
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    • 2001
  • Spectral phase interferometry for direct electric-field reconstruction (SPIDER) was fabricated and used to characterize pulses from a Ti:sapphire oscillator. In the SPIDER apparatus, two replicas of the input pulse were generated with a time delay of 200 fs and were upconverted by use of sum-frequency generation with a strongly chirped pulse using a 8-cm-long SFIO glass block at a 30-11m-thick type II BBO (p-BaBz04) crystal. The resulting interferogram was recorded with a UV-enhanced CCD array in the spectrometer. The spectral phase was retrieved by SPIDER algorithm in combination with independently measured pulse spectrum and the corresponding temporal intensity profile was reconstructed with a duration of 19 fs. As an independent cross-check of the accuracy of the method, we compared the interferometric autocorrelation (lAC) signal calculated from the SPIDER data with a separately measured lAC. The conventional, but unjustified, method of fitting a sechz pulse to the autocorrelation deceivingly yielded a pulse duration of 15 fs. This systematic underestimation of the pulse duration affirms the need for a complete characterization method. From the consideration in this paper, we concluded that the SPIDER could provide an accurate characterization of femtosecond pulses. ulses.

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Adaptive Feedback Interference Cancellation Using Correlations for WCDMA Wireless Repeaters (WCDMA용 무선중계기에서 상관도를 이용한 적응적 궤환 간섭 제거)

  • Moon, Woo-Sik;Im, Sung-Bin;Kim, Chong-Hoon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.7 s.361
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    • pp.35-40
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    • 2007
  • As the mobile communication service is widely used and the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we propose a new varable step-size LMS algorithm which utilizes correlation between reference and error signals to adjust the step sizes, for cancelling the feedback interference signals in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm was evaluated through computer simualation by being applied to the feedback canceling filter of the WCDMA repeater. The simulation results demonstrated that the proposed one is superior to the conventional ones in terms of the cancelation perormance.

An Adaptive Hybrid Multi-User Detection Using Amplitude Estimation with Array Antennas (어레이 안테나를 이용한 적응 혼합형 다중 간섭 제거기)

  • 이규만;한동석
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.83-86
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    • 2000
  • DS/CDMA 이동통신 환경에서 채널의 용량을 제한하는 가장 큰 요인은 다중 사용자 간섭 신호의 영향이다. 본 논문에서는 어레이 안테나와 적응 혼합 다중 사용자 검파기 구조 (MUD: Multi-User Detection)를 이용하여 이러한 문제를 제거한다. 어레이 안테나의 각각의 빔 형성기는 MUD에서 궤환되는 기준 신호를 이용하여 원하는 사용자의 방향으로 빔을 형성하고 간섭 신호 방향으로는 널을 형성하여 제거하게 된다. 수신 신호의 전력이 제어되지 못하여 원근 문제(near-far problem)가 발생할 경우, 제안한 MUD는 적응적으로 지배적인 상관 값에 대해서는 직렬형, 비슷한 크기의 신호들은 병렬형 간섭 제거기를 통하여 제거함으로써 기존의 고정형 간섭 제거기보다 우수한 성능을 나타내었다.

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Receive Diversity for OFDM Systems with Cochannel Interference (동일 채널 간섭을 고려한 OFDM 시스템의 수신 다이버시티 기법)

  • Seo, Bo-Seok
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2005.11a
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    • pp.95-98
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    • 2005
  • 이 논문에서는 동일채널 간섭이 존재하는 채널 환경에서 OFDM(Orthogonal Frequency Division Multiplexing) 시스템의 수신 다이버시티 결합 방법을 제시한다. 제시된 방법에서는 각 수신 안테나로부터의 수신 신호를 주파수 영역에서 부반송파 단위로 결합하며, 잡음과 간섭 전력을 고려한 MRC(Maximum Ratio Combining)를 적용한다. 잡음과 간섭 전력은 채널의 제한된 지연확산에 기인하는 주파수 대역에서의 상관특성(coherency)을 이용하여 인접한 몇 개의 부채널에 대해 잡음과 간섭 전력의 평균을 취함으로써 더 정확한 추정치를 얻는다. IEEE 802.11a 무선 LAN 규격에서 모의실험 결과 제안방법은 기존 방시에 비해 SNR을 2-4 dB 개선하였으며, 정확하게 SINR을 추정한 경우에 대해 1 dB 이내로 접근하는 결과를 나타내었다.

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