• Title/Summary/Keyword: Feedback Interference Cancellation

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WCDMA Interference Cancellation Wireless Repeater Using Variable Stepsize Complex Sign-Sign LMS Algorithm (가변 스텝 Complex Sign-Sign LMS 적응 알고리즘을 사용한 WCDMA 간섭제거 중계기)

  • Hong, Seung-Mo;Kim, Chong-Hoon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.9
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    • pp.37-43
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    • 2010
  • An Interference Cancellation Wireless Repeater transmitts directly amplified the RF signal input to extend the coverage of the base station. Such a repeater inevitably suffers from the feedback interferences due to the environment and the adaptive Interference Cancelling System(ICS) is necessary. In this paper, the Variable Stepsize Complex Sign -Sign(VSCSS) LMS algorithm for ICS is presented. The algorithm can be implemented without multiplication/division arithmetic operation so that the required logic resources can be dramatically reduced in FPGA implementation. The performance of the proposed algorithm was analyzed in comparison with CSS-LMS algorithm and the learning curves obtained from simulation showed an excellent agreement with the theorical prediction. The simulation result with ICS in fading feedback channel environment showed the performance of the proposed algorithm is competible with NLMS algorithm.

ICS RF Repeater for Marine NB-IoT Service (해상 NB-IoT 서비스를 위한 ICS RF 중계기)

  • Cho, Sin-ho;Lee, Seong-Real
    • Journal of Advanced Navigation Technology
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    • v.25 no.5
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    • pp.390-396
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    • 2021
  • In this research, design and fabrication of marine repeater capable to extend communication coverage in monitoring system of fishing gear automatic identification, which is one of implementation method of the real-name electric fishing gear system declared by Ministry of Oceans and Fisheries in 2016, is reported. The proposed marine repeater is fabricated in a form of RF repeater with interference cancellation system (ICS), which can cancel the oscillation due to feedback signal between service antenna and link antenna. In design process, we secure the isolation of 30 dB between service antenna and link antenna. It is confirmed that when the level of feedback signal into repeater input be lower of 15 dB than repeater gain, error vector magnitude due to oscillation can be lower than the performance criterion of 6%, from the test verification. It is expected that the service coverage will be extended by applying the developed marine ICS RF repeater into marine IoT network including monitoring system of fishing gear automatic identification.

Feedback Interference Cancellation for W-CDMA Repeaters Using the Adaptive Algorithms (W-CDMA용 무선중계기에서의 적응알고리즘을 이용한 궤환 간섭 잡음 제거)

  • Moon, Woo-Sik;Kim, Sun-Ho;Im, Sung-Bin;Cho, Jun-Kyung
    • Proceedings of the IEEK Conference
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    • 2007.07a
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    • pp.183-184
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    • 2007
  • As the mobile communication service is widely used, the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But wireless repeaters 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 investigate the performance of adaptive variable step-size NLMS-based algorithms for cancelling the interference signals in the W-CDMA system under time-varying multipath channels. The criteria for comparison are tracking capability, convergence speed, and complexity.

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Performance Analysis of Various Hybrid DS/CDMA Multiuser Detection Algorithms in Rayleigh Fading Channels (Rayleigh 페이딩 채널에서 하이브리드 DS/CDMA 다중사용자 검파 알고리즘의 성능분석)

  • 강환민;조성호
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.26 no.7B
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    • pp.944-950
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    • 2001
  • 현재 상용화된 CDMA (code division multiple access) 방식은 사용자가 증가함에 따라 다중 사용자 간섭에 의해 통화품질 향상 및 가입자 수용 용량 증대에 한계를 가지고 있다. 이러한 문제를 극복하기 위해 다양한 형태의 다중 사용자 검파 알고리즘이 제안되었다. 본 논문에서는 여러 형태의 알고리즘들 가운데, 역상관 (decorrelating) 검파기와 병렬 간섭 제거 (parallel interference cancellation, PIC) 검파기, 연속 간섭 제거 (successive interference cancellation, SIC) 검파기와 PIC 검파기, zero-forcing decision-feedback (ZF-DF) 검파기와 PIC 검파기를 하이브리드 형태로 구성하는 방법을 제시하였고, Rayleigh 페이딩 환경에서 성능분석 및 컴퓨터 시뮬레이션을 통한 성능 비교를 하였다. 컴퓨터 모의실험 결과, 본 논문에서 제안한 세 가지 하이브리드 검파기 모두 기존 검파기에 비하여 우수한 성능을 보였다.

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Adaptive Techniques for Joint Optimization of XTC and DFE Loop Gain in High-Speed I/O

  • Oh, Taehyoun;Harjani, Ramesh
    • ETRI Journal
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    • v.37 no.5
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    • pp.906-916
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    • 2015
  • High-speed I/O channels require adaptive techniques to optimize the settings for filter tap weights at decision feedback equalization (DFE) read channels to compensate for channel inter-symbol interference (ISI) and crosstalk from multiple adjacent channels. Both ISI and crosstalk tend to vary with channel length, process, and temperature variations. Individually optimizing parameters such as those just mentioned leads to suboptimal solutions. We propose a joint optimization technique for crosstalk cancellation (XTC) at DFE to compensate for both ISI and XTC in high-speed I/O channels. The technique is used to compensate for between 15.7 dB and 19.7 dB of channel loss combined with a variety of crosstalk strengths from $60mV_{p-p}$ to $180mV_{p-p}$ adaptively, where the transmit non-return-to-zero signal amplitude is a constant $500mV_{p-p}$.

A Study on the Narrow-band Interference Rejection in DS Spread-spectrum Systems (DS 스펙트럼 확산 시스템의 협대역 간섭 제거에 관한 연구)

  • 라상동
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.12
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    • pp.1994-2000
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    • 1993
  • A new lattice structure using decision feedback and augmented prediction for estimating and suppressing the narrowband interference is presented. The performance of the proposed interference canceller is compared to the conventional interference cancellation filter. The reference signal of the interference canceller is formed by using the chip decisions, which is correlated with the narrowband interference components of the received signal. The decision feedback technique reduce the distortion of the desired signal which is introduced by the interference canceller through the use of feedback chip decisions. And by linear prediction of the error signal, the residual interference component of can be eliminated, Using this unconteminated error signal to update the adaptive filter coefficients, the performance of the rejection can be improved. In the simulation, it is assumed that the processing gains are 7 and 15, signal to interference ratio is -10[dB], and 5% interference band. The results show that the BER performance of the proposed filter structure is improved by 1~3dB.

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Decision Feedback Equalizer Algorithms based on Error Entropy Criterion (오차 엔트로피 기준에 근거한 결정 궤환 등화 알고리듬)

  • Kim, Nam-Yong
    • Journal of Internet Computing and Services
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    • v.12 no.4
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    • pp.27-33
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    • 2011
  • For compensation of channel distortion from multipath fading and impulsive noise, a decision feedback equalizer (DFE) algorithm based on minimization of Error entropy (MEE) is proposed. The MEE criterion has not been studied for DFE structures and impulsive noise environments either. By minimizing the error entropy with respect to equalizer weight based on decision feedback structures, the proposed decision feedback algorithm has shown to have superior capability of residual intersymbol interference cancellation in simulation environments with severe multipath and impulsive noise.

Transmit Antenna Selection for Spatial Multiplexing with Per Antenna Rate Control and Successive Interference Cancellation (순차적인 간섭제거를 사용하는 공간 다중화 전송 MIMO 시스템의 전송 안테나 선택 방법에 관한 연구)

  • Mun Cheol;Jung Chang-Kyoo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.6C
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    • pp.560-569
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    • 2005
  • This paper proposes an algorithm for transmit antenna selection in a multi-input multi-output(MIMO) spatial multiplexing system with per antenna rate control(PARC) and an ordered successive interference cancellation (OSIC) receiver. The active antenna subset is determined at the receiver and conveyed to the transmitter using feedback information on transmission rate per antenna. We propose a serial decision procedure consisting of a successive process that tests whether antenna selection gain exists when the antenna with the lowest pre-processing signal to interference and noise ratio(SINR) is discarded at each stage. Furthermore, we show that 'reverse detection ordering', whereby the signal with the lowest SINR is decoded at each stage of successive decoding, widens the disparities among fractions of the whole capacity allocated to each individual antenna and thus maximizes a gain of antenna selection. Numerical results show that the proposed reverse detection ordering based serial antenna selection approaches the closed-loop MIMO capacity and that it induces a negligible capacity loss compared with the heuristic selection strategy even with considerably reduced complexity.

Robust Decision Feedback Equalizer for OFDM System under Severe ISI Channel

  • Su, Xin;Hui, Bing;Chang, KyungHi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.6
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    • pp.1914-1925
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    • 2014
  • Inter-symbol interference (ISI) problem is inevitable when the guard interval (GI) is shorter than the delay spread (DS) for an orthogonal frequency division multiplexing (OFDM) system. Iterative techniques have been proposed to overcome such a problem. However, most of existing algorithms are not efficient for an OFDM system with a small GI working under the channel with a large DS. Especially in the case of the DS spans a longer time than the half of the OFDM symbol duration. On the other hand, conventional algorithms, which can reduce the effects of the severe ISI, often employ several impractical assumptions to support the conclusions. In this paper, we present a robust decision feedback equalizer (DFE) for the OFDM system to overcome the severe ISI problem. The proposed DFE removes the ISI in a same manner as the residual inter-symbol interference cancellation (RISIC) algorithm. However, the inter-carrier interference (ICI) is reduced via cyclicity removal instead of the cyclicity restoration used in the conventional algorithms. The link-level simulation (LLS) results indicate that our proposed DFE scheme can dramatically improve the BER performance when the DS spans longer than the half of ODFM symbol duration.

Performance Improvement of Adaptive Interference Cancellation Repeater based on Image Rejection (적응형 간섭제거 중계기에서의 이미지 제거를 통한 성능 개선)

  • Kim, Won-Taek;Kwon, Jong-Hwa;Park, Kyoung-Ho;Kim, Joo-Wan;Ha, Sung-Hee;Van, Ji-Hun;Lee, Jong-Hyun
    • Proceedings of the IEEK Conference
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    • 2007.07a
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    • pp.117-118
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    • 2007
  • The received signal of ICS repeater is composed of BS(Base Station) and feedback signals. In this case, if the feedback signal is not rejected, system is oscillated. we use the IF signal for rejecting the feedback signal at ICS system. In general, SAW filter is used to reject the image of If signal. the use of this filter generates the system delay problems. In this paper, instead of SAW filter we use the Hilbert transform for rejecting image signal.

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