• Title/Summary/Keyword: Decision feedback

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Decision Feedback Demodulation-based Adaptive Equalizers for DDPSK Systems (DDPSK 시스템을 위한 결정궤환복조에 근거한 적응등화기)

  • 장동운
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.6B
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    • pp.625-637
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    • 2002
  • This study extends the modified linear feedback equalizer (MLFE), normally used for differentially coherent DPSK systems, to the equalization of double differentially coherent PSK (DDPSK) signals. By feeding back into the feedback part after modifying the equalizer output using decision feedback-based demodulation, the proposed equalizer can operate like an equalizer with a decision feedback structure. Simulation results showthat performances of the decision feedback demodulation-based feedback equalizer (DFD-FE) approach those of the DFE/coherent.

Compelex fuzzy adaptive decision feedback equalizer using RLS algorithm (RLS알고리듬을 이용한 복소 퍼지 판정궤환 적응 등화기)

  • 이상연;김재범;김기용;이충웅
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.6
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    • pp.1447-1452
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    • 1996
  • In this papre, a complex fuzzy adaptive decision feedback equalizer using the RLS algorithm is proposed. The proposed equalizer is based on the complex fuzzy adaptive equalizer. The 'IF'-part of the complex fuzzy adaptive decision feedback equalizer has membership functions which are characterized by the sate of decision feedback. The role of decision feedback is to reduce the computational complexity. Computer simulation shows that the proposed equalizer not only reduces the computational complexity but also improves the performance compared with the conventional complex fuzzy adaptive equalizers under the assumption of perfect knowledge of the linear and nonlinear channels. The effects of error propagation due to wrong decision feedback is also shown.

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Adaptive Decision Feedback Equalizer using the hierarchical Feedback filter and Soft decision device (계층적 궤환 필터 구조와 연판정 장치를 갖는 적응형 결정 궤환 등화기)

  • Lim, Dong-Guk;Song, Jeong-Ig;Kim, Jae-Mong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.1
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    • pp.138-145
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    • 2007
  • Wireless transmission system using the multipath channel is affected ISI due to the delay spread. So we use a decision feedback equalizer which consist of decision part and feedback filter for remove the ISI effectively. In this paper, we propose a improved adaptive decision feedback equalizer to mitigate ISI effectively. The proposed adaptive decision feedback equalizer is construct by using soft decision device and hierarchical feedback filter based on MMSE sub-optimal equalizer using the LMS algorithm. Soft decision device mitigate the error propagation in feedback filter by incorrectly detected decision symbol and feedback filter which is divided two step independently mitigate the ISI by using a adaptive algorithm. As a result this structure shows better performance than conventional decision feedback equalizer by mitigating the error propagation in filter cause incorrectly detecting symbol. and we get the MSE more rapidly by using larger step-size due to reduce the number of feedback filter tap. In computer simulation, we compare the bit error rate performance of proposed decision feedback equalizer with conventional one on the S-V channel model for UWB system.

Complex LMS Fuzzy Adaptive Equalizer with Decision Feedback (판정궤환이 있는 복소 LMS 퍼지 적응 등화기)

  • 이상연;김재범;이기용;이충웅
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.10
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    • pp.2579-2585
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    • 1996
  • In this paper, a complex fuzzy adaptive decision feedback equalizer(CFADFE) based on the LMS algorithm is proposed. The propoed equalizer is based on the complex fuzzy adaptive equalizer. The CFADFE isconstructed from a set of changeable complex fuzzy IF-THEN rules, where the 'IF' part of the rule is characterized by the state from a set of changealble complex fuzzy IF-THEN rules, where the 'IF' part of the rule is characterized by the state of the desision feedback. the role of decision feedback is to reduce the computational complexity. Computer simulation of the decision feedback. The role of decision feedback is to reduce the computational complexity. Computer simulation shosw that the CFADFE notonly reduces the computational complexity but also improves the performance compared with the conventional complex fuzzy adaptive equalizers. We also show that the adaptation speed is greatly improved by incorporating some linguistic information about the channel into the equalzer. It is applied to M-ary QAM digital communication system with linear and nonlinear complex channel characteristics.

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Multiple-Training LMS based Decision Feedback Equalizer with Soft Decision Feedback (연판정 귀환을 갖는 다중 훈련 LMS 기반의 결정 재입력 등화기)

  • Choi Yun-Seok;Park Hyung-Kun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.9 no.3
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    • pp.473-479
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    • 2005
  • A key issue toward mobile multimedia communications is to create technologies for broadband signal transmission that ran support high quality services. Such a broadband mobile communications system should be able to overcome severe distortion caused by time-varying multi-path fading channel, while providing high spectral efficiency and low power consumption. For these reasons, an adaptive suboptimum decision feedback equalize. (DFE) for the single-carrier short-burst transmissions system is considered as one of the feasible solutions. For the performance improvement of the system with the short-burst format including the short training sequence, in this paper, the multiple-training least mean square (MTLMS) based DFE scheme with soft decision feedback is proposed and its performance is investigated in mobile wireless channels throughout computer simulation.

Soft Decision Approaches for Blind Decision Feedback Equalizer Adaptation (소프트 판정을 이용한 자력복구 적응 판정궤환 채널등화 기법)

  • Chung Won-Zoo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.8 s.350
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    • pp.69-76
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    • 2006
  • In this paper, we propose blind adaptation strategies for decision feedback equalizer (DFE) optimizing the operation mode between acquisitionand tracking modes based on adjustable soft decision devices. The proposed schemes select an optimal soft decision device to generate feedback samples for the DFE at a given noise to signal ratio, and apply corresponding adaptation rules which combine a blind infinite impulse response (IIR) filtering adaptation and the decision-directed least mean squared (DD-LMS) DFE adaptation. These adaptation approaches attempt to achieve not only smooth transition between acquisition and tracking of DFE but also mitigation of error propagation.

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.

Blind Algorithms with Decision Feedback based on Zero-Error Probability for Constant Modulus Errors

  • Kim, Nam-Yong;Kang, Sung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.12C
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    • pp.753-758
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    • 2011
  • The constant modulus algorithm (CMA) widely used in blind equalization applications minimizes the averaged power of constant modulus error (CME) defined as the difference between an instant output power and a constant modulus. In this paper, a decision feedback version of the linear blind algorithm based on maximization of the zero-error probability for CME is proposed. The Gaussian kernel of the maximum zero-error criterion is analyzed to have the property to cut out excessive CMEs that may be induced from severely distorted channel characteristics. Decision feedback approach to the maximum zero-error criterion for CME is developed based on the characteristic that the Gaussian kernel suppresses the outliers and this prevents error propagation to some extent. Compared to the linear algorithm based on maximum zero-error probability for CME in the simulation of blind equalization environments, the proposed decision feedback version has superior performance enhancement particularly in cases of severe channel distortions.

Performance Analysis of Blind Adaptive Orthogonal-Decision-Feedback Multiuser Detector in Synchronous DS-CDMA (동기식 DS-CDMA에서 블라인드 적응형 부귀환 직교 다중사용자 검파기의 성능평가)

  • 김우성;곽경섭
    • 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.

Performance analysis of decision feedback equalizer with dual-feedback in pre-ghost channel (이중 후방필터 구조 결정 궤환 등화기의 선행 고스트에 대한 성능 분석)

  • Oh, Young-Ho;Lee, Kyoung-Won;Kim, Dae-Jin
    • Journal of Broadcast Engineering
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    • v.12 no.5
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    • pp.516-524
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    • 2007
  • In order to use limited frequency resources efficiently, a single frequency network using digital on-channel repeater(DOCR) has been studied and would be implemented. The DOCR generates strong pre-ghosts to ATSC DTV receivers. The forward filter of equalizer in ATSC DTV receivers compensates the distortion made by pre-ghosts. This process induces noise enhancement and colored noise, thereby results in the performance degradation. In this paper we propose to use a dual-feedback equalizer to combat strong pre-ghosts. The proposed equalizer has two feedback filters. One is the decision feedback filter and the other is non-decision feedback filter. The additional non-decision feedback filter decreases the noise by whitening the noise and preventing the generation of colored noise in pre-ghost channel. Thus the equalization technique of dual-feedback structure has performance enhancement in pre-ghost channel in comparison with conventional decision feedback equalizer(DFE). By simulation we analyzed the performance enhancements of DTV receiver using dual-feedback equalization structure.