• Title, Summary, Keyword: DFE

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An FPGA Implementation of an MML-DFE for Spatially Multiplexed MIMO Systems (공간다중화 MIMO 시스템을 위한 MML-DFE기법의 FPGA 구현)

  • Im, Tae-Ho;Lee, Kyu-In;Park, Chang-Hwan;Jeong, Ki-Cheol;Yu, Sung-Wook;Kim, Jae-Kwon;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.11A
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    • pp.1167-1175
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    • 2006
  • The ML-DFE(Maximum Likelihood-Decision Feedback Equalization) can be viewed as either a suboptimal signal detection method for reducing hardware complexity of ML or an enhanced detection method for reducing the effect of error propagation of SIC(Successive Interference Cancellation) in spatially multiplexed MIMO systems such as V-BLAST. The ML-DFE can achieve a higher diversity in rich scattering environments as well as reducing the error propagation effect by combing ML decoding with the DFE. In this paper, an MML-DFE(Modified Maximum Likelihood-Decision Feedback Equalization) is proposed to reduce the hardware complexity of the ML-DFE, without compromising performance. It is shown by FPGA implementation that the proposed MML-DFE can achieve the same performance as the ML-DFE with significantly reduced hardware complexity.

High Speed Low Power Decision-Feedback Equalizer Techniques (고속 저전력 결정-피드백 이퀄라이저 기술 동향)

  • Min, Woong-Ki;Kong, Bai-Sun
    • Journal of IKEEE
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    • v.20 no.3
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    • pp.285-290
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    • 2016
  • Inter-symbol interference (ISI) due to channel bandwidth limitation constrains the maximum data rate in high speed I/O. Decision feedback equalizer (DFE) is known as the most popular technique for removing ISI. To ensure fast data transmission, not only removing ISI but also raising maximum operating frequency of the circuit itself by relaxing feedback delay margin is important. For single-ended signaling, DFE should cancel out both ISI and high frequency noises. Low-power operation is as important as fast operation because required DFE elements increase as the data rate goes up. This paper surveys recent techniques for fast DFE by removing ISI and high frequency noises, and low power DFE and discusses about their merits and limitations.

Performance Comparison and Analysis of SC-FDMA Systems employing IB-DFE (IB-DFE를 적용한 SC-FDMA 시스템의 성능 비교 분석)

  • Cho, Jae-Deok;Ahn, Sang-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.9C
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    • pp.906-914
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    • 2009
  • SC-FDMA is employed in the 3GPP-LTE standard as the uplink transmission scheme. SC-FDMA has advantages that the signal has a low PAPR property and a simple equalizer such as FD-LE can be implemented. But FD-LE has inferior performance to Hybrid-DFE composed of frequency-domain feedforward filter and time-domain feedback filter. Recently, several IB-DFE algorithms have been proposed to overcome the disadvantages of implementation and processing complexity of Hybrid-DFE and to obtain superior performance to FD-LE. In this paper, we apply several IB-DFE algorithms to 3GPP-LTE uplink system and compare their performance by calculating BER. We investigate the effects of channel estimation errors and Doppler shift on performance. Finally, by analyzing computational complexity of IB-DFEs, we present some criteria to choose appropriate algorithm and to decide the number of iterative processes.

Differencing Multiuser Detection Using Error Feedback Filter for MIMO DS-UWB System in Nakagami Fading Channel

  • Kong, Zhengmin;Fang, Yanjun;Zhang, Yuxuan;Peng, Shixin;Zhu, Guangxi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.10
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    • pp.2601-2619
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    • 2012
  • A differencing multiuser detection (MUD) method is proposed for multiple-input multiple-output (MIMO) direct sequence (DS) ultra-wideband (UWB) system to cope with the multiple access interference (MAI) and the computational efficiency in Nakagami fading channel. The method, which combines a multiuser-interference-cancellation-based decision feedback equalizer using error feedback filter (MIC DFE-EFF), a coefficient optimization algorithm (COA) and a differencing algorithm (DA), is termed as MIC DFE-EFF (COA) with DA for short. In the paper, the proposed MUD method is illuminated from the rudimental MIC DFE-EFF to the advanced MIC DFE-EFF (COA) with DA step by step. Firstly, the MIC DFE-EFF system performance is analyzed by minimum mean square error criterion. Secondly, the COA is investigated for optimization of each filter coefficient. Finally, the DA is introduced to reduce the computational complexity while sacrificing little performance. Simulations show a significant performance gain can be achieved by using the MIC DFE-EFF (COA) with DA detector. The proposed MIC DFE-EFF (COA) with DA improves both bit error rate performance and computational efficiency relative to DFE, DFE-EFF, parallel interference cancellation (PIC), MIC DFE-EFF and MIC DFE-EFF with DA, though it sacrifices little system performance, compared with MIC DFE-EFF (COA) without DA.

Design of a Blind DFE Equalizer for high-speed data communication (고속 데이터 통신을 위한 Blind DFE Equalizer의 설계)

  • 박원흠;선우명훈
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.7C
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    • pp.704-711
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    • 2002
  • This paper proposes a DFE (Decision Feedback Equalizer) equalizer ASIC using the Multi-Modulus Algorithm (MMA) for cable modem applications. We believe that it is the first effort to combine the DFE structure and the MMA algorithm. The proposed equalizer has been designed for 64/256 QAM modems. The existing MMA equalizer uses two transversal filters and updates two tap weights while the proposed equalizer uses two DFE filter banks to improve the channel adaptive performance and to reduce the number of taps and updates only one tap weights. We have used the 0.35 $\mu\textrm{m}$ standard cell library. The implemented equalizer ASIC operates at 8 MHz and provides 64 Mbps which is higher than existing equalizers. The total number of gates are about 160,000.

Near-Optimum Blind Decision Feedback Equalization for ATSC Digital Television Receivers

  • Kim, Hyoung-Nam;Park, Sung-Ik;Kim, Seung-Won;Kim, Jae-Moung
    • ETRI Journal
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    • v.26 no.2
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    • pp.101-111
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    • 2004
  • This paper presents a near-optimum blind decision feedback equalizer (DFE) for the receivers of Advanced Television Systems Committee (ATSC) digital television. By adopting a modified trellis decoder (MTD) with a trace- back depth of 1 for the decision device in the DFE, we obtain a hardware-efficient, blind DFE approaching the performance of an optimum DFE which has no error propagation. In the MTD, the absolute distance is used rather than the squared Euclidean distance for the computation of the branch metrics. This results in a reduction of the computational complexity over the original trellis decoding scheme. Compared to the conventional slicer, the MTD shows an outstanding performance improvement in decision error probability and is comparable to the original trellis decoder using the Euclidean distance. Reducing error propagation by use of the MTD in the DFE leads to the improvement of convergence performance in terms of convergence speed and residual error. Simulation results show that the proposed blind DFE performs much better than the blind DFE with the slicer, and the difference is prominent at the trellis decoder following the blind DFE.

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Blind Decision Feedback Equalizer with a Modified Trellis Decoder for ATSC DTV Receivers (ATSC DTV 수신기를 위해 변형된 트렐리스 복호기를 사용하는 블라인드 판정 궤환 등화기)

  • 박성익;김형남;김승원;이수인
    • Journal of Broadcast Engineering
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    • v.8 no.4
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    • pp.481-491
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    • 2003
  • We present a near-optimal blind decision feedback equalizer (DFE) for Advanced Television Systems Committee digital television (DTV) receivers. By adopting a modified trellis decoder (MTD) with trace back depth of 1 for the decision device In the DFE, we obtain a hardware-efficient near-optimal blind DFE approaching to the optimal DFE which has no error propagation. The MTD uses absolute distance instead of Euclidean distance for computation of a path metric, resulting. In reduced computational complexity. Comparing to the conventional slicer, the MTD shows outstanding performance improvement of decision error probability and is comparable to the original trellis decoder using Euclidean distance. Reducing error propagation in the DFE leads to the improvement of convergence performance in terms of convergence speed and residual error. Simulation results show that the proposed blind DFE performs much better than the blind DFE with the slicer.

Performance Analysis of Adaptive Equalizers to Enhance DTV Receiving Performance (DTV수신 성능 향상을 위한 적응 등화기의 성능 분석)

  • Yoon, Young-Jun;Sohn, Won
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.533-536
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    • 2001
  • 지상파 DTV 전송 시스템은 "training sequence"를 이용한 결정 궤환 등화기(DFE)를 사용한다. 이 등화기는 정적 다중경로 환경에서는 심볼 간의 간섭을 적절히 제거하는 반면, 동적 다중경로 환경에서는 "training sequence" 의 주기가 채널 효율 문제로 충분히 짧지 않기 때문에 충분히 제거하지 못하는 것으로 보고되고 있다. 이 논문에서는 이 문제점을 해결하기 위해서 "training sequence" 를 이용한 DFE와 선형 등화기, 블라인드 DFE와 선형 등화기 및 혼합형 DFE를 구현하여 정적 채널과 동적 채널에 대한 성능을 분석하였다.

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Dandelion (Taraxacum officinale) Flower Ethanol Extract Inhibits Cell Proliferation and Induces Apoptosis in Human Ovarian Cancer SK-OV-3 Cells

  • Choi, Eun-Jeong;Kim, Gun-Hee
    • Food Science and Biotechnology
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    • v.18 no.2
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    • pp.552-555
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    • 2009
  • This study investigated the proapoptotic effect of ethanol extracts obtained from dandelion (Taraxacum officinale) flower on human ovarian cancer SK-OV-3 cells. Cells were treated with dandelion flowers ethanol extract (DFE) ranging from 1.5625 to $100{\mu}g/mL$ for 24 hr. Significant antiproliferative effects of DFE were first observed from at $6.25{\mu}g/mL$ (p<0.05), and this inhibition showed in a dose-dependent manner. When cells were treated with more than $6.25{\mu}g/mL$ DFE, cell-cycle analysis showed that DFE caused an increase in the percentage of sub-G0/G1 cells and arrested at the S and G2/M phase in a dose-dependent manner. Moreover, apoptosis induction by DFE involved p53 activation and bax upregulation as well as downregulation of bcl-2. Our findings indicate that DFE resulted in apoptotic cell death, suggesting that DFE possesses potential anticancer properties.

A Study on the Performance Improvement in Equalization of DTV using DCT HLMS DFE (DCT HLMS DFE를 이용한 DTV 등화 성능 개선 연구)

  • 김재욱;서종수
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.27-30
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    • 2002
  • 본 논문은 8VSB 방식의 디지털 지상파 TV 시스템에서 수신 채널 등화기의 수렴속도와 MSE(Mean Square Error) 성능을 개선하기 위하여 DCT HLMS DFE(Discrete Cosine Transform Hierarchical Least Mean Square)를 제안한다. 즉, 다중경로 수신 환경에서 수신 신호의 왜곡 및 지연에 따른 입력 데이터에 대한 고유값 확산을 감소하기 위하여 DCT와 전력추정 알고리즘을 사용하고 또한, LMS(Least Mean Square) DFE를 계층적 구조의 서브필터로 변형함으로써 수신 데이터상관 행렬의 고유값 범위를 줄인다. 전산모의 실험 결과 제안한 DCT HLMS DFE는 ATTC(Advanced Television Test Center)가 제시한 디지털 지상파 TV 방송 채널 중 A 채널 하에서 기존의 LMS DFE 보다 수렴속도와 MSE 성능이 개선됨을 알 수 있다.

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