• 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.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1125-1128
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• 1998

A new architecture for high-speed implementation of adaptive decision-feedback equalizer (ADFE) applicable to wide-band digital wireless modems is described. Rather than using conventional two's complement arithmetic, a novel complex-valued filter structure is devised, which is based on redundant binary (RB) arithmetic. The proposed RB complex-valued filter reduces the critical path delay of ADFE, as well as leads to a more compact implementation than conventional methods. Also, the carry-propagation free (CPF) operation of the RB arithmetic enhances its speed. To demonstrate the proposed method, a prototype chip set is designed. They are designed to contain two complexvalued filter taps along with their coefficient updating circuits, and can be cascaded to implement loger filter taps for high bit-rate applications.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.199-205
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• 2011

This paper presents a QR decomposition processor by exploiting Givens rotation for the GDFE (Generalized Decision Feedback Equalizer). A Givens rotation consists of phase extraction, sine/cosine generation and angle rotation parts. Combining two-stage method (coarse and fine stage) and the fixed-width modified-Booth multiplier, we design an efficient QR decomposition processor. By simulations, it is shown that the proposed QR decomposition processor can be a feasible solution for GDFE.

• ETRI Journal
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• v.23 no.3
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• pp.121-128
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• 2001

In this paper, the theoretical as well as experimental results of BER characteristics of three different modulation schemes, ASK, FSK and BPSK, in a multi-path Rician channel are addressed. These BER characteristics are analyzed as a function of $E_b/N_o$ and the power ratio of the line of sight (LOS) component to the Rayleigh scattered component. The theoretical as well as computer simulation results shows the ASK is the most suitable modulation scheme for the dedicated short range communication (DSRC) in terms of implemental cost and system complexity. The decision feedback equalizer is proved to be very effective in canceling the multi-path interference in the DSRC channel environment. The simulation result of the equalized ASK, reveals the performance enhancement achievable with decision feedback (DFE) equalizer for the first generation DSRC system. The multi-ray DSRC channel model is also provided to predict the received carrier power and fluctuation, which are quite dependent on the surroundings of a cell.

• Journal of the Institute of Convergence Signal Processing
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• v.18 no.2
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• pp.37-42
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• 2017

In this paper, we study on symbol error rate(SER) performance of frequency domain decision feedback equalization for modelled underwater channel. Underwater channel is generated by Bellhop model. Simulation results show that proposed method is efficient for underwater acoustic communication.

• 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.

• 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.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.212-221
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• 2010

The bubbles could be created from multiple source in the surface of ocean. The bubbles which are created like this affect to the intensity and the sound speed of acoustic wave which are used from the ocean. From the research, it observed Reverberation from the sea surface, using Vbeam transmission and reception equipment that was a cross-shaped Array, from 2008 July 2nd to July 3rd at 4Km from the East Sea Mookho port. It is difficult to analyze data because the received signal has ambient noise and occurrence ISI(Inter Symbol Interference) for multipath. This paper remove that ambient noise and ISI using the directions of arrival beamforming and the filter and sum beamforming. After beamforming, a following DFE(Decision Feedback Equalizer) removes the remaining multipath components. Experimental results show that the proposed technique reduce the errors caused by ISI.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.5
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• pp.269-274
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• 2004

In this paper, proposed is the dual-mode algorithm of blind decision feedback equalizer (DFE) for digital terrestrial television signals. According to channel impairments, the proposed dual-mode algorithm for blind DFE operates in decision-directed mode or in blind mode of operation. The error signals being used in tap update of the equalizer are generated in the best mode of operations, so that the confidence of equalizer tap coefficient update is more accurate. As a result, it is possible to track the channel characteristics variations by automatic switching over between two modes of operations. For 8-level vestigial sideband modulated digital television signals, the mean square errors and symbol error rates of the proposed algorithm are compared with those of conventional methods. And the usability of the proposed scheme is assessed by computer simulations under various static and dynamic multipath channel environments.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.709-717
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• 2002

A new multi constant modulus algorithm (MCMA) for a blind decision feedback equalizer is proposed. In order to avoid the error propagation problem in the conventional DFE structure, Feed-Back Filter coefficients are updated only after Feed-Forward Filter coefficients are sufficiently converged to the steady state. Therefore, it has the problem of slow convergence speed characteristics. To overcome this drawback, the proposed MCMA algorithm uses not only new cost function considering the minimum distance between the received signal and the representative value containing the statistical characteristics of the transmitted signal, but also adaptive step-size according to the equalizer outputs to fast convergence speed of FBF. Simulations were carried out under the certified communication channel environment to evaluate a performance of the proposed equalizer. The simulation results show that the proposed equalizer has an improved convergence and SER performance compared with previous methods. The proposed techniques offer the possibility of practical equalization for cable modem and terrestrial HDTV broadcast (using 8-VSB or 64-QAM) applications.