• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3434-3439
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• 2015

As a criterion of information theoretic learning, the Euclidean distance (ED) of two error probability distribution functions (minimum ED of error, MEDE) has been adopted in nonlinear (decision feedback, DF) supervised equalizer algorithms and has shown significantly improved performance in severe channel distortion and impulsive noise environments. However, the MEDE-DF algorithm has the problem of heavy computational complexity. In this paper, the recursive ED for MEDE-DF algorithm is derived first, and then the feed-forward and feedback section gradients for weight update are estimated recursively. To prove the effectiveness of the recursive gradient estimation for the MEDE-DF algorithm, the number of multiplications are compared and MSE performance in impulsive noise and underwater communication environments is compared through computer simulation. The ratio of the number of multiplications between the proposed DF and the conventional MEDE-DF algorithm is revealed to be $2(9N+4):2(3N^2+3N)$ for the sample size N with the same MSE learning performance in the impulsive noise and underwater channel environment.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.2
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• pp.53-57
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• 2002

Recently, digital communication system becomes high speed, as communication demand dose not only increases sharply, but an image, voice various kinds data also comes multimedia. In transmitting data at a high speed, the main problem is fading by multipath. A linear or nonlinear distortion arise In multipath channel fading from ISI(Intersymbol Interference). For restoring this distorted signal, A lot of equalizer and adaptive algorithm is introduced. This paper compares and analysises, for improving communication quality in channel which is long delay spread, performance of decision feedback equalizer by RLS algorithm, a channel estimation by RLS-MLSE and viterbi equalizer Particularly, there Is exactly channel estimation of impluse response and excellent property of equalization about channel, which delay spread is long impluse response comparatively and is property of non-minimun phase.

• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.169-173
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• 2012

In this paper, we propose an equalizer to minimize the inter-symbol interference when PSSK(Phase Silence Shift Keying) technique is applied to the low power underwater acoustic communication. PSSK is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation), and it was proposed for low power communication. However, it has poor performance due to delay spread of underwater channel. In this paper, we propose a decision feedback equalizer to minimize the error in PSSK receiver. The sea trial was performed to evaluate the performance of the proposed method. In the result, the BER of PSSK was $4.36{\times}10^{-2}$ before the equalizer was applied, but the BER of PSSK was $3.95{\times}10^{-4}$ after the proposed equalizer was applied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.491-498
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• 2012

Recently, many papers have been proposed in order to improve the OFDM system performance in T-DMB DOCR (Digital On Channel Repeater), by using removing the feedback signal so that the transmitter power can be increased or by using the equalizer to remove ICI. Despite these efforts, however, signal quality at the receiving terminal has not been improved because of constellation smearing in T-DMB DOCR. In this paper, in order to suppress constellation smearing, we propose an effective equalizer algorithm that can improve system performance. We perform adaptive channel estimation and non-coherent decision directed noise cancellation method that can estimate the channel subsequently during data symbols period in the frequency domain. So we can obtain better quality of the signal at the receiving terminal. In order to secure QoS(Quality of Service) required in T-DMB handsets, we evaluate SNR and BER in T-DMB DOCR(Digital On Channel Repeater) and verified by simulation. In this simulation results, this system is satisfied the performance of BER=$10^{-5}$ at less than SNR=14 dB at the receiver after compensation of phase noise -18 dBc.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.7-10
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• 2003

VDSL(Very-high-rate Digital subscriber Line) have a severe FEXT(Far-End Crosstalk). This paper proposes FEXT cancelation scheme in VDSL system. The scheme is GDFE(Generalize Decision Feedback Equalizer) and Vectored-DMT (Discrete Multitone). Feedback part of GDFE decreases FEXT noise. Canceler and Precoder block a part of Vectored-DMT eliminate FEXT. After all, simulation result show improvement of transmit and receive speed.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.63-75
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• 2010

In this paper, the equalizer techniques that is able to adopt the digital on-channel repeater for 8VSB-based DTV system has been analyzed and we propose an effective equalizer structure which can reduce the error propagation phenomenon by the feedback signal and improve the receiver performance at the same time. In order to confirm the effective cancellation of the feedback signal, the multi-level Correlation LMS scheme is proposed through the analysis of conventional basic LMS based DFE and Correlation LMS algorithm and as compared with the conventional method, we can confirm the reduction of error propagation. When performing the computer simulation, as the Brazil channel model which is very popular for DTV broadcasting system is adopted, the result is drawn by comparing and analysing the equalizer algorithm. We have examine the symbol error rate which is in the range of 15~25dB of operation receipt SNR and MSE(Mean Square Error) in the DTV broadcasting system. As a result of comparing with the existing method, the signal-noise ratio which is necessary for maintain the bit error correction ability that the means of proposal is same is reduced by about 2~5dB, and in the rate of convergence through the MSE, we found the reduction of needed time.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.69-74
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• 2006

In this paper, we present symbol detection methods for decision feedback equalizers (DFE) in trellis coded modulation systems. The proposed symbol detectors improve symbol error rate (SER) by exploiting the coding structure of trellis coded modulation (TCM). For example, for 8-PAM signals the achieved SER with the proposed detection scheme is improved to $2{\times}10^{-5}$ from $2.5{\times}10^{-2}$ of the conventional symbol-by-symbol detector under AWGN channel at 20dB SNR. This SER improvements mitigate error propagation of DFE.and produces significant over-all SER improvement for under multipath channels (for example, from 0.26 to 0.01 and 0.005 under a severe multipath channel 20dB SNR as shown in the simulation result of this paper).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.12
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• pp.60-69
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• 2000

This paper describes a single-chip full-custom implementation of pipelined adaptive decision-feedback equalizer(PADFE) using a 0.25-${\mu}m$ CMOS technology for wide-band wireless digital communication systems. To enhance the throughput rate of ADFE, two pipeline stages are inserted into the critical path of the ADFE by using delayed least-mean-square(DLMS) algorithm. Redundant binary (RB) arithmetic is applied to all the data processing of the PADFE including filter taps and coefficient update blocks. When compared with conventional methods based on two's complement arithmetic, the proposed approach reduces arithmetic complexity, as well as results in a very simple complex-valued filter structure, thus suitable for VLSI implementation. The design parameters including pipeline stage, filter tap, coefficient and internal bit-width, and equalization performance such as bit error rate (BER) and convergence speed are analyzed by algorithm-level simulation using COSSAP. The single-chip PADFE contains about 205,000 transistors on an area of about $1.96\times1.35-mm^2$. Simulation results show that it can safely operate with 200-MHz clock frequency at 2.5-V supply, and its estimated power dissipation is about 890-mW. Test results show that the fabricated chip works functionally well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.295-301
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• 2011

In [1], it has been shown that the energy spreading transform (EST) based iterative equalizer (IE) could enhance its performance by improving the reliability of the decision feedback symbols without the help of the complicated channel decoder. In the matched filter (MF) based IE proposed in [1], however, its feedforward filter (FFF) has been designed in the frequency domain while its feedback filter (FBF) in the time domain. So its complexity increases proportional to the channel memory length. To solve this problem, in this paper, both FFF and FBF are designed in the frequency domain. This enables the proposed frequency domain IE (FD-IE) to achieve the lower complexity over the conventional method in the highly dispersive channel. In addition, simulation results demonstrate that the BER performance of the proposed method is the same as the conventional.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.103-118
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• 1999

This paper analyzes the performance of symbol timing recovery and equalizer in 8VSB digital terrestrial TV receiver under various multipath signals and proposes equalization techniques which improve indoor reception performance. Data segment sync is used for symbol timing recovery and timing offset is measured for echoes of various delays and amplitudes by using symbol timing detection filter whose pattern is +1. +1. -1. and -1. Measured timing offsets were below 10% for long echoes with more than 5 symbol delay and above 30% for short echoes with around 1 symbol delay. Indoor reception is always more challenging than outdoor reception due to lower signal strength. large and short multipaths. and moving interfering objects. So it is considered to use FSE (Fractionally Spaced Equalizer) which is very robust to timing offset and blind equalizer which can update equalizer tap coefficients even by information data. We compare the performance of conventional DFE (Decision Feedback Equalizer) and FSE-DFE using LMS algorithm and Stop and Go algorithm for the indoor reception. Experiments reveals FSE has excellent performance for large timing offset and Stop and Go algorithm shows good performance for Doppler shift. so we propose to use FSE-DFE structure with Stop and Go algorithm for the reliable indoor reception.