• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06a
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• pp.23-26
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• 1996

본 논문에서는 선형궤환 등화방식과 결정궤환 복조방식을 결합하여 차동 PSK 신호검출에 필요한 등화기 구조를 제안한다. 이 등화기의 출력을 등화기의 궤환부로 입력하기 앞서, 결정궤환 복조방식에 근거하여 적절히 변형함으로써 제안된 구조는 마치 결정궤한 등화기처럼 동작한다. 모의 실험 결과는 실제로 제안된 등화기가 기존의 차동검파 방식의 등화기 보다 월등한 성능을 나타내고, 동기검파를 위한 결정궤환 등화기에 근접한 성능을 가짐을 보여준다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1706-1715
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• 1996

The decision feedback equalizer(DFE) received recent attention since it can compensate for channels with severe intersymbol interference(ISI) without as much noise enhancement as the linear equalizer(LE). In this paper, we propose a new DFE which can icrease the performance of DFE further by using error feedback. The performance increase is achieved by reducing correlation of error signal, which cannot be reduced by the feedforward or feedback filter. Hardware complexity for the proposed approcach is minimal since it requires only additional few taps to the conventional DFE. Based on theoretical analysis and computer simulations, the proposed approach is shown to be much more effective than the conventional DFE, especially for channels with large ISI.

• 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.

• 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.

• The Journal of the Acoustical Society of Korea
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• v.31 no.1
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• pp.1-10
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• 2012

The linear and decision-feedback equalization can mitigate time-varying intersymbol interference (ISI) caused by time-varying multipath propagation for underwater acoustic channels. The perfect elimination of interference components, however, is difficult using the linear equalization and the decision feedback equalizer has an error propagation problem. To overcome these shortcomings, this paper proposes an equalizer mode selection method using training sequences. The proposed method selects an equalization mode corresponding to the signal-to-noise ratio (SNR). If the SNR is low, the proposed system operates the linear equalizer for preventing the error propagation and if the SNR is high, the decision feedback equalizer for eliminating the residual ISI. Therefore, the proposed method can improve the error performance compared to the conventional equalizers. The computer simulation shows the proposed method improves the bit error performance using practical underwater channels responses acquired from the sea experiment.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.12
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• pp.103-108
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• 1998

The increase in the capacity of the digital magnetic recording systems inevitably causes severe intersymbol interference (ISI) and nonlinear distortions in the digital magnetic recording channel. In this paper, to cope with severe ISI and nonlinear distortions a neural decision feedback equalizer (NDFE) is applied to the digital magnetic recording channel - partial erasure channel model. In the performance comparison of bit error probability (or bit error ratio : BER) between the NDFE and the conventional decision feedback equalizer (DFE) via computer simulations. It has been found that as nonlinear distortions increase the NDFE has more SNR (SIgnal-to-Noise Ratio) advantage over the conventional DFE. In addition, in spite of the same recording density, as nonlinear distortions are increased, NDFE has the better performance of BER and the greater stability over conventional DFE.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.343-347
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• 2012

Non-linear equalization techniques using decision feedback structure are highly demanded for cancellation of intersymbol interferences occurred in severe channel environments. In this paper decision feedback structure is applied to the linear blind equalizer algorithm that is based on information theoretic learning and a randomly generated symbol set. At the decision feedback equalizer (DFE) the random symbols are generated to have the same probability density function (PDF) as that of the transmitted symbols. By minimizing difference between the PDF of blind DFE output and that of randomly generated symbols, the proposed DFE algorithm produces equalized output signal. From the simulation results, the proposed method has shown enhanced convergence and error performance compared to its linear counterpart.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1794-1801
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• 2001

다중 반송파 변조의 일종인 OFDM(Orthogonal Frequency Division Multiplexing) 방식은 기존의 주파수 분할 다중화 기법에 각 부 채널들 사이의 직교성까지 보장함으로써 사용 주파수 효율을 극대화시킬 수 있는 방식이다. 그러나 주파수 비 선택적 다중경로 채널에서 높은 데이터 율을 갖는 OFDM 신호의 전송은 주파수 영역에서 인접 심벌간 간섭과 동일한 형태를 갖는 승산성 왜곡에 의해 영향을 받는다. 본 논문에서는 결정 궤환 시퀀스 등화기를 OFDM 시스템에 적용하여 신호를 등화하고, 등화를 통하여 주파수 영역에서의 인접 심벌간 간섭을 보상하는 방법을 제안한다. 결정 궤환 시퀀스 등화를 이용하여 최우 시퀀스 등화가 갖는 복잡도를 크게 줄이면서 주파수 오프셋이 추정될 수 있음을 설명하고 모의 실험을 통해 OFDM 시스템의 성능 개선을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11B
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• pp.1884-1894
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• 2000

광대역 무선 통신 시스템에서는 주파수 선택적 다중경로 페이딩 채널상에서 발생하는 인접 심볼간의 간섭에 의한 성능 열화를 극복하기 위해서 채널 등화 기술의 도입이 필연적이다. 그러나, 데이터 전송률이 증가함에 따라 채널 등화에 필요한 훈련열의 길이가 늘어나고, 이로 인한 오버헤드를 감소하기 위해서는 보다 수렴률이 높은 적응 알고리즘이 요구된다. 본 논문에서는 주파수 영역의 적응 여파 기법 중의 하나인 자기 직교환 방식의 결정궤환 등화기를 고려한다. 이 채널 등화기에서는 적응 알고리즘으로 DCT-LMS (discrete cosine transform least mean square) 알고리즘을 채택함으로써 수렴률과 MSE (mean square error) 성능을 향상시켜 결과적으로 광대역 무선통신에서 요구되는 훈련열에 따른 오버헤드를 감소시킬 수 있게 된다. 시뮬레이션을 통해 주파수 선택적 다중경로 페이딩 채널에서의 제안된 채널 등화 기법에 대한 성능을 분석한다.