Improvement of bit-error-rate in decision feedback equalizer by preventing decision-error propagation

Fertner, Antoni

doi:10.1109/78.700956

Cited by 25 publications

(19 citation statements)

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“…ISI가 발생할 경우 통신신호의 전송 출력을 높이더 라도 수신된 신호의 간섭성분의 전력 또한 높아져 서 SINR이 신호 대 간섭비 (SIR, signal-to-interference ratio)로 수렴하므로 비트 오류율 향상에 한계를 유발 한다 [14] . 수중음향채널에서 이러한 ISI를 제거하기 위한 방법으로 적응형 선형 등화와 결정궤환 등화 방법이 제안되었다 [4][5][6][7][8][9][10][11][12][13] . 선형 등화 방법은 선형 등화 필터를 이용하며 연산량이 적고 주로 ISI의 감소 효 과를 얻을 수 있다 [6,9,11,12] .…”

Section: 기존의 적응형 등화기법unclassified

“…선형 등화 방법은 선형 등화 필터를 이용하며 연산량이 적고 주로 ISI의 감소 효 과를 얻을 수 있다 [6,9,11,12] . 그리고 결정궤환 등화 방 법은 궤환 탭을 갖는 필터를 이용하며 연산량은 상 대적으로 많지만 ISI를 효과적으로 제거할 수 있다 [4,5,7,8,10,13] . …”

Section: 기존의 적응형 등화기법unclassified

“…적응 형 등화기법에는 적응형 알고리즘과 결합된 선형 등 화와 결정궤환 등화기법이 사용될 수 있는데 선형 등화기법은 횡단선 등화기와 같은 선형 필터를 이용 하여 채널을 보상하는 방법으로 구조가 간단하다는 장점이 있으나 필터 계수를 산출하는 알고리즘에 따 라 잡음에 의한 영향이 커지거나 잔여 ISI가 남는 단 점이 있다 [12] . 그리고 결정궤환 등화기법은 일반적 인 횡단선 등화기에 궤환 필터를 추가시킨 구조로 잔여 ISI를 제거할 수 있는 장점이 있으나 낮은 SNR 범위에서 검출 오류에 의한 오류 전파가 증가하여 오류 성능이 열화되는 단점이 있다 [13] . …”

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Equalizer Mode Selection Method for Improving Bit Error Performance of Underwater Acoustic Communication Systems

Kim¹,

Seo²,

Kim³

et al. 2012

The Journal of the Acoustical Society of Korea

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ABSTRACT: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.

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Section: 기존의 적응형 등화기법unclassified

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Equalizer Mode Selection Method for Improving Bit Error Performance of Underwater Acoustic Communication Systems

Kim¹,

Seo²,

Kim³

et al. 2012

The Journal of the Acoustical Society of Korea

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“…We also do not focus on the effect of errors in other components of the system (specifically, the feedback filter. Error propagation in the feedback filter has been an emphasis of prior research-see, for instance, [14], [44] and [46]). …”

Section: The Problem Statementmentioning

confidence: 99%

Direct-form adaptive equalization for underwater acoustic communication

Yellepeddi¹

2012

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Adaptive equalization is an important aspect of communication systems in various environments. It is particularly important in underwater acoustic communication systems, as the channel has a long delay spread and is subject to the effects of timevarying multipath fading and Doppler spreading.The design of the adaptation algorithm has a profound influence on the performance of the system. In this thesis, we explore this aspect of the system. The emphasis of the work presented is on applying concepts from inference and decision theory and information theory to provide an approach to deriving and analyzing adaptation algorithms. Limited work has been done so far on rigorously devising adaptation algorithms to suit a particular situation, and the aim of this thesis is to concretize such efforts and possibly to provide a mathematical basis for expanding it to other applications.We derive an algorithm for the adaptation of the coefficients of an equalizer when the receiver has limited or no information about the transmitted symbols, which we term the Soft-Decision Directed Recursive Least Squares algorithm. We will demonstrate connections between the Expectation-Maximization (EM) algorithm and the Recursive Least Squares algorithm, and show how to derive a computationally efficient, purely recursive algorithm from the optimal EM algorithm.Then, we use our understanding of Markov processes to analyze the performance of the RLS algorithm in hard-decision directed mode, as well as of the Soft-Decision Directed RLS algorithm. We demonstrate scenarios in which the adaptation procedures fail catastrophically, and discuss why this happens. The lessons from the analysis guide us on the choice of models for the adaptation procedure. We then demonstrate how to use the algorithm derived in a practical system for underwater communication using turbo equalization. As the algorithm naturally incorporates soft information into the adaptation process, it becomes easy to fit it into a turbo equalization framework. We thus provide an instance of how to use the information 3 of a turbo equalizer in an adaptation procedure, which has not been very well explored in the past. Experimental data is used to prove the value of the algorithm in a practical context.

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“…However, the decision errors from the equalizer/detector may result in erroneous cancellation of the postcursor ISI through the feedback filter (FBF) [2] and consequently degrade the overall performance. There have been some ad hoc techniques proposed to deal with the error propagation problem by using erasures [3], error decision threshold [4] or a soft decision device [5]. In [6], some constraints were used in deriving the feedforward filter (FFF) to monitor decision error and ensure ISI cancellation.…”

Section: Introductionmentioning

confidence: 99%

Decision-Feedback Detection for MIMO-ISI Channels: Design Using Fixed and Adaptive Constraints

Nguyen

Choi

2007

IEEE Trans. Veh. Technol.

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Abstract-In this correspondence, we investigate the decision feedback detection for multiple-input multiple-output intersymbol interference (MIMO-ISI) channels. Firstly, a novel constrained symbol-by-symbol decision feedback detector (CS-DFD) is proposed, in which a constraint on the feedback filter (FBF) provides robustness against error propagation and outperforms the conventional decision feedback detector (DFD). However, we find that an error floor is observed at high signal-to-noise ratios (SNRs) if a fixed constraint is used. To resolve this problem, we then propose an iterative symbol-by-symbol decision feedback detector (IS-DFD) in which an adaptive constraint is implicitly used to update the DFD's coefficients. Simulation results show that the error floor problem is overcome and the performance becomes satisfactory at high SNRs through iterations.Index Terms-Multiple-input multiple-output intersymbol interference (MIMO-ISI) channel, decision feedback detection, error propagation, constrained optimization, iterative processing.

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Improvement of bit-error-rate in decision feedback equalizer by preventing decision-error propagation

Cited by 25 publications

References 11 publications

Equalizer Mode Selection Method for Improving Bit Error Performance of Underwater Acoustic Communication Systems

Equalizer Mode Selection Method for Improving Bit Error Performance of Underwater Acoustic Communication Systems

Direct-form adaptive equalization for underwater acoustic communication

Decision-Feedback Detection for MIMO-ISI Channels: Design Using Fixed and Adaptive Constraints

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