• Journal of Broadcast Engineering
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• v.12 no.5
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• pp.516-524
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• 2007

In order to use limited frequency resources efficiently, a single frequency network using digital on-channel repeater(DOCR) has been studied and would be implemented. The DOCR generates strong pre-ghosts to ATSC DTV receivers. The forward filter of equalizer in ATSC DTV receivers compensates the distortion made by pre-ghosts. This process induces noise enhancement and colored noise, thereby results in the performance degradation. In this paper we propose to use a dual-feedback equalizer to combat strong pre-ghosts. The proposed equalizer has two feedback filters. One is the decision feedback filter and the other is non-decision feedback filter. The additional non-decision feedback filter decreases the noise by whitening the noise and preventing the generation of colored noise in pre-ghost channel. Thus the equalization technique of dual-feedback structure has performance enhancement in pre-ghost channel in comparison with conventional decision feedback equalizer(DFE). By simulation we analyzed the performance enhancements of DTV receiver using dual-feedback equalization structure.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.1
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• pp.13-20
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• 2005

This paper addresses a new blind channel equalization method using fourth-order cumulants of channel inputs and a three-layer neural network equalizer. The proposed algorithm is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum-phase characteristic of the channel. The transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel inputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple recordering and scaling. By using this estimated deconvolution matrix, which is the inverse of the over-sampled unknown channel, a three-layer neural network equalizer is implemented at the receiver. In simulation studies, the stochastic version of the proposed algorithm is tested with three-ray multi-path channels for on-line operation, and its performance is compared with a method based on conventional second-order statistics. Relatively good results, withe fast convergence speed, are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.2
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• pp.253-260
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• 2018

The acoustic communication channel in shallow underwater is typically shown as time-varying multipath fading channel characteristics. The received signal through channel transmission cause inter-symbol interference (ISI) owing to multiple components of different time delay and amplitude. To compensate for this, several techniques have been used, and one of them is acoustic equalizer. In this study, we used four equalizers - feed forward equalizer (FFE), decision directed equalizer (DDE), decision feedback equalizer (DFE) and combination DDE with DFE to compensate ISI. And we applied two adaptive algorithms to adjust coefficient of equalizers - normalized least mean square algorithm and recursive least square algorithm. As result, we found that it has a significant performance improvement over 6 dB on SNR in nonlinear equalizer. By combination of DFE and DDE has almost best performance in any case.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.683-688
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• 1999

This paper describes design of equalizer chips of the read channel for high-density hard-disk drives. In order to meet increasing need of hard-disk drives, the read channel incorporates various PRML schemes. They require proper equalization to implement the efficient hardware of Viterbi decoders. This paper describes EPR-IV equalization for the read channel and a 200MHz analog FIR filter chip is presented which utilizes the sampled analog signal processing efficiently.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.54.4-54
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• 2002

1.Introduction 2. Channel Equalizer Using Adaptive Neural Network 3. Data Modulation and Demodulation Using Haar Transform 4. Binary Signal Transmission Using Haar Transform 5. Conclusion

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.19-26
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• 2010

The criterionmaximizing cross-correntropy (MCC) of two different random variables has yielded superior performance comparing to mean squared error criterion. In this paper we present a complex-valued blind equalizer algorithm for QAM and complex channel environments based on cross-correntropy criterion which uses, as two variables, equalizer output PDF and Parzen PDF estimate of a self-generated symbol set. Simulation results show significantly enhanced performance of symbol-point concentration with no phase rotation in complex-channel communication.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.43-49
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• 2007

In this paper, the performance of OFDM/64QAM systems under Rummler model based cable channel is evaluated through computer simulation, and then the degree of performance improvement is estimated when adopting adaptive LMS equalizer. From the performance evaluation results, in the Rummler two-ray channel model, it is known that the performance improvement degree by adopting equalizer is greatly increased in case of attenuation coefficient of reflected ray (b) being less than 0.15, but when attenuation coeffcient (b) is larger than 0.15, the performance improvement degree by adopting equalizer shows little changes in almost all range of Eb/No.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.435-441
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• 2001

In this paper, we proposed adaptive MMSE receiver, which use channel equalizer to eliminate the interference due to multi-path fading and adaptive filter to eliminate the multiple access interference. The unique features of proposed receiver schemes are as following. We use pilot channel to estimate the channel coefficients exactly and guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signals. The length of channel equalizer also can be reduced with the help of guard symbols. Especially utilizing adaptive code-matched filter(AMMSE) when the user population is high and SNR is not low we accepts excellent performance improvement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.623-631
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• 2010

In this paper, various of pilot-assisted channel estimation techniques for 3GPP LTE downlink are tested under multipath Rayleigh fading channel. At first, the conventional channel estimation techniques are applied with linear zero-forcing (ZF) equalizer, such as one dimensional least square (1-D LS) linear interpolation, two dimensional (2-D) wiener filter, the time and frequency dimension separate wiener filter and maximum likelihood estimator (MLE). Considering the practical implementation, we proposed two channel estimation techniques by combining time-dimension wiener filter and MLE in two manners, which showed a good tradeoff between system performance and complexity when comparing with conventional techniques. The nonlinear decision feedback equalizer (DFE) which can show a better performance than linear ZF equalizer is also implemented for mitigating inter-carrier interference (ICI) in our system. The complexity of these algorithms are calculated in terms of the number of complex multiplications (CMs) and the performances are evaluated by showing the bit error rate (BER).

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.677-683
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• 2010

In this paper, a channel estimation scheme for high-speed Binary CDMA systems is proposed and its performances are investigated. In high-speed Binary CDMA which adopt high order modulations, since BER(bit error rate) performances are deteriorated when equalizer does not converge enough during preamble period it is preferred to set the optimum coefficients of equalizer through channel estimation. In this paper, taking notice of repetition of CAZAC sequence in preamble period, a channel estimation scheme is proposed, which can improve estimation performances with few complexity increase. From the simulation results, one can see that the proposed channel estimation scheme can be implemented simply with no performance deterioration compared to the conventional one.