• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.12
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• pp.2315-2325
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• 2011

We propose a novel reduced-state maximum-likelihood sequence detection (MLSD) structure using the Viterbi algorithm based on the second-order Volterra kernel modeling nonlinear distortion due to square law detection of multipath channels commonly occurring in chromatic dispersion (CD) or polarization mode dispersion (PMD) in optical communication systems. While all existing MLSD methods for square-law detection receivers are based on direct computation of branch metrics, the proposed algorithm provides an efficient and structured way to implement reduced-state MLSD with almost the same complexity of a MLSD for linear channels. As a result, the proposed algorithm reduces the number of parameters to be estimated and the complexity of computation.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.11
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• pp.83-96
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• 1996

On PR-IV magnetic recording systems, the maximum likelihood sequence detection (MLSD) method is optimum. But it has the problem of the complexity of the structure. The three level detection (TLD) method can be used, which has simpler structure than MLSD, but requires almost twice of power to achieve the same probbility of error as MLSD does. Therefore a new detection method (error controlled detection: ECD) is proposed which has much simpler structure than MLSD and gives much better performance than TLD. The simulation resutls show that the performance of ECD is better than that of TLD by approximaterly 0.5~1.3dB both in linear and nonlinear channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1522-1532
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• 1996

In this paper, we compare the performance of channel estimators with the L$_{1}$-norm and L$_{2}$-norm criteria in impulaive noise environment, and show than the L$_{1}$-norm criterion is appropriate for that situation. Also, it is shown that the performance of the conventional maximum likelihood sequence detector(MLSD) can be improved by applying the same principle to mobile channels. That is, the performance of the conventional MLSD, which is known to be optimal under the Gaussian noise assumption, degrades in the impulsive noise of radio mobile communication channels. So, we proposed the MLSD which can reduce the effect of impulsive noise effectively by applying the results of channel estimators. Finally, it is confirmed by computer simulation that the performance of MLSD is significantly affected depending on the types of branch metrics, and that, in the impulsive noise environments, the proposed one with new branch metrics performs better thatn the conventional branch metric, l y(k)-s(k) l$^{[-992]}$ .

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.746-760
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• 1998

In this paper, an adaptive RSSD(reduced-state sequence detection) receiver is proposed for the purpose of reducing the complexity and decision delay of the adaptive MLSD(maximum-likelihood sequence detection) receiver in the mobile satellite channel. The RSSD receiver reconstructs the trellis with a reduced number of states. The performance degradation due to the reduced states is compensated by modifying the branch metric calculation which uses the symbols in each path memory to estimate the residual ISI(intersymbol interference) terms. The structure of the proposed adaptive RSSD is a modified RSSD utilizing a per-survivor processing as well as the symbol-aided method and a channel estimation using the tentative data sequences. The complexity and performance of the proposed adaptive RSSD are controlled by the number of system states and ISI cancelers and the inserting period of the known symbols. In spite of a suboptimal alternative receiver compared to the adaptive MLSD receiver, the proposed adaptive RSSD receiver is able to reduce the complexity significantly and track the time-varying channel fast and reliably.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.683-689
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• 2004

The power and bandwidth efficient constant-envelope BPSK (CE-BPSK) modulation is proposed. The CE-BPSK signal is realized specifying the phase transition characteristics for the conventional low pass filtered BPSK signal. Since the CE-BPSK signal has constant envelope and modified waveform, the CE-BPSK signal has better power and bandwidth efficiency compared to the conventional BPSK signal while the CE-BPSK signal is backward compatible to the conventional BPSK signal. It is also shown that the bit error rate performance of the CE-BPSK signal is the same as that of the conventional BPSK signal.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.279-280
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• 2008

In order to improve the performance and simplify the structure of the conventional detectors in high density magnetic channels, a new equalizer based on bilinear recursive polynomial (BRP) models, which uses the previously estimated sequence, is proposed. The performance is compared with the conventional equalizers and the maximum likelihood sequence detection (MLSD) bound.