• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.179-190
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• 1998

One of the most important topics of recent years is that a multimedia technology such as wireless ATM has been introduced in radio systems for video, voice and data transmission. A major problem in such systems is the occurrence of errors due to multipath fading or interference. To combat this problem, forward error correction (FEC) coding is commonly used as a means of eliminating these errors. This paper has analyzed theoretically the effect of fading to design effective wireless ATM system. The BER, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. Also, simulations of BER and CLR have been carried out and compared with the above theoretical results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.648-653
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• 2011

In this paper, coordinated space division multiple access(SDMA) technology is proposed to mitigate inter-cell interference by using partial channel state information in cooperative wireless communications system with limited feedback. Each AT selects an optimal cluster transmission mode and sends it back to a cluster scheduler, and at the cluster scheduler, ATs are scheduled within a AT group with the identical cluster transmission mode, and the optimal transmission mode and the corresponding scheduled ATs are determined to maximize scheduling priority. Also, in order to enhance multiuser diversity gain, an extended transmission feedback method is proposed to feed back multiple preferred cluster transmission modes at each AT. It is shown that the proposed coordinated SDMA scheme outperforms existing non-coordinated SDMA schemes in terms of the average system throughput.

• Journal of The Korean Society of Clinical Toxicology
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• v.13 no.1
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• pp.1-10
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• 2015

Purpose: The purpose of this study was to evaluate the usefulness of intravenous lipid emulsion as well as adverse events in acute poisoning patients. Methods: Literature was accessed through PubMed, EMBASE, Cochrane library, Web of science, and KoreaMed. All forms of literatures relevant to human use of intravenous lipid emulsion for acute poisoning were included. Cases reports or letters without description of clinical outcomes for each case were excluded. The literature search was conducted by two investigators in March, 2015, with publication language restricted to English and Korean. The effect, onset time, and adverse event of lipid emulsion and final outcome of each case were analyzed. Results: Eighty-one published articles were included, excluding articles whose title and abstract were not relevant to this study. No articles were classified as high level of evidence. Sixty-eight case reports were identified, consisting of 25 local anesthetics and 43 other drugs, such as tricyclic antidepressants and calcium channel blockers. Although most cases described significant clinical improvements, some of them showed no beneficial effect or worsening of clinical course. Several adverse events including hyperamylasemia and laboratory interference were reported. Conclusion: Although there were many case reports illustrating successful use of lipid for various drug poisonings, the effect cannot be estimated due to significant possibility of publication bias. Therefore, lipids might be considered in severe hemodynamic instability resulting from lipophilic drug poisoning, however further studies should follow to establish the use of lipid as the standard of care.

• Journal of Biomedical Engineering Research
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• v.18 no.4
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• pp.389-396
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• 1997

Several types of electrical artifact seen on electroencephalogram( EEG) records are described. Those are the EOG and the PVC roller pump noise, and so on. An adaptive digital filtering of the electroencephalogram( EEG) is a successful way of suppressing mains interference, but it affects some of the frequency components of the signal, whore artifacts may not be acceptable in some cafes of automatic EEG processing. Thus we studied the method for cancelling these artifacts. This proposed method does not use the reference channel, and is realized by connecting the linear predictor and the fixed FIR filter for the EOG artifact, and by cascading the linear predictor and the noise canceller for the pump artifact. The simulation results illustrate the performances of the proposed method in terms of the capability of interferences suppression. In the results we obtained about 20 dB noise reduction.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.107-112
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• 2016

This paper proposes the improving the equalization performance using the variable step size in the S-MMA (Sliced-Multi Modulus Algorithm) equalization algorithm in order to minimize the effect of intersymbol interference which occurs at the nonlinear transfer function of communication channel. The S-MMA were showned for the improving the steady state equalization performance and misadjustment compared to the MMA present algorithm, this two algorithm has a limitation of performance improvement due to the adapting the fixed step size according to the error signal amplitude. In order to solving the abovemensioned problem, the proposed algorithm was adopting the variable step size proportional to the error signal amplitude and the computer simulation was performed for showing the performance improving. As a result of simulation, the proposed VSS S-MMA algorithm has more superior equalization performance compared to the present S-MMA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.109-114
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• 2015

This paper relates with the eualization performance of Adaptive Varying-MMA (AV-MMA) in order to the minimization of intersymbol interference that is occurs in the nonlinear communication channel. In order to obtain the error signal in the tap coefficient updating process of adaptive equalization algorithm, the present MMA uses the constant modulus. But in AV-MMA, the adaptively varying modulus are used according to the equalizer output, it is possible to reduce the error signal and possbile to improving the overall equalization performance. In order to improved equalization performance of the AV-MMA in the 64-QAM signal, the present MMA performance were compared. For this, the output signal constellation of equalizer, residual isi, maximum distortion, MSE and SER curves are applied. As a result of computer simulation, the AV-MMA has more better performance in the every performance index than MMA, and the SER performance shows that it has more robustness in high SNR environmnet compared to MMA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.85-90
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• 2018

This paper compares the adaptive eualization performance of CR-MMA (Constellation Reduction-MMA) and CR-MMA (Constellation Matching-MMA) in order to minimization of intersymbol interference that is occur in channel for 2-dimensional QAM signal. For obtain the error signal in order to updating the tap coefficient of conventional adaptive equalization algorithm MMA, the CR-MMA converts the constellation reduction concept of high order 2-dimensional QAM nonconstant modulus signal to constant modulus signal and the CM-MMA use the constellation matchine error concept in order to force the matching the $2^{nd}$ and $4^{th}$ cumulant of equalizer output and transmitted signal constellation. By applying the different method for getting the error signal, these algorithm are possible to obtain the improved equalization performance compared to the conventional MMA algorithm, the improved performance of CR-MMA and CM-MMA were compared by computer simulation in this paper. As a result of simulation, the CM-MMA has more better performance in the equalizer internal performance than CR-MMA, but not in equalizer external performance as in SER.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.135-143
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• 1998

Several equalizers are applied to the DVD-ROM(Digital Versatile Disc-Read Only Memory) system. Because imperfect writing process may cause nonlinear distortion in the reply signal, neural equalizers which have strong nonlinear mapping capability are applied to the system to compensate the nonlinear distortion. Experimental results to verify that the combination of decision-feedback type equalizers and modulation code is formidable are also given. The experimental results shwo that the SNR gain of the neural equalizers over the conventional equalizers becomes much as the nonlinearity in the channel increases. Furthermore, the decision-feedback type equalizers outperform the equalizers which have no decision-feedback in eliminating ISI(Intersymbol Interference) of random data sequence but there is no performance gain of the decision-feedback type equalizers over the equalizers without decision-feedback when these are applied to compensate the ISI of modulation-encoded data sequence.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.378-390
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• 2001

In this paper, it is analyzed that the error performance of a Multi-Carrier DS-CDMA system in a single cell with multipath Rician fading and multiple access interference (MAI) and the error performance of the system is compared with that of a Sing1e-Carrier DS-CDMA system. Moreover, the convolutional coding techniques with code rate of 1/2, 1/3, and 1/4 are adopted in order to improve the error performance degraded by the multipath fading and MAI and performance improvement through the coding techniques is analyzed. As a result, it is shown that the number of users in each system can be determined by the number of branches of the rake receiver in a Single-Carrier DS-CDMA system and the number of carriers in a Multi-Carrier DS-CDMA system. Furthermore, the convolutional coding should be chosen with considering the trade-off between coding gain and a power limitation in a Multi-Carrier DS-CDMA system. In case of increasing the number of carriers, the processing gain is decreased but the error performance is improved through the effect of frequency diversity and the system can be possibility implemented due to the low chip rate.

• 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.