• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.97-102
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• 2020

This paper relates with the Hybrid-SE-MMA (Signed-Error MMA) that is possible to improving the equalization performance by using the adaptive modulus and adaptive step size in SE-MMA adaptive equalizer for the minimizing the intersymbol interference. The equalizer tap coefficient is updatted use the error signal in MMA algorithm for adaptive equalizer. But the sign of error signal is used for the simplification of arithmetic operation in SE-MMA algorithm in order to updating the coefficient. By this simplification, we get the fast convergence speed and the reduce the algorithm processing speed, but not in the equalization performance. In this paper, it is possible to improve the equalization performance by computer simulation applying the adaptive modulus to the SE-MMA which is proposional to the power of equalizer output signal. In order to compare the improved equalization performance compared to the present SE-MMA, the recovered signal constellation that is the output of the equalizer, residual isi, MD(maximum distortion), MSE and the SER perfomance that means the robustness to the external noise were used. As a result of computer simulation, the Hybrid-SE-MMA improve equalization performance in the residual isi and MD, MSE, SER than the SE-MMA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.251-254
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• 2002

In the design of mobile wireless communication system, the location of BTS(Base Transciver Stations), RSC(Base Station Controllers), and MSC(Mobile Switching Center) is one of the most important parameters. Designing wireless communication system, the cost of equipment is need to be made low by combining various, complex parameters. We can solve this problem by combinatorial optimization algorithm, such as Simulated Annealing, Tabu Search, Genetic Algorithm, Random Walk Algorithm that have been extensively used for global optimization. This paper shows the four kind of algorithms which are applied to the location optimization of BTS, BSC, and MSC in designing mobile communication system and then we compare with these algorithms. And also we analyze the experimental results and shows the optimization process of these algorithms. As a the channel of a CDMA system is shared among several users, the receivers face the problem of multiple-access interference (MAI). Also, the multipath scenario leads to intersymbol interference (ISI). Both components are undesired, but unlike the additive noise process, which is usually completely unpredictable, their space-time structure helps to estimate and remove them.

• 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 B
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• v.31B no.11
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• pp.27-35
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• 1994

In this paper, a modified version of PRML is discussed to reduce nonlinearity in digital high-density storage devices. We propose a PRML with a nonlinear compensator which can reduce nonlinear interaction between the stored flux regions on the storage channel, and apply it to recording channels with three different densities. By comparing its performance with the existing PRML through computer simulation, we confirm that the nonlinear intersymbol interference increasing with high-density recording channels can be reduced effectively by the PRML with a nonlinear compensator.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.3
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• pp.18-29
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• 1993

In single mode fiber optic transmission systems(FOT's) operated at high modulation rates over long fiber spans, chromatic dispersion can produce distortion in the demodulated waveforms, resulting in intersymbol interference(ISI) in the received signal and a reduction of transmission system performance. In this paper, chromatic dispersion limitations for intensity modulation and direct detection(IM-DD) systems are studied by considering the effect of phase modulation to amplitude modulation (PM-AM) conversion noise. Laser phase noise conversion to amplitude noise due to fiber chromatic dispersion is analyzed by deriving the noise power spectral density. We first derive the noise power spectral density of the laser phase noise to intensity noise conver- sion. Next, also evaluate the system power penalty and the transmitter laser linewidth required to avoid PM-AM conversion noise penalties in long-haul nonregenerative transmission system using an external modulator and optical amplifiers. For such system with optical amplifiers, transmission sys- tem length is limited due to fiber chromatic dispersion, even if an ideal external modulator is used.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2390-2395
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• 2011

For intersymbol interference (ISI) compensation from communication channels with multi-path fading and impulsive noise, a decision feedback equalizer algorithm that minimizes Euclidean distance of error probability is proposed. The Euclidean distance of error probability is defined as the quadratic distance between the probability error signal and Dirac-delta function. By minimizing the distance with respect to equalizer weight based on decision feedback structures, the proposed decision feedback algorithm has shown to have significant effect of residual ISI cancellation on severe multipath channels as well as robustness against impulsive noise.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.223-230
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• 2002

In this paper, we induced that the noise powers and bit error rate of direct detection receiver taking account of ISI (intersymbol interference) in the 2,000 km optical transmission system. And we evaluated the sensitivity in the vrious bit rate system. We verified that the proposed calculation method is applicable to the exact optical system. And we confirmed that the signal distortion due to both chromatic dispersion and nonlinear effects compensated by using of MSSI (Mid-Span Spectral Inversion) method, and yet the sensitivity of a higher bit rate system is reduced, because of the increase of ISI and then the decrease of the average receiving power, compared with a the lower bit rate system.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1132-1136
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• 2005

In this paper, adaptive equalizer receiver for a turbo code direct sequence code division multiple access (DSCDMA) by using least mean square (LMS) adaptive algorithm is presented. The proposed adaptive equalizer is using soft output of decision feedback adaptive equalizer (DFE) to examines the output of the equalizer and the Log- maximum a posteriori (Log-MAP) algorithm for the turbo decoding process of the system. The objective of the proposed equalizer is to minimize the bit error rate (BER) of the data due to the disturbances of noise and intersymbol interference (ISI)phenomenon on the channel of the DS-CDMA digital communication system. The computer program simulation results shown that the proposed soft output decision feedback adaptive equalizer provides a good BER than the others one such as conventional adaptive equalizer, infinite impulse response adaptive equalizer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8C
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• pp.516-521
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• 2011

In this paper, a nonlinear algorithm that maximizes zero-error probability (MZEP) with decision feedback (DF) is proposed to counteract both of severely distorted multi-path fading effect and impulsive noise. The proposed MZEP-DF algorithm has shown the immunity to impulsive noise and the ability of the feedback filter section to cancel the remaining intersymbol interference as well. Compared with the linear MZEP algorithm, it yields above 10 dB enhancement of steady state MSE performance in severely distorted multipath fading channels with impulse noise where the least mean square (LMS) algorithm does not converge below -3dB of MSE.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.109-114
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• 2016

This paper relates with the performance improvement of CCA (Compact Constellation Algorithm) equalization algorithm by adding the adaptive step size control in order to the minimization of intersymbol interference and additive noise effects that is occurs in the channel for digital radio transmissionl. In general, the fixed step size was used in order to adaptation in equalizer algorithm. But in proposed algorithm, the variable step size were adapted that is proposional to the nonlinear function of error signal for equalization. In order to show the improved equalizatation performance, the output signal constellation of equalizer, residual isi, maximum distortion, MSE and SER were used, then it were compared with the present CCA algorithm. As a result of computer simulation, the adaptive step size CCA has more better performance in the every performance index compared to the fixed step size CCA after in the steay state.