• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.67-72
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• 2019

This paper evaluates the performance of CCA (Compact Constellation Algorithm) adaptive equalization algorithm by varying the step size for minimization of the distortion effect in the communication channel. The CCA combines the conventional DDA and RCA algorithm, it uses the constant modulus of the transmission signal and the considering the output of decision device by the power of compact slice weighting value in order to improving the initial convergence characteristics and the equalization noise by misadjustment in the steady state. In this process, the compact slice weight values were fixed, and the performance of CCA adaptive equalization algorithm was evaluated by the varing the three values of step size for adaptation. As a result of computer simulation, it shows that the smaller step size gives slow convergence speed, but gives excellent performance after at steady state. Especially in SER performance, the small step size gives more robustness that large values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8A
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• pp.1291-1297
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• 2001

본 논문에서는 DS-CDMA 환경의 다중 사용자 검출에서 문제시되는 다중 접속 간섭을 제거시켜주기 위해 사용되는 간섭 제거기에 대하여 소개한다. 기존의 간섭 제거 기술 중 병렬형 간섭 제거기는 장치적으로 복잡하고, 순차적 간섭 제거기는 지연 시간이 길다는 단점을 가지고 이다. 무엇보다도, 적응형 간섭 제거기는 수렴하기 위하여 많은 반복수가 필요하다. 우리는 이러한 간섭 제거기들의 성능을 개선시키기 위해서 CMA(Constant Modulus Algorithm)을 이용한 적응형 간섭 제거기에 간섭 제거 기법을 적용시킨 새로운 간섭 제거기를 제안한다. 제안된 간섭 제거기는 적응 필터 처리후 간섭 제거 기법을 적용시키기 때문에 동일한 BER(Bit Error Rate)을 얻고자 할 때 기존의 적응형 간섭 제거기에 비해 수렴을 위한 반복수를 줄여 준다. 그리고, 적응 필터를 사용함으로써 기존의 비선형 간섭 제거기에 비해 하드웨어적인 복잡도를 줄일 수 있는 효과가 있다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.33-36
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• 2000

DS-CDMA (direct sequence-code division multiple access) 시스템에서 여러 사용자가 동일 주파수 대역을 공유함으로써 다중 접속 간섭 (multiple access interference; MAI)이 발생하고 시스템의 성능을 크게 제한한다. 이러한 다중 접속 간섭을 제거하여 전송 신호의 질을 높이고 용량을 증대시키는 중요한 신호 처리 기술 가운데 하나가 적응 간섭 억제 기술이다. 적응 간섭 억제 기술 가운데 CMA (constant modulus algorithm) 기반의 블라인드 적응 간섭 억제기는 훈련수열을 필요로 하지 않고 빠른 수렴을 통하여 간섭을 효과적으로 제거할 수 있으나, 다중 경로 환경에서 심벌간 간섭 (intersymbol interference; ISI)이 증대되어 기존의 적응 수신기보다 악화된 성능을 보인다. 본 논문에서는 CMA를 기반으로 훈련 수열 없이 빠른 수렴을 하며 MAI와 ISI를 효과적으로 제거하기 위한 다이버시티 결합기 구조의 적응 간섭 억제기를 제한한다. 다중 경로 페이딩 채널 환경에서 기존의 블라인드 적응간섭 억제기와의 성능 비교 결과, 제안된 방식이 다중경로에 의한 ISI의 영향을 효과적으로 제거하여 우수한 성능을 얻을 수 있음을 확인하였다.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.399-405
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• 2010

Blind equalization techniques have been used in broadcast and multipoint communications. In this paper, two criteria of minimizing Euclidian distance between two probability density functions (PDFs) for adaptive blind equalizers are presented. For PDF calculation, Parzen window estimator is used. One criterion is to use a set of randomly generated desired symbols at the receiver so that PDF of the generated symbols matches that of the transmitted symbols. The second method is to use a set of Dirac delta functions in place of the PDF of the transmitted symbols. From the simulation results, the proposed methods significantly outperform the constant modulus algorithm in multipath channel environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.876-881
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• 2006

In this paper, we propose a complex-valued IIR filter for digital VSB signals based on CMA in order to efficiently mitigate multipath distortions, especially the leakage from the quadrature component. The proposed equalizer overcomes the drawback of the conventional real-valued IIR equalizers that it attempts to equalize Hilbert transform of quadrature component. We demonstrate via simulation that the proposed complex IIR filter successfully mitigates the leakages from the quadrature component, while the conventional real IIR filter requires a longer IIR filter to achieve the same performance. We present cost function analysis for a simple two-tap case showing that the proposed IIR equalizer with CMA for VSB signals has a global minimum at the desired location.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1274-1282
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• 1996

This paper deals with an inverse modeling of nonminimum phase communication channel utilizing the HOS (High Order Statistics) of the received signal. After the communication channel is separated into the minimum phase and maximum phase components, the inverse modeling is performed independently. The performance superiority is confirmed by monte-carlo computer simulation in comparison with the traditional CMA (Constant Modulus Algorithm) method. By utilizing the proposed algorithm employing the HOS of the received signal, the inverse frequency characteristics of the channel can be obtained withoug transmitted signal in digital communication. This algorithm is required in preprocessing or postprocessing in order to remove the channel effect, and effective in the self adaptive equalizer which can minimize the bit error rate or symbol error rate in the recovry of received signal.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.96-103
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• 2000

This research is a new design method, which will be presented as a basic concept for a more efficient minimum weight design of grillages, as an attempt to describe true collapse mechanism in as overall search as possible. It serves as introduction to the numerical technique of Linear Programming(LP) and Automatic Modified Direct Plastic Frame Analysis(AMDPFA). Attention is directed to both analysis and design, and emphasis is placed on the physical significance of Systematic Searching Techniques(SST) involved. In weight minimum grillages design, the parameterisation study in optimum beam configuration which was carried out over the range of beam sections for a given plastic section modulus likely to occur in structures by suing an adaptive stochastic optimisation technique, Genetic Algorithms.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.4
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.1
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• pp.95-100
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• 2020

This paper related with the performance evaluation of mSE-MMA (modified Signed Error-Multi Modulus Algorithm) adaptive equalization algorithm which is possible to reduce the distortion that is occurs in nonlinear communication channel like as additive noise, intersymbol interference and fading. The SE-MMA algorithm are emerged in order to reducing the computational load compared to the presently MMA algorithm, it has the degraded equalization performance by this. In order to improve the performance degradation of SE-MMA, the mSE-MMA controls the step size according to the existence of arbitrary radius circle of equalizer output is centered at transmitted symbol point. The performance of proposed mSE-MMA algorithm were compared to present SE-MMA using the same channel and noise environment by computer simulation. For this, the recoverd signal constellation which is the output of equalizer, residual isi and MD (Maximum Distortion), MSE learning curve which is represents the convergence performance and SER which is represents the roburstness of noise were used as performance index. As a result of simulation, the mSE-MMA has more superior to the SE-MMA in every performance index, and was confirmed that mSE-MMA has roburstness to the noise in the SER performance than SE-MMA especially.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.29-35
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• 2006

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.