• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.107-113
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• 2011

This paper is concerned with the CR-CMA (Coordinate Reduction-Constant Modulus Algorithm) adaptive equalization algorithm using the coordinate reduction in order to improve the convergence characteristic and residual intersymbol interference which are used as the performance index for an adaptive equalizer. The equalizer is used to reduce the distortion caused by the intersymbol interference on the wireless and the wired band-limited channel that connect the transmitting system and receiving system. The CMA is widely known as the representative algorithm for equalization. In order to transmitting the mass information with a high speed through the channels, a fast convergence speed in the equalizer performance that is able to minimize overhead needed for equalization is acquired. In this paper, we introduce the new cost function to reduce the constellation of received signal at the input stage of a equalizer. It reduce the error at the steady equalization state. By the computer simulation, we confirmed that the proposed CR-CMA algorithm has the faster convergence speed and the smaller residual intersymbole interference than the conventional CMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5C
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• pp.601-610
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• 2004

In this paper, the performance of an adaptive array antenna using Constant Modulus Algorithm (CMA) based on the signal structure for the IMT-2000 3GPP specification reverse link of an asynchronous direct sequence code division multiple access (DS-CDMA) system are evaluated. In addition, the performance is compared with the array antenna using Least Mean Square (LMS) based on the training signal. The simulation parameters such as the number of multipath, mu10pa1h intensity profiles between path, spreading gain and multiuser etc., are considered in the Monte Carlo simulation. Simulation results demonstrate an adaptive array antenna using CMA may give more capacity gain than the amy antenna using LMS in the case of multipath fading channel.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.153-158
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• 2012

This paper deals with the performance comparison of adaptive equalization algorithm, CMA and MMA, that is used for the minimization of the distortion and noise effect in the communication channel at receiver.. We confirmed the application possibilities of the point to point or point to multipoint digital transmission technologies by analyzing the performance of MMA which is changing the error function of CMA that is the possible algorithm of fast equalization by relatively simple arithmatic computation compared to the other method. In CMA algorithm, we need the PLL for the amplitude compensation only and not possible to phase compensation inherently. But in MMA algorithm, we confired that the amplitude and phase of received signal can be compensated by computer simulation. For the comparison of algorithm, we used the essential performance index, convergence characteristics and residual isi. The result of performance comparison of algorithms, the MMA has good in convergence characteristic and the CMA has good in residual isi that is used for the amplitude compensation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10B
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• pp.2004-2010
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• 1999

This paper presents the blind multiuser detector using the constant modulus algorithm(CMA) to solve the near-far problem in DS-CDMA systems. The convergence property of the detector is compared with the conventional MOE(minimum output energy) detector by means of SIR(signal-to-interference ratio). The MOE detector needs both the spreading code of the users and the timing information, while proposed methods needs only information about the spreading code of users Simulation results show that the CMA-based detector is superior to the conventional blind MOE multiuser detector. For this, the BER performance was tested using different values of SNR and near-far ratio. The SIR is also investigated for different number of users in AWGN and Rayleigh fading channels. We have observed that the proposed blind multiuser detector performs better than conventional MOE multiuser detector.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6B
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• pp.1074-1081
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• 2000

In this paper, in order to speed up the convergence process and improve the steady mean square error simultaneously, we propose the Stop-and-Go Dual Mode Modified Constant Modulus Algorithm(SAG DM MCMA) for adaptive blind channel equalization of high order QAM. The proposed algorithm is a hybrid scheme of the Modified CMA that treat error signals with real and imaginary components of the equalizer output, the concept of dual mode CMA, and Stop-and-Go algorithm. As a result it can prevent blind equalization from converging to incorrect direction and simultaneously operates reliably for tap weight adaptation. We demonstrate via simulation that the proposed algorithm achieves lower steady state mean square error and residual ISI than the conventional algorithms under high order QAM signals and severe channel environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12C
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• pp.753-758
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• 2011

The constant modulus algorithm (CMA) widely used in blind equalization applications minimizes the averaged power of constant modulus error (CME) defined as the difference between an instant output power and a constant modulus. In this paper, a decision feedback version of the linear blind algorithm based on maximization of the zero-error probability for CME is proposed. The Gaussian kernel of the maximum zero-error criterion is analyzed to have the property to cut out excessive CMEs that may be induced from severely distorted channel characteristics. Decision feedback approach to the maximum zero-error criterion for CME is developed based on the characteristic that the Gaussian kernel suppresses the outliers and this prevents error propagation to some extent. Compared to the linear algorithm based on maximum zero-error probability for CME in the simulation of blind equalization environments, the proposed decision feedback version has superior performance enhancement particularly in cases of severe channel distortions.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.47-50
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• 1999

Adaptive channel equalization accomplished without resorting to a training sequence is known as blind equalization. The Constant Modulus Algorithm(CMA) and Modified CMA(MCMA) are widely referenced algorithms for blind equalization of a QAM system. This paper proposes a hybrid scheme of CMA and MCMA with Carrier Recovery that is robust for high level QAM with low steady state tracking error.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.152-159
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• 2005

For high-speed data communication in band-limited channels, main of the bit error are fading and ISI(Inter-Symbol Interference). The common way of dealing with ISI is using equalization in the receiver. In this thesis, channel adaptive equalizer which uses Fuzzy Stochastic Gradient(FSG) and Constant Modulus Algorithm(CMA) is nonlinear equalizer, or Blind equalizer, that works directly on the signals with no training sequences required. This equalizer employs Takagi-Sugeno's fuzzy model that uses the FSG algorithm, to automatically regulate the step size of the descent gradient vector, combining fast convergence rate and low mean square error(MSE), and the CMA which is a special case of Godard's algorithm, to having multiple dispersion constants($R_p$).

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.601-604
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• 2000

본 논문에서는 MCMA(modified constant modulus algorithm) 블라인드 등화 알고리듬을 고속 데이터 통신에 적합한 FSE(fractionally spaced equalize.)에 적용시킨 FS-MCMA를 제안하였다. 제안한 FS-MCMA는 위상 복원문제와 같은 CMA의 단점을 보완하기 위하여 M-ary QAM 신호의 경우 다중레벨로 등화하는 기존의 MCMA 이용하였고 주기 T의 간격으로 수신되는 심볼을 2배 이상으로 샘플링하는 기법, 즉 FSE를 도입하여 높은 테이터율을 요구하는 멀티미디어 통신에 적합하도록 구성하였다. 컴퓨터 모의 실험을 시행한 결과를 residual ISI 측면에서 기준을 정하고 비교하였는데 4dB정도의 성능향상을 보였으며, 또한 기존의 CMA보다 154dB 정도의 성능향상을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.996-1007
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• 1996

In this paper, a blind adaptation method for a decision feedback equalizer (DFE) is proposed to deal with nominimum phase channels. This equalizer is composed of a linear transversal filter and a prediction error filter which are trained separately using constant modulus and decision feedback prediction algorithms, respectively, during the learnign time. The proposed algorithm guaranetees the DFE to converge to a suboptimal point on the condition that a linear transversal of the proposed scheme is illustrated and the performance is compared with conventional blind equlization algorithms.