• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.1
• /
• pp.19-26
• /
• 2013

This paper deals with the performance comparison of blind adaptive equalization algorithm, the MMA and S-MMA, that is used for compensation of the amplitude and phase distortion simultaneously which occurs in the time dispersive channel. The present CMA algorithm is possible to compensates the amplitude only, but not in phase, so it needs to the another additional circuit for compensating the phase. In order to overcoming the abovemensioned shorthand, the improved cost function is applied to the MMA algorithm. In MMA algorithm, the error is consists of the dispersion constant only, but in S-MMA, the error is consists of the dispersion constant considering the output of decision device (sliced symbol) in order to updating the tap coefficients. By using the two kind error signal, the adaptive equalization algorithm has different performance. In this paper, we compare to the adaptive equalization algorithm performance by using the recovered constellation, residual isi, MD (Maximum Distortion) and SER as a index when the transmitting signal is 16 and 64-QAM and then passing through the same communication channel. As a result of simulation, the S-MMA can improving the Roburstness in SER performance compared to the MMA in the high order QAM signal.

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

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.39 no.6
• /
• pp.709-717
• /
• 2002

A new multi constant modulus algorithm (MCMA) for a blind decision feedback equalizer is proposed. In order to avoid the error propagation problem in the conventional DFE structure, Feed-Back Filter coefficients are updated only after Feed-Forward Filter coefficients are sufficiently converged to the steady state. Therefore, it has the problem of slow convergence speed characteristics. To overcome this drawback, the proposed MCMA algorithm uses not only new cost function considering the minimum distance between the received signal and the representative value containing the statistical characteristics of the transmitted signal, but also adaptive step-size according to the equalizer outputs to fast convergence speed of FBF. Simulations were carried out under the certified communication channel environment to evaluate a performance of the proposed equalizer. The simulation results show that the proposed equalizer has an improved convergence and SER performance compared with previous methods. The proposed techniques offer the possibility of practical equalization for cable modem and terrestrial HDTV broadcast (using 8-VSB or 64-QAM) applications.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.4A
• /
• pp.330-335
• /
• 2002

In the direct sequence code division multiple access system, the problem of multiple access interference due to multiple access is generated. A interference cancelling receiver is used to solve this problem. The conventional interference cancelling receiver is structure of successive interference canceller using antenna array. In this structure, the difference of between method I and method II depends on updating weight vector. In this paper, the adaptive blind CMA array interference cancelling receiver using cost function of constant modulus algorithms is proposed to update weight vector at conventional structure. The simulation compared the proposed interference cancelling receiver with two conventional interference cancelling receivers by signal to interference ratio and bit error rate curve under additive white Gaussian noise environment. The simulation results show that the proposed receiver has about the gain of SIR of 1.5[dB] more than method I which is conventional receiver at SIR curve, and about the gain of SIR of 0.5(dB) more than method II. In BER curve, the proposed IC receiver about the gain of SNR of 2[dB] more than method I and about the gain of SNR of 0.5[dB] more than method If, Thus, the proposed interference cancelling receiver has the higher performance than conventional interference cancelling receivers.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.19 no.5
• /
• pp.101-106
• /
• 2019

This paper propose the VSS-FC-MMA algorithm that is possible to improve the equalization performance based on varying step size to the FC-MMA adaptive equalization algorithm in order to reducing the intersymbol interference effect occurred in the nonconstant modulus signal transmission, and improved performance were confirmed. The FC-MMA is possible to improve the convergence speed, and degrades the steady state performance based on the fixed step size and modified dispersion constant considering the level number of signal symbol for obtain the error signal in adaptive equalization compared to MMA. The proposed VSS-FC-MMA uses varying step size and current FC-MMA possible to improve the steady state equalization performance, it was confirmed by computer simulation. For this, the signal recovery capabilities and residual isi, MSE, SER were applied for performance comparison index in the same channel and signal to noise ratio. As a result of computer simulation, the proposed VSS-FC-MMA improve the risidual value in steady state and SER performance than the FC-MMA, but has 1.7 times slow convergence time by using varying step size.

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

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.7B
• /
• pp.937-943
• /
• 2001

fast fading 채널 특성을 갖는 DS-CDMA 다중 사용자 환경에서 Normalized CMA(Constant Modulus Algorithm)와 Newton 방식을 이용한 CMA를 이용하여 빠른 수렴속도와 작은 평균 자승 오차(Mean Square Error)를 동시에 개선할 수 있는 등화 방법을 제안하였다. Normalized CMA는 Newton 방식을 이용한 CMA에 비해 작은 평균 자승오차를 갖지만 수렴속도가 느리다는 단점이 있다. 반면 Newton 방식을 이용한 CMA는 Normalized CMA에 비해 수렴속도는 빠르지만 큰 평균 자승 오차를 갖는다는 단점이 있다. 따라서 빠른 수렴 속도와 작은 평균 자승 오차를 동시에 얻기 위한 구조를 제안하였으며, 이 구조는 각각의 알고리즘을 사용하는 방법과는 달리 두 개의 알고리즘을 동시에 이용한다. 모의 실험 결과, 제안한 기법이 Normalized CMA보다 약 320번, Newton 방식을 이용한 CMA보다는 170번 정도 빠른 수렴 속도를 나타냈으며, 동시에 수렴시의 평균 자승 오차는 Newton 방식을 이용한 CMA보다 약 0.6dB, Normalized CMA보다 약 0.4dB 정도 낮은 수치를 나타내는 것을 확인할 수 있었다.

• Journal of information and communication convergence engineering
• /
• v.8 no.2
• /
• pp.155-158
• /
• 2010

In this article, we proposed a new interference canceller using the adaptive algorithm. We designed constant modulus algorithm-correlation normailized least mean square (CMA-CNLMS) for wireless system. This structure is normalized LMS algorithm using correlation between the desired and input signal for cancelling the interference signals in the wideband code division multiple access (WCDMA) system. We showed that the proposed algorithm could improve the Mean Square Error (MSE) performance of LMS algorithm. MATLAB (Matrix Laboratory) is employed to analyze the proposed algorithm and to compare it with the experimental results. The MSE value of the LMS with mu=0.0001 was measured as - 12.5 dB, and that of the proposed algorithm was -19.5 dB which showed an improvement of 7dB.

• Journal of Industrial Technology
• /
• v.21 no.B
• /
• pp.99-105
• /
• 2001

In this paper, the selective normalized constant modulus algorithm(SNCMA) is applied to a fractionally spaced equalizer. The fractionally spaced equalizer is insensitive to the sampling timing because it processes received signals with the sampling rate larger than the symbol rate. The SNCMA improves the convergence rate by using the large step size for the most outer covering symbol belonging to the trust-level. This blind equalizer exhibits a fast start-up convergence rate as well as a reduced steady-state residual error compared to the fractionally spaced blind equalizer and the T-spaced blind equalizer using conventional blind algorithms.

• Journal of the Optical Society of Korea
• /
• v.15 no.3
• /
• pp.232-236
• /
• 2011

We analyze the linear equalizers used in optically amplified on-off-keyed (OOK) systems to combat chromatic dispersion (CD) and polarization mode dispersion (PMD), and we derive the mathematical minimum mean squared error (MMSE) performance of these equalizers. Currently, the MMSE linear equalizer for optical OOK systems is obtained by simulations using adaptive approaches such as least mean squared (LMS) or constant modulus algorithm (CMA), but no theoretical studies on the optimal solutions for these equalizers have been performed. We model the optical OOK systems as square-law nonlinear channels and compute the MMSE equalizer coefficients directly from the estimated optical channel, signal power, and optical noise variance. The accuracy of the calculated MMSE equalizer coefficients and MMSE performance has been verified by simulations using adaptive algorithms.