• Title/Summary/Keyword: modified decision-directed

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Performance Improvement of MCMA Equalizer with Parallel Structure (병렬 구조를 갖는 MCMA 등화기의 성능 개선)

  • Yoon, Jae-Sun;Lim, Seung-Gag
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.11 no.5
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    • pp.27-33
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    • 2011
  • In digital communication system that the Modified Constant Modulus Algorithm (MCMA) reduced the use of the adaptive equalization algorithm to combat the Inter-symbol Interference (ISI). MCMA is relatively brief operation. The major point of MCMA that it only achieves moderate convergence rate and steady state mean square error (MSE). In this paper suggest, MCMA equalization improve the performance with parallel structure. It combines Modified Constant Modulus Algorithm(MCMA) and Modified Decision Directed(MDD) algorithm. By exploiting the inherent structural relationship between the 4-QAM signal's coordinates and 16-QAM signal's coordinates, another style of cost function for Modified Constant Modulus Algorithm(MCMA) is defined and If it happen to offset of received signals and MCMA is poor performance in order to overcome this because the paper combines apply for MCMA and MDD(Modified Decision Direct) algorithm. By computer simulation, we confirmed that the proposed PMCMA-MDD algorithm has the fater convergence rate and steady mean square error than the conventional MCMA.

A Modified Decision-Directed LMS Algorithm (수정된 DD LMS 알고리즘)

  • Oh, Kil Nam
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.7
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    • pp.3-8
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    • 2016
  • We propose a modified form of the decision-directed least mean square (DD LMS) algorithm that is widely used in the optimization of self-adaptive equalizers, and show the modified version greatly improves the initial convergence properties of the conventional algorithm. Existing DD LMS regards the difference between a equalizer output and a quantization value for it as an error, and achieves an optimization of the equalizer based on minimizing the mean squared error cost function for the equalizer coefficients. This error generating method is useful for binary signal or a single-level signals, however, in the case of multi-level signals, it is not effective in the initialization of the equalizer. The modified DD LMS solves this problem by modifying the error generation. We verified the usefulness and performance of the modified DD LMS through experiments with multi-level signals under distortions due to intersymbol interference and additive noise.

A Study on the performance Improvement of the Adaptive Blind Equalizer Using the Soft Decision-Directed Stop-and-Go Algorithm (연판정지향 Stop-and-Go 알고리즘을 이용한 적응 블라인드 등화기의 성능 향상에 관한 연구)

  • 정영화
    • The Journal of Information Technology
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    • v.2 no.1
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    • pp.103-113
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    • 1999
  • In this paper, we propose th soft decision-directed sto-and-go algorithm combining a concept of the stop-and-go algorithm with soft decision-directed algorithm. The proposed algorithm has an enhanced equalization performance according to using the more confidential error signal than two algorithms. By computer simulation, it is confirmed that the proposed algorithm has the performance superiority in terms of residual ISI and convergence speed compared with the adaptive blind equalization algorithm of CMA, Modified CMA(MCMA), Stop-and Go algorithm and simplified 50ft decision-directed algorithm.

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Performance Enhancement of Decision Directed SNR Estimation by Correction Scheme of SNR Estimation Error (결정지향 SNR 추정방식에서의 추정오차 보정기법을 통한 SNR 추정성능개선)

  • Kwak, Jae-Min
    • Journal of Advanced Navigation Technology
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    • v.16 no.6
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    • pp.982-987
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    • 2012
  • In this paper, the SNR estimation error of Decision Directed SNR estimation method in AWGN is investigated, which uses samples received in reference decision region. In communication system receiver, when SNR estimation scheme using error vectors between ideal sample points and received sample points of reference region is adopted, the samples contain incorrectly received samples due to AWGN. Consequently, the mean of estimated reference constellation point is shifted and Decision Directed SNR estimation is inaccurately performed. These effects are explained by modified probability density function and difference between actual SNR and estimated SNR is theoretically derived and quantatively analyzed. It is proved that SNR estimation error obtained through computer simulation is matched up with derived one, and SNR estimation performance is enhanced significantly by adopting suggested correction scheme.

A New Bussgang Blind Equalization Algorithm with Reduced Computational Complexity (계산 복잡도가 줄어든 새로운 Bussgang 자력 등화 알고리듬)

  • Kim, Seong-Min;Kim, Whan-Woo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.10
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    • pp.1012-1015
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    • 2011
  • The decision-directed blind equalization algorithm is often used due to its simplicity and good convergence property when the eye pattern is open. However, in a channel where the eye pattern is closed, the decision-directed algorithm is not guaranteed to converge. Hence, a modified Bussgang-type algorithm using a hyperbolic tangent function for zero-memory nonlinear(ZNL) function has been proposed and applied to avoid this problem by Filho et al. But application of this algorithm includes the calculation of hyperbolic tangent function and its derivative or a look-up table which may need a large amount of memory due to channel variations. To reduce the computational and/or hardware complexity of Filho's algorithm, in this paper, an improved method for the decision-directed algorithm is proposed. In the proposed scheme, the ZNL function and its derivative are respectively set to be the original signum function and a narrow rectangular pulse which is an approximation of Dirac delta function. It is shown that the proposed scheme, when it is combined with decision-directed algorithm, reduces the computational complexity drastically while it retains the convergence and steady-state performance of the Filho's algorithm.

Trellis Defection of Tamed FM with the DLMS and Convergence

  • Kang, Min-Goo;Lee, Yang-Won;Cho, Hyung-Rae;Kang, Sung-Chul
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.1 no.2
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    • pp.199-207
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    • 1997
  • The Maximum Likelihood Sequence Estimation scheme is modified to improve the error performance of the correlative coding in the Tamed FM. To remove intersymbol interference, the Decision Feedback Equalization scheme with the delayed LMS algorithm and the Viterbi algorithm(10-symbol delay) in the delayed adaptive equalization are proposed for the performance of decision-directed adaptive equalization under the High Frequency channels, and the condition of convergence is analyzed.

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A New Implementation of the LMS Algorithm as a Decision-directed Adaptive Equalizer with Decoding Delay

  • Ahn, Sang-Sik
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.1E
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    • pp.89-94
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    • 1996
  • This paper deals with the application of the LMS algorithm as a decision-directed adaptive equalizer in a communication receiver which also employs a sophisticated decoding scheme such as the Viterbi algorithm, in which the desired signal, hence the error, is not available until several symbol intervals later because of decoding delay. In such applications the implemented weight updating algorithm becomes DLMS and major penalty is reduced convergence speed. Therefore, every effort should by made to keep the delay as small as possible if it is not avoidable. In this paper we present a modified implementation in which the effects of the decoding delay can be avioded and perform some computer simulations to check the validity and the performance of the new implementation.

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Machine Layout Decision Algorithm for Cellular Formation Problem

  • Lee, Sang-Un
    • Journal of the Korea Society of Computer and Information
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    • v.21 no.4
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    • pp.47-54
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    • 2016
  • Cellular formation and layout problem has been known as a NP-hard problem. Because of the algorithm that can be solved exact solution within polynomial time has been unknown yet. This paper suggests a systematic method to be obtain of 2-degree partial directed path from the frequency of consecutive forward order. We apply the modified Kruskal algorithm of minimum spanning tree to be obtain the partial directed path. the proposed reverse constructive algorithm can be solved for this problem with O(mn) time complexity. This algorithm performs same as best known result of heuristic and metaheuristic methods for 4 experimental data.

Design of a High Speed QPSK/16-QAM Receiver Chip (고속 QPSK/16-QAM 수신기 칩 설계)

  • Park, Ki-Hyuk;Sunwoo, Myung-Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.4B
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    • pp.237-244
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    • 2003
  • This paper presents the design of a QPSK/16-QAM downstreams receiver chip. The proposed chip consists of a blind equalizer, a timing recovery block and a carrier recovery block. The blind equalizer uses a DFE sturucture using CMA(Constant Module Algorithm). The symbol timing recovery uses the modified parabolic interpolator. The decision-directed carrier recovery is used to remove the carrier frequency offset, phase offset and phase jitter. The implemented LMDS receiver can support four data rates, 10, 20, 30 and 40 Mbps and can accommodate the symbol rate up to 10 Mbaud. This symbol rate is faster than existing QAM receivers.

A Performance Evaluation of Blind Equalization Algorithma for a Variable Step-Size MSAG-GMMA (가변 스텝 크기 MSAG-GMMA 적응 블라인드 등화 알고리즘의 성능 평가)

  • Jeong, Young-Hwa
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.3
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    • pp.77-82
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    • 2018
  • This paper is concerned with the performance analysis of a modified stop-and-go generalized multi-modulus algorithm (MSAG-GMMA) adaptive blind equalization algorithm with variable step size. The proposed algorithm multiplies the fixed step size by the error signal of the decision-oriented algorithm in the equalization coefficient update equation, and changes the step size according to the error size. Also, the MSAG-GMMA having a fixed step size is operated so as to maintain a fast convergence speed from a certain threshold to a steady state by determining the error signal size of the decision-directed algorithm, and when the MSAG-GMMA to work To evaluate the performance of the proposed algorithm, we use the ensemble ISI, ensemble-averaged MSE, and equalized constellation obtained from the output of the equalizer as the performance index. Simulation results show that the proposed algorithm has faster convergence speeds than MMA, GMMA, and MSAG-GMMA and has a small residual error in steady state.