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Combination of Kalman filter and constant modulus algorithm with variable stepsize for the equalisation of fast-fading channels

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ELECTRONICS LETTERS 1998年第18期34卷 1718-1719页

作者： Pora, W Chambers, JA constantinides, AG Univ London Imperial Coll Sci Technol & Med Dept Elect Engn Signal Proc & Digital Syst Sect London SW7 2BT England

In fast-fading channels, the constant modulus algorithm (CMA) is unable to properly track the rime-variations because the magnitude of the received signal changes too rapidly. The Kalman filter (KF), however, works well in time-varying channels but needs a training sequence to operate. Therefore, a combined CMA and KF algorithm is proposed in order to utilise the advantages of both algorithms. The associated step sizes of the CMA and the KF algorithm are also varied in accordance with the magnitude of the output. Simulations are presented to demonstrate the potential of the combination.

关键词： Mobile radio systems time-variations magnitude Radiowave propagation equalisers equalisation step sizes constant modulus algorithm training sequence fading variable stepsize Kalman filters Kalman filter fast-fading channels telecommunication channels mobile communication

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Increasing the speed of convergence of the constant modulus algorithm for blind channel equalization

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第6期50卷 872-876页

作者： Nelatury, SR Rao, SS Villanova Univ Dept Elect & Comp Engn Villanova PA 19085 USA

The constant modulus algorithm (CMA) is an excellent technique for blind channel equalization. Recently signed error version of CMA (SE-CMA) and dithered signed error version (DSE-CMA,) have been proposed which afford overall computational efficiency. We propose three different error functions for faster convergence. This would be essential for communication systems, which cannot afford a high startup delay or for systems, where the channel's impulse response is rapidly fluctuating. One of these algorithms relies on the idea of a variable step size, which increases the rate of convergence.

关键词： blind equalization constant modulus algorithm error function speed of convergence

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constant modulus algorithm for multiuser detection

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CHINESE JOURNAL OF ELECTRONICS 2000年第2期9卷 163-165页

作者： Wang, Y Zhao, JP Wu, WL Beijing Univ Posts & Telecommun Beijing 100876 Peoples R China

constant modulus algorithm (CMA) for blind multiuser detection is proposed in [3]. However, the first type of stationary points in [3] is not correct. A general expression for the solutions is given in this paper, which shows there are many undesired stationary points. Therefore, methods that guarantee CMA to converge to the desired point are needed. We present approximate conditions that set initialization in the lock region. Simulation shows that CMA with variable step size has quicker convergence speed than MOE-RLS, while obtaining better performance.

关键词： Code-Division Multiple-Access multiuser detection constant modulus algorithm

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Multiuser interference suppression using block Shanno constant modulus algorithm

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2000年第5期48卷 1503-1506页

作者： Jani, UG Dowling, EM Golden, RM Wang, ZF Univ Texas Erik Jonsson Sch Engn & Comp Sci Richardson TX 75083 USA

In this correspondence, we extend the results from Wang and Dowling to provide a low-cost and high performance blind adaptive interference suppression scheme for CDMA systems. Simulation results confirm that the proposed algorithm outperforms several existing algorithms, even under the most severe cases of near-far and multipath conditions.

关键词： adaptive filters blind equalization CDMA conjugate gradient algorithms constant modulus algorithm interference suppression multiuser detection wireless

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A fast constant modulus algorithm for blind equalization

A fast constant modulus algorithm for blind equalization

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34th Asilomar Conference on Signals, Systems, and Computers

作者： Nelatury, SR Rao, SS Villanova Univ Dept Elect & Comp Engn Villanova PA 19085 USA

ISBN: (纸本)0780365143

The constant modulus (CM) criterion coupled with a gradient search helps in the design of fractionally spaced equalizers. Effective implementation of CIM algorithm requires proper choice of the scale factor mu called the step size and initialization of equalizer coefficients. Experience reveals that these two determine the convergence rate and final misadjustment. Recently Brown et al proposed a computationally efficient algorithm, which is a signed error version of CMA. This paper proposes yet another variation of the same and reports faster convergence. The idea is to use a variable step size, which increases the convergence rare.

关键词： blind equalization constant modulus algorithm error function speed of convergence

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Tracking analysis of the constant modulus algorithm

Tracking analysis of the constant modulus algorithm

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33rd IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Silva, Magno T. M. Nascimento, Vitor H. Univ Sao Paulo Dept Elect Syst Engn Escola Politecn BR-05508900 Sao Paulo Brazil

ISBN: (纸本)9781424414833

Recently, we proposed a model for the steady-state estimation error of real-valued constant-modulus-based algorithms as a function of the a priori error and of a term that measures the variability in the modulus of the transmitted signal. In this paper, we extend this model to complex-valued data and use it in conjunction with the feedback analysis method to obtain an analytical expression for the steady-state excess mean-square error (EMSE) of the constant modulus algorithm (CMA). Such expression is more accurate for larger step-sizes than the previous ones in the literature, as confirmed by the good agreement between analytical and simulation results. Furthermore, from the EMSE expression, we obtain an estimate for the CMA step-size interval to ensure its convergence and stability, when it is initialized sufficiently close to the zero-forcing solution.

关键词： adaptive filters blind equalization energy conservation tracking analysis constant modulus algorithm

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Avoiding divergence in the constant modulus algorithm

Avoiding divergence in the Constant Modulus Algorithm

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33rd IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Miranda, Maria D. Silva, Magno T. M. Nascimento, Vitor H. Univ Sao Paulo Escola Politecn BR-05508900 Sao Paulo Brazil

ISBN: (纸本)9781424414833

One of the most popular algorithms for blind equalization is the constant modulus algorithm (CMA), due to its simplicity and low computational cost. However, if the step-size is not properly chosen or if the initialization is distant from the optimal solution, CMA can diverge or converge to undesirable local minima. In order to avoid divergence, we propose a dual-mode algorithm, which works as CMA with a time-variant step-size, but rejects non-consistent estimates of the transmitted signal. We present a deterministic analysis of the stability of the new algorithm for scalar filters. In the vector case, the good performance of the new algorithm is confirmed through numerical simulations.

关键词： adaptive filters blind equalization constant modulus algorithm dual-mode algorithms stability

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A vector constant modulus algorithm for shaped constellation equalization

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IEEE SIGNAL PROCESSING LETTERS 1998年第4期5卷 89-91页

作者： Yang, VY Jones, DL Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA

The constant modulus algorithm (CMA), a popular method for performing blind equalization, has the drawback of failing when the input data has a Gaussian distribution or a kurtosis larger than three, This means that source shaping (which is used to increase the shaping gain) can produce data unequalizable by CMA and other important blind equalization techniques. This paper proposes a simple extension of CMA that blindly equalizes many types of shaped constellations, including those shaped by shell mapping.

关键词： blind equalization constant modulus algorithm shaped constellation shell mapping

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PAPR reduction using constant modulus algorithm and IDCT in MIMO-OFDM Networks 3

PAPR reduction using Constant Modulus Algorithm and IDCT in ...

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3rd International Conference on Eco-Friendly Computing and Communication Systems (ICECCS)

作者： Sujatha, S. Dananjayan, P. Pondicherry Engn Coll Dept ECE Pondicherry India

ISBN: (纸本)9781479970025

In MIMO-OFDM networks, the main drawback includes the large peak-to-average power ratio (PAPR) of the transmitter's output signal on different antennas. In order to overcome this issue, PAPR is reduced using IDCT in this paper. In this technique, Inverse Discrete Cosine Transform (IDCT) along with constant modulus algorithm is used to reduce the PAPR in MIMO-OFDM networks. It involves two methods, first the time domain signal from the Resource Block is combined linearly using pre-coding weights which is transparent to the receiver side. Then the precoding weights are modified to decrease the modulus variations of the resulting signal, which leads to the reduction of PAPR in MIMO OFDM. By simulation results, it is observed that the proposed technique reduces PAPR.

关键词： MIMO-OFDM PAPR constant modulus algorithm IDCT

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Strategy to transition from the constant modulus algorithm to a decision feedback blind equalizer

Strategy to transition from the constant modulus algorithm t...

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IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： McGinty, N Def Sci & Technol Org Commun Div Kingston ACT Australia

ISBN: (纸本)0780374029

The constant modulus algorithm (CMA) is commonly used for first stage blind equalization applications. CMA's main advantage is that it will open the eye based on the received signal only. Decision directed (DD) equalization is often used as it provides a lower mean square error (MSE) in the equalized signal. Obvious from its name, DD equalization requires estimates of the transmitted symbols in order to adapt the equalizer - the eye must be open. This paper considers an elegant method to transition between CMA and DD equalization (in a decision feedback equalizer structure). A conventional "brute force" approach to perform the transition is to determine the filter coefficients for the DD equalizer through a MMSE design criterion based on the inverse CMA filter coefficients. This may cause a large procession delay at the point of transition between filter types and requires significant computations. The algorithm in this paper is low complexity and does not require a large processing delay when transitioning from CMA to DD LMS.

关键词： blind equalisers decision feedback equalisers least mean squares methods delays computational complexity constant modulus algorithm decision feedback blind equalizer CMA decision directed equalization mean square error MSE DD equalization decision feedback equalizer brute force approach filter coefficients MMSE design inverse CMA filter coefficients low complexity algorithm processing delay multipath propagation intersymbol interference ISI

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