Periodically time varying (PTV) filters can offer significant performance gains over conventional filtering methods in DS-CDMA communications systems that are either multirate or corrupted by narrow band interference....
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Periodically time varying (PTV) filters can offer significant performance gains over conventional filtering methods in DS-CDMA communications systems that are either multirate or corrupted by narrow band interference. This paper develops a new blind adaptive PTV linear multiuser detector based on the frequency shift (FRESH) architecture. The blind adaptive algorithm is based on the linearly constrained constant modulus algorithm (LCCMA), but is modified for the FRESH architecture. The resulting stochastic gradient algorithm has significantly less computational complexity than the recently proposed recursive and cyclic subspace tracking algorithms, and can offer comparable performance. The robustness of the FRESH-LCCMA algorithm is ensured through a proof of convergence which is carried out in the paper.
The constant modulus algorithm (CMA) enjoys widespread popularity as methodsfor blind beamform-ing and equalization of communication signals, CMA is straightforward toimplement, robust, and computationally of moderate...
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The constant modulus algorithm (CMA) enjoys widespread popularity as methodsfor blind beamform-ing and equalization of communication signals, CMA is straightforward toimplement, robust, and computationally of moderate complexity. Furthermore, it is insensitive toarray imperfection. In an environment containing multiple constantmodulus signals, the signalextracted by CMA depends on the relative power of the incident signals. According previous works,the CMA is prone to capture the strongest constantmodulus (CM) signal at the output of the *** this paper, we show that the weak CM signal could be recovered by CMA_(1-2) and CMA_(2-1) whensetting special step-size. Simulation examples confirm our remarks.
A new mulfitarget constantmodulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constantmodulus alg...
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A new mulfitarget constantmodulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm （D-DDLSCMA）. In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.
A new non-linear adaptive filter called blind image deconvolution via dispersion minimization has recently been proposed for restoring noisy blurred images blindly. This is essentially a two-dimensional version of the...
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A new non-linear adaptive filter called blind image deconvolution via dispersion minimization has recently been proposed for restoring noisy blurred images blindly. This is essentially a two-dimensional version of the constant modulus algorithm that is well known in the field of blind equalization. The two-dimensional extension has been shown capable of reconstructing noisy blurred images using partial a priori information about the true image and the point spread function in a variety of situations by means of simulations. This paper analyses the behaviour of the algorithm by investigating the static properties of the cost function and the dynamic convergence of the parameter estimates. The theoretical results are supported with computer simulations. Copyright (c) 2006 John Wiley & Sons, Ltd.
In linear image restoration, the point spread function of the degrading system is assumed known even though this information is usually not available in real applications. As a result, both blur identification and ima...
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In linear image restoration, the point spread function of the degrading system is assumed known even though this information is usually not available in real applications. As a result, both blur identification and image restoration must be performed from the observed noisy blurred image. This paper presents a computationally simple iterative blind image deconvolution method which is based on non-linear adaptive filtering. The new method is applicable to minimum as well as mixed phase blurs. The noisy blurred image is assumed to be the output of a two-dimensional linear shift-invariant system with an unknown point spread function contaminated by an additive noise. The method passes the noisy blurred image through a two-dimensional finite impulse response adaptive filter whose parameters are updated by minimizing the dispersion. When convergence occurs, the adaptive filter provides an approximate inverse of the point spread function. Moreover, its output is an estimate of the unobserved true image. Experimental results are provided. (c) 2005 Elsevier Inc. All rights reserved.
The deconvolution of a filtered version of a zero-mean normalized independent and identically distributed (i.i.d.) signal (s(n))(n is an element of z) having a strictly negative Kurtosis gamma(2) = E[|s(n)|(4)] - 2(E[...
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The deconvolution of a filtered version of a zero-mean normalized independent and identically distributed (i.i.d.) signal (s(n))(n is an element of z) having a strictly negative Kurtosis gamma(2) = E[|s(n)|(4)] - 2(E[|s(n)|(2)])(2) - |E[s(n)(2)|(2)] is addressed. This correspondence focuses on the global minimizers of the Godard function. A well-known result states that these minimizers achieve deconvolution at least if the input signal shows the symmetry E[s(2)] = 0. When this constraint is relaxed, (s(n))(n is an element of Z) is said to be noncircular symmetric: It is shown that the minimizers achieve deconvolution if and only if 2|E [s(n)(2)]|(2) < -gamma(2)(s). If this condition is not met, the global minimizers are found to be finite-impulse-response filters with two taps.
We address the problem of signal separation using space-time blind decision feedback equalizer. Assuming correct decisions and absence of noise, the perfect equalization conditions are obtained. We present an extensio...
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ISBN:
(纸本)9781424436446
We address the problem of signal separation using space-time blind decision feedback equalizer. Assuming correct decisions and absence of noise, the perfect equalization conditions are obtained. We present an extension of the blind algorithm which avoids degenerated solutions in the single-input single output case. The proposed algorithm jointly adapts the feedforward and feedback filters of DFE, avoids degenerated solutions, and has capability of simultaneously recovering all sources.
In this paper, we investigate the impetus for a Rake receiver together with an equalizer for UWB communication systems and then develop a novel Rake combining equalizer which employs a blind adaptive algorithm to impr...
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ISBN:
(纸本)9781424401017
In this paper, we investigate the impetus for a Rake receiver together with an equalizer for UWB communication systems and then develop a novel Rake combining equalizer which employs a blind adaptive algorithm to improve the system performance by mitigating multi-path distortion and suppressing inter-symbol interference (ISI). Simulations have verified the usefulness of this structure in UWB communication systems.
In order to overcome the slow convergence rate and large state error of the CMA. a new dual-mode algorithm for multi-modulus blind equalization suitable for high-order QAM signals is proposed. This algorithm uses the ...
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In order to overcome the slow convergence rate and large state error of the CMA. a new dual-mode algorithm for multi-modulus blind equalization suitable for high-order QAM signals is proposed. This algorithm uses the CMA as the basal mode. And in the second mode the multi-modulusalgorithm is used. Furthermore, the two modes operate concurrently, and in the second mode the adaptation of the weight vector is based on the decision of the equalizer's output. The efficiency of the method is proved by computer simulations in underwater acoustic channels.
A new adaptive step-size constant modulus algorithm for direct-sequence code division multiple access receivers is presented for application in nonstationary channel conditions. The algorithm is derived upon the basis...
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A new adaptive step-size constant modulus algorithm for direct-sequence code division multiple access receivers is presented for application in nonstationary channel conditions. The algorithm is derived upon the basis of adapting the step-size to minimise the constantmodulus criterion and its convergence is verified analytically. Simulations show the superior performance of the proposed method over similar adaptive receivers and its robustness to different settings of the initial step-size. (C) 2002 Elsevier Science B.V. All rights reserved.
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