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11
Blind Beamforming for Non Gaussian Signals
 IEE ProceedingsF
, 1993
"... This paper considers an application of blind identification to beamforming. The key point is to use estimates of directional vectors rather than resorting to their hypothesized value. By using estimates of the directional vectors obtained via blind identification i.e. without knowing the arrray mani ..."
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Cited by 494 (31 self)
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This paper considers an application of blind identification to beamforming. The key point is to use estimates of directional vectors rather than resorting to their hypothesized value. By using estimates of the directional vectors obtained via blind identification i.e. without knowing the arrray manifold, beamforming is made robust with respect to array deformations, distortion of the wave front, pointing errors, etc ... so that neither array calibration nor physical modeling are necessary. Rather surprisingly, `blind beamformers' may outperform `informed beamformers' in a plausible range of parameters, even when the array is perfectly known to the informed beamformer. The key assumption blind identification relies on is the statistical independence of the sources, which we exploit using fourthorder cumulants. A computationally efficient technique is presented for the blind estimation of directional vectors, based on joint diagonalization of 4thorder cumulant matrices
A Simple Scheme For Adapting TimeFrequency Representations
, 1994
"... Signaldependent timefrequency representations, by adapting their functional form to fit the signal being analyzed, offer many performance advantages over conventional representations. In this paper, we propose a simple, efficient technique for continuously adapting timefrequency representations o ..."
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Cited by 14 (3 self)
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Signaldependent timefrequency representations, by adapting their functional form to fit the signal being analyzed, offer many performance advantages over conventional representations. In this paper, we propose a simple, efficient technique for continuously adapting timefrequency representations over time. The procedure computes a shorttime quality measure of the representation for a range of values of a free parameter and estimates the optimal parameter value maximizing the quality measure via interpolation. Many representations, including the shorttime Fourier transform, the conekernel distribution, and the continuous wavelet transform, support adaptation, at a computational cost of only a few times that of the corresponding static representations. Sponsored by the National Science Foundation, Grant No. MIP 9012747, the Joint Services Electronics Program, Grant No. N0001490J1270, and the Sound Group of the Computerbased Education Research Laboratory at the University of ...
MinimumEntropy Blind Acquisition/Equalization for Uplink DSCDMA
 Allerton Conference
, 1998
"... : In this paper, we consider blind estimation of linear chipspaced receivers for the demodulation of a particular shortcode DSCDMA mobile user under multipath propagation and in the absence of timing information. We propose a family of schemes for blind acquisition and equalization based on Donoh ..."
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Cited by 6 (2 self)
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: In this paper, we consider blind estimation of linear chipspaced receivers for the demodulation of a particular shortcode DSCDMA mobile user under multipath propagation and in the absence of timing information. We propose a family of schemes for blind acquisition and equalization based on Donoho's Minimum Entropy principle and propose a specific algorithm that uses the second and fourthorder moments of a prewhitened chiprate received signal. The proposed algorithm can be considered a nearfar resistant initialization procedure for, and application of, the Constant Modulus Algorithm (CMA) to DSCDMA. 1 Introduction Direct sequence code division multiple access (DSCDMA) systems have received considerable attention as a flexible means of communication between multiple mobile users and centralized base stations. Since CDMA users share the same time and frequency resources, demodulation of a particular user is principally concerned with suppression of interference from other user...
Effects Of Source Distributions And Correlation On Fractionally Spaced Blind Constant Modulus Algorithm Equalizers
, 1995
"... Simplicial Complex: By an abstract simplicial complex with vertices in a set V , we mean a family of finite subsets of V satisfying the condition that K is hereditary, i. e. every subset of any set in K is also in K. Subcomplex Let K and L be any two abstract simplicial complexes with vertices V an ..."
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Cited by 6 (0 self)
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Simplicial Complex: By an abstract simplicial complex with vertices in a set V , we mean a family of finite subsets of V satisfying the condition that K is hereditary, i. e. every subset of any set in K is also in K. Subcomplex Let K and L be any two abstract simplicial complexes with vertices V and W respectively. If L ae K, then L is said to be a subcomplex of K. Topological Realization Let K be an arbitrarily given abstract simplicial complex. We will construct a space P = jKj called the topological realization as follows. For each finite set F 2 K, consider the simplex oe F defined in the previous section. These simplexes foe F jF 2 Kg (without the identification introduced in studying their faces) are by definition disjoint topological spaces. Form their topological sum S = S(K) = X F2K oe F : Then S is clearly a metrizable space containing every simplex oe F as an open and closed subspace. Introduce a relation ¸ in S as follows. Let f 2 oe F and g 2 oe G be any two points in ...
Canonical Piecewise Linear Network for Nonlinear Filtering and Its Application to Blind Equalization
 SIGNAL PROCESS
"... Canonical piecewise linear structures provide a desirable compromise between the approximation ability of nonlinear models and the efficiency and theoretical accessibility of the linear domain, and they reduce the parameter storage requirement of piecewise linear models considerably by employing a g ..."
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Cited by 3 (0 self)
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Canonical piecewise linear structures provide a desirable compromise between the approximation ability of nonlinear models and the efficiency and theoretical accessibility of the linear domain, and they reduce the parameter storage requirement of piecewise linear models considerably by employing a global linear representation. We first study the representation and approximation ability of CPL network and show that we can always construct a partition for which a CPL representation exists, and that we can approximate any given continuous nonlinear mapping with a CPL network. We then present application of CPL network to blind equalization, show the ability of CPL equalizer to achieve blind equalization of a nonlinear channel, specifically, we show that if the distribution of the equalizer output is the same as that of the input to the channel, then the channel and equalizer combination is identity except for a sign and a delay factor. We also present experimental results to show the succ...
Adaptive Blind MultiChannel Equalization for Multiple Signals Separation
"... This paper investigates adaptive blind equalization for multipleinput and multipleoutput (MIMO) channels and its application to blind separation of multiple signals received by antenna arrays in communication systems. The performance analysis is presented for the CMA equalizer used in MIMO channel ..."
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Cited by 2 (1 self)
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This paper investigates adaptive blind equalization for multipleinput and multipleoutput (MIMO) channels and its application to blind separation of multiple signals received by antenna arrays in communication systems. The performance analysis is presented for the CMA equalizer used in MIMO channels. Our analysis results indicate that double infinitelength MIMOCMA equalizer can recover one of input signals, remove the intersymbol interference (ISI), and suppress the rest signals. In particular, for the MIMO FIR channels satisfying certain conditions, the MIMOCMA FIR equalizer is able to remove the ISI and cochannel interference regardless of the initial setting of the blind equalizer. To recover all input signals simultaneously, a novel MIMO channel blind equalization algorithm is developed in this paper. The global convergence of the new algorithm for MIMO channels is proved. Hence, the new blind equalization algorithm for MIMO channels can be applied to separate and equalize the...
Fast Blind Adaptive Algorithms for Equalization and Diversity Reception in Wireless Communications using Antenna Arrays
"... : To combat the multipath and timevariant fading of wireless communication channels, antenna arrays are usually used to improve the quality and increase the capacity of communication service. This paper investigates the fast blind adaptive algorithms for the equalization and diversity combining in ..."
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Cited by 1 (1 self)
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: To combat the multipath and timevariant fading of wireless communication channels, antenna arrays are usually used to improve the quality and increase the capacity of communication service. This paper investigates the fast blind adaptive algorithms for the equalization and diversity combining in wireless communication systems using antenna arrays. Two secondorder statistics based algorithms, SOSA and MSOS, for equalization and diversity combining are proposed and their convergence in noiseless and noisy channels is analyzed. Since the proposed algorithms use only secondorder statistics or correlation of the channel outputs, they converge faster than the higherorder statistics based algorithms, which is also confirmed by computer simulation examples. Keywords: blind adaptive equalization, fractionallyspaced equalizer, diversity reception, antenna arrays. The work was supported in part by the NSF grants MIP9309506 and MIP9457397. y To whom all correspondence will be sent. Ye...
Highlights of Signal Processing for Communications
, 1999
"... This paper chronicles more than 40 years of evolution in the design of such modems. ..."
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This paper chronicles more than 40 years of evolution in the design of such modems.
Blind Source Separation: a Partial Joint Diagonalization (PAJOD) Approach
, 2003
"... Blind Separation of convolutive mixtures and Blind Equalization of MultipleInput MultipleOutput (MIMO) channels are two different ways of naming the same problem, which we address here. A novel MIMO optimization criterion, subsequently presented in this paper, consists of a Partial Approximate Joi ..."
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Blind Separation of convolutive mixtures and Blind Equalization of MultipleInput MultipleOutput (MIMO) channels are two different ways of naming the same problem, which we address here. A novel MIMO optimization criterion, subsequently presented in this paper, consists of a Partial Approximate Joint Diagonalization (PAJOD) of several matrices, containing some values of output cumulant multicorrelations. A numerical algorithm is then devised, which works blockwise, and sweeps all the output pairs.