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25
Fading Channels: InformationTheoretic And Communications Aspects
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 1998
"... In this paper we review the most peculiar and interesting informationtheoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information ..."
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Cited by 289 (1 self)
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In this paper we review the most peculiar and interesting informationtheoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information theory of fading channels, by emphasizing capacity as the most important performance measure. Both singleuser and multiuser transmission are examined. Further, we describe how the structure of fading channels impacts code design, and finally overview equalization of fading multipath channels.
Multichannel Blind Deconvolution: Fir Matrix Algebra And Separation Of Multipath Mixtures
, 1996
"... A general tool for multichannel and multipath problems is given in FIR matrix algebra. With Finite Impulse Response (FIR) filters (or polynomials) assuming the role played by complex scalars in traditional matrix algebra, we adapt standard eigenvalue routines, factorizations, decompositions, and mat ..."
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Cited by 74 (0 self)
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A general tool for multichannel and multipath problems is given in FIR matrix algebra. With Finite Impulse Response (FIR) filters (or polynomials) assuming the role played by complex scalars in traditional matrix algebra, we adapt standard eigenvalue routines, factorizations, decompositions, and matrix algorithms for use in multichannel /multipath problems. Using abstract algebra/group theoretic concepts, information theoretic principles, and the Bussgang property, methods of single channel filtering and source separation of multipath mixtures are merged into a general FIR matrix framework. Techniques developed for equalization may be applied to source separation and vice versa. Potential applications of these results lie in neural networks with feedforward memory connections, wideband array processing, and in problems with a multiinput, multioutput network having channels between each source and sensor, such as source separation. Particular applications of FIR polynomial matrix alg...
Relationships Between the Constant Modulus and Wiener Receivers
 IEEE Transactions on Information Theory
, 1998
"... The Godard or the constant modulus algorithm (CMA) is an effective technique for blind receiver design in communications. However, due to the complexity of the Constant Modulus (CM) cost function, the performance of CM receivers has primarily been evaluated using simulations. Theoretical analysis is ..."
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Cited by 24 (4 self)
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The Godard or the constant modulus algorithm (CMA) is an effective technique for blind receiver design in communications. However, due to the complexity of the Constant Modulus (CM) cost function, the performance of CM receivers has primarily been evaluated using simulations. Theoretical analysis is typically based on either the noiseless case or approximations of the cost function. The following question, while resolvable numerically for a specific example, remains unanswered in a generic manner: In the presence of channel noise, where are the CM local minima and what are their meansquared errors (MSE)? In this paper, a geometrical approach is presented that relates CM to Wiener (or minimum MSE) receivers. Given the MSE and the intersymbol/user interference of a Wiener receiver, a sufficient condition is given for the existence of a CM local minimum in the neighborhood of the Wiener receiver. MSE bounds on CM receiver performance are derived and shown to be tight in simulations. The ...
Adaptive blind source separation and equalization for multipleinput/multipleoutput systems
 IEEE Transactions on Information Theory
"... Abstract—In this paper, we investigate adaptive blind source separation and equalization for multipleinput/multipleoutput (MIMO) systems. We first analyze the convergence of the constant modulus algorithm (CMA) used in MIMO systems (MIMOCMA). Our analysis reveals that the MIMOCMA equalizer is ab ..."
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Cited by 12 (2 self)
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Abstract—In this paper, we investigate adaptive blind source separation and equalization for multipleinput/multipleoutput (MIMO) systems. We first analyze the convergence of the constant modulus algorithm (CMA) used in MIMO systems (MIMOCMA). Our analysis reveals that the MIMOCMA equalizer is able to recover one of the input signals, remove the intersymbol interference (ISI), and suppress the other input signals. Furthermore, for the MIMO finite impulse response (FIR) systems satisfying certain conditions, the MIMOCMA FIR equalizers are able to perfectly recover one of the system inputs regardless of the initial settings. We then propose a novel algorithm for blind source separation and equalization for MIMO systems. Our theoretical analysis proves that the new blind algorithm is able to recover all system inputs simultaneously regardless of the initial settings. Finally, computer simulation examples are presented to confirm our analysis and illustrate the effectiveness of blind source separation and equalization for MIMO systems. Index Terms—Blind equalization, convergence, multipleinput/ multipleoutput system, source separation. I.
Geometrical Characterizations of Constant Modulus Receivers
 IEEE TRANS. SIGNAL PROCESSING
, 1999
"... Convergence properties of the constant modulus (CM) and the ShalviWeinstein (SW) algorithms in the presence of noise remain largely unknown. A new geometrical approach to the analysis of constant modulus and ShalviWeinstein receivers is proposed by considering a special constrained optimization i ..."
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Cited by 11 (2 self)
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Convergence properties of the constant modulus (CM) and the ShalviWeinstein (SW) algorithms in the presence of noise remain largely unknown. A new geometrical approach to the analysis of constant modulus and ShalviWeinstein receivers is proposed by considering a special constrained optimization involving norms of the combined channelreceiver response. This approach provides a unified framework within which various blind and (nonblind) Wiener receivers can all be analyzed by circumscribing an ellipsoid by norm balls of different types. A necessary and sufficient condition for the equivalence among constant modulus, ShalviWeinstein, zero forcing, and Wiener receivers is obtained. Answers to open questions with regard to CM and SW receivers, including their locations and their relationship with Wiener receivers, are provided for the special orthogonal channel and the general twodimensional (2D) channelreceiver impulse response. It is also shown that in two dimensions, each CM or...
An Analysis of Constant Modulus Receivers
 IEEE Trans. on Signal Processing
, 1999
"... This paper investigates connections between (nonblind) Wiener receivers and blind receivers designed by minimizing the constant modulus (CM) cost. Applicable to both Tspaced and fractionally spaced FIR equalization, the main results include 1) a test for the existence of CM local minima near Wiener ..."
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Cited by 9 (3 self)
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This paper investigates connections between (nonblind) Wiener receivers and blind receivers designed by minimizing the constant modulus (CM) cost. Applicable to both Tspaced and fractionally spaced FIR equalization, the main results include 1) a test for the existence of CM local minima near Wiener receivers; 2) an analytical description of CM receivers in the neighborhood of Wiener receivers; 3) mean square error (MSE) bounds for CM receivers. When the channel matrix is invertible, we also show that the CM receiver is approximately colinear with the Wiener receiver and provide a quantitative measure of the size of neighborhoods that contain the CM receivers and the accuracy of the MSE bounds. Index TermsBlind equalization, CMA, MSE. I. INTRODUCTION B LIND equalization of intersymbol interference (ISI) in communication channels and blind separation of multiple users are promising signal processing techniques in certain communication system designs. One of the earliest blind ...
Blind Equalization By Direct Examination Of The Input Sequences
 IEEE Trans. Commun
, 1992
"... This paper presents a novel approach to blind equalization (deconvolution) , which is based on direct examination of possible input sequences. In contrast to many other approaches, it does not rely on a model of the approximative inverse of the channel dynamics. To start with, the blind equalization ..."
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Cited by 9 (1 self)
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This paper presents a novel approach to blind equalization (deconvolution) , which is based on direct examination of possible input sequences. In contrast to many other approaches, it does not rely on a model of the approximative inverse of the channel dynamics. To start with, the blind equalization identifiability problem for a noisefree finite impulse response channel model is investigated. A necessary condition for the input, which is algorithm independent, for blind deconvolution is derived. This condition is expressed in an information measure of the input sequence. A sufficient condition for identifiability is also inferred, which imposes a constraint on the true channel dynamics. The analysis motivates a recursive algorithm where all permissible input sequences are examined. The exact solution is guaranteed to be found as soon as it is possible. An upper bound on the computional complexity of the algorithm is given. This algorithm is then generalized to cope with timevarying in...
An Analysis of Constant Modulus Algorithm for Array Signal Processing
 Signal Processing
, 1999
"... The constant modulus (CM) cost function is analyzed for array signal processing. The analysis includes arbitrary source types. It is shown that CM receivers have the signal space property except in two special cases. Local minima of CM cost function are completely characterized for the noiseless cas ..."
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Cited by 8 (2 self)
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The constant modulus (CM) cost function is analyzed for array signal processing. The analysis includes arbitrary source types. It is shown that CM receivers have the signal space property except in two special cases. Local minima of CM cost function are completely characterized for the noiseless case. In the presence of measurement noise, the existence of CM local minima in the neighborhood of Wiener receivers is established, and their mean squared error (MSE) performance, output power, estimation bias and residual interference are evaluated. Numerical examples are presented to demonstrate the e#ects of signal statistics on the locations of CM local minima. # 1999 Published by Elsevier Science B.V. All rights reserved.
Static and dynamic convergence behavior of adaptive blind equalizers
 IEEE Trans. Signal Processing
, 1996
"... AbstractThis paper presents a theoretical analysis of the static and dynamic convergence behavior for a general class of adaptive blind equalizers. We first study the properties of prediction error functions of blind equalization algorithms, and then, we use these properties to analyze the static a ..."
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Cited by 8 (1 self)
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AbstractThis paper presents a theoretical analysis of the static and dynamic convergence behavior for a general class of adaptive blind equalizers. We first study the properties of prediction error functions of blind equalization algorithms, and then, we use these properties to analyze the static and dynamic convergence behavior based on the independence assumption. We prove in this paper that with a small step size, the ensemble average of equalizer coefficients will converge to the minimum of the cost function near the channel inverse. However, the convergence is not consistent. The correlation matrix of equalizer coefficients at equilibrium is determined by a Lyapunov equation. According to our analysis results, for a given channel and stepsize, there is an optimal length for an equalizer to minimize the intersymbol interference. This result implies that a longerlength blind equalizer does not necessarily outperform a shorter one, which is contrary to what is conventionally conjectured. The theoretical analysis results are confirmed by computer simulations.
Performance Analysis of Blind Carrier Phase Estimators for General QAM Constellations
, 2001
"... Largo quadrature amplitude modulation (QAM) constellations are currently used in throughput efficient high speed communication applications such as digital TV. For such largo signal constellations, carrier phase synchronization is a crucial problem because for efficiency reasons the carrier acquisit ..."
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Cited by 7 (1 self)
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Largo quadrature amplitude modulation (QAM) constellations are currently used in throughput efficient high speed communication applications such as digital TV. For such largo signal constellations, carrier phase synchronization is a crucial problem because for efficiency reasons the carrier acquisition must often be performed blindly, without the use of training or pilot sequences. The goal of the present paper is to provide thorough performance analysis of the blind carrier phase estimaters that have boon proposed in the literature and to assess their relative merits.