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34
Joint MAP registration and highresolution image estimation using a sequence of undersampled images
 IEEE Transactions on Image Processing
, 1997
"... Abstract — In many imaging systems, the detector array is not sufficiently dense to adequately sample the scene with the desired field of view. This is particularly true for many infrared focal plane arrays. Thus, the resulting images may be severely aliased. This paper examines a technique for esti ..."
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Cited by 208 (2 self)
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Abstract — In many imaging systems, the detector array is not sufficiently dense to adequately sample the scene with the desired field of view. This is particularly true for many infrared focal plane arrays. Thus, the resulting images may be severely aliased. This paper examines a technique for estimating a highresolution image, with reduced aliasing, from a sequence of undersampled frames. Several approaches to this problem have been investigated previously. However, in this paper a maximum a posteriori (MAP) framework for jointly estimating image registration parameters and the highresolution image is presented. Several previous approaches have relied on knowing the registration parameters a priori or have utilized registration techniques not specifically designed to treat severely aliased images. In the proposed method, the registration parameters are iteratively updated along with the highresolution image in a cyclic coordinatedescent optimization procedure. Experimental results are provided to illustrate the performance of the proposed MAP algorithm using both visible and infrared images. Quantitative error analysis is provided and several images are shown for subjective evaluation. Index Terms—Aliased, high resolution, image registration, image sequence, MAP estimation. I.
The Watermark Copy Attack
, 2000
"... Research in digital watermarking has progressed along two paths. While new watermarking technologies are being developed, some researchers are also investigating different ways of attacking digital watermarks. Common attacks to watermarks usually aim to destroy the embedded watermark or to impair it ..."
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Cited by 70 (10 self)
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Research in digital watermarking has progressed along two paths. While new watermarking technologies are being developed, some researchers are also investigating different ways of attacking digital watermarks. Common attacks to watermarks usually aim to destroy the embedded watermark or to impair its detection. In this paper we propose a conceptually new attack for digitally watermarked images. The proposed attack does not destroy an embedded watermark, but copies it from one image to a different image. Although this new attack does not destroy a watermark or impair its detection, it creates new challenges, especially when watermarks are used for copyright protection and identification. The process of copying the watermark requires neither algorithmic knowledge of the watermarking technology nor the watermarking key. The attack is based on an estimation of the embedded watermark in the spatial domain through a filtering process. The estimate of the watermark is then adapted and inserted in...
Multiresolution histograms and their use for recognition
 IEEE Transactions on Pattern Analysis and Machine Intelligence
, 2004
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Performance analysis of SIRbased dual selection diversity over correlated Nakagamim fading channels
 IEEE Trans. Veh. Technol
, 2003
"... diversity is an efficient technique to mitigate fading and cochannel interference in wireless communications systems. In this paper, an approach to the performance analysis of dual SIRbased selection diversity over correlated Nakagami fading channels with arbitrary parameters is presented. Useful ..."
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Cited by 11 (0 self)
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diversity is an efficient technique to mitigate fading and cochannel interference in wireless communications systems. In this paper, an approach to the performance analysis of dual SIRbased selection diversity over correlated Nakagami fading channels with arbitrary parameters is presented. Useful formulae for the outage probability, the average output SIR, and the average error probability for coherent, noncoherent, and multilevel modulation schemes are derived. The main contribution of this paper is that, for the first time, the proposed analysis is carried out assuming correlated Nakagami fading with arbitrary parameters for both the desired signals and the cochannel interferers, which is the real scenario in practical dual selection diversity systems with insufficient antenna spacing. It is shown that the general results presented in the paper reduce to the specific ones for the independent fading case, previously published. Numerical and simulation results are also presented to show the effects of various parameters as the fading severity, input SIR unbalance, and level of correlation to the system’s performance. Index Terms—Cochannel interference, correlated fading, diversity systems, Nakagami fading, Rayleigh fading, selection combining. I.
A unified superresolution approach for optical and Synthetic Aperture Radar images
, 1998
"... It is easy to feel overwhelmed by the amount of time and effort required of the Ph.D. degree. These feelings were, often times, too familiar. With patience, persistence and the help of many individuals, my doctoral studies provided for a very memorable and fruitful four years. I would like to thank ..."
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Cited by 9 (2 self)
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It is easy to feel overwhelmed by the amount of time and effort required of the Ph.D. degree. These feelings were, often times, too familiar. With patience, persistence and the help of many individuals, my doctoral studies provided for a very memorable and fruitful four years. I would like to thank these people for their help and friendship throughout my studies. First, I wish to acknowledge and thank Dr. Jose C. Principe for his role as advisor and mentor throughout my doctoral studies. Our discussions and exchanging of ideas were fundamental in the shaping of this work. I would also like to thank him for providing a stimulating work environment in CNEL through which my engineering horizons were expanded. Thank you to my supervisory committee members: Dr. John M. M. Anderson, Dr. A. Antonio Arroyo, Dr. John G. Harris and Dr. Janice C. Honeyman – your interest and suggestions were appreciated. Dr. John G. Harris deserves additional thanks, particularly for our fruitful discussions and his suggestion to me to work on optical images. I would like to thank Dr. Leslie Novak of MIT Lincoln Laboratory for providing me the opportunity to work with him during the summer of 1997. It was a truly
Iterative decoding of codes over complex number for impulsive noise channels
 IEEE Trans. Inf. Theory
, 2003
"... Abstract—We discuss the decoding of errorcorrecting block codes over complex numbers for the transmission over impulsive noise channels. The encoder multiplies a vector of complex information symbols resulting from a modulation scheme, e.g., quadrature amplitude modulation (QAM), with a unitary gen ..."
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Cited by 9 (0 self)
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Abstract—We discuss the decoding of errorcorrecting block codes over complex numbers for the transmission over impulsive noise channels. The encoder multiplies a vector of complex information symbols resulting from a modulation scheme, e.g., quadrature amplitude modulation (QAM), with a unitary generator matrix. Choosing the inverse Fourier transform as, the encoding procedure is similar to orthogonal frequencydivision multiplex (OFDM) modulation. The maximum a posteriori (MAP) receiver is analyzed and a suboptimum decoder based on the turbo decoding principle is derived. Simulation results show the excellent performance of the iterative decoder. Index Terms—Complex number codes, diversity, fading channel, impulsive noise, orthogonal frequencydivision multiplex (OFDM), rotation, turbo decoding. I.
Performance Improvement of Spread Spectrum Based Image Watermarking Schemes Through Mary Modulation
 Proc. of the Workshop on Information Hiding, LNCS1768
, 1999
"... . In spread spectrum communication the use of Mary modulation is a popular extension to binary signaling usually resulting in a signicant performance improvement. Furthermore it was shown that for increasing M and for certain schemes Mary modulation works at the channel capacity. In this work ..."
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Cited by 8 (0 self)
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. In spread spectrum communication the use of Mary modulation is a popular extension to binary signaling usually resulting in a signicant performance improvement. Furthermore it was shown that for increasing M and for certain schemes Mary modulation works at the channel capacity. In this work we investigated on how to use Mary modulation in the context of spatial spread spectrum based watermarking schemes. The performance of Mary watermarking schemes is theoretically analyzed and the results veried through empirical test. We show that in general Mary modulation based on the biorthogonal extension of the Hadamard matrix results in a signicant performance improvement for values of M > 4. Furthermore we show that the performance improvement does not decrease under noise like distortion such as lossy JPEG compression. 1 Introduction Digital watermarking, the art of hiding information in multimedia data, has become a very popular research area for the past 7 years. The...
Kalman’ Shrinkage for WaveletBased Despeckling of
 SAR Images,” International Journal of Intelligent Systems and Technologies, Volume 1, Number
, 2006
"... Abstract—In this paper, a new probability density function (pdf) is proposed to model the statistics of wavelet coefficients, and a simple Kalman’s filter is derived from the new pdf using Bayesian estimation theory. Specifically, we decompose the speckled image into wavelet subbands, we apply the K ..."
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Cited by 6 (3 self)
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Abstract—In this paper, a new probability density function (pdf) is proposed to model the statistics of wavelet coefficients, and a simple Kalman’s filter is derived from the new pdf using Bayesian estimation theory. Specifically, we decompose the speckled image into wavelet subbands, we apply the Kalman’s filter to the high subbands, and reconstruct a despeckled image from the modified detail coefficients. Experimental results demonstrate that our method compares favorably to several other despeckling methods on test synthetic aperture radar (SAR) images. Keywords—Kalman’s filter, shrinkage, speckle, wavelets. I.
Kernels and multiple windows for estimation of the WignerVille spectrum of gaussian locally stationary processes
 IEEE Trans. on Signal Processing
, 2007
"... Abstract—This paper treats estimation of the WignerVille spectrum (WVS) of Gaussian continuoustime stochastic processes using Cohen’s class of timefrequency representations of random signals. We study the minimum mean square error estimation kernel for locally stationary processes in Silverman’s ..."
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Cited by 6 (0 self)
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Abstract—This paper treats estimation of the WignerVille spectrum (WVS) of Gaussian continuoustime stochastic processes using Cohen’s class of timefrequency representations of random signals. We study the minimum mean square error estimation kernel for locally stationary processes in Silverman’s sense, and two modifications where we first allow chirp multiplication and then allow nonnegative linear combinations of covariances of the first kind. We also treat the equivalent multitaper estimation formulation and the associated problem of eigenvalueeigenfunction decomposition of a certain Hermitian function. For a certain family of locally stationary processes which parametrizes the transition from stationarity to nonstationarity, the optimal windows are approximately dilated Hermite functions. We determine the optimal coefficients and the dilation factor for these functions as a function of the process family parameter. Index Terms—Locally stationary circular symmetric processes, multitaper spectral estimation, optimal estimation, timefrequency analysis, WignerVille spectrum (WVS). I.
Performance and Optimized Design of SpaceTime Codes For MIMO Wireless Systems with Imperfect Channel Estimates
, 2004
"... Multipleantennas constitute an effective mean to achieve spatial diversity in emerging bandwidthefficient multiple input multipleoutput (MIMO) wireless systems. Until now, most contributions in this area are focused on the two limit cases of fully coherent and fully incoherent decoding, which, i ..."
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Cited by 5 (4 self)
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Multipleantennas constitute an effective mean to achieve spatial diversity in emerging bandwidthefficient multiple input multipleoutput (MIMO) wireless systems. Until now, most contributions in this area are focused on the two limit cases of fully coherent and fully incoherent decoding, which, in turn, occur when perfect channel estimates and no channel estimates are available at the receiver. However, very accurate channel estimates typically demand long training sequences that reduces spectral efficiency. Therefore, testing capabilities of multipleantenna systems with partially coherent decoding may be appealing for improving powerversusbandwidth tradeoff. In this contribution, we focus on the optimized design and performance evaluations of multipleantenna blockcoded systems with partiallycoherent maximumlikelihood (ML) decoding. After considering emerging fourthgeneration WLANs (4GWLANs) as a possible application scenario, we present new performance bounds and optimized design criteria together with a new family of robust spacetime unitary block codes that "selfmatch" to channelestimation errors. We name these codes "self matching." Index TermsBandwidthversuspower tradeoff, multipleantenna, MIMO systems, partially coherent decoding, performance bounds, "selfmatching" spacetime blockcodes, 4GWLAN.