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Signal Reconstruction (signal + reconstruction)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Signal reconstruction in the presence of finite-rate measurements: finite-horizon control applications

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2010
Sridevi V. Sarma
Abstract In this paper, we study finite-length signal reconstruction over a finite-rate noiseless channel. We allow the class of signals to belong to a bounded ellipsoid and derive a universal lower bound on a worst-case reconstruction error. We then compute upper bounds on the error that arise from different coding schemes and under different causality assumptions. When the encoder and decoder are noncausal, we derive an upper bound that either achieves the universal lower bound or is comparable to it. When the decoder and encoder are both causal operators, we show that within a very broad class of causal coding schemes, memoryless coding prevails as optimal, imposing a hard limitation on reconstruction. Finally, we map our general reconstruction problem into two important control problems in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite-rate noiseless channel. The first problem is to minimize a finite-horizon weighted tracking error between the remote system output and a reference command. The second problem is to navigate the state of the remote system from a nonzero initial condition to as close to the origin as possible in finite-time. Our analysis enables us to quantify the tradeoff between time horizon and performance accuracy, which is not well studied in the area of control with limited information as most works address infinite-horizon control objectives (e.g. stability, disturbance rejection). Copyright © 2009 John Wiley & Sons, Ltd. [source]

Theoretical analysis of iterative signal reconstruction for impulsive noise mitigation in OFDM systems

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2010
Nikola Rozic
Abstract In this paper a theoretical analysis of the iterative signal reconstruction algorithm for impulsive noise mitigation in orthogonal frequency-division multiplexing (OFDM) systems is developed. The following main results are developed: first, analytical model for the total noise in the frequency domain, and second the model for the total noise probability density function (pdf) in the frequency domain, both defined for each step of the iterative reconstruction process. Finally, based on the pdf of the total noise, explicit expressions for BER in kth iteration are defined as well. The main intention of the paper is to present the approach to theoretical analysis of the iterative impulsive noise mitigation algorithm that has not yet been appeared in the literature, because the theoretical analysis of the noise pdf during iterations has been considered as too complex a problem. Analyses and analytical results presented in the paper are given for scenario with a fixed number of noise impulses per frame. However, this is not a handicap of the proposed approach, since all presented models can be used as building blocks for scenarios with other impulsive noise distributions including Bernoulli,Gaussian and Middleton's Class A. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Signal reconstruction in the presence of finite-rate measurements: finite-horizon control applications

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2010
Sridevi V. Sarma
Abstract In this paper, we study finite-length signal reconstruction over a finite-rate noiseless channel. We allow the class of signals to belong to a bounded ellipsoid and derive a universal lower bound on a worst-case reconstruction error. We then compute upper bounds on the error that arise from different coding schemes and under different causality assumptions. When the encoder and decoder are noncausal, we derive an upper bound that either achieves the universal lower bound or is comparable to it. When the decoder and encoder are both causal operators, we show that within a very broad class of causal coding schemes, memoryless coding prevails as optimal, imposing a hard limitation on reconstruction. Finally, we map our general reconstruction problem into two important control problems in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite-rate noiseless channel. The first problem is to minimize a finite-horizon weighted tracking error between the remote system output and a reference command. The second problem is to navigate the state of the remote system from a nonzero initial condition to as close to the origin as possible in finite-time. Our analysis enables us to quantify the tradeoff between time horizon and performance accuracy, which is not well studied in the area of control with limited information as most works address infinite-horizon control objectives (e.g. stability, disturbance rejection). Copyright © 2009 John Wiley & Sons, Ltd. [source]

Multichannel mapping of fetal magnetocardiogram in an unshielded hospital setting

PRENATAL DIAGNOSIS, Issue 5 2005
Donatella Brisinda
Abstract Objectives To evaluate the feasibility of unshielded in-hospital multichannel mapping of fetal magnetocardiogram (FMCG), with a 36-channel system for standard adult magnetocardiographic (MCG) recordings, and its reliability according to the recommended standards for FMCG. Methods FMCG was ambulatory mapped with a 36-channel MCG system, in six normal pregnancies at different gestational ages. MCG analysis included adaptive digital filtering of 50 Hz, signal averaging, reconstruction of magnetic field distribution (MFD) and source localization. Fixed Point Independent Component Analysis algorithm (FastICA) was used to reconstruct the FMCG, separating them from maternal contamination and noise. Results The quality of FMCG recorded after the 32nd gestational week and reconstructed with FastICA was close to FMCG obtained in shielded rooms, and good enough to measure cardiac intervals and heart rate variability parameters. In two cases, reconstruction of the MFD during the QRS allowed three-dimensional localization of ventricular sources. Conclusions A first demonstration has been given that multichannel mapping of FMCG can be performed in unshielded clinical environments, with resolution good enough for contactless assessment of fetal cardiac electrophysiology. FastICA processing on unshielded FMCG, recorded after the 32nd week, provided beat-to-beat analysis and heart rate variability assessment. Further work is needed to improve signal reconstruction in early pregnancy. Copyright © 2005 John Wiley & Sons, Ltd. [source]