In this paper, we develop simple principal and minor subspace tracking algorithms that exactly maintain the orthonormality of the subspace matrix estimate over time. Each of these algorithms use m identical Householde...
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ISBN:
(纸本)0780363396
In this paper, we develop simple principal and minor subspace tracking algorithms that exactly maintain the orthonormality of the subspace matrix estimate over time. Each of these algorithms use m identical Householder transformations to update the rows of the subspace matrix estimate at each time instant. Unlike many other approaches, ours have asymptotic complexities that scale linearly with the number of adaptive coefficients. We show that existing gradient-based and projection approximation subspace tracking (PAST) methods are first-order approximate versions of our proposed methods, and we also derive several more-accurate approximations. Simulations verify the excellent numerical behaviors of the proposed methods in subspace tracking tasks.
In radio astronomy images are made of astronomical objects as they appear at radio frequencies using a technique called aperture synthesis. Signats from several antennas are correlated and integrated over time. The da...
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ISBN:
(纸本)1424403081
In radio astronomy images are made of astronomical objects as they appear at radio frequencies using a technique called aperture synthesis. Signats from several antennas are correlated and integrated over time. The data collected over several hours are further processed to calibrate the instrument and to form an image or intensity map. The calibration and imaging algorithms do not use the autocorrelations because the receiver noise is unstable and hence considered unknown. In literature the Cramer Rao Bound for the calibration problem has been derived assuming that the autocorrelations are part of the available data. If the assumption is correct that the autocorrelations do not contain useful information when the receiver noise is unknown, than the CRB for the case that the autocorrelations are not part of the data will be the same. In this paper we will derive the CRB excluding the autocorrelations and show that it indeed does not matter whether the autocorrelations are included or not.
Many nonlinear parameter estimation problems can be described by the class of curved exponential families. The latter are fundamental concept in the framework of Information Geometry. This paper shows that when a clos...
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ISBN:
(纸本)9781479914814
Many nonlinear parameter estimation problems can be described by the class of curved exponential families. The latter are fundamental concept in the framework of Information Geometry. This paper shows that when a closed-form statistical model is available the problem can be mapped onto the corresponding statistical manifolds via fixed parameterizations and thus solved optimally through a manifold gradient method. The solution process involves a dual projection which iteratively operates under the e-connection and m-connection in the flat manifolds with the coordinate systems in which the Cramer Rao Bound is attained. An example of tracking a moving target by two bearings-only sensors with location uncertainties is presented to demonstrate the efficiency and optimality of this manifold based method as well as the associated geometrical interpretation.
This paper undertakes a comparison of two nonhomogeneity detection (NHD) methods and addresses their impact on the performance of the adaptive matched filter (AMF) method and the normalized adaptive matched filter (NA...
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ISBN:
(纸本)0780375513
This paper undertakes a comparison of two nonhomogeneity detection (NHD) methods and addresses their impact on the performance of the adaptive matched filter (AMF) method and the normalized adaptive matched filter (NAMF) method in severely non-homogeneous clutter scenarios. Performance analysis is carried out using simulated data as well as measured data from the MCARM Program. Specific consideration is given to the computational cost of the NHD method and the sample support requirements. This paper presents a technique for speeding up the computations in the NHD. Performance is reported in terms of the probability of detection versus signal-to-noise-ratio (SNR) for simulated data analyses.
Multipath propagation has a significant impact on the performance of cellular and Personal Communication Services (PCS) systems in urban environments. This paper contains analyses to better understand urban multipath ...
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ISBN:
(纸本)0780363396
Multipath propagation has a significant impact on the performance of cellular and Personal Communication Services (PCS) systems in urban environments. This paper contains analyses to better understand urban multipath and examines the use of base-station antenna arrays to obtain spatial diversity. The results are based on data collected on large sparse aperture arrays and finely sampled arrays at a location below surrounding rooftop heights for both PCS and cellular frequencies. A statistical model is formulated to explain the relationship between multipath scatterers and signal cross-correlations as a function of antenna spacing.
Multiple transmitters and receivers can be used to provide high link capacity in future wireless systems. Herein analysis of real indoor environment Multiple-Input-Multiple-Output measurements on the 5.8 GHz band is p...
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ISBN:
(纸本)0780363396
Multiple transmitters and receivers can be used to provide high link capacity in future wireless systems. Herein analysis of real indoor environment Multiple-Input-Multiple-Output measurements on the 5.8 GHz band is performed. The possible increase in capacity, utilizing multiple transmit and receive elements is examined. The gain possible when using channel knowledge at both transmitter and receiver is shown and the capacity dependence on the intra-element distance is examined for the experimental system and compared to simulations.
We propose an approach for tracking a varying number of simultaneously active acoustic wideband signal sources in an acoustic enclosure. Relying on the assumption of W-disjoint orthogonality, the method uses narrowban...
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ISBN:
(纸本)9781538647523
We propose an approach for tracking a varying number of simultaneously active acoustic wideband signal sources in an acoustic enclosure. Relying on the assumption of W-disjoint orthogonality, the method uses narrowband position estimates of the sources for the targets. The instantaneous position estimates form clusters rather than single points, as would be required for a conventional Probability Hypothesis Density (PHD) filter. Therefore, we model the position estimates as extended targets and use a special form of the PHD filter, the extended target Gaussian mixture PHD filter, for tracking the targets. This allows to model target birth and death, which correspond to speech onset and end of utterance, respectively. With this model and by using the well-developed theory of Finite Set Statistics (FISST)-based multi-target tracking, we provide a comprehensive, strictly Bayesian treatment of the problem of tracking wideband acoustic sources using narrowband position estimates. We validate the results by tracking a varying number of targets in an enclosure simulated with the image-source method.
Cooperative communication in energy-constrained networks is a topic of emerging interest in recent years especially for sensor network applications. We consider cooperative transmission from a cluster of nodes to a re...
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ISBN:
(纸本)1424403081
Cooperative communication in energy-constrained networks is a topic of emerging interest in recent years especially for sensor network applications. We consider cooperative transmission from a cluster of nodes to a remote receiver. The transmission protocol used is randomized orthogonal space-time block coding, which allows each node to randomly transmit one column of a given orthogonal space-time code matrix. Previous work on the topic has shown that the scheme can achieve maximum possible diversity order for a given SNR as the number of cooperating nodes increases. In this paper we examine the range extension achievable under realistic conditions accounting for time synchronization errors and use of pulse shaping filters. We show that the scaling of range as the number of nodes increase with timing error is not linear. It reaches a limit beyond which range improvement is not significant.
A cluster of commodity personal computers (PCs) is an attractive platform for signalprocessing, especially for applications like sensorarrays where there is significant parallelism in the computation. This paper rep...
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ISBN:
(纸本)0780363396
A cluster of commodity personal computers (PCs) is an attractive platform for signalprocessing, especially for applications like sensorarrays where there is significant parallelism in the computation. This paper reports the results of experiments with several small cluster configurations to explore the opportunities and limitations of this approach. Experiments included uniprocessor and multiprocessor PCs, 100 MBit/sec and 1 Gbit/sec ethernet. All experiments were receive-only, starting from raw spectrum samples provided by a wideband A/D card, and all signalprocessing code ran as application processes on top of standard Linux. The applications used to drive the experiments were delay and sum beamforming and the simultaneous reception of multiple AMPS cellular channels. The currently standard PCI I/O bus (32 bits at 33 MHz) was the most significant bottleneck in the experiments. This suggests that the arrival of the next generation of commodity PCs, with faster I/O busses (such as 64-bit PCI at 66 MHz), may open the door to their use as a low-cost platform for a variety of low-end realtime signalprocessing applications.
A technique is presented for incorporating pulse-to-pulse (inter-pulse) motion effects into side-looking array radar data models yielding a motion-sensitive space-time snapshot. Low flying, highly-maneuverable Unmanne...
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ISBN:
(纸本)1424403081
A technique is presented for incorporating pulse-to-pulse (inter-pulse) motion effects into side-looking array radar data models yielding a motion-sensitive space-time snapshot. Low flying, highly-maneuverable Unmanned Aerial Vehicles (UAV) represent a potential worst case application scenario given their roll, yaw, and pitch rates are primarily limited by structural integrity. High degrees of maneuverability during the Coherent processing Interval (CPI) allow clutter and target returns to change significantly. The technique presented uses M coordinate transformations to describe platform attitude variations throughout the CPI. Ward's model then is extended to incorporate maneuver-induced changes in spatial frequency and Doppler. The new motion-sensitive space-time snapshot is used to characterize Space Time Adaptive processing (STAP) performance without motion-compensation applied. Results clearly show motion-induced clutter-null broadening with measurable degradation of STAP algorithm minimal discernable velocity.
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