Detection of Spatially Correlated Gaussian Time Series

Ramírez, David; Vía, Javier; Santamarı́a, Ignacio; Scharf, Louis L.

doi:10.1109/tsp.2010.2053360

Cited by 108 publications

(87 citation statements)

References 20 publications

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“…2), the quantity we seek to maximize is the generalized magnitude squared coherency (GMSC; Chakrabarty et al, 2002;Ramirez et al, 2008Ramirez et al, , 2010, an extension of the traditional coherency to more than two time series. More precisely, we maximize this quantity over the interannual band, where age perturbations have the largest effect on coherency.…”

Section: Optimization Schemementioning

confidence: 99%

A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives

et al. 2014

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Abstract. The ability to precisely date climate proxies is central to the reconstruction of past climate variations. To a degree, all climate proxies are affected by age uncertainties, which are seldom quantified. This article proposes a probabilistic age model for proxies based on layer-counted chronologies, and explores its use for annually banded coral archives. The model considers both missing and doubly counted growth increments (represented as independent processes), accommodates various assumptions about error rates, and allows one to quantify the impact of chronological uncertainties on different diagnostics of variability. In the case of a single coral record, we find that time uncertainties primarily affect high-frequency signals but also significantly bias the estimate of decadal signals. We further explore tuning to an independent, tree-ring-based chronology as a way to identify an optimal age model. A synthetic pseudocoral network is used as testing ground to quantify uncertainties in the estimation of spatiotemporal patterns of variability. Even for small error rates, the amplitude of multidecadal variability is systematically overestimated at the expense of interannual variability (El Niño-Southern Oscillation, or ENSO, in this case), artificially flattening its spectrum at periods longer than 10 years. An optimization approach to correct chronological errors in coherent multivariate records is presented and validated in idealized cases, though it is found difficult to apply in practice due to the large number of solutions. We close with a discussion of possible extensions of this model and connections to existing strategies for modeling age uncertainties.

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Section: Optimization Schemementioning

confidence: 99%

A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives

et al. 2014

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“…This assumption is particularly reasonable if the primary network employs orthogonal frequency division multiplexing (OFDM) as modulation format [15,18]. Similarly, we also assume that the SU collects N T consecutive samples of vector x (n).…”

Section: Proposed Methodology and Signal Modelmentioning

confidence: 99%

“…From [15,18], we know that the multivariate WSS time series has a block-Toeplitz covariance matrix. We remark here that Toeplitz structured matrices belong to a subclass of the persymmetric matrices [19,21,29].…”

Section: Persymmetric Structurementioning

confidence: 99%

“…In order to achieve the proposed goal, we start with our earlier work in [15], where we derived the GLRT. This detector basically tests whether the covariance matrix is block diagonal or not.…”

Section: Introductionmentioning

confidence: 99%

“…In our earlier work [15,18], by assuming wide sense stationary (WSS), we exploited the Toeplitz structure of the covariance matrix. Doing so, we proposed an approximated GLRT in the frequency domain that leads to robustness against the small sample support.…”

Section: Introductionmentioning

confidence: 99%

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Multi-antenna spectrum sensing by exploiting spatio-temporal correlation

Ali

Ramírez

Jansson

et al. 2014

EURASIP J. Adv. Signal Process.

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In this paper, we propose a novel mechanism for spectrum sensing that leads us to exploit the spatio-temporal correlation present in the received signal at a multi-antenna receiver. For the proposed mechanism, we formulate the spectrum sensing scheme by adopting the generalized likelihood ratio test (GLRT). However, the GLRT degenerates in the case of limited sample support. To circumvent this problem, several extensions are proposed that bring robustness to the GLRT in the case of high dimensionality and small sample size. In order to achieve these sample-efficient detection schemes, we modify the GLRT-based detector by exploiting the covariance structure and factoring the large spatio-temporal covariance matrix into spatial and temporal covariance matrices. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages over existing detectors.

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Variability of moisture in coarse woody debris from several ecologically important tree species of the Temperate Zone of Europe

et al. 2011

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Deadwood moisture affects multiple functions of downed logs in forest ecosystems. They include provision of habitats for xylobionts, additional water stores and organic carbon stocks. In contrast to Northern American forests, little is known about moisture variability in downed logs of important tree species within the Temperate Zone of Europe. Therefore, our study aimed at elucidating this variability according to species, site and decay class (DC). Measurements were taken by TDR during two vegetation periods in eight Carpathian natural forests representing distinct site conditions, ranging from xerothermophilous to subalpine. Downed logs of Quercus spp., Abies alba Mill., Fagus sylvatica L., and Picea abies L., belonging to various DCs, were selected and instrumented with TDR probes. Species and DC‐specific TDR calibration showed the importance of intrinsic wood porosity. The course of deadwood moisture consisted of drying during the early decay stage, except for A. alba and F. sylvatica, and an intense water reabsorption at later decay stages. Average moisture for all species and sites displayed seasonal trends, reflecting the occurrence of precipitation clusters and dry periods, as well as short‐term fluctuations. Cross‐spectral analysis revealed that both sapwood and heartwood participated in wetting and drying processes, but only after reaching an advanced stage of decay. New findings can be applied in interpreting, modelling and predicting deadwood water stores, habitat properties and respiration. Copyright © 2011 John Wiley & Sons, Ltd.

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Detection of Spatially Correlated Gaussian Time Series

Cited by 108 publications

References 20 publications

A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives

A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives

Multi-antenna spectrum sensing by exploiting spatio-temporal correlation

Variability of moisture in coarse woody debris from several ecologically important tree species of the Temperate Zone of Europe

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