Estimation of Time-Limited Channel Spectra From Nonuniform Samples

This paper deals with the estimation of a time-invariant channel spectrum from its own nonuniform samples, assuming there is a bound on the channel’s delay spread. Except for this last assumption, this is the basic estimation problem in systems providing channel spectral samples. However, as shown in the paper, the delay spread bound leads us to view the spectrum as a band-limited signal, rather than the Fourier transform of a tapped delay line (TDL). Using this alternative model, a linear estimator is presented that approximately minimizes the expected root-mean-square (RMS) error for a deterministic channel. Its main advantage over the TDL is that it takes into account the spectrum’s smoothness (time width), thus providing a performance improvement. The proposed estimator is compared numerically with the maximum likelihood (ML) estimator based on a TDL model in pilot-assisted channel estimation (PACE) for OFDM.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Project TEC2011-28201-C02-02

ML Estimation and Detection of Multiple Frequencies Through Periodogram Estimate Refinement

This letter presents a method to detect and estimate multiple frequencies based on the maximum-likelihood principle. The method addresses the three main difficulties in this kind of computation, which are the detection of the number of frequencies, the coarse localization of the cost function's global maximum, and the iterative refinement of an initial estimate. Fundamentally, it consists of first detecting and estimating single frequencies or frequency clusters using the periodogram, and then refining this last estimate through a Newton-type method. This second step is fast because its complexity is independent of the number of samples, once a single fast Fourier transform (FFT) has been computed. These two steps are iteratively repeated until no mode frequency is above a fixed detection threshold. The main advantage of the proposed method is its low complexity, given that its computational burden is just that of a few FFTs in typical scenarios. The method is assessed in a numerical example.This work was supported by the Spanish Ministry of Economy and Competitiveness and EU FEDER under project TIN2014-55413-C2-2-P

Efficient Computation of ML DOA Estimates Under Unknown Nonuniform Sensor Noise Powers

This paper presents an efficient method for computing Maximum Likelihood (ML) direction-of-arrival (DOA) estimates in scenarios in which the sensor noise powers are nonuniform and unknown. The method combines the Alternating Projection (AP) algorithm for coarsely locating additional DOAs and Newton iterations for finally obtaining the ML estimates. Compared with the existing approaches, the method reduces the computational burden significantly due to the small number of Newton iterations required and to the efficient computation of each iteration. Specifically, the iterations are computed in a small number of arithmetic operations thanks to the closed-form formulas for the gradient and Hessian of the ML cost functions presented in this paper. The method’s total computational burden is of just a few mega-flops (mega floating-point operations) in typical cases. We present the method for the deterministic and stochastic ML estimators. Then, an analysis of the deterministic ML cost function’s gradient reveals an unexpected drawback: its associated estimator is either degenerate or inconsistent. Finally, we assess the method’s root-mean-square (RMS) error and computational burden numerically and compare it with other relevant estimators in the literature.This work was supported by the Spanish Ministry of Science and Innovation, the State Agency of Research (AEI) and the European Funds for Regional Development (EFRD) under Project PID2020-117303GB-C22

Efficient Wideband DOA Estimation Through Function Evaluation Techniques

This paper presents an efficient evaluation method for the functions involved in the computation of direction-of-arrival (DOA) estimators. The method is a combination of the Chebyshev and barycentric interpolators, and makes use of the Discrete Cosine Transform (DCT). We present two applications of this method. The first is for reducing the complexity of the line searches in three wideband DOA estimators: Incoherent Multiple Signal Classification (IC-MUSIC), Test of Orthogonality of Projected Subspaces (TOPS), and Deterministic Maximum Likelihood (DML). And the second application is a procedure to compress the wideband DML cost function, so that it is formed by just a few summands. This compression entails a reduction in complexity by a large factor. The evaluation method and its applications are numerically assessed in several numerical examples

Estilos parentales y competencias comunicativas en niños de cinco años en una institución educativa del distrito de Pariñas - Talara, 2023

La presente investigación tuvo como objetivo determinar la relación entre estilos parentales y competencias comunicativas en niños de cinco años en una institución educativa del distrito de Pariña - Talara, 2023, asimismo, se consideró realizar una investigación de tipo básico, enfoque cuantitativo, método hipotéticodeductivo, nivel correlacional y de diseño no experimental, cabe agregar, que para efectos del estudio, la población la integraron 100 niños y niñas de cinco años, y la muestra fue de tipo censal. Asimismo, para recoger información de las variables se consideró como técnica a la observación y los instrumentos fueron dos listas de cotejo. Respecto a los resultados, el 20.0 % (20) evidenciaron que los padres tienen bajo estilo parental, 35.0 % medio y 45.0 % alto, de igual modo, el 15.0 % de niños se encontraron en inicio del desarrollo de sus competencias comunicativas, el 25.0 % en proceso y 60.0 % logrado; en cuanto al análisis inferencial, se determinó que el coeficiente correlacional tuvo un valor de .726, en tal sentido, se pudo afirmar que el alto desarrollo de los estilos parentales evidencia que los estudiantes dominan las competencias comunicativas

An Improved Phase Filter for Differential SAR Interferometry Based on an Iterative Method

Phase quality is a key element in the analysis of the deformation of the Earth's surface carried out with differential synthetic aperture radar interferometry. Various decorrelation sources may degrade the surface deformation estimates, and thus, phase filters are needed for this kind of application. The well-known Goldstein filter is the most widely used due to its simple implementation and computational efficiency. In the past years, improved filters have been proposed, which are based on this filter but introduce variations in the data processing. The effectiveness of these filters mostly depends on the size of the filtering window, the weight of the smoothed spectrum, and the kernel used to filter the spectrum. In this paper, we evaluate the performance of four of these filters and present a new method that outperforms all of them. The proposed filter is based on an iterative method in which the original phase is denoised progressively with adaptive filtering windows of different sizes. The effectiveness of the filter is controlled by the interferometric coherence, a direct indicator of the phase quality. Moreover, we introduce some modifications regarding the processing of the power spectrum. Specifically, we propose to smooth the original phase using a new filter which is based on a Chebyshev interpolation scheme. The performance of the new filter has been tested on both simulated and real interferograms, acquired by RADARSAT-2 and the Uninhabited Aerial Vehicle Synthetic Aperture Radar, which mapped two different geological events that caused surface deformation.This work was supported in part by the Spanish Ministry of Economy, Industry and Competitiveness, in part by the State Agency of Research (AEI), in part by the European Funds for Regional Development under Project TIN2014-55413-C2-2-P and Project TEC2017-85244-C2-1-P, in part by the U.K. Natural Environmental Research Council through the Looking Inside the Continents under Grant NE/K011006/1, in part by the Rapid deployment of a seismic array in Ecuador following the April 16th 2016 M7.8 Pedernales earthquake under Grant NE/P008828/1, and in part by the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics under Grant COMET, GA/13/M/031

Coordinación de competencias de tratamiento de señal y comunicaciones en estudios de Telecomunicación en EPS-UA

Los objetivos del presente trabajo son el seguimiento, la coordinación, la evaluación y la mejora en la distribución de competencias de las asignaturas obligatorias de los cursos primero, segundo y tercero del Grado en Ingeniería en Sonido e Imagen en Telecomunicación y una asignatura obligatoria del Máster en Ingeniería de Telecomunicación. La red tiene carácter transversal y se centra en materias de tratamiento de señal y comunicaciones de estudios de Telecomunicación en la Escuela Politécnica Superior de la Universidad de Alicante. Para alcanzar los objetivos se plantea llevar a cabo una colaboración de la que formen parte las subdirecciones de las titulaciones, la dirección del departamento y las profesoras y los profesores de las asignaturas relacionadas con las competencias de tratamiento de señal y comunicaciones en el Grado y Máster Universitario de estudios de Telecomunicación en la Escuela Politécnica Superior. En el proceso se elaboraron documentos para facilitar la puesta en común y la concreción de acuerdos de mejora

Iterative Filtering Based on Adaptive Chebyshev Kernel Functions for Noise Supression in Differential SAR Interferograms

Differential SAR Interferometry (DInSAR) is a powerful remote sensing technique employed to monitor surface displacements, such as ground subsidence or strong deformations caused by geological activity. The quality of the interferometric phase between two combined SAR images is essential for the estimation of the surface deformation. Multi-pIe decorrelation factors may degrade the quality of the measurements and, then, the development of filtering methods for noise suppression is mandatory. In this work, we propose a new strategy to improve noise reduction while preserving the original phase structure. The new method consists in an iterative filter in which noise reduction is achieved progressively. The original phase is filtered with adaptive kernels based on Chebyshev interpolation functions. The filter is especially useful for DInSAR geophysical applications, such as earthquakes or volcanic eruptions monitoring. The performance of the proposed method has been tested with both simulated data and recently acquired Sentinel-1 SAR data which mapped the August 2016 Central Italy earthquake.This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), the State Agency of Research (AEI) and the European Funds for Regional Development (FEDER) under Projects TIN2014-55413-C2-2-P and TEC2017-85244-C2-1-P. This work was partially supported by the UK Natural Environmental Research Council (NERC) through the “Looking Inside the Continents (LiCS)” (NE/K011006/1), the “Rapid deployment of a seismic array in Ecuador following the April 16th 2016 M7.8 Pedernales earthquake” (NE/P008828/1), and the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, GA/13/M/031, http://comet.nerc.ac.uk) projects

Aprendizaje basado en proyectos (PBL) aplicado a la docencia de sistemas tecnológicos de última generación

El planteamiento general de la docencia de asignaturas cuyo contenido es eminentemente tecnológico, presenta el reto del constante y rápido cambio asociado a los avances en desarrollo tecnológico. Dentro de este contexto, se plantea emplear un método basado en la generación de herramientas que permitan un seguimiento autónomo de los cambios frente a opciones más descriptivas del estado actual de los sistemas estudiados. Sobre esta base, se estudia la idoneidad de un contexto basado en el desarrollo de proyectos que, si bien tienen necesariamente que abordar una temática particular, supone una forma a priori interesante de generar las habilidades necesarias para el aprendizaje autónomo y continuado

Influence of Type 2 Diabetes in the Association of PNPLA3 rs738409 and TM6SF2 rs58542926 Polymorphisms in NASH Advanced Liver Fibrosis

Advanced fibrosis; Nonalcoholic steatohepatitis; Type 2 diabetesFibrosis avanzada; Esteatohepatitis no alcohólica; Diabetes tipo 2Fibrosi avançada; Esteatohepatitis no alcohòlica; Diabetis tipus 2Nonalcoholic steatohepatitis (NASH) is a leading cause of cirrhosis in western countries. Insulin resistance (IR), type 2 diabetes (T2D), and the polymorphisms patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 and transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 are independent risk factors of NASH. Nevertheless, little is known about the interaction between IR and T2D with these polymorphisms in the pathogenesis of NASH and the development of advanced fibrosis. Thus, our study aimed to investigate this relationship. This is a cross-sectional study including NASH patients diagnosed by liver biopsy, at the Vall d’Hebron University Hospital. A total of 140 patients were included (93 T2D, 47 non-T2D). T2D (OR = 4.67; 95%CI 2.13–10.20; p < 0.001), PNPLA3 rs738409 and TM6SF2 rs58542926 polymorphisms (OR = 3.94; 95%CI 1.63–9.54; p = 0.002) were independently related with advanced liver fibrosis. T2D increased the risk of advance fibrosis on top of the two polymorphisms (OR = 14.69; 95%CI 3.03–77.35; p = 0.001 for PNPLA3 rs738409 and OR = 11.45; 95%CI 3.16–41.55; p < 0.001 for TM6SF2 rs58542926). In non-T2D patients, the IR (HOMA-IR ≥ 5.2, OR = 14.33; 95%CI 2.14–18.66; p = 0.014) increased the risk of advanced fibrosis when the polymorphisms were present (OR = 19.04; 95%CI 1.71–650.84; p = 0.042). The T2D and IR status increase the risk of advanced fibrosis in patients with NASH carrying the PNPLA3 rs738409 and/or TM6SF2 rs58542926 polymorphisms, respectively