Exploiting probability density function of deep convolutional autoencoders’ latent space for reliable COVID-19 detection on CT scans

The Journal of Supercomputing - We present a probabilistic method for classifying chest computed tomography (CT) scans into COVID-19 and non-COVID-19. To this end, we design and train, in an...     

Energy-saving self-configuring networked data centers

In this paper, we develop the optimal minimum-energy scheduler for the dynamic online joint allocation of the task sizes, computing rates, communication rates and communication powers in virtualized Networked Data Centers (NetDCs) that operates under hard per-job delay-constraints. The referred NetDC’s infrastructure is composed by multiple frequency-scalable Virtual Machines (VMs), that are interconnected by a bandwidth and power-limited switched Local Area Network (LAN). Due to the nonlinear power-vs.-communication rate relationship, the resulting Computing-Communication Optimization Problem (CCOP) is inherently nonconvex. In order to analytically compute the exact solution of the CCOP, we develop a solving approach that relies on the following two main steps: (i) we prove that the CCOP retains a loosely coupled structure, that allows us to perform the lossless decomposition of the CCOP into the cascade of two simpler sub-problems; and, (ii) we prove that the coupling between the aforementioned sub-problems is provided by a (scalar) constraint, that is linear in the offered workload. The resulting optimal scheduler is amenable of scalable and distributed online implementation and its analytical characterization is in closed-form. After numerically testing its actual performance under randomly time-varying synthetically generated and real-world measured workload traces, we compare the obtained performance with the corresponding ones of some state-of-the-art static and sequential schedulers.     

Spectral Green's Functions for Layered Gyrotropic Structures Through a Transmission-Line Approach

In this work, a straightforward method is shown to derive spectral Green's functions in classes of planar structures including gyrotropic media, based on a recently proposed transmission-line formalism. In particular, the analysis is expressly carried out for a current line source in layered configurations with transversely-magnetized ferrites, useful for microwave and millimeter-wave waveguiding and radiating devices.     

Novel efficient bit-loading algorithms for peak-energy-limitedADSL-type multicarrier systems

We develop solutions for the loading of digital subscriber loop (DSL) multicarrier (MC) systems that present constraints both on overall available energy and maximum energy per carrier. In the emerging G.DMT-based systems planned for high-throughput multimedia applications, the constraint on the peak-energy arises from spectral compatibility issues. However, until today, optimal solutions for loading peak-energy constrained MC systems do not seem explicitly developed in the literature. Hence, starting from suitable applications of the Kuhn-Tucker conditions, we present the analytical relationships characterizing the optimal solution of the peak-energy-limited loading for the general case of concave "rate-functions", and then, we apply them in the context of the so-called "gap analysis". Thus, a low-complexity iterative algorithm implementing this solution is also developed, and its performance is numerically tested on several ANSI-standard asymmetric DSL (ADSL)-type loops impaired by crosstalk. Furthermore, a version of the presented loading algorithm that guarantees integer bit rates with low computational effort is also presented, and its performance is tested. The carried-out performance comparisons allow us to evaluate the throughput loss induced by peak-energy constraints in emerging ADSL-like services     

Minimum-error-probability single-user detection for ISI-impairednarrow-band multiuser systems

The goal of this contribution is to give some insight into the cochannel interference (CCI) suppression capability of novel symbol-by-symbol-type maximum a posteriori probability single-user receivers for nonspread-spectrum multiuser narrow-band systems impaired by intersymbol interference and CCI. The presented multiuser receivers minimize the error probability in the detection of the desired user message on a per-symbol basis. Practical application environments for the developed detectors can be constituted by Ethernet-type LANs and DSL-based high-throughput links connecting central offices to subscribers     

Model parameter estimation for reciprocal Gaussian random processes

The problem of estimating the model parameters of a discrete-index reciprocal Gaussian random process from a limited number of noisy observations is addressed. The general case of a first-order multivariate process is analyzed, stating its basic properties and deriving a linear equation set that relates the model parameters (including the unknown variance of the observation noise) to the (generally nonstationary) autocorrelation function of the observed process. It generalizes to the reciprocal processes the so-called `high-order Yule-Walker equations' for AR processes. Based on these results, a practical estimation algorithm is proposed     

Recursive filtering and smoothing for reciprocal Gaussianprocesses-pinned boundary case

The least square estimation problem for pinned-to-zero discrete-index reciprocal Gaussian processes in additive white noise is solved, thus completing and extending some previous results available in the literature. In particular, following the innovations approach a (finite) set of recursive equations is obtained for the filter and for the three standard classes of smoothers (fixed-point, fixed-interval, fixed-lag). Recursive expressions for the mean square performance of the proposed estimators are also given     

Minimization of Download Times for Large Files over Wireless Channels

The emerging proxy-based wireless content delivery networks (CDNs) should to be designed to download huge-size files over fading-affected channels. However, from a radio resource management point of view, several basic problems still need to be solved for such wireless delivery systems to operate efficiently. Specifically, due to the fading nature of the downlink channel, a still open basic problem is how to design optimal energy-allocation (for example, scheduling) policies that minimize the requested download time when constraints on the total available energy and peak energy are simultaneously active. In this contribution, this problem is solved for application scenarios where the downlink channel is slotted and continuous-state, the carried out traffic is elastic, and the resulting conveyed throughput is measured by any desired increasing concave rate function. Specifically, the optimal energy-allocation policy minimizing the download time is computed in closed form, and its performance is compared against that of a basic on-off heuristic energy scheduler on some Rayleigh-faded multi-antenna delivery systems of practical interest. The carried out performance comparisons point out that the presented optimal policy typically may outperform the heuristic one up to two orders of magnitude, especially when the delivery system is strongly energy limited.     

New results about analysis and design of TCM for ISI channels andcombined equalization/decoding

New upper bounds for the performance of the optimum combined symbol-by-symbol (SbS) Abend-Fritchman-like equalizer and decoder are presented, and a related criterion for the actual design of good trellis-coded-modulated (TCM) schemes effectively matched to the distortion introduced by the intersymbol interference (ISI)-corrupted transmission channel is developed. The actual application of the proposed design criterion is also addressed     

Bounds on the symmetric cutoff rate for QAM transmissions overtime-correlated flat-faded channels

This article presents new upper and lower bounds on the symmetric cutoff rate for block-coded quadrature-amplitude-modulated (QAM) signaling over links affected by time-correlated Rayleigh-distributed flat-faded phenomena. The proposed bounds assume maximum-likelihood soft-decoding with perfect channel-state-information at the receiving side and hold for any form of QAM constellations. These bounds are quickly computable and constitute an efficient means to estimate the cutoff rate of systems employing very long codewords, so that an exact evaluation of the cutoff rate results. Analytical and numerical evidence of the tightness of the presented bounds is also provided