1,721,225 research outputs found
Managing information constraints over networks through the lens of configuration functions
No full textThis work deals with networks of agents that exchange information under communication constraints. As a first contribution, the theory of configuration functions is exploited to obtain a general abstract formulation of the network information as a function of the network constraints. As a second contribution, two classic network paradigms are examined: i) a decentralized architecture with remote fusion center; and ii) a fully-flat decentralized architecture with local data exchange between neighboring agents. It is shown how these paradigms match well with the general formulation in terms of configuration functions. Finally, the statistical concentration properties of configuration functions are exploited to characterize the information growth rate under both the aforementioned network paradigms, revealing the thermodynamic deterministic behavior that emerges with high probability as the network size scales to infinity
An improved version of the generalized Laplacian pyramid algorithm for pansharpening
No full textThe spatial resolution of multispectral data can be synthetically improved by exploiting the spatial content of a companion panchromatic image. This process, named pansharpening, is widely employed by data providers to augment the quality of images made available for many applications. The huge demand requires the utilization of efficient fusion algorithms that do not require specific training phases, but rather exploit physical considerations to combine the available data. For this reason, classical model-based approaches are still widely used in practice. We created and assessed a method for improving a widespread approach, based on the generalized Laplacian pyramid decomposition, by combining two different cost-effective upgrades: the estimation of the detail-extraction filter from data and the utilization of an improved injection scheme based on multilinear regression. The proposed method was compared with several existing efficient pansharpening algorithms, employing the most credited performance evaluation protocols. The capability of achieving optimal results in very different scenarios was demonstrated by employing data acquired by the IKONOS and WorldView-3 satellites
ADVoIP: Adversarial Detection of Encrypted and Concealed VoIP
Full text linkA network attacker wants to transmit Voice-over-IP (VoIP) traffic streams covertly. He tries to evade the detection system by manipulating the VoIP streams through padding, shifting, and splitting operations, so as to conceal them amidst the Internet traffic. A defender wants to detect the manipulated VoIP streams. Tackling this problem from an adversarial perspective, we provide two contributions: 1) we obtain a highly stylized representation of VoIP streams in terms of transmission frequency F and packet length L , and characterize the F, L region achievable by the attacker's transformation and 2) We formulate the VoIP detection game, and find both theoretical conditions and a practical algorithm to find the Nash equilibrium of the game. As a result, we are able to design an optimal (from the adversarial perspective) algorithm for VoIP detection, which is nicknamed as ADVoIP. Simulations over real network traces, and comparison with existing approaches, show the effectiveness of the proposed approach
A Data-Driven Model-Based Regression Applied to Panchromatic Sharpening
No full textImage fusion is growing interest in recent years, thanks to the huge amount of data acquired everyday by sensors on board of satellite platforms. The enhancement of the spatial resolution of a multispectral (MS) image through the use of a panchromatic (PAN) image, usually called pansharpening, is getting more and more relevant. In this work, we focus on the problem of the estimation of the injection coefficients that rule the enhancement of the spatial resolution of the MS image by properly adding the PAN details. In particular, a statistical analysis of the residuals coming from the linear multivariate regression between details extracted from the PAN image and the MS image is performed. A novel hybrid model is introduced for accurately describing the statistical distribution of these residuals, together with a procedure for efficiently estimating both the parameters of the residual distribution and the injection coefficients. The improvements achieved by the proposed approach are assessed using two very high resolution datasets acquired by the WorldView-3 and Worldview-4 satellites. The benefits of the proposed approach are particularly clear when vegetated areas are involved in the fusion process
Adversarial Kendall's Model towards Containment of Distributed Cyber-Threats
No full textThis work examines propagation of cyber-threats over networks under an adversarial formulation. Exploiting Kendall's birth-death-immigration model, we propose an analytical framework to describe the stochastic dynamics of cyber-threat propagation in a collection of heterogeneous sub-networks characterized by different attributes. We propose two formalisations of the problem as zero-sum games involving two adversaries: an attacker, who launches cyber-threats across the distinct sub-networks; and a defender, who tries to mitigate the threats by delivering suitable countermeasures. According to the first formalisation, the interplay between the defender and the attacker is modelled as a Stackelberg leader-follower game, while the second formalisation considers a strategic game wherein the two contenders play simultaneously without knowing the choice of the other player. We derive the equilibrium strategies for both versions of the game, and discuss a number of insightful interplays and ramifications of the different equilibrium points for the problem at hand. The equilibrium strategies depend on three fundamental attributes: i ) the available resource budget of the attacker and the defender; ii ) the capacity of the legitimate nodes to (unintentionally) forward the threat across the network, after they have been compromised during the propagation of the threat; iii ) the intrinsic characteristics of the sub-networks, namely, their immunity to the attacks, their inertia in responding to the countermeasures, and the importance of the individual sub-networks. The relevance of the proposed solution is illustrated through a series of examples and numerical simulations
Editorial for Special Issue "Remote Sensing for Target Object Detection and Identification"
No full textThis special issue gathers fourteen papers focused on the application of a variety of target object detection and identification techniques for remotely-sensed data. These data are acquired by different types of sensors (both passive and active) and are located on various platforms, ranging from satellites to unmanned aerial vehicles. This editorial provides an overview of the contributed papers, briefly presenting the technologies and algorithms employed as well as the related applications
Correlated disorder in broadband dielectric multilayered reflectors
No full textA disordered one-dimensional photonic structure can be realized as a multilayer consisting of two different dielectric materials that alternate with random thicknesses. Generally, such a multilayer exhibits a wide reflection wavelength range in which, however, transmission notches that break the reflectance band continuity may be present due to stochastic resonances. Statistical analysis reveals that multilayers characterized by correlated disorder (i.e., thickness sequence presenting a non-negligible degree of autocorrelation) do not suffer from these stochastic resonances and behave as high-performance broadband reflectors
Localization of gravitational sources from time-frequency maps
No full textThe localization of Gravitational Waves (GW) sources, that is key in identifying their physical nature via the joint use of GW interferometers and other companion instruments, is mainly based on the observed delays between each pair of interferometers. In this scenario, Time-Frequency (TF) representations are widely used for GW detection and measurements, as the time delays between two detected GWs can be estimated by suitably aligning the related TF maps. In this work we adopt the Phase Correlation method for TF maps alignment, and compare different TF representations (i.e., Continuous Q Transform, Wigner-Ville Distribution, Smoothed Wigner-Ville and Sparsified Wigner-Ville) in terms of time delay estimation performance
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