170,048 research outputs found
A cross-layer protocol for cooperative content delivery over mobile ad-hoc networks
No full textReal-time multimedia streaming over MANETs is an active research field since this technology promises scalable and robust audio/video delivery without infrastructure. Even though this problem has several commune features with peer-to-peer routing, the additional sensible parameters of MANETs make wired solutions unfit to this case; therefore, we propose a content routing/delivery protocol inherently designed for the ad-hoc wireless case, exploiting the intrinsic broadcast property of the medium. We provided an implementation of this protocol and we tested it in several use-cases, observing how it assures availability, robustness and scalability. Copyright © 2011 Inderscience Enterprises Ltd
Adozione co-parentale e interesse del minore nella prassi della CEDU : profili di criticità e l’impatto sull’ordinamento italiano
No full textLow-latency video streaming with congestion control in mobile Ad-Hoc networks
No full textIn this paper, we address the challenge of delivering a video stream, encoded with multiple descriptions, in a mobile ad-hoc environment with low-latency constraints. This kind of application is meant to provide an efficient and reliable video communication tool in scenarios where the deployment of an infrastructure is not feasible, such as military and disaster relief applications. First, we present a recently proposed protocol that employs a reliable form of one-hop broadcast to build an efficient overlay network according to a multi-objective function that minimizes the number of packets injected in the network and maximizes the path diversity among descriptions. Then, we introduce the main contribution of this paper: a cross-layer congestion control strategy where the MAC layer is video-coding aware and adjusts its transmission parameters (namely, the RTS retry limit) via congestion/distortion optimization. The main challenge in this approach is providing a reliable estimation of congestion and distortion, given the limited information available at each node. Our simulations show that, if a stringent constraint of low delay is imposed, our technique grants a consistent gain in terms of both PSNR and delay reduction, for bitrates up to a few megabits per second. © 2012 IEEE
H.264-based multiple description coding using motion compensated temporal interpolation
No full textMultiple description coding is a framework adapted to noisy transmission environments. In this work, we use H.264 to create two descriptions of a video sequence, each of them assuring a minimum quality level. If both of them are received, a suitable algorithm is used to produce an improved quality sequence. The key technique is a temporal image interpolation using motion compensation, inspired to the distributed video coding context. The interpolated image blocks are weighted with the received blocks obtained from the other description. The optimal weights are computed at the encoder and efficiently sent to the decoder as side information. The proposed technique shows a remarkable gain for central decoding with respect to similar methods available in the state of the art. ©2010 IEEE
Il riconoscimento in Italia di provvedimenti stranieri di adozione
No full textL’apertura di un numero sempre più significativo di Stati verso forme di adozione, diverse dalle fattispecie previste e disciplinate dalla nostra legislazione, ha messo in evidenza alcune criticità dell’ordinamento italiano, laddove si tratti dare seguito al riconoscimento di status familiari, il cui fondamento giuridico risiede in adozioni straniere per così dire atipiche, ovvero pronunciate a favore di soggetti diversi dalla coppia di coniugi eterosessuali. Il problema, che non riguarda solo lo Stato italiano, è stato sottoposto all’attenzione della Corte EDU, la quale, ribadendo il principio sancito dal diritto internazionale, e più di recente da quello dell’Unione europea, secondo cui in tutte le decisioni che riguardano il minore, il suo superiore interesse dovrebbe essere il parametro cui i giudici devono lasciarsi necessariamente guidare, ha espresso il concetto per cui il riconoscimento dello status filiationis acquisito all’estero può ritenersi strumentale alla tutela del diritto del minore alla continuità delle relazioni affettive in cui questi si riconosce. Concetto questo che è stato recepito da una parte significativa dei nostri giudici, i quali, nell’applicazione delle norme sul riconoscimento delle adozioni straniere, hanno proposto soluzioni ermeneutiche che, in linea con le indicazioni provenienti dalla giurisprudenza europea, hanno spesso consentito di aggirare la rigidità della legislazione interna, consentendo così il riconoscimento di adozioni straniere, anche al di fuori delle ipotesi espressamente previste dal nostro ordinamento
Validation of the IPSL Venus general circulation model with Venus Express data
No full textSeveral numerical models devoted to the simulation of Venus atmosphere have been developed. These models are useful instruments in the understanding of the mechanisms behind the observational features. However, before using their outputs to drive any conclusion about the dynamics and the structure of the atmosphere of Venus, we need to validate them. The process of validation passes by a comparison of the modelled and observational features. Among these numerical models, the Institut Pierre Simon Laplace (IPSL) Venus GCM is the one with a more physical approach, being capable to solve the radiative transfer for each layer of the simulated atmosphere. Our study makes use of Venus Express data – in particular VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) and VeRa (Venus Express Radio Science Experiment) observations – in order to validate this model. This work will analyze the temperature and wind fields in the atmosphere of Venus between 50 and 90 km, that is the range covered by observations. In this range – covering from the upper troposphere to the upper mesosphere – two different regimes are found in the observational thermal field, above and below ~ 76 km, with temperatures increasing towards the pole and towards the equator, respectively. At cloud top level (~ 68 km), permanent cold features, the cold collars, encircle the warmer poles. Winds velocities reach their maximum values (~ 120 m/s) at cloud top, but are faster than the solid body through the entire range of altitudes, determining a condition called superrotation. Seasonal thermal tides are negligible in data, but those related to the diurnal cycle, are present and have a large impact, especially in the upper atmosphere. Venus modelling has always suffered from the strong dependence of the simulation by the initial conditions and the different dynamical cores. Winds far weaker than observed, as well as the inability to reproduce the complex polar vortexes and the subpolar cold regions, have been the major issues for all the numerical simulations for Venus. However, to simulate the fast rotation of the atmosphere and to properly model the thermal structure associated to the polar and subpolar regions, means to understand the physical conditions under which these characteristics develop. Thus, the first objective of our validation of the IPSL Venus GCM is to estimate the general characteristics of the modelled atmosphere and their resemblance of observations. A first, qualitative comparison, is fundamental in recognizing the main dynamical regions in Venus atmosphere. Being the main goal of this work, the validation of a model through its comparison with the thermal and winds field in observational data, we need to clarify the adopted ingredients and the state of the art of our knowledge of Venus. Thus, in chapter 1 we present the overall characteristics of Venus atmosphere, in terms of its composition, thermal structure and dynamics. In chapter 2 we discuss the Venus Express mission, with a focus on the VIRTIS and VeRa experiments and the datasets that we used in this analysis. In chapter 3 we describe the evolution and the present state of the major numerical models trying to simulate the atmosphere of Venus, with a particular emphasis on the IPSL Venus GCM. Chapter 4 and chapter 5 present our validation: the former concerns the analysis of the average temperature and wind fields, the latter is about the thermal tides affecting the temperature and wind fields. As a result, we recognize the capability of the model to reproduce the main observational feature and we propose future steps in order to overcome the major discrepancies that we found in our validation
Il riconoscimento degli status acquisiti all’estero : diritto internazionale privato, diritto dell’UE e giurisprudenza delle Corti europee
No full textL’eterogeneità normativa che caratterizza la disciplina dei rapporti di famiglia nel contesto della UE, accentuata dal recente affermarsi di diversi modelli familiari, pone il problema del riconoscimento in uno Stato di uno status familiare – o personale – acquisito altrove, qualora questo non solo non trovi, ai fini della sua qualificazione giuridica, alcuna corrispondenza nelle fattispecie previste dall’ordinamento di destinazione, ma addirittura si ponga in contrasto con i fondamentali principi su cui esso si fonda, la cui tutela è assicurata dalla possibilità di invocare l’ordine pubblico, quale limite all’ingresso di valori giuridici stranieri. Il mancato riconoscimento degli status familiari, che ha come sua principale conseguenza quella della produzione di situazioni c.d. claudicanti, si pone in contraddizione, pregiudicandone il pieno conseguimento, con gli obiettivi, perseguiti a livello europeo, della libera circolazione delle persone, della tutela dei diritti dell’uomo, con particolare riguardo al diritto al rispetto della vita privata e familiare, alla salvaguardia infine del superiore interesse del minore. In tale contesto si pone quindi l’esigenza di verificare l’efficacia, rispetto al conseguimento di tali obiettivi, dei tradizionali meccanismi di funzionamento delle norme di conflitto, nonché di un ripensamento, almeno in via ermeneutica, delle norme di conflitto in vista della realizzazione dei medesimi
On a hashing-based enhancement of source separation algorithms over finite fields with network coding perspectives
No full textBlind Source Separation (BSS) deals with the recovery of source signals from a set of observed mixtures, when little or no knowledge of the mixing process is available. BSS can find an application in the context of network coding, where relaying linear combinations of packets maximizes the throughput and increases the loss immunity. By relieving the nodes from the need to send the combination coefficients, the overhead cost is largely reduced. However, the scaling ambiguity of the technique and the quasi-uniformity of compressed media sources makes it unfit, at its present state, for multimedia transmission. In order to open new practical applications for BSS in the context of multimedia transmission, we have recently proposed to use a non-linear encoding to increase the discriminating power of the classical entropy-based separation methods. Here, we propose to append to each source a non-linear message digest, which offers an overhead smaller than a per-symbol encoding and that can be more easily tuned. Our results prove that our algorithm is able to provide high decoding rates for different media types such as image, audio, and video, when the transmitted messages are less than 1.5 kilobytes, which is typically the case in a realistic transmission scenario
Multi-view video streaming over wireless networks with RD-optimized scheduling of network coded packets
No full textMulti-view video streaming is an emerging video paradigm that enables new interactive services, such as free viewpoint television and immersive teleconferencing. However, it comes with a high bandwidth cost, as the equivalent of many single-view streams has to be transmitted. Network coding (NC) can improve the performance of the network by allowing nodes to combine received packets before retransmission. Several works have shown NC to be beneficiai in wireless networks, but the delay introduced by buffering before decoding raises a problem in real-time streaming applications. Here, we propose to use Expanding Window NC (EWNC) for multi-view streaming to allow immediate decoding of the received packets. The order in which the packets are included in the coding window is chosen via RD-optimization for the current sending opportunity. Results show that our approach consistently outperforms both classical NC applied on each view independently and transmission without NC. © 2012 IEEE
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