Search results for " Bandwidth"

showing 6 items of 26 documents

Graph-based minimal path tracking in the skeleton of the retinal vascular network

2012

This paper presents a semi-automatic framework for minimal path tracking in the skeleton of the retinal vascular network. The method is based on the graph structure of the vessel network. The vascular network is represented based on the skeleton of the available segmented vessels and using an undirected graph. Significant points on the skeleton are considered nodes of the graph, while the edge of the graph is represented by the vessel segment linking two neighboring nodes. The graph is represented then in the form of a connectivity matrix, using a novel method for defining vertex connectivity. Dijkstra and Floyd-Warshall algorithms are applied for detection of minimal paths within the graph…

Settore INF/01 - Informaticabusiness.industryComputer sciencePath trackingGraph theoryImage segmentationGraph bandwidthRetinal Images Graphs Dijkstra Floyd-WarshallGraph (abstract data type)Computer visionArtificial intelligencebusinessBeta skeletonDijkstra's algorithmAlgorithmRandom geometric graphMathematicsofComputing_DISCRETEMATHEMATICS2012 25th IEEE International Symposium on Computer-Based Medical Systems (CBMS)
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Large-Scale Available Bandwidth Measurements: Interference in Current Techniques

2011

The end-to-end available bandwidth of an Internet path is a desirable information that can be exploited to optimize system performance. Several tools have been proposed in the past to estimate it. However, existing measurement techniques were not designed for large-scale deployments. In this paper we show that current tools do not properly work where multiple probing processes share a portion of a path. We provide experimental evidence to quantify the impact of mutual interference between measurements. We further analyze the characteristics of popular tools, quantifying (i) the impact of mutual interference, (ii) the total overhead imposed to the network and (iii) the intrusiveness of the m…

Settore ING-INF/03 - TelecomunicazioniComputer Networks and Communicationsbusiness.industryComputer scienceSystem of measurementReal-time computingAvailable BandwidthProcess (computing)Interference (wave propagation)ScalabilityBandwidth (computing)Overhead (computing)The InternetElectrical and Electronic EngineeringbusinessDimensioning
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Rateless Codes Performance Analysis in Correlated Channel Model for GEO Free Space Optics Downlinks

2012

Settore ING-INF/03 - TelecomunicazioniFree Space Optics (FSO) technologies for satellite communications offer several advantages: wide bandwidth high rate capability immunity to electromagnetic interference and small equipment size. Thus they are suitable for inter-satellite links deep space communications and also for high data rate ground-to-satellite/satellite-to-ground communications. Nevertheless FSO links suffer impairments that cause power signal degradation at the receiver. Scattering and absorption cause power signal attenuations predictable by suitable deterministic models. Optical turbulence causes random irradiance fluctuations which can generate signal fading events and can thereby only be predicted by statistical models. Attenuation and fading events can corrupt FSO links and so it would be recommended to add mitigation error codes on the communication link. FSO channel can be described as an erasure channel: fading events can cause erasure errors. We have identified in rateless codes (RCs) a suitable solution to be employed in FSO links. RCs do not need feedback and they add a redundant coding on the source data that allows the receiver to recover the whole payload despite erasure errors. We implemented two different of rateless codes: Luby Transform (LT) and Raptor. We analyzed their performances on a simulated turbulent GEO FSO downlink (1 Gbps - OOK modulation) at a 106 μm wavelength and for different values of zenith angles. Assuming a plane-wave propagation and employing Hufnagel-Valley we modeled the downlink using: 1) a temporal correlated channel model based on Gamma-Gamma probability distribution and 2) an irradiance covariance function that we converted on a time function using Taylor frozen eddies hypothesis. Our new channel model is able to simulate irradiance fluctuations at different turbulence conditions as it will be shown in the full paper. We will also report performance results of LT and Raptor codes at overhead range varying between 0 and 50% and for different values of source packets.Settore ING-INF/01 - Elettronica
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Bimodal Approach for Noise Figures of Merit Evaluation in Quantum-Limited Josephson Traveling Wave Parametric Amplifiers

2022

The advent of ultra-low noise microwave amplifiers revolutionized several research fields demanding quantum-limited technologies. Exploiting a theoretical bimodal description of a linear phase-preserving amplifier, in this contribution we analyze some of the intrinsic properties of a model architecture (i.e., an rf-SQUID based Josephson Traveling Wave Parametric Amplifier) in terms of amplification and noise generation for key case study input states (Fock and coherents). Furthermore, we present an analysis of the output signals generated by the parametric amplification mechanism when thermal noise fluctuations feed the device.

Superconducting microwave devicesMicrowave photonicMicrowave amplifiersCondensed Matter - SuperconductivityPhysicsFOS: Physical sciencesMicrowave photonics Noise figure Superconducting microwave devices.Condensed Matter PhysicsNoise figureSettore ING-INF/01 - ElettronicaSuperconducting microwave deviceElectronic Optical and Magnetic MaterialsSuperconductivity (cond-mat.supr-con)BandwidthMicrowave amplifierBandwidth; Gain; Microwave amplifiers; Microwave photonics; Noise figure; Physics; Superconducting microwave devicesMicrowave photonicsHardware_INTEGRATEDCIRCUITSPhysicGainElectrical and Electronic EngineeringPhysics Gain Microwave amplifiers Noise figure Superconducting microwave devices Microwave photonics Bandwidth Microwave photonics noise figure superconducting microwave devicesMicrowave photonics; Noise figure; Superconducting microwave devicesIEEE Transactions on Applied Superconductivity
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Achieving Fair Bandwidth Distribution in WiFi Networks: A Game Theoretical Approach

2011

International audience; Achieving fair bandwidth distribution among uplink and downlink ows in IEEE 802.11 infrastructure networks is a complex issue, due to the well-known features of the Distributed Coordination Function (DCF) which regulates the access to the shared medium. Indeed, the dynamic adaptation of the contention windows causes phenomena of short-term unfairness, while the use of homogeneous contention parameters among the contending nodes makes the aggregated downlink bandwidth equal to the uplink bandwidth of a single node. We propose a dynamic tuning of the contention parameters used by the nodes, based on simple network monitoring functionalities and rational strategies. Spe…

WiFi; game theorygame theoryDynamic bandwidth allocationbusiness.industryComputer scienceDistributed computingWiFiComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSNetwork monitoringShared mediumDistributed coordination functionNash equilibriumShared resource[INFO.INFO-NI]Computer Science [cs]/Networking and Internet Architecture [cs.NI]Telecommunications linkComputer Science::Networking and Internet ArchitectureBandwidth (computing)NetworksbusinessGame theoryGame theoryComputer network
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Largescale available bandwidth measurements: Shortcomings of current techniques

2009

available bandwidth

available bandwidthSettore ING-INF/03 - Telecomunicazioni
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