Search results for "Satellite links"

showing 2 items of 2 documents

Streaming for vehicular users via elastic proxy buffer management

2004

In this article we refer to the market of vehicular networks, where groups of customers located in the same public vehicle (e.g., a train or bus) connect to a terrestrial network through a wireless/satellite backbone link. Elastic buffering is a proxy management technique devised to decouple the multimedia information retrieval rate on the network backbone from the playout streaming rate at the user terminal. It has been shown in the past that the application of elastic buffering mechanisms in terrestrial networks brings significant advantages in terms of network effectiveness. We show that elastic buffering is an extremely effective means to reduce, or even eliminate, streaming service out…

Mobile radioService (systems architecture)Computer Networks and CommunicationsComputer scienceDelayed real time servicesMultimedia information retrievalCommunication channels (information theory)Resource sharing algorithmBuffer storageWirelessInformation retrievalWireless telecommunication systemsElectrical and Electronic EngineeringReal time streaming servicesProxy (statistics)Railroad car equipmentVehicular area networksBackbone networkInternetMobile computingVehicular ad hoc networkbusiness.industrySettore ING-INF/03 - TelecomunicazioniComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSSatellite communication systemsElastic proxy buffer managementLocal area networksReal time systemsAlgorithms; Buffer storage; Communication channels (information theory); Information retrieval; Internet; Local area networks; Multimedia systems; Railroad car equipment; Real time systems; Satellite communication systems; Satellite links; Wireless telecommunication systems; Delayed real time services; Elastic proxy buffer management; Fast internet for fast train hosts (FIFTH); Real time streaming services; Resource sharing algorithm; Vehicular area networks; Mobile computingComputer Science ApplicationsTerminal (electronics)Fast internet for fast train hosts (FIFTH)businessSatellite linksAlgorithmsMultimedia systemsComputer network
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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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