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showing 10 items of 2452 documents

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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Correlated channel model for terrestrial Free Space Optics: performance analysis of rateless codes

2012

We describe a novel correlated channel model able to predict random temporal fluctuations of optical signal irradiance caused by scintillation. With regards to the same channel, we also report simulation results on the error mitigation performance of Luby-Transform and Raptor codes.

Settore ING-INF/03 - TelecomunicazioniFree Space Optics channel modeling Raptor codes RaptorQ codes LT codes rateless codesSettore ING-INF/02 - Campi ElettromagneticiSettore ING-INF/01 - Elettronica
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Flexible and Modular Support for Multicast Rate Adaptation in WLANs

2013

The flexibility and virtualization capabilities provided by wireless cards have received significant attention as a means to reduce development costs. In this paper we present a modular architecture that exploits the features provided by emerging PHY and MAC implementations to rapidly develop new rate adaptation algorithms for multicast trans- mission in wireless LANs. We validate our solution by developing three rate adapta- tion algorithms that use an innovative sensing mechanism to evaluate the frame recep- tion correlation of the members of the multicast group. The experimental results obtained on a real-life testbed show that our solutions permit to increase the performance of multicas…

Settore ING-INF/03 - TelecomunicazioniMulticast Rate Adaptation Multimedia Communication Wireless MAC Processor Wireless LAN
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Luby Transform Performance Tests on Time-Correlated Channel Model for Geo Free Space Optics Downlinks

2012

Settore ING-INF/03 - TelecomunicazioniSettore ING-INF/01 - ElettronicaFree Space Optics Luby Transform Codes Rateless Codes Channel Modeling Geo Free Space Optics Downlinks
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Performance Investigation of Fountaine Codes on a Simulated Terrestrial Free Space Optical Channel

2012

Settore ING-INF/03 - TelecomunicazioniSettore ING-INF/02 - Campi ElettromagneticiSettore ING-INF/01 - ElettronicaFree Space Optics Channel Modeling Fountain Codes Raptor Codes RaptorQ Codes Luby Transform Codes Rateless Codes
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Optical wireless GEO satellite-to-ground downlinks: rateless codes as solution for scintillation fading

2013

Scintillation fading can corrupt a satellite-to-ground optical wireless links with burst errors. Rateless codes, suitable for erasure channel, are able to eliminate or to reduce these communication errors. We analyzed the performances of three different rateless codes in a simulated Geo satellite-to-ground downlink.

Settore ING-INF/03 - TelecomunicazioniSettore ING-INF/02 - Campi ElettromagneticiSettore ING-INF/01 - ElettronicaFree Space Optics Rateless codes LT codes Raptor codes RaptorQ codes channel modeling
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Fading mitigation coding techniques for space to ground free space optical communications

2014

Settore ING-INF/03 - TelecomunicazioniSpace-to-Ground FSO links time-series rateless codefading mitigationSettore ING-INF/02 - Campi ElettromagneticiOptical Wireless CommunicationSettore ING-INF/01 - Elettronica
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Supporting code mobility and dynamic reconfigurations over Wireless MAC Processor Prototype

2014

Mobile networks for Internet Access are a fundamental segment of Internet access net- works, where resource optimization are really critical because of the limited bandwidth availability. While traditionally resource optimizations have been focused on high effi- cient modulation and coding schemes, to be dynamically tuned according to the wireless channel and interference conditions, it has also been shown how medium access schemes can have a significant impact on the network performance according to the application and networking scenarios. This thesis work proposes an architectural solution for supporting Medium Access Con- trol (MAC) reconfigurations in terms of dynamic programming and c…

Settore ING-INF/03 - TelecomunicazioniWireless MAC Processor Software Defined Network Network Programmability Cognitive Network
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Channel estimation and transmit power control in wireless body area networks

2015

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements u…

Settore ING-INF/03 - Telecomunicazionibusiness.industryComputer scienceTKWireless Body area Newtork; WBAN; TPCTransmitter power outputIndustrial and Manufacturing EngineeringReturn channelTest caseBody area networkElectronic engineeringWirelessSuperframeTPCWBANWireless Body area NewtorkbusinessFade marginComputer networkPower controlIET Wireless Sensor Systems
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MAC design on real 802.11 devices: From exponential to Moderated Backoff

2016

In this paper we describe how a novel backoff mechanism called Moderated Backoff (MB), recently proposed as a standard extension for 802.11 networks, has been prototyped and experimentally validated on a commercial 802.11 card before being ratified. Indeed, for performance reasons, the time critical operations of MAC protocols, such as the backoff mechanism, are implemented into the card hardware/firmware and cannot be arbitrarily changed by third parties or by manufacturers only for experimental reasons. Our validation has been possible thanks to the availability of the so called Wireless MAC Processor (WMP), a prototype of a novel wireless card architecture in which MAC protocols can be p…

Settore ING-INF/03 - Telecomunicazionibusiness.industryFirmwareWireless ad hoc networkComputer scienceComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS05 social sciences050801 communication & media studies020206 networking & telecommunicationsTime critical02 engineering and technologyDistributed coordination functioncomputer.software_genreExponential functionComputer Networks and Communication0508 media and communicationsFormal languageMedia Technology0202 electrical engineering electronic engineering information engineeringWirelessbusinesscomputerComputer network2016 IEEE 17th International Symposium on A World of Wireless, Mobile and Multimedia Networks (WoWMoM)
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