6,019 research outputs found

    Reliable Video Streaming over mmWave with Multi Connectivity and Network Coding

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    The next generation of multimedia applications will require the telecommunication networks to support a higher bitrate than today, in order to deliver virtual reality and ultra-high quality video content to the users. Most of the video content will be accessed from mobile devices, prompting the provision of very high data rates by next generation (5G) cellular networks. A possible enabler in this regard is communication at mmWave frequencies, given the vast amount of available spectrum that can be allocated to mobile users; however, the harsh propagation environment at such high frequencies makes it hard to provide a reliable service. This paper presents a reliable video streaming architecture for mmWave networks, based on multi connectivity and network coding, and evaluates its performance using a novel combination of the ns-3 mmWave module, real video traces and the network coding library Kodo. The results show that it is indeed possible to reliably stream video over cellular mmWave links, while the combination of multi connectivity and network coding can support high video quality with low latency.Comment: To be presented at the 2018 IEEE International Conference on Computing, Networking and Communications (ICNC), March 2018, Maui, Hawaii, USA (invited paper). 6 pages, 4 figure

    Incorporating project uncertainty in novel environmental biotechnologies: illustrated using phytoremediation

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    "Pollution of the environment by metals and organic contaminants is an intractable global problem, with cleanup costs running into billions of dollars using current engineering technologies. The availability of alternative, cheap and effective technologies would significantly improve the prospects of cleaning-up metal contaminated sites. Phytoremediation has been proposed as an economical and ‘green' method of exploiting plants to extract or degrade the contaminants in the soil. To date, the majority of phytoremediation efforts have been directed at leaping the biological, biochemical and agronomic hurdles to deliver a working technology, with scant attention to the economic outlook other than simple estimates of the cost advantages of phytoremediation over other techniques. In this paper we use a deterministic actuarial model to show that uncertainty in project success (the possibility that full clean up may not be realized) may significantly increase the perceived costs of remediation works for decision-makers." Authors' Abstractbiotechnology, Soil contaminants, Environmental remediation Economic aspects, Industrial crop technologies,

    Estimating Self-Sustainability in Peer-to-Peer Swarming Systems

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    Peer-to-peer swarming is one of the \emph{de facto} solutions for distributed content dissemination in today's Internet. By leveraging resources provided by clients, swarming systems reduce the load on and costs to publishers. However, there is a limit to how much cost savings can be gained from swarming; for example, for unpopular content peers will always depend on the publisher in order to complete their downloads. In this paper, we investigate this dependence. For this purpose, we propose a new metric, namely \emph{swarm self-sustainability}. A swarm is referred to as self-sustaining if all its blocks are collectively held by peers; the self-sustainability of a swarm is the fraction of time in which the swarm is self-sustaining. We pose the following question: how does the self-sustainability of a swarm vary as a function of content popularity, the service capacity of the users, and the size of the file? We present a model to answer the posed question. We then propose efficient solution methods to compute self-sustainability. The accuracy of our estimates is validated against simulation. Finally, we also provide closed-form expressions for the fraction of time that a given number of blocks is collectively held by peers.Comment: 27 pages, 5 figure

    How user throughput depends on the traffic demand in large cellular networks

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    Little's law allows to express the mean user throughput in any region of the network as the ratio of the mean traffic demand to the steady-state mean number of users in this region. Corresponding statistics are usually collected in operational networks for each cell. Using ergodic arguments and Palm theoretic formalism, we show that the global mean user throughput in the network is equal to the ratio of these two means in the steady state of the "typical cell". Here, both means account for double averaging: over time and network geometry, and can be related to the per-surface traffic demand, base-station density and the spatial distribution of the SINR. This latter accounts for network irregularities, shadowing and idling cells via cell-load equations. We validate our approach comparing analytical and simulation results for Poisson network model to real-network cell-measurements

    Development of a BIM-based simulator for workspace management in construction

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    openNei cantieri edili, quali contesti altamente dinamici, lo spazio richiesto dalle attività muta continuamente evidenziando la necessità di considerarlo come una risorsa limitata. Ad oggi, le aree di lavoro non sono efficacemente gestite né dalle tecniche tradizionali di pianificazione né dagli strumenti 4D più avanzati. I manager del processo costruttivo sono costretti a condurre considerazioni spaziali manualmente sulla base di schizzi 2D. Tale approccio è altamente dispendioso e soggetto ad errori; inoltre, come dimostrano le statistiche, è una delle principali cause di infortuni e riduzione della produttività. Questa tesi di dottorato affronta il problema della gestione delle aree di lavoro, proponendo un approccio che integra la fase di pianificazione con la verifica delle interferenze, condotta da un simulatore spaziale sviluppato in un motore grafico. Tale simulatore, acquisiti il modello BIM ed il cronoprogramma, individua eventuali conflitti spaziali quale risultato di computazioni geometriche e simulazioni fisiche. La criticità dei conflitti viene stimata mediante inferenza Bayesiana al fine di escludere scenari trascurabili. Successivamente, i manager del processo costruttivo, consapevoli dei possibili conflitti spaziali futuri, modificano o confermano il cronoprogramma. Questo approccio può essere applicato per identificare i conflitti spaziali sia durante la fase di pianificazione che quella di esecuzione dei lavori. In questa tesi, il simulatore spaziale proposto è stato validato con riferimento alla fase di pianificazione dei lavori di un edificio reale. I risultati hanno dimostrato la sua capacità di identificare non solo un maggior numero di conflitti, rispetto agli strumenti dello stato dell’arte, ma anche di stimare il relativo livello di criticità evitando sovrastime. In futuro, l’approccio proposto in questa tesi, adattato con minime integrazioni, potrà essere applicato a runtime per aggiornare il cronoprogramma durante l’esecuzione dei lavori.In the AEC industry, construction sites are very dynamic operating environments. Activities workspace demand continuously changes across space demanding and time, stressing the need to consider the space as a limited and renewable resource. This issue has not been fully handled yet, neither by traditional scheduling techniques nor by more advanced 4D tools. For these reasons, construction management teams usually carry out manually spatial considerations based on 2D sketches. This approach, especially in big construction projects, is highly time-demanding and error-prone causing, as demonstrated by statistics, injuries, and productivity slowdown. To cover these gaps, this study proposes a workspace management framework that integrates the work scheduling phase with spatial analysis, carried out by a spatial conflict simulator developed using a serious game engine. The simulator, given the BIM model and the construction work schedule, can detect eventual spatial interferences based on geometric computations and physics simulations. The detected conflicts are then judged applying Bayesian inference to filter non-critical scenarios and avoid overestimation. Afterwards, the construction management team, made aware of likely future spatial issues, can adjust or confirm the work schedule. This approach can provide a valuable contribution in detecting spatial conflicts during both the construction planning phase and works execution. In this study, the proposed spatial conflict simulator has been validated on the planning phase of a real use case, demonstrating its capability to not only detect an increased number of spatial issues, compared to the state-of-the-art tools, but also to esteem related criticality levels and avoid overestimations. In the future, the proposed approach, adapted with minor changes, can be applied at runtime for proactively refining the work schedule during works execution.INGEGNERIA CIVILE, AMBIENTALE, EDILE E ARCHITETTURAopenMessi, Leonard

    Evaluation of probabilistic constellation shaping performance in Flex Grid over multicore fiber dynamic optical backbone networks [Invited]

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    In this paper, we present a worst-case methodology for estimating the attainable spectral efficiency over end-to-end paths across a Flex Grid over multicore fiber (MCF) optical network. This methodology accounts for physical link noise, as well as for the signal-to-noise ratio in the Add module (SNR TX ) of spatial-division-multiplexing-enabled reconfigurable optical add and drop multiplexers (SDM-ROADMs), introducing a dominant noise contribution over that of their Bypass and Drop modules. The proposed methodology is subsequently used to quantify the benefits that probabilistic constellation shaping (PCS) can bring to Flex-Grid/MCF dynamic optical backbone networks, compared to using traditional polarization-multiplexed modulation formats. In a first step, insight is provided into the spectral efficiency attainable along the precomputed end-to-end paths in two reference backbone networks, either using PCS or traditional modulation formats. Moreover, in each one of these networks, two SNR TX values are identified: the SNR TX yielding the maximum average paths’ spectral efficiency, as well as an SNR TX that, although slightly degrading the average paths’ spectral efficiency (by 10%), would yet enable a cost-effective SDM-ROADM Add module implementation. Extensive simulations are conducted to analyze PCS offered load gains under 1% bandwidth blocking probability. Furthermore, the study lastly focuses on finding out whether lower fragmentation levels in Flex-Grid/MCF dynamic optical backbone networks can push PCS benefits even further.Funding: Agencia Estatal de Investigación (PID2020-118011GB-C21, PID2020-118011GB-C22, RED2018-102585-T).Peer ReviewedPostprint (author's final draft
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