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Browsing by Author "Ribeiro, Nuno"

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  • Modelling spreading process of a wildfire in heterogeneous orography, fuel distribution and environmental conditions - a complex networks approach
    Publication . Perestrelo, Sara; Grácio, Maria; Ribeiro, Nuno; Lopes, Luís
    Forest fires are phenomena that represent a great danger for the population and have severe environmental consequences. The greatest efforts in regard to direct confrontation require a large investment in terms of both financial and human resources, partly due to the unpredictability of fire behaviour and the fuel distribution that feeds its growth and spread. To deal with this unpredictability in a more efficient manner, our work focuses around the establishment of an optimal fire-break structure whose purpose is to block the spread along the landscape, at a minimal cost. It’s a preventative approach, which acts as a complement to direct confrontation and contributes to the reduction of material, economic and human losses. For the establishment of this optimal fire-break structure it is necessary to model fire spreading process and, for that, we use the multilayer network model, within the area of complex networks. We aim the construction of a network of networks that allows us to simulate the fire spreading process both at a local scale and at a more global scale.
    2020-09Conference object Open access Show more
  • A SON Enhanced Algorithm for Observed Time Differences Based Geolocation in Real 3G Networks
    Publication . Vieira, Pedro; Varela, Nuno; Fernandes, Nuno; Guedes, Nuno; Varela, Luis; Ribeiro, Nuno
    This paper presents a SON enhanced approach for OTD Based Geolocation in a real 3G UMTS Network. The algorithm was implemented using cell, measurement report and drivetest data, the last just for geolocation accuracy determination. It uses a dual convergence approach evolving Node B time reference estimation followed by trilateration, boosting convergence. A motion model Kalman filtering module was developed, and tuned for urban mobile. Around 35% of the events were geopositioned, which motivates using OTD measurements for geolocation in live networks. The median accuracy achieved by the algorithm was 178 m, which is rather promising, considering that OTD measurements have an intrinsic uncertainty of a UMTS chip, i.e, 78 m.
    2013Conference object Metadata only Show more