SAMOVAR UMR 5157

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Séminaire : GT "Performances, QoS et gestion de ressources des réseaux sans fil dynamiques"

Séminaire : GT "Performances, QoS et gestion de ressources des réseaux sans fil dynamiques"

Vendredi 19 juin après-midi

Session du Groupe de Travail DigiCosme

"Performances, QoS et gestion de ressources des réseaux sans fil dynamiques"

Lieu : Amphi 34, bâtiment 862 – NanoInnov

Avenue de la Vauve

91120 PALAISEAU

(GPS : N. 48°42,7575’, E. 02°11,5228’)

Entrée libre

14h00-14h45 : Marco Fiore, CNR Italie - Titre : Road traffic modeling with an eye to networking applications

The performance of protocols and architectures for upcoming connected vehicles are commonly investigated by means of computer simulations, due to the excessive cost and complexity of large-scale experiments. Dependable and reproducible simulations are thus paramount to a proper evaluation of vehicular networking solutions. Yet, we lack today a reference dataset of vehicular mobility scenarios that are realistic, publicly available, heterogeneous, and that can be used for networking simulations straightaway. In this talk, we present several contributions to the development of such a reference dataset, including (i) original synthetic traces that are generated from reliable sources, (ii) validation methodologies, and (iii) assessments of the potential impact of the traces on networking studies.

14h45-15h30 : Alexandre Mouradian, L2S Université Paris Sud - Titre : Study of Probabilistic Worst Case Inter-Beacon Delays Under Realistic Vehicular Mobility Conditions

Road safety applications are one of the main incentives to deploy vehicular networks. These applications rely on periodic message exchange among vehicles (known as beaconing). The beacon messages contain information about the environment which is used to perceive dangerous situations and alert the drivers. The inter-beacon delay is the time between two consecutive beacons received from a car. It is an essential parameter because, if this delay exceeds the application requirement, the application cannot accurately predict dangerous situations and alert the drivers on time. The worst case inter-beacon delay has thus to be bounded according to the application requirements. Unfortunately, a tight and strict bound is in fact very difficult to obtain for a real network because of the randomness of the collisions among beacons coming from : the unpredictable mobility patterns, random interferences, randomness of the MAC layer backoff, etc.
We propose to provide a probabilistic worst-case of the inter-beacon delay under realistic mobility using Extreme Value Theory (EVT). EVT provides statistical tools which allow to make predictions on extreme deviations from the average of a parameter. These statistical predictions can be made based on data gathered from simulation or experimentation. We first introduce the EVT technique. Then we discuss its application to the study of inter-beacon delays. Finally, we apply EVT on the results of extensive vehicular network simulation using a realistic mobility trace : the Cologne trace.

15h30-16h15 : Michel Marot, Telecom SudParis - Titre : On the Maximal Shortest Path in a Connected Component in V2V

We consider a VANET (Vehicular Ad-hoc NETwork) in a simple lane, without infrastructure. The arrivals of vehicles are assumed to be general with any traffic and speed assumptions. The vehicles communicate through the shortest path. We present results on the probability distribution of the number of hops on the maximal shortest path in a connected component of vehicles. The general formulation is given for any assumption of road traffic. Then, it is applied to calculate the z-transform of this distribution for medium and dense networks in the Poisson case. Our model is validated with the Madrid road traces of the Universitat Polit\`ecnica de Catalunya. These results may be useful for example when evaluating diffusion protocols through the shortest path in VANET, where not only the mean but also the other moments are needed to derive accurate results.