Amalgamation of Transition Sequences in the PEPA Formalism

This report presents a proposed formal approach towards reduction of sequences in PEPA components. By performing the described amalgamation procedure we may remove, from the Markov chain underlying an initial PEPA model, those states for which detailed local balance equations cannot be formulated. This transformation may lead to a simpler model with product form solution. Some classes of reduced models preserve those performance measures which we are interested in and, moreover, the steady state solution vector is much easier to find from the computational point of view

Performance improvement of an optical network providing services based on multicast

Operators of networks covering large areas are confronted with demands from some of their customers who are virtual service providers. These providers may call for the connectivity service which fulfils the specificity of their services, for instance a multicast transition with allocated bandwidth. On the other hand, network operators want to make profit by trading the connectivity service of requested quality to their customers and to limit their infrastructure investments (or do not invest anything at all). We focus on circuit switching optical networks and work on repetitive multicast demands whose source and destinations are {\em \`a priori} known by an operator. He may therefore have corresponding trees "ready to be allocated" and adapt his network infrastructure according to these recurrent transmissions. This adjustment consists in setting available branching routers in the selected nodes of a predefined tree. The branching nodes are opto-electronic nodes which are able to duplicate data and retransmit it in several directions. These nodes are, however, more expensive and more energy consuming than transparent ones. In this paper we are interested in the choice of nodes of a multicast tree where the limited number of branching routers should be located in order to minimize the amount of required bandwidth. After formally stating the problem we solve it by proposing a polynomial algorithm whose optimality we prove. We perform exhaustive computations to show an operator gain obtained by using our algorithm. These computations are made for different methods of the multicast tree construction. We conclude by giving dimensioning guidelines and outline our further work.Comment: 16 pages, 13 figures, extended version from Conference ISCIS 201

Allocation équitable de ressources dans les réseaux ad hoc OFDMA

Session Posters & DemosInternational audienceLa technique de partage OFDMA permet d'allouer des ressources discrètes aux communications. Dans cet article, nous présentons un nouvel algorithme distribué d'allocation des Ressource Blocks dans un réseau ad hoc OFDMA. Nous considérons une allocation des ressources sur les liens et un modèle d'inter- férence à deux sauts. Les performances de notre algorithme sont évaluées par simulation et les résultats sont comparés à des bornes théoriques

Resource Allocation in Ad Hoc Networks with Two-Hop Interference Resolution

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A Composite Mobility Model for Ad Hoc Networks in Disaster Areas

Ad hoc network is an essential means of communication in disaster scenes. Validation of new communication protocols for these networks requires exhaustive simulation runs because real life experiences can be performed exclusively during expensive civil protection exercises. The necessity of these simulations calls for realistic and reliable mobility models which take into account numerous aspects of rescue worker interventions. We propose a composite model of mobility for disaster scenarii which includes a realistic model of human displacement, team mobility, and obstacle avoidance. The comparison of its performance with those of other available models is encouraging. We believe that it can improve the veracity of rescue operation simulations

Spatial Frequency Reuse in a Novel Generation of PMR Networks

International audiencePrivate Mobile Radio (PMR) networks are cellular infrastructures dedicated to be used by professionals, such as public safety, military, industry and transportation organizations. In those networks, resources are scarce, and there are strong Quality of Service (QoS) requirements. The emergence of new services which need more bandwidth has made the world PMR leader focus on the LTE-Advanced protocol. In order to ensure the QoS despite resource shortage, we propose an algorithm of Resource Blocks (RBs) allocation with spatial frequency reuse whose scheme takes into account users' (UEs') interference possibility and probability. We start by defining the underlying problem, which we call Weighted Fractional Coloring Problem (WFCP), in terms of graph theory. Next, we prove its NP-hardness. As obtaining an exact solution of such a problem in reasonable time is unrealistic, we propose a heuristic algorithm. In order to evaluate the performance of our algorithm we use a rigorous validation procedure. We compare its performance with that of a random one which we propose as a reference and the exact one which can be run on very small networks. Thanks to the results obtained we believe that the proposed algorithm can establish a solid starting point to conceive its distributed versions for novel PMR protocols