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Accueil > Équipes > METHODES > Séminaires Méthodes > Séminaires METHODES > Séminaires 2013 METHODES

Séminaire : 5 présentations

Séminaire : 5 présentations

lundi 27 mai de 9h45 à 12H30 en salle A004.

5 présentations.

Integer programming models for maximizing parallel transmissions in wireless networks

Professor Michal Pioro :

Department of Electrical and Information Technology

Lund University, Lund, Sweden ; Institute of Telecommunications

Warsaw University of Technology, Warsaw, Poland)

Abstract :

In radio communications, a set of links that can transmit in parallel with a tolera-ble interference is called a compatible set. Finding a compatible set with maximum weighted revenue of the parallel transmissions is an important subproblem in wire-less network management. For the subproblem, there are two basic approaches to express the signal to interference plus noise ratio (SINR) within integer programming, di_ering in the number of variables and the quality of the upper bound given by linear relaxations. To our knowledge, there is no systematic study comparing the effectiveness of the two approaches. The contribution of the paper is two-fold.

Firstly, we present such a comparison, and, secondly, we introduce matching inequalities improving the upper bounds as compared to the two basic approaches. The matching inequalities are generated within a branch-and-cut algorithm using a minimum odd-cut procedure based on the Gomory-Hu algorithm. The paper presents results of extensive numerical studies illustrating our statements and findings.

Scheduling Mechanisms for Energy Saving in Fixed-Mobile Networks

(Glenda GONZALEZ, Télécom SudParis )

Abstract :

Minimizing the use of transceivers of Optical Network Units (ONUs) is an effective approach for achieving minimum energy consumption in convergent access networks.

While synchronizing downstream and upstream ONUs transmissions can minimize the use of transceivers, and reduce the number of switches of these components, incurring in less consumed energy.

In this paper, we propose the synchronization of downstream traffic and upstream traffic to reduce the consumed energy in a fixed-mobileGEPON access network. Specifically, we present a novel synchronized downstream-upstream bandwidth allocation scheme for saving energy. Simulation results verify the proposed model and highlight the advantages of our scheme.

Title : Using Passive Testing based on Symbolic Execution and Slicing techniques : Application to the Validation of Communication Protocols

Presented by : Pramila Mouttappa, Télécom SudParis

Abstract :

Our work is based on a new approach to perform passive testing based on the analysis of the control and data part of the system under test. Passive testing techniques are based on the observation and verification of properties on the behavior of a system without interfering with its normal operation. Many passive testing techniques consider only the control part of the system and neglect data, or are confronted with an overwhelming amount of data values to process. In our approach, we consider control and data parts by integrating the concepts of symbolic execution and we improve trace analysis by introducing trace slicing techniques. Properties are described using Input-Output Symbolic Transition Systems (IOSTS) and we illustrate in our work how they can be tested on real execution traces optimizing the trace analysis. These properties can be designed to test the functional conformance of a protocol as well as security properties. In addition to the theoretical approach, we have developed a software tool that implements the algorithms presented in this paper. Finally, as a proof of concept of our approach and tool we have applied the techniques to a real-life case study : the SIP protocol. In particular, the proposed techniques are applied to a set of real execution traces extracted from IMS/SIP architecture.

Title : Network performance under general traffic

by : Hind Castel, Télécom SudParis
Abstract :

We propose to use stochastic bounds for histograms characterization of general network traffic. We apply an algorithm based on dynamic programming in order to derive a bounding traffic histogram on a reduced state space. The goals are to obtain an easier bounding stochastic process working with histograms for network performance analysis. The results of this process are stochastic upper and lower bound buffer occupancy histogram (queue length distribution) using a finite queue model. From this buffer occupancy histogram, we detail how to obtain another interesting performance parameters like blocking probability and buffer length distribution. The proposed methods have been extensively evaluated using real traffic traces with self similar behavior.

Numerical results show that the method provides an interesting solution as a trade-off
between computation time and accuracy of results. Applications could be very relevant in network dimensioning for QoS (Quality of Service) guarantees.

Title : Resource Optimization in Localized SC-FDMA Systems

By Faiz Hamid, Télécom SudParis

Abstract :

In this paper we study the problem of resource allocation in SC-FDMA system which is adopted as the multiple access scheme for the uplink in the 3GPP-LTE standard. A sum utility maximization is considered where the utility of each user may be neither additive nor super additive. Unlike OFDMA, in addition to the restriction of allocating a sub-channel to at most one user, the multiple sub-channels allocated to a user in SCFDMA must be consecutive. This makes the resource allocation

problem prohibitively difficult and challenging. We provide a fundamental complexity analysis of the optimization problem for general non additive utility functions and show that not only the problem is NP-hard but also approximating it by a factor better than 2011/2012 is not possible unless P=NP. We then provide an efficient cutting plane algorithm and also develop

five suboptimal heuristics that can achieve a solution close to the optimum in different scenarios. Computational results of the cutting plane and heuristic algorithms are reported in the paper and a comparison between these heuristics in terms of sub-optimality gap and complexity is provided as well.

Contact : Walid Ben Ameur