Eric Fleury

Self-stabilization in self-organized multihop wireless networks

In large scale multihop wireless networks, flat architectures are not scalable. In order to overcome this major drawback, clusterization is introduced to support self-organization and to enable hierarchical routing. When dealing with multihop wireless networks, the robustness is a main issue due to the dynamicity of such networks. Several algorithms have been designed for the clustering process. As far as we know, very few studies check the robustness feature of their clustering protocols. In this paper, we show that a clustering algorithm, that seems to present good properties of robustness, is self-stabilizing. We propose several enhancements to reduce the stabilization time and to improve stability. The use of a directed acyclic graph ensures that the self-stabilizing properties always hold regardless of the underlying topology. These extra criterion are tested by simulations.

On the performance and feasibility of multicast core selection heuristics

A core-based forwarding multicast protocol uses a core router as a traffic transit center: all multicast packets are first sent to the core, then distributed to destinations on a multicast tree rooted at the core. The purpose of this paper is to evaluate, via simulation, the effect of various core selection methods on multicast performance. The main contribution of this work is the discovery of a simple yet effective core selection heuristic that can be implemented in a wide range of networks. Specifically, our results show that the tree center heuristic (using the center of the existing multicast tree as the new core node) significantly outperforms heuristics based on random selection, and performs as well as heuristics that are more computationally expensive.

Triangles to Capture Social Cohesion

Although community detection has drawn tremendous amount of attention across the sciences in the past decades, no formal consensus has been reached on the very nature of what qualifies a community as such. In this article we take an orthogonal approach by introducing a novel point of view to the problem of overlapping communities. Instead of quantifying the quality of a set of communities, we choose to focus on the intrinsic community-ness of one given set of nodes. To do so, we propose a general metric on graphs, the cohesion, based on counting triangles and inspired by well established sociological considerations. The model has been validated through a large-scale online experiment called Fellows in which users were able to compute their social groups on Face book and rate the quality of the obtained groups. By observing those ratings in relation to the cohesion we assess that the cohesion is a strong indicator of users subjective perception of the community-ness of a set of people.

SCILAB to SCILAB // : the Ouragan project

In this paper, we present the developments realized in the Ouragan project around the parallelization of a Matlab-like tool called Scilab. These developments use high-performance numerical libraries and different approaches based either on the duplication of Scilab processes or on computational servers. This tool, Scilab//, allows users to perform high-level operations on distributed matrices in a metacomputing environment. We also present performance results on different architectures.

No administration protocol (NAP) for IPv6 router auto-configuration

This paper outlines the concept of auto-organization in IPv6 networks. If the auto-configuration of hosts is defined by IPv6 and mandatory, these mechanisms can not be assimilated to a fully plug and play feature as IPv6 routers still have to be manually configured. In order to succeed in new domains such as SOHO, a full auto-configuration feature must be offered. Indeed, the configuration of 64 bits IPv6 prefixes and the numbering of links are not really friendly and are error prone especially in home networking. This paper tackles the issues that arise, reviews actual solutions and proposes a totally distributed protocol named NAP for IPv6 routers auto-configuration.

Measurement Analysis of the Live E! Sensor Network: Spatial-Temporal Correlations and Data Aggregation

The (Japanese) Live E! project consists of a large sensor network of spatially distributed weather stations measuring different environmental quantities such as temperature, humidity, pressure, etc. Our goal is to conduct the first analysis on this huge data set of the structures of correlations both in time and space observed on data, for given quantity among stations, and for a given station, among sensors. Finally, we investigate a data aggregation algorithm, based on polynomial regression, and we show how it can reduce significatively the overall data traffic.

A fully distributed mediator based service location protocol in ad hoc networks

With the increasing number of Internet services, extensive research on service location protocols is an essential feature for future networks. In this paper, we discuss a service location and declaration protocol in ad hoc wireless environments. Our on demand protocol is based on a distributed approach which contributes to overhead optimization. The main features of our protocol are: overhead minimization, minimizing the time spent to respond to a client request, increasing the probability a client is served by the nearer service and its independence from the underlying protocols.

On the Structure of Changes in Dynamic Contact Networks

We present a methodology to investigate the structure of dynamic networks in terms of concentration of changes in the network. We handle dynamic networks as series of graphs on a fixed set of nodes and consider the changes occurring between two consecutive graphs in the series. We apply our methodology to various dynamic contact networks coming from different contexts and we show that changes in these networks exhibit a non-trivial structure: they are not spread all over the network but are instead concentrated around a small fraction of nodes. We compare our observations on real-world networks to three classical dynamic network models and show that they do not capture this key property.

Lower and Upper Bounds for Minimum Energy Broadcast and Sensing Problems in Sensor Networks

In this paper, we study the problem of power transmission and sensing ranges assignment wireless sensor network nodes so that to minimize power consumption while ensuring broadcasting task or sensing process. A first novelty is that our model takes into account both the transmission and the reception costs when evaluating the energy consumption of a broadcasting task. We establish a new analytical model and derive lower and upper bounds on region covering. Moreover, we show that the lower bound is asymptotically optimal and can be approached up to epsi

Ananas: a local area ad hoc network architectural scheme

We present an architecture for ad hoc networks: Ananas. Based on the combined use of a classical ad hoc routing protocol and virtual ad hoc interfaces, Ananas allows a complete support for the IP protocol over ad hoc networks, including auto-configuration mechanisms such as the IPv6 one or DHCP. It also provides Internet connectivity and compatibility with Internet services and protocols such as multicast. Finally Ananas addresses problems of scalability and ad hoc network partitioning and provides very good performance results.