François Spies

Impact of radio propagation models in vehicular ad hoc networks simulations

Vehicular ad hoc networks use new protocols to enable security, services and other inventive applications to be run onboard many types of vehicles. In their design phase, those protocols and applications need to be extensively simulated but most of the work in the simulator field concentrates on the medium access and higher layer protocols. In this paper, through real world experimentations we first characterize the behavior of the channel regarding losses, we deduce a set of properties needed for lightweight models still producing relevant results. Then we implement them in a model we called shadowing-pattern which we finally use in a VANET distinctive scenario where it considerably modifies the results of a data propagation application.

A Friis-based calibrated model for WiFi terminals positioning

Two types of applications use indoor positioning, services linked with mobility, such as guided tour or meeting systems, and the active security of a wireless network which locates intrusive unauthorized mobile terminals. Indoor positioning cannot be managed by a geostationary system like GPS. In fact, current researches are being conducted to conceive indoor positioning using wireless networks such as WiFi. We study such a mechanism and compare the accuracy of our results to other solutions. Our model is based on the Friis relation, which expresses signal strength as a function of distance, in a free space environment. The Friis-based model is adapted to fit the conditions of implementation. The positioning function is combined with a mobility prediction mechanism and constitutes the mobility service in a video on demand system called MoVie (mobile video).

Indoor Wi-Fi positioning: techniques and systems

If outdoor positioning is widely treated and quite precise, positioning indoors or, more generally, in heterogeneous environments, as well as mobility prediction, requires important devices. New wireless technologies (e.g., Wi-Fi, Ultra Wide Band) combine the mobility of terminals with large bandwidth. Terminal mobility is one of the major pillars of applications attempting to become context-aware, and a large bandwidth enables new services such as multimedia contents streaming towards mobile terminals. Being context-aware and able to provide services in a mobile environment requires the knowledge of spatial and temporal data about the terminal. The key phase in the achievement of mobility management is the positioning process. We propose a layered positioning system based on a model combining a reference point-based approach with a trilateration-based one. Several layers of refinement are offered based on the knowledge of the topology and devices deployed. The more data are known, the better adapted to its area the positioning system can be.

A global security architecture for intrusion detection on computer networks

Detecting all kinds of intrusions efficiently requires a global view of the monitored network. Built to increase the security of computer networks, traditional IDSs are unfortunately unable to give a global view of the security of a network. To overcome this situation, we are developing a distributed SOC (Security Operation Center) which is able to detect attacks occurring simultaneously on several sites in a network and to give a global view of the security of that network. In this article, we present the global architecture of our system, called DSOC as well as several methods used to test its accuracy and performance.

Wi-Fi-based indoor positioning: Basic techniques, hybrid algorithms and open software platform

In urbanized and indoor environments, outdoor positioning systems, such as Global Navigation Satellite Systems (GNSSs), are often inaccurate and adaptations of such systems to those contexts are expensive and hard to deploy. Nowadays, a lot of indoor positioning techniques have been studied, but it it quite difficult to objectively evaluate and compare their accuracies in the same environment.

Open Wireless Positioning System: A Wi-Fi-Based Indoor Positioning System

Wireless network positioning is the main pillar of the continuity of rich and mobile multimedia applications. Good position accuracy is particularly difficult to obtain in urban or leafy areas and indoors or in mixed (both indoor and outdoor) environments. A system proposing such positioning must localize any mobile terminal accurately within hostile environments and ideally be low-cost and easy to deploy. We propose an indoor positioning system, based on the IEEE 802.11 wireless network. This system, named OWLPS (Open WireLess Positioning System), implements several of the major mobile position computation algorithms and techniques: fin- gerprinting location, topology-based and viterbi-like algorithm, propagation models. These algorithms result from community work and our personal researches. Index Terms—Wireless LAN, Radio position measurement, Indoor radio communication

WiFi GPS based combined positioning algorithm

If nowadays, positioning becomes more and more accurate, and covers better and better a territory (indoor and outdoor), it remains territories where traditional (and basic) positioning system (GPS, gsm or WiFi) and hybrid ones (GPS- gsm, GPS-WiFi, GPS-WiFi-gsm, …) are insufficient and requires research investment treating combined positioning. In this paper we propose a GPS-WiFi combined positioning algorithm, based on trilateration technique. Real experiments and other simulation are conduced and demonstrate accuracy gains, even where various criteria dilution of precision (GPS dops criteria, or ours WiFi geometrical and signal attenuations dop proposal, or hybrid dop ones) indicate all the disruption of positioning service. A testbed scenario issued from a real urban campus environment validates not only our GPS-WiFi combined positioning algorithm but also an implementation of pertinent positioning techniques and dops criteria. This work constitutes a further step to better position everywhere and to ensure continuity of a positioning service.

Using an evolutionary algorithm to optimize the broadcasting methods in mobile ad hoc networks

A mobile ad hoc network (MANET) is a collection of mobile nodes communicating through wireless connections without any prior network infrastructure. In such a network the broadcasting methods are widely used for sending safety messages and routing information. To transmit a broadcast message effectively in a wide and high mobility MANET (for instance in vehicular ad hoc network) is a hard task to achieve. An efficient communication algorithm must take into account several aspects like the neighborhood density, the size and shape of the network, the use of the channel. Probabilistic strategies are often used because they do not involve additional latency. Some solutions have been proposed to make their parameters vary dynamically. For instance, the retransmission probability increases when the number of neighbors decreases. But, the authors do not optimize parameters for various environments. This article aims at determining the best communication strategies for each node according to its neighborhood density. It describes a tool combining a network simulator (ns-2) and an evolutionary algorithm (EA). Five types of context are considered. For each of them, we tackle the best behavior for each node to determine the right input parameters. The proposed EA is first compared to three EAs found in the literature: two well-known EAs (NSGA-II and SPEA2) and a more recent one (DECMOSA-SQP). Then, it is applied to the MANET broadcasting problem.

A Global Security Architecture for Intrusion Detection on Computer Networks

Detecting all kinds of intrusions efficiently requires a global view of the monitored network. Built to increase the security of computer networks, traditional IDS are unfortunately unable to give a global view of the security of a network. To overcome this situation, we are developing a distributed SOC (security operation center) which is able to detect attacks occurring simultaneously on several sites in a network and to give a global view of the security of that network. In this article, we present the global architecture of our system, called DSOC as well as several methods used to test its accuracy and performance.

Video transmission adaptation on mobile devices

The development of multimedia streaming over wireless network is facing a lot of challenges. Taking into account mobility and highly variable bandwidth are the two major ones. Using scalable video content can solve the variable bandwidth problem only if the streaming architecture is able to react without latency. In this article, we present NetMoVie, an intermediate architecture based on real-time protocol which is able to adapt streams to the constraints of the wireless channel.