Fanilo Harivelo

Using general public connected devices for disasters victims location

Information Technologies (IT) have largely contributed to improve disaster management by providing new means to acquire, process and broadcast information to the various actors. However, most of the work was targeted toward the risk experts: decision makers, rescue teams, firemen, etc. Nowadays, a new parallel trend seems to emerge: it consists in taking into account signal from consumer devices like cell phones (basic ones to smartphones), tablets, computers or other devices but light networks equipment (routers, WiFi access points) too. More particularly, our goal is to rely on the wave activity generated by those equipments, which are generally personal, to detect where victims are more likely to be located after a disaster, typically a seism. To reach this aim, we present the feasibility of mixing two approaches to acquire data by measuring their radio activity.

Transport congestion events detection (TCED): towards decorrelating congestion detection from TCP

TCP(Transmission Control Protocol) uses a loss-based algorithm to estimate whether the network is congested or not. The main difficulty for this algorithm is to distinguish spurious from real network congestion events. Other research studies have proposed to enhance the reliability of this congestion estimation by modifying the internal TCP algorithm. In this paper, we propose an original congestion event algorithm implemented independently of the TCP source code. Basically, we propose a modular architecture to implement a congestion event detection algorithm to cope with the increasing complexity of the TCP code and we use it to understand why some spurious congestion events might not be detected in some complex cases. We show that our proposal is able to increase the reliability of TCP NewReno congestion detection algorithm that might help to the design of detection criterion independent of the TCP code. We find out that solutions based only on RTT (Round-Trip Time) estimation are not accurate enough to cover all existing cases. Furthermore, we evaluate our algorithm with and without network reordering where other inaccuracies, not previously identified, occur.

An Architecture to Increase Performance of Self-Organizing Networks

The unpredictable variations of the characteristics of wireless and ad hoc networks make Quality of Service (QoS) support difficult. Wireless Mesh Networks constitute an alternative to provide QoS in an ad hoc network. This paper proposes a wireless mesh solution that reduces co-channel interference and simplifies both services and resources management. The architecture is based on a topology control or clustering scheme and a channel assignment mechanism. The network is organized hierarchically in order to obtain a seamless stable backbone. The clustering scheme aims to achieve a maximum number of covered nodes and a minimum hop count, while providing a topology minimizing co-channel interference by means of a channel assignment algorithm. Performance evaluation in NS-2 shows that resource management in a cluster can be uncoupled from that of neighboring clusters and that the network achieves improved performance compared to a classical ad hoc network.

Expedited forwarding for WiFi

It is essential to reserve resources in order to provide an acceptable quality of service in networks with real-time communication requirements. However, such reserved resources, e.g. bandwidth, may be unused as a consequence of the variations in the actual resource demands. Since bandwidth is scarce in wireless LANs (WLANs), QoS provisioning may be very expensive. Therefore, we propose a new resource management approach leading to a more efficient usage of the network in which communicating stations or end-users dynamically hand over some of the free resources temporarily to the other communication neighbors. This paper concentrates on two fundamental problems of such a demand-based sharing of resources: the current estimation of resource utilization, and the algorithm to share and redistribute resources with real-time requirements. This approach for resource and traffic management allows one to achieve significantly better utilization of network resources.

Enhancing Disaster Management by Taking Advantage of General Public Mobile Devices: Trends and Possible Scenarios

When a crisis occurs, particular infrastructures that are specific to the emergency situation are deployed in order to support rescue operations. Indeed, those normally used may have suffered from the disaster resulting in an altered service or may not be available at all. This process concerns physical (logistics) as well as immaterial (information) items delivery. Nowadays, special emphasis has been put on the latter as it has been proven that it is a major requirement to ensure that the former is realized properly and more generally to address the crisis. Generally, required information aims at answering the following basic questions: what (happened)? When (did it happened)? Where (is the disaster located)? And possibly, how (can it be reached)?

Achieving Fairness in IEEE 802.11 Ad Hoc Networks

This paper introduces a fair access method (FWM: Fair Wireless MAC) that is an extension of the original 802.11 DCF access method for ad hoc networks. A busy tone-like mechanism is coupled with carrier sensing in order to synchronize the state of neighboring nodes of a communication. By extending the knowledge of the neighborhood, the distributed contention resolution mechanism of 802.11 can apply again. This paper also deals with unfairness caused by wireless transmission

Table-driven geographical routing using aggregate areas

Geographical routing protocols scale well in large ad-hoc and sensor networks but fall short with some topologies. This causes packet losses and a drop in network performance. In this paper, we propose to introduce topological information aiming to improve the quality of routing decision while keeping the protocol scalable. Every node maintains precise information for nearby nodes and aggregated information for farther nodes by means of aggregate areas. Evaluation demonstrates the scalability of the proposition and its efficiency compared to a pure geographical routing protocol.

Hierarchical Area-Based Address Autoconfiguration Protocol for Self-organized Networks

Node autoconfiguration is one of the main issues in self-organized networks. One class of approaches relies on hierarchical organization of nodes. This kind of structuration aims to deal with scalability issues, especially for wireless networks. But building and maintaining a hierarchy is generally expensive for these resource-limited networks. We propose a low-cost distributed, hierarchical, location-based address autoconfiguration protocol. Each node infers its address from those of its one-hop neighbors and from its relative position to them. In this way we obtain a globally-consistent organization resulting from local interactions only. This reduces the latency and the overhead generated during address configuration. Moreover this scheme is the first step towards the design of a scalable routing protocol taking advantages of the proposed hierarchical addressing.

A robust service for delay sensitive applications on a WLAN

Technological advances in mobile terminals and the large spreading of Internet have led to the growing need of a certain level of a quality of service for the applications. Wireless networks characteristics make this task difficult. Thus, the classical protocols and models of QoS became inaccurate in this type of networks. This article presents a mechanism that guarantees a service corresponding to the Expedited Forwarding PHB (Per Hop Behavior) in a wireless network. Simulations under NS-2 are carried out to evaluate the performances of the solution.