Dominique Gaïti

A survey of autonomic communications

Autonomic communications seek to improve the ability of network and services to cope with unpredicted change, including changes in topology, load, task, the physical and logical characteristics of the networks that can be accessed, and so forth. Broad-ranging autonomic solutions require designers to account for a range of end-to-end issues affecting programming models, network and contextual modeling and reasoning, decentralised algorithms, trust acquisition and maintenance---issues whose solutions may draw on approaches and results from a surprisingly broad range of disciplines. We survey the current state of autonomic communications research and identify significant emerging trends and techniques.

Performance management issues in ATM networks: traffic and congestion control

The goal is first to introduce performance monitoring aspects of asynchronous transfer mode (ATM) networks and then to focus on traffic and congestion control schemes. To deal with this performance monitoring management, a framework for defining a generic intelligent and integrated model for network management is described. As an example of the efficiency of this intelligent management architecture, we measure the performance of a new congestion control scheme. This scheme uses the cell loss priority (CLP) bit, the explicit forward congestion indicator and the explicit backward congestion indicator. The intelligent management uses different parameters and builds a complex but efficient control scheme. We show that this new control scheme allows performance to be increased by an order of magnitude.

A Survey and Synthesis of User Behavior Measurements in P2P Streaming Systems

In terms of scalability, cost and ease of deployment, the Peer-to-Peer (P2P) approach has emerged as a promising solution for video streaming applications. Its architecture enables end-hosts, called peers, to relay the video stream to each other. P2P systems are in fact networks of users who control peers. Thus, user behavior is crucial to the performance of these systems because it directly impacts the streaming flow. To understand user behavior, several measurement studies have been carried out over different video streaming systems. Each measurement analyzes a particular system focusing on specific metrics and presents insights. However, a single study based on a particular system and specific metrics is not sufficient to provide a complete model of user behavior considering all of its components and the impact of external factors on them. In this paper, we propose a comparison and a synthesis of these measurements. First of all, we review video streaming architectures, followed by a survey on the user behavior measurements in these architectures. Then, we gather insights revealed in these measurements and compare them for consensual and contrasting points. Finally, we extract components of user behavior, their external impacting factors and relationships among them. We also point out those aspects of user behavior which require further investigations.

Decentralized Aggregation Protocols in Peer-to-Peer Networks: A Survey

In large scale decentralized and dynamic networks such as Peer-to-Peer ones, being able to deal with quality of service requires the establishment of a decentralized, autonomous and efficient management strategy. In this context, there is a need to know the global state of a network by collecting a variety of distributed statistical summary information through the use of aggregation protocols. In this paper, we carried out a study on a set of aggregation protocols that can be used for autonomous network monitoring purposes in P2P networks, and we propose a classification and a comparison of them.

Haptic virtual environment performance over IP networks: a case study

This paper reports on the quality of service (QoS) requirements and the performance of virtual environment (VE) applications deployed in IP networks. We are interested specifically in systems that support communication with end-user through force feedback devices known as haptic interfaces. Little is known about networked haptic interfaces in VE. Our goal is to understand such application QoS requirements as well as the effect of other traffic when they co-exist in the same network. In this paper, we compare the peer-to-peer model with the client-server model. Our motivation is to deploy distributed haptic VE applications (DHVE) over a network connecting two departments of Queens University of Belfast. This deployment will be used for educational purposes and for implementing further research in this area, and will be evaluated by end-users; hence, the essential realization of network-based DHVE under realistic network conditions. A set of experiments was conducted to achieve this aim and their results are presented in this paper.

A Cooperative Multiagent Based Spectrum Sharing

A major issue in recent wireless networks is the static utilization and allocation of the available spectrum. An effective solution to this problem is to detect the empty spectrum portions using cognitive radio devices and to share them with the neighboring users, in a dynamic and distributed manner. However, since nodes generally have limited knowledge about their environment, we suggest that cooperative behavior can provide them with the necessary information in order to solve the global issues. To this extend, we develop a novel approach for spectrum allocation using multiagent system cooperation that enables cognitive radio (or secondary user) devices to utilize the amount of available spectrum, dynamically and opportunistically. The key aspect of our design is the deployment of agents on each of the primary and secondary user devices that cooperate in order to have a better use of the spectrum. For cooperation, contract net protocol is considered, allowing spectrum to be dynamically allocated by having a series of exchange of messages amongst the devices. Simulation results show that our approach achieves up to 80% of the whole utility within the span of few messages, and provides an effective mechanism for distributed spectrum allocation.

TCRA: a time-based channel reservation scheme for handover requests in LEO satellite systems

In this paper, we propose a time-based channel reservation algorithm (TCRA) suitable for handover and call admission control procedures in future mobile satellite systems. These systems are characterized by a high rate of handover attempts which can degrade significantly their performance. Therefore, we propose TCRA, a scheme which guarantees a null handover failure probability by using a channel reservation strategy in the cells to be crossed by the user. The performance of TCRA has been compared to the guaranteed handover (GH) scheme. The TCRA reservation method has the advantage of a better channel utilization by locking the resources only for their expected time of use. A mathematical model has been developed for both schemes, and its results have been validated through simulations.

An EAP-BT smartcard for authentication in the next generation of wireless communications

Wireless LANs based on the IEEE 802.11b have emerged as a new standard but still a lot of security issues remain. One of them issues is the authentication of a terminal to an access point (AP). The IEEE has released a secure architecture, IEEE 802.1x, based on the extensible authentication protocol (EAP). Similarly at the ETSI, the 3GPP has studied EAP to be used with Universal SIM (USIM) modules. In this paper, we propose an authentication architecture where smartcards play a key role.

A channel reservation algorithm for handover issues in LEO satellite systems based on a satellite-fixed cell coverage

In this paper, we propose a channel reservation mechanism referred to as time-based channel reservation algorithm (TCRA). The aim of TCRA is to handle the handover issue in low Earth orbit satellite networks. These systems face an important number of handover attempts due to the high satellite velocity when placed in low orbits. The TCRA scheme uses the deterministic satellite movement pattern to estimate the user residence time in each cell to be crossed. Two versions of the algorithm are proposed depending on whether the network disposes of a positioning system or not. These versions of TCRA allow to guarantee a null handover failure probability for the users. The performance of TCRA (with its two versions) is examined by simulations and compared to the guard channel scheme. The results show the behaviour of the schemes and their performance in terms of new call and handover blocking probabilities.

Crisis management using MAS-based wireless sensor networks

Wireless communication is increasingly used to manage large-scale crises (e.g., natural disasters or a large-scale city fire). Communication has traditionally been based on cellular networks. However, real-life experience has proven that the base stations of these networks may collapse or become unreachable during a crisis. An incident commander must also know as much information as possible about the occurring events to control them quickly and efficiently. This paper thus proposes a crisis management approach that overcomes the problems encountered by the base stations and insures relevant, rich and real-time information about events. This approach is based on wireless sensor networks, which are distributed in nature with no need for infrastructure and could be deployed in dangerous and inaccessible zones to gather information. Our proposal uses a multi-agent system as a software layer. The multi-agent system aims to improve the wireless sensor network performance by allowing cooperation between sensor nodes, offering better lifetime management and virtualizing the application layer. This virtualization supports several required applications simultaneously, including event monitoring and object tracking. Through successive simulations, we prove the importance of our approach in crisis management using several criteria to estimate the positions error in object tracking, end-to-end delay and wireless sensor network lifetime management.