Issam Mabrouki

Design and performance of wireless data gathering networks based on unicast random walk routing

Wireless environment monitoring applications with significantly relaxed quality-of-service constraints are emerging. Hence, the possibility to use rough low knowledge routing in sensor networks to reduce hardware resource and software complexity is questionable. Moreover, low knowledge handling allows better genericity, which is of interest, for instance, for basic operation enabling system set-up. In this framework, this paper revisits stateless unicast random walk routing in wireless sensor networks. Based on random walk theory, original closed-form expressions of the delay, the power consumption and related spatial behaviors are provided according to the scale of the system. Basic properties of such a random routing are discussed. Exploiting its properties, data gathering schemes that fulfill the requirements of the application with rather good energy efficiency are then identified.

Evolutionary Games in Interacting Communities

In this paper, we extend the evolutionary games framework by considering a population composed of communities with each having its set of strategies and payoff functions. Assuming that the interactions among the communities occur with different probabilities, we define new evolutionarily stable strategies (ESS) with different levels of stability against mutations. In particular, through the analysis of two-community two-strategy model, we derive the conditions of existence of ESSs under different levels of stability. We also study the evolutionary game dynamics both in its classic form and with delays. The delays may be strategic, i.e., associated with the strategies, spatial, i.e., associated with the communities, or spatial strategic. We apply our model to the Hawk–Dove game played in two communities with an asymmetric level of aggressiveness, and we characterize the regions of ESSs as function of the interaction probabilities and the parameters of the model. We also show through numerical examples how the delays and the game parameters affect the stability of the mixed ESS.

The Coverage Configuration Protocol under AT-Dist Localization☆

Abstract Sensing coverage is one the most fundamental research issues in wireless sensor networks. It reflects how well a sensor network is able to monitor or track a field of interest. So far, several sensing coverage protocols have been proposed. Throughout the diversity of research works in this topic, major interests focused purely on the coverage problem under the restrictive assumption that each deployed node is equipped with a GPS receiver that provides it with its precise location. However, in some applications, GPS service may be unavailable, non-practical and very expensive. Confronted to this constraint, different GPS-less localization algorithms for wireless sensor networks have been introduced. Such algorithms enable sensor nodes to estimate their position with some degree of precision. In this paper, we tackle the problem of maintaining coverage from the perspective of a GPS-less localization. We present the design and analysis of a novel integrated framework guaranteeing both sensing coverage and GPS-less localization. In sharp contrast to several existing approaches that address the two problems in isolation, we integrate the well- known coverage configuration protocol CCP with the GPS-less localization algorithm AT-Dist. Extensive simulations results show the efficiency of the proposed unified framework in providing guaranteed coverage and localization while considerably reducing the energy consumption. We also discuss the potential security threats in the framework and propose the use of a secure solution to deal with them.

A game theoretic model for network virus protection

Security is crucial for information systems. In a company, security management is traditionally controlled via a centralized single-point. However, when we deal with multiple computer systems interconnected in a wide area networks (WAN), the use of a central authority for security management is completely meaningless. In this paper, we propose a distributed decision-making designed to thwart viruses in a WAN. A key aspect is whether owners of devices are willing to update their anti-virus in order to protect their computers or not to pay for an anti-virus update and take the risk to be contaminated. Given the fact that computers are interconnected via networks and the Internet, the risk of being infected does not only depend on each computers strategy, but also on the strategies chosen by other computers in the network. This makes the virus protection problem much more challenging. To do so, we model the interaction between nodes as a non-cooperative game in which each node decides individually whether to update the anti-virus or not. The virus spread is assumed to follow a biologically inspired epidemic model in which the dynamic of sources that disseminate the virus evolves as function of the popularity of virus using the influence linear threshold model. We first provide a full characterization of the equilibria of the game and then we investigate the impact of the update cost. In particular, we study the performance of the strategies at the equilibrium in terms of the update cost and the network size on both the security management system and the anti-virus producers. These results give some helpful insights on how secure is decentralizing antivirus update decisions.

An integrated framework for localization and coverage maintenance in wireless sensor networks

Sensing coverage in wireless sensor networks is one of the most fundamental issues, which have been extensively addressed in the literature. It is viewed as one of the critical performance measures in large-scale sensor networks. In this context, researchers have designed several coverage protocols. Throughout the variety of research works in this topic, most interests focused purely on the coverage problem under the restrictive assumption that each deployed node is equipped with a GPS receiver that provides a sensor node with its accurate location. However, in some wireless sensor network applications GPS service may be inaccessible, unpractical and very expensive. Faced to this challenge, several GPS-less localization algorithms for wireless sensor networks have been proposed. Such localization algorithms enable sensor nodes to locate themselves with some degree of accuracy. In this paper, we address the issue of maintaining coverage from the perspective of a GPS-less localization. We particularly integrate two well-known coverage and GPS-less localization solutions, namely CCP and AT-Dist. This integration yields key insights for handling coverage and GPS-less localization in a unified framework in contrast to several existing approaches that address the two issues in isolation. To the best of our knowledge, this will be the first work that integrates those two solutions. Extensive simulations show the effectiveness of this integrated framework to provide guaranteed coverage and localization.

CrossWalk: A novel cross-layer random walk data dissemination in wireless sensor networks

This paper introduces CrossWalk, a novel integrated cross-layer medium access control/routing protocol based on a receiver-oriented contention resolution mechanism for data dissemination in wireless sensor networks. Traditional approaches for data dissemination such as flooding or simple random walks suffer respectively from a large message forwarding overhead and an excessively long cover time. In this scope, CrossWalk, based on biased random walks, aims to achieve a convenient cover time at the cost of a reasonable overhead. In particular, we demonstrate by an analytical study that the proposed biasing strategy based on a decreasing truncated geometric distribution over a fixed contention window favors a data packet to progress-in a unicast fashion-towards nodes in less explored vicinity by making them more likely to win the contention for the medium access. We therefore show by extensive simulations that CrossWalk outperforms common random walks in terms of partial coverage and efficient network resources consumption by making less redundant message transmissions.

Analytical revisit on the use of biased random walks for data forwarding in wireless sensor networks

In recent years, the use of random walks (RW) for data forwarding in wireless sensor networks (WSN) has gained a lot of popularity. However, a negative effect is often caused by the fact that a completely uniform random choice of the next hop during the walk translates into a reduced progress towards the sink node, thereby yielding a long latency. Several strategies are proposed to attenuate this problem. Most of them are characterized by their dependence on state information stored in sensor nodes in order to bias the direction of the walk towards the target. Such information require additional capabilities and it is costly in terms of complexity and energy, which is inherently problematical in WSN. This leads to a tradeoff between mutually contradictory goals and raises the question as to what extent biasing RW can affect the performance of the data forwarding scheme. This question is our primary motivation in investigating the problem of biasing RW based data forwarding from a pure analytical perspective.

Analytical Framework for Contact Time Evaluation in Delay-Tolerant Networks

In the last few years, there has been an increasing concern about stochastic properties of contact-based metrics under general mobility models in delay-tolerant networks. Such a concern will provide a first step toward detailed performance analysis of various routing/forwarding algorithms and shed light on better design of network protocols under realistic mobility patterns. However, throughout the variety of research works in this topic, most interests rather focused on the inter-contact time while other contact-based metrics such as the contact time received too little interest. In this paper, we provide an analytical framework to estimate the contact time in delay-tolerant networks based on some recent key results derived from biology and statistical physics while studying spontaneous displacement of insects such as ants. In particular, we analytically derive a closed-form expression for the average value of the contact time under the random waypoint mobility model and then give an approximation for its distribution function.