Leila Azouz Saidane

Ecole Supérieure de Technologie et d'Informatique, Tunis-Ville, Tūnis, Tunisia

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Publications (52)0.51 Total impact

  • ons mabrouk, Pascale Minet, Hanen Idoudi, Leila Azouz Saidane
    HPCC 2014 : 16th IEEE International Conference on High Performance and Communications, Paris, France; 08/2014
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    ABSTRACT: Cars cruising for parking adds a non negligible amount to traffic congestion and CO2 pollution. Hence, good parking management policies are required to reduce such dis-comfort. In this paper, we address this problem from two sides. First, we consider how local parking authorities called parking coordinators (PC) can optimize the distribution of the slots they manage through a full cooperation between them. Second, we model the problem as a congestion game, where vehicles act as players who will eventually choose the best parking garage for them, while minimizing the whole network cost. We study the effectiveness of both schemes (i.e., PC-aware and game theoretic approaches) in various contexts and compare them with the reference centralized model as well as a greedy approach. Simulation results show that our proposals provide high request satisfaction ratio, close to the optimal baseline approach and outperform the greedy method up to 30%, while ensuring a fair distribution of slots through the network.
    ICC 2014; 06/2014
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    AINA 2014: 28th IEEE International Conference on Advanced Information Networking and Applications, Victoria, Canada; 05/2014
  • Skander Azzaz, Leila Azouz Saidane
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    ABSTRACT: In this paper, we have introduced three proactive maintenance strategies for static wireless sensor networks (WSNs) using a limited number of mobile maintainer robots: the centralised proactive maintenance strategy denoted by CPMS, the fixed distributed proactive maintenance strategy denoted by FDPMS and the adaptive distributed proactive maintenance strategy denoted by ADPMS. The proposed maintenance strategies are based on a simple energy dissipation analytical model to estimate the occurrence times of the expected sensor failures in the network. Once identified, the anticipated failures are replaced by the available robots before they happen. To select the appropriate maintainer robot for each expected failure, CPMS opts for a centralised scheduling method based on the genetic algorithm fundamentals. However, the distributed maintenance strategies (FDPMS and ADPMS) use two different WSN area partitioning methods to share the sensor maintenance tasks among the available robots. Simulation results have shown that CPMS gives the minimal network dysfunction time representing the interruption service time induced by the detected faulted nodes. However, due to its significant signalling cost, we have remarked that CPMS can be deployed only in small scale WSNs. In large-scale ones, ADPMS has demonstrated its efficiency in terms of the network dysfunction time, the robot travelled distance and the introduced signalling cost. In particular cases, when sensor failures are uniformly distributed on the network map, FDPMS has given the best performances. Copyright © 2013 John Wiley & Sons, Ltd.
    Transactions on Emerging Telecommunications Technologies. 12/2013;
  • Nour Brinis, Leila Azouz Saidane
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    ABSTRACT: Energy depletion of sensor nodes is one of the major issues in the wireless sensor networks. Data gathering reveals a convenient solution in order to conserve the sensor nodes energy. It aims at using mobile robots able to visit sensor nodes in order to collect sensed data and carry them to the sink. However, visiting each node may lead to an exponential data latency in the network due to the data collector tour length. So, introducing local relay hop transmissions may be mandatory in order to deliver data to the sink in an acceptable delay. Most of the previous studies have mainly focused on finding an appropriate trade-off between the tour length and the number of local relay hops. However, they neglect the energy depletion of the coordinator nodes, responsible of relaying sensed data into the mobile data collector. Indeed, preserving a uniform energy level constitutes one of the challenging issues in wireless sensor networks. Hence, we propose, in this paper, an enhancement of a bounded relay hop data gathering strategy by ensuring a balanced energy conservation between the active sensor nodes. This study proves that this enhancement contributes significantly to extend the network lifetime.
    Proceedings of the 10th ACM symposium on Performance evaluation of wireless ad hoc, sensor, & ubiquitous networks; 11/2013
  • Hanen Idoudi, ons mabrouk, leila azouz saidane
    African Journal of Information and Communication Technology. 11/2013; 7(2).
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    ABSTRACT: This paper provides a description of a wireless mesh network testbed setup and a measurement-based performance evaluation of the Optimized Link State Routing (OLSR) protocol [7] under three different routing metrics. The considered metrics include hop-count, ETX and ETT. The network performances are evaluated in an indoor testbed formed by heterogeneous MIMO devices. A part of our tests was about the impact of 802.11n features on the network performances showing the importance of lower layers consideration. Our measurements point out the shortcoming of each metric and eventual optimizations towards a more efficient routing. Experimental results show that OLSR-ETT outperforms OLSR-ETX and OLSR-hopcount significantly in terms of packet loss, end-to-end delay, and efficiency.
    IEEE IWCMC 2013, Italy; 07/2013
  • Hanen Idoudi, Fatma Somaa, Leila Azouz Saidane
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    ABSTRACT: Using wireless body sensors in medical field is becoming an efficient, low cost and non invasive way for continuously monitoring patients' vital signs. New MAC protocols have to be designed to handle the intrinsic constraints of Wireless Body Area Networks (WBANs) especially insuring low latency for alarms management and high reliability. In this paper, we propose a new access method in WBANs for alarms management: E-Health Access Channel Mechanism (E-HACM). E-HACM is intended to be used in e-health applications designed to monitor patients' vital signs by fixing on them body sensors for periodic measurements and to detect critical cases that require real-time delivery and no data loss. Simulation results show that our proposed mechanism outperforms IEEE 802.15.4 in terms of delay, energy consumption and packet loss ratio.
    10th ACS/IEEE International Conference on Computer Systems and Applications (AICCSA); 05/2013
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    ABSTRACT: This paper investigates the design of effective routing metrics in the purpose of network resources optimization and the satisfaction of users QoS requirements. Using several real experiments, we point out the shortcoming of the Expected Transmission Count (ETX) metric for eventual optimizations towards a more efficient routing. Experiments were carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol and have shown that ETX presents several shortcoming resulting in inaccurate estimation of the link quality and then of the routing decision. This paper presents improvements of the ETX metric based on link availibility for accurately finding high-throughput paths in multihop wireless mesh networks.
    10th ACS/IEEE International Conference on Computer Systems and Applications (AICCSA); 05/2013
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    ABSTRACT: Current routing mechanisms proposed for adhocnetworks are still feasibly applied in Wireless Mesh Networks given their similarities. Many researchers have conducted numerous simulations for comparing the performances of these routing protocols under various conditions and constraints. Most made comparisons are not aware of PHY/MAC layers and their impact on routing performances. In this paper we study through simulations the impact of PHY/MAC protocols on higher layers. The considered protocols include three propagation models, i.e., Free Space, TwoRayGround and Shadowing, three different PHY/MAC protocols specified IEEE 802.11 standards namely, 802.11b, 802.11s and 802.11n, and finally three routing protocols, i.e., AODV, OLSR and HWMP. In a comparative way, we investigate the effectiveness of these protocols when they coexist on a wireless mesh network environment. Our results show that the routing strategy can significantly impact the network performance only if it is strongly linked to the characteristics of the lower layers.
    AINA-International Symposium on Frontiers of Information Systems and Network Applications (FINA 2013); 03/2013
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    ABSTRACT: In this paper, we propose a new approach to ensure fault tolerance in wireless sensor networks (WSNs) while guaranteeing both coverage and connectivity in the network. Hence after reviewing the fault tolerance related works in wireless sensor networks and enumerating the requirements that must be satisfied by our fault tolerance solution, we present the different mechanisms we propose to maintain both coverage and connectivity in the network in the case of node failure. Our approach is a proactive one in the sense that it aims to replace the “up to fail” node before its defection. In the case of impossible replacement of the “up to fail” node, a fast rerouting mechanism is proposed to forward the traffic initially routed via the “up to fail” node. Performance evaluation of our fault tolerance approach shows that the number of nodes potentially eligible for the “up to fail” node replacement depends on a threshold about the node redundancy as well as the network density metric. Moreover, we show that, compared to a classical routing algorithm, our fast rerouting mechanism reduces the packet loss rate in the network.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2013 9th International; 01/2013
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    ABSTRACT: In the last few years, femtocells have gained a great deal of interest as an emerging wireless and mobile access technology to improve indoor coverage and network capacity. In such an environment, mobility management is one of the major concerns that may limit the wide deployment and adoption of such networks. In this paper, we investigate the handover procedure for the two-tier macro/femto LTE networks. An optimized handover algorithm with an efficient call admission control has been proposed and described. Our proposed scheme is mainly designed to reduce the number of unnecessary handovers and to maintain the communication quality during the handover. The choice of the femtocell target takes into account the direction of the mobile user, its velocity and the quality of the signal. Performance evaluation results show that our algorithm minimizes both the number of hand-in and the handover drop rate. Besides, the signal quality in terms of SINR after the hand-in is maintained higher than a fixed threshold, which maximizes the sojourn time of the mobile user within the selected femtocell.
    Wireless and Mobile Computing, Networking and Communications (WiMob), 2013 IEEE 9th International Conference on; 01/2013
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    ABSTRACT: This paper presents two novel metrics, Link Occupancy aware routing Metric (LOM) and Residual Link Capacity based routing metric with Interference Consideration (RLCIC), for accurately finding high-throughput paths in multihop wireless mesh networks. The first metric is load-sensitive and aims to balance the traffic load according to the availability of a link to support additional flows. The second metric reproduces better the capacity of a link since it is based on its residual bandwidth. It captures accurately the available path bandwidth information when considering both the intra-flow and the interflow interferences. Using several real experiments carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol, we have shown that our first proposal can accurately determine better paths in terms of throughput and delay, thereby significantly outperforming the other existing metrics. The consistency of the second metric RLCIC is proved formally based on notions of graph theory.
    Global Information Infrastructure Symposium, 2013; 01/2013
  • Skander Azzaz, Leila Azouz Saidane
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    ABSTRACT: Generally, the Quality of Service (QoS) in a wireless sensor network (WSN) is measured by the sensing area coverage degree and the connectivity between the deployed sensors. To conserve and protect these QoS parameters, we have used a limited number of mobile maintainer robots to handle the eventual network failed sensors. In this paper, we have introduced two Centralized Preventive Maintenance Strategies (CPMS) dedicated for the WSNs. Indeed, with an analytical energy model representing the energy consumption of each network's node, a central manager robot estimates the expected sensors failures to be repaired by the available robots before the total depletion of their energies. To schedule the available maintainer robots, we have introduced two Centralized Preventive Maintenance Strategies (CPMS) for WSNs with two scheduling approaches used to obtain the convenient maintainer robot scheduling for a fixed number of anticipated failures (fixed window): (i) CPMS with the Nearest available robot heuristic Backtracking robot scheduling algorithm (CPMS-NB) and (ii) CPMS with a Genetic robot scheduling Algorithm (CPMS-GA). Simulation results show that the CPMS-GA scheduling algorithm is more complex than that of CMSA-NB, but it gives a better network dysfunction time with a minimal robot traveling distance.
    Proceedings of the 1st ACM workshop on High performance mobile opportunistic systems; 10/2012
  • Skander Azzaz, Leila Azouz Saidane
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    ABSTRACT: In this paper, we have proposed two distributed preventive maintenance strategies dedicated for large-scale wireless sensor networks (WSNs) using a reduced number of mobile robots : (i) Fixed Distributed Preventive Maintenance Strategy denoted by F-DPMS, (ii) Adaptive Distributed Preventive Maintenance Strategy denoted by A-DPMS. F-DPMS and A-DPMS are based on a simple analytical model to estimate the expected failures. To share the sensors repair load among the available robots, F-DPMS subdivides the WSN sensing area in equal surface subareas. Each maintainer robot is assigned to a single one area to deal with its anticipated failures. In contrary, A-DPMS uses an adaptive area partitioning technique depending on the distribution of failures over the network map, in order to balance the repair load sharing. Simulation has shown that both F-DPMS and A-DPMS provide a null network dysfunction time with a sufficient number of robots. Obtained results show also that A-DPMS requests a minimal number of robots lower than F-DPMS. But, it produces a heavier signaling cost. To remedy this problem, we have proposed a new version of A-DPMS denoted by A-DPMS*. The novel maintenance strategy reduces not only the introduced signaling messages, but also the traveled distance achieved by the maintainer robots to replace the expected failures.
    Proceedings of the 9th ACM symposium on Performance evaluation of wireless ad hoc, sensor, and ubiquitous networks; 10/2012
  • Ines El Korbi, Chayma Zidi, Sherali Zeadally, Leila Azouz Saidane
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    ABSTRACT: We propose a new technique to relocate a set of redundant sensor nodes from their initial deployment area called ROI (region of interest) to a new location outside the ROI called COI (center of interest) where a new event happened (e.g., to measure the soil contamination level in the case of a chemical spill disaster). Relocating mobile sensor nodes from their initial deployment area ROI requires covering that area at a given center of interest while maintaining connectivity with the initial region of interest. Our proposed technique to relocate redundant mobile sensors nodes towards a new target position is a four-phase solution that includes the clustering phase and the cell head election, the evaluation of the number of nodes to be relocated, the propagation of the COI position, and finally the election of the redundant nodes and their relocation. A performance evaluation of our novel relocation approach shows that the consumed energy and the relocation time increase as the distance separating the initial ROI from the COI increases regardless of the size or the density of the initial deployment area.
    Proceedings of the 15th ACM international conference on Modeling, analysis and simulation of wireless and mobile systems; 10/2012
  • I. El Korbi, L. Azouz Saidane
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    ABSTRACT: To satisfy the Quality of Service (QoS) requirements of delay-sensitive flows, we propose in this paper to support the Earliest Deadline First (EDF) policy over wireless ad hoc networks. Hence, we enhance the IEEE 802.11 protocol to support the real-time EDF scheduling policy. Therefore, we develop a Markov-chain-based analysis modelling the backoff process of the EDF policy. Then, we propose to evaluate the performance of EDF in terms of saturation throughput and service time delay bounds. Service time delay bounds are obtained by inverting service time Z-transforms. Analytical results are validated and extended by simulation using the NS-2 network simulator. Finally, we evaluate the performance of the EDF policy in a multi-hop environment in the presence of ad hoc routing protocols.
    International Journal of Ad Hoc and Ubiquitous Computing 08/2012; 10(3):175-195. · 0.51 Impact Factor
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    Hanen Idoudi, Chiraz Houaidia, Leila Azouz Saidane, Pascale Minet
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    ABSTRACT: Connectivity and coverage are two crucial problems for wireless sensor networks. Several studies have focused on proposing solutions for improving and adjusting the initial deployment of a wireless sensor network to meet these two criteria. In our work, we propose a new hierarchical architecture for sensor networks that facilitates the gathering of redundancy information of the topology. Several mobile robots must then relocate, in an optimized way, redundant sensors to achieve optimal connectivity and coverage of the network. Mobile robots have to cooperate and coordinate their movement. A performance evaluation is conducted to study the trade-off between the number of required robots and its impact on the rate of network connectivity and coverage.
    Journal of Networking Technology. 03/2012; 3(1):1-12.
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    Chiraz Houaidia, Hanen Idoudi, Leila Azouz Saidane
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    ABSTRACT: Wireless sensor networks are often deployed in hardly accessible or hazardous fields. Their main goal is to monitor the target field and transmit surveillance data to a sink. Therefore, connectivity of the sensor network and the coverage ratio of the monitored area are the most relevant concerns to reach these goals. In this paper, we propose to use several mobile robots to assist sensor networks redeployment in order to enhance the network connectivity and the coverage ratio of the monitored area. We model the sensor network as an islets-based topology and we propose to use robots to detect and heal connectivity and coverage holes availing the sensors redundancy. Preliminary simulations showed that our new scheme can significantly enhance the connectivity ratio of the initial network and improve the coverage ratio by using few numbers of robots.
    01/2011;
  • H. Idoudi, N. Hmili, L.A. Saidane
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    ABSTRACT: In this paper, we introduce a new asynchronous power saving architecture that provides an adaptive duty cycle, depending on the network load with no overhead. Our proposition is based on the combination of two novel protocols: a load balancing MAC protocol and a very simple, yet efficient, forwarding function. They achieve power saving by balancing nodes activity and eliminating any routing overhead while insuring fault tolerant communications. Preliminary simulation results demonstrate the effectiveness of our proposed approach in terms of mean residual energy and energy distribution compared to BMAC and Greedy geographic routing.
    Mediterranean Microwave Symposium (MMS), 2011 11th; 01/2011