Abdelfettah Belghith

Wireless Body Area Networks: Applications and Technologies☆

Abstract The increasing use of wireless networks and the constant miniaturization of electrical invasive/non-invasive devices have empow- ered the development of Wireless Body Area Networks (WBANs). A WBAN provides a continuous health monitoring of a patient without any constraint on his/her normal daily life activities. Many technologies have proved their efficiency in supporting WBANs applications, such as remote monitoring, biofeedback and assisted living by responding to their specific quality of service (QoS) requirements. Due to numerous available technologies, selecting the appropriate technology for a medical application is being a challenging task. In this paper, the different medical applications are presented. The most common technologies used in WBANs are highlighted. Finally, a matching between each application and the corresponding suitable technology is studied.

A distributed advanced analytical trust model for VANETs

In this paper we propose a trust model based on a Markov chain in order to formalize the trust metric variation and its stability in the context of Vehicular Ad hoc Networks (VANETs). The proposed model takes into account not only the dynamic trust metric variation according to the vehicles behaviors, but also the constraints related to the monitoring process. In our model each vehicle can act as monitor and update the trust metric of its neighbors according to their behavior in the network. In addition, our model can be customized through different parameters like the trust interval and the number of transitions needed to reach the highest trust level. This flexibility enables to adapt the model according to the application context. The performance evaluation of the proposed model is presented with different parameters and two types of disruptive vehicles are taken into account: malicious and selfish. The obtained results show the resistance, the robustness and the incentive of the proposed model against the fluctuations of the vehicles behaviors.

Stability routing with constrained path length for improved routability in dynamic MANETs

Quality of service (QoS) routing is known to be an NP-hard problem in case of two or more additive constraints, and several exact algorithms and heuristics have been proposed to address this issue. In this paper, we consider a particular two-constrained quality of service routing problem maximizing path stability with a limited path length in the quest of improving routability in dynamic multi-hop mobile wireless ad hoc networks. First, we propose a novel exact algorithm to solve the optimal weight-constrained path problem. We instantiate our algorithm to solve the most stable path not exceeding a certain number of hops, in polynomial time. This algorithm is then applied to the practical case of proactive routing in dynamic multi-hop wireless ad hoc networks. In these networks, an adequate compromise between route stability and its length in hops is essential for appropriately mitigating the impact of the network dynamics on the validity of established routes. Secondly, we set up a common framework for the comparison between three families of proactive routing: the shortest path-based routing, the most stable path-based routing and our proposed most stable constrained path routing. We show then through extensive simulations that routing based on our proposed algorithm selects appropriate stable paths yielding a very high routability with an average path length just above that of the shortest paths.

A new generic model for signal propagation in Wi-Fi and WiMAX environments

The ability to accurately predict radio propagation behavior for wireless communication systems, such as cellular mobile radio, is becoming crucial to system design. Since site measurements are costly, propagation models have been developed as suitable, low-cost, and convenient alternative. In this paper, we will propose a new generic signal propagation model for Wi-Fi and WiMAX environments. To develop this model we used existing models which are classified as: Free space models and land propagation models. This includes different types of loss: path loss, slow fading (shadowing) and fast fading. Our aim is to have a flexible model to be applicable in indoor and outdoor environments. Experiments carried out for indoor Wi-Fi and outdoor WiMAX cases have shown excellent results for the proposed model.

LEATCH: Low Energy Adaptive Tier Clustering Hierarchy

Abstract In Wireless Sensor Networks, low latency, energy efficiency, and coverage problems are considered as three key issues in designing routing protocols. In this paper we present a new protocol called Low Energy Adaptive Tier Clustering Hierarchy (LEATCH), which offers a good compromise between delay and energy consumption and resolves some coverage problems. For our purpose, a two level hierarchical approach has been proposed to organize a sensor network into a set of clusters, every cluster divided into small clusters that are called Mini Clusters. As the way the clusters are organized, for each mini cluster we define a Mini Cluster- Head (MCH). Every MCH communicates with the cluster-head directly, it aggregates its mini-cluster information. In addition, we have made some changes in the procedure of cluster head and mini cluster head election. LEATCH promises better performances than the conventional LEACH protocol which is one of the most known hierarchical routing protocols using the probabilistic model to manage the energy consumption in WSNs. Simulation results show that LEATCH performs better than LEACH in term of energy, delay, coverage and scalability.

Secure Clustering Scheme Based Keys Management in VANETs

We propose an efficient dynamic architecture of the Public Key infrastructure (PKI) for vehicular ad hoc networks (VANETs) based on a trust model and a novel distributed clustering algorithm. Furthermore, we introduce the notion of a VANET Dynamic Demilitarized Zone (VDDZ), composed of the set of confident vehicles located within the immediate neighborhood of each clusterhead (CH) to assume the Registration Authorities (RA). The VDDZ aims to secure the elected CAs by shielding them from unknown or malicious vehicles. A host of simulations using urban and highway scenarios are conducted to investigate the effects of the transmission range, the speed of vehicles and the number of confident vehicles in the network on the security level, the stability and the efficiency of our proposed architecture. In particular, the results show a strong dependency of the security and the stability on the assumed percentage of trust nodes and the mobility models.

Technology integration framework for fast and low cost handovers: case study: WiFi-WiMAX network

The Next Generation Wireless Networks (NGWNs) are seemed to be heterogeneous networks based on the integration of several wireless technologies. These networks are required to achieve performances equivalent to classic wireless networks by ensuring the continuity of communications and the homogeneity of network management during horizontal and vertical handovers. This task is even more important when management services, like security and quality of service (QoS), are deployed at access technology level. In this paper, we propose a framework for heterogeneous wireless technology integration based on network architecture skeleton and a handover management mechanism. This framework optimizes the layer-2 handover procedure to achieve performances required by sensitive applications while ensuring the minimization of signaling overhead required for operated networks. As an application example, we make use of this framework to propose a heterogeneous network based on WiFi and WiMAX technologies. We present an application example of the framework using the specification of a WiFi-WiMAX network. We propose several performance evaluations based on simulation tests based on this application. The latter confirm the efficiency of handover delay optimization and the minimization of management signaling costs.

New Strategies and Extensions in Weighted Clustering Algorithms for Mobile Ad Hoc Networks

Abstract We study the problem of constructing a novel framework for dynamically organizing mobile nodes in wireless ad-hoc networks into clusters where it is necessary to provide robustness in the face of topological changes caused by node motion, node failure and node insertion/removal. The main contribution of our work is a new strategy for clustering a wireless AD HOC network and improvements in WCA (Weighted Clustering Algorithm) [3] , a well-known algorithm. We first derive mathematically a new cluster size bound to replace δ in WCA and a simple node stability model. Thereafter, we prove their efficiencies. Our contribution also extends previous work to replace the degree- difference used initially in WCA to provide load-balance in wireless AD HOC with a new more efficient and consistent model which helps to decrease the number of clusters. We show that our algorithm outperforms WCA in terms of cluster formation and stability. The non-periodic procedure for clusterhead election is invoked on-demand, and is aimed to reduce the computation and communication costs. We strive to provide a trade-off between the uniformity of the load handled by the clusterheads and the connectivity of the network.

LTE Based Communication System for Urban Guided-Transport: A QoS Performance Study

The control and management of new urban guided-transport systems such as tramways and subways are based on several IT services with heterogeneous data communication requirements. These applications are known as CBTC (Communication Based Train Control systems) and CCTV (Closed Circuit TeleVision). In order to support existing as well as emerging applications over a unique communication infrastructure, it is mandatory to be able to ensure efficient QoS management that meets the requirements of CBTC and CCTV services especially the critical ones. This paper presents an evaluation of QoS provisioning in LTE (Long Term Evolution) based communication system for urban guided-transport. The evaluation is made through simulations with the well known event driven simulator OPNET. We propose a mapping of the typical applications CBTC and CCTV to standardized 3GPP QCIs (QoS Class Identifiers) that serve as a basis for the LTE class-based QoS. After discussion of the obtained results, we provide recommendations to enhance the communication performances experienced by these applications.

Dynamically self adjustable proactive routing protocols for mobile ad hoc networks

Routing in Mobile Ad hoc Networks (MANETs) is central to their proper functioning. Mobility in such networks makes the routing a real challenging task. Routes validity plays a central leveraging mission to enhance network performances. Forwarding through incorrect routes not only results in traffic wandering inside the network without ever being able to be delivered to their ultimate destinations but also over consumes valuable network resources. As mobility of nodes gets higher, the routing period should be set smaller to be able to correctly track frequent changes in the topology. An adequate trade off should then be found between the size of the routing period which controls the amount of traffic overhead and the validity of routes which governs the performances of the network.