Maher Ben Jemaa

Distributed Hash table-based routing and data management in wireless sensor networks: a survey

Recent advances in Wireless Sensor Networks (WSN) have led to a great breakthrough in sensors design and features. These technological novelties have brought additional challenges to WSN. Sensornets are seeking for new approaches for efficient data routing and management. The last few years have witnessed the emergence of several approaches that build Distributed Hash Tables (DHTs) over WSN. DHTs are initially conceived for efficient data lookup in large-scale wired networks. The main objective of this combination is to manage location-independent data and nodes identification. DHT mapping over WSN brings however new challenges. This paper presents an analytical survey on applying DHT techniques in WSNs. It describes existing DHT-based routing and data management protocols and includes a detailed classification of them.

Vehicular cloud networks: Challenges, architectures, and future directions

Vehicular Cloud Computing is a promising solution to exploit the underutilized vehicular resources and to meet the requirements of VANET applications and services. Although modern vehicles have important capacities of computation and storage, there is an increasing need for resources, in particular, for safety applications which require the cooperation between vehicles. The vehicular cloud offers to users the opportunity to rent resources on-demand or to share them freely to run their applications or to carry out some tasks. Even though this paradigm is feasible, its implementation still faces problems. Many researchers have focused on the architectural design in order to overcome different challenges and consequently meet user requirements to provide him/her with reliable services. In this work, we survey the vehicular cloud paradigm. We focus on its features and architectures. We first present a brief overview of the motivation of vehicular cloud. Then, we explore challenges related to its design. Furthermore, we highlight the features of existing vehicular cloud architectures: we provide a taxonomy of vehicular cloud followed by our classification criteria. Finally, we discuss issues that can be considered as open research directions.

An Efficient Mobility Management Approach for IEEE 802.15.4/ZigBee Nodes

Mobility management in IEEE 802.15.4/ZigBee networks is not efficiently handled. This paper presents an enhanced approach for mobility management of end devices in IEEE 802.15.4/ZigBee cluster tree network related to a backbone network. This approach anticipates link disruption and does not require scanning neighbor cells. It is based on the link quality indicator (LQI) and uses a speculative algorithm. Using different mobility models and network parameters, it is demonstrated that the energy consumption as well as the latency of mobile devices can be significantly reduced.

An ID-based user authentication scheme for Wireless Sensor Networks using ECC

The explosive growth in the use of mobile and wireless devices demands a new generation of remote user authentication schemes that has to accommodate limitations on power and bandwidth, at the same time, to provide an adequate level of security for transferred data in wireless networks. In this paper, we present a new method of access control adapted to constrained Wireless Sensor Networks (WSNs), thats provide access to legitimate users and deny access to illegitimate ones. Our scheme is based on the ID-based techniques and the Elliptic Curve Cryptography (ECC). The proposed protocol provides mutual authentication and key establishment between the user and a gateway node in the WSN.

Semantic matching of WS-SecurityPolicy assertions

The lack of semantics in WS-SecurityPolicy (WS-SP) hampers the effectiveness of matching the compatibility between WS-SP assertions. To resolve this problem, we present in this paper a semantic approach for specifying and matching the security assertions. The approach consists in the transformation of WS-SP into an OWL-DL ontology and the definition of a set of semantic relations that can exist between the provider and requestor security concepts. We show how these relations lead to more correct and flexible matching of security assertions.

Dynamic and On-Line Design Space Exploration for Reconfigurable Architectures

The implementation of complex embedded applications requires a mix of processor cores and HW accelerators on a single chip. When designing such complex and heterogeneous System on Chip (SoCs), the HW/SW partitioning needs to be made prior to refining the system description. Traditional system partitioning is generally done at the early stage of system architecture, by defining the tasks to be implemented on the embedded processor(s), and the tasks to be implemented on the hardware. We describe here a new approach of On-line Partitioning Algorithm (OPA) which consists of adapting dynamically the architecture to the processing requirements. A scheduling heuristic is associated to this partitioning approach. We consider soft real time data flow graph oriented applications for which the execution time is dependent on the content of input data. The target architecture is composed of a generic processor connected to a dynamically reconfigurable hardware accelerator. The dynamic reconfiguration allows the self adaptation of the architecture which avoids redesigning a new architecture according to variation of characteristics of applications algorithms. We compare our method with an Off-line static HW/SW partitioning approach. We present results of the OPA on an image processing application. Our experiments included simulation results with SystemC for on-line scheduling and partitioning approaches. An ILP solver is used to compare the experiment results with an off-line static HW/SW partitioning approach.

Energy-aware Virtual Ring Routing in Wireless Sensor Networks

Virtual Ring Routing (VRR) is an ad-hoc routing protocol that avoids flooding the network. It uses location independent identifiers for packet routing. However, VRR does not take into consideration the amount of energy in nodes, leading to the failure of several nodes in the network. To resolve this problem, we have adopted a hierarchical Distributed Hash Table in the VRR architecture. In the resulting architecture, the energy powerful sensors are responsible for most message traffic. Weak sensors are then utilized less frequently than powerful sensors. The experimental results show that Coral-based VRR consumes less energy than VRR and extends the network lifetime.

Toward Antifragile Cloud Computing Infrastructures

Abstract Cloud computing systems are rapidly growing in scale and complexity. They are also changing dynamically as a result of dynamic addition and removal of system components, different execution environments, common updates and upgrades, runtime repairs, mobility of devices and more. Such large-scale, complex and dynamic cloud environments are prone to failures and per- formance anomalies. Thus, dependability and resilience in cloud computing are of paramount importance to guarantee availability and reliability of services and application execution, even in the presence of large number of faulty components. Antifragility is the key to such techniques. It proposes that some systems could be strengthened by changes and faults instead of be weakened by them. In contrast to classical resilience methods, antifragile techniques aim to build systems that handle unpredictable and irregular events, while growing and getting stronger. Most of the classical resilience techniques are not sufficient to build highly available cloud infrastructures. In fact, they just resist shocks and stay the same. They should be complemented by some other aspects like learning from failure to built more elastic and stronger cloud infrastructures. This may represent the idea of building antfragile cloud systems. In this paper, we discuss the existing resilience techniques and propose a solution to design antifragile systems in cloud computing environments.

Semantic matching of web services security policies

The lack of semantics in WS-SecurityPolicy (WS-SP) hampers the effectiveness of matching security policies. To resolve this problem, we present a semantic approach for specifying and matching web service security policies. The approach consists in the transformation of WS-SP into an OWL-DL ontology and the definition of a set of rules which automatically generate semantic relations that can exist between the provider and requestor security requirements. We show how these relations lead to more correct and accurate matching of security policies. At the end of this paper, we present the implementation of our approach and its validation through a real-world use case.

Combination of document structure and links for multimedia object retrieval

In this paper, we are interested in XML multimedia retrieval, the aim of which is to find relevant multimedia objects such as images, audio and video through their context as document structure. In context-based multimedia retrieval, the most common technique is based on the text surrounding the image. However, such textual information can be irrelevant to the image content. Therefore many works are oriented to the use of alternative techniques to extend the image description, such as the use of ontologies, relevance feedback, and user profiles. We studied in our work the use of links between XML elements to improve image retrieval. More precisely, we propose dividing the document into regions through the document structure and image position. Then we weight links between these regions according to their hierarchical positions, in order to distinguish between links that are useful and those that are not useful. We then apply an updated version of the HITS algorithm at the region level, and compute a final image score by combining link scores with initial image scores. Experiments were done on the INEX 2006 and 2007 multimedia tracks, and showed the potential of our method.