Platooning refers to a group of synchronized vehicles travelling near each other. It is regarded as an effective solution for optimizing traffic flows, reducing fuel consumption and improving road safety. A platoon is a dynamic structure that allows vehicles to join or leave during the journey. However, a vehicle may attempt to join the platoon to cause damage or disrupt its stability. A platoon may also be exposed to malicious attacks from external sources. Thus, a phase to authenticate new members and generate a secret group key is required to authorize only legitimate vehicles and to secure communications between platoon members. Most authentication mechanisms rely on a third party, which makes authentication impossible in the case of intermittent connectivity, particularly when travelling on highways. This paper presents a new scheme for verifying the legitimacy of new members and generating a group key, even in an environment with intermittent connectivity. The mechanism is based on Diffie-Hellman key exchange and secret key sharing; it aims to reduce the complexity, and the control overhead associated with the key management process for joining and leaving operations. The security analysis shows that our scheme can ensure authentication, privacy protection and confidentiality.

Summary Due to the increasing number of vehicles in circulation in different urban cities, several automatic traffic monitoring systems have been developed. In particular, traffic monitoring systems using roadside cameras are becoming extensively deployed, as they offer imperative technological advantages compared with other traffic monitoring systems. Vehicle detection and traffic congestion classification are two main steps for video‐based traffic congestion detection systems; the associated methods have a deep impact on the performance of the whole system. In this paper, we investigate four selected vehicle detection methods namely Gaussian Mixture Model (GMM), GMM‐Kalman filter, Optical Flow, and ACF object detector in two contexts: urban and highway. Three traffic congestion classification methods are also studied. The comparative study of the different methods allows us to choose the most appropriate ones to be integrated in the framework proposed to solve the traffic issues in the bridge of Bizerte.

Summary As sensor nodes are power constrained, saving energy and prolonging network lifetime have been given the greatest priority in the design of routing protocols in wireless sensor networks (WSNs). In this regard, duty‐cycling is broadly utilized as an underlying MAC (Medium Access Control)‐based protocol for routing solutions. In this regard, a cross‐layer approach, integrating MAC and routing protocols, is required to achieve a trade‐off between energy efficiency and communication reliability, through adapting nodes duty‐cycle to routing decisions. Besides, with the proliferation of WSNs applications in various domains, achieving energy efficiency should not be performed while ignoring the diverse quality of service (QoS) demands of the considered applications to ensure their well functioning. In this context, we propose a context‐aware routing framework under duty‐cycled networks, a generic framework that allows to support heterogeneous applications and traffic patterns. An evaluation of the framework is also proposed in this paper. Results prove the effectiveness of context‐awareness and the cross‐layer interaction between the different modules of the framework to guarantee desired QoS while reducing energy consumption.

Summary The specific characteristics of vehicular ad hoc networks, such as high speed of nodes and frequent topology changes, impose challenges for the routing process. In addition, the advent of the Internet of Vehicles (IoV) concept along with the autonomous and connected cars contribute to the proliferation of new innovative applications with different quality of service requirements, rising new challenging issues for data transfer. In this article, we review the different taxonomies of vehicular routing protocols, while giving an insight into the design of geographical protocols. Then, we outline several optimization techniques and paradigms used to enhance the routing process. Moreover, in order to promote the deployment of robust IoV routing protocols at large scale, we provide some directions for future research work.

Internet of Vehicles (IoV) constitutes an important part of the Smart Cities concept, relying on different technologies and including heterogeneous cars types, which raises challenges to ensure and preserve road safety. Throughout this paper, we tackled the data collection and transmission problems related to the safety in the terrestrial domain by identifying the car-types and exposing the different communication data levels and means used in the quest of safety realization.

Wireless Body Area Networks are nowadays attracting both academic and industrial worlds. Combining collected data related to patient context with original health measurement can enhance the general health state monitoring and help to better understand the patient disease evolution. Daily activity is one of the important features that may influence the patient health state. Thus, recognizing the user activity can be a useful way for improving quality of health services. Relying on supervised learning, we study the feasibility of extracting and classifying the human activities from channel gain measures, which is an important feature that characterizes the WBAN channel links.

As the energy efficiency remains a key issue in wireless sensor networks, duty-cycled mechanisms acquired much interest due to their ability to reduce energy consumption by allowing sensor nodes to switch to the sleeping state whenever possible. The challenging task is to authorize a sensor node to adopt a duty-cycle mode without inflicting any negative impact on the performance of the network. A context-aware paradigm allows sensors to adapt their functional behavior according to the context in order to enhance network performances. In this context, the authors propose an enhanced version the Efficient Context-Aware Multi-hop Broadcasting (E-ECAB) protocol, which combines the advantages of context awareness by considering a multi criteria and duty-cycle technique in order to optimize resources usage and satisfy the application requirements. Simulation results show that E-ECAB achieves a significant improvement in term of throughput and end-to-end delay without sacrificing energy efficiency.

The wide proliferation of wireless sensor networks in various domains has lead to the emergence of numerous applications with different requirements to satisfy for the well functioning. It is imperative to develop different approaches and communication protocols to meet these diverse and specific requirements while considering the most critical constraint, network lifetime. Adopting duty cycling is an efficient way to conserve energy, by allowing nodes to turn off their radio whenever possible. With these intermittent sleeping periods, it is hard to meet short delay delivery for real time traffic in duty cycled networks, since involved nodes in forwarding are not always awake. For delay intolerant applications, providing an always-on path without scarifying energy can be an effective solution. In this context, we propose a node-disjoint multipath routing algorithm, operating under duty cycled environment, to construct n complementary paths from the source towards the sink. To support urgent data transfer from sources of critical traffic, our protocol aims to offer always at least one available path while others are down. Simulation results show good performances in term of energy consumption and the number of exchanged packets control with a relative small increase in paths establishment time.

Context-awareness has gained an increasing popularity in ubiquitous computing environments as it allows automatic adaptation of protocols behavior according to context changes. Nowadays, wireless sensor networks (WSNs), deployed as a main appliance to gather contextual information, can benefit from their own context data. In such scarce resource networks, the concept of context-awareness can be exploited either to optimize resource usage or to enhance the functional behavior of operating protocols. In this paper, we investigate the benefits brought by the concept of context-awareness when exploited in duty-cycled networks, since WSNs rely mainly on power saving mode in order to prolong the lifetime of sensor nodes. We focus mainly on the broadcast operation required for data collection and routing task. To quantify these improvements, we propose a comparative study relying on our ECAB protocol, using context-awareness jointly with a duty cycle mechanism to assure an efficient multi-hop broadcasting. To this end, we compare ECAB against protocols operating without context-awareness. Results show the effectiveness of this concept to improve network performances related to energy consumption, latency and packet delivery.

In Wireless Ad Hoc Networks, synchronization is a prerequisite to many basic operations such as frequency hopping, power saving, free contention channel access, clustering and security. Clock synchronization requires the availability of a common time reference for all mobile nodes. However, a synchronization algorithm cannot converge quickly to a stable point without considering the effects of collisions and channel interference inherent to wireless environments. In this paper, we propose a Fast Synchronization Protocol with Collision Handling for multi hop wireless ad hoc networks. Performance evaluation results show the ability of our algorithm to improve the convergence time and to assure the network wide synchronization accuracy even in highly dynamic scenarios.

Nowadays, the Peer-to-Peer (P2P) Video-on-Demand (VOD) systems knows a huge success for several reasons: a) each peer is both server and client leading to scalable system, b) it is not necessary to build and maintain infrastructures. BitTorrent is the most popular P2P file sharing protocols due to its effectiveness in the delivery of content. Thus, many VoD protocols have been proposed based on it. They investigate new ways for pieces and neighbor peers selections to assure the tight displaying time deadlines of video frames. In this paper, we present an up-to-date literature review of the main P2P VoD works based on the BitTorrent protocol. Furthermore, we propose a taxonomy of these works considering the pieces and the peers selection algorithms criterions.

Duty-cycling scheme consists in switching between active and sleeping modes. While this technique is widely exploited in WSNs to reduce power consumption, It raises several challenges especially for broadcast communications. In fact, as many neighboring nodes are involved in the communication, keeping them all active during a specific period of time requires a preliminary synchronization process which is a complex task and causes extra overhead. In this context, we propose an Efficient Context-Aware multi-hop Broadcasting (ECAB) over asynchronous duty cycled networks. ECAB exploits both the neighborhood knowledge and the traffic load conditions to regulate node behaviors and dynamically adjust duty-cycling schedules. Our objective is to reduce energy consumption without performances penalties. Simulation results show that ECAB outperforms RI-MAC and greatly improves energy consumption compared to broadcast under always-on networks with small degradation related to end-to-end delay and packet delivery.

Multipath routing has been widely used in wireless sensor networks to improve mainly the network performance by providing the load balancing capabilities. However, high correlated paths can throttle data transfer and can cancel the benefits of using multiple routes for data forwarding towards the sink. In this context, we propose a Fast Multipath Routing Protocol (FMRP), a query based multipath routing protocol which provides a simple mechanism during the discovery phase to construct node-disjoint paths while minimizing the impact of collision and interference. Thus, selecting less correlated paths allows a fluent data transfer and an efficient resources use. The good performance of our protocol in terms of more energy saving and better network throughput is witnessed by extensive simulations under various traffic loads and adopting different scenarios.

Wireless sensor networks (WSN) have received significant attention over the last few years as they afford a growing number of applications in various fields. At the same time, these networks provide numerous challenges due to their constraints, primarily related to energy scarcity. To overcome energy waste caused by collisions and contention based algorithm, the channel assignment mechanisms, like TDMA1, seem to be an effective way for scheduling node transmissions. To solve channel assignment problems, graph coloring theory has been exploited in many research works, primarily in order to assure collision-free communications. In this paper, we present a novel distributed coloring algorithm for WSNs taking into account the constraints of a real WSN environment. Our collision aware coloring algorithm assures a 2 hop nodes coloring, in a deterministic time execution, without requiring a neighborhood discovering phase. Performance evaluation results have shown the effectivness of our algorithm in terms of exchanged control packets per node as well as the chromatic number.

The intrinsic characteristics of ad hoc networks, such as the frequent connectivity changes and the strict bandwidth and power constraints, impose further challenges, especially for routing tasks. Besides, existing routing algorithms devoted to ad hoc networks and based on proactive or reactive schemes suffer from scalability due to their intrinsic mechanisms. The control overhead induced by routing packets is a primary factor, since it increases with the number of nodes, especially in large and dense networks evolving in a dynamic environment. Relying on a virtual infrastructure seems a promising approach to overcome the scalability problem. The basic idea consists on assigning additional tasks to a limited set of dominating nodes, satisfying specific requirements. In this paper, we present a routing algorithm, which exploits the benefits of our clustering algorithm TBCA. Conducted simulations show the ability of our new approach to reduce the control overhead and improve the reactivity of routing to the topology changes.

Designing power aware protocols becomes a pre-requisite to conserve energy and extend network life time. In fact, many target applications may require such features when being deployed for long periods in hostile environments, such as rescue or military operations. To assure power saving while preserving network capacity, relaying on a virtual backbone seems a promising approach. Through keeping a subset of nodes active for communication tasks, we allow other nodes to switch to sleep mode reducing consequently energy waste. However, the benefits of clustering come at a cost in terms of time and the prohibitive overhead incurred during the clusters' establishment and maintenance. In this paper, we investigate the influence of the underlying clustering algorithm on the performance of a power saving mechanism. The conducted simulations confirm the importance given to the choice of an efficient clustering algorithm to achieve energy efficiency while preserving network capacity.