Abderrahim Benslimane

Dynamic Clustering-Based Adaptive Mobile Gateway Management in Integrated VANET — 3G Heterogeneous Wireless Networks

Coupling the high data rates of IEEE 802.11p-based VANETs and the wide coverage area of 3GPP networks (e.g., UMTS), this paper envisions a VANET-UMTS integrated network architecture. In this architecture, vehicles are dynamically clustered according to different related metrics. From these clusters, a minimum number of vehicles, equipped with IEEE 802.11p and UTRAN interfaces, are selected as vehicular gateways to link VANET to UMTS. Issues pertaining to gateway selection, gateway advertisement and discovery, service migration between gateways (i.e., when serving gateways lose their optimality) are all addressed and an adaptive mobile gateway management mechanism is proposed. Simulations are carried out using NS2 to evaluate the performance of the envisioned architecture incorporating the proposed mechanisms. Encouraging results are obtained in terms of high data packet delivery ratios and throughput, reduced control packet overhead, and minimized delay and packet drop rates.

Optimized Dissemination of Alarm Messages in Vehicular Ad-Hoc Networks (VANET)

In this paper, we propose a new scheme to disseminate alarm messages between vehicles in order to prevent pile-up of cars when fogs, accident or any other obstacle. Communications between vehicles constitute a Vehicular Ad hoc Network (VANET). Contrary to MANET, in VANET nodes which are vehicles can move with high speed and generally must communicate quickly and reliably. When an accident occurs in a road or highway, alarm messages must be transmitted to inform all other vehicles. However, a classical routing or multicasting protocol as in MANET cannot be used since it must first discovers routes and constructs for each node its neighbors. This task take many time so it is not adapted to disseminate unexpected information such as prevent crash. Also, a classical broadcast cannot be used since it causes a protocol overhead and high number of message collisions. To overcome these limitations, we introduce an efficient dissemination of alarm messages while restricting re- broadcast to only special nodes, called relays, and in restricted zones, called risk zones. By simulations, we shows that this method is efficient and reduce the overhead compared to existing solutions. So, it is reliable and scalable.

Toward an Effective Risk-Conscious and Collaborative Vehicular Collision Avoidance System

In this paper, we introduce a cooperative collision-avoidance (CCA) scheme for intelligent transport systems. Unlike contemporary strategies, the envisioned scheme avoids flooding the considered vehicular network with high volumes of emergency messages upon accidental events. We present a cluster-based organization of the target vehicles. The cluster is based upon several criteria, which define the movement of the vehicles, namely, the directional bearing and relative velocity of each vehicle, as well as the inter-vehicular distance. We also design a risk-aware medium-access control (MAC) protocol to increase the responsiveness of the proposed CCA scheme. According to the order of each vehicle in its corresponding cluster, an emergency level is associated with the vehicle that signifies the risk of encountering a potential emergency scenario. To swiftly circulate the emergency notifications to collocated vehicles to mitigate the risk of chain collisions, the medium-access delay of each vehicle is set as a function of its emergency level. Due to its twofold contributions, i.e., the cluster-based and risk-conscious approaches, our adopted strategy is referred to as the cluster-based risk-aware CCA (C-RACCA) scheme. The performance of the C-RACCA system is verified through mathematical analyses and computer simulations, whose results clearly verify its effectiveness in mitigating collision risks of the vehicles arising from accidental hazards.

Fast track article: An efficient routing protocol for connecting vehicular networks to the Internet

Vehicular ad hoc networks (VANETs) enable vehicles to communicate with each other (V2V) as well as with roadside infrastructure units (V2I). These units provide different services such as driver information systems and Internet access. The high speed and high mobility of vehicles make it very challenging to establish and maintain a connection to these units. We introduce a new protocol which uses the characteristics of vehicle movements to predict the future behavior of vehicles, and to select a route with the longest lifetime to connect to the wired network. The proposed protocol aims at spreading the advertisement messages through multi-hops without flooding the network and performing seamless handovers. The proposed protocol is simulated by considering mobility scenarios, generated by the MOVE tool, in the ns-2 simulator tool. The simulation results show that the proposed scheme increases the packet delivery ratio and decreases the packet delay and overhead.

High accuracy localization method using AoA in sensor networks

In sensor networks, several applications such as habitat monitoring and moving objects tracking, require the knowledge of nodes positions. Position estimation most often includes errors due to the measurements of distance and incoming angles between neighbors. Erroneous positions are propagated from a node to other nodes exacerbating the degree of errors in the estimation of the positions of these nodes. In this paper, we propose a new localization method, called HA-A2L (High Accuracy localization based on Angle to Landmark); it consists of (a) a new protocol that allows nodes to exchange information pertinent to the localization process; and (b) a localization algorithm that uses estimation of distances and incoming angles to locate nodes in sensors networks. Compared, via simulations, to previous methods, such as APS and A2L, HA-A2L considerably increases the number of located nodes with far better accuracy.

Enhancing IEEE 802.11 Random Backoff in Selfish Environments

Wireless access protocols currently deployed in mobile ad hoc networks use distributed contention resolution mechanisms for sharing the wireless channel. In such an environment, selfish hosts that fail to adhere to the medium access control (MAC) protocol may obtain an unfair share of the channel bandwidth at the expense of performance degradation of well-behaved hosts. We present a novel access method, called predictable random backoff (PRB), that is capable of mitigating the misbehavior of selfish hosts, particularly hosts that deliberately do not respect the random deferment of the transmission of their packets. PRB is based on minor modifications of the IEEE 802.11 binary exponential backoff (BEB) and forces each node to generate a predictable backoff interval. The key idea is to adjust, in a predictable manner, the lower bound of the contention window to enhance the per-station fairness in selfish environments. Hosts that do not follow the operation of PRB are therefore easily detected and isolated. We present an accurate analytical model to compute the system throughput using a 3-D Markov chain. We evaluate the performance of PRB under the normal case and in the presence of selfish hosts. Our results show that PRB and BEB similarly perform in the former case. Selfish hosts, however, achieve substantially higher throughput than well-behaved hosts under BEB. PRB, on the other hand, can effectively enhance IEEE 802.11 BEB by mitigating the impacts of these MAC selfish misbehaviors and guarantee a fair share of the wireless channel for well-behaved hosts.

MAC layer misbehavior in wireless networks: challenges and solutions

IEEE 802.11 CSMA/CA has been widely deployed as the primary MAC protocol for ad hoc networks and wireless LANs. It was designed with the assumption that nodes would follow proper operation of the protocol. Nodes, however, may choose to deviate in order to either obtain an unfair share of the available bandwidth or disrupt the services of the network. Accordingly, a misbehavior rooted at the MAC layer can be classified as selfish or malicious behavior. This article surveys the research activities related to MAC layer misbehavior; based on the operating principles and the objective of misbehaving nodes, we classify MAC layer misbehavior and present descriptions for each solution. We conclude with a brief summary of the key ideas and a general direction for future work.

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.

Design Guidelines for a Network Architecture Integrating VANET with 3G & beyond Networks

Vehicle Ad Hoc Networks (VANETs), based on IEEE 802.11p, and 3G & beyond networks are characterized by their high date transmission rates and wide range communication, respectively. This paper presents an architecture that integrates between the two, making advantage of the features of each. Design guidelines pertaining to vehicle clustering and gateway management are defined. The former aims for enhancing the link stability within the VANET, whereas the latter sustains inter-connectivity of the VANET with the backhaul 3G & beyond network. Simulations are carried out using NS2 to evaluate the performance of the integrated network architecture and encouraging results are obtained in terms of high data packet delivery ratio, reduced control packet overhead, and reduced packet drop rate.

A lifetime-based routing protocol for connecting VANETs to the Internet

Inter-Vehicle Communications have recently attracted research from both academia and industry. In such networks, vehicles should be able to communicate among each other (V2V) as well as with roadside Infrastructure units (V2I). These units provide some services such as driver information systems and Internet access. Because of the high speed and high mobility of vehicles, establishing and maintaining a connection to these units is very challenging. We introduce a new protocol which uses the characteristics of vehicle movements to predict the vehicle behavior and select a route with the longest life time to connect to the wired network. It aims at spreading the advertisement messages through multi-hops without flooding the network, do seamless hand-overs and select the most stable routes to these units. We performed some simulations and compared the performance of our work with some well-known protocols.