Desastres naturales

Páginas: 17 (4016 palabras) Publicado: 7 de mayo de 2010
Adaptative Movement Aware Routing for Vehicular Ad Hoc Networks
N.Brahmi, M.Boussedjra
ESIGELEC-IRSEEM Technopôle du Madrillet 76801 Saint Etienne du Rouvray (33) 02 32 91 59 69

ESIGELEC-IRSEEM Technopôle du Madrillet 76801 Saint Etienne du Rouvray (33) 02 32 91 59 48

Data routing through vehicular ad hoc networks (VANET) remains a challenging task due to the high mobility of nodes which causes rapid topology changes and frequent disconnections. To address this issue, we exploit additional information about vehicle’s movement in order to adapt traditional position-based approach for such adynamic environment. Assuming that a vehicle is aware of its own movement as well as those of its direct neighbors, the proposed solution called Movement Aware Greedy Forwarding (MAGF) defines a new strategy to select next hop towards the destination. Based on a computed metric which is a combination of position, velocity and direction information, MAGF improves forwarding decisions with anoptimal next hop selection. Simulations results show significant performance improvement and proved the efficiency of the proposed solution compared to GPSR in terms of data delivery.

with each other as well as with the roadside infrastructure. The flexible deployment and the absence of energy constraints in VANET make this kind of communications attractive to beused in safety related applications and comfort services offered for roads users [1][2]. However, unlike in traditional mobile ad hoc networks (MANETs), the high speed of vehicles causes dynamic topology changes and makes network disconnections difficult to predict. As a result, the network behavior is greatly affected by these characteristics and many challenges have to be addressed while deployingthe aforementioned safety and comfort applications [3]. One major challenge relates to designing an efficient routing protocol for vehicular environment since a reliable route should be ensured to send data from a source to a destination under changing link connectivity. A comparison study of routing protocols described in [4] has demonstrated that traditional ad hoc routing protocols(topologybased and position-based approaches) are not suitable for VANETs. They fail to fully address the specific needs of a dynamic environment. The topology-based protocols, such as DSR [6], DSDV [7] and AODV [8], maintain routing information about the available or the used paths in the network which may occupy a significant part of the bandwidth. Moreover, the route instability and frequent topologychanges increase the overhead for path repairs or changes notifications and consequently degrades the routing performances. The class of position-based routing protocols, such as GPSR [5], offers an alternative approach known to be more robust in face to mobility [9]. Indeed, no global knowledge of the network topology is required; a purely local decision is made by each node to forward data to theclosest neighbor to the destination. Ideally, this process can be repeated until the packet is delivered. Unfortunately this is not always possible; a packet could not be forwarded if its current forwarder node does not have a neighbor geographically closer to the destination than itself. This problem, known as local maximum [5], occurs often in road intersections because position information doesnot always point to the right direction leading to a wrong forwarding decision. The absence of mobility prediction also prevents a node from detecting the unavailability of some neighbors. With these shortcomings, the position-based routing still needs some improvements to match the requirements of vehicular applications.

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