Building a Landmark Overlay Network on Top of an Urban Topology

1556-6072/09/$25.00©2009IEEE IEEE VEHICULAR TECHNOLOGY MAGAZINE | MARCH 2009 We introduce a routing solution called landmark overlays for urban vehicular routing environments (LOUVRE), an approach that efficiently builds a landmark overlay network on top of an urban topology. We define urban junctions as overlay nodes and create an overlay link if and only if the traffic density of the underlying network guarantees the multihop vehicular routing between the two overlay nodes. LOUVRE contains a distributed traffic density estimation scheme that is used to evaluate the existence of an overlay link. Then, efficient routing is performed on the overlay network, guaranteeing a correct delivery of each packet. We evaluate LOUVRE against the benchmark routing protocols of greedy perimeter stateless routing (GPSR) and greedy perimeter coordinator routing (GPCR) and show that LOUVRE performs higher in packet delivery and achieves lower hop count. The ever-growing spread of vehicles and roadside traffic monitors with the advancement of navigation systems and the low cost of wireless network devices provide incentives for car manufacturers to equip vehicles with real-time traffic reports, promising peer-to-peer (P2P) applications, and externally driven services to vehicles. However, for these applications and services to materialize, there is a need for standards of ubiquitous high-speed communications and homogeneous communication interfaces among different automotive manufacturers. For this purpose, the Intelligent Transportation Systems (ITS) have proposed the wireless access in vehicular environments (WAVE) standards that define an architecture that collectively enables vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless communications [1]. In order to enable multihop wireless vehicular communications, vehicles are equipped with WAVE devices and interconnected with one other to form a vehicular ad hoc network (VANET), which is a particularly challenging class of mobile ad hoc networks (MANETs). VANETs are distributed, self-organizing networks built from moving vehicles, and are thus characterized by very high speed, a strong nonuniform distribution of vehicles, and a Building a Landmark Overlay Network on Top of an Urban Topology