Now a days Many car manufacturers are planning to install wireless connectivity equipment in their vehicles to enable communications with "roadside base station" and also between vehicles, for the purposes of safety, driving assistance, and entertainment. One distinct feature is that vehicles are highly mobile, with speed up to 30 m/s, though their mobility patterns are more predictable than those of nodes in Mobile Ad-hoc Networks (MANET) due to the constraints imposed by road, speed limits,

more »

... d commuting habits. Therefore, these networks require specific solutions and identify a novel research area, i.e., Vehicular Ad-hoc Networks (VANET). In this paper, we focus on a particular VSN architecture, where the ad hoc network is operated by a telecommunication/service provider to combine non-valuable individual sensed data and extract from them effective feedbacks about the situation of the road in a geographical area. In operated VSNs, providers tend to reduce the traffic load on their network, using the free-frequency communication medium (IEEE 802.11p, for example). To do so, we propose TCDGP (Tree Clustered Data Gathering Protocol), a cross layer protocol based on hierarchical and geographical data collection, aggregation and dissemination mechanisms. We analyze the performances of our solution using a simulation environment and realistic mobility models. We demonstrate the feasibility of such solution and show that TCDGP offers the operator precious information without overloading his network.