Research On Cooperative Scheme For Data Communication In Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks(VANETs) are distributed, self-organized Mobile Ad Hoc Networks(MANETs) which provide communication among vehicles and vehicles to Road Side Units(RSU) via wireless media. Compared to normal MANETs, VANETs are characterized with high mobility of the nodes, which is restricted by road direction,encompassing traf?c and traf?c regulations. As an important part of the Intelligent Transport System(ITS), on the one hand VANETs enable the vehicles to download contents form RSUs. On the other hand, the traf?c center may use VANETs to collect data about the road and vehicles.Previous research about downloading scheme in VANETs often regards the downloading process of different vehicles as independent parts, while they focus on the problem of network connectivity, download delay or throughput, they ignore the homogeneity of the content which will be downloaded by different vehicles, they also ignore the possibilities of the cooperation among vehicles in their downloading process; Previous research about data collection in VANETs either uses proactive ways such as periodical broadcast or modi?es those schemes in wireless sensor networks, unfortunately the former one increases network overhead while the later can’t suit the dynamic nature of VANETs very well.In this paper we ?rstly propose cooperative content downloading scheme in multihop VANETs(CMV). We aim to minimize the cost where a number of vehicles on the road are interested in downloading the same content from the RSUs. Our basic idea is to use a coalitional game model where the vehicles can download the content cooperatively in mutually disjoint coalitions. In each coalition, a vehicle called seed player is selected to download from the nearest RSU and shares with other coalition members. Each vehicle has a utility function which is determined by the download hop count, its position, speed and the cost of cooperation in each coalition. To compute the best coalition structure,a distributed coalitional formation algorithm is also proposed. Numerical results show that the proposed content download approach can achieve a considerable cost reduction compared with the non-cooperative method.We then propose ODDC, a novel On Dmand Data Collection scheme in VANETs.ODDC uses a reactive way to collect data, it contains three phases: query broadcasting,local data gathering and data aggregation. We enhance our scheme to adapt with vehicles’ mobility, density and the linear topology of VANETs. Simulation results show that the proposed scheme can collect data in a target area of highway with a light overhead, low collection duration and high collection accuracy.