Research On The Instantaneous Topology Of Urban Vehicular Ad-Hoc Network And Routing Strategy

Vehicular Ad Hoc Network, shorten as VANET, is supposed to be an important component in the intelligent transportation system(ITS) which integrates ad hoc network, WLAN and cellular technology to provide innovative services for public and improve the safety and efficiency of daily traffic. In VAN ET, vehicles equipped with Dedicated Short Range Communication devices can exchange message directly or indirectly with other vehicles(vehicle-to-vehicle communication), and exchange message with roadside infrastructure(vehicle-to- infrastructure communication). Namely, VANET can provide a number of potential services for public such as vehicle collision warning, real-time traffic jams reporting, and so on.End-to-end communication is extremely important between moving vehicles in a variety of applications and services VANET-based. Services based on this requirement would sorely depend on mobility features, especially on the dynamic changes of network topology caused by high-speed mobility of vehicles. Bunches of study results focusing on the characteristics of network topology come from theoretical models. Theoretical mobility models can simplify problem analysis, however, they are inconsistent with the reality. This paper explores the characteristics of node mobility and VANET topology based on two real vehicle trajectory datasets.Firstly, we introduce the features of datasets and key matric of node mobility: inter-contact time(ICT), residual IC T and degree centrality. We found that ICT was the exponential decay of the light-tailed distribution. Then we define waiting time ratio(WTR) and good nodes ratio(GNR) and present Analysis of the impact of uncertainty on the vehicle node transmission delay.Secondly, we let the network become an undirected graph with a timestamp, using the data set to explore the temporal variation characteristics of the connected component, we find that the whole network consists of a large number of connected components(CC), the vast majority of connected component contained in the number of nodes is very small. However, the biggest CC contains most of vehicles and stays relatively stable. And the number of nodes of biggest CC stay stable in low or peak traffic periods, we proposed the concept of CC stability factor to measure the degree of change in the node members. Finally, we introduce the classic algorithms k-core decomposition of complex network, to find the largest component of k-core.Finally, we design the FMK strategy, RIC T strategy and routing strategy based on CC. We find that end-to-end communication is independent of the initial location of S-D node pair. After tests we found RICT has a better performance.