Vehicular Ad-Hoc Networks (VANETs) as a part of intelligent transportation systems (ITS) are a\nnew perspective to settle the traffic problem. Because of the high velocity, variational topology\nand such other characters, the link between VANETs and road side unit (RSU) is unstable. Besides,\non account of the high cost of RSU, some places can�t be covered completely which make the Internet\naccessing difficult and accessing delay long. In this paper, we propose a hierarchical link\nscheme to help vehicles access the Internet based on delay analysis for congestion scenario. We\nselect some moving accessing help points (AHPs) from vehicles in VANETs. Two different hierarchical\nschemes under the circumstances of whole road covered or not are proposed. When the\nRSUs are enough to cover the whole road fully, we propose the inward progressive hierarchical\nmethod. When the RSUs are not enough to cover the whole road, we propose the outward extend\nhierarchical method. According to the delay analysis, we can get the optimal hierarchy number.\nThis hierarchical link scheme can decrease delay and make all vehicles access the Internet with\ndelay guarantee. The simulation results indicate that our proposed hierarchical link scheme in\nVANETs can decrease the link delay effectively.
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