Abstract: The relay node needs to be found in the range of forwarding when packets data is forwarded.In order to reduce the complexity of searching relay nodes and the average number of hops from source node to destination node in the process of forwarding,an adaptive routing protocol based on directional transmission in vehicular ad hoc networks was proposed.Forwarding angle and the average distance of one-hop progress are the two key parameters of the routing protocol.Firstly,in order to reduce the forwarding range,a forwarding angle always to awards the destination node is designed,which can reduce the number of nodes in the forwarding range and simplify the calculation of searching relay nodes.And then,in order to reduce the average number of hops,optimal or sub-optimal neighbor nodes are chosen adaptively as relay node based on the distance of progress in the forwarding range.Simulation results show that compared with the OBDR,the proposed adaptive routing protocol is superior in terms of both the average number of hops and the average distance of one-hop progress,with which the data packets can be transmitted quickly to the destination node.

Key words: Vehicular Ad hoc network,Routing protocol,Average number of hops,Average distance of one-hop progress