An improved routing metric based on link states for vehicular ad hoc networks

Greedy forwarding is widely adopted in geographic routing protocols for VANETs since it selects the neighbor that is geographically closer to the destination as the next hop and is considered efficient. Because of the highly dynamic network topology and various impairment of radio signal, the link chosen according to the greedy algorithm regardless of the link state is unstable to a large extent, and frequent retransmissions lead to a waste of the network bandwidth and longer end to end delay. To address the issue, the paper proposed a new routing metric called expected one-transmission advance (EOA) to select the next hop to construct the route. The EOA of a certain node means the expected advance that a packet can make towards the destination through one transmission if choose the node as the next hop. The node with largest EOA is chosen as the intermediate node. The EOA metric balances the efficiency and reliability of the routing. We evaluate the performance of EOA by simulation and the result demonstrates significant reductions of end to end delay and increases of throughput compared to the traditional geographic routing protocol using greedy forwarding.