Reliable On-Demand Geographic Routing Protocol Resolving Network Disconnection for VANET

High mobility of vehicular node which is one important feature of VANET makes high dynamics of topological structure for vehicular network, leads to frequently disconnection of multi-hop route in ad hoc network, and brings big challenges to reliability of routing algorithm and quality of data transmission. Thus we propose a position-based routing algorithm for VANET called on demand geographic routing (ODGR), which suits for highway scenarios. ODGR uses two new mechanisms to make sure information about positions of the destination nodes and neighbors valid and accurate when choosing next hop, and finally guarantee the reliability of routing algorithm: (1) ODGR uses two independent messages to realize update of position information about the destination. (2) ODGR uses the idea of on-demand to build the neighbor table. We compare the performance of AODV and ODGR using network simulator NS-2, with a specialized node mobility model simulator called VanetMobiSim to produce realistic vehicular movement trace. The final results prove that: on the highway, when node moves with acceleration of 4.9 m/s² and at max speed of 50 m/s, ODGR outperforms AODV by a factor of 1.7.