A Study Of Multi-Priority Opportunity Directional Routing For VANETs

Vehicular ad hoc network is obviously affected by environment and has high mobility of vehicular node: in downtown scenarios, obstacles make vehicular node hide with each other. In highway scenarios, high mobility of vehicular node makes high dynamics of topologic structure for vehicular network. Those problems directly lead to frequently disconnection of multi-hop route in ad hoc network. All of them bring big challenges to reliability of routing algorithm and quality of data transmission.In this paper, a position-based routing algorithm for VANET called multi-priority opportunity directional routing (MPODR) is proposed. MPODR uses opportunity directional forwarding strategy to make some copies for the same data packet, and overcomes the influence brought by obstacles and network partitioning. Each node uses random delay strategy to send data packets to reduce the sending collision and make effective use of channels. Forwarding and destination nodes use hash to search the packets being received, and make sure dealing with the repeated packets timely. Using this, we can reduce the cost of network channels. MPODR is combined with 802.11p protocol, so it adds the function to dispose the high priority packets of security alarms, and improve the ability of routing protocol to dispose multiple priority levels.In this research, we compare the performance of GPSR and MPODR using network simulator NS-2. A specialized node mobility model simulator called VanetMobiSim is used to produce realistic vehicular movement trace. The final results of the research prove that: in the downtown, when nodes move at acceleration of 1 m/s2 and at max speed of 13m/s; on the highway, when node moves at acceleration of 3m/s2 and at max speed of 35m/s, the packets losing rate of MPODR is ten times lower than GPSR and MPODR controls the delay of high priority packets under 300ms.