Research And Improvement Of Hybrid Routing Protocol In Vehicle Ad Hoc Network

With the development of intelligent transportation systems, communication between the carand car through the vehicular Ad hoc network also gets much more attention. As a special form ofmobile Ad hoc network, vehicular Ad hoc network not only has the entire characteristics of mobilenetwork (e.g., self-organization, multi-hop routing, dynamic network topology), but has some owncharacteristics，such as the high-density and high-speed distribution characteristics of the mobilenode which will directly affect the information transmission capacity of the network, packet lossrate and transmission delay.How to improve the routing reliability of the vehicular Ad hoc network has become one of thefocuses. In this paper, we pay attention to the research of hybrid routing protocol. According to thedefects of the existing hybrid routing protocol SARP, such as unstable performance, routing hole,etc., we first present an enhanced hybrid protocol called E-SARP based on the location information.Compared with SARP, E-SARP chooses the best nodes based on the location, distance and velocityof the adjacent vehicles. Besides, the counter we add in E-SARP will reduce the delay in SARP. Thesimulation results in NS-2show that our E-SARP has better performance in packet loss rate andtransmission delay.In addition to the E-SARP, we put forward another hybrid routing protocol called HVAR. Itcombines the on-demand routing protocol with the greedy forwarding algorithm. The HVAR willfirst use the greedy algorithm to forward the packets, if the routing hole happens, then it willforward route request packet to all neighbor vehicles. The improved protocols also optimize thelocal repair mechanism: if the link is down when routing hole happens, the previous vehicle willreplace the wrong vehicle with the one which is nearest to the correspondent vehicle in the neighborlist. The simulation results in NS-2shows that the HVAR performs better than the on-demandrouting protocol.