Research On The Street Attribute-based Routing In Vehicular Ad Hoc Networks

The development of distributed network applications in vehicular ad hoc network (VANET) urgently requires the support of efficient routing service, especially unicast and broadcast routing. The high mobility and the limited distribution by streets of vehicles result in frequent changes of topology and uneven distribution of vehicles. Traditional nodes-centric and topology-centric routing strategy in mobile ad hoc networks cannot meet the requirements of unicast and broadcast in the highly dynamic vehicular ad hoc network. The distribution and movement of vehicles are limited by streets, which is also the basic element of the entire network topology. Thus, the analysis and use of street routing attribute are the key issues for the optimization of routing in vehicular ad hoc network.For the unicast routing strategy, routing based on streets is more suitable for vehicular ad hoc network. Previous researches consider street length, vehicles density, and connectivity of streets as the routing attributes, however, they ignore the high mobility of vehicles, contention and interference in shared wireless channel, and the effect of existing data traffic. Moreover, they can hardly reflect the routing attributes of streets. For the broadcast relay selection, frequent changes of topology and unreliable wireless channel make the relay of broadcast uncertain. Due to the consideration of multi-hops topology or decision on receivers in existing studies, extra delay is induced in dynamic vehicular scenario, which can hardly meet the requirement of efficient broadcast.Thus, with the analysis and consideration of routing attributes of streets, we design efficient unicast and broadcast routing protocols in vehicular ad hoc network.(1)The key issue of unicast routing is the selection of street paths for data packets, and the selection of streets path depends on the analysis of routing attributes of streets. For the varying of the routing attributes of streets with time and location and the accurate analysis of routing attributes of streets, we propose a novel model named micro topology (MT) along streets composed by wireless communication nodes and the links among them along the street, which is the basic element of routing path and the entire network topology. With the consideration of vehicles mobility, channel contention and the effect of existing data traffic, we abstract the relaying strategy in the street and analyze the end-to-end routing performance in a micro topology, including successful delivery rate and delay. Based on the routing performance estimation in a micro topology, we combine the global geographical guidance and local dynamic optimization and design a novel unicast routing protocol RPMT.(2)The most key issue of multi-hops broadcast is the selection of relaying vehicle. First we combine the sender-based and receiver-based broadcast relaying method and design the broadcast protocol with prediction of dynamics BPD. For the optimizing of expected rebroadcast vehicle in BPD scheme, we consider the static attributes as global guidance and dynamic attributes as local optimization, and estimate the broadcast performance by selecting a neighbor as expected rebroadcast vehicle. For the optimizing of coverage delay and efficiency in multi-hops broadcast, we analyze and propose two metrics: expected remaining delay and rebroadcast efficiency, and the corresponding broadcast protocols BPD-D and BPD-E. We also achieve the theoretical analysis of multi-hops broadcast in a street, which is used in the numerical simulation.