Research On Multi-hop Based Messages Dissemination Algorithms In Vehicular Ad Hoc Networks

In recent years, the number of vehicles is growing rapidly in China, which has brought a lot ofproblems to urban traffic and makes Vehicular Ad hoc NETwork (VANET) technology be attractedmuch attention. Through free inter-vehicle networking and communication, VANET can effectivelytransmit information in real-time, like traffic safety related information, road conditions and evenentertainment message, to solve traffic safety, road congestion and other problems. However, due tothe uniqueness of network and different performance requirement of applications, it is impossible todesign a message distribution algorithm applicable to all scenarios. This thesis focuses on multi-hopbased message distribution algorithm under different scenarios in VANET.Firstly, for the traffic safety and traffic conditions related scenarios, this thesis proposes aNeighbor Information-based Multi-hop Broadcasting Suppression (NIMBS) algorithm. It usesvehicles’neighbor information as well as position, speed and direction of vehicle to form an orderedsequence of neighbors, and finally calculates forwarding latency of each forwarded vehicle.Simulation results show that compared to similar suppression algorithms, NIMBS gives lowerpackets loss rate, lower transmission delay and better scalability and effectively solves scalability,redundancy and broadcast storms of broadcast scheme.Secondly, under the free-flow state, this thesis studies a multi-lane connectivity probabilityanalysis model based on vehicle’s speed. The model converts the actual multi-lane scene into avirtual one that all vehicles of each lane have the same speed, and deduces the exact connectivityexpression on the basis of previous work. Simulation results show that this model is consistent withthe actual situation.Finally, for peer to peer scenarios, this thesis proposes a Connectivity Probability-AwareMulti-hop (CPAM) message dissemination algorithm based on the analysis model. It uses theabove-mentioned model to calculate connectivity probability of each road segment and selects thebest one to forward packets. Then, CPAM precedes NIMBS to transmit packets from the selectedsegments to another one. Simulation shows CPAM gives better performance of packets deliveryratio and transmission delay than GPSR with buffering mechanisms.