Research On Broadcasting Algorithms For Urban Scenarios In Vehicular Ad Hoc Networks

VANETs(Vehicular Ad hoc Networks)is a key application of mobile ad hoc networks for intelligent transportation systems.It has become a hot research area for both national and international scholars.In VANETs,broadcast can quickly and efficiently forward broadcast packets to neighbor vehicles and disseminate to the entire network.Therefore,broadcast is currently a necessary communication approach to transmit the information of traffic congestions and traffic accidents.In order to suppress broadcast storm,reduce delay,and improve broadcast reliability,a Direction and Distance Based Broadcast algorithm(DDBB)for urban scenarios in VANETs is proposed.Firstly,the forwarding mode is divided into two types according to the actual situations of the urban roads:the forwarding mode of direct path scenarios and the forwarding mode of crossing scenarios.A node automatically switches the forwarding modes according to the position states of itself and the previous hop node.Secondly,in the two forwarding modes,roads are divided into different sectors according to the direction of the roads without considering the number of lanes,the width of the lane,and the intersection specification(such as crossing,T-junctions or roundabouts,etc.).Each node selects a node in each area as the next hop forwarding node.Therefore,the number of nodes participating in forwarding broadcast packets is reduced.Meanwhile,the next hop forwarding nodes selected do not converge in the same sector.As a result,broadcast storm is alleviated,delay is reduced and reliability is improved.Thirdly,the neighbor nodes with the farthest distances in the areas where the nodes move away from the current node are selected first.By this scheme,the additional broadcast coverage is increased,which results in the broadcast storm mitigation.Fourthly,neighbor information is exchanged by broadcast packets and the additional frame type is not required,which further alleviates the packet competition and collisions.The performance of the DDBB algorithm is demonstrated by the simulations.The results show that DDBB has better performance in terms of ratio of forwarding nodes,average end-to-end delay and reachability.The DDBB algorithm can be universally employed to the real urban scenarios.