面向城市VANETs的多跳警告广播协议

摘要

To improve dissemination toward all directions and decrease duration that message is forwarded,in this paper,the multi-hop broadcast for warning protocol in urban VANETs is proposed.The roads which wireless signal cover every time areclassified into four directions:east,south,west and north.Relay node at the intersection is decided by following rules:first,it has at least two neighbor nodeswhosedirections are different to the relay node,and the distances between relay nodeand the neighbors are more than the width of road.Second,its ID is the smallest among the nodes at the intersection.Relay nodes at intersections prioritize to forward messages without waiting.Relay nodes on the road are selected according to waiting-time equation and message is rebroadcasted if waiting time ends.MBW supports that message is propagated in both directions along the road.Due to relay node selection strategy,the number of relay nodes and message retransmissions is decreased.Simulation results show that MBW offers better coverage,lower delay,lower forwarding nodes ratio and lower overhead compared to exiting broadcasting protocols in VANETs.%为改善道路交叉口处信息向所有方向分发的可靠性以及降低信息分发时延,提出面向城市车载网络多种交通密度、基于位置的多跳警告广播协议MBW.本协议把无线信号一次发射覆盖的道路分为东、南、西、北4个方向.道路交叉路口的中继节点满足两个条件:首先,一个节点至少有两个邻居节点,该节点及邻居的行驶方向都不同,并且与邻居节点之间的距离都大于路宽;其次,ID号在交叉口的节点中最小,交叉路口处中继节点优先广播信息不等待.道路上的中继节点根据WT 公式确定,WT 值为零时转发信息,并定义此节点为中继节点,本协议支持信息在路上双向传输.MBW协议的中继节点选择策略能够减少中继节点个数和信息分发冗余.仿真结果表明MBW协议和现存的VANETs广播协议相比具有较好的高覆盖率、低延迟、低转发节点率和较低的网络开销.