中文摘要：

为提高城市车辆自组织网络（VANETs）安全信息广播的有效性，提出了一种基于区域分组的安全信息广播协议（AGBP）。该协议采用正三角形法或正六边形法给中继节点每跳覆盖的区域平均分割，节点按照所在的区域分组。正三角形和正六边形顶点为中继节点的最佳位置，每一组内所有的节点根据自己和中继节点最佳位置的距离计算等待时延，由等待时延决定每一组内的中继节点并转发信息，因此信息可以同时沿着多个方向多条路转发。与传统的沿着一条道路转发信息的广播协议相比，该协议能够避免因分组不当造成信息冗余和碰撞，致使信息的传输效率下降，从而能够降低网络开销、链路时延和转发节点率，提高覆盖率。

英文摘要：

To improve the effectiveness of the safety message broadcast in urban vehicle ad hoc networks （ VANETs）, an area-grouping based broadcast protocol for safety message dissemination （AGBP） is proposed. The AGBP adopts the equilateral triangle method or the regular hexagon method to equally segment the area the relay node covers per hop, and groups vehicles according to the area in which they are. The vertexes of equilateral triangles and regular hexagons are the best position of the relay node, and all nodes in each group calculate the waiting time （WT） ac- cording to the distance from them to the best position of the relay node. The WT decides the relay node for forward- ing messages in each group, so messages can be disseminated along many directions and roads at the same time. Compared with the traditional broadcast protocol along only one road, the AGBP can avoid the data redundancy and collision caused by misclassification, so it can decrease the overhead, the link delay and the ratio of forwarding nodes, and improve the coverage.