【摘要】 车载网(vehicular ad hoc networks,VANETs)中多数安全应用常采用多跳广播协议传输安全消息,然而,现有的多跳广播协议存在时延和碰撞问题。为此,首先强调并分析了现有协议所忽略的碰撞和时延问题,然后提出了基于位图的多跳广播协议(bitmap-based multi-hop broadcast,BMB)协议以解决这两个问题。为了降低时延,BMB协议允许候选转发节点以反比于它的转发优先权设置等待时间,而转发优先权依据空闲空间分布(empty space distribution,ESD)位图设置。ESD位图反映着车辆间的空间分布。其次,BMB协议推导了两个相邻候选转发节点间等待时间的最小间隔,基于此间隔,BMB协议调整各候选转发节点的等待时间,保证两个节点间的等待时间差大于此间隔。仿真结果表明,与STF相比,提出的BMB协议具有低的转发时延和碰撞概率。更多还原

【Abstract】 Many Safety applications rely on multi-hop broadcasting to disseminate safety messages. However,there are latency and collision problem in existing protocols. Therefore,firstly,the collision and latency problems which existing forwarding schemes overlooked was highlighted and analyzed. Secondly,the BMB protocol is proposed to tackle the collision and latency problems. The first problem of unnecessary delay was solved by allowing a forwarder candidate to use the waiting time which is inversely proportional to its forwarding priority. The forwarding priority was acquired by using ESD bitmap,which describes the distribution of empty spaces between vehicles.BMB protocol finds out the minimum difference between waiting times of two adjacent vehicles. Based on the minimum difference,BMB protocol adjusts the waiting times of forwarder candidates for guaranteeing that the waiting time difference between any two vehicles is larger than minimum difference. Simulation results show that proposed BMB protocol outperform than STF in terms of latency and collision probability.更多还原