In Vehicular Ad-hoc Networks ( VANETs) ,the lack of request-to-send/clear-to-send handshaking and response mechanism makes communication less reliable,which will cause serious consequences in emergency message transmission. Aiming at this problem, first a performance analysis model of safety message dissemination in VANETs with priority was proposed,then figured out the probabili-ty of transmitting status and emergency messages in a random slot respectively. In addition,the probability of a slot in busy condition is figured out. Furthermore,determined average transmission delay of emergency messages in the presence of status messages. Finally,the numerical analysis is validated by simulation,which indicates the model is helpful to select appropriate network parameters to reduce the delay of emergency messages transmission and study other performance in VANETs.%车载自组织网络中,由于没有RTS/CTS握手机制和应答机制,使得通信可靠性降低,这在紧急消息的传输中会带来严重后果. 针对该问题,首先提出车载自组织网络中具有优先级的安全消息传输性能分析模型;然后利用该模型分别计算出任一时隙传递状态消息和紧急消息的概率以及信道忙的概率;在此基础上分析出状态消息存在的情况下紧急消息的平均传输时延;最后对理论分析进行仿真验证. 仿真结果与理论分析具有很好的一致性,表明了该模型对选取合适的网络参数来减小紧急消息的传输时延及进一步研究车载自组织网络的其他性能具有一定的参考价值.
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