基于空分多址的车联网信标消息同步广播协议

摘要

依据车联网中专用短距离通信DSRC协议的标准,车辆通过周期地广播包含车辆状态信息的信标消息,实现邻居节点感知的链路层服务,并且信标消息以随机方式共享传输安全消息的控制信道.然而,这种方式可能导致严重信道竞争和数据丢失,降低邻居节点感知率.为此,提出基于空分多址的信标消息同步广播协议SDMA-SB.通过SDMA-SB协议,使得车辆以分布式方式同步地广播信标,实现车辆在同一个信标时区内有序地广播,降低信道竞争概率,进而提高邻居节点感知效率.SDMA-SB协议先建立有序化的道路模型,然后依据距离信息为同一路段车辆选择一个控制信道间隔CCHI作为信标时区,再根据距离计算广播信标所需的等待时间,并保证车辆等待时间的惟一性.仿真结果表明,与传统的信标广播协议相比,提出的SDMA-SB协议提高了邻居感知率以及信息的新鲜度.%According to the standard of the dedicated short-range communication(DSRC)protocol in vehicular Ad Hoc net-works(VANETs),the vehicle can realize the link-layer service of neighborhood discovery by broadcasting the beacon informa-tion including vehicle status information periodically. The beacon information shares the control channel(CCH)transmitting safe-ty information with random mode,which may cause the severe channel competition and packet loss,and reduce the neighbor-hood-discovery ratio. Therefore,a space-division multiple access based synchronized beacons(SDMA-SB)sending protocol is proposed,with which the vehicles can broadcast the beacon synchronously in distributed mode to realize its sequential broadcast in the same beacon time zone,reduce the channel competition probability,and improve the neighborhood-discovery ratio. The ordering channel model is constructed with SDMA-SB protocol. According to the distance information,a control channel interval (CCHI)is selected for the vehicle in the same path section as the beacon time zone. The waiting time needed by the broadcast beacon is calculated according to the distance to guarantee the uniqueness of vehicle waiting time. The simulation results show that,in comparison with the traditional beacons broadcast protocol,the SDMA-SB protocol can improve the neighborhood-discovery ratio and information freshness efficiently.