| Summary: | 碩士 === 國立暨南國際大學 === 資訊工程學系 === 101 === VANET (Vehicular ad-hoc network) is a popular research issue recently. Safety applications are very important in the VANET field. Multi-hop broadcast method is widely used in those applications. There are a lot of benefits in VANET such as broadcasting the vehicular information to neighbor vehicles which can reduce the traffic congestion and avoid the car accident getting worst. Or transmit the data of entertainment to each other. The purpose of this research is to forward the emergent message to the vehicle which has some distance between accident vehicle as soon as possible. In this paper, we propose two protocols to reduce the latency of emergent packet delivery, one is BCUnit and the other is STAGI. In BCUnit and STAGI mechanism, each vehicles notice those which behind itself according to their location. Firstly, in BCUnit protocol, the transport mechanism is when vehicles received emergent packet, it will calculate the Back-off time which is based on distance between sender and receiver. Follow this transport mechanism, the farthest vehicles from sender will get least Back-off time value. Secondly, the transport mechanism in STAGI is that vehicles will get different random Back-Off time value from different Back-Off time region according to the location of vehicles. In other words, the IV communication range of vehicles wireless communication device has been divided into several partitions. Each partition has been distributed different random Back-Off time value range. The furthermost partition from the sender has the minimal random Back-Off time range. In addition to those mention above, STAGI will choose a vehicle be the first one to transmit the packet. If the packet was lost in the delivery process the other vehicle will send this packet. Other vehicle would transmit the packet to improve the successful
ration of packet delivery. The selection of emergent packet forwarding vehicle of next hop based on slot time distribution and geographic information. In simulation result, the successful ratio of packet delivery and the latency of packet delivery are better than other protocols
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