Research On The Brodcasting Protocol Based On Time Stamp And Rsu In Vanet

Until now, most research for VANET has focused on broadcasting protocols under the high-density network topology, these studies are carried out based on simplistic VANET network which connect well. However, the network disconnecting is a common problem in VANET, and therefore need to develop a reliable and efficient broadcasting protocol to support diverse network topology.Based on the analyzation on the process of SCF (Store-Carry-Forward), SCB (Store-Carry-Broadcast) system, they are simply rely on the vehicle traveling in the opposite direction to realize the disconnected car-car communications, the waiting time that the vehicle in cluster tai encounter the forward in the opposite direction can not be guaranteed, so the message propagation delay could be very long. On this basis, use of fixed facilities RSU, proposed broadcasting protocol aims to shorten the re-healing time between nodes. The main problem related to the thesis are:First, RSU-based Broadcasting Protocol:when studying the the transmission problem of data packets in VANET, it is very important to separate the following two kinds of different situations:first, the source of the vehicle generate a warning message after it detected an accident, and its spread to the rear of the vehicle, they can get this warning message before reaching the potential danger zone; when the target away from the source of the vehicle (ie, a few kilometers or tens of kilometers away sender), Scenario2occurs-sending a message to a particularly far node.Then, the calculation of backoff delay based on time stamp:the main idea of the algorithm is, the source node add the transmission time stamp to the message, each node calculations the appropriate backoff delay after receiving the message, and after the wait time, confirm the next step and continue broadcasting; If the node received a confirmation from other nodes within the time, then give up the radio again. The acknowledgment mechanism are used for suppressing radio broadcast of the other nodes.Last, computing the re-healing time (re-healing time, short):the re-healing time is the time passing messages between two temporally adjacent clusters.By QualNet simulation experiments, compared with SCB, SCF mechanism. The results show that the re-healing time are greatly reduced after applying RSU, and improve the timeliness and reliability of broadcasting.