| Summary: | 碩士 === 國立臺灣大學 === 資訊工程學研究所 === 100 === Recently, the applications of Vehicular Ad-hoc Networks (VANETs) in many existing researches have mainly been related to information distribution and traffic safety. However, in the researches that aim at designing the network protocols and systems for VANETs, performance evaluation usually does not utilize realistic traffic flow data; therefore, the derived design might actually not perform well in the real world. In VANETs, the nodes, i.e., the vehicles, have many unique features: they have high mobility, and the topology often changes rapidly; the movements of the vehicles need to follow the general traffic rules and obey the traffic signs. As a result, how realistic the traffic mobility model is can have significant impact on whether the simulations of VANETs are sufficiently realistic.
The main goal of this thesis is to build an integrated simulation framework, which can be utilized to study the Inter-Vehicle Communications (IVC) in VANETs. The framework integrates a traffic mobility simulator and a network simulator; in the framework, the traffic mobility simulator generates realistic traffic mobility information, such as the location and the velocity of the vehicles, and feeds it to the network simulator in real-time. The network simulator would then be able to model the communications between moving vehicles in a more realistic way. This enables the researchers to study and design the network protocols, systems, and applications in VANETs in a setting closer to the reality – with realistic traffic flow information. In this research, we implement the integration of Simulations of Urban Mobility (SUMO) (as the traffic mobility simulator) and OPNET Modeler (as the network simulator) to realize this framework.
In the second part of this thesis, we utilize the developed framework to investigate the feasibility of the networked camera application. In this application, cars with cameras can utilize the IVC to send the captured video to neighboring vehicles, whose drivers can then observe the video and react accordingly. This is especially useful when the view of the driver is blocked; the functionality is similar to the mirror installed at the side of the road, but could serve the purpose at almost any location. We simulate this application in 3 different scenarios with the developed framework: intersections with traffic signals, intersections without traffic signals in the urban area, and a highway scenario, and adjusted various parameters, such as vehicle density, link data rate, and video resolution, to compare the system performance in different settings. Performance metrics such as packet delivery ratio and end-to-end delay are measured and compared. The results show that the quality of service of the tested application is strongly affected by the vehicle density, which is determined by the neighboring road structure and the traffic light status. We also found that in most applicable scenarios, it is required to use a link data rate as high as 36 Mbps so that the video quality is acceptable for the driver.
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