Research On Routing Protocols In Vehicular Networks

In order to solve problems like safe driving,traffic accidents,environmental pollution and traffic congestion,most countries in the world have begun to build the Intelligent Transportation System(ITSs).Vehicular Ad Hoc Networks(VANETs)is a promising technology to achieve an inter-vehicle communication in ITSs.There are some problems in VANETs,such as short transmission time,low packet transmission rate,high broken rate of links and fast changes of topology due to the high rate of vehicle's movement,the uncertainty of the driver's behavior and many other unstable channel characteristics.It is a very critical task to design a stable and scalable routing protocol to adapt to the fast-moving vehicle in VANETs.The thesis has brought up some solutions by sorting out the appropriate routing protocol in VANETs and combing them with the practical issues in different scenarios.Firstly,in super highway scenario,the classic AODV routing protocol in VANETs is improved and become AODV-L.It takes vehicle moving model and random channel model as references to redefine the vehicle communication range and routing stability index.Simulation results show that in super highway scenario,AODV-L routing protocol is more reliable with low packet loss rate and time delay.Secondly,in urban scenario with high vehicle density,the shortage of channel resources is prominent.Based on AODV-L,AODV-C is brought up with the introduction of wireless communication technology.The spectrum sensing and channel access allows the vehicle access the wireless network channel in the case that the primary user is inactive.Simulation results show that in urban scenario with high vehicle density,AODV-C has higher data transmission rate and less time delay.The main contributions and innovations of this thesis lie in the consideration of random channel model to redefine the vehicle communication range,the combination with the model of the vehicle moving in highway scenario to redesign the routing metric that measures the routing stability and the improvement of routing protocol's performance in high-speed environment.The cognitive radio networking technology is introduced into the VANETs.The technology of spectrum sensing and channel access allows the vehicle access the wireless network channel in the case that the primary user is inactive.This is an efficient way to adapt to the urban environment where spectrum resource is scarce and channel is busy.