Adaptive Transmission Mechanism Of VANET For Response To Users’ Information Demand

Vehicular Ad Hoc Networks (VANETs) extend digitization, networking and intel-ligence into moving vehicles and road, thus making the vehicle terminals convenient toaccesstheInternetatanytime,andtoobtainvariousinformationandservices. Thecoreof VANETs lies in that the vehicles can always select the adaptive transmission schemeaccording to their individual requirements. Therefore, how to allocate the resourcebased on the uses’ information demand is one of the most challenging and importantissues in the research of VANETs.Based on the understanding and analysis of characteristics of VANETs and dif-fculties in designing adaptive transmission scheme, this thesis studied adaptive trans-mission schemes for response to users’ information demand in diferent scenarios ofVANETs. These scenarios include:1) the drive-thru scenario where several accesspoints(APs)isinstalledalongthehighwaytoprovideInternetservicestovehicleswith-in its coverage range;2) the vehicular heterogeneous network (VHN) which consistsof a cellular network and several WLAN networks. According to distinctive featuresof each scenario, this thesis made the following contributions:1) For the drive-thru scenario, we consider single-hop vehicle-to-roadside (V2R)communications for a vehicle that aims to upload data within a hard deadline, wherethe bandwidth allocated to it is time-varying, and the size of the data is known uponit enters the area. The data bits received over a time slot are correctly received if theinstantaneous channel capacity rtis greater than or equal to a threshold Rt, and cor-rupted otherwise. The vehicle has to pay an amount for data transmission according tothe power consumption at each time slot whether the data bits are correctly receivedor not. The problem is formulated as a fnite-horizon optimization problem and solved through dynamic programming. The proof of the existence of the optimal value of thecost-to-go function is given after. Simulation results show that our proposed strategyachieves less cost than the heuristic strategy.2) For the VHN scenario, the service area is divided into multiple cells, and thevehicle within each location can request diferent applications through cellular systemorWLANsystem. Weconsidertheproblemofthecapacityshareofthecellularsystemwith multiple locations. The requests from the vehicles are classifed into multiplegroups according to their quality of service (QoS). The vehicles within each locationcanadaptthewirelessaccessbehaviorbyobservingthevariationsinpriceandcapacityofered by the cellular and WLAN systems. In this thesis, we model the evolutionand the dynamic behavior of the vehicles within a location based on the theory ofevolutionarygame. Asforthetotalproftmaximizationproblemforthecellularsystem,an iterative algorithm called GSCS which can quickly converges to the global optimalsolution has been presented to solve the non-convex problem.