VANET Simulation Model Optimization And Congestion Control

Traffic safety and efficiency is one of the most serious problem faced by urbanization. It is hard to estimate the direct and indirect loss caused by traffic problem. Vehicular Ad Hoc Network (VANET) is a special Mobile Ad Hoc Network (MANET). As a key technology of Intelligent Transportation System (ITS), VANET can effectively improve traffic efficiency, ease traffic congestion and ensure the safety of vehicle.Single hop broadcast information is the most important basic information to ensure the safety of vehicle. However, the channel resource of VANET is limited, while the broadcast date size increase sharply with the increasing number of vehicles, VANET would be paralyzed without congestion control. The main work of this paper is adaptive congestion control of VANET. The research content involves improvement of physical layer modeling and congestion control based on joint power-rate adaptation.Firstly, on the basis of introducing the characteristics and existing work of VANET and IEEE802.11p standard, we propose a method based on Exponential Effective SINR Mapping (EESM) to model VANET physical layer and accomplish a dedicated VANET channel model. The new modeling overcomes the tradeoff problem between simulation complexity and simulation accuracy faced by VANET physical layer model. The simulation results show that the new VANET model can precisely reproduce the physical layer Packet Error Rate (PER) with a low simulation complexity.Based on the proposed model, we analysis existence of optimal data rate for VANET:Optimal data rate is just a special case. There is not an optimal data rate for all distance and pathloss model in general VANET. Then, we present a joint power-rate adaptive congestion control algorithm. The algorithm is able to find out the best combination of data rate and transmit power to optimize the PER performance with a channel busy time limitation. The simulation result shows that proposed adaptive algorithm can effectively improve the PER performance and increase effective transmission range.