Research Of Periodic Safety Message Broadcasting In Vehicular Ad Hoc Network

VANET (Vehicular Ad Hoc Network) offers an effective solution for the growing traffic problem all over the world, and therefore is attracting more and more attention recently. Inter-vehicle communication can perceive the vehicle operating environment, and protect the safety of driving effectively. Safety applications are considered as basic requirements of VAENT, and various safety applications are based on the exchange of periodic safety messages. Hence, making sure of the reliable and effective periodic safety message dissemination is of great significance.Evaluations of vehicle communication applications and protocols are usually accomplished by simulation, and selecting the appropriate vehicle mobility model is very important when setting the simulation. The current mobility models’descriptions of vehicle mobility are relatively simple, and have many application limitations. Therefore, this paper first studies the vehicle mobility modeling and proposes a new inter-vehicle force based mobility model, to provide a new kind of solution and idea for the general description of vehicle mobility, and it can be extended to other more complex mobility models with different conditions. This paper analyzes the proposed mobility models and presents the realization of single-lane mobility model and two-lane (lane changing) mobility model. Based on the two mobility models mentioned above, this paper analyzes the vehicle movement state, the distribution of gap between vehicles and the lane changing situations, proving the validity of the proposed mobility model, and applies it to the simulation later.The frequent broadcasting of periodic safety messages and the variability of wireless communication environment have serious challenges to reliable dissemination of message. This paper conducts a research on the broadcasting of periodic safety message, and proposes a joint adaptive control method of generation rate and transmission power for it. After the proposed adaptive control principles of message generation rate and transmission power having been presented in detail respectively, this paper provides a method of joint control and offers relevant analysis of three indicators: distribution delay, message successful reception ratio and channel load. The paper evaluates above performance indicators of proposed method, using the two-lane mobility model proposed before to simulate straight line scenario, compared with no adaption, only using generation rate adaption and only using transmission power adaption. It is found that the performance of joint adaptive control method is the best.This paper analyzes the performance differences of joint adaptive method, early proposed PULSAR (Periodically Updated Load Sensitive Adaptive Rate control) and no adaption in straight line scenario and intersection scenario. The comparison shows that no adaption has the worst performance, and joint adaptive method has better performance than PULSAR. The simulation results show that the joint adaptive control method is feasible.