Research On Congestion Control Algorithm In Vehicle Ad Hoc Network

With the accelerated increase of the world recession,the auto industry also announced in the golden age of evolution.This makes automobiles play a progressively essential part in people’s daily movement approach.But the following secondary problems can’t be ignored.Recurrent traffic accidents and traffic jam it’s getting worse have brought massive damage to the socioeconomic and the safety of people’s lives and property.To be careful of the traffic has become a necessary issue for all state in the nature.The wireless telecommunications promote immediately affords explanation to the above troubles.The vehicular ad hoc network proceeds as the times require,which applies the origin mechanics of mobile ad hoc network to vehicles.Vehicular ad hoc network is composed based on multiple communication mode such as vehicles to vehicles and infrastructures.They mainly broadcast actual time information such as accident avoidance or auxiliary driving,and provides enjoyment,real-time navigation and other services for drivers.These behaviors make the vehicle transportation network achieve more cautiously and accurately.Although the current mobile ad hoc network technology has become mature in many aspects,the research results of mobile ad hoc network technology can’t be directly used to support vehicular ad hoc network due to the characteristics of vehicle transportation network,such as fast topology change,limited wireless channel capacity and unstable network operation.For the reason that finite channel capacity of the vehicular ad hoc network.Specifically the control channel bandwidth supporting safety applications running is only 10 MHz,when the nodes on the road become jammed,the safety messages transmit regularly will cause control channel to be overburden and congestion.Channel congestion not only involves the transmission of periodic safety messages,but also seriously interrupts the transmission of eventdrive messages.This kind of messages is often related to the lives of drivers and passengers,and is a vital emergency message.Therefore,it’s a great significance to study the channel congestion control method for vehicular network to ensure the reliable transmission of security messages and maintain the operation performance of wireless network.To solve the above dilemma,we review the key technologies about vehicular ad hoc network and analyses the challenges for channel congestion.And this paper proposes two congestion control algorithms.The specific work includes the following aspects:(1)This paper proposes an adaptive congestion control method for transmission parameters based on local density prediction.First,the local density prediction method based on vehicle driving environment parameters is introduced in detail.Then,the method of using the busy rate of the channel to judge the channel state is introduced.Subsequently,the rate and power adaptive process framework and detailed workflow based on the local density prediction value and channel busy rate are described,and specific algorithms are designed at the same time.Finally,it is documented that the algorithm in this paper can effectively raise the packet delivery rate and reduce the transmission delay by experimentation.With improving the accuracy of transmission and increasing road safety.(2)Decentralized congestion control based on message priority scheduling mechanism and beacon message generation rate adaptation is proposed.First,describe an approach that associates the static factors of message attributes and application category,and dynamic factors of the network state to determine the priority.And dynamically schedule all messages in the queue based on the priority.Then,a control method based on beacon generation rate adaptation is designed,which mainly adjusts the length of the beacon generation time interval according to the channel state information.Finally,the algorithm of this paper is certified based on NS-3.The consequence appearance that the algorithm has great performance in all conditions,and enhances the average delay and packet loss rate.