Research On The Key Technologies Of MAC Protocol For VANETs’ Broadcast

Vehicular Ad-hoc Networks(VANETs),as a particular form of Mobile Ad-hoc Network(MANETs)in which trajectory is restricted by the road and the performance of vehicle is not considered,will play the extremely vital role in next generat ion Intelligent Transport System(ITS)architecture.Among various services provided by VANETs,it’s a milestone to reach the guaranteed delivery of urgent safety messages.Utilizing the specific fast accurate timely safety information provided by VANETs communication technology,the car drivers can quickly understand the road conditions,vehicular information,etc.And they can make early response to take measures to reduce the occurrence of traffic accidents.Therefore,the design of an efficient,stable and fast access protocol for VANETs is not only beneficial to the implementat ions of routing broadcasting protocol,but also has extremely important future value and practical significance.In this thesis,we concentrated on the design of access protocol for VANETs,proposing a demand-adaptive MAC protocol without information packet collision for safety services and describing the design of dynamic switching between the MAC protocols and existing protocols in different application scenarios.Under the restrictions of VANETs’ and application scenarios’ features,the protocol takes the advantages of design ideas and design principles from some well-performance access protocols.By shrinking or expanding the slots assignment in application and information stages through roadside communication units ’ dynamic management and allocation,the DAM protocol can adaptively realize the exclusive time slots assignment for vehicular nodes to meet their network requirements.By utilizing the principal-subordinate model and the architectural mechanisms of TDMA,the DAM protocol can avoid collis ion of packets containing the safety information.The main contents of this paper are as follows:1.Analyze the existing VANETs’ protocols and understand in-depth of complex network theory and simulat ion theory.From the point of the classification criteria of access protocols,we figure out the principles,peculiar ities,advantages and disadvantages of some well-performance access protocols to establish the basic foundation of the research for VANETs.2.Abstract different application scenarios based on the actual traffic environments and propose the design of dynamic switching mechanism based on application scenario.The dynamic switching mechanism can display the advantages of different access protocols and avoid their shortcomings.3.Propose a demand-adaptive access protocol without information packet collision for safety services on the basis of the improvement and design the defects of some existing protocols and according to the performance measurement standard.The access protocol can effectively reduce the delay and the collision rate.4.Design the experimental models of the protocol,complete the simulation exper iment,collect the simulat ion results and perform the performance analysis.In this paper,we use OPNET Modeler simulat ion platform to simulate the protocol in three layers of internal system.And collect the results to compare with other access protocols in the same environment.