Performance Analysis Of Vehicle Network Based On DSRC

With the road safety gradually attract attention of the public,the security applications of vehicular networks becoming more and more popular.However the high requirement for timeless and accuracy of safety messages makes it impossible to satisfy many protocols.However,the fashionable DSRC standard can exactly solve QoS problems of applications in vehicular networks.The goal of the thesis is to propose an accurate and efficient analysis model for DSRC,and the key point is in its data link layer.Parameters that affect network performance through the model proposed in this thesis are hoped to be obtained,thus the network performance can be improved by adjusting these parameters,and finally making it more useful to satisfy the requirements of security applications.As the DSRC protocol stack uses the EDCA mechanism for channel access control in its MAC sub-layer,and EDCA mechanism joins the multi-level queue classification ideas based on DCF mechanism.So an existing two-dimensional Markov model based on DCF mechanism was firstly introduced in this thesis,and a series of network performance analyses were carried on based on Markov.Based on the above Markov model,two Markov models were proposed based on EDCA mechanism: the two-dimensional markov model for backoff window and one-dimensional markov model for continuous slot.Based on the two Markov models,node throughput and node single hop delay were obtained in analysis by means of mathematical derivation.Node average probability of collision and contracting were firstly computed in this thesis.And then the node throughput and single hop delay were discussed in the thesis from two aspects: saturated situation as well as nonsaturated situation.In saturated situation,node throughput was calculated with its definition,namely the packet payload transmitted in unit slot time.Finally node single hop delay was calculated with the node throughput calculated before.As to nonsaturated situation,single hop delay was firstly calculated according to its feature,and then the node throughput was computed in nonsaturated situation.To verify the correctness of the above model,the system performance was got in this thesis for EDCA mechanism in the light of simulations.By contrast and parameter adjustment,the accuracy of the model proposed in the thesis can be verified.In simulation,enough times of simulations were made with the same parameters to decrease the randomness of the results as far as possible.Thus it ensured the accuracy of the simulation results.By means of theoretical model analysis and simulation experiment,the accuracy of the model is finally tested and verified.The data derived from theoretical analysis and the data collected from simulation are consistent.The theoretical performance of the proposed model is mainly influenced by the AIFS,the minimum backoff window and the maximum backoff window of the EDCA parameter set.Network performance is optimal when the network is about to enter the saturated delivery state.