Research On MAC Layer Protocol Of Vehicle Ad Hoc Network Based On TDMA

Vehicular Ad hoc Network(VANET),as a special application of mobile ad hoc networks in intelligent transportation systems,has played a significant role in improving the driving experience of passengers and solving traffic problems,thus receiving increasing attention.As one of the key technologies of VANET,Media Access Control(MAC)plays an important role in efficient and fair channel resource sharing and reliable data transmission among nodes.Due to the characteristics of high node mobility,frequent topology changes,and frequent slot conflicts in VANET,people face enormous challenges when designing MAC protocols suitable for VANET.Based on time division multiple access(TDMA)technology,this paper mainly studies the conflict of frequent transmissions in VANET’s traditional MAC protocol.The main work is as follows:1.Addressing the issue of overlapping conflicts caused by merging conflicts and access conflicts in distributed MAC protocols.A TDMA MAC protocol based on mobility prediction,DTMP-MAC(Distributed MAC Protocol with Time Slot Reservation Based on Mobility Prediction),is proposed.This protocol divides time slots into different time slots for vehicles that need to be reassigned after merging conflicts and vehicles that need to be accessed by new access networks.During driving,vehicles use mobility prediction algorithms and time slot reservation mechanisms to reassign time slots for these vehicles that may encounter future conflicts,thereby reducing the probability of overlapping conflict problems.The results of simulation experiments show that compared with PTMAC protocol and Ve MAC protocol,the DTMP-MAC protocol proposed in this paper has a certain degree of improvement in reducing the probability of stacking conflicts,reducing average end-to-end delay,and improving packet reception rate.2.A TDMA MAC protocol,CTDI-MAC(Cluster MAC Protocol for Time Slot Management Based on Dynamic Information),is proposed to address the frequent merging conflicts between different clusters in cluster based MAC protocols.In the cluster head election stage,the CTDI-MAC protocol takes into account four dynamic parameters: average link lifetime,node degree,speed correlation,and average distance as factors,and uses Analytic Hierarchy Process to calculate the weighted sum of the comprehensive metrics generated by the cluster head.The node with the highest comprehensive metric value is selected as the cluster head,which improves the stability of the cluster and the management efficiency of the cluster head.In the generation stage of the cluster,appropriate time slots are allocated based on the relative position of vehicles.In the time slot management stage,vehicle dynamic information is used to manage the time slots of cluster members,in order to reduce the probability of adjacent vehicles occupying the same time slot between different clusters,thereby reducing the probability of merging conflicts between clusters.The results of simulation experiments show that compared with existing protocols,the CTDI-MAC protocol proposed in this paper has a certain degree of improvement in reducing the average number of cluster head changes,reducing merge conflict rates,reducing average end-to-end latency,and improving packet reception rate.3.Finally,by comparing the simulation results of CTDI-MAC protocol and DTMP-MAC protocol in the same scenario,it was found that CTDI-MAC protocol is more suitable for scenarios with relatively high density and relatively large communication range,while DTMPMAC protocol is more suitable for scenarios with relatively low density and relatively small communication range.