TDMA-based Tolerant Collision MAC Algorithm On VANET

In recent years,the continuous innovation of Internet technology has brought unprecedented opportunities and challenges.As the trend of the times,it has changed all aspects of life.As one of the most important parts of transportation,vehicles has always provided its convenience for people.In order to meet people's needs for adapting to the times,intelligent transportation comes into being and VANET is at the forefront of this wave.VANET is the abbreviation of Vehicular ad-hoc network.It is a self-organizing mobile network formed by mobile vehicle and wireless communication technology.As an important part of VANET wireless communication,MAC algorithm has never been absent from researchers' studies and occupies an important position.After author carried out studies on VANET,a cluster strategy based on historical route theory,namely,Cluster Strategy for Collision Tolerance(CSCT)was proposed.This theory divides clusters by comparing similarity degree between different vehicles.It provides a stable communication environment for inter-vehicle communication.Cluster Head Factor(CHF)algorithm which is used for electing cluster head nodes is proposed.This algorithm takes the correlation properties of vehicles within a cluster into consideration,such as relative speed and relative distance between nodes and the number of coincident nodes in the route etc.It can quickly select the vehicle node with the optimal CHF weight as the cluster head node which can effectively improves the “crash” status caused by long selection time;it sets similarity(RS,Route similar)as priority.When collisions occur between clusters,vehicles with high priority are allowed to join the cluster and obtain “time slots” in time,this will effectively increases the speed of vehicles joining the cluster.Route Prediction Mechanism(RPM)is proposed.This mechanism filters out the best “driving route” by analyzing multiple routes used by vehicles which effectively improves the efficiency of the use of a cluster strategy for collision-tolerance;it takes comprehensive consideration of route relevant properties,like vehicle usage time and usage frequency on the route,it proposed Route Prediction Parameters(RPP)which improves the convergence rate of route selection and solves the computing load caused by excessive routes.Tolerant Collision Time Slots(CTTS)is proposed to be used for vehicle slot assignment and slot competition.When the transmission time slots are not free,collision-tolerant time-slots will participate in the allocation of time-slots,effectively increasing the speed of vehicles acquiring time slots.TDMA-based tolerant collision MAC algorithm on VANET(TTC-MAC)based on time division multiplexing in VANET is proposed.Based on IEEE 802.11 p,this algorithm uses time division multiplexing strategy to divide the synchronization period into transmission time slots,control time slots and tolerant collision slots.At the same time,it will dynamically adjust concrete time slots quantities according to the vehicle node amount within the tolerant cluster and effectively improve the utility rate of communication channel.In this paper,the communication environment is built by using traffic simulation software SUMO and network simulation software NS-3.And simulation experiments are carried out for vehicles in 802.11 p,tolerant collision cluster strategy and TTC-MAC algorithm environment.In the experiment,TTC-MAC algorithm allocates the number of transmission time slots,control time slots and collision-tolerant time slots by a ratio of 5:4:1 for a synchronization period of 100 ms,and dynamically adjusts the specific time slots according to the number of vehicle nodes in the cluster.Experimental results show that with the increasing number of vehicles,compared with 802.11 p,TTC-MAC algorithm has significantly improved the packet delivery rate of vehicle nodes,MAC access delay and communication efficiency of vehicle nodes.