Research On Multi-Priority Time Division-CSMA Protocol Based On FPGA In VANET

Vehicular Ad Hoc network(VANET)is one of the key construction projects of industrial Internet of things,which aims to improve the construction level and vehicle service quality of intelligent transportation system.At present,the research of VANET has achieved phased results under the collaborative efforts of government departments and scientific research institutions.However,the problems of low transmission reliability and high delay of media access control(MAC)layer protocol still hinder the development of VANET technology,especially the fast growth of vehicle and traffic information,which brings great challenges to MAC layer access control protocol.In order to achieve the high-speed development of Internet of vehicles technology,it is necessary to improve the transmission performance of MAC layer access control protocol and realize the reliable transmission of data.Therefore,this paper optimizes and merges the MAC layer access control protocol of the VANET from the aspects of enhancing the network transmission reliability,reducing the transmission delay and increasing the channel utilization.The following work was carried out:Firstly,the slot allocation strategy,channel detection and transmission mechanism of the traditional random multiple access control protocol are optimized,and get the optimized carrier sense multiple access(CSMA)protocol model.The correctness of the protocol model is verified by computer simulation.At the same time,the throughput of the optimized protocol model is higher than that traditional protocol,the throughput of the optimized three slot and three-dimensional probability detection CSMA is higher and the transmission delay is lower.Then,aiming at the problem of low transmission reliability of CSMA protocol when there are many information packets arriving and high system overhead of time division multiple access(TDMA).TDMA and three slot and three-dimensional probability detection CSMA are integrated to get time division-carrier sense multiple access(TD-CSMA),which gives full play to the advantages of high transmission reliability of TDMA.The simulation results show that TD-CSMA protocol model enhances the reliability of network transmission,reduces the transmission delay,and further improves the service quality of the vehicular Ad Hoc network.Thirdly,the multi-priority differentiated service mechanism is added to the protocol model of the vehicular Ad Hoc network to increase the channel utilization.By optimizing the protocols three slot and three-dimensional probability detection CSMA and TDCSMA,the multi-priority optimized CSMA and multi-priority TD-CSMA(MPTDCSMA)are proposed.The throughput of the multi-priority protocol model is simulated.The higher the priority of the sending site is,the more channel capacity is occupied and the greater the throughput of the system.Finally,according to the theoretical model and hardware implementation flow of MAC layer access control protocol,the hardware circuit system of protocol model is implemented based on field programmable gate array(FPGA).The test results of the throughput of the hardware circuit system of the access control protocol model are compared with the theoretical values,the test values are consistent with the theoretical values,which proves that the access control protocol model based on FPGA is correct and reasonable.