| Travel safety and traffic efficiency,are the most important two motivations for the rapid development of the Internet of Vehicles and vehicular ad hoc network(VANET)technology.However,a lot of charac-teristics of vehicle network bring new challenges to the design of vehicle network communication protocols.How to design the communication protocol and communication system with high throughput and low latency according to the characteristics of the on-board network environment has always been the focus of vehicle network communication research.The design and standardization of the multi-channel protocol standard for the physical layer and MAC layer is especially significant.To solve the problem related to channel utilization and multi-channel information delay,we propose the multi-channel protocol:spectrum penetration based MAC(SPBM)protocol.We have conducted an in-depth study on SPBM protocol.The following three aspects of contributions are made by this thesis.(1)Based on the existing MAC protocols and the multi-channel cooperation mechanism in WAVE proto-col stack,the spectrum penetration mechanism of the Type ? messages is designed to perform the cross-channel information transmission,so as to obtain high channel utilization while ensuring that safety-related messages can be transmitted timely.By using the channel allocation algorithm of Type ? messages and Type ? mes-sages,the problem of media loss can be solved and different types of messages can be transmitted efficiently in different channels and at different synchronization intervals.Considering the different characteristics of three types of messages,we also design the overall operation of our SPBM protocol.(2)Based on the characteristics of SPBM protocol,the Markov hybrid queuing model is proposed.The normalized service intensity of Type ? and Type ? messages is considered as the key parameter,and the utilization and allocation distributions of different types of messages in steady state are given.Significant parameters like the collision probability of Type ? messages,the queuing delay of the third kind of messages are analyzed as well.The comparison results show that our analytical and simulation results are in good agreement.(3)Through the simulation and experiment,we verify the feasibility and validity of our SPBM proto-col mechanism and its algorithms.Evaluation results prove that our protocol improves the throughput of non-secure messages and the reliability of safety message transmission compared with other protocols.The proposed SPBM protocol has a high channel utilization rate,and has strong adaptability to different traf-fic density scenarios.In the experiment,we use USRP 2920 and PXI software defined radio platform with the Lab VIEW development environment to implement a lot of key technologies including orthogonal fre-quency division multiplexing(OFDM)communication,channel estimation/frequency-domain equalization and spectrum sensing.We finally built up the V2V/V2I vehicular communication system based on OFDM technology,and the validity of the SPBM protocol mechanism is verified.In summary,SPBM protocol is designed to satisfy the different transmission demands of different types of messages in VANET multi-channel MAC protocols.Besides the theoretical model,the simulation and experimental verification are carried out.Our research provides a reference for the design and improvement of the vehicle networking technology,especially the communication mechanism and the related communication standard,and the contributions of this thesis are helpful to promote the technology development and practical application of vehicular network. |
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