| With the continuous development of the Internet of Things(Io T)technology,the Internet of Vehicles(Io V),as a typical application of the Io T technology in the field of intelligent transportation,has attracted much attention and received extensive research attention.However,due to the characteristics of limited resources,large scale,high real-time requirements,frequent transactions,and a large proportion of micro-transactions in the Io V,the consensus algorithm used in the Io V needs to have efficient resource utilization,strong scalability,high transaction throughput,low consensus cost,and good security.Therefore,finding a consensus algorithm suitable for the Io V environment has become a hot issue.These algorithms need to be able to meet the needs of the Io V to ensure safety and reliability.This paper focuses on the requirements of the Io V system and the basic concepts of the consensus algorithm.Several common blockchain consensus algorithms are analyzed,including proof-of-work(Po W),proof-of-stake(Po S),and directed acyclic graph(DAG)-based consensus algorithms.The advantages and limitations of these algorithms in the Io V environment are discussed,and it is pointed out that the DAG algorithm is more suitable for high-concurrency and high-real-time Io V systems.In addition,this paper builds a mathematical model to deeply analyze the performance and characteristics of these consensus algorithms.The main research content and results of this paper are as follows:Firstly,this paper selects the Tangle consensus algorithm,the most representative algorithm in DAG,as an example to explore its advantages in the Io V,and establishes a Markov chain model.The Io V environment is divided into four different network load regimes: high load regime(HR),low load regime(LR),high-to-low load regime(H2LR),and low-to-high load regime(L2HR),in order to analyze the performance of the Io V system under changing network load regimes.To further analyze the performance and security of the Io V system in the H2 LR consensus process,this paper derives closed-form and approximate expressions of the state transition probabilities,as well as the closed-form and approximate expressions of the convergence probability in special cases.These studies provide useful information and guidance for the Io V system to better cope with complex network load environments,and improve the performance and security of consensus algorithms.Secondly,in order to comprehensively analyze the performance of the Io V system,this article proposes three performance metrics: expected cumulative weight,expected number of steps,and confirmation failure probability.With respect to these three metrics,this article derives their closed-form expressions based on state transition probability,and provides a detailed analysis of them.The article also explores the relationships between these performance metrics,and how to improve them by optimizing the Io V consensus algorithm.These metrics can better evaluate the performance of the Io V system and provide strong support for optimizing the Io V. |
