The Internet of Vehicles (IoV) is emerging as a pivotal technology for enhancing traffic management and safety. Its rapid development demands solutions for enhanced communication efficiency and reduced latency. However, traditional centralized networks struggle to meet these demands, prompting the exploration of decentralized solutions such as blockchain. Addressing blockchain's scalability challenges posed by the growing number of nodes and transactions calls for innovative solutions, among which sharding stands out as a pivotal approach to significantly enhance blockchain throughput. However, existing schemes still face challenges related to a) the impact of vehicle mobility on blockchain consensus, especially for cross-shard transaction; and b) the strict requirements of low latency consensus in a highly dynamic network. In this paper, we propose a DAG (Directed Acyclic Graph) consensus leveraging Robust Dynamic Sharding and Tree-broadcasting (DRDST) to address these challenges. Specifically, we first develop a standard for evaluating the network stability of nodes, combined with the nodes' trust values, to propose a novel robust sharding model that is solved through the design of the Genetic Sharding Algorithm (GSA). Then, we optimize the broadcast latency of the whole sharded network by improving the tree-broadcasting to minimize the maximum broadcast latency within each shard. On this basis, we also design a DAG consensus scheme based on an improved hashgraph protocol, which can efficiently handle cross-shard transactions. Finally, the simulation proves the proposed scheme is superior to the comparison schemes in latency, throughput, consensus success rate, and node traffic load.

翻译：车联网（IoV）正成为提升交通管理与安全的关键技术。其快速发展对通信效率提升和时延降低提出了迫切需求。然而，传统的中心化网络难以满足这些需求，这促使了对区块链等去中心化解决方案的探索。针对节点与交易数量增长带来的区块链可扩展性挑战，需要创新的解决方案，其中分片技术作为显著提升区块链吞吐量的关键方法脱颖而出。然而，现有方案仍面临以下挑战：a) 车辆移动性对区块链共识的影响，尤其是跨分片交易；b) 高动态网络中低时延共识的严格要求。本文提出一种结合鲁棒动态分片与树广播的DAG（有向无环图）共识机制（DRDST）以应对这些挑战。具体而言，我们首先建立节点网络稳定性评估标准，结合节点信任值，提出一种新颖的鲁棒分片模型，并通过设计遗传分片算法（GSA）求解该模型。随后，通过改进树广播机制以最小化各分片内的最大广播时延，从而优化整个分片网络的广播延迟。在此基础上，我们还设计了一种基于改进哈希图协议的DAG共识方案，能够高效处理跨分片交易。最终，仿真实验证明所提方案在时延、吞吐量、共识成功率和节点流量负载方面均优于对比方案。