#### wChain: A Fast Fault-Tolerant Blockchain Protocol for Multihop Wireless Networks

##### Minghui Xu, Chunchi Liu, Yifei Zou, Feng Zhao, Jiguo Yu, Xiuzhen Cheng

This paper presents $\mathit{wChain}$, a blockchain protocol specifically designed for multihop wireless networks that deeply integrates wireless communication properties and blockchain technologies under the realistic SINR model. We adopt a hierarchical spanner as the communication backbone to address medium contention and achieve fast data aggregation within $O(\log N\log\Gamma)$ slots where $N$ is the network size and $\Gamma$ refers to the ratio of the maximum distance to the minimum distance between any two nodes. Besides, $\mathit{wChain}$ employs data aggregation and reaggregation, and node recovery mechanisms to ensure efficiency, fault tolerance, persistence, and liveness. The worst-case runtime of $\mathit{wChain}$ is upper bounded by $O(f\log N\log\Gamma)$, where $f=\lfloor \frac{N}{2} \rfloor$ is the upper bound of the number of faulty nodes. To validate our design, we conduct both theoretical analysis and simulation studies, and the results only demonstrate the nice properties of $\mathit{wChain}$, but also point to a vast new space for the exploration of blockchain protocols in wireless networks.

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