Byzantine Fault Tolerance (BFT) protocols can be divided into synchronous BFT protocols, partially synchronous BFT protocols, and asynchronous BFT protocols according to communication delay. Asynchronous BFT protocols are widely used because they can tolerate uncertain communication delays in the real world. However, asynchronous BFT protocols need to perform many rounds of broadcasts to reach agreement on a transaction subset, which consumes a lot of communication, computing, and storage resources. In this paper, we present Volia, an asynchronous BFT protocol which resolves above problem.We design new broadcast protocol to reduce the number of broadcast rounds needed for agreement. It reduces the communication overhead. Voting broadcast is used to maintain the order of transaction subsets rather than threshold signature to reduce computation cost. Above mechanisms speeds up the agreement phase, reduces the accumulated transaction subsets waiting for agreement and thus saves storage resources. We conduct experiment on Volia and the results show that Volia exhibits about 2~65× throughput, 2~25% latency, and 30% storage cost compared to other asynchronous BFT protocols.

Wireless Sensor Actuator Networks (WSANs) have shown its advantages of flexibility and cable-free deployment in industrial applications. However, the sensors explore directly to the harsh environment and are the most prone to faults and malfunctioning, which poses a big challenge to the WSAN's applicability in applications with high safety requirements. This paper focuses on highly reliable WSANs equipped with double-sensing system and proposes a model-based on-line sensor fault detection scheme by exploiting information redundancy between sensors and actuators. An optimization method is developed to make the proposed scheme robust to the largely fluctuating end-to-end packet transmission delays due to wireless communications. The performance of the proposed sensor fault detection scheme is demonstrated by the simulation of a pick and place robot.