グエン キエン

The fusion of IoT and Blockchain (i.e., IoT-Blockchain) promisingly revolutionizes numerous domains. However, IoT-Blockchain systems may face scalability challenges due to a large number of IoT devices and blockchain performance. Sharding, which divides the blockchain into smaller groups, offers a solution to enhance blockchain scalability. However, most previous sharding research typically considers even node distribution in a shard (i.e., a fixed node number). Hence, it may not capture the characteristics of IoT- Blockchain systems well, where nodes are diversely distributed. This paper investigates a new scenario of shards having unevenly distributed nodes, aiming to see the impacts of the scenario on sharding protocols. More specifically, we evaluate the BrokerChain protocol on the sharding-based emulation platform (i.e., BlockEmulator) in scenarios with even and uneven node distributions. The results show that the protocol performance degrades with the uneven node distribution, suggesting the need for a dynamic sharding protocol.

Blockchain holds significant potential in addressing the security, privacy, decentralization, and interoperability challenges prevalent in the Internet of Things (IoT), However, this advancement often comes at the expense of scalability. Therefore, enhancing the scalability of IoT blockchain systems while preserving other essential blockchain attributes is imperative. This paper aims to mitigate network latency in the blockchain network, a factor directly linked to blockchain scalability. Achieving this goal requires implementing an efficient peer selection method, moving beyond the reliance on default selection (i.e., the one in Bitcoin, Ethereum, etc.). In existing literature, Perigee has been introduced as a method that nearly optimizes the delay in the transaction transmission process. However, Perigee has not comprehensively addressed the complete transaction life cycle, which includes a crucial process-block transmission. In response to this limitation, we propose Dual Perigee, a solution that thoroughly considers and optimizes both transaction-oriented latency (TOL) and block-oriented latency (BOL). To show the effectiveness of Dual Perigee, we implemented and evaluated it within an emulated IoT-Blockchain system, comparing its performance with Perigee and the default peering method in Ethereum. The results reveal that Dual Perigee excels in reducing BOL compared to Perigee. Moreover, Dual Perigee exhibited a latency that was 43% and 80% lower than the default peering method and Perigee, respectively.

This paper proposes a load-independent high-frequency wireless power transfer (WPT) system. The proposed system achieves mode switching between constant current (CC) and constant voltage (CV) output modes, which can be applied to rechargeable batteries. In the proposed system, a single switch component is added on the receiver side to change the topology of the compensation circuit. As a result, the switching between CC and CV modes is accomplished on the receiver side, which means wireless communication about the load-information feedback from the receiver to the transmitter becomes unnecessary. By achieving zero-voltage switching (ZVS) in both CC and CV modes through the load-independent operation, the proposed system achieves high power-delivery efficiency even at high frequencies. Therefore, the proposed WPT system contributes to cost reduction, system simplification, and circuit downsizing. The experimental results agreed with the analytical predictions quantitatively, which verified the effectiveness of the proposed circuits.