The rising demand for sustainable IoT has promoted the adoption of battery-free devices intermittently powered by ambient energy for sensing. However, the intermittency poses significant challenges in sensing data collection. Despite recent efforts to enable one-to-one communication, routing data across multiple intermittently-powered battery-free devices, a crucial requirement for a sensing system, remains a formidable challenge. This paper fills this gap by introducing Swift, which enables seamless data routing in intermittently-powered battery-free sensing systems. Swift overcomes the challenges posed by device intermittency and heterogeneous energy conditions through three major innovative designs. First, Swift incorporates a reliable node synchronization protocol backed by number theory, ensuring successful synchronization regardless of energy conditions. Second, Swift adopts a low-latency message forwarding protocol, allowing continuous message forwarding without repeated synchronization. Finally, Swift features a simple yet effective mechanism for routing path construction, enabling nodes to obtain the optimal path to the sink node with minimum hops. We implement Swift and perform large-scale experiments representing diverse realworld scenarios. The results demonstrate that Swift achieves an order of magnitude reduction in end-to-end message delivery time compared with the state-of-the-art approaches for intermittentlypowered battery-free sensing systems.

翻译：可持续物联网日益增长的需求推动了采用环境能量间歇供电的无电池设备进行传感。然而，间歇性供电给传感数据收集带来了重大挑战。尽管近期研究已实现一对一通信，但在多个间歇供电无电池设备间进行数据路由——这一传感系统的关键需求——仍然面临严峻挑战。本文通过提出Swift系统填补了这一空白，该系统实现了间歇供电无电池传感系统中的无缝数据路由。Swift通过三大创新设计克服了设备间歇性与异质能量条件带来的挑战：首先，系统采用基于数论的可信节点同步协议，确保在任何能量条件下都能实现成功同步；其次，系统设计了低延迟消息转发协议，支持无需重复同步的持续消息转发；最后，系统构建了简洁高效的路由路径建立机制，使节点能以最小跳数获取到汇聚节点的最优路径。我们实现了Swift系统，并在代表多样化真实场景的大规模实验中进行了验证。结果表明，相较于间歇供电无电池传感系统的最先进方案，Swift将端到端消息传递时间降低了一个数量级。