Wilderness Search and Rescue (WiSAR) represents a longstanding and critical societal challenge, demanding innovative and automatic technological solutions. In this paper, we introduce Wi2SAR, a novel autonomous drone-based wireless system for long-range, through-occlusion WiSAR operations, without relying on existing infrastructure. Our basic insight is to leverage the automatic reconnection behavior of modern Wi-Fi devices to known networks. By mimicking these networks via on-drone Wi-Fi, Wi2SAR uniquely facilitates the discovery and localization of victims through their accompanying mobile devices. Translating this simple idea into a practical system poses substantial technical challenges. Wi2SAR overcomes these challenges via three distinct innovations: (1) a rapid and energy-efficient device discovery mechanism to discover and identify the target victim, (2) a novel RSS-only, long-range direction finding approach using a 3D-printed Luneburg Lens, amplifying the directional signal strength differences and significantly extending the operational range, and (3) an adaptive drone navigation scheme that guides the drone toward the target efficiently. We implement an end-to-end prototype and evaluate Wi2SAR across various mobile devices and real-world wilderness scenarios. Experimental results demonstrate Wi2SAR's high performance, efficiency, and practicality, highlighting its potential to advance autonomous WiSAR solutions. Wi2SAR is open-sourced at https://aiot-lab.github.io/Wi2SAR to facilitate further research and real-world deployment.

翻译：荒野搜索救援（WiSAR）是一项长期且关键的社会挑战，亟需创新和自动化的技术解决方案。本文提出Wi2SAR，一种新颖的自主无人机无线系统，可在不依赖现有基础设施的情况下，实现远距离、穿透遮挡的WiSAR操作。我们的基本思路是利用现代Wi-Fi设备自动重连已知网络的行为。通过机载Wi-Fi模拟这些网络，Wi2SAR独辟蹊径地实现了通过受害者随身移动设备发现并定位他们。将这一简单想法转化为实用系统面临诸多技术挑战。Wi2SAR通过三项独特创新克服了这些挑战：（1）一种快速且节能的设备发现机制，用于发现并识别目标受害者；（2）一种使用3D打印龙勃透镜的仅基于接收信号强度（RSS）的远距离测向方法，该方法放大定向信号强度差异，显著延长工作距离；（3）一种自适应无人机导航方案，高效引导无人机飞向目标。我们实现了端到端原型系统，并在多种移动设备和真实荒野场景中评估了Wi2SAR。实验结果表明，Wi2SAR具有高性能、高效率和实用性，展示了其推动自主WiSAR解决方案发展的潜力。Wi2SAR已在https://aiot-lab.github.io/Wi2SAR开源，以促进进一步研究和实际部署。