Bridging Technical Capability and User Accessibility: Off-grid Civilian Emergency Communication

Authors:
  • KKKarim Khamaisi
    Karim Khamaisi
  • OKOliver Kamer
    Oliver Kamer
  • BRBruno Rodrigues
    Bruno Rodrigues
  • JAJan von der Assen
    Jan von der Assen
  • BSBurkhard Stiller
    Burkhard Stiller
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Abstract
During large-scale crises disrupting cellular and Internet infrastructure, civilians lack reliable methods for communication, aid coordination, and access to trustworthy information. This paper presents a unified emergency communication system integrating a low-power, long-range network with a crisis-oriented smartphone application, enabling decentralized and off-grid civilian communication. Unlike previous solutions separating physical layer resilience from user layer usability, our design merges these aspects into a cohesive crisis-tailored framework. The system is evaluated in two dimensions: communication performance and application functionality. Field experiments in urban Z\"urich demonstrate that the 868 MHz band, using the LongFast configuration, achieves a communication range of up to 1.2 km with 92% Packet Delivery Ratio, validating network robustness under real-world infrastructure degraded conditions. In parallel, a purpose-built mobile application featuring peer-to-peer messaging, identity verification, and community moderation was evaluated through a requirements-based analysis.