ImOK: A Civilian Emergency Messaging Platform

Abstract

During disasters, communication systems can fail when individuals most urgently need to reassure others of their safety. While amateur radio is an alternative, it generally requires technical expertise and is not easily accessible to the broader public. This thesis introduces a low-cost, low-bandwidth messaging system that integrates a user-friendly captive portal with radio-based communication. The platform, called ImOK, enables users to connect to a local Wi-Fi hotspot and submit short messages through a captive portal without requiring internet access. Messages are stored and processed on a Raspberry Pi–based backend, encoded, and transmitted over amateur radio to a receiving station. On the receiving side, packets are decoded, reassembled, and delivered via an email gateway. This architecture forms an end-to-end communication pipeline that integrates local wireless access, radio transmission, and internet-based delivery. Experimental results demonstrate that the system can reliably transmit and reconstruct messages under controlled conditions, supporting asynchronous communication in environments with intermittent connectivity. By leveraging low-cost hardware and widely available technologies, this work demonstrates a practical approach to enabling communication during disasters. The system highlights the feasibility of combining traditional radio techniques with modern software architectures to support emergency messaging when conventional communication infrastructure is unavailable.