Offline Emergency Communication Network Using ESP32 and LoRa Technology

Abstract

Communication systems that depend on cellular networks or Internet connectivity may become unreliable or unavailable during disasters and emergency situations. This paper presents an offline emergency communication system that uses ESP32-based nodes and 433 MHz LoRa communication to transmit SOS information without requiring conventional network infrastructure. The system allows an emergency alert to be generated through either a physical SOS button or a local Wi-Fi web interface hosted by the transmitter node. The transmitter integrates a NEO-6M GPS module to obtain location information and combines it with emergency details such as the emergency type, number of people, and message before transmitting the SOS packet. The receiving node acknowledges the received packet and transfers the emergency information to a local computer through USB serial communication. The system also incorporates relay-based multi-hop forwarding to support communication beyond a direct transmitter-receiver link. On the computer side, a Python backend processes the received data, calculates emergency priority, stores the information in an SQLite database, and provides the data to a local rescue dashboard. The developed system integrates offline SOS generation, LoRa-based communication, location reporting, acknowledgement, emergency prioritisation, and local monitoring into a single communication framework for emergency scenarios where conventional connectivity is unavailable.

Introduction

During natural disasters and emergency situations, conventional communication networks such as cellular services and the Internet may become unavailable due to power failures, infrastructure damage, or network congestion. These disruptions make it difficult for affected individuals to communicate their emergency details and locations to rescue teams. Therefore, infrastructure-independent communication systems are essential for improving emergency response.

LoRa (Long Range) technology offers a promising solution because it enables long-range, low-power wireless communication without depending on cellular networks or Internet connectivity. Previous studies have explored LoRa-based emergency communication, mesh networking, multi-hop forwarding, GPS localization, and offline monitoring interfaces. However, there remains a need to integrate these features into a lightweight, end-to-end emergency communication system.

The proposed system, titled Offline Emergency Communication System Using ESP32 and 433 MHz LoRa, integrates emergency alert generation, GPS-based location tracking, wireless communication, acknowledgement, multi-hop forwarding, local data processing, and rescue-side monitoring. It consists of two primary ESP32-based nodes, TX001 and RX001, optional LoRa relay nodes, and a local computer for data processing and visualization.

The system operates as follows:

1. SOS generation: An emergency alert can be triggered using a physical SOS button or a local Wi-Fi web interface hosted by the transmitter. Users can provide details such as their name, emergency type, number of affected individuals, and a message.

2. GPS localization: A NEO-6M GPS module obtains the emergency location. When a valid GPS fix is available, latitude, longitude, and satellite information are included in the emergency packet.

3. LoRa communication: The ESP32 transmitter sends the structured SOS packet through a 433 MHz LoRa module. The system supports direct communication and multi-hop forwarding through relay nodes to extend the communication path.

4. Acknowledgement and duplicate detection: The receiving node acknowledges successfully received SOS packets. Unique packet identifiers help identify duplicate messages and prevent unnecessary repeated forwarding. RSSI and SNR measurements provide information about the received signal quality.

5. Backend processing and storage: The receiving node transfers emergency data to a local computer through USB serial communication. A Python backend processes the information, converts it into structured JSON data, assigns an emergency priority using rule-based processing, and stores the records in an SQLite database.

6. Rescue dashboard: A local HTTP interface displays emergency details, location information, affected-person counts, calculated priority, and location markers on an offline map, enabling rescue personnel to monitor alerts without Internet connectivity.

The proposed methodology combines embedded hardware, wireless communication, GPS localization, local software processing, and offline visualization into a unified workflow. Its main advantages include independence from conventional communication infrastructure, low-power communication, location-aware emergency reporting, extended communication through relay nodes, local data storage, and organized emergency prioritization.

Conclusion

This paper presented an offline emergency communication system designed to provide structured emergency information without depending on cellular networks or Internet connectivity. The developed system combines ESP32-based transmitter and receiver nodes with 433 MHz LoRa communication, GPS localization, acknowledgement handling, and relay-based multi-hop communication. The transmitter provides two methods for generating an SOS: a physical emergency button and a local Wi-Fi web interface. Emergency information is combined with available GPS coordinates and transmitted as a structured SOS packet. At the receiving side, the emergency packet is acknowledged and transferred to a local computer, where a Python backend performs data processing and emergency priority calculation. The processed information is stored in an SQLite database and presented through a local rescue dashboard. The main contribution of the developed system is the integration of the complete emergency information flow, from user-side SOS generation and wireless transmission to local processing, storage, and rescue-side visualization. This makes the system suitable as an infrastructure-independent communication framework for situations in which conventional communication networks are unavailable or unreliable.

References

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Copyright

Copyright © 2026 Ayush Kalambe, Kshitij Dushing, Rutuja Bhusari, Shreya Mahetkar, Vedant Bavaria, Prajkta Wankhede, Ruchi Kadwane. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.