When disaster strikes, communication often fails. Cell towers can go offline, internet connections can disappear, and people are left without a way to share information or ask for help. A new research project looks at how to keep people talking even when regular networks are gone.
Researchers from the University of Zürich and the University of St. Gallen have developed a system that combines low-power radios with a smartphone app. It is designed for situations where traditional infrastructure is damaged or taken down, such as during natural disasters or large cyberattacks.
LoRa and smartphones working together
The project uses LoRa, a long-range, low-power radio technology, to create a mobile ad hoc network, or MANET. These radios connect directly to each other without relying on cell towers or Wi-Fi. The researchers built a smartphone app that links to the radios through Bluetooth, allowing civilians to send messages and share location data using familiar tools on their phones.
The team focused on both the physical network and the user experience. Many past systems required technical skills or special equipment, which limited their usefulness in a crisis. This new approach is designed so that volunteers and community members can set it up quickly and communicate without needing radio expertise.
Component-view: mobile app and radio. Message object (bottom left) and mesh network including user roles (bottom right)
Field testing in Zürich
The researchers tested the system in an urban area of Zürich using ten devices. They compared two frequencies, 868 MHz and 433 MHz, and two types of LoRa channel settings. The best results came from the 868 MHz LongFast setting, which delivered a range of about 1.2 kilometers with a 92 percent packet delivery rate. This means messages were delivered reliably across a dense city environment.
The tests also measured battery use and signal strength. Devices stayed powered for several hours using small portable batteries. The study did not yet test 24-hour operation, which would be needed in a real emergency.
Tackling misinformation and abuse
One of the challenges in crisis communication is trust. During disasters, rumors and false information can spread quickly. To address this, the researchers added an identity system based on public key infrastructure. Users can verify their identity by scanning a government ID, which creates a digital certificate. Messages are signed with this certificate so others can confirm who sent them.
The system includes roles such as community moderators and administrators. Moderators can flag or hide harmful content within a local area. People without verified identities can still receive messages but cannot send them. This design aims to reduce the risk of bad actors spreading harmful information.
Limitations and next steps
The project is still in its early stages. The tests involved only ten nodes and one urban setting, so performance with larger networks and different locations remains untested. The app currently works only on iOS, and the identity verification step assumes that government ID systems are online, which may not always be the case after a disaster.
The researchers plan to expand testing to include 50 or more devices and to try the system in both rural and urban environments. They also want to explore ways to integrate with existing emergency services so that civilian networks can coordinate with official responders.
