We rarely think about our mobile carrier in everyday life. It ensures that calls go through and messages arrive, and it tends to go unnoticed until the moment the signal disappears. In a disaster situation, that failure starts to compromise people’s ability to ask for help.
While mapping the communication technologies and responses mobilized during the 2024 floods in Rio Grande do Sul, we stayed in contact with Anatel in the state, which followed the crisis closely and helped us understand how the networks behaved throughout the disaster. It was in that conversation that we came across a mechanism rarely discussed when it comes to resilience, even though it was decisive in that context: the opening of roaming between carriers.
Under normal conditions, each phone connects only to the network of the carrier it is contracted with. If that carrier is down in a given municipality, the device loses signal even if another company still has its network running there. That is what happened in dozens of towns in Rio Grande do Sul during the peak of the flooding, with towers knocked down, stations submerged, and, in many places, only one carrier still operating. At the height of the crisis, we were told, around 170 municipalities depended on a single active network.
The opening of roaming temporarily suspended that restriction. By order of Anatel, customers of the carriers that had gone down began connecting automatically to the network that was still working, as if they were its own customers, without swapping SIM cards, changing settings, or taking any manual action. People who were isolated, and who did not understand why their phones had stopped working, were able to send a message or complete a call again. Without the measure, as reported to us, the number of towns left completely cut off, which reached somewhere between ten and fifteen at the worst point, would have been higher and would have lasted longer.
This measure helps reveal how telecommunications networks are organized. The separation between them, which makes one device lose signal while another right next to it stays connected, has no basis in any technical limitation. The infrastructure in place is capable of serving every device within an antenna’s reach, regardless of each user’s contract. What keeps the networks apart in everyday life is the business model that organizes competition between carriers. When the agency orders the opening of roaming, no new technology needs to be built or activated; what changes is a commercial rule, suspended so that the available infrastructure can serve everyone.
Broader communication, in which any device connects to any available network, is already possible with the infrastructure that exists today. It remains restricted in everyday life by a market decision, and the crisis ends up revealing that latent capacity. The point deserves attention because disaster response does not always involve introducing new solutions; part of it depends on the rules that define how the infrastructure already in place can be used.
Roaming also has its limits, which are worth acknowledging. It depends on at least one network being active and working. In towns where the power grid was destroyed, stations were submerged, and towers were swept away by the current, there was no network left to share. The opening of roaming sustained communication in the municipalities where something remained in operation, and it could do little in places where the physical infrastructure was entirely lost.
This difference between municipalities helps define what we investigate at Tridecs as communicational resilience. A resilient network depends on the existence of alternatives when one of them fails, and part of that resilience lies precisely in the rules that determine when infrastructure can be shared. Roaming activates a redundancy that already exists across the territory, distributed among different carriers, and makes it available at the moment it is most needed. Documenting this mechanism is part of the effort to understand what sustains communication when the networks we use every day stop working.