Disaster Roaming

Description

Disaster Roaming is a specialized roaming service defined in 3GPP specifications that activates when a Disaster Condition occurs, such as a natural disaster or major network outage. Unlike normal roaming, which is governed by commercial agreements and subscription policies, Disaster Roaming allows subscribers to access services through any available network in the affected area, even if no roaming agreement exists between the home and visited networks. This ensures that users can make emergency calls, receive alerts, and maintain basic connectivity when their home network is damaged or overloaded.

The service is built upon existing roaming architectures but introduces specific policies and procedures to handle the exceptional circumstances. In 5G, the Policy Control Function (PCF) in the visited network can apply special Disaster Roaming policies, while the Unified Data Management (UDM) in the home network may provide limited subscription data to the visited network. The Access and Mobility Management Function (AMF) and Session Management Function (SMF) enforce these policies, ensuring that only essential services are granted. For EPS, similar mechanisms are defined in 23.401, with the Mobility Management Entity (MME) and Policy and Charging Rules Function (PCRF) playing key roles.

Key components include the Disaster Condition detection, which can be triggered by the home network or by regulatory authorities. Once declared, the visited network broadcasts an indication that Disaster Roaming is active. Subscribers' devices then attempt to register with any available network, and the visited network authenticates them using the home network's credentials if reachable, or via alternative means if the home network is isolated. The service may be limited to voice, SMS, and emergency services, depending on operator policies and resource availability.

Disaster Roaming also involves coordination between operators and regulators. The GSM Association (GSMA) has published guidelines for its implementation, and 3GPP specifications 22.261 and 22.831 outline the service requirements. The architecture ensures that charging and billing are handled appropriately, often with special tariffs or waived fees during the disaster period. Security is maintained through existing authentication and encryption mechanisms, though some relaxations may apply to facilitate access.

In summary, Disaster Roaming is a critical enabler for public safety and emergency communications. It leverages 3GPP's flexible roaming framework to provide connectivity when it is most needed, demonstrating the standards' adaptability to exceptional scenarios.

Purpose & Motivation

Disaster Roaming was created to address the critical need for communication during disasters when home networks are incapacitated. Traditional roaming relies on pre-existing agreements and normal subscription policies, which fail in emergencies because users cannot access any network if their home operator's infrastructure is destroyed or if no roaming agreement exists with the available network. This can leave victims and first responders without vital communication links.

The service solves this by allowing any available network to serve subscribers from affected operators, regardless of commercial arrangements. It ensures that emergency calls, disaster alerts, and basic connectivity remain available. The motivation stems from real-world events like earthquakes, hurricanes, and tsunamis, where network damage isolated communities. Regulatory bodies and standards organizations recognized the need for a standardized approach to enable rapid cross-network access.

Introduced in Release 17, Disaster Roaming builds on existing roaming and policy control mechanisms, adding minimal complexity to support the exceptional case. It represents a significant step in making mobile networks more resilient and socially responsible, aligning with global efforts to improve disaster response and recovery.