Warning Notification

Description

Warning Notification is a public warning service in 3GPP networks that delivers alerts to users about imminent or ongoing emergencies, such as natural disasters, terrorist threats, or public safety incidents. It is defined in specifications 22.168 and 22.968, which cover the service requirements and architecture for Warning Notification System (WNS). The service enables authorized agencies to broadcast warnings to all users in a specific area, ensuring widespread and timely dissemination of critical information.

The Warning Notification service operates over cellular networks using technologies like Cell Broadcast Service (CBS) and Earthquake and Tsunami Warning System (ETWS). It supports two types of notifications: Primary Notification, which is a short, high-priority alert that triggers immediate user alerting (e.g., a siren or vibration), and Secondary Notification, which provides additional details such as instructions, maps, or links to further information. Primary Notifications are designed for minimal latency and high reliability, while Secondary Notifications can be larger and may be delivered with less urgency.

Architecturally, the Warning Notification service involves several entities: the Warning Notification Provider (e.g., government agency), the Public Warning System (PWS) in the core network, and the radio access network. The provider sends warning requests to the PLMN operator, which then uses the PWS to broadcast the notification to UEs in the target area. The PWS includes elements like the Cell Broadcast Center (CBC) and the Mobility Management Entity (MME) or Access and Mobility Management Function (AMF) for 5G. The CBC manages the broadcast scheduling and content, while the MME/AMF handles the distribution to base stations (eNBs/gNBs).

The radio access network delivers the warning via System Information Blocks (SIBs) or dedicated messages. For ETWS, SIB10 and SIB11 carry primary and secondary notifications, respectively. For CMAS (Commercial Mobile Alert System), SIB12 is used. The UE receives these SIBs and, if configured, alerts the user. The service supports area targeting, allowing warnings to be sent only to specific cells or tracking areas, and can be activated even when the UE is in idle mode.

Key procedures include warning message initiation, broadcast, and cancellation. The provider sends a warning request to the PLMN, which authenticates and authorizes it. The CBC then formats the message and sends it to the relevant MME/AMF, which forwards it to the base stations. The base stations broadcast the message repeatedly for a configured duration to ensure reception. UEs in the area receive the warning and display it according to user settings. The service also supports testing and periodic reminders.

In summary, Warning Notification is a critical public safety service that leverages cellular networks to deliver timely alerts to citizens. Its classification into Primary and Secondary Notifications ensures that urgent information is prioritized while still allowing for detailed follow-up.

Purpose & Motivation

The Warning Notification service was created to provide a standardized, efficient, and reliable means of alerting the public to emergencies using mobile networks. Before its introduction, warning dissemination relied on traditional media like sirens, radio, and TV, which could be slow or limited in reach. With the ubiquity of mobile phones, cellular networks offer a direct and immediate channel to reach a large population.

The service addresses the need for a coordinated public warning system that can be used by government agencies to broadcast alerts to all users in a specific area, regardless of their mobile operator. It ensures that warnings are delivered even during network congestion, as Cell Broadcast is a point-to-multipoint service that does not require individual connections. The classification into Primary and Secondary Notifications allows for a tiered approach: Primary for immediate life-saving alerts, and Secondary for additional guidance.

Over releases, the service has evolved to support new requirements, such as improved message formats, support for 5G, and enhanced area targeting. The Warning Notification Provider concept clarifies the role of agencies in initiating warnings, ensuring proper authorization and authentication. The service is now a key component of many national public warning systems, mandated by regulations in various countries.