Delivering public warning messages over 5G Broadcast, without a SIM, a subscription or a return channel.
Overview
Public warning over 5G Broadcast carries emergency alerts (earthquake and tsunami warnings, and CMAS-style civil alerts) to any receiver in coverage, using the same free-to-air LTE-based broadcast carrier as linear TV and radio. Because it needs no SIM, no subscription and no return channel, it keeps working when the cellular network is congested or unavailable, which is exactly when warnings matter most.
Three layers define it. ETSI TS 103 720, the 5G Broadcast system specification maintained by 5G-MAG, profiles PWS support over the E-UTRAN Uu downlink. 3GPP TS 23.041 defines the Cell Broadcast Service message itself: its structure, message identifiers, serial numbers and data coding. 3GPP TS 36.331 defines how that message is encoded on the radio interface, as SystemInformationBlockType12, and what a UE does on receiving it. For acronyms used here, see the Glossary.
Technology & Analysis
The implementer-facing analysis of 5G Broadcast, including the transmit and receive chain that carries these warnings.
Specifications in scope
| Specification | Title | Layer |
|---|---|---|
| ETSI TS 103 720 | 5G Broadcast System for linear TV and radio servicesMaintained by 5G-MAG. PWS support, the delivery of warning messages via SIB broadcast on the E-UTRAN Uu downlink, is defined in v1.2.1 clause 5.15.3.3. Work towards v1.3.1 (aligning with 3GPP Release 18) adds further PWS-related improvements. | System specification |
| TS 23.041 | Technical realization of Cell Broadcast Service (CBS)CBS message structure, message identifiers, serial numbers and data coding for ETWS and CMAS. Message identifier 0x1102 is the ETWS combined earthquake-and-tsunami identifier used by the reference transmitter. | Warning message realisation |
| TS 36.331 | E-UTRA; Radio Resource Control (RRC); Protocol specificationDefines SystemInformationBlockType12 and the UE actions on receiving a warning-message SIB. | Radio interface |
| TR 36.976 | Overall description of LTE-based 5G broadcast | Overview |
Receiver behaviour for public warning, and the exact CBS feature coverage, depend on the version of ETSI TS 103 720 being implemented; work towards v1.3.1 adds PWS-related improvements. Confirm the current status against the repositories and the Kanban board before relying on it.
5G-MAG tracking and contribution focus
5G-MAG maintains ETSI TS 103 720 and carries the public warning requirements into it, so feedback from implementing the alert chain in the reference tools feeds directly back into the specification. Contributions to this documentation are made through the 5G-MAG Standards repository.
Related Standards Work
- Standards: 5G Broadcast - TV, Radio and Emergency Alerts — the full 5G Broadcast specification set this builds on
- Standards: Multimedia Delivery Protocols — the FLUTE transport used for file delivery on the same carrier
- Tech: 5G Broadcast
- Reference Tools: 5G Broadcast - Emergency Alerts
Refer to the Standards repository to contribute to this documentation.