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Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly

Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly. IETF #79, 7 – 12 Dec, 2010, Beijing, China. PWS Public Warning System. Contents. Cell Broadcast Service Overview Current status of PWS PWS Service requirements Cell Broadcast Service PWS Technical overview Use case Details

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Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly

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  1. Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly IETF #79, 7 – 12 Dec, 2010, Beijing, China PWS Public Warning System

  2. Contents • Cell Broadcast Service Overview • Current status of PWS • PWS Service requirements • Cell Broadcast Service • PWS Technical overview • Use case • Details • Extensibility • Message Identifiers • Regional Standards • CMAS architecture and call flow example • Summary

  3. Current status of Public Warning System • PWS comprises public alert services in 3GPP • Earthquake and Tsunami Warning System ETWS (Rel-8) • Commercial Mobile Alert System CMAS (Rel-9) • EU-Alert requirements are being studied (Rel-11) • Global service • Warning categories must be defined globally • Detection of the warning categories must be global for roaming users • Applicable in 3GPP systems over GSM, UTRAN and LTE radio • Specification references • Stage 1 in 3GPP TS 22.268 (Requirements) • Stage 2 in 3GPP TS 23.041 (CBS, Message Identifier coding) • Stage 3 in 3GPP TS 25.304, 25.331, 36.304, 36.331, 45.002, 44.018 (Radio interface)

  4. Service requirements (from 3GPP TS 22.268) • Broadcast Warning Notifications to multiple users simultaneously • Geographical notification area is specified by the Warning Notification Provider • Roaming subscribers must be supported • Concurrent broadcast of multiple Warning Notifications • with no acknowledgement required • PWS capable terminals in idle mode shall be able to receive broadcast warnings • User may opt-out from certain alert categories • Warning Notifications languages are determined by regulatory requirements • Warning Notifications are processed by PWS on a first in, first out basis, subject to regulatory requirements • Reception and presentation of Warning Notifications to the user shall not pre-empt an active voice or data session. • Current implementation requirement is up to 90 7-bit characters • Typical contents of the warning: • Event Description • Area Affected • Recommended Action • Expiration Time (with time zone) • Sending Agency

  5. Cell Broadcast Service (CBS) • CBS is defined in 3GPP TS23.041 • CBS can cover different services that are independent of each other • PWS uses CBS in GSM and UTRAN • In LTE the messages are encoded according to CBS rules, but distribution at the radio interface is LTE specific • Unacknowledged broadcast to all CBS-capable mobiles within a particular region • defined geographical areas known as cell broadcast areas • may comprise of one or more cells, up to the entire network • CBS messages may originate from a number of Cell Broadcast Entities (CBEs) through an operator’s Cell Broadcast centre (CBC) • CBS messages are sent from the CBC to the cells, in accordance with the CBS's coverage requirements • Maximum capacity ranges from GSM 93 7-bit characters to LTE 316 characters • Message segmentation is possible (15 – 64 segments) • A CBS message is identified by a message identifier and serial number • Can be used by the mobile to “screen” which messages are received • Also to identify and ignore re broadcasts of already received messages • 3GPP manages the message identifiers • CBS messages may be broadcast cyclically by the cell at a frequency and for a duration agreed between the operator and the information provider

  6. Technical overview, use case(Figure from 3GPP TS 22.268) • Key points: • Interface provided to Government authority to submit alert messages • Government authority is responsible for interface to and authentication of alert originators • Security against fake alarms, operator must authenticate alert issuer at interface C • Support for all terminals in the affected geographical area, including roaming users and terminals sourced from other countries • Distribution mechanisms at radio interface differ between GSM, UTRAN, LTE but are all based on broadcast mechanisms

  7. Technical overview, details • Radio procedures for broadcasting in 3GPP radio access technologies • Common paging or SysInfo change or CBS • Distribution area • Geographical selectivity is based on network topology • Alert codes are globally defined • Detection of alert categories is not restricted to physical distribution channel at radio interface but part of PWS service • Paging to wake up the terminal to listen to broadcast information • Mutual authentication to avoid MiM and playback attacks • Data coding scheme is critical for compatibility and mobility • Message Identifier corresponds with alert category • Message Identifiers to be received can be pre-configured on USIM or by the user • Language code • Default 7-bit coding with several language specific extensions or 16-bit UCS2 coding for other languages • Sequencing to distinguish between different messages

  8. PWS extensibility • Message identifier ranges are assigned for different broadcast use cases • MI 0 – 999 are defined by GSMA for Flash messages, weather reports, traffic reports, date & time, etc • http://gsmworld.com/documents/SE15330.pdf • MI 1000+ are defined by 3GPP for specific services, among them PWS • MI values 1100 – 18FF are reserved for PWS use • More than 2000 code points not assigned yet • ME application configures the reception of the MIs related with the service • Reception of any MI can be configured on USIM by the HPLMN operator • Legacy terminal processing of unforeseen data is normatively specified and thus predictable • alert category, character set, broken sequence, etc. • All alert categories shall be globally unique • National or regional exceptions cannot change the meaning of alert code • Japanese Tsunami alert code cannot be re-used for avalanche warning in Switzerland • CMAS Presidential Level Alert code point can be re-used for EU-Alert 1 • Additions to existing codes are possible • National extensions must be defined globally

  9. Message Identifiers (3GPP TS 34.041)

  10. Regional StandardsETWS, CMAS, EU-Alert • ETWS requirements are defined by Japanese requlator, but not normatively referenced from 3GPP specifications • 3GPP TS 22.268 captures the 3GPP system requirements for ETWS • CMAS is defined under FCC CFR 47 Part 10 Rules in the U.S. • CMAS Standards developed by ATIS and TIA: • J-STD-100, J-STD-101, ATIS-0700006, ATIS-0700007, ATIS-0700008, ATIS-0700010 • EU-Alert requirements are specified in ETSI ETS 102 900

  11. CMAS architecture E-UTRAN Public authority Network Operator UTRAN Access specific broadcast procedures GERAN 11

  12. CMAS Call Flow Example • CMSP Gateway in the operator network receives the CMAS alert from the government entity • The alert is passed to the operator’s cell broadcast centre (CBC) which identifies the cell site(s) to broadcast the alert • The alert is broadcast using 3GPP PWS

  13. Summary • PWS was designed by 3GPP as a global solution for issuing public warnings over 3GPP mobile systems • PWS is designed to allow extendable set of national and regional specific alerts while maintaining global uniqueness • PWS is a service for alerting and updating the user of emergency situations in a timely, secure, and geographically selective manner • PWS architecture • provides interface towards public authorities who generate and authorize the warnings • uses common PWS broadcast and message coding capabilities • uses radio specific cell broadcast procedures in GSM, UMTS and LTE • is extendable in future 3GPP enhancements

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