What is ETWS and CMAS?
ETWS stand for Earthquake and Tsunami Warning System. This is a public warning system with the purpose to broadcast emergency information to all the users in a specific area in a situation like Earthquake or Tsunami. This help to broadcast emergency situation by a local or national authorities to users as quickly as possible.
There are two types of notifications the ETWS that is primary and secondary notifications. The Primary Notification contains only simple patterned type of disaster information, such as “Earthquake”, or “Tsunami”, or “Tsunami + Earthquake,” etc. When a mobile user receives a Primary Notification, it produces a pre-set alert sound and displays pre-determined text on the screen according to the message content to notify users of the danger. The Secondary Notification contains detail textual information like the epicentre, seismic intensity and other such information related to danger. ETWS primary notification is carried by SIB10 and ETWS secondary notifications carried by SIB11.
CMAS stand for Commercial Mobile Alert System. CMAS notifications carry high emerygency situations. It is carry by SIB12. There is an IE in paging message which indicate the presence of CMAS. When decode paging message came to know about CMAS notification and start to receive and decode SIB12 immediately after reading SIB1.
There are three types of alerts through CMAS:
1. Alerts issued by the President or higher authority of geographical area.
2. Alerts involving imminent threats to safety of life, issued in two different categories: extreme threats and severe threats
3. AMBER Alert or a Child Abduction Emergency
The paging message is used to inform both ETWS and CMAS notifications to UEs in RRC_IDLE and RRC_CONNECTED mode.