Cell broadcast is not affected by traffic load; therefore, it is very suitable during a disaster when load spikes of data (
social media and
mobile apps), regular SMS and voice calls usage (
mass call events) tend to significantly congest mobile networks, as multiple events have shown.
Public warning systems, otherwise known as emergency alert systems, implemented through cell broadcast technology vary by country, but are broadly the same. Technical standards are outlined in the 3GPP TS 23.041 standard. Large implementations mentioned in 3GPP standards are
Wireless Emergency Alerts (CMAS) in the United States and
EU-Alert in Europe (set out in
ETSI standards, but national implementation varies). Alerts can be geo-targeted, when only phones in a defined geographical area are set to receive an alert. When an alert is received, a notification is shown in a unique format and a dedicated sound is played even if the phone is set to silent: a of 853
Hz and 960 Hz
sine waves, as prescribed by both WEA (CMAS) and ETSI standards. Most phone manufacturers adhere to these standards but have slightly different user interfaces. Similar to
emergency calls, devices do not usually need a
SIM card to receive alerts. Emergency alerts in most implementations of cell broadcast have distinct alert categories or levels, using a message identifier outlined in 3GPP standards. The alert category or level is defined by the severity of the warning, e.g. threat to life, imminent danger or advisory message. Depending on national implementation, users may be able to opt-out of receiving lower level alerts. However, the highest level of alert will usually always be displayed on a user's device. Below is a comparison table on alert categories/levels across systems (based on the common 3GPP message identifiers): When
roaming, if the user's home carrier supports Cell Broadcast emergency alerts, alerts will be displayed if the category/level of alert is enabled and equivalent to their home carrier's system. Cell Broadcast messages can use a CAP (
Common Alerting Protocol) message as an input as specified by
OASIS (organization) or the
Wireless Emergency Alerts (WEA) C-interface protocol, which has been specified jointly by the
Alliance for Telecommunications Industry Solutions (ATIS) and the
Telecommunications Industry Association (TIA). Advantages of using Cell Broadcast for Public warning are: • Sending out a Cell Broadcast message to a few or millions of people takes less than 10 seconds • Cell Broadcast has a unique and dedicated ringtone and vibration • Only an authorized authority and the serving mobile network are able to send out the Cell Broadcast messages • 99% of all handsets used today support Cell Broadcast • Cell Broadcast supports a maximum message length of 1,395 characters in the Latin alphabet, and 615 characters in
Universal Coded Character Set (UCS-2) encoding in order to support other alphabets such as
Arabic,
Chinese,
Urdu, or
Greek. • Cell Broadcast supports multiple languages • Cell Broadcast supports the use of
URLs and Web-links in the alert message • Cell Broadcast supports targeting a specific geographic area (
geotargeting); only devices connected to a
base station in that area will receive the message • Cell Broadcast supports the update within seconds of existing alert messages due to changing hazard situations • Cell Broadcast supports the mechanism to inform and instruct people within seconds in the adjacent hazard areas • Cell Broadcast is able to reach all mobile subscribers including roaming subscribers (in their own language) • Cell Broadcast is not affected by mobile network congestion • Cell Broadcast is not affected by access class barring and or SIM class barring • Cell Broadcast is not affected by any data protection constraints as no personal data (subscriber identity or
MSISDN) is required and used to deliver the message. • Cell Broadcast can be used to address people present in an individual cell sector or large polygons covering a complete city or country. • Cell Broadcast messages can be updated as incident conditions change during an event at the end of an event an all-clear can be given. • Cell Broadcast is suitable for monthly or half yearly national public warning awareness tests • Cell Broadcast enablement in the mobile network has no influence on the battery life of mobile devices ==Cell Broadcast adoption rate==