Cell Broadcast

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Public warning alerts using embedded Cell Broadcast feature on Android 7.1

Cell Broadcast/Cell Information (CB) messaging is a mobile technology feature defined by the ETSI’s GSM committee and is part of the 2G, 3G, 4G LTE (telecommunication) and 5G standards. It is also known as Short Message Service-Cell Broadcast (SMS-CB).

Cell Broadcast is designed for simultaneous delivery to multiple users in a specified area. Whereas the Short Message Service-Point to Point (SMS-PP) is a one-to-one and one-to-a-few service (requires multiple SMS messages, as each message can only carry one phone number), Cell Broadcast is a one-to-many geographically focused messaging service.

Cell Broadcast messaging was technologically demonstrated in Paris for the first time in 1997. Some mobile operators use Cell Broadcast for communicating the area code of the antenna cell to the mobile user (via channel 050), for nationwide or citywide alerting, weather reports, mass messaging, location-based news, etc. Not all operators have the Cell Broadcast messaging function activated in their network yet, however the large majority of the handsets nowadays have the capability to support cell broadcast by default.

Cell Broadcast is a technology that allows a text or binary message to be defined and distributed to all mobile terminals connected to a set of cells.

Thus, one Cell Broadcast message can reach a large number of terminals[a] at once. In other words, Cell Broadcast messages are directed to radio cells, rather than to a specific terminal. The latest generation of Cell Broadcast Systems (CBS) are capable to send a Cell Broadcast (alert) message up to 500,000 cells in less than 10 seconds, reaching millions of Mobile subscribers in a matter of seconds. A Cell Broadcast message is an unconfirmed push service, meaning that the originators of the messages do not know who has received the message, allowing for services based on anonymity. Cell Broadcast technology is compliant with the latest EU General Data Protection Regulation (GDPR) as mobile phone numbers are not required by CB. The originator (alerting authority) of the Cell Broadcast message can request the success rate of a message. In such a case the Cell Broadcast System will respond with the number of addressed cells and the number of cells that have broadcast the Cell broadcast (alert) message.

Cell Broadcast is not affected by traffic load; therefore, it is especially usable during a disaster when load spikes of Data (Social media and Mobile app), regular SMS and Voice calls usage (mass call events) tend to significantly slowdown mobile networks, as multiple events showed e.g. 2016 Brussels bombings, Paris attacks, 2017 London attacks, Manchester Arena bombing, Boston Marathon bombing, 7 July 2005 London bombings, 2004 Madrid train bombings, 2004 Indian Ocean earthquake and tsunami.

Cell broadcast has been widely deployed since 2008. The major Asian, US, Canadian, South American operators have deployed the technology in their networks. In Europe the first countries have adapted the technology at this moment in time.

Cell Broadcast is a mobile technology that allows messages (up to 1395 characters) to be broadcast to all mobile handsets and similar devices within a designated geographical area (polygon). The broadcast range can be varied, from a single cell to the entire network.

Wireless Emergency Alerts and Government alerts using Cell broadcast technology are natively supported in every Apple handset running IOS 6 and higher and every Android handset running Android Kitkat 4.4 and higher. Mobile Smart Phones have a standard configuration menu to enable/disable the receiving of Cell Broadcast messages.

Technology[edit]

A Cell Broadcast message page is composed of 82 octets, which, using the default character set, can encode 93 characters. Up to 15 of these pages may be concatenated to form a Cell Broadcast message (maximum length of one Cell broadcast message is therefore 1395 characters). Each page of such a CB message will have the same message identifier (indicating the source of the message), and the same serial number. Using this information, the mobile telephone is able to identify and ignore broadcasts of already received messages.

A Cell Broadcast Centre (CBC), a system which is the source of SMS-CB, is connected to a base station controller (BSC) in GSM networks, to a radio network controller (RNC) in UMTS networks, to a Mobility Management Entity (MME) in LTE (telecommunication) networks or to a core Access and Mobility management Function (AMF) in 5G networks.

  • The 2G-CBC (BSC) interface is described in 3GPP standard TS 48.049; however, non-standard implementations exist.
  • The 3G-CBC (RNC) interface is described in 3GPP standard TS 25.419.
  • The 4G-CBC and 5G-CBC (MME & AMF) interfaces are described in 3GPP standard TS 23.041.

A CBC sends SMS-CB messages, a list of cells where messages are to be broadcast, and the requested repetition rate and number of times they shall be broadcast to the BSC/RNC/MME/AMF. The BSC's/RNC's/MME/AMF responsibility is to deliver the SMS-CB messages to the base station (BTSs), NodeBs, eNodeBs and gNodeBs which handle the requested cells.

In GSM SMS-CB messages are broadcast over an air interface on a special signaling channel, Cell Broadcast Channel (CBCH). CBCH reuses one of signalling channels (SDCCH). There is only one CBCH in each cell in cellular network. GSM specification allows to send only one SMS-CB message page every 1.883 s in basic mode and another one in extended mode. However extended mode is optional in GSM thus neither networks nor mobile phones are required to support it, so the real throughput is only one message page each 1.883 s in basic mode.

Broadcast messages are used in most countries to send emergency alerts, using as input a CAP (Common Alerting Protocol) message or Wireless Emergency Alerts C-interface protocol, which has been specified jointly by the Alliance for Telecommunications Industry Solutions and the Telecommunications Industry Association.

Cell Broadcast adoptation rate[edit]

A point of criticism in the past on Cell Broadcast was that there was no uniform user experience on all mobile devices in a country.

This limitation is since 2012 no longer present. In case a national civil defence organisation is adopting one of the Wireless Emergency Alerts standards, WEA - formerly known as CMAS in North America, EU-Alert in Europe, LAT-Alert in South America, Earthquake Tsunami Warning System in Japan, each subscriber in that country either making use of the home network or is roaming automatically makes use of the embedded Public warning Cell Broadcast feature present in every Android (operating system) and IOS mobile device.

In countries that have selected Cell Broadcast as the technology to submit public warning messages up to 70-80% of the population older than 12 year receive the public warning verification message within seconds after the government authorities have submitted the message see as an example NL-Alert.

Public warning implementations[edit]

Many countries have implemented location-based alert systems based on cell broadcast. The alert messages to the population, already broadcast by various media, are relayed over the mobile network using cell broadcast.

An example of an actual Cell Broadcast Message on an Android smartphone, indicating a Tornado Warning in the covered area in the US.

Sources[edit]

  • "5G Americas White Paper Public Warning Systems in the Americas" (PDF). www.5gamericas.org. 5G Americas. July 2018.

External links[edit]

Footnotes[edit]

  1. ^ A "terminal" in this context is a "mobile " or any device (usually a mobile telephone) which can receive voice or data via the GSM/UMTS/LTE network.