Cell broadcasting is an existing, though rarely used, function of cellular networks and is defined by the official standardisation bodies such as GSM MoU, (GSM 03.49)UMTS, 3GPP/3GPP2 and IS95CDMA.
Cell broadcasting allows text messages to be broadcast to all mobile handsets in a given geographical area. This area can range from the area covered by a single cell to the whole network. Because cell broadcast works by targeting particular cells no knowledge of mobile telephone numbers is required, unlike bulk SMS. Also cell broadcasting places a very low load on the network, a cell broadcast to every subscriber on the network is equivalent to sending an SMS message to a single phone. Network loading problems can cause severe problems in emergency situations when network usage is likely to be very high anyway and in these circumstances SMS messages can be delayed for hours or days or even lost altogether.
The cell broadcast technology provides for 64000 broadcast channels so that different types of message (severe weather, terrorist, missing child etc) could be broadcast on different channels. Not every subscriber would necessarily receive all the channels and hence all the messages. Channels can be activated from the handset or remotely by the network. Ideally certain channels would be allocated for certain message types and these would be standardised globally so that travellers would receive alerts wherever they happen to be.