In essence SMS doesn't work for sending messages to everyone at once; the system will become overloaded. As the paper says, some mobile phone standards have a "Cell Broadcast" facility built in for delivering messages quickly to all users, which is what is needed for emergency broadcasts. SMS is useful for delivering emergency messages to select groups of relevant personnel. That is used in Sydney and for places such as university campuses.
I discussed the issue with the staff of the tsunami watch center for the Eastern Mediterranean region, when I visited in May to give a seminar. For them warning of events like Tsunami was far less demanding than for earthquakes, where there is only 5 to 20 seconds warning.
Cellular networks have fundamentally changed the way in which our society communicates. Instead of calling a static location such as a home or office, we now call individuals and can reach them at nearly any time. Such “always on” connectivity may one day create new opportunities for the dissemination of critical information during an emergency. However, as demonstrated in this study, modern cellular networks are simply not capable of providing such a service, whether through voice calls or text messages. Through a series of experiments, we have shown that even under optimal conditions, these networks cannot meet the 10 minute alert goal set forth by the public EAS charter. Moreover, we have demonstrated that the extra text messaging traffic generated by third party EAS will cause congestion in the network and may potentially block the delivery of critical
information, such as calls between emergency responders or the public to 9-1-1 services. Accordingly, it is critical that legislators, technologists and the general public understand the current limitations of these systems.
Efforts undertaken by the CMSAAC will allow cellular networks to take an
active role during emergencies. Through the creation of new standards such as Cell Broadcast, many of the problems created by the current “point to point” architecture can be avoided. In particular, by allowing each base station to act as a virtual megaphone, cellular networks will be able to rapidly distribute up to the moment emergency messages to all phones. While nearly all major cellular providers are actively working to design, test and deploy such systems, it will taketime before this piece of our critical infrastructure can perform such tasks.
From: "Characterizing the Limitations of Third-Party EAS Over Cellular Text Messaging Services" (Patrick Traynor, School of Computer Science at the Georgia Institute of Technology, September 2008)