For all the effort service providers put into 911 emergency calling service and systems, the simple fact is that both wired and wireline 911 systems will crash if there is a big enough event. The 911 system can even stay up, but might not be usable, simply because callers can't get access to the network. Everybody knows that, and the recent San Jose, Calif. earthquake simply proved it.
Thousands of mobile phone users were unable to connect calls in the hour following the 5.6 earthquake that struck the Bay Area shortly after 8 p.m. Oct 30. The reason is simple enough: networks always are under-provisioned. They are designed for a "normal" peak demand, and a large unexpected demand will simply swamp any network.
Wireless carriers said traffic spiked up to 10 times higher than normal, primarily with calls to family and friends, news outlets and emergency services.
The flood of calls also tied up at&t's landline phone service.
In a strict sense, the wireless 911 network continued to function. The problem is simply that when the access network is really congested enough that call attempts are blocked, any given call--to 911 or to any other number--simply can't be completed.
The solution? Use text messaging for non-911 calls. It doesn't tax the network as much.
