A fascinating article on cell phone service overload can be found on Crowe's website.

In the article, Crowe points out that wireless systems are assigned limited frequencies, and "the amount of frequency that can be used in one place is also constrained by neighboring cells needing to use part of the same block and the amount of radio equipment installed in the cellsite. With analog and TDMA/GSM cellular systems, the number of users who can be supported in a single cellsite is a simple function of the number of transceivers installed, but with CDMA it is more complex."

"No matter what the technology," he writes, "cellsite capacity is carefully engineered to ensure that the undesirable tone known as 'fast busy' (two beeps per second versus one beep for normal busy) is rarely heard, even during the busiest times of the day. This tone indicates a lack of resources for the call, usually radio capacity, although sometimes it reflects the lack of a connection back to the main switch or other network overload or failure situations."

An event such as the Minneapolis bridge collapse can generate as much as 10 times more cellular traffic than normal levels, Crowe says. For example, Crowe, who is based in Canada, notes that the Dawson College shootings in Montreal last September led to 11 times the amount of normal traffic. "It is impossible for cellular carriers to have this much extra capacity in place," he writes. "It is not just that this would increase the cost of cell phone communications several-fold, something that consumers would not tolerate, but there simply is not enough frequency available in many locations, particularly in urban areas."

What's interesting to note is just how much companies rely on wireless communication services for their disaster recovery and business continuity plans. "I would suggest that [CIOs] ensure that their wireless communication is split between at least two carriers," Crowe advises. "[CIOs] should all have long-distance cards as well, so that if their cell phone isn't working perhaps they can find another phone."

Crowe points out that the Minneapolis bridge tragedy should remind businesses and CIOs that it's wise for disaster-recovery teams to play out all kinds of different scenarios. For example, he says, what would they do if a bridge took out their sites and their cellular communications functionality? What would be their most critical communications needs, and how could they be accomplished?