When Communication Systems Fail

Good communications are essential in any emergency


On September 11, 2001, much of the telecommunications infrastructure in lower Manhattan was destroyed. The public and private radio networks used by the police, firefighters and emergency personnel were limited in their effectiveness because of catastrophic infrastructure damage. This severely limited the ability of emergency personnel to communicate effectively, thereby exacerbating the difficulties inherent in crisis management.

On September 18, 2002, The New York Times reported that 21 minutes before the second tower collapsed, police helicopters were hovering near the tower to check its condition. A pilot radioed: “About 15 floors down from the top, it looks like it's glowing red.” Seconds later a second pilot radioed, “I don’t think this has too much longer to go. I would evacuate all people within the area of that second building.”

That knowledge never reached the emergency personnel. This interoperability problem contributed to the failure to inform firefighters and police of the tower’s imminent collapse. The problem was most apparent when Mayor Rudy Giuliani attempted to coordinate the efforts of emergency agencies by speaking into an ad hoc assortment of microphones and radios.

Good communications are essential in any emergency. Today, the primary means of communication are the public switched network, cellular, broadband, and private radio networks. Landlines have the greatest network capacity, but their fixed location and lead time for installation make their use impractical in emergencies. Even with their redundant network capability, landlines are subject to blocking when extremely large volumes of traffic occur unexpectedly. For example, after an earthquake on the West Coast, it is not unusual for residents of the area to experience busy signals for hours as the result of blocking in an overloaded network.

The fastest-growing method of communication is the public cellular network. The wireless spectrum is limited and usage is growing, so it is not uncommon to experience delays and blocking during peak periods. Blocking occurs most often during emergencies when call completion is most important. On September 11, 2001, in New York City, more than 75 percent of the wireless calls were blocked. On that same day in Washington, 50 percent of the calls were blocked.

When emergency personnel, various media, and the cell-phone-equipped public converge at disaster sites, it is no wonder the cellular network experiences blocking almost immediately. While the telecommunications industry has established standards for the prioritization of service to emergency personnel, this action has not resolved the problem.

The public switched network has built-in redundancy and can reroute a majority of the traffic around a cable cut or central office failure. Cellular and PCS networks are much more fragile. An inoperable tower, base station or antenna means that thousands of people may lose coverage in a specific geographic area. The trend is for carriers to increase the strength of the point of presence (POP), particularly in metropolitan areas, rather than to create new POPs. This network architecture may be more cost effective, but it creates a brittle network that is more likely to suffer major outages.

The blackout of August 2003 demonstrates the viability of relying on cellular telephony for priority access or mission-critical communications. The cellular networks proved unreliable, since their battery backup systems are effective only for short power outages, and many transmitters were left without power after a short time. Even after electrical power was restored, call volumes of four times the norm contributed to many calls being blocked.

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