In emergencies, can cell phone network overload be prevented?

High call volume temporarily flooded networks after last week's San Francisco quake

Within minutes of Tuesday's 5.6 magnitude earthquake that hit the San Francisco Bay Area, the number of cell phone calls on the Verizon Wireless network skyrocketed.

Twenty minutes after the 8:04 p.m. quake, instead of the normal 300,000 calls made between 8 p.m. and 9 p.m. in one area of Santa Clara County, the call volume soared to 2.3 million. Many of those calls were probably made by people trying to check on friends or relatives who lived in the vicinity of the temblor.

And many of those calls never got through because, as often happens after a major emergency, the huge number of cell phone calls overwhelmed systems that weren't built to handle such high demand. Instead of reaching their destinations, the calls received fast busy signals or messages saying that all circuits were busy.

The incident raises the question: Is this acceptable service? Or can the system be fixed so that every call can go through at anytime, no matter how many calls are being made?

It's not a yes or no answer.

Yes, it could be done, according to wireless carriers, but it would be expensive, and would lead to an overbuilt network that's needed only a few times each year.

"It's not appropriate or feasible," said Chuck Hamby, a spokesman for Verizon Wireless in Tampa, Fla., where hurricanes are a fact of life and frequently cause problems for cell phone networks. "You could build, at least theoretically, a network that has enough capacity for everyone in the United States to get on the phone at one time, but [the required switching facilities] would be the size of the Empire State Building."

Instead, wireless carriers build specific cell site buildings that can handle the capacity that's needed in each individual area, and that capacity can be increased as needed, he said.

Usually, those capacity needs are met because the wireless carriers monitor the call volumes to keep up with normal demands. But when a natural disaster or some other unusual incident occurs, demand peaks, causing the call congestion that hit the Bay Area Tuesday night. "Only in truly unusual events do you see this," Hamby said.

If cell phone systems were overbuilt to handle those occasional but huge spikes, more cell towers, which are controversial in many communities, would need to be built a lot and the added expense would be passed on to customers, he said. "That 60% overcapacity would then sit idle probably 364 days a year" until it's needed in an emergency. "It's probably not the best use of the resources."

Verizon said its systems in the Bay Area worked fine when the earthquake occurred and that all systems were back at normal performance levels 30 minutes after the event. None of its cell phone towers were damaged or lost power because of the quake, the company said.

The "circuits are busy" messages callers receive are the expected response when the system is overloaded and worked just as designed, Hamby said. "Don't worry. Nothing's broken. It's just too many people trying to get through a revolving door at once."

Heidi Flato, a spokeswoman for Verizon Wireless in Northern California, said no company can economically or realistically build a stout-enough network to handle situations such as the call spikes that came in Tuesday night after the earthquake. "In general, we build for the type of usage we see on a day-to-day basis," Flato said. "To build for that sort of need, for that sort of circumstance, it's like building a second [San Francisco] Bay Bridge just in case the first one falls down. It's just not feasible."

Mark Siegel, a spokesman for AT&T Wireless, said large spikes in call volumes after emergencies or other events will always cause some callers to experience difficulties in getting their calls through. As an alternative, callers should try sending short text messages, which use less capacity on the networks because they pass through in bits and bytes instead of requiring a dedicated circuit as a true phone call does.

Roger Entner, a telecom analyst and senior vice president of the communications sector at New York-based IAG Research, agreed that cell phone carriers can't feasibly build networks that can hold up under every conceivable emergency and allow every call to go through.

"If you live in an unlimited resource world, it's certainly possible, but we don't live in an unlimited resource world," Entner said. "The wireless system is not advertised as the system of last resort. Nobody ever made the claim that this system will work always."

Emergency first responders have cell phones that use codes to automatically route their calls to the highest priority to ensure they get through, Entner said. "Those safeguards are in place," he said. "Yes, we are being inconvenienced in an emergency [when our calls can't get through]. I think people should be able to accept that."

One problem in building more capacity for emergencies, he said, is that the wireless companies don't know where emergencies will happen, so they have no way of building in the extra capacity ahead of time since mobile phone users are, well, mobile. With wired phone service, the phone companies already know where the service demands are because people and businesses are in fixed locations.

Wireless carriers know that an NFL football game will boost capacity needs at the stadium because of the 70,000 fans in attendance, and the carriers can bring in portable equipment to bolster the capacity temporarily, Entner said. "In a disaster, you can't anticipate that."

Jeff Kagan, an independent telecom analyst in Atlanta, also said it's unrealistic to expect that cell phone companies can make their networks big enough to withstand occasional high-volume needs.

"It's a constant balancing act between having the capacity but not having too much capacity so that you have to charge customers more and be uncompetitive," Kagan said.

Another analyst, Ken Dulaney of Stamford, Conn.-based Gartner Inc., sees it differently, however.

Today, cell phones have become so "mission critical" for users that new ways need to be found to make them work more efficiently during emergencies, he said, even when the networks are overloaded. In many homes, he said, wired phone service is no longer used, making cell phones or VoIP phones the only means of telephone communication. If the power is out, VoIP phones won't work, making cell phones even more important, he said.

Dulaney said alternatives, such as metering cell phone use in emergencies so that all users can get some time to make their important calls, need to be reviewed. Another alternative is a callback service, like those used in the 1950s, where if a circuit is busy, the customer gets a phone call back when the circuit is available to make a call, he said.

"I think it's going to require government regulation" in the future to make it equitable, he said. "This sort of rationing of calls is the only way to take the existing [network] capacity and let people use it. You've got to go to a rationing mode just like in any emergency."

Copyright © 2007 IDG Communications, Inc.

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