Sunday, August 05, 2007

As bridge failed, so did phone network - Surge overwhelmed cellular service

By Jon Van - Chicago Tribune staff reporter - August 5, 2007
Even before cable news channels began to spread news of Minnesota's collapsed bridge catastrophe, engineers at T-Mobile knew something was up because they saw a vivid shift in mobile-phone calling patterns.

"They turned on the radio, heard the news, and initiated a conference call at once," said Peter Dobrow, a T-Mobile spokesman. "They had extra radios installed at two cell towers nearest the bridges to double capacity within two hours of the collapse."

Other cell phone operators also said they moved quickly to meet the unexpected spike in network traffic, but even so, many customers found their calls couldn't get through.
At moments of crisis, the performance of cellular phones gets attention because they become potential lifelines. In the wake of the bridge collapse on Wednesday evening, when some people on the scene couldn't get a connection, questions were raised about whether wireless providers are adequately prepared to handle unexpected call volumes.

"My frustration is that any tower on any network should have an emergency line, or else towers should work for all networks in emergencies," said Omar Thompson, 32, of St. Paul, a customer service worker in downtown Minneapolis. His first calls to reassure loved ones got out, he said, but were increasingly drowned out by automated messages:

"Current network not available."

Everyone from emergency officials to office workers complained last week that cell phone signals seemed blocked out by the deluge of calls from trapped commuters and panicked families watching the news Wednesday night. Rescue workers, in their first test of a new universal radio system turned to their personal cell phones as back-up. Authorities asked residents of the Twin Cities to stay off their cell phones, fearing the clogged lines would hamper rescue efforts.

A text case for an emergency

Some experts said that service providers can't be expected to manage a sudden, huge uptick in phone calls in one location, but there is a sometimes overlooked solution during emergencies: using a cell phone to send a text message almost always works when phone calls don't get through.

That was how Jennifer Lupient, 25, a hotel concierge in Minneapolis, was able to trade messages with her boyfriend. Both use the Interstate Highway 35W bridge often, she said. But she was unable to get calls from concerned college friends who called her cell phone from out of state. Lupient got those messages the next morning, she said.

"Some calls would come in, others wouldn't," said Charise Rhodes, 36, a Minneapolis retirement education specialist. But the stream of text messages from nervous friends was reliable. "Tried to call," most began. Rhodes tapped out responses in reply.

"I ended up sending lots of text messages on Wednesday," she said.

Experiences last week in Minneapolis varied by carrier. Verizon Wireless estimates that at the height of demand, about 1 in 5 calls on its network to or from the disaster site didn't get through. People using wireless networks operated by Sprint Nextel didn't see excessive dropped or missed calls, said Dave DeVries, a Sprint spokesman, "but our landline long distance did experience several blocked calls for a few hours."

AT&T Mobility experienced trouble for a few hours and was poised to send in cell sites on wheels, or COWs, said Mark Siegel, an AT&T spokesman, but the network difficulties were over before that could be done.

"We don't send in a COW without a request from the authorities because we don't want to do anything to interfere at a disaster site," Siegel said.

Portable cell sites are regularly brought in for special events such as music concerts and sports competitions where carriers can expect that calling volumes will be higher than average, Siegel said. They may also be used in the aftermath of disasters such as the Sept. 11 terrorist attacks or Hurricane Katrina that require extra communications infrastructure for prolonged periods.

At the Lollapalooza music festival in Chicago this weekend, for example, there will be extra capacity from Sprint, which installed extra radios at cell towers to cover all of the seasonal festivities along the city's lakefront, DeVries said.

"We don't need a COW for the Grant Park area because so many events occur there, a longer-range solution makes sense," he said. "But for a one-time event, such as the Ribfest in Naperville, we did bring in a COW to handle the extra demand."

Emergencies, of course, are a different story because they are unpredictable, though the industry has learned a lot from extraordinary events like Sept. 11.

Making a connection

Cell phone networks have technology that enables them to give priority to people dialing 911 and to authorized emergency personnel, but no network can handle every call when traffic spikes at levels two or three times beyond normal, said David Chamberlain, principal wireless analyst for In-Stat, a market research firm.

"The public should just expect" cell phone calls to be blocked, he said. "It's going to happen. If I'm ever in a situation where my calls don't go through, I'll just send a text message. That will get through."

Because text messages require little network capacity and travel on separate channels from voice calls, they are always the preferred mode to assure a loved one that someone near a disaster is unharmed, said Sprint's DeVries.

While virtually all cell phones support text messaging and young people typically use it more than voice calling, it is utterly foreign to many older customers, he said.

"After the Virginia Tech tragedy, we suggested that it would be wise for parents with youngsters in college to learn to text message in case they needed to communicate in some kind of situation like that," DeVries said.

All cell carriers said that calling volumes declined enough to support normal service within a few hours after the bridge collapse occurred. The task now is to monitor changes in calling patterns in the Twin Cities due to a major thoroughfare being closed.

"We're watching network traffic to see how people are commuting," Dobrow said. "They're taking different routes to work and school, and we'll need to adjust capacity to adapt to those new patterns."

copyright © 2007, Chicago Tribune
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