Wireless carriers' disaster plans tested after storm

— -- Large wireless carriers stepped up disaster recovery efforts over the weekend as a rare derecho storm stomped through the Mid-Atlantic, and millions of cell calls and data downloads strained their capacity.

Many regional cell sites were still without power Monday, and customers complained of spotty or non-existent coverage. Industry executives and analysts say wireless networks, with cell sites designed to cover as much five to 10 miles, often struggle during heavy call volumes. But they also say a series of disaster-recovery measures the carriers put in place after Hurricane Katrina in 2005 helped mitigate disruptions during the weekend. "There has been a lot of effort to beef up and back up power," says Phil Marshall, a mobile network analyst at Tolaga Research.

Managing network capacity in disasters and large events has always been critical to carriers' operations. But the industry's investment in such efforts has ratcheted up in recent years, along with its greater ambition to install faster data networks and attract more customers using smartphones, Marshall says. Cell connections can be disrupted by malfunctioning equipment in any of the components in the network. The storm damaged some cell towers, cut off power at tower sites and destroyed connections between the towers and the nearby "switch" facilities that route calls.

With electricity out for much of the Washington, D.C., region, most recovery efforts involved delivering back-up power to cell sites. Verizon Wireless has installed generators at most cell towers, on top of back-up batteries at all sites that can last up to eight hours, says Mike Haberman, vice president of network engineering. In the last year, Verizon installed 1,300 generators nationwide. About 450 sites were running on generators as of late Monday.

T-Mobile, with about a quarter of its sites in the region down "for a short period of time," moved 200 generators and 12,000 gallons of fuel by Saturday, says Tom Ellefson, T-Mobile's vice president of engineering for the Northeast. About 85% of its cell sites in the area were restored as of Monday, he says.

AT&T says it has nearly doubled the number of portable generators for cell sites to about 10,000 in the last three years.

Carriers also have added fleets of trucks that function as cell towers on wheels. Sprint's cell tower truck fleet, which is used to boost coverage for large customers, has grown to 21 from five in recent years. T-Mobile's Ellefson says the company deployed three trucks to the D.C. region to boost coverage.

The industry's conversion from copper wires to fiber-optic cables in connecting cell towers to switch facilities also has helped ease disruptions, Ellefson says. "We've improved reliability and quality. … (Otherwise), we'd have seen more dramatic outages."