Hurricane Irene Tests Resilience of Communication Networks

The Federal Communications Commission (FCC) and wireless carriers report that although Hurricane Irene didn't cause major damage to communication infrastructure, thousands of cell sites are down or running on backup power.

On Sunday, the agency reported that Irene had brought down around 1400 cell sites in North Carolina and Virginia. After the storm moved northward through Connecticut, Rhode Island, and Vermont, an updated report stated that 6500 cell sites were down along the East Coast. Recent updates show Vermont with 44 percent of its cell sites down—a higher percentage than in other states.

Cell sites (or towers), which contain the elevated antennas and communications equipment that provide mobile phones with a frequency, typically run off the power grid, though many have independent power sources in place as backup. In the wake of Irene, generators and batteries kept many cell towers online, but service disruptions could increase in the coming days as backup fuel and batteries run out. That could put additional stress on the cell sites still in operation. But service providers like Verizon, Sprint, and AT&T say they distributed extra generators and sources of backup power to cell sites before the storm against that possibility.

Repairs are also happening quickly—the FCC reported Monday that only 11 percent of cell sites in North Carolina are down, an improvement of 14 percent from Sunday's numbers.

The FCC’s Sunday afternoon report also said 130 000 wirelines were down and 500 000 cable subscribers were without service. A day later, those numbers rose to 210 000 and 1 million, respectively.

The FCC collects outage data from telecom companies through its Disaster Information Reporting System (DIRS). Wireless, wireline, broadcast, and cable providers are encouraged to enter outage data in the system on a daily basis during disasters, though the process is voluntary. To keep up its own assessment of communication systems, the FCC also uses spectrum analyzers in areas affected by disasters. The effort is called Project Role Call, which is jointly run by the Department of Homeland Security and the Federal Emergency Management Agency.

Federal assessments ran in parallel with service providers’ efforts to make repairs to their network equipment. Though most telecom companies aren't providing explicit data about outages to the public, AT&T has been tweeting about recovery efforts. “We are currently seeing some impact to our network along the East Coast, and stand ready to respond as soon as our crews are safely able to,” @ATT tweeted on Sunday. Before the storm, the company also used Flickr to publicize some of its hurricane preparations, such as the use of mobile cell towers.

Cable companies are keeping customers informed with Twitter and special sections of their websites. Time Warner customers in the Carolinas, for example, can get some status updates from @TWCCarolinas, and Cox Communications is keeping a tally on restoration of service to affected areas.

Even those who lost power were able to use Smartphones, tablets, and laptops to stay connected to news and social networks. This helped users stay online to contribute to crowd sourcing projects like this map, which is being used to track everything from weather to damages to clean up efforts:

mappingIrene

Though there was no shortage of users with access to their social networks over the weekend, the effects of the storm on Internet service providers varies by report.

Underground cabling has not yet been formally assessed, but FEMA says that flooding will continue to be biggest issue associated with the storm. The Associated Press reported that the fiber optic cables that run underground through much of New York City were unharmed by the storm’s floods. Those fibers, the report says, are usually wrapped in copper tubes, water-repellent jelly, or water-absorbing powder to protect them from potential water damage.

One of Vermont’s telecom providers describes extensive damage to underground fiber networks:

"Our redundant fiber rings were cut on both the western and eastern sides of Vermont, and also en route to Boston, and also west-to-east connecting Springfield to Wallingford, and also north-to-south connecting Springfield to Hartland, Chester to Grafton, and Wallingford to Killington. In cases where our fiber is (or was) on bridges that washed away, or under roads that eroded, the repairs require coordination. By far the most-isolated of our service area is Killington, where our fiber ring follows Route 4 and Route 100, and both roads washed out."

Most networks have built in redundancy: Wireless networks can serve as backup for broken cables, and mobile devices can rely on alternative cell towers. Of course limits exist, as evidenced by last week’s earthquake. The event caused noticeable cellular service disruptions, caused by network congestion. But whereas wireless carriers had advanced warning of Hurricane Irene, the earthquake wasn’t forecasted (or quite the media frenzy), and not enough resources were allocated to accommodate bursts in call activity.

A few sources have noted that service disruptions caused by power outages might have been lessened with smart grid technologies. As Chicago’s ComEd stated in an interview earlier this summer, utility companies still rely on customer reports to identify outages, and a downed wire can often knock out large areas of service at a time. The utility says that a smarter grid would automatically pinpoint outages and isolate damaged circuits. A utility could even reroute power in high-risk areas before a storm, perhaps even sparing parts of the grid that are critical to communication infrastructure.

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