As part of a $25.4 million upgrade, State Civil Defense officials are changing how they activate Hawaii’s tsunami sirens.

They’re dumping a decades old high-frequency radio system and instead moving the sirens to cellular and satellite networks.

But everyone knows how hard it is to connect to the network during an emergency when people are trying to use their cell phones all at the same time.

Hawaii is not getting any special signal prioritization — Verizon has guaranteed the state the same level of service afforded to any other customer.

Will the sirens work during an emergency? Cellular network experts say the answer is probably yes. But there’s no way to know for certain until there’s an actual emergency.

“I am skeptical of anything that would only rely on satellite or only rely on something that would be carried over the Internet,” said Jamie Barnett, the Federal Communications Commission’s former chief of public safety and homeland security. He’s now with the Potomac Institute for Policy Studies, a Virginia-based think tank.

“If the cell system doesn’t work, will in fact satellite be enough?” he said. “I don’t know how you can test that except live (during an event). And that may not be the best time.”

The sirens will eventually operate exclusively on Verizon’s M2M (machine-to-machine) data network, which is separate from its voice network, according to state officials.

When a voice network overloads, it doesn’t accept new connections. Whereas a data network works more like an Internet connection: when there’s a lot of traffic, the network doesn’t respond as quickly.

Data networks “don’t crash generally. But they slow down,” said Roger Entner, a Boston expert on telecom and cellular networks. “For the first signal — no problem at all. But from the data side, it can slow down significantly, so where that might become a problem is if there is a second alert.”

During a tsunami warning, the sirens sound at least three times. The first coordinated statewide sounding of the sirens occurs three hours before the first wave’s arrival, then hourly afterward. The sirens sound a fourth time 30 minutes before the tidal wave is scheduled to hit.

As a backup, sirens are also outfitted to respond to satellites. But even that technology has its weakness: weather can interfere with satellite signals.

But Entner wasn’t too concerned about that.

“You always have that backup solution,” he said. “How big is the likelihood that when the second siren calls there’s heavy downpours over Hawaii — and a tsunami and the commercial data network comes to a crawl?”

During the 2011 tsunami warning caused by the Japan earthquake, the AT&T network failed completely across Hawaii for commercial and municipal users alike.

AT&T representatives cited higher-than-normal phone usage. On Maui, county officials had to dump their iPhones and rely on walkie-talkies to communicate. It’s still unclear whether unlucky timing of AT&T’s rollout that night of a new iPhone software upgrade exacerbated the problem.

New Technology Costs About The Same As Buying News Radios

Experts say the most foolproof way to make sure that the sirens will sound during an emergency is for the government to build a private Internet.

And there are plans in Congress to do so. Last year, Congress made the first appropriations to build a public safety broadband system called FirstNet.

But it could be awhile before the network expands to include Hawaii.

“This is something we’ve been watching very closely that we want to take advantage of,” said George Burnett, Civil Defense telecommunications branch chief.

Hawaii’s move from high-frequency radio to cellular and satellite technology is in part a financial decision, he says.

The Federal Communications Commission has mandated that cities move away from high bandwidth communications to one that uses a lower bandwidth.

“Instead of spending money to replace the old radio system, we thought let’s replace the technology altogether,” Burnett said. “The two costs were roughly in same ballpark.”

Buying new, lower-bandwidth 800 MHz trunk radios costs about $570,000 more than leasing space on commercial satellite and cellular networks, he said. The service cost of operating sirens via satellite and cellular is $11 per month. Amortized over a 10-year period, combined with the lower cost of related equipment, there was a cost advantage.

The old system relied on radio transmitters that would communicate through mountaintop repeaters. But the repeaters didn’t have coverage everywhere. And there was no two-way instant communication with the sirens. The advantage of using cell networks is that the siren sends back an error message if it doesn’t sound.

Misfiring sirens were an issue after the Oct. 27 tsunami warning. State officials said many sirens are old and until upgrades are completed, there will always be a handful that don’t sound. For those older sirens without wireless technology, Civil Defense relies on conscientious neighbors to report malfunctioning equipment.

Civil Defense has signed a 5-year agreement with Verizon to lease service on its wireless cellular network. Inmarsat is providing the satellite service. Verizon does offer priority access on its voice network for emergency personnel during a crisis, but the feature does not exist on its data network.

“Everywhere where we have a siren currently installed, we’re able to verify there was cellular data service available,” Burnett said. “So it gives us better ability to expand in areas where we didn’t have radio coverage.”

The new cellular and satellite technology has been installed in 141 of 152 state-owned sirens on Oahu, with the others soon to follow.

Civil Defense’s statewide siren modernization plan calls for complete upgrades of 125 of the state’s 371 sirens and adding 146 new sirens.

So far, it has $17.4 million in funding and needs another $8.2 million.

No other state has a statewide siren network, Burnett said.

So with this move to satellite and cell networks, Burnett says the state doesn’t have others to look to.

“We’re trailblazing,” he said.

In 2010, Verizon Wireless invested nearly $40 million in its Hawaii network and services, bringing the company’s spending in the Aloha State to more than $254 million in the last decade, according to a company statement.

“Verizon has a reputation for putting a lot of focus on their network, they are really network centric,” said Entner. “I would say Verizon is certainly a good choice.”

View a powerpoint by Hawaii State Civil Defense on their tsunami warning siren modification plan:

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