Public Safety Agencies Switching From Analog Radios Must Combat the ‘Digital Cliff’

After a digital radio system failure during a blaze on Oct. 1, the Fire and Rescue Department in Toledo, Ohio, established an evacuation policy to better protect its firefighters.

System or programming errors, called “failsofts,” causing emergency personnel to lose contact with dispatchers aren’t necessarily common occurrences, but in zero-visibility situations they can quickly become a firefighter’s worst nightmare.

While nobody died in Toledo, that wasn’t the case in a 2013 fire in Houston, where four firefighters died after malfunctioning radios left them communicating with hand signals during a blaze at the Southwest Inn.

“Digital is either there or it’s not,” Lt. Matthew Hertzfeld, a Toledo Fire and Rescue spokesman, told Route Fifty in an interview. “One of the challenges that we face is if firefighters are deep in the bowels of a building or surrounded by a lot of metal or separated by a lot of concrete, and they could be in an area with great coverage.”

Strong overlying coverage means little if a signal can’t reach emergency personnel where they’re operating.

The ‘Digital Cliff’

Cities transitioning away from analog radios like the type Houston was using must deal with the “digital cliff.”

Unlike with analog, where the sound gets increasingly scratchy as a user nears the edge of coverage, digital provides a clear signal until it immediately cuts off.

Digital radios offer plenty of advantages: They filter out background noise better, are more reliable inside buildings, provide stronger encryption and connect compatible systems more effectively and securely. But users are often overlooked in the switch from analog antenna sites and hardware to digital.

Emergency radio conversations typically last 2 to 3 seconds, so the dispatcher can ascertain the status of the user, said Jim Reid, spokesman for Melbourne, Florida-based communications company Harris Corporation. Retraining the human ear to unlearn “comfort sounds” associated with analog after going digital takes three to six months. Personnel should be taught to expect differences prior to deploying digital systems.

“What really determines the success of migration from one technology to another technology is the participation of the user,” Reid said. “Don’t shortcut operator training to save money or time.”

When Miami-Dade County in South Florida began its transition from analog to digital about five years ago, the digital cliff proved the biggest difficulty, Chief Information Officer Angel Petisco said in an interview. So the county was proactive in providing training and advanced simulations on the new communications environment, though people still called in saying their radios were too loud.

A yell is a yell in the digital world, as Petisco puts it.

The 97 Percent

Almost two years since Miami-Dade’s system was completed, it’s received high praise because the county not only relied on coverage maps but ride-alongs with public safety officials to pinpoint radio service dropoffs.

The general goal everywhere is 97 percent coverage with that last 3 percent hard to achieve due to physics and tight budgets. Covering 80 percent of a system’s area might equal 20 percent of the cost, Reid said.

Denver has around 15 to 20 antenna sites in its system, but it could need 30 percent more sites for maximum coverage in its downtown area. That’s because urban geography can be tough to maneuver around, and antennas need to be relocated and tradeoffs made to optimize costs.

Miami-Dade’s analog system was configured in the early 1990s with 95 percent coverage. But over time the county grew larger than several states, and its urban landscape changed—making it one of the most densely populated systems in the nation.

Because about 30,000 subscribers across 109 agencies at the municipal to federal and even tribal levels rely on Miami-Dade’s system, upgrading equipment, repositioning antennas and adding sites to improve coverage was the equivalent of “replacing a flat tire in a moving vehicle,” Petisco said. Still the county did it without major service disruptions working with Sprint and Harris Corporation.

County officials identified four traditionally low-coverage areas within the approximately 2,000 square mile county for new antenna sites, the latest of which were added a little more than a month ago.

“By doing that it created other challenges we weren’t necessarily anticipating,” Petisco said.

The county projected 100 percent coverage improvement in certain areas but was surprised to find closer to 80 percent improvement because some directional antennas overlapped to create interference. That led to noise on the channel and made it difficult for users to get on, so infrastructure had to be adjusted and directional amplifiers, or repeaters, installed in large buildings and arenas.

“When looking at a map of a county, there are a lot of things—hills, trees, buildings—that block signals,” Reid said. “The key to cost-effective coverage is determining what areas are not as important to coverage, which could be a lake or marsh.”

All said and done, Miami-Dade’s system operates around 95 percent coverage with $25 million spent to keep the new infrastructure initially covered by a federal grant and $3.6 million earmarked for improved coverage. A successful active shooter exercise involving all county public safety agencies and using the communications system was recently staged.

Safeguards

When problems arise with digital radio systems, as they did in Houston, the situations can quickly become political, especially when they attract local media attention.

Toledo attempts to keep communication lines open by placing repeaters in radio coverage-challenged places like hospitals and underground, while also having backup systems in place if all else fails.

Radios begin to beep when they can’t transmit or receive signals from dispatch, a warning to emergency personnel, and a talkaround channel allows units in close proximity to still communicate.

According to Toledo Fire & Rescue’s new evacuation policy, when dispatch can’t be reached during a fire, the incident commander will order nearby fire apparatuses to sound their horns three times, pause and repeat. Firefighters hearing the horns know to immediately exit the burning structure, while the incident commander conducts a personnel accountability report and consults with the safety officer on scene about whether it’s feasible to continue internal operations. If not, firefighters will fight the blaze defensively from the outside.

“Generally, if there was a problem with radio communications, firefighters were directed to leave the building,” Hertzfeld said. “What this procedure does is formalize that process.”