A Primer on 700 MHz

Technology moves at a rapid pace, and one area in which the fire service has seen a tremendous amount of innovation during the past 10 to 15 years is communications. Not limited to point-to-point communications on the fireground, communications now includes cell phone usage, mobile data computers (MDCs) or mobile data terminals (MDTs), voice and alphanumeric paging systems, along with the ubiquitous two-way radio.

After September 11, 2001, interoperability between responding areas became the focal point of municipalities around the country. Employing unified command (UC) means public safety representatives from all departments must be able to communicate. Technology for voice was in place for this to happen, but interoperability was yet to be achieved. Many departments or counties transitioned from a UHF or VHF radio system to analog trunked systems and later to digitally trunked systems. With these types of systems, capacity is critical, and many municipalities found they taxed the systems relatively quickly, particularly because of the number of portable radios in the systems.

When the United States transitioned from analog television broadcasting to digital broadcasting, 22 megahertz (MHz) of spectrum in the 700 MHz band became available to public safety, adding not only capacity for voice but also broadband capabilities for data transfer. This bandwidth’s availability has been confusing for some, and others have questioned why this is important to public safety agencies. What it boils down to is that this spectrum dedicated to public safety can be viewed as an additional communications tool.

Defining the Band

Mary Doherty, director of business development, Harris Corporation, says that the 700-MHz spectrum became available through the digital television legislation. “Back in 2009, this spectrum became available. In that legislation, Congress allocated 10 MHz of spectrum—five MHz on the uplink and five MHz on the downlink for the broadband spectrum—as well as 12 MHz for the narrow-band spectrum,” she says. Between June 2009 and May 2010, she continues, a number of counties, cities, and states applied to the FCC for waivers. “The FCC had not made final rulings on how it could be built out,” she says. “In the legislation, Congress said that the 10 MHz will be used for a nationwide interoperable network and the FCC will determine the final rule of what that means.” So, in May 2010, the FCC issued waivers to 21 entities to build out networks. There are conditions of the waivers, one of which is that they must use long-term evolution (LTE) technology. LTE is one of the major benefits to the fire service because it provides higher speed data that can enable situational awareness applications, such as video, according to Doherty.

Narrowband vs. Broadband

According to Doherty, one thing to understand when talking about 700 MHz is that there are narrowband channels dedicated to public safety and also broadband channels dedicated to public safety. “In the narrowband space, there are a number of counties and states that have already built out systems at 700 MHz narrowband,” she says.

Roger Kohr, area sales manager, Pennsylvania, adds, “Many of the counties that are looking at the traditional 700 MHz that we think of when we see the firefighter or police officer talking on a radio either didn’t have the opportunity to get 800-MHz spectrum or need additional spectrum.”

Two different types of 700-MHz frequencies, says Kohr, means there are two different types of 700-MHz systems. “People hear 700 MHz and right away ask ‘What’s 700 MHz?’ and it just happens to be the frequency that has two different technologies,” he says. What causes confusion, according to Kohr, is that narrowband and broadband comprise two different sets of channels in the 700-MHz band. Customers looking for data will have an LTE need. On the flip side, Kohr says there are customers that will decide the public safety radio system they have used for years has done them well. They want to maintain that, but they will also put up an LTE system and use that primarily for data. “The confusion is people hear ‘700 MHz’ and they instantly think of the new technology, the LTE, and the broadband,” he says.

Digital Capabilities

Beyond the increased capacity for traditional push-to-talk communications (narrowband), the broadband capabilities of the 700-MHz band should be of interest to the fire service. For example, many departments use MDCs or MDTs in their apparatus and chief vehicles. Often these devices are linked to their municipality’s computer-aided dispatch (CAD) systems via a commercial carrier’s air card. If a municipality chooses to use the broadband capability of the 700-MHz band, the need to use a commercial carrier disappears. This is good for a few reasons. Doherty cites the example of the recent earthquake that impacted the East Coast. During the hours following the quake, cellular communication was almost impossible, which also would have affected the MDCs using air cards supplied by commercial carriers. “When there are incidents like the earthquake that we had in Washington, D.C., I had no phone service. I didn’t even have data service,” she says. “Sometimes when there’s an incident like that and a public network is overloaded, you can still text. I couldn’t even do that. That’s why public safety needs a private network.”

Doherty says there are a number of different applications that will only run on broadband. “For example, firefighters could download building plans so that they could see what a building’s structure looks like or what hazmat material may be there as opposed to now when someone at the firehouse might print something out and rip and run,” she says. “But, now they’ll be able to do it in real time. As they’re driving, they can have someone downloading that information and sending it to them over the air, or they can get it over the air themselves.” Another example she cites is in wildland firefighting, where firefighters could get weather information in a more real-time fashion.

Kohr cites an example in which broadband allows video to be streamed from a helmet-mounted camera to a command post, so an incident commander (IC) would be able to see what firefighters are seeing inside to help effect a rescue or fight a fire. “Video is the best way to be able to do that because it doesn’t require the firefighters to do anything, and the chief can be running command and seeing what’s going on in real time.”

Secure Networks

A public safety network differs from a public network in terms of how “hardened” it is to resist what occurred the day of the earthquake in Washington, D.C. and other natural disasters. “The big thing that’s been at issue for years, and this came out of Katrina, is that public networks are not as hardened—meaning they are not going to sustain damage or loss of power,” says Kohr. “When you’re building a public safety network, you’re trying to take many of the worst-case scenarios into consideration, and you’re trying to harden the network against those.” He states that most public safety sites are equipped with generators, battery backups, and so on to sustain operations for some period of time. Many public safety sites are supported with microwave links that are intended to keep these sites going for days or weeks, whereas many commercial carriers have battery backups that might only last a few hours and then they are out of commission. “When things are bad, that’s when public safety really needs its network to work.”

Doherty adds that, from the very beginning, the way a network is designed for a carrier network is very different from a public safety network. “In designing public safety networks, we’re looking at coverage,” she says. “In the carrier space, it’s about capacity and serving the population. And this is about covering the service area of our first responders, so it’s a different design philosophy as well.”

Implementation Models

The models for implementing a broadband network include the traditional build, own, and operate by the municipality. “Depending on the size of the service area, the more users you have on a network, the better your return on investment because you’re getting more service spread among more users,” says Doherty. “So, from that perspective, it can be a very good model, a very effective model for certain metro regions.” Doherty adds that another positive is that in this case, a municipality or department will work with a vendor or consultant to build out a network specific to that area’s needs. “The downside of that is that the operating expense can be pretty high,” Doherty cautions. “These cores are built for very large public networks, so they are scaled for that. We’ve scaled the cores down to make them more affordable. But, in the end, relative to a traditional land/mobile radio switch, it’s a lot more complex. So, that part of it is a little bit of a challenge, depending on the economics of a particular metro area or municipality.”

Another model is having regional cores, according to Doherty. In this case, one core might serve multiple states, making it more economical. She cites one example where a region owns a core, and then each state builds out its own radio access network (RAN), so they would pay for that infrastructure, creating a shared system.

A third model, which many embrace, is a hosted core. “They want some entity to host the core for them, as well as build up the network, and they would pay that entity as they pay a carrier,” says Doherty.

The Need for Clarification

Any time there is a change to the way public safety personnel communicate via radio, there is a certain amount of trepidation, as there is often some sort of equipment upgrade to do it. There are many municipalities that have already switched to and operate on an 800-MHz system that is either analog or digitally trunked. Doherty states that in many cases, adding broadband capabilities simply augments the narrowband systems already in place in many public service entities vs. replacing these systems: “There are a number of agencies that intend for this broadband network to augment the narrowband voice system they currently have,” she says. “What that will do is give them the data applications of downloading bulding plans, vehicle information, and so on. It’s not meant to replace voice.” That said, Doherty adds that there are some entities that actually do want to do push-to-talk voice over LTE. “You don’t have to give up your narrowband voice communications. LTE and narrowband systems can and will coexist, but we can also provide push-to-talk over LTE for entities that want that.”

An Additional Tool

When many came into the fire service, there was one dispatch channel, one responding channel, and one fireground channel. Then the 800-MHz band became available, which opened up an additional pool of frequencies for public safety. Now 700 MHz is here, but ultimately public safety organizations should look at it as another tool to be used for on-scene communications. What’s causing confusion is the broadband aspect of the 700-MHz band, according to Kohr. “There’s this new thing called broadband, which is going to run using LTE technology, and that is definitely something new that’s never been in the fire service before,” he says.

Even if public safety agencies view the 700-MHz band as an additional tool, it is critical to learn about the technology. “Get educated,” says Kohr. “All the changes going on between narrowbanding and rebanding of the 800-MHz spectrum and narrowbanding of VHF and UHF, and the new tool of 700 MHz, and the types of 700 MHz—education is key as the users go forward in deciding what they’re going to do now and in the future.”

In addition, Doherty suggests getting involved. “The FCC and Congress are acting,” she says. “From a local perspective, sending letters to congressmen to support legislation that will enable this is important.”

CHRIS Mc LOONE, associate editor of Fire Apparatus & Emergency Equipment, is an 18-year veteran of the fire service and a captain with the Weldon Fire Company (Glenside, PA). He has been a writer and editor for more than 15 years. While with Fire Engineering, he contributed to the May 2006 issue, a Jesse H. Neal Award winner for its coverage of the Hurricane Katrina response and recovery.

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