Public Safety Advocate: Public Safety Spectrum, Interoperability, and the FCC

This week’s column is late due to my travel commitments this week and there will be no Advocate next week since I will be in Santa Barbara, my old stomping grounds, to meet with several agencies so we can update each other on several projects that are in the works. I will also be dropping in on the County Sheriff, whom I worked with, and briefing him on the status of FirstNet and public safety communications in general. And I want to meet with the County to discuss its proposed move to 700 MHz and how this will affect the County fire department’s ability to communicate with surrounding agencies, Cal Fire, and the U.S. Forest Service, which are currently planning to stay with VHF for their Land Mobile Radio (LMR) systems. 

Unfortunately, as in California and elsewhere, too many agencies are upgrading to higher frequencies to take advantage of conventional, trunked, and simulcast P25. In many cases, this upgrade requires departments to deploy two radios per vehicle and multiband LMR handhelds. These new configurations are more complex and thus it is more difficult to match today’s level of interoperability with neighboring agencies. Of course, FirstNet was designed to deliver this interoperability. When other agencies in the area are also on FirstNet, FirstNet’s PTT, data, and video capabilities will be available to all of them. Further, with FirstNet they may be able to eliminate the second radio on their older analog channels. 

There is one caveat. During major incidents and wildland fires, agencies employ many simplex or off-network communications channels. In many areas today, these channels are used by multiple agencies. When an existing system is converted to an exclusively-P25 system, it will still be capable of simplex or off-network, but in many cases it will not have the number of channels available on say, the VHF band. In the Santa Barbara area, we experienced a number of major fires for which all available simplex channels were in use. 

During major fires and other incidents, simplex is critical to public safety communications. Everyone who fought so long and hard for the creation of FirstNet did so primarily to achieve interoperability between agencies. However, until and unless FirstNet, LTE, or broadband networks used by public safety can provide the same level of off-network or simplex communications, channels, and range as LMR systems, we must be careful about moving agencies to the P25 digital standard simply because P25 has been implemented by most public safety agencies. (Some smaller departments are moving to Digital Mobile Radio (DMR), which is much less expensive.)

There needs to be a balance between what is required today, what might be available tomorrow, and how to make the transition. Relying on FirstNet or any LMR network as your only mode of communications means that if either or both networks are down, public safety will have no way to communicate. According to an old story, a city council called its police chief in and asked him to justify why the police department needed to upgrade its communications system. He supposedly placed his pistol and his two-way radio on the table in front of him and said, “If I had to do without one of these, it would be the pistol.” As the story goes, he got his funding.

Spectrum

All I discussed above depends on FirstNet continuing to build out its network and the federal government leaving land mobile radio, 6-GHz, and 4.9-GHz broadband systems alone. The first real danger to this spectrum is the T-band giveback. Hopefully, the bills in Congress will be passed and those who use the T-band can breathe again and turn their attention back to expanding their systems. Next up is the challenge to the 6-GHz band. While this band is not used by public safety directly, it is the primary band for microwave connections between public safety sites, control points, and in many cases dispatch centers. Many other organizations use the 6-GHz band for microwave including cellular companies, power companies, gas companies, cities for high-speed broadband between buildings, and more. 

It is important to remember that most 6-GHz systems were installed when the Federal Communications Commission (FCC) decided to auction the 2-GHz spectrum that was being used for microwave. This spectrum was auctioned as the “AWS bands” and as a result, public safety and other agencies were forced to relocate to the 6-GHz band.

The threat here is that if the FCC and those pushing for these actions have their way, unlicensed users will be permitted to land on the 6-GHz spectrum. We are told unlicensed use will be controlled by means of a master database that will coordinate use of the spectrum. If you believe for a moment all those with access to unlicensed equipment will follow the rules, you are wrong. If you believe a master database will prevent interference, you are wrong. 

To see how this doesn’t work, all you have to do is look at the TV white space database to see how much interference there is to and from unlicensed systems even though interference is not supposed to occur. In the case of unlicensed use it is difficult to identify the offender. In several instances there was interference to licensed public safety agencies using T-band LMR that was caused by licensed TV stations. When both are licensed it is easy to determine the identity of the offender and address the problem. Solving the problem is another matter.

Today, public safety and other licensed spectrum users spend a lot of time and money mitigating interference to and from their systems. In most cases, offenders can be identified through their FCC licenses. However, it is an entirely different story when someone is using a $25 Chinese radio that was shipped with public safety channels already installed or easily programmable. Unfortunately, there have been many reports of these types of radios being used to interrupt and jam public safety communications. (If you do have a problem with this type of interference, you might find it worthwhile to talk to ham radio operators since many have been trained to identify illegal transmitters or other devices that interfere.)

Those who want the 6-GHz band open to unlicensed use swear a master database that will coordinate use of the spectrum will be 100-percent effective in preventing interference. In my estimation, this is a disaster just waiting to happen. For whatever reason, the current FCC is concerned only with keeping vendors happy and how much spectrum can be found to sell at auction—with no concern about possible consequences. This is a harsh statement but time and again the FCC has proven its veracity. As with pollution of our lakes and rivers, spectrum can and is being polluted by other spectrum users, even when they follow the rules. 

FirstNet (Built with AT&T) also employs 6-GHz microwave spectrum as part of its network. Interference to one FirstNet’s 6-GHz links impacts more than one LMR system, it impacts the FirstNet system itself, perhaps over a larger area. I don’t know how intelligent people charged with overseeing our spectrum can justify playing Russian roulette with it!

Spectrum Noise Floor

I have previously discussed what is called the noise floor, which is the level of noise present in a given portion of spectrum when there is no radio activity. When I was on a project for the Idaho National Labs, I was given a tour and later worked on their radio range. While there is a very low noise floor in most of the spectrum, interference tests can be conducted on this range with the assurance that there is no outside cause of noise. In my location in Phoenix where I have lived for only three years, I have used my spectrum analyzer to periodically read the noise floor on 2.4 GHz (WiFi for example). I have found the noise floor here to have significantly increased over the three years. What this means to WiFi users is their existing systems now cover less distance and are slower than they were. The answer of course is to buy a repeater or more WiFi access points, which will inadvertently add to the noise floor.

What is needed is an organization that will be more of a guardian of the spectrum than the current FCC, which continues to try to find more spectrum or spectrum that can be shared, regardless of the consequences. 

The last piece of spectrum under attack (at the moment) is the 4.9-GHz band. This band contains 50 MHz of spectrum and it was licensed years ago to public safety. The thought was that this spectrum could be used as public safety WiFi and at first only an area-wide license was needed. Then it was determined that 4.9 GHz is also a great place for point-to-point communications over short distances and the cost to implement is less than rolling out a microwave link. When establishing a point-to-point system today, an existing license must be modified or a new license specifying the points that will be connected will be required. In many locations the band is being split into 10-MHz, 5-MHz, or smaller segments for low bandwidth use. It can also be grouped into 20-MHz and greater swaths for HD video (for example). 

Now the FCC and others want to turn the 4.9-GHz band into a shared band because the perception is that it is lightly used. This perception is not based on fact or research, nor is it based on previous commitments to public safety. The public safety community has been assured this spectrum will remain exclusively for public safety use for more point-to-point video links and perhaps WiFi bubbles that can be updated to encrypted 4.9-GHz around FirstNet-equipped vehicles. At the moment, public safety has taken a wait-and-see approach until the FCC makes up its mind. 

Winding Down

I am told that in late August or September, NIST/PSCR will be uploading videos of the PSCR 2019 Stakeholders Conference sessions. That is a lot of video to watch so I will probably choose to listen to only the sessions of most interest to me. Even so, I know that by not actually being there I missed a lot of information that was presented or discussed during coffee breaks. 

This week took me to Chicago, next week to Santa Barbara, and then a break until APCO. I enjoy traveling and talking with public safety people and others, especially during the Phoenix hot spells. Unfortunately, this time it appears I might be headed into heat along with humidity in these other destinations. As long as you don’t touch anything metal that has been in the sun, 114-degree heat with 7-percent humidity is not as bad as 100 degrees with much higher humidity. Yet even in heat and humidity, law enforcement personnel, firemen, and paramedics are out answering the call doing what they are trained to do. My hat is off to them!

Andrew M. Seybold
©2019, Andrew Seybold, Inc.