FCC Shifts The Interference Paradigm

The FCC has released a Policy Statement that contains spectrum management principles for transmitters and receivers.

Why should you care?

This document represents a seismic shift in how the FCC has assigned responsibility for curing interference. In this regard, we started long ago with a standard of “last-in, fix it.” Accompanying that was the concept that the interference had to be “harmful.”  Unfortunately, defining harmful became quite difficult, with some believing ANY interference was harmful.  However, remember even in Part 90 we have for many decades separated systems based upon a desired signal being heard at 50 percent of the locations in the licensed area 50 percent of the time, having a non-overlap with a signal heard at 50 percent of the locations, 10 percent of the time (using the TV R-6602 curves).  Thus, there’s an assumption from the start that there are SOME locations within a licensee’s service area where interference will occur.

But then came Nextel, and its interference to public safety.  We determined that we needed to better define what interference was, and that determination resulted in the adoption of Sections 90.672-675.  But those sections were created at the end of the analog era, without sufficient consideration of the changes that the digital era would create.

While we’ve refined the protocols that we used to determine what signals are out there, we really haven’t changed much of anything in terms of responsibility for curing it (other than Sections 90.672-675).  With the FCC’s decision to allow spectrum sharing between 6 GHz microwave systems and unlicensed devices, and the interference that will no doubt result in the field (all representations from unlicensed interests to the contrary), the FCC is now creating a shift in the responsibility quotient.

Before, an incumbent experiencing true interference could point to the interferor and force them to “fix-it.”  But we made a slight change in that dynamic in Section 90.672(1)(i), where the FCC set a minimum signal level that the 800 MHz licensee must be receiving at the location in order to be entitled to protection.  At the time we (meaning my office and Jay Jacobsmeyer of Pericle Communications) encouraged public safety entities issuing RFPs for new portable and mobile radios to get from responding manufacturers information sufficient to determine the ability of the proposed radios to reject unwanted signals.  This came on the heels of Pericle’s work in evaluating then-available equipment, which showed a huge variation amongst Part 90 equipment, a variance that didn’t necessarily correspond with the relative cost of the radio.

Now, more than 15 years later, the FCC is taking that to the next level.  Specifically, the FCC is talking about “shared responsibilities” between licensees, which the FCC says should include:

(1) transmitters should be designed to minimize the amount of transmitted energy outside of their assigned frequencies; (2) receivers should be designed to mitigate interference from emissions outside of their service’s assigned frequencies and channels; and (3) radio systems should use good engineering practices to mitigate degradation from interference.

What this tells us is that the FCC is going to start looking at your radios and your system design when you have an interference problem, and your system ought to be “up to snuff” if you wish to be protected (or even if you’re the one causing).

While this is a policy document, and not new rules (yet), it is a significant paradigm shift, one to which wireless operators should pay much attention.  At the recent Annual Meeting of the National Wireless Communications Council (“NWCC”, the successor to the Land Mobile Communications Council a/k/a LMCC) of which we (the Government Wireless Technology & Communications Association or GWTCA) are a member, I asked Ira Keltz of the FCC’s Office of Engineering and Technology whether the FCC recognized that land mobile operators needed time to adapt their systems to this new responsibility, with equipment often being used for twenty years or more, and the significant costs that would entail.  He said that the FCC was well aware of these factors.  But be aware that while legacy Part 90 systems may still have a little runway left before interference and sharing decisions directly impact system operations and design, that runway isn’t endless.  And the sooner that system operators review their equipment and designs, and start make plans for the next stage, the better.

Public Notice:

Policy Statement (Original Draft):

The EV East Coast Road Trip – February 2023

I needed to travel from my home in Delaware to a Board Meeting for a new EV Charger Company near Daytona Beach, Florida. I had booked my flights out of Baltimore-Washington International Airport to Orlando, Florida, and was all set to go. In thinking about my trip, and realizing that I was in no rush to get back home, it occurred to me that I should head over to Tampa, Florida after the meeting and see two different groups of friends that I hadn’t seen since before Covid. Thus, I booked my return flight out of Tampa.

No doubt you’ve heard about the recent airline issues – cancelled flights, crazy people on flights, etc. It also occurred to me that there were a number of family and friends in between Delaware and Florida that I hadn’t seen in years, and I should. So, I cancelled my flights, and decided to take a road trip to Florida and back (alone).

My trip was with my 2022 Tesla X, with an estimated 330 miles of range, in decent weather. This is my second Tesla X, as I had a 2016 for 4 1/2 year, before trading it in. Since I was doing this trip in February, I knew that my range would be a bit reduced on the northern part of the trip, and better in the southern part.

The first thing that I noticed in my trip planning that was that there is no trip planning software that was totally helpful for this kind of trip. It’s not just a function of finding chargers along the way, there were so many Tesla Superchargers enroute that I merely had to decide how long I would go without a rest stop. However, none of the programs out there accounted for using hotel destination chargers for overnight charging. In other words, they couldn’t account for me arriving with (for example) arriving at a hotel with a 20% charge, and leaving in the morning with a 90% charge. One program, www.abetterrouteplanner.com, came closest, enabling me to change my departure time at a time, and being able to adjust my arrival charge state (but not my departure charge state). It has an adjustment to do either more stops with shorter charging time, or fewer stops with longer charging time. I chose fewer/longer stops, because I like to take a nap while my car is charging (although my Tesla is outfitted so that I could watch Netflix, Disney, etc., or play games). Basically, I was stopping every 2 to 2 1/2 hours, which was perfect for hygiene stops.

Once I figured out the best route to see my friends (I-95 on the way down, I-85 on the way back), I was pleased to find that even in the non-interstate portions of my trip did not cause any charger location issues. In fact, the only charger issue that I had was at a Tesla Supercharger at a police station that was giving me fluctuating charging number. So I went another 10 miles along my route to another Supercharger. Another Supercharger in Atlanta was full when I arrived, but a spot cleared about a minute later. Of course, since I was only using Tesla Superchargers, I can’t speak to the experience with non-Tesla chargers.

My experience thus far with destination chargers (those at hotels), has been mixed. A couple of months ago, I arrived at the hotel that I picked because of it having such chargers, and found one spot occupied by a charging EV, another occupied by a non-EV, and the final remaining spot blocked by a car in an adjacent spot that could stay within it’s white lines. On my road trip, at one hotel it was no problem, but at the second three of the five chargers were not functioning. Clearly, if we’re to encourage such use, hotels must be more diligent.

The car experience itself was excellent on the highway. Not having to keep my foot on the accelerator or brake allowed me to arrive at each location feeling decently, and not dragging. There were a few times when the car slowed down for emergency lights in various locales, but nothing significant.

On the other hand, the Full-Service Beta was a bit glitchy. It has trouble distinguishing between yellow blinking lights at intersections, thinking that they’re either emergency lights or perhaps traffic lights about to turn red. Near my home, it had trouble at one intersection, getting into the left turn lane when the GPS was clearly showing it was time for a right turn. Once it figured out it was wrong, it just stopped in that left turn lane. I didn’t give it a chance to see what it would do next. Similarly, on a street near my home, it for some reason followed the car ahead and made a right turn, even though the GPS showed it was supposed to go straight forward. Finally, “creeping out” at a four-way stop sign to see traffic from either side just took too long.

On the plus side, it was great at stop lights, etc. Most impressively, however, I was in the left lane of a four-lane route at night, with a median, when the car came to a rather abrupt stop. At first, I didn’t know why. But the car had seen a person in all black clothing on a dark bicycle in the asphalt part of the median, who was riding. The car clearly thought that this person was going to cross in front of me. I would have thought so, too, but I never saw them in the dark. Score one for the car over the human.

In sum, it was a great trip in the EV. Chargers were fast and plentiful, although hotels must improve. Battery life was as expected, and the comfort of the drive was outstanding. Someone needs to create a route planning app that is more flexible and adjustable for lengthy trips. But my EV enabled me to see friends and family that I hadn’t seen in years, and I look forward to doing it again!

The FCC’s Draft 4.9 GHz R&O/NPRM


It’s been a pretty crazy two weeks in the public safety communications universe.  In addition to what is presently facing first responders on the streets and in the forests, the FCC has dropped a draft Sixth Report & Order and Seventh Further Notice of Proposed Rulemaking in the 4.9 GHz proceeding.  It has caused a lot of talk and discussion in the industry, much of it confusing.

Continue reading “The FCC’s Draft 4.9 GHz R&O/NPRM”

We’ve Seen This Interference Movie Before


Science projects can be so much fun. We all remember the science fairs when we were in school with volcanos, homemade playdoh, and a million other things. Science projects are also so important to life. Marie Curie, Jonas Salk and hopefully someone developing a COVID-19 vaccine soon come to mind.

However, public-safety communications should not be a science project. Mistakes in this instance can prove costly. If risks are to be taken, they shouldn’t be taken without adequate testing.

Unfortunately, that’s exactly what the FCC has permitted in its decision to allow unlicensed devices to share the 6 GHz band with public-safety and critical infrastructure industries (CII) microwave systems. By permitting such sharing without first demonstrating that co-existence can work in the field, there is a dangerous risk that this science project can have disastrous consequences.

Continue reading “We’ve Seen This Interference Movie Before”

Tips For Using Third Party Application Preparers


Lately, we’ve been asked by a number of long-term clients to take over their application preparation process.  The clients have been enterprise users, municipalities and two-way radio dealers.  This is nothing new for us, our licensing staff has taken over this responsibility for entities big and small for many, many years.

What is “new” now is that many FCC land mobile radio-familiar employees are retiring, and entities have been reluctant to replace them.  Even when they are replaced, the new folks can be terribly lost in this highly esoteric area, with huge consequences for simple errors.  Further, the pandemic shutdown has resulted in the loss of some personnel, placing additional strain on this process.  While I wrote about this in 2017, it seems like an appropriate time to revisit the issue.

If you are in a similar situation, due care should be taken with regard to your chosen entity, whether it is a law firm, a third-party application preparation service or even a Part 90 Frequency Advisory Committee (FAC).  Sometimes, the “cheapest” option is the most expensive option at the end of the day.  Thus, there are a series of questions that should be asked before selecting an entity to perform this function. Continue reading “Tips For Using Third Party Application Preparers”

The Citizens Broadband Radio Service – An Overview

view of vintage camera

Photo by Karol D on Pexels.com

The Citizens Broadband Radio Service (CBRS), is a spectrum sharing plan that provides a more efficient alternative to the traditional methods of allocating spectrum. In April 2016, the FCC finalized rules for spectrum sharing, authorizing 150 MHz of new spectrum – originally used by the Navy and other Department of Defense personnel – for commercial uses on a shared basis with the incumbent users of the spectrum. Continue reading “The Citizens Broadband Radio Service – An Overview”

Carpenter v. U.S. – Implications For Smart Cities

time lapse photography of city road at nighttime

Photo by zhang kaiyv on Pexels.com

The Supreme Court’s decision on the privacy of cell phone records in Carpenter v. United States, and the need for law enforcement to obtain a warrant, could have implications for the future of smart, connected cities.

The smart building of the future contains a variety of sensors, from heat and motion sensors that detect how many people are in a room, to metal detectors for hotels.  Outside of the building, cities are putting sensors in the street for Dedicated Short Range Communications (DSRC), which will connect vehicles to infrastructure to avoid accidents (and more).  These are just a few of the connected environment sensors that is part of our near future.  IoT devices already outnumber the world’s population.  Here’s a nice presentation from Bosch on just some of what a connected city will enable.

These smart city/smart building technologies will be tied back to databases which represent a treasure trove of information for city/building planners, energy providers and…….. law enforcement.

Where does this data reside?  Does it reside with the municipality (for DSCR, traffic cameras, etc.), with the building owner, or with Google (who has your mapping information)?  Can a third party purchase that information from the municipality for data analytics (perhaps Facebook)?  Can law enforcement access this information, and under what non-emergency conditions?  If law enforcement is provided such access, how do we ensure the chain of custody of that data?

Should a building owner be required to provide building information, and if the owner does so without a warrant, should the building owner be required to provide you with affirmative notice when you enter?  Can you opt-out of providing this information to the building owner?

These questions have consequences for the First Responder Network Authority (FirstNet).  FirstNet is designed to be a nationwide broadband system for police and fire fighters.  One of the most powerful uses of the network is to give first responders the ability to harness the power of IoT in order to enable better information upon which to act in emergencies.  For example, access to internal video cameras at the Washington Navy Yard would have enabled police on the outside of the building to know the location and number of shooter(s) inside the building during the incident in 2013.  If the building was a private facility, instead of a government facility, does accessing inside building IoT represent a unreasonable search and seizure?

As a participant in the Telecommunications Industries Association’s (TIA) Smart Buildings Program, I see opportunities to create simply amazing technologically advanced buildings that resemble the best of Star Trek.

I do not suggest or recommend any answers to these questions here.  However, it is a conversation that must be had as a society, and considered prior to the issue arising in a litigation context.  Part of that discussion will be shaped by the Carpenter decision, which certainly would seem to suggest that access to many of the potential data users discussed above will require a warrant.

Connectivity and analytics of shared information is an important part of creating a more efficient future and limiting the use of our planet’s scarce natural resources, with the hope of making a better world for all.  How that future isn’t considered to be a “Big Brother” future is a conversation to have now.

800 MHz Post-Rebanding Interference – What You Need To Know


On November 6, 2017, the FCC held an Open Forum on Interference from broadband systems to public safety land mobile radio operations.  We were honored to have been asked to participate.

During the session, we were asked about our efforts to provide education to the public safety community about the issue.  We told the FCC about our half day interference workshops at the International Wireless Communications Expo (which we’ve done multiple times), presentations at numerous APCO meetings, and magazine articles.  The Commission urged us to keep getting the word out, and so this is the purpose of this blog post. Continue reading “800 MHz Post-Rebanding Interference – What You Need To Know”

The Elimination Of Net Neutrality Must Protect Public Safety


A Fact Sheet was recently issued by Democratic FCC Commissioner Clyburn on the FCC’s proposal to eliminate Net Neutrality.  As noted by the Commissioner, the Rules sought to be repealed were previously upheld as reasonable regulation by the U.S. Court of Appeals.
You may wish to read the Fact Sheet in conjunction with Last Week Tonight’s Story by John Oliver from a couple of years ago.  You might want to move to the 2:30 point of the video to skip the setup jokes.
There are significant questions as to how the elimination of these rules impact public safety communications.  It was originally argued that Net Neutrality would keep carriers from being able to offer public safety preemptive service.  That apparent hurdle was overcome, as can be seen by AT&T’s FirstNet offering as well as Verizon’s competing offering.
It has also been suggested by a former FCC attorney that the absence of Net Neutrality would have a negative impact on public safety.
Public Safety is increasingly dependent upon IP connected services, from transmitter sites with IP-based interoperability, to IoT security, to backhaul and controls, to VOIP E911 calls.
Regardless of which Net Neutrality position you believe in, what is important is that if the FCC continues on its apparent course to “free” providers of their current responsibilities, the final rules must include provisions that specifically preclude the ability of providers to give a reduced prioritization to public safety traffic (or to make them pay more), regardless of whether such traffic is FirstNet related.

Mandatory 6.25 kHz VHF/UHF Narrowbanding? Not Soon!


A recent FCC decision resulted in some riled up members of the Part 90 land mobile radio community.  Specifically, on July 30 the FCC denied a Waiver Request submitted by the International Municipal Signal Association (IMSA).   IMSA had requested that the FCC waive the requirement that Part 90 VHF & UHF radio manufacturers include a 6.25 kHz bandwidth mode (or equivalent efficiency) into newly type-accepted products. Continue reading “Mandatory 6.25 kHz VHF/UHF Narrowbanding? Not Soon!”