FCC regulation on UWB

As per FCC regulation an outdoor UWB network must operate without a fixed infrastructure. Meaning you couldn’t permanently mount UWB transceivers in fixed positions outdoors to set up an RTLS system for an open field. Does this mean that I cannot use Decawave anchors and tags outdoors? I am planning to use Decawave for train localization.

Any clarification on this by the Decawave team would be highly appreciated.

See this site for some details on the FCC regulations - https://www.law.cornell.edu/cfr/text/47/part-15
DWM1001 FCC Grant was under 15.250 rules

To address your question, Tx outdoors is not allowed from ‘fixed’ infrastructure

Thank you for your response.

So, If I place an anchor at a fixed location and a tag on the vehicle to be tracked, will the anchor count as a fixed infrastructure?

I am not an expert on the topic. But the FCC may provide a waiver for some circumstances.

See the following article -

You will not find a clear and authoritative interpretation from the FCC on what is “fixed outdoor infrastructure” as stated in 47 CFR 15.250(c).

All three words are subject to interpretation.

Let’s handle “infrastructure” first.

When the FCC put the 15.250 rules in place in the 1990s, there were hearings and discussion on the proposed rules which were aimed at making sure UWB did not proliferate in a way to damage the incumbent spectrum holders, the so called “anti proliferation rules”. Basically, how can we limit UWB so that there aren’t too many of them that would raise the noise floor on existing narrow band systems using the overlaid frequencies. Hence no toys, no flying things, and no “outdoor fixed infrastructure”.

The basic thing the FCC seemed to be worried about was using UWB for cellular towers, that is, creating “wide area communications systems” from UWB. Basically, the FCC didn’t want the cell phone networks using UWB to provide cell phone services, thus bypassing the lucrative spectrum auctions and also impacting the incumbent spectrum holders with a severely raised noise floor. Those concerns seem silly now given the short range and lower power of UWB, but at the time, it was a concern. We have to remember those were the days of cell phone explosion and spectrum was a super hot commodity.

iRobot applied for a waiver to these rules, and the FCC agreed to their request, and here is the order:

The key phrase is on page 3, paragraph 6:

The underlying purpose of Section 15.250(c) is “to prevent the establishment of wide area communications systems” in the 5925-7250 MHz frequency band.

With that statement, the FCC is laying the basis for what systems will be allowed and what will not. In granting the iRobot waiver, the FCC basically said that as long as you aren’t creating a wide area communications system, you are okay. So “infrastructure” really means a system involving more than one entity and spread over a wide area. That does not describe a system installed and used by one entity entirely on one site, as is typical for most UWB RTLS systems.

I don’t believe iRobot needed a waiver to do what they did (stakes in the ground with UWB beacons on them) since they were not building infrastructure, and said so in my comments to the FCC on the issue. And I still believe that is the case, especially now that the iRobot decision so clearly defines the purpose of 47 CFR 15.250(c).

What is “fixed”?

The FCC has no definition of this that I can find and you can make arguments in many ways about what it means.

Some take this to mean the UWB nodes don’t move in operation. That seems overly restrictive to me as lots of tagged objects, say material sitting on a pallet outdoors, doesn’t move hardly at all.

One could get around that definition by making a mount that moves, say a servo that swings an anchor in an arc and you use the servo position to dynamically update the node survey location. Don’t laugh, this is a possible treatment for the rule.

Another view might be that the nodes are bolted or anchored to immovable structure, and indeed the 47 CFR 15.250(c) rule says:

A fixed infrastructure includes antennas mounted on outdoor structures, e.g., antennas mounted on the outside of a building or on a telephone pole.

Again, in the context of cellular networks, this is where cell antennas were typically mounted.

Another way to look at it might be if the node is removable without special effort, say removable without tools. Maybe that isn’t “fixed”?

So I don’t have a very useful definition of “fixed” as the FCC would define it. It is best to rely on the “infrastructure” aspect of the rule if at all possible.

Lastly, what is “outdoor”?

You’d think this would be obvious, but it isn’t. We do a lot of work in large stadiums, so consider a stadium with a roof that can be closed or open. Is that outdoors when the roof is open? Wouldn’t that make any house “outdoors” if a door or window was open?

What about a stadium with a hole in it (like the old Dallas stadium, the “bowl with a hole”). Just how closed does the stadium have to be for it to be “indoors”?

What about a screen porch, or an overhang, or any the other things that are kind of indoors and outdoors at the same time?

What about a building under construction before the roof is put on?

In most cases, what is outdoors and indoors is relatively easy to tell, but there are gray areas.

In conclusion, there is a lot of debate about what constitutes “fixed outdoor infrastructure”. I have clients operating outdoor UWB system that are FCC certified under 47 CFR 15.250, primarily in sporting applications, and they don’t have a waiver and they don’t think they need one. I tend to agree on the basis they can clearly show they aren’t building a wide area communications system per the waiver statement from iRobot. But this is an interpretation and no one, not me or Decawave, can positively tell you what the FCC is thinking today, or what they will think tomorrow.

I hope that this gets clarified in the future, that 47 CFR 15.250 gets changed to be more enabling and less confusing.

For ETSI (Europe), the rules are different and less ambiguous and less permissive. But that’s a story for another day. UWB is, unfortunately, not treated uniformly throughout the world which can make one use case allowed in one country, and not in another. One hopes this improves over time.

Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
+1 812 962 9408


Thank you Mike for a great contribution!

Thank you for such a detailed answer! Much appreciated.

Thank you, really interesting insights

Thank you, Mike. That was quite informative.