A recently passed American spending bill, known as H.R. 1, allocates $24.5 billion for fiscal year 2025 to fund a nationwide integrated air and missile defense system. Although the term isn’t used in the legislation, the new system is referred to as the Golden Dome. There will be higher costs coming in later years. The Department of Defense has already set a target to be able to test the new system by the fall of 2027.

I’ve been reading a lot of speculation that a Golden Dome system will need access to a wide range of spectrum since a defensive system will have to be agile enough to resist jamming and be able to adapt on the fly during enemy attacks.

It looks like the primary spectrum for the system is the 3.1-3.45 GHz spectrum that is already used by the military for radar. The same legislation also directed the FCC and the NTIA to identify 800 megahertz of spectrum for public auction to support “mobile broadband services, fixed broadband services, mobile and fixed broadband services, or a combination thereof.” The legislation specified finding 600 megahertz of spectrum for auction between 1.3 GHz and 10 GHz and excluded spectrum in the 3.1-3.45 GHz and 6 GHz bands.

Interestingly, in November of last year, the Department of Defense suggested it was willing to consider sharing the 3.1-3.45 GHz spectrum with commercial spectrum users. I wonder if that idea is still on the table now that the Golden Dome initiative has been funded.

The most interesting question is where the Department of Defense will look for additional spectrum bands to provide a diverse set of spectrum for air defense. The challenge will be that any spectrum used for air defense must take priority and would likely preempt all other users when the military activates the system.

The FCC began exploring the concept of spectrum sharing with the CBRS spectrum, which created a hierarchical system where the Navy has first use of the spectrum, followed by licensed spectrum holders, and finally unlicensed users. This spectrum is already being used by over 1,000 entities and has become popular because commercial users of the spectrum don’t expect to be shut out of it very often, and perhaps not at all. The hope has been that uses by the Navy can still accommodate other users.

I’ve read speculation that the DoD might want to ‘share’ other bands of spectrum for the Golden Dome that are used or are slated for auction to 5G carriers. This would include a number of possible bands of spectrum between 6 GHz and 15 GHz.

This is pure speculation on my part, but I have to wonder how much the idea of sharing spectrum might affect the FCC’s planned values for spectrum auctions. Does having to share spectrum with the Golden Dome lower the value of the spectrum to cellular carriers? One of the reasons that sharing spectrum with the Navy for CBRS was not seen as too disruptive is that the Navy mostly uses the spectrum in well-defined markets along the coasts. It seems that a Golden Dome system will involve using the spectrum across a much larger part of the country.

Hopefully, the FCC and the military will work out a satisfactory solution to the issue so that the military doesn’t just snatch valuable spectrum. The primary reason I wrote the blog was to highlight the complexity of satisfying every class of users interested in obtaining dedicated access to spectrum. The FCC’s job was a lot easier a decade or two ago, before there were hundreds of new uses for wireless applications—not only terrestrial, but also for the growing constellations of satellites.

The problem the FCC faces is that policy can’t override physics, and there is a defined range of desirable spectrum bands that everybody wants to use. Figuring out how to keep everybody happy while not squelching important uses of spectrum is becoming an increasingly tougher challenge