FCC Moves to Clear C-Band for 5G

2 Mar 2020 • 7 minute read

Last week the FCC approved $9.7B to quickly clear the C-band for 5G. This could be a big deal. It is just the first step, approving the payout. Before I explain why I think this is a big deal, let me explain the story so far. Well, I already have, in several posts:

but especially this one:

5G in US vs Rest-of-World

Radio Spectrum

This big picture is that 5G is transmitted using three radio frequency bands of spectrum. There are some ways of sharing these somewhat, but to a first approximation, if you are using some frequency band for, say, satellite phones then you cannot also use it to provide 5G cellular service. There are three different frequency bands: low-band, mid-band, and mmWave. You will often see the low-band and mid-band grouped together as "sub 6GHz" since that is the top frequency of the mid-band. mmWave is higher-frequency, but we don't say "super 6GHz" since its frequency band is nowhere near there, it starts at 24GHz. The big gap between 6GHz and 24GHz is not used for cellular mobile.

Like the old adage about investing in land since they're not making any more of it, they're not making more spectrum. There is no lower limit on radio spectrum, it is the lowest end of the entire electromagnetic spectrum, although antenna sizes are inversely related to the frequency. The lowest frequency actually used has been under 100Hz requiring antennas tens of kilometers long. These were built to communicate with submerged submarines. This exhibits one point that is important in the 5G debate: low-frequency waves are really good at going through anything (communicate with a submarine underwater, and not just water, but electrically-conducting seawater), but have a really low data rate of a few bytes per minute. It was also one-way, since it's impossible to build a huge antenna on a submarine. At the other end of the spectrum, assuming we are on Earth where we have an atmosphere, high-frequency signals are absorbed by the gases and radio transmission is impossible above about 300GHz, where the limit is a few meters and so essentially useless for practical communication. Above that, from 300GHz to 3THz, you can consider this far-infrared, although it is still microwave in some sense. I don't know if it is useful for transmission in a vacuum. As the tagline for the movie "Alien" said, "in space, nobody can hear you scream"...but maybe you can make very high bandwidth communication by radio.

5G Bands

As I said, there are three different frequency bands involved in 5G. The diagram above, pulled from the entire radio spectrum, covers all the bands we are talking about. I show this mainly to show how complicated the spectrum allocation map is.

Low band. This is the same frequency band as we used for 4G and (mostly) now LTE (and is muddied by some carriers, such as AT&T in the US, calling the more advanced LTE technologies in this band 5G for marketing reasons). There are some gains in efficiency using 5G in these bands versus the older technologies, but not a big increase. This band is already full, and this is the reason sometimes you can't make a call or someone calls you and goes straight to voicemail since there was no channel available to connect your phone to a basestation. But, like the submarine systems I discussed earlier, signals these frequencies can go through walls, car windows, trees, and so on. That's why your current phone works most of the time. In places where it doesn't, such as subway tunnels, often additional base stations are added to provide coverage in stations, and sometimes everywhere in the tunnels.

Mid-band: This is new spectrum that most of the world has allocated, and in most cases auctioned, for 5G. This is the C-band in the title. The US has not auctioned spectrum here since it is already in use, mostly by the government and military. If you have read my earlier posts, you will know that experts generally consider this band essential for effective deployment of 5G. We need more spectrum that can penetrate buildings and vehicles. The low-band is full ("they are not making any more of it") and mmWave cannot go through walls or glass (see more on this below).

mmWave: The problem with mmWave is that it doesn't go through much. Walls and windows, for a start. But it won't go through your hand, the leaves of a tree, or rain. Or even much air. Theoretically, it should go through about 1,000ft (300m) of air, but the last I read is that in the trials they were getting more like 300ft (100m). It is an oversimplification, but mmWave can provide coverage outdoor, or indoor, but not outdoor-to-indoor. On the upside, there is an enormous amount of bandwidth above 25GHz so you can get really high transmission speeds. Personally, I don't understand all this focus on transmission speed in the marketing of 5G—once you can play a 4K movie on your phone, how much more bandwidth can you use?

The FCC Vote Last Week

My post 5G in 2020 covered an interview with Federal Communications Commission (FCC) Chairman Ajit Pai at CES, mostly on just this spectrum issue. One paragraph from that post:

Pai said that it is crucial to get incumbent users, including the government itself, to share the spectrum. He was asked what Congress could do and suggested 'more clarity about spectrum policy'. He has got pushback on proposals to free up spectrum in the C-band, the 5.9GHz band, and the 6GHz band. It is not just the government, in some of these bands there are broadcasters, utility companies, car companies, and more.

So what has the FCC done? It voted to approve a payment package to incumbent users of the 3.7GHz to 3.98GHz band, offering satellite companies nearly $10B to clear 280MHz of spectrum so it can be auctioned off to 5G carriers. If all goes well, the C-band auctions should begin in late 2020 and early 2021.

The approach is controversial, in the sense that it was a vote along party lines. At this stage, there is no guarantee that the satellite companies involved will accept the payment. Other people, however, consider the payments a windfall for them and, further, is a moral hazard. As one of the Commissioners, Geoffrey Starks, who voted against the plan said:

Today’s order will only encourage demands for similar treatment from similarly situated incumbents, at the expense of both competition and the American taxpayer.

I think this is simply an unrealistic position to take. Spectrum has huge value, which is why we auction it off for billions of dollars. If you want someone to give up spectrum they already have, you have to pay the price. If the satellite companies take the deal and the 5G companies pay more than $10B for the spectrum, then the American taxpayer is actually making a profit on the deal. The fact that these satellite operators got their spectrum in an era when they didn't have to pay for it and the government simply "allocated" it to them doesn't reflect modern realities. They are not going to give it back for the price they paid, any more than a homesteader who got 160 acres in the 19th century for free.

US vs Rest of the World

I ran across a joke last week that has more than a grain of truth in it:

China: We'll bring the hardware
US: We'll bring the software
Europe: We'll bring the regulation

But in 5G, the US is falling behind all the advanced mobile markets in the rest of the world. So I think this vote is great news.

The US risked having a second-rate 5G system. It still does since a lot has to happen going forward, getting this spectrum free is just a start. The government can, in principle, clear much of the spectrum that it "uses" itself. I put "uses" in quotes since a lot of it is apparently unused. Naval radar is used at sea, and not in downtown Chicago. Some spectrum is completely unused, but whoever it is allocated to is still not going to give it up without a fight. We also have the WiFi experience, that spectrum sharing is a lot more effective than anyone expected. The original WiFi took a frequency range polluted with things like garage-door controllers and microwave ovens, and created a free but valuable resource literally out of thin air.

I first read about this vote last week in VentureBeat's report. They agree with the basic premise of this post and point out that the vote:

Could significantly bolster 5G’s growth in the United States, as large channels of mid band spectrum provide carriers with a great compromise between transmitting distance and bandwidth. International 5G deployments on similar frequencies have already seen multi-Gbps speeds comparable to millimeter wave 5G, while most U.S. carriers have had to choose between slow but long-reaching low band frequencies or fast but short-distance high band alternatives.

That's a great summary. And my PSA, again, is - don't rush to buy a 5G phone yet.

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