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What is C Band 5G?


There's a whole new kind of 5G being launched and talked about in the US in 2022: C Band. It's much faster than existing "nationwide" 5G, yet has better coverage than hard-to-find mmWave 5G. For AT&T and Verizon, it represents a huge leap forward in the 5G race. For their customers, it will mean the first time many of them will experience a significant difference between 4G and 5G. So what is C Band? Is it just hype or something to actually get excited about? Is "C Band" the best term for this? Where did this band come from? Does it pose a danger to planes? And where does T-Mobile fit into all this? We answer all those questions and more in this in-depth guide to everything C-Band.


Branding


To even talk about C Band, we have to translate the carrier branding around this new 5G service. All major US carriers have come up with their own brand for their faster flavor of 5G. AT&T calls it "5G+". Verizon calls it "Ultra Wideband", sometimes abbreviated "UW".

T-Mobile's equivalent brand is "Ultra Capacity" or "UC". It's technically not C Band, and not new, but it does include mid-band, which — as we'll explain further down — means it's roughly equivalent to C Band and should be part of the same discussion.


All three brands are a bit tricky because they include both C Band / mid-band and mmWave. mmWave is a very different frequency range with very different characteristics. But in most cases going forward, if you get noticeably faster 5G, it's probably going to be C Band / mid-band, because it has such broader coverage compared to mmWave.


Radio Frequency Bands


First of all, C Band is — as the name might imply — just a radio frequency band. It may seem like a whole new 5G technology since the speeds and coverage can be so different from the 5G you may be used to. But it's just the same 5G tech in a new set of radio frequencies.


Different radio frequencies have different characteristics due to basic physics. Low frequencies are inherently great for coverage (extending vast distances and through walls, etc.) but have limited ability to carry data at high speeds. High frequencies are the opposite: they don't reach as far, but are great for high-speed data.


Before 2022, AT&T and Verizon only offered 5G in two flavors: low-band and mmWave.

Low-band 5G offers "nationwide" coverage, but data speeds only slightly better than 4G. There are three reasons the data speeds of low-band 5G haven't been very impressive:

  1. Low-band 5G uses the same exact frequency bands that have been used for 4G (and 3G, and even 2G), so physics applies the same basic constraints on capacity to carry data.

  2. Since it's using the same bands, 5G technology must share those bands with 4G, a situation that's generally not ideal with most radio technologies.

  3. 5G isn't a radically new technology compared to 4G. It's better, more modern, and a necessary step forward technologically... but 5G is heavily based on 4G; you could think of it more like 4.5 G.

Then there's mmWave 5G, which is very fast. However, it operates at so much higher of a frequency range that it has trouble reaching very far or going through walls (or sometimes even windows). It's great for stadiums, arenas, train stations, and certain downtown areas of major cities, but it's not practical for anything approaching broad coverage.

Very high frequencies are only part of the reason mmWave can offer such fast data speeds; there are two other key reasons. First, the mmWave bands are dedicated to 5G and not shared with 4G.


Second, the mmWave bands are very large in terms of bandwidth. This refers to the difference between the upper and lower bounds of the band. A wider band can be thought of like a larger "pipe" that can carry more data.


C Band combines the best of both low-band and mmWave. The frequencies are closer to low-band than they are to mmWave, so coverage is more like low-band. But the frequencies are higher than low-band, and so a bit better-suited to fast data.


But more importantly than the frequency, C Band is a wide band, that is exclusive to 5G. That means a lot of capacity for very fast data, which is why it's such a big deal. For example, Verizon says customers should expect speeds up to 10 times faster compared to 4G.


Mid-Band


C Band is actually better referred to as "mid-band", a broader term that also includes T-Mobile's band 41. C Band is a higher frequency than band 41, but it's close enough in frequency, bandwidth (both are very wide), and 5G implementation to be in the same category. C Band and band 41 also share most of the same differences compared to other bands, so it makes a lot of sense to think of them together as the "mid-band" category.


Another reason "C Band" isn't an ideal term is that the FCC has also just auctioned off a key band just below C Band that may effectively merge with C Band to be part of the same band (band 77) when those frequencies are deployed for 5G networks over the next 2–3 years.


(Also, there isn't global consensus on the boundaries of the C Band. The US FCC defines it as 3.7 – 4.2 GHz, while the rest of the world defines it as 4.0 GHz – 8.0 GHz.)


While "C Band" is in the news today, it's actually a legacy term that makes more sense in the context of the satellite industry, the original owner of these frequencies. It's not the best term to use going forward when talking about 5G. That's why we'll mostly stick to "mid-band" for the remainder of this article.


Sub-6 and Other Terms


If you've heard the term "sub-6", that's a slightly shorter way of saying sub-6-GHz, which simply means all frequency bands below 6 GHz. Therefore sub-6 includes both low-band and mid-band. It's essentially another way of saying "not mmWave". When a company needs to convey that a phone doesn't support mmWave, it sounds better to say "supports sub-6 5G" instead of the negative.


That doesn't necessarily mean that "supports sub-6 5G" means a phone supports mid-band; many older 5G phones do not.


The C Band is also sometimes referred to as the 3.7 GHz band, and the two bands just below it are sometimes referred to as the 3.45 and 3.5 GHz bands.


The 3.45 GHz band was just auctioned off by the FCC. AT&T and Dish bought a ton of it, covering the whole lower 48. T-Mobile bought some, as well. We can expect these companies (especially AT&T) to launch 5G in this band in the next year or two, expanding their mid-band 5G service beyond bands like C Band and band 41.


This 3.5 GHz band is also called CBRS, and it's already been deployed by Verizon using 4G LTE technology. For this, they use band 48, which is a subset of band 77. So if you're with Verizon, you may already be using mid-band if your phone supports LTE 48, it's just not 5G. But according to Verizon, "there are plans to use CBRS spectrum for 5G." This would further expand Verizon's mid-band 5G network beyond C Band.


All of these together (C Band, 3.45 Ghz, and CBRS) are part of the larger band 77, which itself is sometimes referred to as the 3.5 GHz band (because that's roughly where it starts) or the 3.7 GHz band (since 3.7 GHz is close to its center).


Band 77


As I mentioned above, what matters isn't so much "C Band" but "mid-band", and all you really need to know about mid-band if you're with Verizon or AT&T is band 77. This is the international designation for the single frequency band that covers C Band and the related bands just below it (3.45 GHz and CBRS), as they relate to 5G networks. In other words, band 77 includes all of the frequencies used for most new mid-band 5G launches in the US in 2022 – 2024.


(In other parts of the world, band 78 covers similar frequencies.)


As I mentioned, with T-Mobile, mid-band means band 41... for now. Band 41 is separate from band 77, but band 77 will also apply to T-Mobile soon. T-Mobile also participated in the FCC's recent mid-band auctions and plans to deploy 5G in band 77 around the end of 2023 (or potentially even sooner in the 3.45 GHz band), adding even more mid-band bandwidth to their 5G network.


Phone Compatibility


If a phone supports band 77 — also referred to in phone specs as n77, 5G 77, or NR 77 — then it should support these new, faster C Band 5G networks being launched now by Verizon and AT&T (and later on, T-Mobile).


Band 77 support in phones should also cover the new 3.45 GHz band that was just auctioned off by the FCC, to be deployed in the next few years by AT&T and probably T-Mobile. And when Verizon deploys 5G in the CBRS (3.5 GHz) band, phones with band 77 should support that as well. These future deployments should add even more mid-band spectrum to 5G networks, improving capacity and speed further still.


You can check which specific phones support which bands, including band 77, by looking up phone specs here on Phone Scoop. Generally, phones started supporting band 77 in late 2020, and most new 5G phones released by AT&T and Verizon in 2021 already support band 77. (The only exceptions are some of the very cheapest models, like the AT&T Radiant Max.) We expect essentially all new 5G phones for these carriers in 2022 to support band 77.


(Compare this to mmWave, which — unlike mid-band — adds not-insignificant cost to a phone. That's why not all 5G phones support mmWave, and we expect that to continue to be the case in 2022.)


If you're with T-Mobile, you may want a phone that supports band 77 starting in December 2023. So if you're shopping now for a phone that you plan to keep for two or more years, keep that in mind.


Launch & Expansion Plans


As of December 2021, the FCC is allowing AT&T and Verizon to launch C Band 5G in 46 of the top 50 metro areas in the US. By agreement with the FAA, the actual launch date will be on or around January 19th, 2022. Washington DC, Baltimore, Atlanta, Denver, and most rural areas aren't included in this phase. Those areas will have to wait until December 2023 for C Band, although 5G could launch in other mid-band frequencies (that are part of band 77) before then.


Verizon has announced that its new mid-band 5G network will cover 100 million people at launch, and plans to expand that to 175 million over the next two years. After December 2023, Verizon plans to expand this coverage to 250 million people in 2024.


AT&T isn't as detailed with its initial launch plans, but we do expect them to launch this month alongside Verizon. What they will say is that they promise to have a mid-band footprint of "200 million by the end of [2023]". They also "plan to deploy more C-Band than anyone else in the U.S. by the end of 2023." So it's clear they intend to keep up (or perhaps catch up) in the mid-band 5G race over the next two years.


T-Mobile has offered mid-band service for some time. They recently announced that their mid-band 5G now covers 200 million people, and should cover 250 million by the end of 2022. It's too early to say what their C Band deployment will look like around the end of 2023, but they already lead in mid-band 5G, and C Band can only make it better.

It's also too early to say exactly when AT&T (and perhaps T-Mobile) will deploy 5G in the new 3.45 GHz band. It could be before the end of 2022, or it could take a little longer.


Summary


Forget the term "C Band". "Mid-band" is the term you should pay attention to. For most people, mid-band 5G means faster 5G with broader coverage. If you expected 5G to be faster, this is when it might finally meet those expectations.