5G rollout: Why C-Band matters so much

Now that the first C-Band deployments are finally going live in the US, we take a look at the technology's potential to solve issues that have been slowing carriers' 5G rollouts and consumers' 5G connections for years.
Written by Michael Gariffo, Staff Writer

After all regulatory wrangling, aviation industry panic, and last-minute delays, C-Band spectrum is finally live on AT&T and Verizon's carrier networks in the US. At this point, you might be so overwhelmed by the coverage surrounding potential dangers that you've forgotten what the technology might offer you and other smartphones owners across the country. Let us provide a little enlightenment by explaining the current 5G landscape and showing you exactly why C-Band is so important. 

The flavors of 5G

The carrier frequencies that power 5G and earlier mobile networks can generally be divided into three categories: 

  • Low-band: Anything under 1GHz.

  • Mid-band: Everything between 1GHz and 6GHz. This range is where C-Band lives (3.7GHz to 3.98GHz in the US). 

  • High-Band: Everything above 6GHz, including mmWave signals, which operate between 30GHz and 300GHz. 

5G services currently offered by T-Mobile, AT&T, and Verizon Wireless operate across all three of these categories, although only T-Mobile uses any low-band 5G frequencies (600MHz, specifically). 

Why so many bands?

Wireless signal frequencies have different characteristics depending on how low or high they land on the spectrum. 

Generally speaking, the lower the frequency, the further the signal can travel from its cell tower, and the better it is at penetrating buildings. This is especially important in rural settings with widely spaced towers, and urban ones where cellphones are often deep within reinforced concrete buildings. The trade-off is that the lower the frequency gets, the lower the data transmission speed it can generally provide.

On the opposite end of the spectrum, high-band frequencies, especially mmWave bands, are excellent at providing screaming-fast speeds, but terrible at reaching very far or penetrating buildings. This is because the ultra-fast signal oscillations of high-band transmission are extremely prone to being degraded by passing through just a few hundred feet of open air, or a single concrete wall.

How has each carrier dealt with these limitations? 

Each of the "Big Three" US carriers have historically handled the limitations and trade-offs of low, mid, and high-band 5G frequencies differently. 

SEE: Why is my 5G so slow? Comparing the hype to the reality


Verizon's solution revolved around deploying very fast, but very geographically limited, 5G service areas. While its speeds could easily exceed 1Gbps under ideal circumstances, those rates were generally only available within a couple of city blocks of a mmWave tower, assuming an unobstructed line of sight. This resulted in it blowing past T-Mobile in certain regional speed tests, while lagging far behind nationally due to the majority of its nationwide 5G being powered by what are essentially multiple 4G LTE connections combined into a single data stream.

Verizon actually acknowledges on its own coverage map that its "Nationwide 5G" service "runs alongside Verizon 4G LTE, with similar performance." Essentially, it's 5G that runs like 4G LTE because it is 4G LTE in all but name. Most connections of this type would be lucky to exceed 50Mbps in real-world conditions. 


T-Mobile's 5G network is, according to nearly all measurements, the most widely available in the US. This is due, in large part, to its choice to rely on far-reaching low (600MHz) and mid-band (2.5GHz) spectrum. The 600MHz portion was its own construction, while the 2.5GHz components were originally acquired as part of its purchase of Sprint. Since both frequencies offer excellent reach and penetration, and 2.5GHz can be used to push an impressive amount of data, T-Mobile can provide average, nationwide speeds of 150Mbps. 


Like Verizon, AT&T offers mmWave 5G services. As you'd expect, these services are very fast and very limited in range. The company also utilizes 850MHz connections, which exist on the slower, but further reaching end of the spectrum. Unfortunately, this combination of low-band and high-band deployments has left it unable to provide the ubiquitous mix of reach and speed that T-Mobile has accomplished via mid-band deployments, resulting in it placing third in many recent 5G tests. 

So how does C-Band compare?

C-Band is seen by a lot of analysts as the ultimate "sweet spot" for wireless spectrum. It can provide an ideal balance of range, penetration, and transmission speeds. Early testing by our sister site CNET showed that those speeds on Verizon's network can reach as high as 1.4Gbps when standing directly below a tower, with a more realistic 400Mbps being easily accomplished across an impressively wide geographic area. Illustrating the versatility of C-Band, CNET was also able to get a still-respectable 90Mbps, even when deep within an underground parking structure. 

AT&T's much more modest initial rollout has received similar, albeit sparser praise, due to its inclusion of far fewer markets. 

T-Mobile, of course, knows it will need to deal with C-Band competition. While its exact plans remain somewhat hazy, its mid-band 2.5GHz deployments are close enough to C-Band's range that they already offer many of the same benefits. CNET found that T-Mobile's established network can already provide a very similar 400Mbps in the same densely covered urban locations as Verizon's new C-Band offering, while its slightly lower frequency pushed an even-more-impressive 100Mbps in that same underground parking garage scenario. 

What's next?

While the fate of C-Band deployments near airports in the US remains somewhat hazy, it is once again on the table thanks to an agreement between the Federal Aviation Administration, AT&T, and Verizon Wireless. Exactly which airports will receive approval and how wide those service areas will be remains to be seen. 

In the mean time, expect C-Band 5G to be proliferating across the rest of the country like wildfire. Verizon has already massively expanded its own true 5G holdings with its initial launch, while AT&T has similar, if somewhat slower, designs. T-Mobile, meanwhile, will likely continue expanding and exploiting its current 2.5GHz network to maintain its own bid for 5G leadership.

Ultimately, the big winners here will be the consumers. As a whole new leg of the wireless network arms race begins to heat up, C-Band will be the first taste many Americans get of the promised 5G speeds we've been hearing about for so many years.

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