What is mid-range 5G? C band explained

You may have noticed that the rollout of 5G has been much more complicated than previous advancements in cellular technology. Certainly, back in the days of 3G and 4G/LTE rollouts, we didn’t hear terms like “midband,” “C-band,” “millimeter wave,” and “sub-6 GHz.”

Of course, these technologies did not promise to revolutionize wireless communications in the way that 5G has. It’s fair to say that even the best 4G/LTE service was mostly limited to use by smartphones and tablets. By contrast, 5G is already emerging as a viable substitute for home and business internet services.

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After all, 5G can deliver fast speeds and lower latency that were once the exclusive domain of expensive wired broadband plans. However, with all of this power comes its own set of challenges.

Chief among them is finding the best frequencies for 5G radio signals. The airwaves are no less congested, and carriers and regulators need to figure out where to put those 5G signals so they don’t interfere with anything else.

However, for 5G to deliver on its promise, it must also innovate in radio spectrum, using frequencies that have never carried cellular services before.

The Frequency Tradeoff

There is a direct relationship between frequency, speed and range when working with radio frequencies. Higher frequencies provide more bandwidth, which means faster speeds, but they can’t cover as wide an area. Low frequencies travel much farther and can even penetrate solid objects like walls much more effectively, but they are relatively slow.

You’re probably already familiar with this concept if you’ve ever tried to optimize your home Wi-Fi router. The 2.4 GHz band gives you better range at slower speeds, while the 5 GHz band gives faster speeds at a shorter distance. It’s the same principle with cellular frequencies.

Two tall cellular microwave radio towers against a blue sky.
Kabiur Rahman Riyadh / Unsplash

In your home, this can be solved by moving your Wi-Fi router to a better location or investing in a mesh Wi-Fi system to provide additional coverage. Mobile operators need to do essentially the same thing; using higher frequencies requires them to build more towers.

Now, since we expect 5G to be significantly faster than previous cellular services, it must operate at higher frequencies than older 3G or 4G/LTE services. Although 5G offers some innovations that allow it to make better use of the bandwidth available to it, it is still limited by the laws of physics as to how much data it can hold in a given frequency.

The Battle of the Specter

Of course, cellular signals aren’t the only ones using the airwaves. Even in your home, everything from your Wi-Fi router to your garage door opener operates in the same general radio frequency (RF) spectrum. In the wider world there are amateur radio services, aircraft equipment, marine radios, GPS, weather equipment and much more.

To prevent all of these things from interfering with each other, the US Federal Communications Commission (FCC) regulates which frequencies can be used and who can use them through licensing agreements.

Prior to the arrival of 5G, cellular services had always lived in the 600 MHz to 2,300 MHz (2.3 GHz) zone, mostly concentrated around 800 MHz and 1.9 GHz. Operators acquired licenses for this spectrum from the FCC many years ago, and since new technologies like 3G and 4G/LTE operated in the same range, there was rarely a need to purchase new spectrum.

Everything changed when 5G arrived. While it’s still possible to use 5G on these lower frequencies, it’s not its ideal home. Low-band 5G will only offer incremental performance gains over 4G/LTE for a variety of reasons. To really take advantage of what 5G has to offer, carriers needed to get their hands on high-frequency spectrum.

The middle spectrum

Above the frequencies most commonly used for cellular services is the “mid-band” or “mid-range” spectrum. Although this extends from 1 GHz to 6 GHz, the “5G mid-band” is considered to be in the range of 2.4 GHz to 4 GHz. It is also the sweet spot for 5G. It offers the best balance between performance and autonomy; it can deliver significantly faster speeds than 4G/LTE without requiring operators to deploy hundreds of additional towers.

This is where the “C-band spectrum” we’ve been hearing so much about lately lies. “C-band,” in this case, refers to the 3.7–3.98 GHz spectrum that the FCC auctioned in early 2021.

However, technically speaking, frequencies from 2 to 4 GHz are referred to as part of the “S band”, while the C band is from 4 to 8 GHz. When the FCC went looking for spectrum that could be reallocated for 5G use, they managed to find a chunk of 3.7-4.2 GHz that could be released, and since it’s crossed the C-band territory, it chose to use that name for the entire block of spectrum.

Diagram of the 5G median spectrum used by US carriers.
Jesse Hollington / Digital Trends

The 3.7–4.2 GHz band was originally allocated to the fixed-satellite service (FSS) for data transfer from space to earth stations. Since it was associated with the 5.925-6.425 GHz band to send signals back into space, the whole block was known as “conventional C-band” because that’s where most of the signals lived.

The FCC was able to carve out 280 MHz of spectrum in this band – the 3.7-3.98 GHz frequencies – for use by 5G operators. It became part of the historic 2020-2021 FCC auction in which Verizon paid a record $45.4 billion to get its hands on this essential new spectrum.

However, Verizon was not alone in this. AT&T lost $23.4 billion and T-Mobile’s bid was $9.3 billion.

C-band deployment

After the dust settled on the FCC spectrum auction, Verizon and AT&T quickly got to work using their new frequencies, planning to begin rolling them out on December 5, 2021.

Unfortunately, controversy ensued when the Federal Aviation Administration (FAA) and the US Department of Transportation called for a delay in deployments, warning that the new frequencies were dangerously close to the 4.2-4.4 GHz range. used by aircraft radar altimeters. After a series of delays, on January 19, 2022, the two carriers turned the key on their new midband service, finally delivering true 5G speeds to their customers.

Verizon has integrated the new C-band into its 5G Ultra Wideband service, which was originally deployed using the much higher frequency, shorter range mmWave spectrum. The result, the carrier said, was that more than 100 million additional people would be covered in more than 1,700 cities.

AT&T has taken a slow but steady approach, initially rolling out its C-band spectrum in just seven cities, with plans for gradual expansion.

However, AT&T also played its cards more cautiously. While Verizon put all of its money into the 3.7-3.98 GHz auction, AT&T hedged its bets, salvaging some of the high-frequency spectrum but waiting until it could salvage a lesser chunk. controversial in a later auction: 40 MHz of spectrum in the 3.45–3.55 GHz range.

Change the landscape

The deployment of 5G services on new C-band spectrum is already transforming the 5G landscape by enabling all three carriers to deliver the speeds that 5G was born for.

Prior to the C-band rollout, AT&T and Verizon were forced to use low-frequency spectrum and share it with their 4G/LTE networks using Distributed Spread Spectrum (DSS) technology. The result was 5G speeds that were barely distinguishable from 4G/LTE service.

T-Mobile was the only carrier with a head start. Through its 2020 merger with Sprint, the Un-carrier had gotten its hands on a larger 2.5 GHz band of spectrum previously used for Sprint’s 4G/LTE services. It quickly decommissioned those Sprint towers and reallocated that spectrum for its Ultra Capacity 5G service.

As a result, T-Mobile reached over 200 million customers with impressive 5G speeds months before AT&T and Verizon could even begin their C-band rollouts. That’s why T-Mobile has consistently ranked number one. in terms of 5G performance, coverage and reliability.

However, that gap has narrowed in recent months as Verizon and AT&T leveraged their new C-band spectrum. Although T-Mobile also scooped up some of that spectrum from the last year it’s been using it to supplement its existing 2.5 GHz network rather than setting up entirely new cells.

While T-Mobile had an obvious head start, AT&T and Verizon may have a decisive advantage by exclusively using the upper C-band frequencies. This will not be as important as the switch from low band to C-band. , but the 3.7–3.98 GHz spectrum should still allow both carriers to offer even faster speeds, even if it means they have to build a few more towers to ensure optimal coverage.

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Evelyn C. Tobin