How 5G frequencies affect range and speed

Experts say that while 5G technology is a huge improvement over previous generations of wireless technology, much of the impetus for 5G to move into new spectrum bands comes from old-fashioned physics.

It can be difficult to pinpoint exactly what frequencies 5G technology will use, in part because it varies so much between countries and even between different carriers. However, most 5G frequencies can be put into three main groups.

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Low-end: 650MHz to 1GHz

Lower frequencies — from 650MHz at the lowest to 1GHz at the highest — are particularly favored by wireless companies deploying 5G. Signals in this range travel over relatively long distances, which means service providers can cover a large area with a single access point.

However, using 5G in the lower ranges of the 5G radio spectrum is a serious limiting factor, according to Gartner analyst Bill Ray.

“These frequencies are very popular,” he said.

This is a problem because while the channel capacity at the low end is the same as at higher frequencies – that is, a 5MHz-wide channel in the 850MHz range offers the same throughput as a 5MHz-wide channel in the 2.6GHz range – the lack of available spectrum means there simply aren’t enough channels to deliver the high connection speeds advertised by 5G.

To achieve higher speeds, 5G uses wider channels. "In 3G, the standard transmission was 5MHz wide," Ray added. "In 5G, we're talking about 100MHz-wide slots, so your transmission channels can run anywhere from 2.4Ghz to 2.5Ghz."

In the middle: Sub-6GHz and the peak of the spectrum

Most of the performance and efficiency gains promised by 5G technology rely on a portion of the spectrum close to Wi-Fi – the “sub-6GHz” range between 2.4GHz and 6GHz, which is a departure for service providers who are used to running it a little lower.

“Sub-6GHz is new spectrum for them,” said Patrick Filkins, senior research analyst at IDC. “It means bigger channels and improved latency.”

Another issue is that there is available spectrum in this band, specifically in the Citizens Broadband Radio Service/General Authorized Access (CBRS/GAA) spectrum between 3.5GHz and 3.7GHz. This spectrum uses a priority access system, where users are given first dibs, but other users may use the frequency anywhere that does not interfere with those users. Needless to say, the operators are interested in the spectrum.

As individual carriers scramble for their own share of precious spectrum, 5G coverage will continue to expand, and its advantage over Wi-Fi in one particular respect will become more apparent. 5G spectrum is allocated to one licensee per geographic region, while Wi-Fi offers no such exclusivity; anyone can use it anywhere, setting the stage for signal overlap and interference.

“The way cellular is deployed is deterministic — one of its biggest benefits over Wi-Fi is its ability to overcome interference issues that Wi-Fi hasn’t yet solved,” Filkins said.

High-end: millimeter wave

For all its optimizations and sophistication, 5G still requires a lot of bandwidth to deliver on its promise of multi-gigabit throughput. And while the wireless industry is aggressively pursuing bandwidth at lower frequencies, there just isn’t enough room to go around in the more desirable 6GHz and sub-1GHz ranges.

Millimeter wave technology, which operates in the frequency range of 24GHz to 60GHz, depending on which expert you talk to and the specific technology involved. These particularly high frequency bands allow for particularly wide transmission channels, resulting in extremely fast connection speeds, but there are a number of disadvantages.

“The only good thing about millimeter wave frequencies is that they’re empty, so there’s plenty of room,” Ray said.

First, due to basic physics, signals in the millimeter wave range simply don’t travel very far compared to signals in lower regions of the RF spectrum, and they don’t penetrate solid objects such as walls and windows. This means that to cover a given area (even within a single building) you need to deploy a large number of access points.

"It's not ready for enterprise deployment yet," Filkins said. "It's not powerful right now, but it has a lot of potential."

Millimeter wave technology has been around for at least a decade. The unlicensed wireless world has long had the 802.11ad standard, which is essentially Wi-Fi running at millimeter wave frequencies. Qualcomm and Huawei have both made equipment that operates in that range, but the limitations of the technology, and the continued drought of end devices that can actually take advantage of it, means it has remained on the sidelines.

Of course, this won’t always be the case. Trends in wireless bandwidth requirements indicate that the demand for spectrum will be so great that mmWave will be needed to address it.

“The rest of the world will eventually use [millimeter wave], they’re not using it now,” Ray said.

But for now, especially given the fact that adding millimeter-wave antennas and modems to phones and laptops will increase their unit costs by $20, Ray said millimeter-wave will remain a technology of the future.