5G glossary: From spectrum to small cell to MIMO

5G is on every techie's mind. At least, it was before the coronavirus hit. But the next-generation wireless networks continue to roll out despite the pandemic, and if you're interested in technology at all, 5G and its baggage of technical terms will is a reality for you. 

But not to fret! That's what CNET is all about -- deciphering and explaining complicated topics so you walk out looking like a mobile expert. 

If you want to know everything about how 5G works, we've got a handy guide for you. But if you want to sound like an expert, this is the place for you. 

The following is our glossary of 5G terms.

4G

Before we get into 5G, let's talk about 4G, the network we're on today. It stands for the fourth generation of mobile technology, and it launched in late 2010. While 3G networks primarily dealt with phone calls and text messaging, 4G was the first to really emphasize data speeds comparable to those of your home broadband connection. That data focus led to the emergence of the app economy, as well as services like Uber, livestreaming and sophisticated mobile gaming. 

5G

5G, of course, stands for the fifth generation of wireless technology. If 4G brought higher speeds, 5G amps that up and allows for the better connection of more devices, including offering variable speeds based on the needs of the connected gadget. A smartphone is going to consume a lot of bandwidth when livestreaming, while an ATM needs an infrequent, but dependable connection. 

OK, enough of the simple stuff. Let's get wonky.

5G NR 

The 5G bit is pretty obvious, but the NR stands for New Radio. You don't have to know a lot about this beyond the fact that it's the name of the standard the entire wireless industry has rallied behind.

That's important because it means everyone is on the same page when it comes to their mobile 5G networks. Carriers like AT&T and T-Mobile are following 5G NR as they build their networks. But Verizon , which began testing 5G as a broadband replacement service before the standard was approved, initially wasn't using the standard when it launched in late 2018. The company did eventually adopt 5G NR for its broadband service, with its mobile network running on the NR standard too.

Given that everyone is using the same standard, you'll likely hear the term less. But it's key to know the name of the technology that serves as the common foundation for 5G networks. 

Latency

If speed is the headline benefit, latency is the feature of 5G that many believe will actually drive a lot of the innovation. Latency is the lag time that happens when you click on a link or fire a gun in a mobile game and the phone pings the network and receives a response. You probably noticed a slight hesitation when chatting with someone on Zoom -- that's the lag time as the signals physically travel across great distances. 

That lag time can last around 20 milliseconds with current networks. It doesn't seem like much, but it makes a difference if you need instantaneous response. For anyone playing Fortnite, making sure your character actually shoots when you hit the button is critical. 

With 5G, that latency gets reduced to as little as 1 millisecond, or about the time it takes for a flash on a normal camera. The caveat is that lag time can still be a factor if you're communicating with someone far away. 

Spectrum

Spectrum is referred to as the "lifeblood of the wireless industry." That's because these radio airwaves, similar to how you get radio channels in your car, are how you also get cellular signals. But you don't need to tune your phone like a radio to get different channels -- your phone is set to automatically tap into the appropriate frequency. 

Wireless carriers use spectrum to ferry data over the air, and over time, they've gotten better and more efficient at this process. 

Wireless carriers each have their own swath of spectrum, which power older 3G and 4G networks. But these companies are looking to secure more spectrum to enable a broader rollout of 5G. 

Generally, the higher the band or frequency, the higher the speed you can achieve. The down side of higher frequency, however, is shorter range. 

Conversely, the lower the band, the better the range, but there's a limit to how fast your connection will be. 

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Millimeter wave

This refers to a really high-frequency spectrum. The millimeter wave range falls between 24 gigahertz and 100 gigahertz. Whenever someone talks about the crazy speeds you get with 5G, they're often referring to the flavor of 5G running on this kind of spectrum. 

The problem with super high-frequency spectrum, besides the short range, is it's pretty finicky -- if a leaf blows the wrong way, you get interference. Forget about obstacles like walls. Companies including Verizon are working on using software and broadcasting tricks to get around these problems and ensure stable connections.

Think about millimeter wave coverage zones as glorified Wi-Fi hotspots with insane speeds. It's fantastic if you're in one -- just don't walk too far away. 

Low Band

Carriers have been using low-frequency bands for years to power 3G and 4G networks that we use today. Much of the 4G network in the US, for instance, runs on 700 megahertz spectrum. The industry likes using low-band radio airwaves because they travel across great distances and penetrate walls. 

But that long range comes at a price. If millimeter wave is one side of the equation with a fat bandwidth pipe, then low-band spectrum sits on the other side, with a limited amount of speed you can place on those airwaves. 

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Midband

Midband, as its name suggests, sits in between the low and millimeter wave spectrums. It's considered a "sweet spot" swath of radio frequencies because it has a nice mix of speed and range. 

Most of the carriers around the world launched with midband spectrum, but because the US carriers lacked radio airwaves in this frequency, they opted to invest in the flashier and faster millimeter wave technology. 

In the US, only T-Mobile has a significant swath of 2.5 GHz midband spectrum, which it obtained from Sprint . In fact, that's the primary reason why T-Mobile worked so hard to acquire its rival. 

There isn't necessarily one band of spectrum that's better than the rest. The carriers all understand that they'll need all three in order to offer complete coverage. 

Sub-6 GHz

Sub-6Ghz is a term that generally groups together the low and midband frequencies. Back when a few of the early carriers were talking up millimeter wave, Sub-6 became the alternative path for 5G that allowed carriers to reuse their existing stash of spectrum. 

5G E

Sorry, but it's marketing fluff. AT&T's 5G E stands for 5G Evolution, its upgraded 4G LTE network that has a path to real 5G. 

But the designation, which showed up on phones early in 2019, has caused some consumer confusion, with some thinking they already have 5G. To be clear, it's not, with many bashing AT&T for misleading customers. Sprint filed a lawsuit against AT&T, which, according to an AT&T spokesperson, the companies "amicably settled." The National Advertising Review Board has recommended that AT&T stopping using the term in its marketing, although the icon on your AT&T phone remains. 

AT&T has said it's "proud" that it went with the 5G E name. 

5G E does bring higher speeds, but not the kind of true benefits real 5G would bring. 

5G UWB (or 5G UW) and 5G Plus

Verizon and AT&T each have their own different (but really, the same) designation for millimeter wave-based 5G. 

CNET has a whole separate story dedicated to the marketing of 5G. 

DSS

Dynamic spectrum sharing, or DSS, allows a carrier to take spectrum already in use for 4G and allow it to also work for 5G. If a wireless network is like a multilane freeway, DSS would allow a carrier to redesignate lanes as 5G or 4G on the fly based on their specific needs. 

In the US this helps providers like AT&T and Verizon which currently don't have as much free midband or low-band spectrum to offer multiple flavors of 5G. While the technology is useful to T-Mobile as well, the carrier acquired a large chunk of midband spectrum when it completed its merger with Sprint in April. 

5G SA

Known as 5G standalone, this is a 5G network that doesn't rely on a 4G LTE network to provide a backbone. As "true 5G" networks, these deployments have lower latency and even faster speeds. 

5G NSA

The early form of 5G networks, 5G non-standalone (5G NSA) uses an LTE anchor while allowing carriers to provide some of the early upgrades of 5G on compatible devices, particularly when it comes to speed.  

Small cell

Traditional cellular coverage typically stems from gigantic towers littered with different radios and antennas. Those antennas are able to broadcast signals at a great distance, so you don't need a lot of them. Small cells are the opposite: backpack-size radios that can be hung up on street lamps, poles, rooftops or other spots. They can broadcast a 5G signal only at a short range, so the idea is to have a large number of them in a densely packed network. 

Some cities have this kind of dense network in place, but if you go outside the metro area, that's where small cells become more of a challenge. 

MIMO

An abbreviation of "multiple input, multiple output." Basically, it's the idea of shoving more antennas into our phones and onto cellular towers. And you can always have more antennas. They feed into the faster Gigabit LTE network, and companies are deploying what's known as 4x4 MIMO, in which four antennas are installed in a phone.

Carrier aggregation 

Wireless carriers can take different bands of radio frequencies and bind them together so phones like the Samsung Galaxy S8 can pick and choose the speediest and least congested one available. Think of it as a three-lane highway so cars can weave in and out depending on which lane has less traffic.

This is often referred to as dual connectivity.

QAM 

This is a term that's so highly technical, I don't even bother to explain the nuance. It stands for quadrature amplitude modulation. See? Don't even worry about it.

What you need to know is that it allows traffic to move quickly in a different way than carrier aggregation or MIMO. Remember that highway analogy? Well, with 256 QAM, you'll have big tractor trailers carrying data instead of tiny cars. MIMO, carrier aggregation and QAM are already going into 4G networks, but they play an important role in 5G too.

Gigabit LTE (LTE Advanced)

Gigabit LTE, also known as LTE Advanced, is a precursor to 5G. Ultimately it's about much higher speeds on the existing LTE network. But the work going toward building a Gigabit LTE network provides the foundation for 5G.

Devices using Qualcomm's X24 modem can use carrier aggregation and other techniques to get peak download rates of 2Gbps. That's fast enough to download the third season of Stranger Things in about 8 seconds (though LTE Advanced realistically will give you download speeds of 200Mpbs to 600Mbps, still much faster than the previous LTE average speed of 100Mbps to 300Mbps).

For more on Gigabit LTE, read our explainer here.

AT&T's 5G E is an example of LTE Advanced. 

Beam forming 

This is a way to direct 5G signals in a specific direction, potentially giving you your own specific connection. Verizon has been using beam forming for millimeter wave spectrum, getting around obstructions like walls or trees.

Unlicensed spectrum 

Cellular networks all rely on what's known as licensed spectrum, which they own and purchased from the government.

But the move to 5G comes with the recognition that there just isn't enough spectrum when it comes to maintaining wide coverage. So the carriers are moving to unlicensed, public spectrum, similar to the kind of free airwaves that our Wi-Fi networks ride on.

Historically, that's been a controversial prospect because unlicensed spectrum was seen as less secure than spectrum locked up by a specific carrier. 

Network slicing

This is the ability to carve out individual slivers of spectrum to offer specific devices the kind of connection they need. For instance, the same cellular tower can offer a lower-power, slower connection to a sensor for a connected water meter in your home while at the same time offering a faster, lower-latency connection to a self-driving car that's navigating in real time.