All of the US carriers have now launched some form of 5G cellular network. But what exactly is 5G, and how fast is it compared with 4G? Here are the facts we know so far.
The race to 5G is on. All four major US carriers now have some form of 5G wireless. We're tracking the rollouts monthly .
But 5G is currently very confusing. Three major flavors of 5G have come out: low-band, mid-band, and high-band, all of which perform very differently from each other. We've been testing all of them as they appear. The most widespread version, low-band, operates and performs pretty much like 4G.
5G is an investment for the next decade, and in previous mobile transitions, we've seen most of the big changes happening years after the first announcement. Take 4G, for instance. The first 4G phones in the US appeared in 2010, but the sorts of 4G applications that changed our world didn't appear until later. Snapchat came in 2012, and Uber became widespread in 2013. Video calls over LTE networks also became widespread in the US around 2013.
So following that plan, while we're getting a little bit of 5G right now, you should expect the big 5G applications to crop up around 2021 or 2022. Until then, things are going to be confusing as wireless carriers jockey for customers and mindshare.
5G stands for fifth-generation cellular wireless, and the initial standards for it were set at the end of 2017. Let us take you down the 5G rabbit hole to give you a picture of what the upcoming 5G world will be like.
1G, 2G, 3G, 4G, 5G
First of all, if you're hearing about 5G Wi-Fi or AT&T's "5G E" phones, they aren't 5G cellular. Here's a full explainer on 5G vs. 5G E vs. 5GHz: What's the Difference?
And if you're hearing that 5G means millimeter-wave towers on every lamppost, that's not true. That's only one of the three main forms of 5G we're seeing right now.
The G in this 5G means it's a generation of wireless technology. While most generations have technically been defined by their data transmission speeds, each has also been marked by a break in encoding methods, or "air interfaces," that make it incompatible with the previous generation.
1G was analog cellular. 2G technologies, such as CDMA, GSM, and TDMA, were the first generation of digital cellular technologies. 3G technologies, such as EVDO, HSPA, and UMTS, brought speeds from 200kbps to a few megabits per second. 4G technologies, such as WiMAX and LTE, were the next incompatible leap forward, and they are now scaling up to hundreds of megabits and even gigabit-level speeds.
5G brings three new aspects to the table: bigger channels (to speed up data), lower latency (to be more responsive), and the ability to connect a lot more devices at once (for sensors and smart devices).
The actual 5G radio system, known as 5G-NR, isn't the same as 4G. But all 5G devices in the US, for now, need 4G because they'll lean on it to make initial connections before trading up to 5G where it's available. That's technically known as a "non standalone," or NSA, network. Later this year, our 5G networks will become "standalone," or SA, not requiring 4G coverage to work.
It turns out that SA 5G is much more important than we thought it was in 2019. Except on Sprint, carriers' 5G cells are shaped differently than their 4G ones, so they're losing coverage where the 4G signal cuts out but the 5G one continues. When the networks evolve into standalone mode, we may see a sudden growth in urban coverage.
4G will continue to improve with time, as well. The Qualcomm X24 modem, which is built into most 2019 and 2020 Android flagship phones, supports 4G speeds up to 2Gbps. The real advantages of 5G will come in massive capacity and low latency, beyond the levels 4G technologies can achieve.
That symbiosis between 4G and 5G has caused AT&T to get a little overenthusiastic about its 4G network. The carrier has started to call its 4G network "5G Evolution," because it sees improving 4G as a major step to 5G. It's right, of course. But the phrasing is designed to confuse less-informed consumers into thinking 5G Evolution is 5G, when it isn't.
Low, Middle, and High
5G gives carriers more options in terms of airwaves than 4G did. Most notably, it opens up "high-band," short-range airwaves that didn't work with 4G technology. But 5G can run on any frequency, leading to three very different kinds of 5G experiences—low, middle, and high.
The key thing to understand here is that 5G speeds are directly related to how wide the available channels are, and how many are available. With 4G, you can combine up to seven, 20MHz channels to use a total of 140MHz of spectrum. Most of the time, though, phones are using 60MHz or less.
With current phones in low- and mid-band 5G, you can combine two 100MHz channels, for 200MHz usage—and stack three more 20MHz 4G channels on top of that. In high-band 5G, you can use up to eight 100MHz channels. The great speeds 5G carriers promise are just about leveraging more airwaves at once. But if you don't have the airwaves available, you don't get the speeds.
Average 5G download speeds, December 2019—AT&T is high-band only
Right now, networks need to put up 'walls' between their 4G and 5G channels. The two can't coexist closely. Later in 2020, that will change with a technology called dynamic spectrum sharing, or DSS. DSS makes the walls flexible and movable, so carriers can dynamically split channels between 4G and 5G based on demand. AT&T and Verizon will both be using DSS heavily, and that will require DSS-compatible phones.
T-Mobile's low-band 5G airwaves have excellent coverage
Low-band 5G operates in frequencies below 2GHz. These are the oldest cellular and TV frequencies. They go great distances, but there aren't very wide channels available, and many of those channels are being used for 4G. So low-band 5G is slow. It acts and feels like 4G, for now. Low-band 5G channels are from 5MHz in width (for AT&T) up to 20MHz (for T-Mobile), so you can see they aren't roomier than 4G.
Complicating things, AT&T and T-Mobile low-band phones sometimes show 5G icons when they aren't even using 5G, making it hard to tell any difference.
Mid-band 5G is in the 2-10GHz range. That covers most current cellular and Wi-Fi frequencies, as well as frequencies slightly above those. These networks have decent range from their towers, often about half a mile, so in most other countries, these are the workhorse networks carrying most 5G traffic. Most other countries have offered around 100MHz to each of their carriers for mid-band 5G. Here in the US, New T-Mobile will use Sprint's spectrum for a mid-band network, using up to 120MHz per city. AT&T and Verizon will shave off little bits of their 4G spectrum using DSS for mid-band 5G, 10MHz here and 10 there.
High-band 5G is much faster than 4G
High-band 5G, or millimeter-wave, is the really new stuff. So far, this is mostly airwaves in the 20-100GHz range. These airwaves haven't been used for consumer applications before. They're very short range; our tests have shown about 800-foot distances from towers. But there's vast amounts of unused spectrum up there, which means very fast speeds using up to 800MHz at a time. Verizon relies extensively on high-band, which it calls "ultra wideband." AT&T has some, in small parts of 35 cities. T-Mobile has a bit, more broadly in 7 cities.
T-Mobile describes the three forms of 5G as a 'layer cake'
High bands have been used before for backhaul, connecting base stations to remote internet links. But they haven't been used for consumer devices before, because the handheld processing power and miniaturized antennas weren't available. Millimeter-wave signals also drop off faster with distance than lower-frequency signals do, and the massive amount of data they transfer will require more connections to landline internet. So cellular providers will have to use many smaller, lower-power base stations (generally outputting 2-10 watts) rather than fewer, more powerful macrocells (which output 20-40 watts) to offer the multi-gigabit speeds that millimeter-wave networks promise. Because of the very fast drop-off, the waves are quite weak when they get to you.
In many major cities, the carriers installed these "small cells" to increase 4G capacity starting in 2017. (From my office window in New York, I can see several small cell sites.) In those cities, they just need to bolt an extra radio onto the existing site to make it 5G. There's a struggle going on elsewhere, though, where carriers are having trouble convincing towns to let them add small cells to suburban neighborhoods. That's similar to previous struggles over establishing cellular service at all in many of these towns.
How 5G Works
Like other cellular networks, 5G networks use a system of cell sites that divide their territory into sectors and send encoded data through radio waves. Each cell site must be connected to a network backbone, whether through a wired or wireless backhaul connection.
High-band 5G, or millimeter-wave, is the really new stuff. So far, this is mostly airwaves in the 20-100GHz range. These airwaves haven't been used for consumer applications before. They're very short range; our tests have shown about 800-foot distances from towers. But there's vast amounts of unused spectrum up there, which means very fast speeds using up to 800MHz at a time. Verizon relies extensively on high-band, which it calls "ultra wideband." AT&T has some, in small parts of 35 cities. T-Mobile has a bit, more broadly in 7 cities.
T-Mobile describes the three forms of 5G as a 'layer cake'
High bands have been used before for backhaul, connecting base stations to remote internet links. But they haven't been used for consumer devices before, because the handheld processing power and miniaturized antennas weren't available. Millimeter-wave signals also drop off faster with distance than lower-frequency signals do, and the massive amount of data they transfer will require more connections to landline internet. So cellular providers will have to use many smaller, lower-power base stations (generally outputting 2-10 watts) rather than fewer, more powerful macrocells (which output 20-40 watts) to offer the multi-gigabit speeds that millimeter-wave networks promise. Because of the very fast drop-off, the waves are quite weak when they get to you.
In many major cities, the carriers installed these "small cells" to increase 4G capacity starting in 2017. (From my office window in New York, I can see several small cell sites.) In those cities, they just need to bolt an extra radio onto the existing site to make it 5G. There's a struggle going on elsewhere, though, where carriers are having trouble convincing towns to let them add small cells to suburban neighborhoods. That's similar to previous struggles over establishing cellular service at all in many of these towns.
How 5G Works
Like other cellular networks, 5G networks use a system of cell sites that divide their territory into sectors and send encoded data through radio waves. Each cell site must be connected to a network backbone, whether through a wired or wireless backhaul connection.
5G networks use a type of encoding called OFDM, which is similar to the encoding that 4G LTE uses. The air interface is designed for much lower latency and greater flexibility than LTE, though.
With the same airwaves as 4G, the 5G radio system can get about 30 percent better speeds thanks to more efficient encoding. The crazy gigabit speeds you hear about are because 5G is designed to use much larger channels than 4G does. While most 4G channels are 20MHz, bonded together into up to 140MHz at a time, 5G channels can be up to 100MHz, with Verizon using as much as 800MHz at a time. That's a much broader highway, but it also requires larger, clear blocks of airwaves than were available for 4G.
That's where the higher, short-distance millimeter-wave frequencies come in. While lower frequencies are occupied by 4G, by TV stations, by satellite firms, or by the military, there had been a huge amount of essentially unused higher frequencies available in the US, so carriers could easily construct wide roads for high speeds.
5G networks need to be much smarter than previous systems, as they're juggling many more, smaller cells that can change size and shape. But even with existing macro cells, Qualcomm says 5G will be able to boost capacity by four times over current systems by leveraging wider bandwidths and advanced antenna technologies.
The goal is to have far higher speeds available, and far higher capacity per sector, at far lower latency than 4G. The standards bodies involved are aiming at 20Gbps speeds and 1ms latency, at which point very interesting things begin to happen.
AT&T (left) and T-Mobile (right) cover much of the Providence area with low-band 5G
