5G buzz is everywhere. Billboards display the latest, fastest gadgets like Samsung's Galaxy S10 5G, TV ads tout the benefits of the fast speeds and carriers are jockeying for title of best 5G network. But with 5G networks in the US only a few months old, your 4G phone isn't destined for the junk heap yet. In fact, the ramp-up to 5G means your 4G phone may actually get better.
5G is touted as a game-changing technology, with the ability to dramatically boost the speed and coverage of wireless networks. It can run between 10 and 100 times faster than your typical 4G cellular connection today. It's quicker than anything you can get from a physical fiber-optic cable in your house. And latency, the amount of time between when your phone pings the network and when it responds, is faster than what Wi-Fi provides.
But 5G also has limitations. The higher-frequency bands rolled out first by Verizon and AT&T, called millimeter wave, provide super-high speeds, but the signals travel only short distances. Things like trees and double-pane glass block millimeter wave signals. T-Mobile, Sprint and most carriers in Europe and Asia have opted to build their broader 5G networks using sub-6GHz or mid-band spectrum, the lower-frequency airwaves that are more stable but slower than millimeter wave. They travel longer distances, but speeds can be similar to what you find with some LTE connections, not the dramatic leap you get with millimeter wave.
"Right now there are huge compromises with 5G in terms of design, coverage and cost," IHS Markit analyst Wayne Lam said. "4G LTE and 5G will coexist for a very, very long time."
There are some unique features of the shift to 5G that can help the operators move quicker than before -- without forcing everyone onto the faster network at once. Here's how 4G and 5G will coexist for years to come:
4G and 5G coexistence
The move from 4G to 5G is different from past network upgrades. 5G isn't replacing 4G, like how 4G overtook 3G. Instead, 5G is building on 4G LTE, using updated radios and software. Right now, if you have an early 5G phone phone and upload videos to Google Photos, you're actually using a 4G LTE connection for that uplink.
"This is the first time so many aspects of [the old and new network] are shared," said Gordon Mansfield, AT&T vice president for converged access and device technology. "Some things we'll do for 5G are inherently backward compatible and will lift the capabilities of 4G."
By 2025, 15% of mobile connections in the world will be on 5G, according to a 2019 report by GSMA Intelligence, the research arm of the mobile operator group that hosts Mobile World Congress. But LTE usage will be about 59% by the same year, up from 43% in 2018. (In North America, the split will be more even, with about 47% of 2025's connections on 5G and 44% on 4G). Even if 5G becomes an even bigger part of the market by 2025 than estimated today, "it will complement rather than replace LTE," GSMA said in a separate report from last year.
"For operators in many parts of the world, LTE is and will be the foundation for the next 10 years at least," the GSMA report said. "LTE speeds are improving, which makes 5G less compelling without new services such as AR/VR."
The first 5G connections still need 4G
Right now, 5G networks in the US are something called "non standalone." They need 4G as the anchor to make that initial handshake between a phone and network before passing the device along to a 5G connection. Using non standalone technology allows carriers to roll out 5G more quickly than if they had to completely overhaul their entire networks with new hardware.
"With non standalone mode, [carriers] retain the same 4G core network and simply add 5G radios," said Durga Malladi, Qualcomm's head of 5G.
The next flavor of 5G network, called "standalone," lets a phone go straight to 5G, but it could take several years to roll out in the US and globally. At least through the end of next year, all devices on AT&T's network will use non-standalone technology, Mansfield said. It's not until late 2021 or early 2022 that standalone networks will really roll out, he said.
Most of the 5G networks in the US today also rely on 4G for uploads and use only 5G connections for downloads. That made it less complex for carriers to develop their networks. While you can download a video in record time, uploading one will take as long as it did before -- at least for now. Verizon deployed 5G for uploads in Providence, Rhode Island earlier this month, but other areas and carriers will have to wait until later this year or next year.
4G will remain great (for some)
Even when 5G is widespread, phones and networks in the US will need to access older wireless technologies. Parts of the US, particularly some rural areas, may not have 5G for years, and there are some devices, like smart locks and other smart home products, that may use 4G for a decade or longer.
Until they do get an upgrade, 4G is more than enough for Internet of Things devices. Right now, most smart home devices don't even use 4G but instead opt for Wi-Fi or Bluetooth connections. Those products typically don't use a lot of data, so a super fast network isn't critical. Smart home products also require long battery life, and 5G's power consumption may not be low enough for battery-powered IoT devices. At the same time, 5G chips are pricey, so something like a $10 smart light bulb may need cheaper connectivity components.
"4G is great for [all of] that," said Peter Linder, 5G evangelist at cellular network gear provider Ericsson.
5G also will take some time to make its way into lower-end smartphones, particularly those for prepaid service plans. Those devices are likely to stick to 4G for the next few years, AT&T's Mansfield said, and customers who buy prepaid phones tend to hold onto them longer.
"Those devices will drive the bulk of traffic on LTE at the latter part of the decade," he said.
4G and 5G networks can share spectrum
All wireless signals travel over invisible airwaves via radio frequency called spectrum. The amount of spectrum is limited, and two carriers can't use the same spectrum at the same time. 2G, 3G and 4G connections can't share the same spectrum, either. They each need their own dedicated lanes to deliver service.
Something called spectrum refarming lets carriers shift older spectrum to new wireless networks, like moving from 3G to 4G. That's essential to free up spectrum for new uses, like all of those apps we download on our 4G devices. In the past, carriers had to wait until essentially all users of an older network had left a particular spectrum band before it could be changed to the newer technology. It was either 3G or 4G -- not both.
"The problem with refarming was it could take 10 years," said Dean Brenner, Qualcomm senior vice president for spectrum strategy and tech policy.
That changes when it comes to 5G, thanks to something called dynamic spectrum sharing, or DSS. The technology, likely available in 2020 in the US, lets carriers use the same spectrum band for both 4G and 5G. Instead of having different roads for buses and cars, DSS is like having one big highway with separate lanes for buses and cars. A software update can quickly turn the current 4G LTE networks into 5G.
"This is a game changer," said Qualcomm's Malladi.
The benefit of DSS today is that it lets carriers roll out their 5G networks quickly and deal with the spectrum shortages. Going forward, DSS will make it easier for carriers to keep some 4G lanes open for 4G smart home products or for people who are slow with moving to 5G.
And something called dual connectivity, which is available today, lets phones run on both 4G and 5G networks to make sure you never drop a signal even if you move out of 5G range. It also combines the two to give you faster speeds.
Sprint's 5G network, which uses mid-band spectrum and went live in Chicago on Thursday, has a feature called "split-mode" -- essential dual connectivity -- that lets Sprint simultaneously deliver 4G LTE Advanced and 5G service. It gives Sprint "a nearly identical footprint for both 4G LTE and 5G NR coverage," the company said.
"On the same hardware, you kill two birds with one phone," Sprint Technology Chief John Saw said. He added that the company continues to invest in building out its 4G network. "You'll see [4G] improving."
Combining 4G and 5G signals
Another 4G and 5G technology, called carrier aggregation, has the ability to combine multiple wireless signals into one. This allows for even higher speeds than when running on one band by itself. It's like combining several one-lane roads to make a multi-lane highway with a faster speed limit.
5G marks the first time a cellular technology can power a device at the same time as a previous generation, 4G. Carrier aggregation is commonly used to combine 4G signals with other 4G signals, which provided "a huge performance and capacity lift," said Heidi Hemmer, vice president of networking and technology at Verizon.
Soon carriers soon will be able to combine 4G and 5G with carrier aggregation. In the US, the network operators could start using the technology as soon as 2020.
"Whatever spectrum resources you have, you can use them and combine them into one big thing," Ericsson's Linder said. "From a user perspective, you don't see what's going on. The magic is in the background."
That magic results in faster and broader 5G network launches. When 5G carrier aggregation happens, operators can combine millimeter wave for downloads and sub-6Ghz for uploads. Or they can do a combination of sub-6Ghz and sub-6Ghz, or sub-6Ghz plus 4G LTE and so on and so forth.
"For operators who have millimeter wave networks, like in the US, this is a significant enhancement in the range of millimeter wave coverage," Qualcomm President Cristiano Amon said.
4G connections should get faster
While 5G is new and will keep improving, so too will 4G. 5G builds on 4G, so users will see faster 4G LTE speeds -- particularly when paired with 5G. They'll also see lower latencies thanks to the steps operators are taking with 5G.
But 4G chips likely won't see huge speed increases on their own. MediaTek, one of the world's only remaining wireless chip makers, isn't investing in 4G on its own anymore. Instead, it will seek to boost 4G speeds only on modems that also have 5G connectivity, said Finnbar Moynihan, MediaTek's vice president of corporate sales and business development in the Americas and Europe.
"For standalone 4G chipsets, the speeds we have [today] is the way they'll remain," Moynihan said. "But when a customer buys a 5G solution, they'll get 5G plus a much higher 4G [speed] built in."
The fastest version of 4G LTE available in the US today is called LTE Advanced (In the case of Qualcomm's X24 modem, devices 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).).
Those gigabit-speed LTE networks are a key first step in the move toward 5G, Qualcomm's Amon said. Network operators and device makers will keep rolling out improved LTE Advanced, which should get even speedier than 2Gbps.
"Most of the operators are upgrading 4G to higher speeds so you have service continuity as you use applications more dependent on broadband speeds," Amon said. "If your phone is capable of supporting higher speeds, you will be able to benefit from that transition from LTE to gigabit LTE."
As more people move to 5G, there won't be as many phones on 4G networks. That frees up capacity and gives you speeds closer to the peaks. Because of DSS, the carriers know they can easily switch their 4G connections to 5G when more devices connect to the newer network, so there's little downside in building out 4G right now.
Until you're ready to buy your first 5G device, enjoy your faster 4G LTE phone.
Originally published at 5 a.m. PT
Update at 3:45 p.m. PT: Adds Sprint CTO and Verizon networking executive comments.