Joshua Goldman/CNET
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.
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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," saidGordon 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.
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