5G isn’t replacing 4G, like how 4G overtook 3G. Instead, 5G is building on 4G LTE, using updated radios and software. “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.”
Right now, 5G networks in the US are something called “non standalone.” “With non standalone mode, [carriers] retain the same 4G core network and simply add 5G radios,” Most of the 5G networks in the US today also rely on 4G for uploads and use only 5G connections for downloads. 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.
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. “The problem with refarming was it could take 10 years, …”
Instead of having different roads for buses and cars, DSS (dynamic spectrum sharing) 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. 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.
That magic results in faster and broader 5G network launches. When 5G carrier aggregation happens, operators can combine millimeter wave (mmWave) 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.
[editor’s comment] hmm, don’t hold your breath on aggregating mmWave with the lower sub-6Ghz! Takes TWO connections and RF propagation differences will be implementaion difficults. IMO, the comment is purely theoretical. [/editor]
Please see the article for more details
This transition is different from earlier cellular generation shifts, which means 4G could be useful a lot longer.