There's change in the air, and the big cellphone companies are trying to make the most of it.

The change is 4G, or fourth-generation, cellphone service, made possible by a technology called LTE, or long-term evolution, which makes data travel through the air about 10 times faster than the previous 3G service.

The result is better video and improved Web browsing for phones and new services such as video surveillance and Internet access in moving cars.

LTE, which has been deployed across the country over the last four years, is now the driving force behind sales of smartphones. LTE-capable phones now account for half of U.S. cellphone sales, said research firm Strategy Analytics.

"The main attraction of LTE for consumers is faster download speeds," said Neil Mawston, an analyst at Strategy Analytics. "LTE is broadband in your pocket."

There's clearly something in it for cellphone companies, too.

"A main attraction of LTE for operators is more network capacity and a chance to upsell higher-priced data plans or devices," Mawston said.

The companies with the most national LTE coverage are Verizon Wireless, AT&T, T-Mobile and Sprint, in that order, Mawston said.

In Minnesota, Verizon Wireless said it has completed installing LTE in nearly the entire state. However, that doesn't mean you won't ever lose a signal on LTE, said Aaron Glass, executive director of network for Verizon's Great Plains region.

"There's a higher density of cell towers in the Twin Cities than in rural area, so there's a better chance that you won't lose a signal in the Twin Cities," Glass said.

How fast? Very fast

Verizon's typical LTE download speeds are 5 to 12 million bits per second, or megabits, while upload speeds are 2 to 5 megabits, he said. That's considerably faster than 3G service, which offers downloads of 1 megabit per second, and uploads of 0.3 to 0.4 megabits, Glass said. Speeds can be affected by the number of people using the cellular network at the same time.

"The traffic on the LTE network is in its infancy," Glass said. "The rate of traffic growth more than doubled from last year. The capabilities of 4G LTE are changing user behavior."

Despite those speeds, Verizon makes no claim that its LTE network is competitive with the speed of cable TV companies.

The reason: Verizon charges by the amount of data you download. Cable TV companies such as Comcast still allow customers to download unlimited amounts of data for a flat rate.

"We expect LTE to remain mostly a metered data service for now," said analyst Mawston. "If U.S. operators made LTE usage unlimited for the masses, it would quickly fill up the networks with traffic, reduce the user experience due to clogged networks, and diminish profits for carriers."

Big cities, major highways

AT&T says it has concentrated its LTE coverage in major Minnesota metro areas, including the Twin Cities, Duluth and Rochester, and on major highways. While AT&T's Minnesota LTE network is less extensive than Verizon's, the company says it also provides another tier of cellular service whose download speeds are about 40 percent as fast as LTE, but still faster than 3G.

"If customers fall off our competitor's LTE network, they go back to 3G because there's nothing in between," said Hardmon Williams, AT&T's vice president and general manager for Minnesota and the Northern Plains region. "We have two layers of mobile broadband."

T-Mobile said in an e-mail that it also has limited its coverage to larger Minnesota population areas, including the Twin Cities, St. Cloud, Rochester and Hudson, Wis.

Sprint, which is in the midst of a major nationwide conversion to LTE from its existing and largely unsuccessful 4G network that used WiMax technology, says it offers LTE in parts of the Twin Cities and smaller cities like Mankato, Faribault and Northfield.

Verizon is planning new LTE services, such as cellular video conferencing for corporate employees in remote offices, or two-way video for existing services, such as allowing customers at ATM banking machines to converse with a real bank employee.

LTE to get more work

Verizon also plans to shift voice calls and text messages to the LTE network as a way to improve voice quality and enable easy video calls, Glass said. Because the primary beneĀ­fit of LTE is faster data downloads, carriers tend to use them for video and other data-dense information while sending lower-data voice and text messages to the older 3G network.

AT&T's Williams says that new services for the company's LTE network will include home automation, which AT&T introduced earlier this year for its 3G network. AT&T also expects to introduce LTE service for automobiles early next year, and is working on ways to use LTE cellphones as credit cards.

"LTE is not just for devices you hold in your hand or for voice calls," Williams said.

But the LTE revolution won't happen all at once, and the slower 3G cellular network is expected to be available for years to come.

"We expect 3G networks to be active until the early 2020s," said analyst Mawston. "There will be plenty of demand for 3G services in rural areas where 4G does not reach for years to come."