AT&T plans to invest more than $100 million on its network in Colorado this year to bolster Internet speeds, improve call quality and better handle high-traffic locations such as Invesco Field at Mile High.

The nation’s No. 2 wireless carrier will deploy fiber-optic connections to about 400 cell sites in the Denver area. The upgrade, which covers more than half of AT&T’s roughly 750 cell sites in the state, will boost mobile Internet capacity and speeds.

AT&T also will add 24 new cell sites in metro Denver, which will broaden coverage and help eliminate potential dead zones. The company added 10 sites in the area in 2010.

“We’re building new sites and expanding existing sites just as fast as we can,” said AT&T Colorado president Bill Soards. “We have consistently invested over $100 million a year in the state, and it continues to increase.”

The oft-criticized carrier is also installing advanced antenna systems at high-traffic venues such as Invesco Field and the Pepsi Center to improve coverage.

Other network improvements will include the deployment of newly acquired wireless spectrum and the reallocating of existing spectrum previously used for older 2G connections for 3G traffic.

“It’s like adding additional lanes to the highway,” said Jace Barbin, general manager for AT&T’s Rocky Mountain Region.

From 2008 to 2010, AT&T spent $375 million on network enhancements in Colorado, Barbin said.

“High-tech expansions like this one help our business community, our local economy and our overall quality of life,” said Tom Clark, executive vice president of the Metro Denver Economic Development Corp.

AT&T, which proposed last month to acquire No. 4 wireless carrier T-Mobile, didn’t provide details on when its high-speed 4G LTE network would light up in Colorado. The network is slated to go live in certain markets in the middle of this year.

AT&T’s existing 4G service uses upgraded 3G technology. The company’s 2011 network upgrades in Colorado should increase those speeds.

Separately, T-Mobile plans to announce today that its 4G network, which technically is also upgraded 3G, has expanded to the Fort Collins- Loveland area. The service is already available in Denver, Boulder, Colorado Springs, Grand Junction and Greeley.

Andy Vuong: 303-954-1209, avuong@denverpost.com or twitter.com/andyvuong