DETROIT — AT&T Inc. said Tuesday that it had invested more than $1.5 billion in its Michigan wireless and wireline networks from 2009 through 2011 with a focus on improving the company’s mobile broadband coverage and overall performance of its networks.

During 2011, AT&T made nearly 1,900 wireless network upgrades in four key categories in Michigan. These enhancements include:

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* Activating more than 30 new cell sites or towers to improve network coverage.
* Deploying faster fiber-optic connections to nearly 700 cell sites. Combined with HSPA+ technology, these deployments enable 4G speeds.
* Adding capacity or an extra layer of frequency to cell sites — like adding lanes to a highway — with the addition of nearly 775 of these layers, or “carriers.”
* Upgrading more than 400 cell sites to provide fast mobile broadband speeds.

“Our goal is to deliver a network experience that mobilizes everything for customers,” said Brian Ducharme, vice president and general manager for AT&T in Michigan and Indiana. “The ongoing investment we’re making in Michigan is designed to increase coverage and reliability, and to provide advanced services to our customers.

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Last year, AT&T completed 150,000 network enhancements across the country, more than triple the year before, giving customers more capacity and faster speeds, as well as improving 3G dropped-call performance by 25 percent.

AT&T said it planned to support the build or upgrade of thousands of cell sites nationwide to increase network speed, coverage and reliability for both mobile voice and broadband services. In addition, AT&T plans to install additional radio “carriers” at thousands of cell sites nationally, enabling new layers of spectrum capacity to carry larger volumes of mobile broadband traffic. Additional capacity helps support rising mobile data traffic volumes, which continue to increase at a rapid pace.

AT&T operates the nation’s largest Wi-Fi network with nearly 30,000 hotspots in the U.S. and provides access to nearly 190,000 hotspots globally through roaming agreements. Most AT&T smartphone customers get access to our entire national Wi-Fi network at no additional cost, and Wi-Fi usage doesn’t count against customers’ monthly wireless data plans.

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For more information about AT&T’s coverage in Michigan or anywhere in the United States, consumers can visit the AT&T Coverage Viewer. Using the online tool, AT&T customers can measure coverage quality of coverage from a street address, intersection, ZIP code or even a landmark. The viewer is at