Both AT&T and Sprint have announced network expansions this week.

AT&T said it is investing more than $52 million in Kentucky to expand its wireless coverage in the state. The telco said it will add 40 new cell sites in Kentucky and roll out its higher-speed wireless network by year’s end. AT&T has also expanded its 3G network in Nassau County, N.Y.

In 2008, AT&T said it will expand its wireless 3G network in the U.S. to more than 80 additional cities, bringing its 3G wireless services to nearly 350 leading U.S. markets, including all of the Top 100 cities.

In February, AT&T initially announced the ongoing rollout of its 3G wireless broadband service and said that it would begin to deploy a new variant of its 3G technology that promises to deliver faster data access rates (story here).

Meanwhile, Sprint has upgraded its wireless networks in New Jersey, Massachusetts, Idaho and the Inland Northwest.

In 2007, Sprint added 141 new cell sites in New Jersey. The telco also added 159 new cell sites in Massachusetts, including Boston.

In 2007 and early 2008, Sprint added three new cell sites in Idaho and upgraded 76 existing sites to faster EV-DO Rev. A technology. The telco also added 19 new cell sites in the Inland Northwest region and upgraded 76 existing sites to faster EV-DO Rev A.

More Broadband Direct:

• FCC to consider phasing in DTV transition 

• Analyst downgrades Cablevision due to acquisition strategy 

• Insight bulks up digital tier with more HD, digital music offerings 

• NCTA, cable entities come together on scheduling industry events 

• Brophy, Campbell join ACA’s executive committee 

• AT&T, Sprint upgrade networks in select markets 

• Clearwire ups sub count, operating loss in Q4 

• New Cisco router based on new chip 

• Japan, China, U.S. drive 2007 fiber deployments 

• Number of U.S. mobile subs who recall ads increasing 

• Broadband Briefs for 3/04/08