Sprint today announced four new LTE markets, including Baltimore, Gainesville, Manhattan/Junction City, Kan., and Sedalia, Mo.

The new LTE markets bring the Sprint's total to 19, including the 15 cities that went live on July 15. Sprint said it plans to introduce more markets to the network in 2012, with a goal of completing its LTE buildout by 2013.

As part of its $5 Network Vision initiative, Sprint is also modernizing and expanding its nationwide 3G network. The carrier said today that customers in Baltimore, Boston and Washington, D.C., should be seeing the benefits of its new 3G service, which is expected to deliver an a clearer signal, better in-building coverage and fewer dropped/blocked calls. 

Sprint has been offering mobile broadband service over Clearwire's WiMAX network since 2008, but its 15-market LTE footprint is just a fraction of what competitors AT&T and Verizon Wireless offer. AT&T's LTE service is available in nearly 50 markets, and Verizon recently announced that its LTE network now covers 75 percent of the United States population. T-Mobile has plans to begin rolling out LTE in 2013.

Sprint plans to eventually discontinue the use of Clearwire’s WiMaX service, but will supplement its LTE service with that carrier’s planned TD-LTE network.